WO2025021288A1 - Rate splitting multiple access based wireless communication with enhanced reliability - Google Patents

Abstract

The present disclosure relates to a transmitting method, a receiving method, a transmitting device and a receiving device and the corresponding programs. For example, a method is provided for transmitting data of a plurality of users, the method comprising: mapping a data unit of each user of the plurality of users onto wireless resources; extracting, for each user of the plurality of users, a data unit portion from the data unit of said user; generating a common data unit by combining the data unit portions of all respective users of the plurality of users; and mapping the common data unit onto wireless resources. The receiver receives the signals form the wireless resources and demaps the user data unit correspondingly.

Description

Rate Splitting Multiple Access based Wireless Communication with Enhanced Reliability

The present disclosure relates generally to wireless communication, and in particular to a rate splitting based transmission and reception as well as to the corresponding devices.

BACKGROUND

There have been several multiple access approaches applies and/or studied for wireless communications so far. Among them are an orthogonal multiple access (OMA), physical layer multicasting, space division multiple access (SDMA), and non-orthogonal multiple access (NOMA). An example of OMA is the Orthogonal Frequency Division Multiple Access (OFDMA) used in 4^th generation (4G) of cellular communications (Long Term Evolution, LTE) as well as in IEEE 802.11 (WiFi) standard family. The SDMA may be based on linear precoding such as the one presently used in 5th generation (5G) of cellular systems (New Radio, NR). NOMA may be based on linearly precoded superposition coding with a successive interference cancellation (SIC).

Recently, Rate Splitting Multiple Access (RSMA) has been studied. It is a multiple access scheme that enables a user messages to be split into common and private parts, after which the private parts are independently encoded into private streams while the common parts are jointly encoded into a common stream. The streams may then be precoded, superposed, and transmitted from a multi-antenna transmitter. On the receiver side, SIC is applied at each user receiving device to enable sequential decoding of the common streams and the private stream. Receiving devices then reconstruct the original messages by extracting the respective common part from the decoded common stream and combining it with the decoded private stream.

The RSMA has been considered as a strong and versatile multiple access technique in particular for downlink multi-antenna networks. RSMA may be seen as superior to SDMA and NOMA in some aspects. For example, SDMA works well when the user channels are not aligned. On the other hand, NOMA may be suited for aligned users. RSMA may work for both scenarios. Moreover, SDMA and NOMA do not work well under imperfect channel state information at the transmitter (CSIT), whereas RSMA is inherently robust to imperfect CSIT. Moreover, RSMA has a flexibility of adapting to the interference level instead of operating in two extremes of partially decoding the interference and partially treating it as a noise as in NOMA and SDMA, respectively.

Thus, RSMA may be suitable for employment in communication systems such as cellular systems (e.g. 4G, 5G, or further generations) or wireless local area networks (WLANs) or even for narrowband (NB) Internet of Things (loT) applications. It may be desirable to further improve RSMA.

SUMMARY

Methods and apparatuses are described herein for facilitating transmission and reception of wireless signals using a specific RSMA based on channel state information (CSI) which may enhance the reliability of the overall network while maintaining low latency.

The invention is defined by the independent claims. Some exemplary implementations are provided by the dependent claims.

For example, a transmitting method is provided for transmitting data of a plurality of users, comprising mapping a data unit of each user of the plurality of users onto wireless resources; extracting, for each user of the plurality of users, a data unit portion from the data unit of said user; generating a common data unit by combining the data unit portions of all respective users of the plurality of users; and mapping the common data unit onto wireless resources.

For example, a method is provided for receiving data of a receiving user, the method comprising: extracting, from wireless resources, a common data unit including data of a plurality of users including said receiving user; separating, from the common data unit, a data unit portion of the receiving user; extracting a data unit of the receiving user from wireless resources; and combining the data unit of the receiving user with the data unit portion of the receiving user.

For example, a method is provided for receiving data of a plurality of users, the method comprising: demapping a common data unit from wireless resources; extracting, from the common data unit, a common data unit for a current user out of the plurality of users; demultiplexing a private data unit portion of the current user from wireless resources; and combining, for the current user, the common data unit potion and the private data unit into a user data unit.

These and other features and characteristics of the presently disclosed subject matter, as well as the methods of operation and functions of the related elements of structures and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the disclosed subject matter. As used in the specification and the claims, the singular form of “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

BRIEF DESCRIPTION OF DRAWINGS

An understanding of the nature and advantages of various embodiments may be realized by reference to the following figures.

FIG. 1 is a block diagram illustrating a communication system with a transmitter and a receiver.

FIG. 2 is a block diagram illustrating a communication system architecture using infrastructure and involving communication between a base station and a user equipment.

FIG. 3 is a block diagram illustrating a communication system with one base station communicating with four user equipments in downlink direction.

FIG. 4 is a block diagram illustrating exemplary parts of a communication system processing chain at a data source and at a data destination.

FIG. 5 is a block diagram illustrating an exemplary RSMA implementation in a transmitter and receiver side.

FIG. 6 is a flow diagram illustrating a method for transmitting signals according to a modified RSMA.

FIG. 7 is a flow diagram illustrating a method for receiving signals according to a modified RSMA.

FIG. 8 is a block diagram illustrating an exemplary transmitter for transmitting signals according to a modified RSMA. FIG. 9 is a block diagram illustrating an exemplary receiver for receiving signals according to a modified RSMA.

FIG. 10 is a block diagram illustrating an exemplary transmitting apparatus including its structural features.

FIG. 11 is a block diagram illustrating an exemplary implementation of a memory of the transmitting apparatus of Fig. 10.

FIG. 12 is a block diagram illustrating an exemplary receiving apparatus including its structural features.

FIG. 13 is a block diagram illustrating an exemplary implementation of a memory of the receiving apparatus of Fig. 12.

Like reference numbers and symbols in the various figures indicate like elements, in accordance with certain example implementations.

DETAILED DESCRIPTION

For purposes of the description hereinafter, the terms “end,” “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” “lateral,” “longitudinal,” and derivatives thereof shall relate to the disclosed subject matter as it is oriented in the drawing figures. However, it is to be understood that the disclosed subject matter may assume various alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments or aspects of the disclosed subject matter. Hence, specific dimensions and other physical characteristics related to the embodiments or aspects disclosed herein are not to be considered as limiting unless otherwise indicated.

