CN114208385A - Congestion management - Google Patents

Abstract

A distributed congestion management system for cellular systems having different transmission types is disclosed. The transmission limit parameter is adjusted based on the transmission type and traffic priority.

Description

Congestion management

Technical Field

The following disclosure relates to the technical field of congestion management, and in particular to congestion management in V2X systems with different transport types.

Background

Wireless communication systems such as third generation (3G) mobile telephone standards and technologies are well known. Such 3G standards and techniques have been developed by the third generation partnership project (3 GPP). Third generation wireless communications have typically been developed to support macrocell mobile telephone communications. Communication systems and networks have evolved towards broadband and mobile systems.

In a cellular wireless communication system, User Equipment (UE) is connected to a Radio Access Network (RAN) over a radio link. The radio access network comprises a set of base stations providing radio links for user equipment located in cells covered by the base stations and an interface to a Core Network (CN) providing overall network control. It should be understood that the radio access network and the core network each perform respective functions related to the overall network. For convenience, the term cellular network refers to a combined radio access network and core network, and it is understood that the term refers to the corresponding system for performing the disclosed functions.

The third generation partnership project has developed a so-called Long Term Evolution (LTE) system, evolved universal mobile telecommunications system terrestrial radio access network (E-UTRAN), for mobile access networks in which one or more macro cells are supported by base stations of enodebs or enbs (evolved nodebs). Currently, LTE systems are further evolving towards so-called 5G or NR (new radio) systems, in which one or more cells are supported by the base station of the gNB. NR is proposed to use an Orthogonal Frequency Division Multiplexing (OFDM) physical transmission format.

In conventional cellular communication networks, all signaling is between each mobile device and the base station, rather than directly between the mobile devices, even though the mobile devices are within wireless communication range of each other. This may result in inefficient use of radio transmission resources and may increase the use of base station resources. Sidelink (or sidelink, etc.) communications allow mobile devices to communicate directly, rather than via a base station, thereby increasing the utilization of radio and base station resources. The sidelink communication is particularly noteworthy for machine-to-machine communication, especially for vehicle-to-vehicle (V2V) and vehicle-to-everything/anything (V2X).

The following disclosure relates to various improvements to cellular wireless communication systems, and in particular to sidelink communications in such systems.

Disclosure of Invention

The purpose of the summary is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later. This summary is not intended to specifically identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

The present invention provides a method of distributed congestion control in a cellular communication system, the method being performed at a transmitting station of the cellular communication system and comprising the steps of: calculating an indication of a transmission channel state available to the transmitting station; calculating the channel utilization rate required by the transmitting station for transmitting data; calculating a channel utilization rate limit value according to the state indication of the transmission channel and the flow type of the transmission data; comparing the required channel utilization to a channel utilization limit; if the required channel utilization does not exceed the channel utilization limit, the data is transmitted.

The traffic types may include unicast traffic, multicast traffic, and broadcast traffic.

The channel utilization limits for the multicast transmission type and the broadcast transmission type are higher than the channel utilization limit for the unicast transmission type.

The channel utilization limit for the broadcast transmission type is higher than the channel utilization limit for the multicast transmission type.

The channel utilization limit for multicast communications is dependent on the size of the group.

The status indication of the transmission channel is the channel busy rate.

The required channel utilization and channel utilization limit is the channel occupancy.

The calculating a channel utilization limit comprises: adjusting the starting value, the adjusting being based on at least one of a traffic type of the transmission data and a priority of the transmission data.

The step of adjusting the start value is based on a quality of service (QoS) priority of a traffic type and a traffic content priority.

The traffic content priority constitutes the most significant bits of the QoS priority and the traffic type constitutes the least significant bits of the QoS priority.

If the required channel utilization exceeds the channel utilization limit, no data is sent.

If the required channel utilization exceeds the channel utilization limit, the method may include: adjusting transmission parameters of the data to reduce the required channel utilization to a value not exceeding the channel utilization limit, and transmitting the data with the adjusted transmission parameters.

