WO2025165697A1 - Systems and methods for medium access control tower configuration and use in cell-free networks - Google Patents

Abstract

Apparatuses and methods for the configuration and use of medium access control (MAC) towers in cell-free networks are discussed herein. A cell-free network includes a cluster of base stations that serves a UE. A set of MAC entities used/useable within the cluster can be configured as a MAC tower from the network perspective when the MAC entities collected into the MAC tower use at least a single common base station and are connected with the same set of RLC entity(s) according to a sub-clustering of the cluster. MAC-level operations (e.g., MAC-level scheduling) can then be performed on a MAC tower basis. Embodiments detailing the configuration and use of such MAC towers in cell-free networks, including the selection of anchor base stations for those MAC towers, are discussed. Embodiments for hybrid automatic repeat request (HARQ) operation in cell-free networks using MAC towers are also discussed.

Description

SYSTEMS AND METHODS FOR MEDIUM ACCESS CONTROL TOWER CONFIGURATION AND USE IN CELL-FREE NETWORKS TECHNICAL FIELD [0001] This application relates generally to wireless communication systems, including wireless communications systems operating one or more medium access control (MAC) towers within a cell-free network. BACKGROUND [0002] Wireless mobile communication technology uses various standards and protocols to transmit data between a base station and a wireless communication device. Wireless communication system standards and protocols can include, for example, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) (e.g., 4G), 3GPP New Radio (NR) (e.g., 5G), and Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard for Wireless Local Area Networks (WLAN) (commonly known to industry groups as Wi-Fi^®). [0003] As contemplated by the 3GPP, different wireless communication systems' standards and protocols can use various radio access networks (RANs) for communicating between a base station of the RAN (which may also sometimes be referred to generally as a RAN node, a network node, or simply a node) and a wireless communication device known as a user equipment (UE). 3GPP RANs can include, for example, Global System for Mobile communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE) RAN (GERAN), Universal Terrestrial Radio Access Network (UTRAN), Evolved Universal Terrestrial Radio Access Network (E-UTRAN), and/or Next-Generation Radio Access Network (NG-RAN). [0004] Each RAN may use one or more radio access technologies (RATs) to perform communication between the base station and the UE. For example, the GERAN implements GSM and/or EDGE RAT, the UTRAN implements Universal Mobile Telecommunication System (UMTS) RAT or other 3GPP RAT, the E-UTRAN implements LTE RAT (sometimes simply referred to as LTE), and NG-RAN implements NR RAT (sometimes referred to herein as 5G RAT, 5G NR RAT, or simply NR). In certain deployments, the E-UTRAN may also implement NR RAT. In certain deployments, NG-RAN may also implement LTE RAT. 1 4899-3079-6051\1 P65732WO1 [0005] A base station used by a RAN may correspond to that RAN. One example of an E-UTRAN base station is an Evolved Universal Terrestrial Radio Access Network (E- UTRAN) Node B (also commonly denoted as evolved Node B, enhanced Node B, eNodeB, or eNB). One example of an NG-RAN base station is a next generation Node B (also sometimes referred to as a g Node B or gNB). [0006] A RAN provides its communication services with external entities through its connection to a core network (CN). For example, E-UTRAN may utilize an Evolved Packet Core (EPC) while NG-RAN may utilize a 5G Core Network (5GC). BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS [0007] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced. [0008] FIG. 1 illustrates a diagram for an example of clustering in a cell-free network architecture, according to embodiments discussed herein. [0009] FIG. 2 is a diagram illustrating an example radio protocol architecture used in cell-free networks according to certain embodiments. [0010] FIG. 3 illustrates a multi-base station MAC entity, according to embodiments discussed herein. [0011] FIG. 4 illustrates a diagram showing a cluster of base stations, MAC entity options for that cluster, and a corresponding example of MAC entity establishment within a given sub-clustering arrangement that is in use within that cluster. [0012] FIG. 5 illustrates a diagram showing a portion of a protocol stack and its visualized application within a cluster, corresponding to a case of MAC configuration as discussed herein. [0013] FIG. 6 illustrates diagram of a network-level view of a RAN topology that shows the relation of various MAC entities used by a wireless communication system to various base stations within the RAN topology. [0014] FIG. 7 illustrates a diagram of a MAC scheduler of a cluster. [0015] FIG. 8 illustrates an example network topology for which one or more resource allocation chains may be established. 2 4899-3079-6051\1 P65732WO1 [0016] FIG. 9 illustrates a diagram for an example operation of a responsible base station in a MAC entity, according to embodiments discussed herein. [0017] FIG. 10A illustrates a diagram illustrating the input of previous resource allocation decisions for one or more MAC entities to a base station b from a set of Prec(b) base stations and a subsequent output of resource allocation decisions for one or more MAC entities from the base station b to a set of Succ(b) base stations. [0018] FIG. 10B illustrates a flow diagram showing details of the communications between the base station b, the set of Prec(b) base stations, and the set of Succ(b) base stations corresponding to FIG. 10A. [0019] FIG. 11 illustrates a diagram showing an RLC entity that uses each of a first base station, a second base station, and a third base station in a corresponding sub-cluster and that is connected to each of a first MAC entity and a second MAC entity. [0020] FIG. 12A illustrates a first example of using a MAC entity for a HARQ retransmission for low latency traffic that is different than an initial MAC entity used for an initial transmission, according to embodiments herein. [0021] FIG. 12B illustrates a second first example of using a MAC entity for a HARQ retransmission for low latency traffic that is different than an initial MAC entity used for an initial transmission, according to embodiments herein. [0022] FIG. 13 illustrates a diagram of an example MAC tower, according to embodiments herein. [0023] FIG. 14A illustrates a collection of established MAC entities for a cluster of base stations and example MAC towers that may be arranged from that collection of MAC entities, according to embodiments herein. [0024] FIG. 14B illustrates a collection of established MAC entities for a cluster of base stations and a corresponding network protocol diagram between the cluster and a UE, according to embodiments herein. [0025] FIG. 15 illustrates a diagram showing a visualization of various MAC tower configuration options that are applicable when configuring a MAC tower for use within a cluster, according to embodiments herein. [0026] FIG. 16 illustrates a network topology that includes a first base station, a second base station, a third base station, a fourth base station, and a fifth base station and that 3 4899-3079-6051\1 P65732WO1 shows a first MAC entity, a second MAC entity, and a third MAC entity for that network topology. [0027] FIG. 17A illustrates a first case of an initial transmission and a HARQ-based retransmission through a MAC tower that uses each of a first MAC entity and a second MAC entity, according to embodiments herein. [0028] FIG. 17B illustrates a second case of an initial transmission and a HARQ-based retransmission through a MAC tower that uses each of a first MAC entity a second MAC entity, according to embodiments herein. [0029] FIG. 18 illustrates a diagram for an example L2 architecture of a cluster of base stations, according to embodiments herein. [0030] FIG. 19A illustrates a diagram for an example cluster partitioning of a cluster serving a UE, according to embodiments herein. [0031] FIG. 19B illustrates a diagram for an L2 architecture for the cluster of base stations of FIG. 19A. [0032] FIG. 20 illustrates a method of a CCF of a wireless communication system for operating a cluster of base stations serving a UE, according to embodiments discussed herein. [0033] FIG. 21 illustrates a method of a first anchor base station of a first MAC tower that operates in a cluster of base stations serving a UE, according to embodiments discussed herein. [0034] FIG. 22 illustrates a method of a first anchor base station of a MAC tower operating within a cluster of base stations serving a UE, according to embodiments discussed herein. [0035] FIG. 23 illustrates a method of a UE that is served by a cluster of base stations of a wireless communication system, according to embodiments discussed herein. [0036] FIG. 24 illustrates a method of a UE that is served by a cluster of base stations of a wireless communication system, according to embodiments discussed herein. [0037] FIG. 25 illustrates an example architecture of a wireless communication system, according to embodiments disclosed herein. [0038] FIG. 26 illustrates a system for performing signaling between a wireless device and a network device as supported by a CN device, according to embodiments disclosed herein. 4 4899-3079-6051\1 P65732WO1 DETAILED DESCRIPTION [0039] Various embodiments are described with regard to a UE. However, reference to a UE is merely provided for illustrative purposes. The example embodiments may be utilized with any electronic component that may establish a connection to a network and is configured with the hardware, software, and/or firmware to exchange information and data with the network. Therefore, the UE as described herein is used to represent any appropriate electronic component. Clustering in Cell-Free Networks [0040] In some wireless communication systems, a cell-free network architecture provides an adaptive/dynamic and UE-centric distribution of functionalities that may be associated with a “serving cell” as understood in the context of prior cell-based network architectures (e.g., such as an NR network architecture or an LTE network architecture). With respect to the present disclosure, it may be understood generally that a “cluster” or “serving cluster” of a UE is a set of physically and/or logically connected base stations over which functionalities related to the serving the UE (e.g., traditional serving cell functionalities used in cell-based network architectures) may be distributed. Accordingly, (the concept of) a cluster may, under some perspectives, “replace” (the concept of) a serving cell of a UE as understood for prior cell-based networks. [0041] A cluster may have a one-to-one mapping with a UE. Thus, separate (logical) clusters for each of two UEs may be understood/cognizable (even when each of the two corresponding clusters is made up of the same physical set of base stations). Further, note that a single base station may simultaneously belong to multiple clusters that each serve different UEs. [0042] FIG. 1 illustrates a diagram for an example of clustering in a cell-free network architecture. A first cluster 102 of base stations serves a first UE 104 and a second cluster 106 of base stations serves the second UE 108. As illustrated, the first cluster 102 includes the first base stations 110 and the second base stations 112, while the second cluster 106 includes the second base stations 112 and the third base station 114. [0043] Base stations in a same cluster are not necessarily required to jointly transmit/receive to/from the UE being served. Further, control plane and/or user plane functionalities may be dynamically distributed among the base stations in the cluster. 5 4899-3079-6051\1 P65732WO1 [0044] A clustering control function (CCF) may be defined as one or more logical function sets for the establishment and control of clusters in the wireless communication system. The CCF may be a distributed entity of the wireless communication system. For example, the CCF may be distributed across one or more of the core network, a RAN intelligent controller (RIC), and/or one or more base station(s) of the RAN. [0045] The CCF may dynamically develop, update, control, and schedule UE-centric connected sets of clusters in certain geographical areas based on, for example: traffic, latency, reliability, coverage, interference, sensing, mobility, cell load, radio resource management (RRM) aspects, radio link quality, backhaul ideality, location, quality of service (QoS) requirements, and/or measurement reports, etc. [0046] In some wireless communication systems, clustering in cell-free networks includes concepts such as a UE-centric cluster, a CCF, connected base stations (cBSs) (e.g., base stations that are part of a cluster serving a UE), neighboring un-connected base stations (uBSs) (e.g., neighboring base stations to a UE that are not currently part of a cluster serving the UE), etc. In some such systems, a CCF includes functionalities, protocols, message exchange capabilities, and the like that may be used for cluster establishment and/or update tasks (among other things). UEs and base stations may include corresponding functionalities, protocols, message exchange capabilities, and the like supporting the use of clustering as described herein. [0047] In wireless communication systems implementing cell-free networks, it may be that cell-free radio resource control (RRC) connection establishment and maintenance messaging protocols are used. This may mean, among other things, that an RRC state of a UE is understood with respect to the network generally (rather than with respect to a particular serving cell). [0048] Further, such wireless communication systems for cell-free networks may use one or more cluster establishment options corresponding to an initial access of the UE and/or to cluster updating mechanisms (e.g., that control the composition of base stations in the cluster after the UE's initial access). These may include, for example, “greedy”, downlink (DL)-based, uplink (UL)-based, and/or real-time methodologies (and any corresponding message exchanges). Radio Protocols in Cell-Free Networks 6 4899-3079-6051\1 P65732WO1 [0049] In some wireless communication systems, “cluster partitioning” represents a radio-bearer-specific dynamic partition of a cluster serving a UE into logical sub- clusters. Such a cluster partitioning into sub-clusters may be determinative of a protocol stack architecture that applies with respect to that cluster. For example, sub-clusters according to the partitioning may be in one-to-one correspondence with radio link control (RLC) entities. Base stations in a same sub-cluster may then, for example, each carry a copy of the same logical RLC entity for a given radio bearer. [0050] FIG. 2 illustrates a diagram showing aspects of radio protocol use in cell-free network mechanisms. A UE 202 is served by a cluster 204. Within the cluster 204, there is a first sub-cluster 206 that corresponds to a first RLC entity 210 used between the UE 202 and the cluster 204 and a second sub-cluster 208 that corresponds to a second RLC entity 212 between the UE 202 and the cluster 204. The first RLC entity 210 and the second RLC entity 212 are RLC entities used by a packet data convergence protocol (PDCP) entity 218 that corresponds to a radio bearer between the UE 202 and the cluster 204 and that uses the illustrated cluster partitioning. [0051] As illustrated, the first RLC entity 210 is synchronized 214 across the base stations of the first sub-cluster 206 (BS1, BS2, and BS3). This means that, for example, each of these base stations has and operates according to a copy of the first RLC entity 210, as shown. Further, the second RLC entity 212 is synchronized 216 across the base stations of the second sub-cluster 208 (BS4, BS5, and BS6). This means that, for example, each of these base stations has and operates according to a copy of the second RLC entity 212, as shown. Note that, as illustrated, the arrangement of particular base stations of the cluster into the first sub-cluster 206 or second sub-cluster 208 may be transparent to the UE (the UE knows about/operates in terms of the first RLC entity 210 and the second RLC entity 212 (in terms of the sub-clusters), without consideration with respect to particular base stations underlying those RLC entities/sub-clusters). [0052] In the illustrated case, a first packet 220 of the radio bearer corresponding to the PDCP entity 218 is handled at the first RLC entity 210. This ultimately means that the first packet 220 is communicated between the UE 202 and the cluster 204 via one or more of the base stations of the first sub-cluster 206. Further, a second packet 222 of the (same) radio bearer corresponding to the PDCP entity 218 is handled at the second RLC entity 212. This ultimately means that the second packet 222 is communicated between 7 4899-3079-6051\1 P65732WO1 the UE 202 and the cluster 204 via one or more of the base stations of the second sub- cluster 208. [0053] It is contemplated that a cluster partitioning may be updated over time. Establishment and/or updating of a cluster partitioning may take into account QoS requirements and traffic properties associated with a radio bearer. For example, latency constraints, and/or traffic periodicity may be considered. These mechanisms allow the network (e.g., a CCF) to optimally configure sub-cluster-enabled multi-connectivity of a UE to a cluster in, for example, a non-ideal backhaul scenario (where different