No aspect, component, element, structure, act, step, function, instruction, and/or the like used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more” and “at least one.” Furthermore, as used herein, the term “set” is intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and/or the like) and may be used interchangeably with “one or more” or “at least one.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based at least partially on” unless explicitly stated otherwise.

Communication system

Fig. 1 illustrates exemplary components of a communication system CS in which Tx represents a transmitter and Rx represents a receiver. The transmitter Tx is capable of transmitting a signal to the receiver Rx over an interface Intf. The interface Intf may be, for instance, a wireless interface. The interface may be specified by means of resources, which can be used for the transmission and reception by the transmitter Tx and the receiver Rx. Such resources may be defined in one or more (or all) of the time domain, frequency domain, code domain, and space domain. It is noted that in general, the “transmitter” and “receiver” may be also both integrated in the same device. In other words, the devices Tx and Rx in Fig. 1 may respectively also include the functionality of the Rx and Tx.

The present disclosure is not limited to any particular transmitter Tx, receiver Rx and/or interface Intf implementation. However, it may be applied readily to some existing communication systems as well as to the extensions of such systems, or to new communication systems. Exemplary existing communication systems may be, for instance the 5G New Radio (NR) in its current or future releases, and/or the IEEE 802.11 based systems such as the recently studied IEEE 802.11 be or the like.

Fig. 2 shows an exemplary wireless communication system such as an IEEE 802.11 based system or a 3GPP system such as 4G/5G or the like employing infrastructure. Such system includes a base station BS and a user equipment UE. The BS can be an access point (AP) of the IEEE 802.11 based system or a NodeB of the 3GPP system, such as an eNB of the 4G (LTE) or gNB of the 5G (NR) or the like. The UE may be any device such as mobile phone, laptop or tablet with the access to the wireless system, or even loT machine-type devices or the like. The term UE is used mainly in the context of the 3GPP standards. However, in this disclosure, this term is also used for general user equipment in any system such as e.g. a STA in the IEEE 802.11 based systems. The present disclosure is not limited to any particular implementation of the BS and the UE. As illustrated in Fig. 2, the communication between the BS and the UE may include downlink (DL) and uplink (UL). The DL communication is from the BS to the UE. Accordingly, in this case, the BS corresponds to the transmitter Tx of Fig. 1 and the UE corresponds to the receiver Rx of Fig. 1. The UL communication is from the UE to the BS. The present disclosure is not limited to the infrastructure based communication and may be employed also in device to device communications (e.g. between two UEs or ST As), at sidelink.

Fig. 2 illustrates a communication system on the example of one BS and one UE. However, in general, one BS may communicate with a plurality of UEs in uplink and/or in downlink and possibly also with further BSs or other network infrastructure elements. Fig. 3 illustrates a specific example, in which the BS communicates in downlink (DL) with four UEs, UE1 to UE4.

A more detailed, yet still a simplified block diagram of a digital communication system is depicted in Fig. 4. Blocks 110-140 belong to a transmitter side and may be implemented by the transmitter Tx of Fig. 1. Blocks 160-190 belong to a receiver side and may be implemented by the receiver Rx of Fig. 1. The transmitter and the receiver communicate with each other via a channel 150, which may add to the signal transmitted by the transmitter some noise. Information source 110 provides source data to be communicated to the receiving side. This may be raw data such as sensor data that may be e.g. AM audio signal, a video signal, image signal, text, measurement value(s) or the like. The source data may be compressed by the source encoder 120. The source encoder 120 may perform compression of the source data, such as lossy or lossless compression. The possibly compressed data are then passed to the channel encoder 130 that may perform various techniques such as FEC and ARQ or the like which facilitate robust transmission over the noisy channel 150. The channel coded data may then be modulated in a modulator 140 and transmitted over the channel 150, e.g. via one or more antennas. It is noted that the information source and the source encoder are typically not part of a communication system such as wireless communication interface. They are usually performed on the application layer and passed to the communication interface for transmission.

Correspondingly, the receiver side includes a demodulator 160 that demodulates the received signal (received e.g. over one or more antennas) and a channel decoder 170 which applies FEC decoding and/or implements receiver-side ARQ protocol and/or possibly other techniques. The source decoder 180 then de-compresses the source data, which are then used at the destination 190, e.g. displayed, used in further processing, played via loudspeaker, or the like.

The present disclosure mainly relates to the channel coder 130 and channel decoder 170.

Channel coding 130 is performed on data, that are typically referred to as information data (or information bits if the data is coded in units of bits rather than symbols), in such a way as to mitigate the negative effects of noise and interference incurred in the communications channel 150. This is achieved by FEC by adding redundancy, where some extra bits are included into the data to be transmitted in addition to the information bits for future error correction or error detection 170 at the receiver side. The capability of the demodulator 160 to restore the transmitted signals may be hampered by different channel factors including noise, interference, Doppler shift, multipath fading, etc. These factors result in demodulation errors and may hinder reliable communication. The purpose of a channel encoder 130 is, therefore, to facilitate a way to combat these errors caused by unfavorable channel conditions.

RSMA is one of promising candidates for sixth generation (6G) of communication systems and beyond networks to achieve a universal, flexible, robust, higher spectral-efficiency, and higher energy efficiency communication. One of the concerns in RSMA-based wireless communication networks is reliability. Several solutions have been proposed in the literature to cope with this issue, including short packet transmission or some specific Hybrid ARQ (HARQ) schemes. However, short packet transmission is mainly suitable for low-data rate applications. On the other hand, integration of HARQ with RSMA is not as straightforward as in other multiple access systems because of the message splitting and combing for each user in the network. It may also lead to an increase in latency in the network.

Numerous applications anticipated in 6G and beyond cannot handle large latency in order to achieve the reliability level that is targeted; for example non-terrestrial networks (NTNs), grant- free (GF), and ultra-reliable low latency communication (URLLC). In the case of NTNs, the distance between the satellite and the ground node is exceptionally large, making the use of retransmission techniques such as HARQ impractical, as this would further increase the latency. Similarly, grant-free access scheduling methods do not use a feedback path, so any error that occurs cannot be addressed through retransmission protocols, which may result in significantly impacting reliability of system. Moreover, URLLC networks are delay sensitive and cannot tolerate large delays.