The present invention also provides a method of performing Distributed Congestion Control (DCC) in a cellular communication system. The transmission restriction parameter is used to restrict access to transmission resources by the transmitting station. The transmission limitation parameter is adjusted according to the transmission type (unicast, multicast or broadcast) and optionally the priority of the transmission traffic.

The present invention also provides a method of distributed congestion control in a cellular communication system, the method being performed at a transmitting station of the cellular communication system and comprising the steps of: mapping the transmitted quality of service priority to a traffic priority and a transmission type to prioritize broadcast and multicast transmissions over unicast transmissions; multicast transmissions of a particular priority are less affected than unicast transmissions of the same priority.

The transmitting station is a user equipment or a base station.

The non-transitory computer readable medium may include at least one of the group consisting of: hard disks, compact disk read-only memories (CD-ROMs), optical storage devices, magnetic storage devices, read-only memories, programmable read-only memories, erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROM), and flash memories.

Drawings

Further details, aspects and embodiments of the invention are described, by way of example, with reference to the accompanying drawings. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. To facilitate understanding, the same reference numerals have been included in the various figures.

Figure 1 shows selected elements of a cellular communication system;

FIGS. 2 and 3 show examples of adjustment of the occupancy limit of a channel; and

fig. 4 shows a flow chart of a congestion management system.

Detailed Description

Those skilled in the art will recognize and appreciate that the specifics of the described examples are merely illustrative of some embodiments and that the teachings set forth herein are applicable in a variety of alternative contexts.

Fig. 1 shows a schematic diagram of three base stations (e.g., enbs or gnbs, depending on the particular cellular standard and terminology) forming a cellular network. Typically, each base station will be deployed by one cellular network operator to provide geographic coverage to user equipment in the area. The base stations form a Radio Access Network (RAN). Each base station provides radio coverage to user equipment in its area or cell. The base stations are interconnected via an X2 interface and connected to the core network via an S1 interface. It should be understood that only basic details are shown in order to illustrate key features of the cellular network. A PC5 interface is provided between user devices for Sidelink (SL) communications. The interface and component names associated with fig. 1 are used as examples only, and different systems operating on the same principles may use different nomenclature.

Each base station includes hardware and software to implement the functionality of the radio access network. The functions include communicating with the core network and other base stations, transmitting control signals and data signals between the core network and user equipment, and maintaining wireless communication with the user equipment associated with each base station. The core network includes hardware and software to implement network functions such as overall network management and control, and call routing and data routing.

It is possible that multiple user equipments may be located in a small geographical area, all of which attempt to share transmission resources for uplink, downlink and sidelink communications. The main area of interest in the present invention is sidelink communications. To manage access to the transmission resources, Distributed Congestion Control (DCC) may be used, where all transmission elements work together to fairly share resources and keep the channel unsaturated. Two key parameters used in distributed congestion control are the Channel Busy Rate (CBR) and the Channel Occupancy rate (CR).

The channel busy rate is defined as the portion of the sub-channel for which the RSSI exceeds the threshold value as measured within the resource pool sensed in the last 100 sub-frames. The channel busy rate provides an estimate of the overall state of the transmission channel.

The occupancy CR of the subframe n is the number of subchannels used by the relevant user equipment in the subframe [ n-a, n-1] and the number of subchannels granted by the relevant user equipment to the subframe [ n, n + b ] divided by the total number of subchannels in the subframe [ n-a, n + b ], where a and b are defined to satisfy the condition that a + b +1 is 1000, and a > is 500. Thus, the channel occupancy is a measure of the fraction of available resources used by the relevant user equipment.

The terms "channel busy rate" and "channel occupancy" are specific names given to appropriate metrics in an LTE cellular system and are examples of appropriate metrics for a distributed congestion control function. The use of these terms is not intended to limit the present invention to these particular LTE metrics, but is merely for clarity of disclosure and to indicate the types of metrics on which the systems and methods of the present invention may be based. Thus, the precise details of the metrics and their names may be changed without departing from the meaning of the present invention.