partitionings of a same cluster may have appreciably different QoS/traffic management characteristics). [0054] In some wireless communication systems, radio protocols in cell-free networks utilize concepts such as cluster partitioning/sub-clusters, RLC synchronization, etc. A functionality for control over dynamically updating cluster partitions, and a corresponding protocol for the update procedure, may be used. PDCP data routing options and a corresponding configuration may be used. Finally, a cell-free radio bearer configuration and/or a message exchange procedure for radio bearer establishment may be used. Embodiments for MAC Entities in Cell-Free Networks [0055] FIG. 3 illustrates a diagram 300 for a multi-base station MAC entity 302, according to embodiments discussed herein. In some wireless communication systems, a MAC entity that is associated with one or more base stations can be established for use by a UE. In various instances, such a MAC entity may be a multi-base station MAC entity that is associated with multiple base stations. For example, FIG. 3 illustrates a multi-base station MAC entity 302 M1 that includes a base station b0304, a base station b1306, a base station b2308, a base station b3310, and a base station b4312 that is established for use by a UE 314. In some instances, a UE might use more than one MAC entity (of which one or multiple may be multi-base station MAC entity(s)). [0056] In some wireless communication systems, a multi-base station MAC entity allocates radio resources jointly across the base stations of the MAC entity. In downlink cases, such radio resource allocation options include: • Joint digital multiple input multiple output (MIMO) precoding (joint coherent beamforming) using the same data at the base stations; 8 4899-3079-6051\1 P65732WO1 • Joint digital MIMO precoding for different data at the base stations, using different MIMO streams; • Coordinated beamforming (interference avoiding); and/or • Coordinated power control (soft frequency reuse). [0057] In uplink cases, such radio resource allocation options include: • Joint digital MIMO equalization; • Joint constellation detection; • Joint forward error correction (FEC) decoding; • Coordinated frequency reuse (e.g., interference avoiding); and/or • Independent reception and processing by multiple base stations. [0058] Note that in the case that a given base station is a member of more than one MAC entity, portions of the radio resources of the base station may be divided/allocated among the MAC entities, with each portion controlled by (e.g., used for data mapping by) its respective one of these MAC entities. [0059] FIG. 4 illustrates a diagram 400 showing a cluster 402 of base stations, MAC entity options 404 for that cluster 402, and a corresponding example of MAC entity establishment within a given sub-clustering arrangement that is in use within that cluster 402. [0060] As illustrated, the cluster 402 serves a UE 406 using the first base station 408 (BS1), the second base station 410 (BS2) and the third base station 412 (BS3). The cluster 402 and the UE 406 communicate according to a first radio bearer associated with the first PDCP entity 414 and a second radio bearer associated with a second PDCP entity 416. [0061] The first radio bearer of the first PDCP entity 414 uses a first sub-clustering of the cluster 402, according to which there is a (single) first sub-cluster 418 associated with a first RLC entity 420. As illustrated, each of the first base station 408, the second base station 410, and the third base station 412 is in the first sub-cluster 418 and thereby associated with the first RLC entity 420. [0062] The second radio bearer of the second PDCP entity 416 uses a second sub- clustering of the cluster 402 that is different than the sub-cluster used by the first radio bearer of the first PDCP entity 414, according to which there are both a second sub- cluster 424 associated with a second RLC entity 426 and a third sub-cluster 428 9 4899-3079-6051\1 P65732WO1 associated with a third RLC entity 430. As illustrated, the first base station 408 and the second base station 410 are in the second sub-cluster 424 and thereby associated with the second RLC entity 426, while the third base station 412 is in the third sub-cluster 428 and thereby associated with the third RLC entity 430. [0063] With respect to designs for MAC entities, it may be that each MAC entity created with respect to/for a UE is associated with a unique set of base stations of the cluster serving that UE. With respect to the cluster 402 used by the UE 406, the following MAC entity options 404 exist. A first MAC entity option is for a first MAC entity 422 that uses the first base station 408. A second MAC entity option is for a second MAC entity 432 that uses the second base station 410. A third MAC entity option is for a third MAC entity 434 that uses the third base station 412. A fourth MAC entity option is for a fourth MAC entity 436 that uses the first base station 408 and the second base station 410. A fifth MAC entity option is for a fifth MAC entity 438 that uses the first base station 408 and the third base station 412. A sixth MAC entity option is for a sixth MAC entity 440 that uses the second base station 410 and the third base station 412. A seventh MAC entity option is for a seventh MAC entity 442 that uses the first base station 408, the second base station 410, and the third base station 412. [0064] It may be that a MAC entity can be connected to (can be activated for use by) an RLC entity if the delays provided by a Xn latency of inter-base station communication within the MAC entity and by MAC scheduling coordination are acceptable for that RLC entity. It may be that such a connection between an RLC entity and a MAC entity can be activated and/or deactivated (such that the MAC entity begins actively serving/stops actively serving the RLC entity) at a near-real time timescale. MAC entity activation/deactivation decisions may be based on, for example, a UE’s capabilities to handle multiple transport blocks (TBs) simultaneously. [0065] Note that a timescale of decision making for MAC entity creation is generally longer than the timescale for RLC entity to MAC entity connection activation/deactivation. For example, MAC entity creation is typically a non-real time process, where the set of created MAC entities may be updated on the order of, e.g., seconds. On the other hand, the activation of a MAC entity to RLC entity connection may be a near-real time process (a faster process) that may occur on the order of dozens or hundreds of milliseconds. 10 4899-3079-6051\1 P65732WO1 [0066] FIG. 4 illustrates a case where each of the third MAC entity 434, the fourth MAC entity 436, and the seventh MAC entity 442 has been activated for the first RLC entity 420. Note that this arrangement is structurally compatible with the example, as each base station found in each of these MAC entities is located in the first sub-cluster 418 for the first RLC entity 420. Note that the activation of the fourth MAC entity 436 and the third MAC entity 434 for the first RLC entity 420 for the first sub-cluster 418 indicates the principle that a MAC entity using fewer than all of the base stations in a cluster may be activated for an RLC entity for that cluster. [0067] Further, as also shown, the fourth MAC entity 436 has been activated for the second RLC entity 426. Note that this arrangement is structurally compatible with the example, as the first base station 408 and the second base station 410 that are represented in the fourth MAC entity 436 are located in the second sub-cluster 424 for the second RLC entity 426. [0068] Further, as also shown, the third MAC entity 434 has been activated for the third RLC entity 430. Note that this arrangement is structurally compatible with the example, as third base station 412 that is represented in the third MAC entity 434 is located in the third sub-cluster 428 for third RLC entity 430. [0069] FIG. 5 illustrates a diagram 500 showing a portion of a protocol stack 502 and its visualized application within a cluster 504, corresponding to a case of MAC configuration as discussed herein. As illustrated, the cluster 504 uses the first base station 506 (BS1), the second base station 508 (BS2), and the third base station 510 (BS3) to serve the UE 512. [0070] The diagram 500 illustrates a PDCP entity 514 corresponding to a radio bearer that is served by a first RLC entity 516 representing a first sub-cluster that includes the first base station 506 (BS1) and the second base station 508 (BS2) and a second RLC entity 518 representing a second sub-cluster that includes the third base station 510 (BS3), in the manner discussed herein. [0071] The diagram 500 further illustrates that first RLC entity 516 is itself served by a first MAC entity 520 that can perform MAC scheduling using the first base station 506 and the second base station 508 and that the second RLC entity 518 is served by a second MAC entity 522 that can perform MAC scheduling using the third base station 510. 11 4899-3079-6051\1 P65732WO1 [0072] By way of example, in FIG. 5 it is the case that the first MAC entity 520 is co- extensive with the first RLC entity 516 with respect to included base stations and that the second MAC entity 522 is co-extensive with the second RLC entity 518 with respect to included base stations. This is given by way of example and not by way of limitation. For example, while in this case the first MAC entity 520 covers all base stations of the sub-cluster of the first RLC entity 516, this should be understood by way of example only (it is possible that a MAC entity includes fewer than all base stations of an RLC entity/sub-cluster that it serves). [0073] In some wireless communication systems, resource allocation decisions for a MAC entity having multiple base stations (e.g., the first MAC entity 520, as illustrated) are made jointly by the base stations within that MAC entity. As an example, a resource allocation decision for the first MAC entity 520 may be made by the first base station 506 and provided to the second base station 508 via an Xn interface. Due to Xn latency, the resource allocation decision may be made for a transmission time interval (TTI) in the future (by at least an applicable Xn latency time). This is understood to add Xn latency to the overall scheduling latency for the first MAC entity 520. Joint resource allocation as so used accordingly may be understood to provide high spectral efficiency but to introduce/add latency. This joint scheduling accordingly may be a rational choice in the context of allocations for latency-tolerant traffic. [0074] In some wireless communication systems, resource allocation decisions across multiple MAC entities used by a UE (e.g., across the first MAC entity 520 and the second MAC entity 522 used by the UE 512) may be made in a decentralized manner by base stations of the different MAC entities used by the UE. First, those base stations may agree about a coordinated allocation pattern (in time, frequency and/or spatial domains) that applies over a period of time. As an example, the base stations can agree to allow the first MAC entity 520 be scheduled at even TTIs and to further allow the second MAC entity 522 be scheduled at odd TTIs. Other possible examples can include having the base stations agree on a coordination in a frequency band and/or in a spatial domain (for multi-antenna UEs). In real-time, each base station may decide to schedule a MAC entity in compliance with the coordinated allocation pattern. Decentralized scheduling as so used accordingly may be understood not add latency, but might achieve less spectral efficiency as compared with a joint decision option across MAC entities. 12 4899-3079-6051\1 P65732WO1 [0075] FIG. 6 illustrates diagram 600 of a network-level view of a RAN topology 602 that shows the relation of various MAC entities used by a wireless communication system to various base stations within the RAN topology 602. As illustrated, the various MAC entities use various ones of the base stations. For example, as can be seen (and as represented in the first listing 604), the MAC entity M1606 includes the base station b0 620, the base station b₂624, and the base station b₃626; the MAC entity M₂608 includes the base station b3626 and the base station b4628; the MAC entity M3610 includes the base station b₀620, the base station b₄628, and the base station b₅630; the MAC entity M4612 includes the base station b0620 and the base station b6632; the MAC entity M5 614 includes the base station b₆632 and the base station b₇634; the MAC entity M₆616 includes the base station b0620; and the MAC entity M7618 includes the base station b0 620, the base station b₁622, the base station b₂624, the base station b₃626, the base station b4628, the base station b5630, the base station b6632, and the base station b7 634. Note that according to this arrangement there are multiple multi-base station MAC entities and one single-base station MAC entity. [0076] A MAC scheduler may be provided as a module in/for the RAN topology 602. The MAC scheduler may be responsible for radio resource allocation and selection of transmission parameters (e.g., modulation and coding scheme (MCS), rank, precoding option, etc.) for such transmissions. Further, a MAC scheduler in cell-free network may be a network-level algorithm that works across one or more base stations of the RAN topology 602. [0077] Mechanisms for and entities used when coordinating radio resource allocation between, for example, multiple multi-base station MAC entities operating within a cell- free network that exhibit non-trivial overlapping characteristics (e.g., as in the example of the various MAC entities found within the RAN topology 602 of FIG. 6) are now discussed. Such mechanisms may be scalable, such that they work any size of the network; may minimize introduced coordination delays; may ensure that coordination delays for single-base station MAC entities are negligible; and/or may maximize communication efficiency (e.g., spectral efficiency) while preserving fairness. [0078] FIG. 7 illustrates a diagram 700 of a MAC scheduler 702 of a cluster. The MAC scheduler 702 may schedule a given MAC entity according to various inputs, including buffer status/service histories 704 for the UE(s) using the given MAC entity, the physical layer (PHY) measurements/link quality estimations 706 for the UE(s) using the given 13 4899-3079-6051\1 P65732WO1 MAC entity, and/or link adaptation/QoS parameters 708 for the UE(s) using the given MAC entity. The outputs of the MAC scheduler 702 may include resource allocation(s) 710 for the UE(s) (e.g., time and frequency domain resource allocation(s)) and/or transmission parameter(s) 712 (e.g., modulation and coding scheme (MCS), rank, precoding, etc.). [0079] FIG. 8 illustrates an example network topology 800 for which one or more resource allocation chains may be established. In some embodiments, B may be provided as a set of base stations in the system. As illustrated in FIG. 8, the set of base stations B within the network topology 800 includes the base station b0802, the base station b1804, and the base station b2806. [0080] In some embodiments, for each base station b, a resource allocation chain of the radio resources of b is defined as a finite sequence of base stations: Ch(b) ≔ (Ch0(b), Ch1(b), …, Chn(b)(b)), where: • Ch_k(b) ∈ B is k-th element of the base station b-th chain; • n(b) ∈ ℕ is the number of elements minus one in base station b-th chain; • Ch₀(b) = b; which denotes that the chain starts with the base station for which it is constructed, and • Chi(b) ≠ Chj(b), ∀ i ≠ j, which denotes that base stations within a single chain are all different.^{[0081] A resource allocation chain can be constructed for each base station, thus Chk(b)}_{∈ B can be defined for each k = 1, …, n(b). A purpose of the resource allocation chain} construction is to define which base stations (and in which order) will allocate the radio resources of the base station b. In this mechanism, base station Chn(b)(b) starts the resource allocation of base station b, allocates some resources, then passes the result to base station Chn(b)−1(b). Accordingly, it is understood that a base station Chk(b) that is not Ch_n(b)(b) may receive a partial allocation result for base station b from base station Chk+1(b). This base station Chk(b) then proceeds to allocate some of the remaining available resources without touching any already made resource allocation(s). [0082] With respect to the reference to the network topology 800 presented in FIG. 8, where B = {b0 , b1, b2}, one example set of such resource allocation chains (among various possibilities) is: • Ch(b0) = (b0, b1, b2), where n(b0) = 2; 14 4899-3079-6051\1 P65732WO1 • Ch(b1) = (b1), where n(b1) = 0; and • Ch(b2) = (b2, b0), where n(b2) = 1. [0083] Note that herein, when providing discussion related a resource allocation chain Ch(b), the base station b may be referred to as “the base station that is described by the resource allocation chain Ch(b).” [0084] In some embodiments, ℳ may be provided as a set of MAC entities in a system._{Then, for each MAC entity ^^ ∈ ℳ, where M is associated to a subset ^^ ⊆ ^^ of base} stations, a responsible base station may be defined. This responsible base station,_{denoted as ^^^^^^(^^) ∈ ^^, is responsible for the radio resource allocation for MAC entity} M. The radio resources in question are radio resources across all base stations in the MAC entity M. To simplify the implementation, a responsible base station of a MAC is_{to be understood to be associated with that MAC entity (i.e., ^^^^^^(^^) ∈ ^^ ⊆ ^^).