Embodiments of the present disclosure aim at addressing the above-mentioned issues and achieving a high reliability while providing low latency. In particular, the embodiments provide an approach for enhancing the reliability of a multi-carrier multi-user RSMA-based wireless network. This is based on exploiting the inherent structure of RSMA such that a private streams contain the data of the respective users, whereas the common stream contains the data of those subcarriers of the private streams that experience bad channel gains (e.g. deep fade channel). Accordingly, on the receiver side, the reliability of the data carried in the bad subcarriers may be improved by increasing the diversity.

The conventional RSMA enables user messages to be splitted into common and private parts, after which the private parts are independently encoded into private streams while the common parts are jointly encoded into common stream. The streams are then linearly precoded and superimposed on the top of each other and transmitted from the multi-antenna transmitter. On the receiver side, SIC is applied at each user to enable sequential decoding of the common streams and the intended private stream. Receivers then reconstruct the original messages by extracting the intended common part from the decoded common message and combining it with the decoded private message.

RSMA Conventional System Model

For exemplary purposes, a multiple input multiple output (MIMO) single-cell downlink network is considered, with one base station to serve K users using RSMA as shown in Fig.1 .

In an RSMA system 500, a transmitter side which may be a base station comprises a scheduler 505 that schedules for example K messages for respective K users, K being an integer larger than 1 . A message D_k is a message for the Mh user, k running from 1 to K. In Fig. 5, K=2 and a message Di is for user 1 whereas a message D₂ is for user 2. The message D_k of the th user is split, by a message splitter 510 into a common part D_C]k and a private part D_p,_k. After that, the common parts of all users {D_c,i , . . ., D_C]k} are combined by a combiner 520 into a combined message D_c. In Fig. 5, the common parts Dd and D_C2 of the first and the second user are combined. The combined message D_c is then encoded, by an encoder 530 into the common stream s_c.

The private message parts {D_p,i , . . ., D_p,_k} are respectively encoded into private streams {s_pi, . . ., s_pk}, as shown in Fig. 5. In the example of Fig. 5, the private message parts D_pi and D_p2 of respective first and second user are encoded by the same encoder 530 into the streams s_pi and s_p2. Then, common and private data streams may be denoted together as s = [s_c, s_pi, . . ., s_pk]^T e QK+I (■■-]-» representing transposing operation), and are linearly precoded, by the linear precoder 540, before transmission and using the precoder P = [p_c, pi, . . ., PK], where p_c, p_k G C^Nt are the precoders of the common stream s_c and private streams s_pi to s_pK, respectively. We denote the power of the common stream s_c as P_c = HpdL. Therefore, the transmitted signal of the th user can be given as

where pk is the transmit power of private stream, s_Pk, for th user. The linearly precoded signal is then transmitted over a channel 550 by multiple antennas; in Fig. 5 two antennas 545a and 545b are illustrated. User 1 and user 2 are illustrated in Fig. 5 as having respectively one antenna 555_1 and 555_2. However, in general, the users may also have more than one antennas. A receiver of User 1 is illustrated in detail. A receiver of User 2 may have a similar structure and is not further illustrated in Fig. 5.

The received signal at th user consists of four parts as shown below:

where h_k e c^NtX1 is the channel gain from the base station (BS) to Mh user. In this model it is assumed to be perfectly known at the BS, it may be known for instance from the feedback the users may send to the BS or based on another estimation technique. n_k is the additive white Gaussian noise (AWGN) at th user, having a zero-mean and a variance o_k² and it is represented as n_k ~ JT(O, o^-2).

The received signal at User 1 consists of four parts as the above equation implies; common part, s_c, has typically higher power compared with other parts, private part, s_pi , has typically more power compared with the remaining parts, the multi-user interference part, s_pj, has typically more power compared with the noise part and this part is considered as noise in the detection process, and the last part is the noise, n₁. The common stream s_c is decoded first in a decoder 560 and then a splitter 580 splits the decoded portion common part D_c to extract the portion D_ci of the common part directed to User 1. In order to decode the private stream s_pi, successive interference cancellation (SIC) 565 is applied between the received signal, Y_{l t} and D_c to remove the larger interference (of the common part) on the private part, and the result is decoded in a decoder 570, thereby obtaining decoded private message part D_pi. The decoded message part D_pi is then combined with the portion D_ci of the common part directed to User 1 to obtain the decoded message Di for User 1 . Note that the interference from the other private users (in this example it is User 2 and in particular signal y₂ of User 2) is considered as a noise. It is noted that Fig. 5 illustrates a simplified basic RSMA System model (transmitter and receiver) 500. The above system model 500 can be scalable to more than two user cases, the two-user assumption is just for explanation. Moreover, there may be further components of the processing chain including modulation or the like.

RSMA with enhanced resilience

According to an embodiment, in order to improve resilience, the common part for a user k includes data carried within the private message part in resources that are experiencing bad channel state.

In particular, a method and apparatuses are provided for transmitting data of a plurality (e.g. K) of users. Such transmission is, for instance, transmission over a wireless channel in the downlink direction such as transmission from a BS to a UE or from an access point (AP) to a station (STA). However, the present invention is not strictly limited to such deployment and may also involve transmission over sidelink or even in uplink in cases a UE/STA would send data to more base station. When referring to “a plurality”, what is meant is two or more.

An exemplary method 600 is shown in Fig. 6. The method comprises a step of mapping 610 a data unit of each user k of the plurality K of users onto wireless resources. Here the term “data unit” corresponds to the term “message” used with reference to Fig. 5. For example the data unit may comprise binary data carrying payload or control information for a user. The present disclosure is not limited to any particular data unit format. It may carry (represent) modulation symbols, e.g. complex symbols or the like. The method further comprises a step of extracting 620, for each user k of the plurality K of users, a data unit portion from the data unit of said user. Which data unit portion is extracted may be given by a predefined rule. Moreover, the method comprises a step of generating 630 a common data unit by combining the data unit portions of all respective users of the plurality of users. The combining may be, for instance, a concatenation. It is noted that a sequential concatenation is only an example and, as is discussed below, other sorting based approaches may be used that include some interleaving, shuffling, scrambling, or the like. Then, the method comprises a step of mapping 640 the common data unit onto wireless resources. It is noted that steps 630 and 640 may be implemented as mapping the K data unit portions according to a predetermined order onto the resources.