The channel occupancy provides a profile (snapshot) of the channel usage of the transmitting station itself. For sharing transmission resources, a channel occupancy limit (CR) for each interval of channel busy rate values_limit) Is defined as the one that the transmitting station should not exceed. In this way, it can be avoided that a particular user equipment monopolizes the transmission resource. When a transmitting station (which term is used to describe an element of a cellular system, such as a user equipment that is making a sidelink or uplink transmission, or a base station that is making a downlink transmission) is ready to transmit, the calculated channel busy value is mapped to an associated time interval and an associated occupancy limit is obtained. The duty cycle limit may be based on radio resourcesControl (RRC) or other configuration message. If the channel occupancy of the transmitting station does not exceed the channel occupancy limit, the transmission may continue, whereas if the channel occupancy of the transmitting station exceeds the channel occupancy limit, the channel occupancy of the transmitting station needs to be reduced to not exceed the channel occupancy limit. The transmitting station may utilize any suitable technique to reduce its channel occupancy, such as dropping transmissions, increasing the coding modulation scheme (MCS) to reduce required resources or adjusting transmit power. In a particular embodiment, the transmitting station is a user equipment and all communication links are sidelink communications between user equipments.

Sidelink communications in the new radio V2X system are intended to support unicast, multicast and broadcast operations, so that a transmission may be intended for a single receiver UE, a group of receiver UEs or all receiver UEs capable of receiving the transmission. These different transmission types complicate the implementation of distributed congestion control systems, since each transmission type (transmission type) has a variable impact on various metrics of cellular system performance.

Each transmission type has a similar contribution to the utilization of the transmission resource, since it is measured by the channel busy rate, and therefore the drop impact of each transmission type has a similar effect on congestion. However, the indicator (KPI) impact for other cellular systems may vary from type to type. For example, from a quality of service (QoS) perspective, packet loss is measured at the receiver, and thus, in QoS statistics, one packet loss in one multicast (K members of the group) results in K-1 packet losses. Similarly, for broadcast transmissions, all transmitting stations within the broadcast range cannot receive dropped transmissions. These examples are in contrast to a packet loss in the case of dropping unicast packet transmissions.

The use of hybrid automatic repeat request (HARQ) feedback may also affect dropping different types of transmissions. Hybrid automatic repeat request can be used for acknowledged/unacknowledged (ACK/NACK) feedback (for unicast and multicast) or for unacknowledged only feedback (for multicast). In a hybrid automatic repeat request system, if congestion control is used after the bypass control information (SCI) (or other scheduling message) is sent, packet loss at the transmitting end triggers a negative feedback message from the receiving end. The feedback message is sent by each receiver, so that dropping the multicast transmission by one of a group of transmit stations (K transmit stations) results in K-1 NACK feedback messages. In unacknowledged mode, multiple unacknowledged feedback messages may be transmitted on common resources, thus resulting in high power interference on the corresponding common resources, while in acknowledged/unacknowledged mode, multiple unacknowledged feedback messages may be transmitted on dedicated resources, which may result in increased resource utilization, thus exacerbating the packet loss problem.

It follows that dropping multicast transmissions typically (although not always) has a greater K-1 impact on the quality of service of the system than dropping unicast transmissions. In the distributed congestion control process, it may be considered to adjust the occupancy limit of the channel based on the transmission type to have a greater impact. For example, the duty cycle limit for multicast transmissions may be increased as compared to unicast transmissions. Thus, the transmitting station is allowed greater access to the transmission resources when multicast transmission is performed than when unicast transmission is performed. The increment of the duty cycle limit may be a set value for all multicast transmissions or may depend on the group size (K). If the transmitting station does not know the size of the group, a default group size may be assigned or the transmission may be considered a broadcast transmission. Unicast transmissions are more likely to be dropped than multicast transmissions in terms of the effect of adjusting the occupancy limit for the multicast transmission.