} [0085] FIG. 9 illustrates a diagram 902 for an example operation of a responsible base station in a MAC entity, according to embodiments discussed herein. The diagram 902 illustrates a network topology that includes the base station b₀904, the base station b₂ 906, the base station b3908, the base station b4910, the base station b5912, and the base station b₆914. As illustrated, the base station b₀904, the base station b₂906, and the base station b3908 are included in a MAC entity M1916 (while the base station b4910, the base station b₅912, and the base station b₆914 are not included in the MAC entity M1916). [0086] The diagram 902 illustrates the nature of the three resource allocation chains that apply to the three base stations in the MAC entity M₁916 as defined with respect to the base stations illustrated. As illustrated, the first resource allocation chain 918 for the base station b₀904 takes the form of Ch(b₀) = (b₀), the second resource allocation chain 920 for the base station b2906 takes the form of Ch(b2) = (b2, b4, b0, b6), and the third resource allocation chain 922 for the base station b₃908 takes the form of Ch(b₃) = (b₃, b5, b0). [0087] As illustrated, the base station b0904 acts as the responsible base station for the MAC entity M₁916. Accordingly, the base station b₀904 is responsible for/performs radio resource allocation for MAC entity M1916. Allocation decisions taken by the base station b₀904 for the MAC entity M₁916 and that involve the base station b₂906 are propagated to the base station b2906 along the second resource allocation chain 920 for the base station b₂906. Allocation decisions taken by the base station b₀904 for the 15 4899-3079-6051\1 P65732WO1 MAC entity M1916 and that involve the base station b3908 are propagated to the base station b₃908 along the third resource allocation chain 922 for the base station b₃908. [0088] Mechanisms for the input and output of resource allocation decisions at a base station are now discussed. In particular, input and/or output message exchange flows for resource allocation decisions for a base station b are discussed. Base station b may_{participate in a number of resource allocation chains ( ^^ℎ^^^^^^^^^^^^(^^): = {(^^ᇱ, ^^): ^^ =^^ℎ^(^^ᇱ)}). Further, base station b may be the responsible base station for performingresource allocation for one or more MAC entities (^^^^^^^^^^^^(^^): = {^^: ^^ = ^^^^^^(^^)}).[0089] For each (^^ᇱ, ^^) ∈ ^^ℎ^^^^^^^^^^^^(^^), base station b keeps an up-to-date version of} resource allocation for ^^^ᇱ. This resource allocation is updated based on the input from predecessor base stations ^^ℎ_^ା^(^^^ᇱ)and based on base station b’s allocation decisions. [0090] Each TTI, after any input messages are received obtained and processed, for_{each ^^ ∈ ^^^^^^^^^^^^(^^), the resource allocation procedure is run for a particular TTI in the} future. The time for computation of the resource allocation is δ. [0091] Each TTI, after the resource allocation procedures that started δ TTIs ago are_{finished for all ^^ ∈ ^^^^^^^^^^^^(^^), for each (^^ᇱ,^^) ∈ ^^ℎ^^^^^^^^^^^^(^^), the current resource} allocation result of ^^^ᇱ resources for all future TTIs (for which the allocation result is available at the base station b) is sent to the successor base stations in the resource allocation chains: ^^ℎ_^ି^(^^^ᇱ). [0092] Further, if the base station b has an allocation decision for its own resources for any TTI T, it implements the decision at this TTI. [0093] According to this mechanism, it may accordingly be understood that a set of one or more predecessor base stations providing input messages to the base station b is_{represented as ^^^^^^^^(^^): = {^^ᇱᇱ:∃(^^ᇱ,^^): ^^ = ^^ℎ ᇱ ᇱᇱ ᇱ ^(^^ ), ^^ = ^^ℎ^ା^(^^ )}. Further, a set of} one or more successor base stations to which the base station b provides output messages_{is represented as ^^^^^^^^(^^): = {^^ᇱᇱ:∃(^^ᇱ, ^^): ^^ = ^^ℎ ᇱ ᇱᇱ ᇱ ^(^^ ), ^^ = ^^ℎ^ି^(^^ )}.} [0094] FIG. 10A illustrates a diagram 1002 illustrating the input of previous resource allocation decisions for one or more MAC entities to a base station b 1006 from a set of Prec(b) base stations 1008 and a subsequent output of resource allocation decisions for one or more MAC entities from the base station b 1006 to a set of Succ(b) base stations 1010. 16 4899-3079-6051\1 P65732WO1 [0095] FIG. 10B illustrates a flow diagram 1004 showing details of the communications between the base station b 1006, the set of Prec(b) base stations 1008, and the set of Succ(b) base stations 1010 corresponding to FIG. 10A. [0096] As illustrated in FIG. 10B, the set of Prec(b) base stations 1008 sends 1012 the base station b 1006 information of any prior resource allocation decisions for one or more MAC entities. This information may include resource allocation decisions that were taken at any one or more of the set of Prec(b) base stations 1008. This resource allocation information may further include resource allocation decisions that were received at the set of Prec(b) base stations 1008 from still further preceding base stations (e.g., as illustrated in FIG. 10A). [0097] The base station b 1006 then processes 1014 the received resource allocation decision information. Taking into account the received resource allocation decision information, the base station b 1006 then runs 1016 scheduling to update/create resource allocation decisions. For example, a resource allocation decision for each MAC entity for which the base station b 1006 is responsible is made by the base station b 1006 and is added to the set of resource allocation information as previously received from the set of Prec(b) base stations 1008. [0098] The base station b 1006 then sends 1018 resource allocation information (e.g., as updated/created at the base station b 1006) to the set of Succ(b) base stations 1010. [0099] Further, if the base station b 1006 has an allocation decision for its own resources for any TTI T, it executes 1020 this decision at this TTI. [0100] Note that while in the particular embodiment illustrated in FIG. 10A each of the set of Prec(b) base stations 1008 and the set of Succ(b) base stations 1010 has been illustrated to include multiple base stations, in alternative cases, either/both of these could include only a single base station. Observations Corresponding to MAC Entity Use [0101] FIG. 11 illustrates a diagram 1100 showing an RLC entity 1106 that uses each of a first base station 1108, a second base station 1110, and a third base station 1112 in a corresponding sub-cluster and that is connected to each of a first MAC entity 1102 and a second MAC entity 1104. [0102] As illustrated, the first MAC entity 1102 is a single base station MAC entity using the first base station 1108. Due to the fact that the first MAC entity 1102 includes 17 4899-3079-6051\1 P65732WO1 only one base station, it exhibits no delay due to inter-base station coordination. Further, a spectral efficiency of the first MAC entity 1102 is limited to that achievable by the first base station 1108 operating alone/independently. [0103] Further, the second MAC entity 1104 is a multiple-base station MAC entity that uses the first base station 1108, the second base station 1110, and the third base station 1112. Because the second MAC entity 1104 uses multiple base stations, it exhibits some amount of delay due to inter-base station coordination. Further, the spectral efficiency of the second MAC entity 1104 is higher than that achievable by the first MAC entity 1102 due to, for example, the ability to use joint MIMO transmission and/or reception across each of first base station 1108, the second base station 1110, and the third base station 1112. [0104] Considerations corresponding to the use of differently-sized RLC buffers are now discussed. Suppose that T_M is a delivery time of RLC buffer content using MAC entity M. A linear model for TM as a function of the size of the RLC buffer SizeBuffer may be expressed as ^_{^ (^^^^^^^^ ) ^ ெ ^௨^^^^ = ^^ெ + ^^^^^^^^^௨^^^^ · ோ^௧^ಾ(ௌ^^^ா^^ಾ), where:} Rate_M is a data rate for the MAC entity M; and SpecEff_M is a spectral efficiency of the MAC entity M. [0105] Assume that a first MAC entity (MAC 1) has delay of D₁ and a data rate of R₁ and that a second MAC entity (MAC 2) has a delay D2 and a data rate R2. In such a case, if D₁ < D₂ then MAC 1 has smaller delay, and if R₁ < R₂ then MAC 1 has a smaller data rate and/or spectral efficiency. Further, if SizeBuffer is smaller than^{^మି^భ} ோ_మିோభ ^^_^^^_ଶ, then MAC 1 delivers the RLC buffer content faster than MAC 2. Otherwise, if is larger than that value, then MAC 2 delivers faster than MAC 1. [0106] It is observed that a flexible choice between MAC 1 and MAC 2 may be possible if tight coordination between MAC 1 and MAC 2 can be achieved/maintained. The ability/feasibility of achieving/maintaining such a level of coordination depends (at least in part) on where these MAC entities reside/are organized within the wireless communication system (e.g., relative to each other). However, it has been found that the 18 4899-3079-6051\1 P65732WO1 residing place/relative organization of MAC entities is not defined in various definitions for various wireless communication systems currently in operation. [0107] It is observed that, if a number of possible retransmissions for data is limited (e.g., due to latency requirements corresponding to that data), it may be beneficial to perform one or more retransmissions for the data on a different MAC entity than an initial MAC entity used for an initial transmission. Note that for such cases, it may be that the MAC entities share a same HARQ procedure. Various examples corresponding to this circumstance are now given. [0108] FIG. 12A illustrates a first example 1202 of using a MAC entity for a HARQ retransmission for low latency traffic that is different than an initial MAC entity used for an initial transmission, according to embodiments herein. [0109] As illustrated, a first MAC entity 1204 (MAC 1) uses a first base station 1208, while a second MAC entity 1206 (MAC 2) uses the first base station 1208, a second base station 1210, and a third base station 1212. As shown, an initial transmission is scheduled via the second MAC entity 1206. This transmission occurs according to a relatively high spectral efficiency due to, for example, joint transmission across each of the first base station 1208, the second base station 1210, and the third base station 1212. [0110] FIG. 12A assumes a case where this initial transmission is not successful. According to a HARQ procedure corresponding to the initial transmission, it is determined that a retransmission of the data is needed. However, performing the retransmission using the second MAC entity 1206 may not fit traffic latency constraints (e.g., due to a coordination delay associated with the joint use of the first base station 1208, the second base station 1210, and the third base station 1212, and/or the joint radio resources for the second MAC entity 1206 that operate across the first base station 1208, the second base station 1210, and the third base station 1212 may be otherwise limited. [0111] However, it may be that, as an alternative, use of the first MAC entity 1204 can fit the applicable traffic latency constraints, in that the first MAC entity 1204 does not incur a coordination delay across base stations and/or that radio resources for the first MAC entity 1204 are otherwise more immediately available. In such a case, it may be beneficial to schedule the retransmission on the first MAC entity 1204 (instead of on the second MAC entity 1206), as illustrated. [0112] FIG. 12B illustrates a second example 1214 of using a MAC entity for a HARQ retransmission for low latency traffic that is different than an initial MAC entity used for 19 4899-3079-6051\1 P65732WO1 an initial transmission, according to embodiments herein. Initially, note that FIG. 12B illustrates the same structural configuration for the first MAC entity 1204 (MAC 1) and the second MAC entity 1206 (MAC 2) in relation to the first base station 1208, the second base station 1210, and the third base station 1212 as was used in FIG. 12A. [0113] In the case shown in FIG. 12B, an initial transmission is scheduled via the first MAC entity 1204. This initial transmission occurs according to a relatively low spectral efficiency due to the use of (only) the first base station 1208 by the first MAC entity 1204 for the transmission. [0114] FIG. 12B assumes a case where this initial transmission is not successful. It may further be the case that, for example, there is only enough remaining time with an applicable delay budget constraint for the data of the transmission for a single try at retransmission (from either the first MAC entity 1204 or the second MAC entity 1206). [0115] As shown, in such a case, it is beneficial to use the second MAC entity 1206 (instead of the first MAC entity 1204) for the retransmission. This is because the higher spectral efficiency of the second MAC entity 1206 due to, for example, its use of joint transmission of the data using each of the first base station 1208, the second base station 1210, and the third base station 1212 is associated with a relatively improved the probability of success for the retransmission over the case of performing the retransmission using the first MAC entity 1204. [0116] In order to implement strategies such as those illustrated in relation to FIG. 12A and FIG. 12B, it may be beneficial to share HARQ processes among/as between MAC entities. Accordingly, mechanisms for formally configuring a set of MAC entities that share HARQ processes (e.g., such that these can be differentiated from MAC entities outside the set that may not share the HARQ processes) are useful within the system. [0117] In sum, it is concluded that providing for additional flexibility in MAC selection, configuration, and use is desirable. In order to provide this flexibility, it may be beneficial to provide mechanisms to configure sets of MAC entities at a network side that jointly agree to scheduling decisions among themselves (such that these can be differentiated from MAC entities outside this set). Note that in various existing wireless communication systems, it is rather assumed that all MAC entities work independently according to, at best, a non-real-time coordination (e.g., via patterns in time). 20 4899-3079-6051\1 P65732WO1 [0118] It may further be beneficial to provide mechanisms to configure for a physical implementation site for a MAC entity within the wireless communication system (e.g., such that the MAC entity is implemented at a particular one or more base station(s)). [0119] It may further be beneficial to provide mechanisms to configure sets of MAC entities that share the same HARQ procedures. Note that mechanisms for configuring for updated corresponding use of the HARQ procedures themselves are also contemplated. [0120] Finally, it is also identified that it is beneficial to define for correspondences between network-side MAC entities (referred to herein at times more simply as “network MAC entities”) that exhibit these properties and UE-side MAC entities (referred to herein at times more simply as “UE MAC entities”) intended for use with such network MAC entities. Embodiments for MAC Tower Configuration and Use [0121] Various extensions for MAC layer design within a cell-free architecture that enable/incorporate the benefits just discussed are disclosed herein. Such extensions incorporate/assume the use of a set of MAC entities referred to herein as a “MAC tower.” MAC tower usage facilitates the definition of, for example, MAC decision coordination as between MAC entities of the MAC tower, permitted physical implementation options for the MAC entities of the MAC tower, and HARQ procedures/sharing rules for MAC entities of the MAC tower. [0122] Corresponding MAC tower configuration protocols are discussed. Mechanisms for formalizing and maintaining a correspondence between network MAC entities and UE MAC entities are also discussed. Mechanisms for HARQ process signaling within a MAC tower, including various requirements for a low density parity check (LDPC) decoder to support partial incremental redundancy, are also discussed. Control mechanisms that provide a way for a UE to have an effect on MAC selection within a MAC tower are also discussed. [0123] Embodiments herein also disclose an updated protocol stack architecture for cell-free systems that use MAC towers. For example, RLC entities having a specified base station are contemplated. Further, mechanisms for MAC entity establishment and configuration when using MAC towers are discussed. [0124] A set of MAC entities can be configured as a MAC tower from the network perspective when: 21 4899-3079-6051\1 P65732WO1 • the MAC entities use at least a single common base station; and • the MAC entities are connected with the same set of RLC entity(s). [0125] FIG. 13 illustrates a diagram 1302 of an example MAC tower 1304, according to embodiments herein. As illustrated, the MAC tower 1304 is made up of a first MAC entity 1306 (MAC 1) for a first base station 1310 and a second MAC entity 1308 (MAC 2) for the first base station 1310, a second base station 1312, and a third base station 1314. [0126] Note that each of the first MAC entity 1306 and the second MAC entity 1308 shares the first base station 1310 as a common base station. Note also that each of the first MAC entity 1306 and the second MAC entity 1308 is connected to a same RLC entity 1318. [0127] Further, corresponding to the configuration and use of various MAC entities within a same MAC tower, the following properties may be assumed: • Each MAC entity in a MAC tower belongs to no other MAC tower; • MAC entities of a same MAC tower are physically implemented at a base station that