Correspondingly to the data transmitting method 600, Fig. 7 illustrates a receiving method 700. In particular, the method 700 for receiving data of a receiving user comprises extracting 710, from wireless resources, a common data unit including data of a plurality of users including said receiving user and separating 720, from the common data unit, a data unit portion of the receiving user. The receiving user herein is the user on whose device the receiving method 700 is executed. The term user does not necessarily involve a human user. For example, the data may be directed to a machine, e.g. control data or requests for loT devices or general machine type communication. For example, the data may be for a base station or a relay or the like. The method 700 further comprises extracting 730 a data unit of the receiving user from wireless resources and combining 740 the data unit of the receiving user with the data unit portion of the receiving user. Which data unit portion is separated from the common data unit may be given by the predefined rule. The predefined rule should be the same at the transmitter and the receiver in order to maintain their operations compatible and to ensure correct parsing at the receiver.

An exemplary implementation of an apparatus that performs the above mentioned transmitting method 600 is shown in Fig. 8. In the exemplary system model 800, there are two scheduled users. The system 800 (transmitting device) includes a scheduler 810 for performing scheduling. In this example, the scheduler 810 schedules two messages Di and D₂ for transmission to the respective two users. Both messages Di and D₂ are then channel encoded by the encoder 820. The encoder 820 may also include modulation, i.e. constellation mapping of bit tuples onto modulation symbols. The constellation mapping may be mapping of bit tuples onto the complex modulation symbols based on constellations such as Quadrature Amplitude Modulation (QAM) of some predetermined order. In other words, the method comprises a step of obtaining the data unit (t and D₂) of the user (user 1 and user 2 respectively) by forward error encoding of the respective uncoded user message (Di and D₂). The uncoded user message may have any format (bits, symbols, etc) or content (payload or control, directed to a human or a machine, etc). For example, the user message may be data from a higher layer or a data from the higher layer after some preceding processing steps (scrambling, interleaving, or the like).

The encoded data units (5^ and 5^) are then passed to a splitter 830. The extracting 620 of the data unit portion for a user includes determining of the data unit portion according to channel conditions of the wireless resources onto which said data unit (private message part) of the user was mapped. In particular, the splitter 830 obtains the data units of all users and their corresponding channel state information. Moreover, the splitter may have, from the scheduler 810, information on which data units are to be mapped onto which wireless resources. The splitter 830 designs the private (based on user data units) and common streams (based on data unit parts of the users) such that the private steams contain the whole data unit of individual users while common stream contains the data that will experience bad subcarriers from all users. By doing so, an implicit diversity of selective data may be achieved that can improve and enhance the reliability and reduce the latency in the network (e.g. by not invoking HARQ at all or not so frequently as without this approach).

In other words, the mapping 610 of the data unit (of one user) onto wireless resources includes mapping onto subcarriers of time-frequency resources. The determining 620 of the data unit portion for the user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers onto which the data unit (of said one user) is mapped. Quality may be measured in terms of bit error rate, signal to noise ration or any other measure. The quality measurement may be provided from a receiver of each user to the transmitter 800 for instance via feedback 895. For example, the feedback may be a channel state information (CSI) such as that provided by 4G or 5G & or WiFi standards. However, it is noted that the present disclosure is not strictly limited to the predefined rule based on the lowest quality. For example, (in addition or alternatively to the channel quality criterion mentioned above) the predefined rule may be based on the priority or quality of service (QoS) requirements of the user data unit. Depending on a priority associated with the user data or based on the QoS of the user data, the number of bits for each user may be determined, which will be mapped onto the common part. For instance, user data with a higher priority will have larger amount of data in the common part than user data with a lower priority. The data unit portions D_ci , Dc2, etc. may be selected pseudo-randomly from the respective data units or according to a predetermined pattern known to the transmitter and the receiver. For example, Di = Dd + Dpi and D2 = D_C2 + D_P2 with “+” in these two equations meaning concatenation.

After that, the combiner 840 combines 630 the common parts of all users (D_c = Dd + D_C2) into data 850 and sends them to Inverse Fast Fourier Transform (IFFT) block 870 while private parts (D_pi, D_p2) 861 and 862 are sent to IFFT block 871 and 872 without combing. After passing through the IFFT block 870, 871 , and, 872 the data (850, 861 , 862) is converted to time domain. It is then sent to the precoder 880 and passed through the channel 890. Thus, the mapping of the private data units D_pi, D_p2 onto wireless resources includes precoding 880 and/or the mapping the common data unit D_c onto wireless resources includes precoding 880. The mapping may include superposition, e.g. spatial multiplexing or space-time coding or the like. The mapping may, following the precoding, further comprise digital to analog conversion, up-conversion, filtering, and/or amplification or the like (digital/analog front-end operations). In a conventional system model, the splitter 830 and combiner 840 may be designed for bit-level in concatenated form where the target of using the common stream 850 is managing the multiuser interference in the network. However, in the embodiments disclosed herein, the splitter 830 is designed on (modulation) symbol level, advantageously considering e.g. the channel state information. Thus, using the common stream may help enhancing reliability and reducing latency. It is noted that implementations without applying modulation (constellation mapping) are also conceivable.

In an exemplary implementation for a multi-carrier (OFDM) multiuser RSMA system, the data bits for each user are encoded and mapped into N (modulation) symbols (e.g. complex symbols), where these symbols are assumed to be in the frequency domain (mapped onto subcarriers). The N symbols of each user will then pass through a channel dependent-splitter. The splitter 830 split the data points into two groups, based on channel frequency response that represents the channel state information. The two groups may be a group with good channel conditions and a group with bad channel conditions. For example, this approach sorts the channel coefficients in descending order and considers the first N/K as good data subcarriers (strong channel state information) and the remaining as bad data subcarriers (weak channel state information) where K is the total number of users in the network that need scheduling. It is noted that the value “N/K” is only an exemplary value of a general predefined threshold on number of symbols.