Similarly, the duty cycle limit may also be adjusted for broadcast transmissions. The resizing may be based on the estimated group size, or a default value may be used. There may be a greater impact if it is assumed that there are more transmitting stations within the range of the broadcast transmission than there are transmitting stations in a group of multicast transmissions. Thus, the channel occupancy limit for broadcast transmissions may be increased by a greater amount than the channel occupancy limit for multicast transmissions. Unicast transmissions may then be more likely to be dropped than multicast transmissions, which may be more likely to be dropped than broadcast transmissions.

The cellular system may allow different priority levels of traffic so that certain traffic may be prioritized for reliability and/or latency. Thus, the impact of dropping a particular transmission on the QoS metric may also depend on the priority of dropping the transmission. This may also be a factor in the decision of the transmitting station on how to handle congestion using the distributed congestion control system. In the discussion that follows, higher priority is represented by lower numbers, e.g.,priority 1>priority 2.

The priority of traffic may also be considered in a distributed congestion control system by adjusting the occupancy limit based on priority. The transmission type and priority are selectively adjusted so that priority N multicast is less affected than priority N unicast, but still more affected than priority N +1 unicast packets (priority N +1 is less urgent than priority N). That is, the duty cycle limit is adjusted to CR_limit(unicast,prio N)<CR_limit(groupcast,prio N)<CR_limit(broadcast,prio N)<CR_limit(unicast, prio N-1), where unicast denotes unicast, groupcast denotes multicast, broadpast denotes broadcast, and prio denotes priority, as shown in fig. 2. The priority-based adjustment may or may not be in addition to the transmission-type-based adjustment.

As described above, the adjustment of the occupancy limit for multicast transmissions may depend on the size (K) of the group, such that larger multicast transmissions are less likely to be dropped than smaller multicast transmissions. The adjustment of the group size to the occupancy limit may be proportional or based on a range of group sizes with different adjustments, each range may control complexity. That is, CR_limit(unicast,prio N)<CR_limit(K1-members groupcast,prio N)<CR_limit(K2-members groupcast,prio N)<CR_limit(broadcast,prio N)<CR_limit(unicast, prio N-1) wherein K1<K2, K1 and K2 indicate the size of the group, as shown in FIG. 3.

The effect of adjusting the occupancy limit is to increase the granularity of the congestion control system to take into account traffic priority and transmission type. It is therefore proposed to add the transmission type of the affected user equipment in the occupancy limit of the channel to better handle the different transmission types in the congestion control procedure. For certain transmission types, the adjustment of the occupancy limit may be referred to as a "sum" (bones) of the respective values added to the occupancy limit.

Figure 4 shows a flow diagram of an aspect of a distributed congestion control system implementing the principles described above. The transmitting station has data with priority N for transmission. Instep 400, the UE senses (and calculates) a current channel busy value. The estimated channel busy rate at the transmitting station determines the choice and selection (choice and selection) of transmission parameters. The parameters include hybrid automatic repeat request related parameters and time-frequency resource amount. A default channel busy rate value of priority or a default parameter may be used when an estimate of the channel busy rate is not yet available. The selected transmission parameters, in particular the time-frequency resource candidates, enable the occupancy of the channel to be calculated at the transmitting station UE. Therefore, instep 401, the transmitting station calculates the channel occupancy of the priority N.

Instep 402, the UE determines a corresponding value of the channel occupancy limit, which is a starting value adjusted based on the priority and traffic type (traffic type). Instep 403, the UE determines the transmission type (unicast, multicast or broadcast) and insteps 404 and 405 adjusts the occupancy limit appropriately by using the relevant "added value" for the multicast or broadcast transmission. Subsequently, instep 406, the UE compares the calculated occupancy to the adjusted occupancy limit and, if possible, continues to transmit in step 407, or instep 408, reduces the occupancy (e.g., cancels the transmission) as needed. The UE continues to use the distributed congestion control algorithm in subsequent transmissions.