common to all of the MAC entities; • MAC entities of a same MAC tower are capable of coordinating their grant allocation decisions with each other on a real-time basis; and • MAC entities of a same MAC tower share the same HARQ processes. [0128] Note that in the example illustrated in FIG. 13, the MAC tower 1304 is sited 1316 at the first base station 1310. This means that each MAC entity of the MAC tower 1304 (the first MAC entity 1306 and the second MAC entity 1308) is physically implemented at the first base station 1310. As discussed herein, a base station at which a MAC tower is sited may be referred to as an “anchor base station.” Accordingly, it will be understood that the first base station 1310 is the anchor base station for the MAC tower 1304. [0129] Still further, corresponding to the configuration and use of MAC towers for use at the network side, the following properties may be assumed: • Different MAC towers may provide grants without real-time synchronization with each other; and • MAC towers as configured/defined/used at the network side are in a one-to-one correspondence with a UE MAC entities at the UE. 22 4899-3079-6051\1 P65732WO1 [0130] FIG. 14A illustrates a first collection 1402 of established MAC entities for a cluster 1404 of base stations and example MAC towers that may be arranged from that collection of MAC entities, according to embodiments herein. The cluster of base stations includes the first base station 1406 (BS 1), the second base station 1408 (BS 2), and the third base station 1410 (BS 3), as illustrated. FIG. 14A also illustrates that established MAC entities for the cluster include a first MAC entity 1412 (MAC 1) for the first base station 1406, a second MAC entity 1414 (MAC 2) for the third base station 1410, a third MAC entity 1416 (MAC 3) for the first base station 1406 and the second base station 1408, a fourth MAC entity 1418 (MAC 4) for the second base station 1408 and the third base station 1410, and a fifth MAC entity 1420 (MAC 5) for the first base station 1406, the second base station 1408, and the third base station 1410. [0131] The first collection 1402 of MAC entities can be arranged into a first MAC tower 1422 and a second MAC tower 1426, as illustrated. The first MAC tower 1422 includes the first MAC entity 1412, the third MAC entity 1416, and a first replacement MAC entity 1424 corresponding to the fifth MAC entity 1420 (MAC 5A) (as will be discussed). The first base station 1406 is a common base station of the first MAC tower 1422 where the first MAC tower 1422 is sited (accordingly, the first base station 1406 is the anchor base station for the first MAC tower 1422). [0132] The second MAC tower 1426 includes the second MAC entity 1414, the fourth MAC entity 1418, and a second replacement MAC entity 1428 corresponding to the fifth MAC entity 1420 (MAC 5B) (as will be discussed). The third base station 1410 is a common base station of the second MAC tower 1426 where the second MAC tower 1426 is sited (accordingly, the third base station 1410 is the anchor base station for the second MAC tower 1426). [0133] The use of fifth MAC entity 1420 from the first collection 1402 of MAC entities is replaced with a new independent MAC entity in each of the first MAC tower 1422 and the second MAC tower 1426: the first replacement MAC entity 1424 of the first MAC tower 1422 that is implemented at the first base station 1406 and the second replacement MAC entity 1428 of the second MAC tower 1426 that is implemented at the third base station 1410. The use of such separate, replacement MAC entities allows for the original scope of the fifth MAC entity 1420 in terms of base stations to be active within each of the first MAC tower 1422 and the second MAC tower 1426. This is instead of an alternative case possible under the MAC tower construction bounds of the fifth MAC 23 4899-3079-6051\1 P65732WO1 entity 1420 where the fifth MAC entity 1420 could have been directly used in only one of the first MAC tower 1422 or the second MAC tower 1426. [0134] It is also observed that in the first collection 1402 of MAC entities illustrated in FIG. 14A, it is not possible for the first MAC entity 1412 and the second MAC entity 1414 to belong to a same MAC tower since they do not share any common base station. [0135] FIG. 14B illustrates a second collection 1430 of established MAC entities for the cluster 1404 of base stations (as modified from the first collection 1402 of established MAC entities as discussed in relation to FIG. 14A) and a corresponding network protocol diagram 1432 between the cluster 1404 and a UE 1434, according to embodiments herein. [0136] The second collection 1430 of MAC entities corresponds to the first collection 1402 of MAC entities from FIG. 14A, but with the first replacement MAC entity 1424 and the second replacement MAC entity 1428 in play instead of one single fifth MAC entity 438 (as was discussed in FIG. 14A). Further, each MAC entity in the second collection 1430 is marked corresponding to its assigned one of the first MAC tower 1422 and the second MAC tower 1426 as was described in FIG. 14A. [0137] The network protocol diagram 1432 of FIG. 14B illustrates that a first network RLC entity buffer 1436 of a first network RLC entity uses the first MAC tower 1422 and that a second network RLC entity buffer 1438 of a second network RLC entity uses the second network RLC entity buffer 1438. This corresponds to the use of the first MAC tower 1422 and the second MAC tower 1426 by different network RLC entities. [0138] The network protocol diagram 1432 further illustrates that the first MAC entity 1412, the third MAC entity 1416, and the first replacement MAC entity 1424 of the first MAC tower 1422 are examples of network MAC entities (consistent with the fact that the first MAC tower 1422 is itself an entity of the cluster of base stations). Likewise, the network protocol diagram 1432 illustrates that the second MAC entity 1414, the fourth MAC entity 1418, and the second replacement MAC entity 1428 of the second MAC tower 1426 are also examples of network MAC entities (consistent with the fact that the second MAC tower 1426 is itself an entity of the cluster of base stations). [0139] The network protocol diagram 1432 further illustrates a corresponding arrangement of UE MAC entities that includes the first UE MAC entity 1440 and the second UE MAC entity 1442. As illustrated, the applicable MAC tower constructs (e.g., the first MAC tower 1422 and the second MAC tower 1426) may not be replicated at the 24 4899-3079-6051\1 P65732WO1 UE 1434. Rather, more straightforwardly, a single UE MAC entity is established at the UE 1434 for each active MAC tower at the cluster 1404. Accordingly, FIG. 14B illustrates in the network protocol diagram 1432 that the first UE MAC entity 1440 of the UE 1434 corresponds to the MAC entities of the first MAC tower 1422 in a joint fashion, and similarly that the second UE MAC entity 1442 of the UE 1434 corresponds to the MAC entities of the second replacement MAC entity 1428 in a joint fashion. [0140] Finally, the network protocol diagram 1432 of FIG. 14B also illustrates that a first UE RLC entity buffer 1444 of a first UE RLC entity (that corresponds to the network side RLC entity of the first network RLC entity buffer 1436) uses the first UE MAC entity 1440 and that a second UE RLC entity buffer 1446 of a second UE side RLC entity (that corresponds to the network side RLC entity of the first network RLC entity buffer 1436) uses the second UE MAC entity 1442. [0141] FIG. 15 illustrates a diagram 1500 showing a visualization 1502 of various MAC tower configuration options that are applicable when configuring a MAC tower for use within a cluster 1504, according to embodiments herein. [0142] In some embodiments, a MAC tower can be configured based on various parameters. A first of these parameters is a parameter for a maximum base station set 1506 (a “MacMaxSet” parameter). The maximum base station set 1506 may be understood as some subset (including potentially an improper subset) of the cluster 1504_{(^^^^^^^^^^^^^^^^^^ ⊆ ^^^^^^^^^^^^^^) that is a collection of base stations that can be used by a MAC} tower for resource allocation. [0143] A second parameter for the configuration of a MAC tower is a parameter for a minimum base station set 1508. The minimum base station set 1508 may be understood as some subset (including potentially an improper subset) of the maximum base station_{set 1506 (^^^^^^^^^^^^^^^^^^ ⊆ ^^^^^^^^^^^^^^^^^^ ⊆ ^^^^^^^^^^^^^^) that is a collection of base stations that} are eligible for the physical siting of a MAC tower (the base stations that are common to all MAC entities of the MAC tower). [0144] The maximum base station set 1506 and the minimum base station set 1508 may accordingly be configured as MAC entities within the MAC tower. [0145] As illustrated, there may be, in at least some arrangements, one or more additional base station set(s) 1510 that can exist that include all of the base stations of the minimum base station set 1508 but fewer than all of the maximum base station set 25 4899-3079-6051\1 P65732WO1 1506. These additional base station set(s) 1510 can also be established/used as MAC entity(s) within the MAC tower. [0146] A third parameter for the configuration of a MAC tower is a parameter for a set of data radio bearers (DRBs) which may be understood as the logical channels to serve by/with the MAC tower. [0147] In some embodiments, for network MAC entities of the MAC tower, the network may select a single base station from the minimum base station set 1508 as the location where MAC entities of the MAC tower reside. The network may create one or several MAC entities that control different subsets of base stations from the maximum base station set 1506 (so long as these MAC entities include at least the minimum base station set 1508). [0148] Correspondingly, in some embodiments, a single counterpart UE MAC entity is created at a UE side for the MAC tower. [0149] Note also that in some cases, a maximum number of TBs per transmission time interval (TTI) may be is configured on a per-MAC tower basis. [0150] Impacts of MAC tower configuration and use on MAC-level scheduling grant procedures are now discussed. In some embodiments, it may be that a MAC tower allocates resources and generates grants for a UE via one or more MAC entity(s) of the MAC tower. This may be the case for either or both of DL and/or UL communication. [0151] A decision to allocate resources for a MAC entity is made/agreed at the base station where the MAC tower for that MAC entity resides (the anchor base station for the MAC tower). Note that such a decision to allocate resources for a MAC entity may not require coordination/agreement with MAC entities of other, outside MAC towers. [0152] Note also that for cell-free wireless communication systems that use responsible base stations, MAC entity scheduling as described in may be applied by selecting a responsible base station of a MAC entity to also be the base station where the MAC entity resides (the anchor base station for the MAC tower). [0153] FIG. 16 illustrates a network topology 1600 that includes a base station b₀1602, a base station b11604, a base station b21606, a base station b31608, and a base station b₄1610. Within the network topology 1600, a MAC entity M₀1612 uses the base station b01602, a MAC entity M11614 uses the base station b01602 and the base station b1 26 4899-3079-6051\1 P65732WO1 1604, and a MAC entity M21616 uses each of the base station b01602, the base station b₁1604, the base station b₂1606, the base station b₃1608, and the base station b₄1610. [0154] Embodiments with respect to siting for a MAC tower in systems that use responsible base stations for MAC entities are now discussed in terms of the network topology 1600. As illustrated, the base station b01602 is a member of each of the MAC entity M₀1612, the MAC entity M₁1614, and the MAC entity M₂1616. This is compatible with an arrangement where the base station b01602 acts as a responsible base station for each of the MAC entity M₀1612, the MAC entity M₁1614, and the MAC entity M21616. It may accordingly be that the base station b01602 is used as the site of each of the MAC entity M01612, the MAC entity M11614, and the MAC entity M2 1616. [0155] Such circumstances are compatible with the siting of a MAC tower that includes each of the MAC entity M₀1612, the MAC entity M₁1614, and the MAC entity M₂1616 (such as the MAC tower assumed in this discussion) at the base station b01602. Accordingly, it will be understood the configuration and use of a MAC tower for these MAC entities that uses the base station b01602 as an anchor base station is non- interfering with the configuration and use of the base station b₀1602 as a responsible base station for these MAC entities. [0156] In various embodiments, MAC towers independently allocate resources to and generate grants for their constituent MAC entity(s). A maximum number of grants (e.g., TBs) that can be generated by a MAC tower at a given TTI can be coordinated between MAC towers. These grants may take into account a given UE’s capabilities to receive/transmit multiple TBs per TTI. [0157] Coordination as between MAC entities of different MAC towers may be performed on a non-real-time basis that establishes an agreed set of resource allocation patterns. For example, each pattern may be uniquely assigned to one of the MAC towers and be understood to relate to physical resources controlled by MAC entity(s) of that corresponding MAC Tower. These agreements for patterning use may provide certain restrictions on frequency, time, and/or spatial allocation of resources to the MAC entities to ensure that MAC entities of different MAC Towers operate with orthogonal physical resources. [0158] In some embodiments, MAC entities of a MAC tower may share HARQ processes. In such cases, it may be that an initial transmissions and any following one or 27 4899-3079-6051\1 P65732WO1 more HARQ-based retransmission(s) can be performed through different MAC entities of the MAC tower. In such cases, it may be that HARQ processes enumeration is consecutive through/with respect to all the MAC entities in the MAC tower. Note that the use of HARQ processes corresponding to a MAC tower as described herein may be controlled by the anchor base station of the MAC tower. [0159] In some cases, a retransmission is performed by a MAC entity having lower spectral efficiency than a MAC entity used for the initial transmission. FIG. 17A illustrates a first case of an initial transmission and a HARQ-based retransmission through a MAC tower 1702 that uses each of a first MAC entity 1704 (MAC 1) and a second MAC entity 1706 (MAC 2), according to embodiments herein. As shown, the first MAC entity 1704 uses a first base station 1708, while the second MAC entity 1706 uses each of the first base station 1708, a second base station 1710, and a third base station 1712. [0160] In the case shown in FIG. 17A, an initial transmission occurs using the second MAC entity 1706 of the MAC tower 1702. It is then determined that HARQ-based retransmission is needed (e.g., because no HARQ acknowledgement (ACK) for the initial transmission has been received). The retransmission occurs, as illustrated, using the first MAC entity 1704 of the MAC tower 1702. As the first MAC entity 1704 uses fewer than all of the base station used by the second MAC entity 1706, the retransmission occurs according to a lower spectral efficiency than that of the initial transmission. [0161] Corresponding to such cases of relatively lower spectral efficiency for a retransmission, a partial redundancy version can be allowed/used for the retransmission. In this mode, the redundancy version is not transmitted fully. In such cases, a TB size of the retransmission is smaller than a TB size of the initial transmission. A decoder at a receiver (e.g., a UE) that supports the use of such a partial redundancy version and may be capable of combining the partial retransmission redundancy with/into its existing HARQ buffer. [0162] Alternatively, corresponding to such cases of relatively lower spectral efficiency for a retransmission, redundancy versions of different sizes may be specified. Then, a redundancy version of a smaller size than the size of the initial transmission can be selected for the retransmission. 