Device and method for multiple access communications with selection of time-frequency resource elements based on payload bits

Abstract

The present disclosure relates to a transmitting device and a receiving device. The disclosure proposes a transmitting device that is configured to: obtain a payload, wherein the payload comprises a sequence of B bits, wherein B is a positive integer; extract m bits from the sequence of B bits, wherein m is a positive integer less than B; identify a user group index based on the extracted m bits, wherein the transmitting device is a user in a user group identified by the user group index; encode the sequence of B-m bits to obtain an encoded signal; assign a set of resource elements from T available time-frequency resource elements based on the identified user group index, wherein T is a positive integer; and transmit the encoded signal using the set of resource elements. This disclosure further proposes a corresponding receiving device.

Description

[0001] DEVICE AND METHOD FOR MULTIPLE ACCESS COMMUNICATIONS WITH SELECTION OF TIME-FREQUENCY RESOURCE ELEMENTS BASED ON PAYLOAD BITS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to the field of wireless communications, more specifically to a transceiver design for facilitating multiple access in environments characterized by massive Machine Type Communications (mMTC), including applications within the Internet of Things (loT) domain. The disclosure addresses the challenges inherent in scenarios where a high number of transmitters concurrently send messages to a singular multi-antenna receiver over frequency-selective channels, with an emphasis on improving the efficiency and reliability of such communications through novel modulation and signal processing techniques.

[0004] BACKGROUND

[0005] Wireless communication technologies have evolved to support a wide array of applications, ranging from personal communication devices to loT applications, which require the transmission of data from numerous devices over complex and often challenging environments. One critical aspect of this evolution is the development of efficient and reliable methods for multiple access communication, especially in scenarios characterized by a dense population of transmitting devices, such as in mMTC scenarios. These environments demand technologies capable of handling a significant number of simultaneous transmissions without compromising on the quality or reliability of the communication.

[0006] Grant-free access methods, where devices transmit data without a prior scheduling grant from the base station, are pivotal for reducing latency and overhead in mMTC. However, the random and simultaneous nature of transmissions in such scenarios exacerbates the challenges of multi-user interference and signal separation at the receiver, especially under the conditions of multipath frequency-selective channels common in wireless communications.

[0007] Tensor-based modulation (TBM) has emerged as a promising solution by encoding transmitted symbols as rank-one tensors, thereby enabling efficient user separation and signal demapping using tensor decomposition techniques. Despite its advantages, the performance of traditional TBM is limited in dynamic channel environments characterized by multipath propagation, leading to correlation that disrupt the rank-one tensor-structured uncorrelated signals and degrade the effectiveness of signal separation at the receiver.

[0008] Moreover, the existing TBM framework is predominantly designed with block-fading channel models in mind, which do not accurately capture the dynamics of multipath propagation. This mismatch between the assumed and actual channel models further exacerbates the problem, limiting the ability of TBM to provide a robust solution for grant-free massive random access in the context of mMTC and loT communications.

[0009] These limitations highlight a critical need for advancements in modulation schemes that can overcome the challenges posed by multipath frequency-selective channels, thereby ensuring efficient, reliable, and scalable wireless communications for a future dominated by loT and mMTC applications.

[0010] SUMMARY

[0011] In view of the above-discussed limitations, this disclosure aims to introduce an improved method and system for a transceiver design that enhances the robustness and efficiency of multiple access communications in mMTC and loT and similar scenarios. One objective is to provide methodologies and systems designed to extend the applicability and efficiency of TBM for grant- free massive random access. Another objective is to provide a robust modulation scheme that enhances the capacity, reliability, and spectral efficiency of mMTC systems.

[0012] These and other objectives are achieved by the solution of the present disclosure as provided in the enclosed independent claims. Advantageous implementations are further defined in the dependent claims.

[0013] A first aspect of the disclosure provides a transmitting device, which is configured to: obtain a payload, wherein the payload comprises a sequence of B bits, wherein B is a positive integer; extract m bits from the sequence of B bits, wherein m is a positive integer less than B; identify a user group index based on the extracted m bits, wherein the transmitting device is a user in a user group identified by the user group index; encode the sequence of B-m bits to obtain an encoded signal; assign a set of resource elements from T available time-frequency resource elements based on the identified user group index, wherein T is a positive integer; and transmit the encoded signal using the set of resource elements.