Afterwards, the splitter 830 will output two private portions D_pi , D_p2 and two common portions D_ci , D_C2. In the private portions D_pi , D_p2, the splitter will put the whole data that correspond to the respective individual users. On the other hand, in the common portion, the data of those subcarriers that will experience bad (poor) channel gain are multiplexed (thus repeating the data that will likely experience errors). It is then likely that the group of “good” subcarriers will be decoded more reliably than the group of “bad” subcarriers. Accordingly, with such RSMA, the overall reliability of the system may be increased. Consequently, since the transmitter can estimate ahead of time the portion of the OFDM symbol that cannot be decoded successfully at the receiver, the transmitter is able to send only the bad part of the OFDM symbol in the common part along with the whole OFDM symbol in the private stream. After the splitter 830, the combiner 840 concatenates the common portions into the common stream 850 and both streams, common 850 and private 861 , 862 are precoded 880 and handled as in conventional RSMA.

It is noted that the splitter 830 may perform two operations. The first one is sorting the data of the subcarriers based on the CSI that the transmitter experience, into bad and good subcarriers. The second operation is to take the data of the bad subcarriers and insert them in the common stream. Correspondingly, at the receiver side, there are two splitters 940 and 970; one for splitting 940 the data of the corresponding user from other users, and one for re-sorting 970 (and thus also referred to as re-sorter) the private data to determine which are the bad subcarriers in the private stream from which the data was repeated in the common stream.

In this way, the two copies of the data (portion of the private stream predicted to have bad quality, and the repetition of this portion) can be determined and combined.

At the receiver side, after the detection of the common stream 850, the data that corresponds to bad subcarriers of each individual user is stored in a buffer and can be later combined (on a symbol level basis) with the data corresponding to bad subcarriers in the private streams 861 , 862 e.g. by maximum ratio combining (MRC). The combined portions may be then concatenated with the private data portions.

The transmitter system model is shown in Fig. 8. The system model can be scalable to more than two users, e.g. K users; the two-user assumption is just a simplification for the sake of explanation. The following steps are performed by the transmitter of Fig. 8:

The message D_k of th user is passed through the channel encoder to encode the data bits and obtain N symbols as an output. Then, N symbols are then passed through the splitter 830 that is dependent on frequency selective channel. As can be seen in Fig. 8, the knowledge of the channel may be provided to the transmitter and in particular to the splitter 830 based on the feedback 895 as indicated in the figure by a dashed arrow. The arrow is illustrated to come from the channel 890. In practice, this may be implemented by various ways. For example, a CSI may be transmitted from the receiver of the data to the transmitter, or in case the transmitter and receiver operate in similar frequency bands, the transmitter may measure the received frequencies, or the like.

Based on sorting of channel coefficients, the splitter 830 divides the data of each user into two portions. In a private stream D_pk, the entire data of a particular th user are mapped, and in the common portion D_ck, the data of those subcarriers are mapped that face the bad channel.

The combiner 840 combines the common portions from all users user into the common stream D_c and transfers it to the IFFT block 870. On the other hand, private streams D_pk are sent to IFFT blocks 861 , 862 without combining for the purpose of conversion to time domain. The output of IFFT blocks (D^ and D_pk) are linearly precoded 880, superimposed on the top of each other resulting in a message Z, and sent over the channel 890. An exemplary receiver is illustrated in Fig. 9. Channel quality may be measured 995 and provided to a splitter 970. The entire message Z is received by the first user. As the common D_c' has higher power and is broadcasted, it is received by all the users and is first decoded. Fig. 9 shows a receiver of one user (referred to e.g. as a first user). The receiver has an antenna 920 over which the signals are received. For the first user, the data corresponding to bad subcarriers D_C1 is demapped (by applying the Fourier transformation 930), split from the common parts of other users in splitter 940, and stored in a buffer (not shown in the figure). The SIC is applied to demap the private stream

and private streams of all other users are treated as noise (the re-sorter 970 re-sorts the private data subcarriers of the corresponding (here first) user into two parts based on the CSI, namely into the good and bad subcarriers). It is noted that the splitter 940 is based on the concatenation approach and the re-sorter 970 is based on the CSI to re-sort the subcarriers in the private stream to identify the “good” and “bad” subcarriers, i.e. to identify subcarriers of which the private data are repeated in the common stream (and to distinguish them from the subcarriers of which the private data is not repeated in the common stream). The demapping includes the SIC 950, and the Fourier transformation 960 in this example. After that, the data corresponding to poor subcarriers in the private stream is merged in the Maximum Ration Combining (MRC) 980 with the data previously stored in the buffer. It is noted that MRC is only an exemplary combining mechanism and other kinds of combining may be used. After this combining the original message

is obtained for the first user. Every user in the network may have a similar receiver and decoder their data accordingly.

Two sorting-based approaches (applying concatenation and interleaving, respectively) are discussed, used so that the receiver knows how many and which sub-carriers in the common stream are for the corresponding user. On the other hand, these approaches show how the transmitter is distributed to the subcarriers between the users in the common stream specifically considering the CSI. It is noted that the above-mentioned mechanisms for dividing the subcarriers into high-quality (good) and low-quality (bad) subcarriers was only exemplary. Below, there are further-exemplary mechanisms, although the present disclosure is not limited to any particular of them.

For example, subcarriers allocated to each user are separately (for each user) divided into good and bad subcarriers based on a predetermined percentage. For example 10% of user’s subcarriers that have the worst quality among the subcarriers of the same user are determined as bad and the corresponding data mapped on these bad subcarriers is repeated in the common portion. The predetermined percentage (here 10% as an example) is same for all (currently scheduled) users.

The predetermined percentage can vary among the users. The variation may be given, for instance by the application the data pertain to and/or to the QoS required by the application and/or by the priority of the data of the users. As mentioned in the above description, the percentage may depend on available subcarriers and on the number of users, because the users will share the common portion.

In summary, provided is a splitting approach to the rate dedicated to common portion and to the private portions may be configurable (e.g. by a base station or by other network entities or by a radio resource control (RRC) protocol or the like).

Another example is based on the interleaving approach.

In some exemplary implementations, it may not be necessary to assign the subcarriers I data according to predefined percentages mentioned above. Alternatively, or in addition, each user may have a specific sequence based on a specific goal such as securing its common data and this can be another (additional or alternative with regard to percentage) degree of freedom for the BS and UEs to allocate the subcarriers. Where the size of sequence and the way of generating it are matter. And this sequence generation could be based on QoS, Security, complexity, etc.