In the above description, the corresponding values of the channel occupancy limits for multicast and broadcast transmissions have increased. In another approach, this may be used in conjunction with or separate from adjusting the channel occupancy limit for unicast transmissions.

Another approach is to take into account the transmission type and traffic priority when calculating the QoS priority of the transmission (e.g., ProSe PPPP in LTE V2X system, where PPPP denotes the near field communication packet priority).

Table 1 below shows an example of QoS priority mapping to traffic priority and transmission type such that broadcast transmissions are prioritized over multicast transmissions and multicast transmissions are prioritized over unicast transmissions. Similarly, all transmission types of higher traffic priority are preferred over all transmission types of lower traffic priority.

TABLE 1

The mapping may also be extended to achieve group size differentiation based on multicast propagation, for example as shown in table 2 below.

TABLE 2

The specific mapping configurations of tables 1 and 2 are merely illustrative of the mechanism for mapping the transmission type and traffic priority to the quality of service priority.

The transmission QoS priority may be required in the bypass control information SCI, but the resources normally used for transmitting the bypass control information are scarce. Thus, the mapping can be optimized to reduce the required overhead. The example encodings of tables 1 and 2 enable only the most significant bits to be sent to the receiver, thereby reducing the size.

The result of these mappings is QoS_prio(unicast,prio N)<QoS_prio(K1-members groupcast,prio N)<QoS_prio(K2-members groupcast,prio N)<QoS_prio(broadcast,prio N)<QoS_prio(unicast,prio N-1), wherein K1<K2，QoS_prioIndicating a quality of service priority.

In another approach to transmission type in a distributed congestion control system, multicast congestion control may be assigned a longer response time than unicast congestion control, so that unicast transmissions are dropped before multicast transmissions. Variable response times may be achieved by using different measurement windows for broadcast, multicast and unicast transmissions, or increasing the delay before the UE reduces the channel occupancy for broadcast and/or multicast transmissions. This may be summarized as the UE using a delay to coincide with the occupancy limit before affecting the traffic: delay (broadcast) > delay (multicast) > delay (unicast). However, this approach may increase the delay of congestion control, especially if multicast transmission is dominant.

The different methods described above may be used in appropriate combination.

For reliable and fair operation, all UEs in the relevant area must share a common view of the operations and parameters of distributed congestion control. However, the parameters may need to be adjusted for different situations. Thus, semi-static configuration, e.g. through radio resource control signaling, may be an appropriate mechanism to configure a distributed congestion control system. More dynamic configuration may also be achieved through messaging using downlink control messages (DCI).

As described above, various configurations may be used according to circumstances. For example, whether the size of the group is a factor in adjusting the occupancy limit. For example, in the case where the size of the group is unknown, such as for a connectionless group, a fixed adjustment of all multicast transmissions may be most appropriate. The adjustment value may be specified in a configuration such as radio resource control. The values used to adjust the channel occupancy limit and other configuration aspects may be explicit values (explicit values), or an index to a list of predefined configurations and values (e.g., a 3-bit integer is required if there are no more than 8 available configurations).

The adjustment of the occupancy limit for multicast may depend on the size of the group, which is known to the transmitting station, e.g. the group size in the connection-oriented group (SA 2). A tuning table related to the group size may be provided or two parameters may be used. These parameters may be referred to as CRbonus _ group _ step and CRbonus _ group _ max and are used according to the following equations:

CRbonus＝min(K*CRbonus_groupcast_step,CRbonus_groupcast_max)

for broadcast transmissions, a fixed value for adjusting the occupancy limit of the channel may be specified, since the number of possible recipients cannot be known.