[0014] This disclosure proposes a transmitter side design for unsourced massive grant-free random access in the context of multipath frequency selective channels. The transmitting device takes as input a sequence of bits and as output the vector to be transmitted. The main point is labeling each message of a particular user using extracted m bits so that it can be identified as belonging to a certain group of users.

[0015] In an implementation form of the first aspect, the transmitting device is further configured to encode the sequence of B-m bits using a TBM encoder, to obtain the encoded signal.

[0016] In a particular example, the proposed transmitting device is based on TBM modulation.

[0017] In an implementation form of the first aspect, to encode the sequence of B-m bits using the TBM encoder, the transmitting device is further configured to encode the sequence of B-m bits using a forward error correction encoder to generate a sequence of coded bits; split the sequence of coded bits into a plurality of subsequences; modulate the plurality of subsequences to produce a plurality of encoded subsequences; and generate the encoded signal based on the plurality of encoded subsequences.

[0018] In an implementation form of the first aspect, the transmitting device is further configured to modulate each of the plurality of subsequences using a respective non-coherent constellation modulator to produce an encoded subsequence, wherein each encoded subsequence is a symbol vector.

[0019] In an implementation form of the first aspect, the transmitting device is further configured to generate the encoded signal by computing a Kronecker product of the plurality of symbol vectors.

[0020] In an implementation form of the first aspect, the transmitting device is further configured to map the encoded signal to the set of resource elements according to a mapping function and the user group index.

[0021] It may be understood that the mapping function takes the encoded signal as input and knowing that a user k is associated with a user group of index q, and maps each element of the encoded signal to a resource element in the time-frequency grid sketched for the user group.

[0022] In an implementation form of the first aspect, the set of resource elements assigned to a user group index comprises a set of contiguous frequency subcarriers. A second aspect of the disclosure provides a receiving device, which is configured to obtain a plurality of user group-specific signals from a received signal based on a plurality of user group indices, wherein each user group-specific signal is for a user group that is identified by a user group index; decompose each user group-specific signal into a plurality of user-specific signals, wherein each user-specific signal is for a respective user in the user group; decode each user-specific signal to obtain a decoded sequence; and generate a decoded payload for the respective user based on the decoded sequence and the user group index.

[0023] This disclosure further proposes a receiving device for estimating the transmitted sequences of bits based on received signals that were corrupted by a frequency-selective channel.

[0024] In an implementation form of the second aspect, the receiving device is further configured to decompose each user groupspecific signal into the plurality of user-specific signals using a multipath alternating least squares (MP-ALS) algorithm, wherein each decomposed user-specific signal comprises a plurality of subsequences.

[0025] An important aspect of the receiving device is the new tensor decomposition algorithm, referred to as MP-ALS for Multipath Alternating Least Squares. This algorithm is specifically engineered to address the challenges posed by severe multipath channels, meaning it is adept at handling situations involving highly correlated rank-one tensors.

[0026] In an implementation form of the second aspect, the MP-ALS algorithm is parameterized by an estimated channel delay spread and an estimated number of multipaths.

[0027] In an implementation form of the second aspect, to decode each user-specific signal, the receiving device is further configured to: estimate a user-specific phase offset based on the user-specific signal; perform phase offset correction on each subsequence of the plurality of subsequences based on the estimated user-specific phase offset; demap each phase offset corrected subsequence to obtain a plurality of demapped subsequences; merge the plurality of demapped subsequence to obtain a userspecific sequence; and decode the user-specific sequence and verify the integrity of the decoded user-specific sequence.

[0028] In an implementation form of the second aspect, the receiving device is further configured to generate a reconstructed signal based on the plurality of decoded user-specific sequences, for which the integrity is successfully checked; and perform interference cancellation iterations for the plurality of decoded user-specific sequences, for which the integrity is successfully checked, based on the reconstructed signal.