Also, it could be based on the threshold where the user can determine it based on its requirements (such as key performance indicators, KPIs).

For example, in case CSI is used as a KPI, a scale of the CSI between 1 and 10 may be defined. For instance, for a first user, CSI below 5, may indicate a bad channel. For a second user, CSI below 7, it is considered a bad channel. The threshold 5 or seven may be user specific and determined based on the user application QoS or based on other parameters. Based on the threshold, the number of subcarriers of the common portion can be different from one user to another. It is also depending on the user's requirements and what the UE wants based on the key performance indicators (KPIs), especially the reliability.

User requirements may be given by the desired channel reliability (e.g. given by target error rate). For example, users with higher desired reliability may be assigned a larger number of subcarriers in the common portion (common stream) than the users with lower desired reliability. In a simplified example, let us have two users and the number of the subcarriers for common stream being 64. If one user requires higher reliability, the BS can allocate a larger number of subcarriers to this user. While the other user can achieve its required reliability with the remaining subcarriers. This approach may be a part of adaptive scheduling of the users based on their requirements. By doing so, the network can achieve an improved user fairness based on the users' demands which will make the resource allocation adaptive.

Correspondingly to the methods described above, apparatuses are provided that are capable of performing those methods. Fig. 10 illustrates an exemplary implementation of a transmitting apparatus 300. Such transmitting apparatus may be, for instance, a base station or an access point or any communication apparatus that transmits data to a plurality of users at the same time (e.g. within the same time instance or within a same frame or the like).

The transmitting apparatus 300 for transmitting data of a plurality of users comprises processing circuitry 320 and a wireless transmitter 330. The wireless transmitter may be a wireless transceiver and may have the functionality of both - transmitter and receiver.

The wireless transmitter 330 may be configured by the processing circuitry 320 to perform the transmission. The transmitter 330 may include one or more antennas with their corresponding analog front circuitry, possibly also a digital-to-analog converter (DAC) and/or one or more filters and/or power amplifiers. The analog front circuitry may include one or more power amplifier stages, gain control circuitry, up-converter, one or more filters, phase control, local oscillator and/or the like.

The processing circuitry 320 is configured to perform any of the above mentioned methods. The processing circuitry 320 may be configured, for instance by a program code that may be stored in a memory 310. The program may include one or more functional modules.

For example, the processing circuitry 320 is configured to map a data unit of each user of the plurality of users onto wireless resources. This may performed by a private portion mapper 360 shown in Fig. 11. Moreover, the processing circuitry 320 is configured to extract, for each user of the plurality of users, a data unit portion from the data unit of said user; generate a common data unit by combining the data unit portions of all respective users of the plurality of users; and map the common data unit onto wireless resources. These steps may be performed by a functional module denoted as a common portion mapper 380. The wireless transmitter 330 is configured to transmit the mapped data unit and mapped common data unit in the wireless resources.

Y1 For example, the processing circuitry 320 may comprise one or more processors that, in operation, execute the program code and. However, the processing circuitry is not necessarily limited to processor(s) and it may include a further or alternative electronic circuitry to perform the above described methods. The transmitting apparatus 300 may further comprise a user interface 340 that may be a programmable interface or a graphical user interface that may be used for configuring the transmitting apparatus.

Correspondingly to the transmitter, a receiver 400 is provided which may have structural features as shown in Fig. 12. In particular, the receiver (an apparatus for receiving data of a receiving user) comprises a wireless receiver (or in general transceiver) 430 configured to receive signal in wireless resources, and processing circuitry 420. This structure is similar as the structure of the transmitting device 300. However, the processing circuitry 420 is configured differently.

The receiving device (apparatus) 400 may also further include a memory 410. The memory 410 may be used to store program code that ma configure the processing circuitry 420 to perform any of the reception related methods described above. In particular, the processing circuitry 420 may be configured to: extract, from the wireless resources, a common data unit including data of a plurality of users including said receiving user; and separate, from the common data unit, a data unit portion of the receiving user. These functions may be performed by the common portion demapper 470 (functional module stored in the memory 410) as shown in Fig. 14. The processing circuitry 420 may be further configured to extract a data unit of the receiving user from the wireless resources, which may be performed by a private portion demapper 460. Finally, the processing circuitry 420 may be further configured to combine the data unit of the receiving user with the data unit portion of the receiving user. This may be performed by the combiner module 480.

The receiving apparatus 400 may further comprise a user interface 440 that may be a programmable interface or a graphical user interface that may be used for configuring the transmitting apparatus. The receiving apparatus may be a user equipment or any kind of wireless station (STA) or wireless communication device. enhance reliability and reduce latency. First, to apply the RSMA approach, the base station applies splitting and combing methods to perform the transmission. In the literature, the splitting block merely splits the message into two parts (in concatenated form). In the present disclosure, a splitting approach is provided based on the channel for each user, to improve the reliability of the transmission. This may facilitate physical layer operation without HARQ in some implementations. If no retransmission method is used, the latency of the overall system would generally be low (reduced). Applying such an approach enhances the reliability of the user data at the same time of transmission without waiting for feedback from the user about data's status. The present disclosure is thus suitable for NTNs and Grant-Free (GF) approaches since no feedback is required from the users about the data; as well as for URLLC where low latency is the main requirement.

The present disclosure implicitly provides security despite sending private data in common portion, because the data in common will not have any immediate meaning to the eavesdropper. Since the data in the common portion is selected based on the corresponding user channel, the eavesdropper (internal or external) would not know which parts of message are used in the common portion. Thus, a desired QoS may be achieved based on the user requirements. If a particular user has high requirement of reliability, a higher percentage of their data may be inserted into the common portion.

In well-known retransmission if the packet is not received correctly at the receiver whole packet is sent again that exhausts more resources. On the other hand, according to the present disclosure, only the data that may be affected is sent (repeated) in the common portion making it more efficient which can be called a feedback-free selective retransmission. The diversity of the data is achieved simultaneously by way of transmitting repetitions of the data that will most likely experience errors: Accordingly, HARQ or ARQ do not need to be used at all or they may be used, but their latency may be improved (as there will likely be less retransmissions necessary).