28 4899-3079-6051\1 P65732WO1 [0163] In some cases, a retransmission is performed by a MAC entity having higher spectral efficiency than a MAC entity used for the initial transmission. FIG. 17B illustrates a second case of an initial transmission and a HARQ-based retransmission through the MAC tower 1702 that uses each of the first MAC entity 1704 the second MAC entity 1706 as was introduced in FIG. 17A, according to embodiments herein. [0164] In the case shown in FIG. 17B, an initial transmission occurs using the first MAC entity 1704 of the MAC tower 1702. It is then determined that HARQ-based retransmission is needed (e.g., because no HARQ ACK for the initial transmission has been received). The retransmission occurs, as illustrated, using the second MAC entity 1706 of the MAC tower 1702. As the second MAC entity 1706 uses more than the single base station used by the first MAC entity 1704, the retransmission occurs according to a higher spectral efficiency than that of the initial transmission. [0165] Corresponding to such cases of relatively higher spectral efficiency for a retransmission, redundancy versions of different sizes may be specified. Then, a redundancy version of a larger size than the size of the initial transmission can be selected for the retransmission. [0166] MAC tower embodiments as discussed herein may impact MAC-level operation at a UE in various ways. For example, in some embodiments, a UE may be informed by the network (e.g., by a CCF) of an identification of base station(s) of a maximum base station set of the MAC tower. This information may be provided to the UE from the network via RRC signaling or MAC control element (MAC CE) signaling. Then, for a particular MAC tower, the UE may ask the network to create and use a MAC entity with particular base station(s) from that maximum base station set. This request may be provided to the network via RRC signaling, MAC CE signaling, or Layer 1 (L1) control signaling. [0167] In some embodiments, the network may inform a UE about MAC entities of a MAC tower that are available/established at the network side. This information can be provided to the UE via RRC signaling or MAC CE signaling. Using this information, the UE may request/recommend the network (e.g., an anchor base station of the MAC tower) to provide a next/upcoming grant for that MAC tower through a particular MAC entity of the MAC tower. Corresponding to cases of either DL and/or UL communication, the request/recommendation may be provided to the network via MAC CE signaling or L1 control signaling. Corresponding to cases of DL communication, the 29 4899-3079-6051\1 P65732WO1 request/recommendation may be sent to the network jointly with a negative acknowledgement (NACK) report for HARQ retransmission. Corresponding to cases of UL communication, the request/recommendation may be provided to the network jointly with a buffer status report (BSR). [0168] Discussion of various aspects with respect to protocol stack architectures that may be implemented in a MAC tower context are now discussed. In some systems a base station at which a buffer of an RLC entity physically resides may be specified. In such cases, the manner in which the RLC entity is accessed from other base stations may up to the network implementation. In some instances, it may be assumed that RLC data is transferred between base station by request. In some other instances, it may be assumed that there is a creation and maintenance of a synchronized copy of an RLC buffer at multiple base stations that may need access to the RLC. [0169] Corresponding to these various cases, in the event a MAC entity and its corresponding RLC entity reside at the same base station, there is no additional latency for MAC-RLC communication. Accordingly, to enable low-latency delivery, embodiments herein contemplate the creation of RLC entities for a DRB to MAC tower pair where the MAC tower of the pair allocates traffic of the DRB of the pair (e.g., the MAC tower is associated to the logical channel represented by the DRB). Note that the RLC entity can be implemented by/sited at the base station that is the anchor base station for the MAC tower in such cases in order to reduce the latency of RLC-MAC interactions. [0170] Corresponding to embodiments herein, it may be understood that RLC entities at the network side and the UE side are in a one-to-one correspondence. [0171] Within this framework, beneficial use of multiple RLC entities can be realized in various scenarios. A first scenario involves low-latency traffic with unacknowledged mode (UM) or transparent mode (TM) RLC entities, in which case the use of multiple independent RLC entities provides additional diversity to improve reliability. In this case, a PDCP entity may implement packet duplication or forward error correction (FEC) packet coding. [0172] A second scenario involves the use of multiple acknowledged mode (AM) RLC entities with asymmetric links, in which the case a first MAC-UE air interface provides a much higher data rate than another MAC-UE air interface. 30 4899-3079-6051\1 P65732WO1 [0173] FIG. 18 illustrates a diagram 1800 for an example Layer 2 (L2) architecture of a cluster of base stations, according to embodiments herein. Within the example L2 architecture, there is a first PDCP entity 1802 for a first DRB 1804, a second PDCP entity 1806 for a second DRB 1808, and a third PDCP entity 1810 for a third DRB 1812. [0174] As shown, the first PDCP entity 1802 operates within the cluster according to a first sub-clustering that uses a first RLC entity 1814 and second RLC entity 1816. The second PDCP entity 1806 operates within the cluster according to a second sub- clustering that uses a third RLC entity 1818, a fourth RLC entity 1820, and a fifth RLC entity 1822. The third DRB 1812 operates within the cluster according to a third sub- cluster that uses the sixth RLC entity 1824. [0175] A first MAC tower 1826, a second MAC tower 1828, and a third MAC tower 1830 have each been configured for use at/by the cluster. The first MAC tower 1826 is configured for use with each of the first RLC entity 1814 and the third RLC entity 1818. Accordingly, it is understood that each individual MAC entity of the first MAC tower 1826 is activated for/useable by each of the first RLC entity 1814 and the third RLC entity 1818. [0176] The second MAC tower 1828 configured for use with the fourth RLC entity 1820. Accordingly, it is understood that each individual MAC entity of the second MAC tower 1828 is activated for/useable by the fourth RLC entity 1820. [0177] The third MAC tower 1830 configured for use with each of the second RLC entity 1816, the fifth RLC entity 1822, and the sixth RLC entity 1824. Accordingly, it is understood that each individual MAC entity of the third MAC tower 1830 is activated for/useable by the each of the second RLC entity 1816, the fifth RLC entity 1822, and the sixth RLC entity 1824. [0178] A PDCP entity may be implemented close to a user plane function (UPF), following re-allocation procedures (e.g., 5G session and service continuity procedures). Accordingly, a one-to-many relationship for PDCP entities to RLC entities is established when a Layer 2 protocol stack is configured or reconfigured. [0179] Note that each of the first MAC tower 1826, the second MAC tower 1828, and the third MAC tower 1830 has a MAC entity counterpart at the UE side of any UE that uses that MAC tower, and that HARQ procedures are implemented on a per MAC tower basis, as has been discussed herein. 31 4899-3079-6051\1 P65732WO1 [0180] Additionally, FEC coding and/or erasure coding may be is implemented at the PDCP on top of multiple wireless links. [0181] For DRBs with low-latency requirements, corresponding RLC entities may be configured in TM and/or UM. [0182] RLC buffers for DRB to MAC tower pairs may be established. In some such embodiments, it may be that an RLC buffer and its associated MAC tower reside at the same base station to allow communication with low latency. In some such embodiments, a copy of the RLC buffer is available at each base station of the maximum base station set of the MAC tower associated with the RLC buffer. [0183] FIG. 19A illustrates a diagram 1902 for an example cluster partitioning of a cluster 1904 serving a UE 1906, according to embodiments herein. As illustrated, the cluster 1904 includes a first base station 1908, a second base station 1910, and a third base station 1912. [0184] As shown, a first radio bearer 1914, a second radio bearer 1916, and a third radio bearer 1918 are to be used within the cluster 1904 corresponding to the implementation of a cluster partitioning procedure 1920 for the cluster 1904. [0185] In some embodiments, results of a cluster partitioning procedure are tailored for QoS purposes (e.g., according to radio-bearer-specific QoSs). A resulting sub-clustering structure for a given radio bearer as determined during a cluster partitioning procedure is made up of one or more sub-clusters. These sub-clusters include subsets of base stations of the cluster that are determined on a per-radio-bearer basis. [0186] In the example cluster partitioning for the cluster 1904 illustrated in FIG. 19A, the cluster partitioning procedure 1920 results in a first sub-clustering 1932 for the first radio bearer 1914. According to the first sub-clustering 1932, the first radio bearer 1914 uses a first sub-cluster 1922 that includes the first base station 1908 and the second base station 1910 and a second sub-cluster 1924 that includes the third base station 1912. [0187] Further, the cluster partitioning procedure 1920 results in a second sub- clustering 1934 for the second radio bearer 1916. According to the second sub-clustering 1934, the second radio bearer 1916 uses a third sub-cluster 1926 that includes each of the first base station 1908, the second base station 1910, and the third base station 1912. [0188] Still further, the cluster partitioning procedure 1920 further results in a third sub-clustering 1936 for the third radio bearer 1918. According to the third sub-clustering 32 4899-3079-6051\1 P65732WO1 1936, the third radio bearer 1918 uses a fourth sub-cluster 1928 that includes the first base station 1908 and a fifth sub-cluster 1930 that uses the second base station 1910 and the third base station 1912. [0189] Note that sub-clustering may be transparent from a UE perspective, such that the UE is enabled to use a single protocol stack that is dedicated to each sub-cluster. [0190] Corresponding to various embodiments herein, different sub-clusters may be assumed to have independent RLC and MAC entities in order to provide for independent data paths. Also, these different sub-clusters may also have independent PHY entities at the network side. [0191] Corresponding to various embodiments herein, RLC and MAC entities of a sub- cluster reside at a base station that is within the corresponding sub-cluster arrangement. [0192] FIG. 19B illustrates a diagram 1938 for an L2 architecture for the cluster 1904 of base stations discussed in FIG. 19A. The example L2 architecture assumes the cluster partitioning of the cluster 1904 as was related in FIG. 19A. [0193] Within the example L2 architecture, there is a first PDCP entity 1940 for the first radio bearer 1914 ("DRB 1" in FIG. 19B), a second PDCP entity 1942 for the second radio bearer 1916 ("DRB 2" in FIG. 19B), and a third PDCP entity 1944 for the third radio bearer 1918 ("DRB 3" in FIG. 19B). [0194] As shown, the first PDCP entity 1940 operates within the cluster 1904 according to the first sub-clustering 1932. This means that the first PDCP entity 1940 uses a first RLC entity 1946 that corresponds to the first sub-cluster 1922 and a second RLC entity 1948 that corresponds to the second sub-cluster 1924. [0195] The second PDCP entity 1942 operates within the cluster 1904 according the second sub-clustering 1934. This means that the second PDCP entity 1942 uses a third RLC entity 1950 that corresponds to the third sub-cluster 1926. [0196] Finally, the third PDCP entity 1944 operates within the cluster 1904 according to the third sub-clustering 1936. This means that the third PDCP entity 1944 uses a fourth RLC entity 1952 that corresponds to the fourth sub-cluster 1928 and a fifth RLC entity 1954 that corresponds to the fifth sub-cluster 1930. [0197] A first MAC tower 1956 and a second MAC tower 1958 are configured for use at/by the cluster. The first MAC tower 1422 is configured for use with each of the first RLC entity 1946, the third RLC entity 1950, and the fourth RLC entity 1952. 33 4899-3079-6051\1 P65732WO1 Accordingly, it is understood that each individual MAC entity of the first MAC tower 1826 is activated for/useable by each of the first RLC entity 1946, the third RLC entity 1950, and the fourth RLC entity 1952. [0198] As illustrated, a first minimum base station set 1960 for the first MAC tower 1956 lists the first base station 1908. This is consistent with the result of the cluster partitioning procedure 1920, in that each of the first sub-cluster 1922 for the first RLC entity 1946, the third sub-cluster 1926 for the third RLC entity 1950, and the fourth sub- cluster 1928 for the fourth RLC entity 1952 includes at least the first base station 1908 (refer to FIG. 19A). [0199] Further, a first maximum base station set 1962 for the first MAC tower 1956 lists each of the first base station 1908, the second base station 1910, and the third base station 1912. This is consistent with the result of the cluster partitioning procedure 1920, in that none of the first sub-cluster 1922 for the first RLC entity 1946, the third sub- cluster 1926 for the third RLC entity 1950, and the fourth sub-cluster 1928 for the fourth RLC entity 1952 uses any base station that is note in the first maximum base station set 1962 (refer to FIG. 19A). [0200] The second MAC tower 1958 is configured for use with each of the second RLC entity 1948 and the fifth RLC entity 1954. Accordingly, it is understood that each individual MAC entity of the second MAC tower 1958 is activated for/useable by each of the second RLC entity 1948 and the fifth RLC entity 1954. [0201] As illustrated, a second minimum base station set 1964 for the second MAC tower 1958962 lists the third base station 1912. This is consistent with the result of the cluster partitioning procedure 1920, in that each of the second sub-cluster 1924 for the second MAC tower 1958 and the fifth sub-cluster 1930 for the fifth RLC entity 1954 includes at least the third base station 1912 (refer to FIG. 19A). [0202] Further, a second maximum base station set 1966 for the second MAC tower 1958 lists each of the second base station 1910 and the third base station 1912. This is consistent with the result of the cluster partitioning procedure 1920, in that neither of the second sub-cluster 1924 for the second RLC entity 1948 and the fifth sub-cluster 1930 for the fifth RLC entity 1954 uses any base station that is not in the second maximum base station set 1966 (refer to FIG. 19A). [0203] One example methodology for developing a valid MAC tower configuration according to a sub-clustering result is now provided. This methodology may be 34 4899-3079-6051\1 P65732WO1 performed at, for example, a CCF of a network that is responsible for establishing relevant aspects/entities of an L2 architecture for a cluster based on a given sub- clustering. 1. First, the relevant sub-cluster structure for each DRB is identified. 2. Then, upon consideration of the full set of all sub-clusters, some subset of the base stations of the cluster are identified as anchor base stations such that each sub- cluster includes at least one anchor base station. Note that one of various possible algorithms for this anchor base station identification may be used (e.g., an algorithm for optimizing/minimizing the total number of anchor base stations may be used). 3. Then, for each anchor base station b: i. DRBs to be connected to anchor base station b are selected. Note that each DRB can be connected to as many anchor base stations b as it has sub- clusters. Note that various possible algorithms/manners for establishing these DRB-to-anchor-base-station connections exist. ii. All sub-clusters of selected DRBs that have anchor base station b are then considered. The intersection of these sub-clusters is established as a minimum base station set, and the union of these sub-clusters is established as a maximum base station set. iii. A MAC tower with anchor base station b, the minimum base station set, the maximum base station set is configured for/to the selected DRBs. iv. An RLC entity for each of the selected DRBs is then created and associated to the MAC tower. [0204] Note that the preceding methodology for developing a valid MAC tower configuration is given by way of example and not by way of limitation. [0205] FIG. 20 illustrates a method 2000 of a CCF of a wireless communication system for operating a cluster of base stations serving a UE, according to embodiments discussed herein. The method 2000 includes identifying 2002, for first one or more sub- clusters used in the cluster that share a first anchor base station of the cluster of base stations, a first minimum set of base stations from among the cluster of base stations, wherein the first minimum set of base stations is present in each of the first one or more sub-clusters. The method 2000 further includes identifying 2004, for the first one or more sub-clusters, a first maximum set of base stations from among the cluster of base stations, wherein the first maximum set of base stations includes all base stations used in 35 4899-3079-6051\1 P65732WO1 any of the first one or more sub-clusters. The method 2000 further includes establishing 2006, at the first anchor base station, a first MAC tower for the first one or more sub- clusters that is configured to operate according to the first minimum set of base stations and the first maximum set of base stations. [0206] In some embodiments, the method 2000 further includes sending, to the first anchor base station of the first MAC tower, an instruction to create a network MAC entity for the first MAC tower; wherein the network MAC entity uses a network MAC entity set of base stations that includes at least the first minimum set of base stations for the first MAC tower and that is bounded by the first maximum set of base stations of the first MAC tower. In some such embodiments, the method 2000 further includes sending, to the UE, an indication that the network MAC entity for the first MAC tower has been created. [0207] In some embodiments, the method 2000 further includes identifying, for second one or more sub-clusters used in the cluster that share a second anchor base station of the cluster of base stations, a second minimum set of base stations from among the cluster of base stations, wherein the second minimum set of base stations is present in each of the second one or more sub-clusters; identifying, for the second one or more sub-clusters, a second maximum set of base stations from among the cluster of base stations, wherein the second maximum set of base stations includes all base stations used