[0029] A Cyclic Redundancy Check may be performed to validate the integrity of the decoded data. An iterative processing through Successive Interference Cancellation (SIC) may also be performed to progressively decode and rebuild the signals for each user.

[0030] In an implementation form of the second aspect, the receiving device is further configured to determine a sequence of m bits based on the user group index; and combine the sequence of m bits with the decoded user-specific sequence to generate the decoded payload for each user.

[0031] The correctly decoded binary sequence is merged with the m bits previously used for user group identification, resulting in a decoded payload.

[0032] In an implementation form of the second aspect, the receiving device is further configured to obtain, for each user group, a user group-specific signal through a resource demapping so that the user group-specific signal corresponds to the received signal at a set of resource elements of that user group, wherein the set of resource elements is assigned to the user group at the transmitting device from T available time-frequency resource elements based on the user group index.

[0033] A third aspect of the disclosure provides a method performed by a transmitting device, the method comprises: obtaining a payload, wherein the payload comprises a sequence of B bits, wherein B is a positive integer; extracting m bits from the sequence of B bits, wherein m is a positive integer less than B; identifying a user group index for the user based on the extracted m bits, wherein the transmitting device is a user in a user group identified by the user group index; encoding the sequence of B-m bits to obtain an encoded signal; assigning a set of resource elements from T available time-frequency resource elements based on the identified user group index, wherein T is a positive integer; and transmitting the encoded signal using the set of resource elements.

[0034] In an implementation form of the third aspect, the method further comprises encoding the sequence of B-m bits using a TBM encoder, to obtain the encoded signal.

[0035] In an implementation form of the third aspect, the encoding of the sequence of B-m bits using the TBM encoder comprises: encoding the sequence of B-m bits using a forward error correction encoder to generate a sequence of coded bits; splitting the sequence of coded bits into a plurality of subsequences; modulating the plurality of subsequences to produce a plurality of encoded subsequences; generating the encoded signal based on the plurality of encoded subsequences.

[0036] Implementation forms of the method of the third aspect may correspond to the implementation forms of the transmitting device of the first aspect described above. The method of the third aspect and its implementation forms achieve the same advantages and effects as described above for the transmitting device of the first aspect and its implementation forms.

[0037] A fourth aspect of the disclosure provides a method performed by a receiving device, the method comprises obtaining a plurality of user group-specific signals from a received signal based on a plurality of user group indices, wherein each user groupspecific signal is for a user group of that is identified by a user group index; decomposing each user group-specific signal into a plurality of user-specific signals, wherein each user-specific signal is associated with a respective user in the user group; decoding each user-specific signal to obtain a decoded sequence; and generating a decoded payload for a respective user based on the decoded sequence and the user group index.

[0038] In an implementation form of the fourth aspect, the method further comprises decomposing each user group-specific signal into the plurality of user-specific signals using a multipath alternating least squares algorithm, wherein each decomposed userspecific signal comprises a plurality of subsequences.

[0039] In an implementation form of the fourth aspect, the decoding of each user-specific signal comprises: estimating a user-specific phase offset based on the user-specific signal; performing phase offset correction on each subsequence of the plurality of subsequences based on the estimated user-specific phase offset; demapping each phase offset corrected subsequence to obtain a plurality of demapped subsequences; merging the plurality of demapped subsequence to obtain a user-specific sequence; and decoding the user-specific sequence and verify the integrity of the decoded user-specific sequence.

[0040] Implementation forms of the method of the fourth aspect may correspond to the implementation forms of the receiving device of the second aspect described above. The method of the fourth aspect and its implementation forms achieve the same advantages and effects as described above for the receiving device of the second aspect and its implementation forms. A fifth aspect of the disclosure provides a computer program product comprising a program code for carrying out, when implemented on a processor, the method according to the third aspect and any implementation forms of the third aspect, or the fourth aspect and any implementation forms of the fourth aspect.

[0041] A sixth aspect of the disclosure provides a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out, the method according to the third aspect and any implementation forms of the third aspect, or the fourth aspect and any implementation forms of the fourth aspect.