The parameters and operation of multicast transmission may be specified in a relevant standard, such as TS 38.211/TS 38.213. Example parameters that may be specified in the standard include:

● enables: yes/no

● broadcast

Channel occupancy value added broadcast (CRbonus broadcast)

● multicast

Type O: fixed, group-based size

Range of: channel occupancy value added _ multicast _ max (CRbonus _ groupcast _ max)

Step size: channel occupancy value added _ multicast _ step (CRbonus _ groupcast _ step)

O channel occupancy value _ multicast _ fixed value (CRbonus _ groupcast _ fixed)

By using radio resource control messaging parameters, for example, these parameters may be added to the Information Element (IE) of SL-CBR-CommonTxConfigList in the 38.331 protocol standard, which carries the channel occupancy limit or any equivalent information element defined by the NR V2X system.

Addition in the equivalent information elements of SL-CBR-PSSCH-TxConfig (within SL-CBR-CommonTxConfigList) or NR, for example:

Cr-Limit-Bonus-Broadcast INTEGER (INTEGER) (0:1000)

Cr-Limit-Bonus-GroupcastFixedINTEGER(0:1000)

Cr-Limit-Bonus-GroupcastMaxINTEGER(0:1000)

Cr-Limit-Bonus-GroupcastStepINTEGER(0:1000)

Cr-Limit-Bonus-Broadcast INTEGER(0:1000)

Although not shown in detail, any device or apparatus forming part of a network may include at least a processor, a memory unit, and a communication interface, where the processor unit, the memory unit, and the communication interface are configured to perform the methods of any aspect of the present invention. Further options and selections are described below.

Embodiments of the present invention, and in particular the signal processing functions of the gNB and UE, may be implemented using computer systems or architectures known to those skilled in the relevant art. The computer system used is, for example, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc.), mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment. The computer system may include one or more processors, which may be implemented using a general-purpose or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control module.

The computer system may also include a main memory, such as a Random Access Memory (RAM) or other dynamic memory, for storing information and instructions to be executed by the processor. Such main memory may also be used for storing temporary variables or other intermediate information during execution of instructions by the processor. Also, the computer system may include a Read Only Memory (ROM) or other static storage device for storing static information and instructions for the processor.

The computer system may also include an information storage system that may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a Compact Disk (CD) or Digital Video Drive (DVD), a read or write drive (R or RW), or other removable or fixed media drive. The storage media may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by a media drive. The storage media may include a computer-readable storage medium having stored therein particular computer software or data.

In other embodiments, the information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computer system. Such components may include, for example, a removable storage unit and an interface, such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to the computer system.

The computer system may also include a communications interface. Such a communication interface may allow software and data to be transferred between the computer system and external devices. Examples of a communication interface may include a modem, a network interface (e.g., an ethernet or other NIC card), a communication port (e.g., a Universal Serial Bus (USB) port), a PCMCIA slot and card, etc. Software and data transferred via the communication interface are in the form of signals which may be electronic, electromagnetic and optical or other signals capable of being received by the communication interface medium.

In this document, the terms "computer program product," "computer-readable medium," and the like may generally refer to a tangible medium, such as a memory, a storage device, or a storage unit. These and other forms of computer-readable media may store one or more instructions that are used by a processor, including a computer system, to cause the processor to perform specified operations. Such instructions 45, generally referred to as "computer program code" (which may be categorized in the form of computer programs or other categories), when executed, enable the computer system to perform the functions of embodiments of the present invention. Note that the code may directly cause the processor to perform specified operations, be compiled to perform such operations, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to perform such operations.

The non-transitory computer readable medium may include at least one of the group consisting of: hard disks, CD-ROMs, optical storage devices, magnetic storage devices, read-only memories, programmable read-only memories, erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), and flash memories. In embodiments where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into the computer system using, for example, a removable storage drive. The control module (in this example, software instructions or executable computer program code), when executed by a processor in a computer system, causes the processor to perform the functions of the invention as described herein.