in any of the second one or more sub-clusters; and establishing, at the second anchor base station, a second MAC tower for the second one or more sub-clusters that is configured to operate according to the second minimum set of base stations and the second maximum set of base stations. [0208] In some embodiments, the method 2000 further includes sending, to the UE, an identification of the first maximum set of base stations. [0209] In some embodiments, the method 2000 further includes receiving, from a UE, a request to create a network MAC entity for the first MAC tower. [0210] In some embodiments, the method 2000 further includes associating a first radio bearer that uses a first sub-cluster of the first one or more sub-clusters to the anchor base station. [0211] FIG. 21 illustrates a method 2100 of a first anchor base station of a first MAC tower that operates in a cluster of base stations serving a UE, according to embodiments discussed herein. The method 2100 includes receiving 2102, from a CCF, a first 36 4899-3079-6051\1 P65732WO1 instruction to create, at the first anchor base station, a first network MAC entity for the first MAC tower; wherein the network MAC entity uses a first network MAC entity set of base stations that includes at least a minimum set of base stations for the first MAC tower and that is bounded by a maximum set of base stations of the first MAC tower. The method 2100 further includes scheduling 2104, in a first sub-cluster of the cluster, first communications with the UE that use the first network MAC entity of the first MAC tower, wherein the first sub-cluster includes the first network MAC entity set of base stations. [0212] In some embodiments, the method 2100 further includes coordinating with a second anchor base station of a second MAC tower that operates in the cluster to determine a maximum number of TBs to be scheduled by the first MAC tower, wherein the first communications occur within the maximum number of TBs. [0213] In some embodiments, the method 2100 further includes coordinating with a second anchor base station of a second MAC tower that operates in the cluster to determine frequency resources that the first MAC tower uses for scheduling, wherein the first communications are scheduled on the frequency resources. [0214] In some embodiments, the method 2100 further includes coordinating with a second anchor base station of a second MAC tower that operates in the cluster to determine time resources that the first MAC tower uses for scheduling, wherein the first communications are scheduled on the time resources. [0215] In some embodiments, the method 2100 further includes coordinating with a second anchor base station of a second MAC tower that operates in the cluster to determine spatial resources that the first MAC tower uses for scheduling, wherein the first communications are scheduled on the spatial resources. [0216] In some embodiments, the method 2100 further includes receiving, from the UE, a request to schedule the first network MAC entity for the first communications with the UE, wherein the first communications are scheduled according to the request. [0217] In some embodiments, the method 2100 further includes receiving, from the CCF, a second instruction to create, at the first anchor base station, a second network MAC entity for the first MAC tower; wherein the second network MAC entity uses a second network MAC entity set of base stations that includes at least the minimum set of base stations for the first MAC tower and that is bounded by the maximum set of base stations of the first MAC tower; and scheduling, in a second sub-cluster of the cluster, 37 4899-3079-6051\1 P65732WO1 second communications with the UE that use the second network MAC entity of the MAC tower, wherein the second sub-cluster includes the second network MAC entity set of base stations. [0218] FIG. 22 illustrates a method 2200 of a first anchor base station of a MAC tower operating within a cluster of base stations serving a UE, according to embodiments discussed herein. The method 2200 includes scheduling 2202, on a first network MAC entity of the MAC tower that uses a first network MAC entity set of base stations; an initial transmission of data to the UE. The method 2200 further includes determining 2204 that an ACK that the UE has successfully decoded the initial transmission of the data has not been received from the UE. The method 2200 further includes scheduling 2206, on a second network MAC entity of the MAC tower that uses a second network MAC entity set of base stations, a retransmission for the data. [0219] In some embodiments of the method 2200, the first network MAC entity set of base station includes a greater number of base stations than the second network MAC entity set of base stations; the initial transmission is of a first TB size; and the retransmission for the data is of a second TB size that is smaller than the first TB size and comprises a partial redundancy version of the data. [0220] In some embodiments of the method 2200, the first network MAC entity set of base station includes a greater number of base stations than the second network MAC entity set of base stations; and the retransmission for the data comprises a redundancy version of the data that is smaller than the initial transmission of the data. [0221] In some embodiments of the method 2200, the first network MAC entity set of base station includes a lesser number of base stations than the second network MAC entity set of base stations; and the retransmission for the data comprises a redundancy version of the data that is larger than the initial transmission of the data. [0222] In some embodiments of the method 2200, the first anchor base station determines that the ACK has not been received from the UE upon receiving a NACK indicating that the UE has not successfully decoded the initial transmission of the data. [0223] FIG. 23 illustrates a method 2300 of a UE that is served by a cluster of base stations of a wireless communication system, according to embodiments discussed herein. The method 2300 includes receiving 2302, from a CCF, an identification of a maximum set of base stations for a MAC tower for one or more sub-clusters used in the cluster. The method 2300 further includes sending 2304, to the CCF, a request to create, 38 4899-3079-6051\1 P65732WO1 at the MAC tower, a network MAC entity of the MAC tower that uses a network MAC entity set of base stations selected from the maximum set of base stations for the MAC tower. The method 2300 further includes receiving 2306, from the CCF, an indication that that the network MAC entity for the MAC tower has been created. The method 2300 further includes performing 2308 communications with the cluster using a UE MAC entity that corresponds to the network MAC entity. [0224] In some embodiments of the method 2300, the request is sent using RRC signaling. [0225] In some embodiments of the method 2300, the request is sent using a MAC CE. [0226] In some embodiments of the method 2300, the request is sent using L1 signaling. [0227] FIG. 24 illustrates a method 2400 of a UE that is served by a cluster of base stations of a wireless communication system, according to embodiments discussed herein. The method 2400 includes receiving 2402, from a CCF, an indication that a network MAC entity of a MAC tower is available. The method 2400 further includes sending 2404, to an anchor base station of the MAC tower, a request to schedule communications with the cluster that use the network MAC entity. The method 2400 further includes receiving 2406, from the anchor base station, scheduling for the communications using the network MAC entity. The method 2400 further includes performing 2408 the communications using a UE MAC entity that corresponds to the network MAC entity. [0228] In some embodiments of the method 2400, the indication is received in RRC messaging. [0229] In some embodiments of the method 2400, the indication is received in a MAC CE. [0230] In some embodiments of the method 2400, the request is sent in a MAC CE. [0231] In some embodiments of the method 2400, the request is sent in L1 signaling. [0232] In some embodiments of the method 2400, the request is sent jointly with a HARQ NACK. [0233] In some embodiments of the method 2400, the request is sent jointly with a BSR. 39 4899-3079-6051\1 P65732WO1 [0234] FIG. 25 illustrates an example architecture of a wireless communication system 2500, according to embodiments disclosed herein. The following description is provided for an example wireless communication system 2500 that operates in conjunction with the LTE system standards and/or 5G or NR system standards as provided by 3GPP technical specifications. [0235] As shown by FIG. 25, the wireless communication system 2500 includes UE 2502 and UE 2504 (although any number of UEs may be used). In this example, the UE 2502 and the UE 2504 are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks), but may also comprise any mobile or non-mobile computing device configured for wireless communication. [0236] The UE 2502 and UE 2504 may be configured to communicatively couple with a RAN 2506. In embodiments, the RAN 2506 may be NG-RAN, E-UTRAN, etc. The UE 2502 and UE 2504 utilize connections (or channels) (shown as connection 2508 and connection 2510, respectively) with the RAN 2506, each of which comprises a physical communications interface. The RAN 2506 can include one or more base stations (such as base station 2512 and base station 2514) that enable the connection 2508 and connection 2510. [0237] In this example, the connection 2508 and connection 2510 are air interfaces to enable such communicative coupling, and may be consistent with RAT(s) used by the RAN 2506, such as, for example, an LTE and/or NR. [0238] In some embodiments, the UE 2502 and UE 2504 may also directly exchange communication data via a sidelink interface 2516. The UE 2504 is shown to be configured to access an access point (shown as AP 2518) via connection 2520. By way of example, the connection 2520 can comprise a local wireless connection, such as a connection consistent with any IEEE 802.11 protocol, wherein the AP 2518 may comprise a Wi-Fi^® router. In this example, the AP 2518 may be connected to another network (for example, the Internet) without going through a CN 2524. [0239] In embodiments, the UE 2502 and UE 2504 can be configured to communicate using orthogonal frequency division multiplexing (OFDM) communication signals with each other or with the base station 2512 and/or the base station 2514 over a multicarrier communication channel in accordance with various communication techniques, such as, but not limited to, an orthogonal frequency division multiple access (OFDMA) communication technique (e.g., for downlink communications) or a single carrier 40 4899-3079-6051\1 P65732WO1 frequency division multiple access (SC-FDMA) communication technique (e.g., for uplink and ProSe or sidelink communications), although the scope of the embodiments is not limited in this respect. The OFDM signals can comprise a plurality of orthogonal subcarriers. [0240] In some embodiments, all or parts of the base station 2512 or base station 2514 may be implemented as one or more software entities running on server computers as part of a virtual network. In addition, or in other embodiments, the base station 2512 or base station 2514 may be configured to communicate with one another via interface 2522. In embodiments where the wireless communication system 2500 is an LTE system (e.g., when the CN 2524 is an EPC), the interface 2522 may be an X2 interface. The X2 interface may be defined between two or more base stations (e.g., two or more eNBs and the like) that connect to an EPC, and/or between two eNBs connecting to the EPC. In embodiments where the wireless communication system 2500 is an NR system (e.g., when CN 2524 is a 5GC), the interface 2522 may be an Xn interface. The Xn interface is defined between two or more base stations (e.g., two or more gNBs and the like) that connect to 5GC, between a base station 2512 (e.g., a gNB) connecting to 5GC and an eNB, and/or between two eNBs connecting to 5GC (e.g., CN 2524). [0241] The RAN 2506 is shown to be communicatively coupled to the CN 2524. The CN 2524 may comprise one or more network elements 2526, which are configured to offer various data and telecommunications services to customers/subscribers (e.g., users of UE 2502 and UE 2504) who are connected to the CN 2524 via the RAN 2506. The components of the CN 2524 may be implemented in one physical device or separate physical devices including components to read and execute instructions from a machine- readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium). [0242] In embodiments, the CN 2524 may be an EPC, and the RAN 2506 may be connected with the CN 2524 via an S1 interface 2528. In embodiments, the S1 interface 2528 may be split into two parts, an S1 user plane (S1-U) interface, which carries traffic data between the base station 2512 or base station 2514 and a serving gateway (S-GW), and the S1-MME interface, which is a signaling interface between the base station 2512 or base station 2514 and mobility management entities (MMEs). [0243] In embodiments, the CN 2524 may be a 5GC, and the RAN 2506 may be connected with the CN 2524 via an NG interface 2528. In embodiments, the NG 41 4899-3079-6051\1 P65732WO1 interface 2528 may be split into two parts, an NG user plane (NG-U) interface, which carries traffic data between the base station 2512 or base station 2514 and a user plane function (UPF), and the S1 control plane (NG-C) interface, which is a signaling interface between the base station 2512 or base station 2514 and access and mobility management functions (AMFs). [0244] Generally, an application server 2530 may be an element offering applications that use internet protocol (IP) bearer resources with the CN 2524 (e.g., packet switched data services). The application server 2530 can also be configured to support one or more communication services (e.g., VoIP sessions, group communication sessions, etc.) for the UE 2502 and UE 2504 via the CN 2524. The application server 2530 may communicate with the CN 2524 through an IP communications interface 2532. [0245] FIG. 26 illustrates a system 2600 for performing signaling 2634 between a wireless device 2602 and a network device 2618 as supported by a CN device 2636, according to embodiments disclosed herein. The system 2600 may be a portion of a wireless communications system as herein described. The wireless device 2602 may be, for example, a UE of a wireless communication system. The network device 2618 may be, for example, a base station (e.g., an eNB, a gNB, or a sixth generation base station) of a wireless communication system. [0246] The wireless device 2602 may include one or more processor(s) 2604. The processor(s) 2604 may execute instructions such that various operations of the wireless device 2602 are performed, as described herein. The processor(s) 2604 may include one or more baseband processors implemented using, for example, a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. [0247] The wireless device 2602 may include a memory 2606. The memory 2606 may be a non-transitory computer-readable storage medium that stores instructions 2608 (which may include, for example, the instructions being executed by the processor(s) 2604). The instructions 2608 may also be referred to as program code or a computer program. The memory 2606 may also store data used by, and results computed by, the processor(s) 2604. 