[0042] It has to be noted that all devices, elements, units, and means described in the present application could be implemented in software or hardware elements or any kind of combination thereof. All steps that are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity that performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements or any kind of combination thereof.

[0043] BRIEF DESCRIPTION OF DRAWINGS

[0044] The above-described aspects and implementation forms of the present disclosure will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which:

[0045] FIG. 1 shows a transmitting device according to an embodiment of this disclosure;

[0046] FIG. 2 shows a structure of the multipath TBM encoder according to an embodiment of this disclosure;

[0047] FIG. 3 shows a block diagram of the state-of-the-art TBM encoder;

[0048] FIG. 4 shows a receiving device according to an embodiment of this disclosure;

[0049] FIG. 5 shows a structure of the multipath TBM decoder according to an embodiment of this disclosure;

[0050] FIG. 6 shows a block diagram of the state-of-the-art TBM decoder;

[0051] FIG. 7 shows an architecture of the multipath TBM transmitter for the kth user according to an embodiment of this disclosure;

[0052] FIG. 8 shows a general architecture of the user group mapper according to an embodiment of this disclosure;

[0053] FIG. 9 shows signal mapping according to an embodiment of this disclosure;

[0054] FIG. 10 shows an architecture of the multipath TBM receiver for the qth user block according to an embodiment of this disclosure;

[0055] FIG. 11 shows a method according to an embodiment of this disclosure; and FIG. 12 shows a method according to an embodiment of this disclosure

[0056] DETAILED DESCRIPTION OF EMBODIMENTS

[0057] Illustrative embodiments of a transmitting device, a receiving device, and corresponding methods are described in the following with reference to the figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.

[0058] Moreover, an embodiment or example may refer to other embodiments or examples. For example, any description including but not limited to terminology, element, process, explanation, and / or technical advantage mentioned in one embodiment or example may also apply to the other embodiments or examples.

[0059] FIG. 1 shows a transmitting device 100 according to an embodiment of the disclosure.

[0060] The transmitting device 100 may comprise processing circuitry (not shown) configured to perform, conduct, or initiate the various operations of the transmitting device 100 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. The transmitting device 100 may further comprise memory circuitry, which stores one or more instruction(s) that can be executed by the processor or by the processing circuitry, in particular under the control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the transmitting device 100 to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to one or more processors. The non-transitory memory may carry executable program code which, when executed by one or more processors, causes the transmitting device 100 to perform, conduct, or initiate the operations or methods described herein.

[0061] The transmitting device 100 is configured to obtain a payload 101, wherein the payload 101 comprises a sequence of B bits, wherein B is a positive integer; extract m bits 1011 from the sequence ofB bits 101, wherein m is a positive integer less than B; identify a user group index 1012 based on the extracted m bits 1011. Notably, the transmitting device 100 is a user in a user group identified by the user group index 1012. The transmitting device 100 is further configured to encode the sequence ofB- m bits 102 to obtain an encoded signal 103; assign a set of resource elements from T available time-frequency resource elements based on the identified user group index 1012 (indicated by the dashed arrow), wherein T is a positive integer; and transmit the encoded signal 103 using the set of resource elements.

[0062] The goal of the present disclosure is to solve both transmitter and receiver side design problems for unsourced massive grant- free random access in the context of multipath frequency selective channels. It may be understood that frequency-selective channels are the consequence of many propagation phenomena, e.g., received signal delay spread from multipath propagation (urban area and indoor environment), beam squint effect, and terahertz propagation. This embodiment proposes a design of a transmitter, which takes as input a sequence of B bits, and outputs the encoded signal.

[0063] In particular, this embodiment is based on the TBM signaling architecture. The transmitting device 100 may be further configured to encode the sequence of B-m bits 102 using a TBM encoder 104, to obtain the encoded signal 103. FIG. 2 depicts a general description of the designed encoder according to an embodiment of the disclosure. It can be seen that generating the transmitted signal for each user follows three main steps:

[0064] (i) from the binary message of B bits 101, extract m bits 1011 to identify the user group q, thereby allowing the application of the mapping function Jttq,

[0065] (ii) use the remaining B-m bits 102 as an input for a “TBM encoder” 104 using T' (T' < T) physical resources, i.e., the set of resource elements; and

[0066] (iii) map the signal issued by the TBM encoder 104 using the mapping function Mq and allocate the output vector of symbols to T physical resources, i.e., T available time-frequency resource elements.