This present disclosure may be used in any wireless network that uses rate splitting as a multiaccess approach to serving multi-users in the network such as: Joint Radar and communication (JRC) applications, Massive MIMO-Networks, Ultra-reliable and low-latency communications (URLLC), millimeter-wave (mmWave) communication, unmanned aerial vehicles-aided communications (UAV), Physical layer security (PLS), Massive machine-type communication (mMTC), Cognitive radio networks (CRN), Device to device communication (D2D), Grant-free access networks (GF), or Non-terrestrial networks (NTN).

It is noted that some exemplary implementations of the methods for transmitting and receiving include features that have been described above with reference to the respective transmitting and receiving devices (e.g. steps performed by the processing circuitry and/or the transceiver.

Implementations in software and hardware It is noted that although embodiments and examples of the present disclosure were provided in terms of a method above, the corresponding devices providing the functionality described by the methods are also provided. Moreover, it is noted that any of the steps described above may be included as code instructions in a program, which may be executed by one or more processors.

The methodologies described herein may be implemented by various means depending upon the application. For example, these methodologies may be implemented in hardware, operation system, firmware, software, or any combination of two or all of them. For a hardware implementation, any processing circuitry may be used, which may include one or more processors. For example, the hardware may include one or more of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, any electronic devices, or other electronic circuitry units or elements designed to perform the functions described above.

If implemented as program code, the functions performed by the transmitting apparatus (device) may be stored as one or more instructions or code on a non-transitory computer readable storage medium. The computer-readable media includes physical computer storage media, which may be any available medium that can be accessed by the computer, or, in general by the processing circuitry. Such computer-readable media may comprise RAM, ROM, EEPROM, optical disk storage, magnetic disk storage, semiconductor storage, or other storage devices. Some particular and non-limiting examples include compact disc (CD), CD-ROM, laser disc, optical disc, digital versatile disc (DVD), Blu-ray (BD) disc or the like. Combinations of different storage media are also possible - in other words, distributed and heterogeneous storage may be employed.

The above examples are not to limit the present disclosure. There are many modifications and configurations, which may be used in addition or alternatively. This present disclosure can be used in any kind of device that is receiving signals over a wireless channel. The embodiments and exemplary implementations mentioned above show some non-limiting examples. It is understood that various modifications may be made without departing from the claimed subject matter. For example, modifications may be made to adapt the examples to new systems and scenarios without departing from the central concept described herein.

Selected embodiments and examples In particular, according to a first aspect, a transmitting method is provided, comprising: mapping a data unit of each user of the plurality of users onto wireless resources; extracting, for each user of the plurality of users, a data unit portion from the data unit of said user; generating a common data unit by combining the data unit portions of all respective users of the plurality of users; and mapping the common data unit onto wireless resources.

According to a second aspect, in addition to the first aspect, the extracting of the data unit portion for a user includes determining of the data unit portion according to channel conditions of the wireless resources onto which said data unit of the user was mapped.

According to a third aspect, in addition to the second aspect, the mapping of the data unit onto wireless resources includes mapping onto subcarriers of time-frequency resources, and the determining of the data unit portion for the user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers onto which the data unit is mapped.

According to a fourth aspect, in addition to any of the first to third aspect, the method comprises a step of obtaining the data unit of the user by forward error encoding of a user message.

According to a fifth aspect, in addition to any of the first to fourth aspect, the mapping of the data unit onto wireless resources includes precoding; and/or the mapping the common data unit onto wireless resources includes precoding.

According to a sixth aspect, a receiving method is provided comprising: extracting, from wireless resources, a common data unit including data of a plurality of users including said receiving user; separating, from the common data unit, a data unit portion of the receiving user; extracting a data unit of the receiving user from wireless resources; and combining the data unit of the receiving user with the data unit portion of the receiving user.

According to a seventh aspect, a method is provided for receiving data of a plurality of users, the method comprises demapping a common data unit from wireless resources; extracting, from the common data unit, a common data unit for a current user out of the plurality of users; demultiplexing a private data unit portion of the current user from wireless resources; and combining, for the current user, the common data unit potion and the private data unit into a user data unit.

According to an eighth aspect, in addition to the seventh aspect, the combing is a maximum ratio combining. According to a ninth aspect, in addition to the seventh or eighth aspect, the extracting of the common data unit portion for the current user includes determining of the common data unit portion according to channel conditions of the wireless resources onto which said data unit of the user was mapped.

According to a tenth aspect, in addition the ninth aspect, the mapping of the data unit onto wireless resources includes mapping onto subcarriers of time-frequency resources, and the determining of the common data unit portion for the current user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers onto which the user data unit is mapped.

According to an eleventh aspect, in addition to any of the seventh to tenth aspect, the method further comprising a step of forward error decoding of the user data unit into a user message.

According to a twelfth aspect, in addition to any of the seventh to tenth aspect, the demapping of the private data unit from wireless resources includes successive interference cancellation, SIC.

According to a thirteenth aspect, a program is provided that is stored on a computer readable, non-transitory medium and comprising code instructions which, when executed on one or more processors, cause the one or more processors to perform the steps of the method according to any of first to twelfth aspect.

According to a fourteenth aspect, an apparatus is provided for transmitting data of a plurality of users, the apparatus comprising: processing circuitry configured to: map a data unit of each user of the plurality of users onto wireless resources; extract, for each user of the plurality of users ,a data unit portion from the data unit of said user; generate a common data unit by combining the data unit portions of all respective users of the plurality of users; and map the common data unit onto wireless resources, and a transceiver for transmitting the mapped data unit and mapped common data unit.

According to a fifteenth aspect, in addition to the fourteenth aspect, the extracting of the data unit portion for a user includes determining of the data unit portion according to channel conditions of the wireless resources onto which said data unit of the user was mapped.

According to a sixteenth aspect, in addition to the fifteenth aspect, the demapping of the data unit from the wireless resources includes demapping from subcarriers of time-frequency resources, and the determining of the data unit portion for the user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers from which the data unit is demapped.

According to a seventeenth aspect, in addition to any of the fourteenth to sixteenth aspect, the processing circuitry is further configured to obtain the data unit of the user by forward error encoding of a user message.

According to an eighteenth aspect, in addition to any of the fourteenth to seventeenth aspect, the mapping of the data unit onto wireless resources includes precoding; and/or the mapping the common data unit onto wireless resources includes precoding.