42 4899-3079-6051\1 P65732WO1 [0248] The wireless device 2602 may include one or more transceiver(s) 2610 that may include radio frequency (RF) transmitter circuitry and/or receiver circuitry that use the antenna(s) 2612 of the wireless device 2602 to facilitate signaling (e.g., the signaling 2634) to and/or from the wireless device 2602 with other devices (e.g., the network device 2618) according to corresponding RATs. [0249] The wireless device 2602 may include one or more antenna(s) 2612 (e.g., one, two, four, or more). For embodiments with multiple antenna(s) 2612, the wireless device 2602 may leverage the spatial diversity of such multiple antenna(s) 2612 to send and/or receive multiple different data streams on the same time and frequency resources. This behavior may be referred to as, for example, MIMO behavior (referring to the multiple antennas used at each of a transmitting device and a receiving device that enable this aspect). MIMO transmissions by the wireless device 2602 may be accomplished according to precoding (or digital beamforming) that is applied at the wireless device 2602 that multiplexes the data streams across the antenna(s) 2612 according to known or assumed channel characteristics such that each data stream is received with an appropriate signal strength relative to other streams and at a desired location in the spatial domain (e.g., the location of a receiver associated with that data stream). Certain embodiments may use single user MIMO (SU-MIMO) methods (where the data streams are all directed to a single receiver) and/or multi user MIMO (MU-MIMO) methods (where individual data streams may be directed to individual (different) receivers in different locations in the spatial domain). [0250] In certain embodiments having multiple antennas, the wireless device 2602 may implement analog beamforming techniques, whereby phases of the signals sent by the antenna(s) 2612 are relatively adjusted such that the (joint) transmission of the antenna(s) 2612 can be directed (this is sometimes referred to as beam steering). [0251] The wireless device 2602 may include one or more interface(s) 2614. The interface(s) 2614 may be used to provide input to or output from the wireless device 2602. For example, a wireless device 2602 that is a UE may include interface(s) 2614 such as microphones, speakers, a touchscreen, buttons, and the like in order to allow for input and/or output to the UE by a user of the UE. Other interfaces of such a UE may be made up of transmitters, receivers, and other circuitry (e.g., other than the transceiver(s) 2610/ antenna(s) 2612 already described) that allow for communication between the UE 43 4899-3079-6051\1 P65732WO1 and other devices and may operate according to known protocols (e.g., Wi-Fi^®, Bluetooth^®, and the like). [0252] The wireless device 2602 may include a MAC tower module 2616. The MAC tower module 2616 may be implemented via hardware, software, or combinations thereof. For example, the MAC tower module 2616 may be implemented as a processor, circuit, and/or instructions 2608 stored in the memory 2606 and executed by the processor(s) 2604. In some examples, the MAC tower module 2616 may be integrated within the processor(s) 2604 and/or the transceiver(s) 2610. For example, the MAC tower module 2616 may be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the processor(s) 2604 or the transceiver(s) 2610. [0253] The MAC tower module 2616 may be used for various aspects of the present disclosure, for example, aspects of FIG. 23 and/or FIG. 24. For example, the MAC tower module 2616 may configure the wireless device 2602 to communicate with a CCF and/or a base station (e.g., an anchor base station) for purposes of establishing, creating, activating, and/or using a MAC tower according to embodiments discussed herein. [0254] The network device 2618 may include one or more processor(s) 2620. The processor(s) 2620 may execute instructions such that various operations of the network device 2618 are performed, as described herein. The processor(s) 2620 may include one or more baseband processors implemented using, for example, a CPU, a DSP, an ASIC, a controller, an FPGA device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. [0255] The network device 2618 may include a memory 2622. The memory 2622 may be a non-transitory computer-readable storage medium that stores instructions 2624 (which may include, for example, the instructions being executed by the processor(s) 2620). The instructions 2624 may also be referred to as program code or a computer program. The memory 2622 may also store data used by, and results computed by, the processor(s) 2620. [0256] The network device 2618 may include one or more transceiver(s) 2626 that may include RF transmitter circuitry and/or receiver circuitry that use the antenna(s) 2628 of the network device 2618 to facilitate signaling (e.g., the signaling 2634) to and/or from the network device 2618 with other devices (e.g., the wireless device 2602) according to corresponding RATs. 44 4899-3079-6051\1 P65732WO1 [0257] The network device 2618 may include one or more antenna(s) 2628 (e.g., one, two, four, or more). In embodiments having multiple antenna(s) 2628, the network device 2618 may perform MIMO, digital beamforming, analog beamforming, beam steering, etc., as has been described. [0258] The network device 2618 may include one or more interface(s) 2630. The interface(s) 2630 may be used to provide input to or output from the network device 2618. For example, a network device 2618 that is a base station may include interface(s) 2630 made up of transmitters, receivers, and other circuitry (e.g., other than the transceiver(s) 2626/antenna(s) 2628 already described) that enables the base station to communicate with other equipment in a core network, and/or that enables the base station to communicate with external networks, computers, databases, and the like for purposes of operations, administration, and maintenance of the base station or other equipment operably connected thereto. As another example, the network device 2618 may communicate with the CN device 2636 on an interface 2648 of the interface(s) 2630 (which, in, for example, NR cases, may be an NG interface or in LTE cases may be an S1 interface). [0259] The network device 2618 may include a MAC tower module 2632. The MAC tower module 2632 may be implemented via hardware, software, or combinations thereof. For example, the MAC tower module 2632 may be implemented as a processor, circuit, and/or instructions 2624 stored in the memory 2622 and executed by the processor(s) 2620. In some examples, the MAC tower module 2632 may be integrated within the processor(s) 2620 and/or the transceiver(s) 2626. For example, the MAC tower module 2632 may be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the processor(s) 2620 or the transceiver(s) 2626. [0260] The MAC tower module 2632 may be used for various aspects of the present disclosure, for example, aspects of FIG. 20, FIG. 21, and/or FIG. 22. For example, the MAC tower module 2632 may configure a network device 2618 that is acting as part of a CCF to communicate with a base station (e.g., an anchor base station) and/or a UE for purposes of establishing, creating, activating, and/or using a MAC tower according to embodiments discussed herein. As another example, the MAC tower module 2632 may configure a network device 2618 that is operating as an anchor base station of a MAC 45 4899-3079-6051\1 P65732WO1 tower to communicate with a CCF and/or UE for purposes of establishing, creating, activating, and/or using a MAC tower according to embodiments discussed herein. [0261] The CN device 2636 may include one or more processor(s) 2638. The processor(s) 2638 may execute instructions such that various operations of the CN device 2636 are performed, as described herein. The processor(s) 2638 may include one or more baseband processors implemented using, for example, a CPU, a DSP, an ASIC, a controller, an FPGA device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. [0262] The CN device 2636 may include a memory 2640. The memory 2640 may be a non-transitory computer-readable storage medium that stores instructions 2642 (which may include, for example, the instructions being executed by the processor(s) 2638). The instructions 2642 may also be referred to as program code or a computer program. The memory 2640 may also store data used by, and results computed by, the processor(s) 2638. [0263] The CN device 2636 may include one or more interface(s) 2644. The interface(s) 2644 may be used to provide input to or output from the CN device 2636. For example, a CN device 2636 may communicate with the network device 2618 on an interface 2648 of the interface(s) 2644 (which, in, for example, NR cases, may be an NG interface or in LTE cases may be an S1 interface). [0264] The CN device 2636 may include a MAC tower module 2646. The MAC tower module 2646 may be implemented via hardware, software, or combinations thereof. For example, the MAC tower module 2646 may be implemented as a processor, circuit, and/or instructions 2642 stored in the memory 2640 and executed by the processor(s) 2638. In some examples, the MAC tower module 2646 may be integrated within the processor(s) 2638. For example, the MAC tower module 2646 may be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the processor(s) 2638. [0265] The MAC tower module 2646 may be used for various aspects of the present disclosure, for example, aspects of FIG. 20. For example, the MAC tower module 2646 may configure the CN device 2636 that is acting as part of a CCF to communicate with a base station (e.g., an anchor base station) and/or a UE for purposes of establishing, creating, activating, and/or using a MAC tower according to embodiments discussed herein. 46 4899-3079-6051\1 P65732WO1 [0266] Embodiments contemplated herein include an apparatus comprising means to perform one or more elements of any of the method 2300 and/or the method 2400. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 2602 that is a UE, as described herein). [0267] Embodiments contemplated herein include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of any of the method 2300 and/or the method 2400. This non-transitory computer-readable media may be, for example, a memory of a UE (such as a memory 2606 of a wireless device 2602 that is a UE, as described herein). [0268] Embodiments contemplated herein include an apparatus comprising logic, modules, or circuitry to perform one or more elements of any of the method 2300 and/or the method 2400. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 2602 that is a UE, as described herein). [0269] Embodiments contemplated herein include an apparatus comprising: one or more processors and one or more computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform one or more elements of any of the method 2300 and/or the method 2400. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 2602 that is a UE, as described herein). [0270] Embodiments contemplated herein include a signal as described in or related to one or more elements of any of the method 2300 and/or the method 2400. [0271] Embodiments contemplated herein include a computer program or computer program product comprising instructions, wherein execution of the program by a processor is to cause the processor to carry out one or more elements of any of the method 2300 and/or the method 2400. The processor may be a processor of a UE (such as a processor(s) 2604 of a wireless device 2602 that is a UE, as described herein). These instructions may be, for example, located in the processor and/or on a memory of the UE (such as a memory 2606 of a wireless device 2602 that is a UE, as described herein). [0272] Embodiments contemplated herein include an apparatus comprising means to perform one or more elements of any of the method 2100 and/or the method 2200. This apparatus may be, for example, an apparatus of a base station (such as a network device 2618 that is a base station, as described herein). 47 4899-3079-6051\1 P65732WO1 [0273] Embodiments contemplated herein include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of any of the method 2100 and/or the method 2200. This non-transitory computer-readable media may be, for example, a memory of a base station (such as a memory 2622 of a network device 2618 that is a base station, as described herein). [0274] Embodiments contemplated herein include an apparatus comprising logic, modules, or circuitry to perform one or more elements of any of the method 2100 and/or the method 2200. This apparatus may be, for example, an apparatus of a base station (such as a network device 2618 that is a base station, as described herein). [0275] Embodiments contemplated herein include an apparatus comprising: one or more processors and one or more computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform one or more elements of any of the method 2100 and/or the method 2200. This apparatus may be, for example, an apparatus of a base station (such as a network device 2618 that is a base station, as described herein). [0276] Embodiments contemplated herein include a signal as described in or related to one or more elements of any of the method 2100 and/or the method 2200. [0277] Embodiments contemplated herein include a computer program or computer program product comprising instructions, wherein execution of the program by a processing element is to cause the processing element to carry out one or more elements of any of the method 2100 and/or the method 2200. The processor may be a processor of a base station (such as a processor(s) 2620 of a network device 2618 that is a base station, as described herein). These instructions may be, for example, located in the processor and/or on a memory of the base station (such as a memory 2622 of a network device 2618 that is a base station, as described herein). [0278] Embodiments contemplated herein include an apparatus comprising means to perform one or more elements of the method 2000. This apparatus may be, for example, an apparatus of a base station (such as a network device 2618 that is a base station, as described herein) and/or of a CN (such as the CN device 2636, as described herein). It is further contemplated that this apparatus may be one of many such apparatuses working 48 4899-3079-6051\1 P65732WO1 together in a distributed fashion to perform the one or more elements of the method 2000. [0279] Embodiments contemplated herein include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of the method 2000. This non-transitory computer- readable media may be, for example, a memory of a base station (such as a memory 2640 of a network device 2618 that is a base station, as described herein) and/or of a CN (such as the memory 2640 of a CN device 2636, as described herein). It is further contemplated that the electronic device may be one of many such electronic devices working together in a distributed fashion to perform the one or more elements of the method 2000. [0280] Embodiments contemplated herein include an apparatus comprising logic, modules, or circuitry to perform one or more elements of the method 2000. This apparatus may be, for example, an apparatus of a base station (such as a network device 2618 that is a base station, as described herein) and/or of a CN (such as the CN device 2636, as described herein). It is further contemplated that this apparatus may be one of many such apparatuses working together in a distributed fashion to perform the one or more elements of the method 2000. [0281] Embodiments contemplated herein include an apparatus comprising: one or more processors and one or more computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform one or more elements of the method 2000. This apparatus may be, for example, an apparatus of a base station (such as a network device 2618 that is a base station, as described herein) and/or of a CN (such as the CN device 2636, as described herein). It is further contemplated that this apparatus may be one of many such apparatuses working together in a distributed fashion to perform the one or more elements of the method 2000. [0282] Embodiments contemplated herein include a signal as described in or related to one or more elements of the method 2000. [0283] Embodiments contemplated herein include a computer program or computer program product comprising instructions, wherein execution of the program by a processing element is to cause the processing element to carry out one or more elements 49 4899-3079-6051\1 P65732WO1 of the method 2000. The processor may be a processor of a base station (such as a processor(s) 2620 of a network device 2618 that is a base station, as described herein). These instructions may be, for example, located in the processor and/or on a memory of the base station (such as a memory 2622 of a network device 2618 that is a base station, as described herein). The processor may be a processor of a CN device (such as a processor(s) 2638 of a CN device 2636, as described herein). These instructions may be, for example, located in the processor and/or on a memory of the CN device (such as a memory 2640 of a CN device 2636, as described herein). It is further contemplated that the processing element may be one of many such processing elements working together in a distributed fashion to perform the one or more elements of the method 2000. [0284] For one or more embodiments, at least one of the components set forth in one or more of the preceding figures may be configured to perform one or more operations, techniques, processes, and/or methods as set forth herein. For example, a baseband processor as described herein in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth herein. For another example, circuitry associated with a UE, base station, network element, etc. as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth herein. [0285] Any of the above described embodiments may be combined with any other embodiment (or combination of embodiments), unless explicitly stated otherwise. The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments. [0286] Embodiments and implementations of the systems and methods described herein may include various operations, which may be embodied in machine-executable instructions to be executed by a computer system. A computer system may include one or more general-purpose or special-purpose computers (or other electronic devices). The computer system may include hardware components that include specific logic for performing the operations or may include a combination of hardware, software, and/or firmware. 50 4899-3079-6051\1 P65732WO1 [0287] It should be recognized that the systems described herein include descriptions of specific embodiments. These embodiments can be combined into single systems, partially combined into other systems, split into multiple systems or divided or combined in other ways. In addition, it is contemplated that parameters, attributes, aspects, etc. of one embodiment can be used in another embodiment. The parameters, attributes, aspects, etc. are merely described in one or more embodiments for clarity, and it is recognized that the parameters, attributes, aspects, etc. can be combined with or substituted for parameters, attributes, aspects, etc. of another embodiment unless specifically disclaimed herein. [0288] It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. [0289] Although the foregoing has been described in some detail for purposes of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles thereof. It should be noted that there are many alternative ways of implementing both the processes and apparatuses described herein. Accordingly, the present embodiments are to be considered illustrative and not restrictive, and the description is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims. 51 4899-3079-6051\1 P65732WO1