[0067] The set of resource elements assigned to a user group index may comprise a set of contiguous frequency subcarriers. Examples of mapping M ‘ q will be discussed in the latter part of the application.

[0068] Notably, the “Splitter” block may be considered as a parameter or input a list of indices of the m bits that will be used for identifying the user group. An example of such a list of indicesis the indices of the first m bits of the payload 101. The complete list of potential indices is known in advance by both transmitters and receivers.

[0069] At the transmitter, it is important to note that labeling each message with the extracted m bits is a key process, ensuring that the message is categorized into a specific user group (“User group identification”). It may be worth mentioning that the term “user group” is not identified with the user index (denoted by k in FIG. 2) but with the extracted m bits of the payload of the user, for instance, its initial m bits.

[0070] It should be emphasized that while the initial m bits are presented as a basic implementation example, this concept is flexible and can be adapted to numerous other configurations. For instance, aside from extracting the initial m bits, or the last m bits, one could consider utilizing the middle m bits of the message, a random selection of m bits scattered throughout the message, or even a pattern-based selection of m bits that follows a predefined rule or sequence. This versatility in selecting m bits allows for a wide range of implementation strategies to suit different requirements and contexts.

[0071] After the user grouping, the transmitted signal sk, i.e., the encoded signal 103, is expressed as: where: skis the signal mapped over T resources for the user fc, sk' G CT' (T' < T) is the rank-1 tensor issued by the TBM encoder,

[0072] Mg is the user group mapping (to higher dimension) function, xi kE CTi( i = 1, the i th source symbols vector of the user fc , issued from a given non-coherent subconstellation. Note here that fl z= i Tt = T' .

[0073] Notably, the encoded signal 103 can consist of encoded symbols or various other types of symbols.

[0074] According to an embodiment of this disclosure, the transmitting device 100 may be further configured to map the encoded signal 103 to the set of resource elements according to a mapping function and the user group index 1012.

[0075] For ease of understanding of the application, TBM modulation is further explained here. The transmitted symbols encoded with a TBM modulation can be considered rank-one tensors. The receiver uses tensor decomposition to separate users, which allows convenient multi-user separation and single-user demapping. The limit of this scheme is that this signaling scheme is designed for the block-fading channel.

[0076] Notably, the TBM encoder 104 of the transmitting device 100 as shown in FIG. 2 may be the TBM encode shown in FIG. 3.

[0077] In a particular embodiment of this disclosure, to encode the sequence of B-m bits 102 using the TBM encoder 104, the transmitting device 100 may be further configured to encode the sequence of B-m bits 102 using an FEC encoder to generate a sequence of coded bits; split the sequence of coded bits into a plurality of subsequences; modulate the plurality of subsequences to produce a plurality of encoded subsequences; and generate the encoded signal 103 based on the plurality of encoded subsequences.

[0078] Possibly, the FEC encoder may comprise a bit interleaver and bit scrambler. Therefore, the encoding processing using the FEC encoder may also comprising bit interleaving and bit scrambling.

[0079] Optionally, the transmitting device 100 may be further configured to modulate each of the plurality of subsequences using a respective non-coherent constellation modulator to produce an encoded subsequence, wherein each encoded subsequence is a symbol vector.

[0080] Within the scope of this disclosure, the following notations are considered:

[0081] Kais the number of single-antenna active users, randomly active among a larger set of K users, transmitting a message of B bits over T physical resources, each active user transmits its signal characterized by a T-dimensional vector, denoted sfc, to a single receiver of N antennas over a frequency-selective channel of L paths, skis an OFDM-modulated signal, which is in fact a sequence of S OFDM symbols, each of them spread over F subcarriers, forming T = FS physical time-frequency resource elements allocated for the signal sk.