Furthermore, the inventive concept may be applied to any circuit that performs a signal processing function within a network element. It is contemplated that, for example, semiconductor manufacturers may employ the inventive concept in the design of stand-alone devices, such as microcontrollers of Digital Signal Processors (DSPs), or Application Specific Integrated Circuits (ASICs), and/or any other sub-system elements.

It will be appreciated that, for clarity, the above description describes embodiments of the invention with reference to a single processing logic. The inventive concept may, however, equally be implemented by means of a plurality of different functional units and processors to provide the signal processing functions. Thus, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented (at least in part) when computer software is run on one or more data processors and/or digital signal processors or configurable modular components such as FPGA devices.

Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Furthermore, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Furthermore, the inclusion of a feature in one category of claims does not imply a limitation to this category but rather indicates that the feature is equally applicable to other claim categories as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. Furthermore, singular references do not exclude a plurality. Thus, references to "a", "an", "first", "second", etc. do not preclude a plurality.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term "comprising" or "comprises" does not exclude the presence of other elements.

Claims (18)

1. A method of distributed congestion control in a cellular communication system, the method being performed at a transmitting station of the cellular communication system and comprising the steps of:

calculating an indication of a transmission channel state available to the transmitting station;

calculating the channel utilization rate required by the transmitting station for transmitting data;

calculating a channel utilization rate limit value according to the state indication of the transmission channel and the flow type of the transmission data;

comparing the required channel utilization to a channel utilization limit; and

if the required channel utilization does not exceed the channel utilization limit, the data is transmitted.

2. The method of claim 1,

the traffic types include unicast traffic, multicast traffic, and broadcast traffic.

3. The method according to claim 1 or 2,

the channel utilization limits for the multicast transmission type and the broadcast transmission type are higher than the channel utilization limit for the unicast transmission type.

4. The method according to any of the preceding claims,

the channel utilization limit for the broadcast transmission type is higher than the channel utilization limit for the multicast transmission type.

5. The method according to any of the preceding claims,

the channel utilization limit for multicast communications is dependent on the size of the group.

6. The method according to any of the preceding claims,

the status indication of the transmission channel is the channel busy rate.

7. The method according to any of the preceding claims,

the required channel utilization and channel utilization limit is the channel occupancy.

8. The method according to any of the preceding claims,

the calculating a channel utilization limit comprises: adjusting the starting value, the adjusting being based on at least one of a traffic type of the transmission data and a priority of the transmission data.

9. The method of claim 8,

the step of adjusting the start value is based on the service quality priority and the traffic content priority of the traffic type.

10. The method of claim 9,

the traffic content priority constitutes the most significant bits of the quality of service priority and the traffic type constitutes the least significant bits of the quality of service priority.

11. The method according to any of the preceding claims,

if the required channel utilization exceeds the channel utilization limit, no data is sent.

12. The method according to any one of claims 1 to 10,

if the required channel utilization rate exceeds the channel utilization rate limit, the transmission parameters of the data are adjusted to reduce the required channel utilization rate to be not more than the channel utilization rate limit, and the data are sent by the adjusted transmission parameters.

13. A method of distributed congestion control in a cellular communication system, the method being performed at a transmitting station of the cellular communication system and comprising the steps of:

limiting access of the transmitting station to the transmission resource by the transmission limiting parameter; and

and adjusting the transmission limiting parameters according to the flow type of the data to be transmitted.

14. The method of claim 13,

the traffic types include unicast traffic, multicast traffic, and broadcast traffic.

15. The method according to claim 13 or 14,

the adjustment parameter is dependent on the traffic content priority.

16. A method of distributed congestion control in a cellular communication system, the method being performed at a transmitting station of the cellular communication system and comprising the steps of:

mapping the transmitted quality of service priority to a traffic priority and a transmission type to prioritize broadcast and multicast transmissions over unicast transmissions; and

multicast transmissions of a particular priority are less affected than unicast transmissions of the same priority.

17. The method according to any of the preceding claims,

the transmitting station is a user equipment.

18. The method according to any of the preceding claims,

the transmitting station is a base station.

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