Claims

CLAIMS 1. A method of a clustering control function (CCF) of a wireless communication system for operating a cluster of base stations serving a user equipment (UE), comprising: identifying, for first one or more sub-clusters used in the cluster that share a first anchor base station of the cluster of base stations, a first minimum set of base stations from among the cluster of base stations, wherein the first minimum set of base stations is present in each of the first one or more sub-clusters; identifying, for the first one or more sub-clusters, a first maximum set of base stations from among the cluster of base stations, wherein the first maximum set of base stations includes all base stations used in any of the first one or more sub-clusters; and establishing, at the first anchor base station, a first medium access control (MAC) tower for the first one or more sub-clusters that is configured to operate according to the first minimum set of base stations and the first maximum set of base stations.

2. The method of claim 1, further comprising sending, to the first anchor base station of the first MAC tower, an instruction to create a network MAC entity for the first MAC tower; wherein the network MAC entity uses a network MAC entity set of base stations that includes at least the first minimum set of base stations for the first MAC tower and that is bounded by the first maximum set of base stations of the first MAC tower.

3. The method of claim 2, further comprising sending, to the UE, an indication that the network MAC entity for the first MAC tower has been created.

4. The method of claim 1, further comprising: identifying, for second one or more sub-clusters used in the cluster that share a second anchor base station of the cluster of base stations, a second minimum set of base stations from among the cluster of base stations, wherein the second minimum set of base stations is present in each of the second one or more sub-clusters; identifying, for the second one or more sub-clusters, a second maximum set of base stations from among the cluster of base stations, wherein the second maximum set of base stations includes all base stations used in any of the second one or more sub- clusters; and 52 4899-3079-6051\1 P65732WO1 establishing, at the second anchor base station, a second MAC tower for the second one or more sub-clusters that is configured to operate according to the second minimum set of base stations and the second maximum set of base stations.

5. The method of claim 1, further comprising sending, to the UE, an identification of the first maximum set of base stations.

6. The method of claim 1, further comprising receiving, from a UE, a request to create a network MAC entity for the first MAC tower.

7. The method of claim 1, further comprising associating a first radio bearer that uses a first sub-cluster of the first one or more sub-clusters to the anchor base station.

8. A method of a first anchor base station of a first medium access control (MAC) tower that operates in a cluster of base stations serving a user equipment (UE), comprising: receiving, from a clustering control function (CCF), a first instruction to create, at the first anchor base station, a first network MAC entity for the first MAC tower; wherein the network MAC entity uses a first network MAC entity set of base stations that includes at least a minimum set of base stations for the first MAC tower and that is bounded by a maximum set of base stations of the first MAC tower; and scheduling, in a first sub-cluster of the cluster, first communications with the UE that use the first network MAC entity of the first MAC tower, wherein the first sub- cluster includes the first network MAC entity set of base stations.

9. The method of claim 8, further comprising coordinating with a second anchor base station of a second MAC tower that operates in the cluster to determine a maximum number of transport blocks (TBs) to be scheduled by the first MAC tower, wherein the first communications occur within the maximum number of TBs.

10. The method of claim 8, further comprising coordinating with a second anchor base station of a second MAC tower that operates in the cluster to determine frequency resources that the first MAC tower uses for scheduling, wherein the first communications are scheduled on the frequency resources.

11. The method of claim 8, further comprising coordinating with a second anchor base station of a second MAC tower that operates in the cluster to determine time resources 53 4899-3079-6051\1 P65732WO1 that the first MAC tower uses for scheduling, wherein the first communications are scheduled on the time resources.

12. The method of claim 8, further comprising coordinating with a second anchor base station of a second MAC tower that operates in the cluster to determine spatial resources that the first MAC tower uses for scheduling, wherein the first communications are scheduled on the spatial resources.

13. The method of claim 8, further comprising receiving, from the UE, a request to schedule the first network MAC entity for the first communications with the UE, wherein the first communications are scheduled according to the request.

14. The method of claim 8, further comprising: receiving, from the CCF, a second instruction to create, at the first anchor base station, a second network MAC entity for the first MAC tower; wherein the second network MAC entity uses a second network MAC entity set of base stations that includes at least the minimum set of base stations for the first MAC tower and that is bounded by the maximum set of base stations of the first MAC tower; and scheduling, in a second sub-cluster of the cluster, second communications with the UE that use the second network MAC entity of the MAC tower, wherein the second sub-cluster includes the second network MAC entity set of base stations.

15. A method of a first anchor base station of a medium access control (MAC) tower operating within a cluster of base stations serving a user equipment (UE), comprising: scheduling, on a first network MAC entity of the MAC tower that uses a first network MAC entity set of base stations; an initial transmission of data to the UE; determining that an acknowledgment (ACK) that the UE has successfully decoded the initial transmission of the data has not been received from the UE; scheduling, on a second network MAC entity of the MAC tower that uses a second network MAC entity set of base stations, a retransmission for the data.

16. The method of claim 15, wherein: the first network MAC entity set of base station includes a greater number of base stations than the second network MAC entity set of base stations; the initial transmission is of a first transport block (TB) size; and 54 4899-3079-6051\1 P65732WO1 the retransmission for the data is of a second TB size that is smaller than the first TB size and comprises a partial redundancy version of the data.

17. The method of claim 15, wherein: the first network MAC entity set of base station includes a greater number of base stations than the second network MAC entity set of base stations; and the retransmission for the data comprises a redundancy version of the data that is smaller than the initial transmission of the data.

18. The method of claim 15, wherein: the first network MAC entity set of base station includes a lesser number of base stations than the second network MAC entity set of base stations; and the retransmission for the data comprises a redundancy version of the data that is larger than the initial transmission of the data.

19. The method of claim 15, wherein the first anchor base station determines that the ACK has not been received from the UE upon receiving a negative acknowledgment (NACK) indicating that the UE has not successfully decoded the initial transmission of the data.

20. A method of a user equipment (UE) that is served by a cluster of base stations of a wireless communication system, comprising: receiving, from a clustering control function (CCF), an identification of a maximum set of base stations for a MAC tower for one or more sub-clusters used in the cluster; sending, to the CCF, a request to create, at the MAC tower, a network MAC entity of the MAC tower that uses a network MAC entity set of base stations selected from the maximum set of base stations for the MAC tower; receiving, from the CCF, an indication that that the network MAC entity for the MAC tower has been created; and performing communications with the cluster using a UE MAC entity that corresponds to the network MAC entity.

21. The method of claim 20, wherein the request is sent using radio resource control (RRC) signaling. 55 4899-3079-6051\1 P65732WO1

22. The method of claim 20, wherein the request is sent using a MAC control element (MAC CE).

23. The method of claim 20, wherein the request is sent using layer 1 (L1) signaling.

24. A method of a user equipment (UE) that is served by a cluster of base stations of a wireless communication system, comprising: receiving, from a clustering control function (CCF), an indication that a network MAC entity of a MAC tower is available; sending, to an anchor base station of the MAC tower, a request to schedule communications with the cluster that use the network MAC entity; receiving, from the anchor base station, scheduling for the communications using the network MAC entity; and performing the communications using a UE MAC entity that corresponds to the network MAC entity.

25. The method of claim 24, wherein the indication is received in radio resource control (RRC) messaging.

26. The method of claim 24, wherein the indication is received in a MAC control element (MAC CE).

27. The method of claim 24, wherein the request is sent in a MAC control element (MAC CE).

28. The method of claim 24, wherein the request is sent in layer 1 (L1) signaling.

29. The method of claim 24, wherein the request is sent jointly with a hybrid automatic repeat request (HARQ) negative acknowledgement (NACK).

30. The method of claim 24, wherein the request is sent jointly with a buffer status report (BSR).

31. An apparatus comprising means to perform the method of any of claim 1 to claim 30.

32. A computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform the method of any of claim 1 to claim 30. 56 4899-3079-6051\1 P65732WO1

33. An apparatus comprising logic, modules, or circuitry to perform the method of any of claim 1 to claim 30.

34. A baseband processor for a user equipment (UE) that is configured to cause the UE to perform one or more elements of any one of claim 20 to claim 30.

35. A baseband processor for a base station that is configured to cause the base station to perform one or more elements of any one of claim 1 to claim 19. 57 4899-3079-6051\1 P65732WO1