[0082] Optionally, the transmitting device 100 may be further configured to configured to generate the encoded signal 103 by computing a Kronecker product of the plurality of symbol vectors.

[0083] This disclosure further proposes a design of a receiver estimating the transmitted sequences of bits based on received signals that were corrupted by a frequency-selective channel. FIG. 4 shows a receiving device 400 according to an embodiment of the disclosure.

[0084] The receiving device 400 may comprise processing circuitry (not shown) configured to perform, conduct, or initiate the various operations of the receiving device 400 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. The receiving device 400 may further comprise memory circuitry, which stores one or more instruction(s) that can be executed by the processor or by the processing circuitry, in particular under the control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the receiving device 400 to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to one or more processors. The non-transitory memory may carry executable program code which, when executed by one or more processors, causes the receiving device 400 to perform, conduct, or initiate the operations or methods described herein.

[0085] The receiving device 400 is configured to obtain a plurality of user group-specific signals 402 from a received signal 401 based on a plurality of user group indices, wherein each user group-specific signal 402 is for a user group that is identified by a user group index 1012. The receiving device 400 is further configured to decompose each user group-specific signal 402 into a plurality of user-specific signals 403, wherein each user-specific signal 403 is for a respective user in the user group; decode each user-specific signal 403 to obtain a decoded sequence 404; and generate a decoded payload 101 for the respective user based on the decoded sequence 404 and the user group index 1012.

[0086] This embodiment proposes a design of the receiver estimating the transmitted sequences of bits based on received signals that were corrupted by a frequency-selective channel. More specifically, under a frequency-selective channel of L paths, the received signal, in the OFDM grid, y 6 C™ over the N antennas is expressed as: where:

[0087] ® denotes the Kronecker product, o denotes the Hadamard (element-wise) product, ske CTis the transmitted signal (rank-one tensor) of the user fc, (C denotes the set of complex numbers and its superscript is the dimension of the related vector / matrix)

[0088] Cki E CTis the steering vector (in the time domain), representing the delay introduced by the Ith path to the signal of the user fc, therefore this vector is a part of the channel model and cannot be controlled by the transmitter, Sk.i G CNis the channel gain, w E CTNis the noise.

[0089] FIG. 5 depicts the structure of the proposed receiving device 400. The decoding steps for each group of users are the same, and are summarized as the following:

[0090] (i) demapping the user group q, giving the received signals of the user group q,

[0091] (ii) unmix signals of the user group by performing a tensor-rank decomposition based on the designed MP-ALS algorithm.

[0092] According to an embodiment of the disclosure, the receiving device 400 may be further configured to obtain, for each user group, a user group-specific signal 402 through a resource demapping so that the user group-specific signal 402 corresponds to the received signal 401 at a set of resource elements of that user group, wherein the set of resource elements is assigned to the user group at the transmitting device 100 from T available time-frequency resource elements based on the user group index 1012.

[0093] On the receiver side, an important aspect is the new tensor decomposition algorithm, referred to as MP-ALS for Multipath Alternating Least Squares. This algorithm is specifically engineered to address the challenges posed by severe multipath channels, meaning it is adept at handling situations involving highly correlated rank-one tensors. For each user group q, of user indices set Uq(user indices sets are disjoint), estimating the transmitted signals amounts to solving optimization: where: yqis the demapped received signal, i.e., the received signals for the user group q, sk’ is the estimation of the transmitted signal sk’ , gkis the estimated channel,

[0094] L'qis the number of restricted paths at the receiver for the user group q,

[0095] Cj'i G CT' is the steering vector (in the time domain), representing the delay introduced by the / 'th path to the signal of the user k.

[0096] For ease of understanding of this embodiment, the structure of a state-of-art TBM decoder is depicted in FIG. 6. In particular, FIG. 6 shows a block diagram of the TBM decoder. It illustrates the steps involved in decoding a received signal that has been encoded using TBM.

[0097] The main components of the TBM receiver are as follows:

[0098] Kank- / <aTensor Decomposition ATS: This block represents the algorithm responsible for decomposing the incoming signal into tensors, which is the first step in separating the signals from different users.