According to a nineteenth aspect, an apparatus is provided for receiving data of a receiving user, the apparatus comprising: a transceiver configured to receive signal in wireless resources; and processing circuitry configured to: extract, from the wireless resources, a common data unit including data of a plurality of users including said receiving user; separate, from the common data unit, a data unit portion of the receiving user; extract a data unit of the receiving user from the wireless resources; and combine the data unit of the receiving user with the data unit portion of the receiving user.

According to a twentieth aspect, in addition to the nineteenth aspect, the combing is a maximum ratio combining.

According to a twenty-first aspect, in addition to any of the nineteenth to twentieth aspect, the extracting of the data unit portion for the current user includes determining of the data unit portion according to channel conditions of the wireless resources onto which said data unit of the user was mapped.

According to a twenty-second aspect, in addition to the twenty-first aspect, the demapping of the data unit from the wireless resources includes demapping from subcarriers of time-frequency resources, and the determining of the common data unit portion for the current user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers from which the user data unit is demapped.

According to a twenty-third aspect, in addition to any of the nineteenth to twenty-second aspect, the processing circuitry is further configured to perform forward error decoding of the user data unit into a user message. According to a twenty-fourth aspect, in addition to any of the nineteenth to twenty-third aspect, the demapping of the private data unit from wireless resources includes successive interference cancellation, SIC.

According to a twenty-fifth aspect, an integrated circuit is provided that is or includes the processing circuitry mentioned above and an interface to the above mentioned transceiver (receiver and/or transmitter).

Claims

1 . A method for transmitting data of a plurality of users, the method comprising: mapping a data unit of each user of the plurality of users onto wireless resources; extracting, for each user of the plurality of users, a data unit portion from the data unit of said user; generating a common data unit by combining the data unit portions of all respective users of the plurality of users; and mapping the common data unit onto wireless resources.

2. The method according to claim 1 , wherein the extracting of the data unit portion for a user includes determining of the data unit portion according to channel conditions of the wireless resources onto which said data unit of the user was mapped.

3. The method according to claim 2, wherein the mapping of the data unit onto wireless resources includes mapping onto subcarriers of time-frequency resources, and the determining of the data unit portion for the user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers onto which the data unit is mapped.

4. The method according to any of claims 1 to 3, comprising a step of obtaining the data unit of the user by forward error encoding of a user message.

5. The method according to any of claims 1 to 4, wherein the mapping of the data unit onto wireless resources includes precoding; and/or the mapping the common data unit onto wireless resources includes precoding.

6. A method for receiving data of a receiving user, the method comprising: extracting, from wireless resources, a common data unit including data of a plurality of users including said receiving user; separating, from the common data unit, a data unit portion of the receiving user; extracting a data unit of the receiving user from wireless resources; combining the data unit of the receiving user with the data unit portion of the receiving user.

7. A method for receiving data of a plurality of users, the method comprising: demapping a common data unit from wireless resources; extracting, from the common data unit, a common data unit for a current user out of the plurality of users; demultiplexing a private data unit portion of the current user from wireless resources; combining, for the current user, the common data unit potion and the private data unit into a user data unit.

8. The method according to claim 7, wherein the combining is a maximum ratio combining.

9. The method according to claim 7 or 8, wherein the extracting of the common data unit portion for the current user includes determining of the common data unit portion according to channel conditions of the wireless resources onto which said data unit of the user was mapped.

10. The method according to claim 9, wherein the mapping of the data unit onto wireless resources includes mapping onto subcarriers of time-frequency resources, and the determining of the common data unit portion for the current user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers onto which the user data unit is mapped.

11 . The method according to any of claims 7 to 10, comprising a step of forward error decoding of the user data unit into a user message.

12. The method according to any of claims 7 to 11 , wherein the demapping of the private data unit from wireless resources includes successive interference cancellation, SIC.

13. A program stored on a computer readable, non-transitory medium and comprising code instructions which, when executed on one or more processors, cause the one or more processors to perform the steps of the method according to any of claims 1 to 12.

14. An apparatus for transmitting data of a plurality of users, the apparatus comprising: processing circuitry configured to:

- map a data unit of each user of the plurality of users onto wireless resources;

- extract, for each user of the plurality of users, a data unit portion from the data unit of said user; generate a common data unit by combining the data unit portions of all respective users of the plurality of users; and map the common data unit onto wireless resources; and a transceiver for transmitting the mapped data unit and mapped common data unit.

15. The apparatus according to claim 14, wherein the extracting of the data unit portion for a user includes determining of the data unit portion according to channel conditions of the wireless resources onto which said data unit of the user was mapped.

16. The apparatus according to claim 15, wherein the demapping of the data unit from the wireless resources includes demapping from subcarriers of time-frequency resources, and the determining of the data unit portion for the user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers from which the data unit is demapped.

17. The apparatus according to any of claims 14 to 16, wherein the processing circuitry is further configured to obtain the data unit of the user by forward error encoding of a user messsge.

18. The apparatus according to any of claims 14 to 17, wherein the mapping of the data unit onto wireless resources includes precoding; and/or the mapping the common data unit onto wireless resources includes precoding.

19. A apparatus for receiving data of a receiving user, the apparatus comprising: a transceiver configured to receive signal in wireless resources; and processing circuitry configured to:

- extract, from the wireless resources, a common data unit including data of a plurality of users including said receiving user;

- separate, from the common data unit, a data unit portion of the receiving user;

- extract a data unit of the receiving user from the wireless resources; and

- combine the data unit of the receiving user with the data unit portion of the receiving user.

20. The apparatus according to claim 19, wherein the combining is a maximum ratio combining.

21. The apparatus according to claim 19 or 20, wherein the extracting of the data unit portion for the current user includes determining of the data unit portion according to channel conditions of the wireless resources onto which said data unit of the user was mapped.

22. The apparatus according to claim 21 , wherein the demapping of the data unit from the wireless resources includes demapping from subcarriers of time-frequency resources, and the determining of the common data unit portion for the current user includes identifying of a predetermined number of subcarriers with a lowest quality among the subcarriers from which the user data unit is demapped.

23. The apparatus according to any of claims 19 to 22, wherein the processing circuitry is further configured to perform forward error decoding of the user data unit into a user message.

24. The apparatus according to any of claims 19 to 23, wherein the demapping of the private data unit from wireless resources includes successive interference cancellation, SIC.