[0099] Time Offset Correction: Each user's signal is corrected for any discrepancies in time alignment, ensuring synchronization.

[0100] Demapper (EER): Following correction, the signals undergo a demapping process that translates the received signals into log-likelihood ratios (LLRs), useful for the subsequent decoding process.

[0101] FEC Decoder: The FEC decoder attempts to correct errors in the signal to ensure accurate data retrieval.

[0102] CRC Check: A Cyclic Redundancy Check is performed to validate the integrity of the decoded data.

[0103] The diagram also shows iterative processing through SIC to progressively decode and rebuild the signals for each user, resulting in the final decoded payload for each user #k.

[0104] The receiving device 400 introduced in this disclosure incorporates the TBM encoder and adopts the newly proposed tensor decomposition algorithm (MP-ALS) algorithm, replacing the conventional Rank-KaTensor Decomposition ALS.

[0105] According to an embodiment of the disclosure, the receiving device 400 may be further configured to decompose each user group-specific signal 402 into the plurality of user-specific signals 403 using an MP-ALS algorithm, wherein each decomposed user-specific signal comprises a plurality of subsequences.

[0106] Optionally, the MP-ALS algorithm is parameterized by an estimated channel delay spread and an estimated number of multipaths.

[0107] According to an embodiment of the disclosure, to decode each user-specific signal 403, the receiving device 400 may be further configured to: estimate a user-specific phase offset based on the user-specific signal 403: perform phase offset correction on each subsequence of the plurality of subsequences based on the estimated user-specific phase offset; demap each phase offset corrected subsequence to obtain a plurality of demapped subsequences; merge the plurality of demapped subsequence to obtain a user-specific sequence; and decode the user-specific sequence and verify the integrity of the decoded user-specific sequence.

[0108] Optionally, the receiving device 400 may be further configured to generate a reconstructed signal based on the plurality of decoded user-specific sequences, for which the integrity is successfully checked; and perform interference cancellation iterations for the plurality of decoded user-specific sequences, for which the integrity is successfully checked, based on the reconstructed signal.

[0109] Notably, the receiving device 400 may be further configured to determine a sequence of m bits 1011 based on the user group index 1012; and combine the sequence of m bits 1011 with the decoded user-specific sequence 404 to generate the decoded payload 101 for each user.

[0110] FIG. 7 shows the detailed structure of the transmitting device 100 according to an embodiment of this disclosure. The embodiment depicted in FIG. 7 is based on the embodiments shown in FIG. 1 and FIG. 2.

[0111] Each user uses m = [log2(<?)] ([. ] denotes the ceiling function) bits of the payload to determine the user group mapping function of index q. This allocation allows a simple design of the receiver dealing independently for each group.

[0112] FIG. 8 depicts the general architecture of the mapping process, where the mapping function Mq is applied. FIG. 9 shows an illustration of mapping assuming 4 groups of users (i.e., Q = 4). As drawn in this example, the mapping functions Mq, having as input (knowing that the user k is associated with the user group of index q) and skas output, maps each element of the signal to a resource element in the time-frequency grid sketched for the user group q. Note that a resource element in the time-frequency grid can be allocated by multiple user groups.

[0113] FIG. 10 shows the architecture of the receiving device 400 according to an embodiment of the disclosure. The embodiment depicted in FIG. 10 is based on the embodiments shown in FIG. 4 and FIG. 5. In particular, FIG. 10 depicts a decoder structure for decoding the q-th group of users. The complete decoder performs this task for all user groups q = 1, ... , Q (as illustrated in FIG. 5).

[0114] The main decoding steps for the decoder of the q-th group of users are the following:

[0115] Step 1 - User group demapping:

[0116] Demapping signals of the corresponding user group, resulting in the received signal yq. i.e., the user group-specific signal 402.

[0117] Step 2 - Tensor rank decomposition:

[0118] The tensor rank decomposition block takes as fixed parameters: Tmax. theapproximated delay spread at the receiver,

[0119] L'q, the number of restricted paths at the receiver,

[0120] For each restricted path I' (I' = define the steering vector C('lin terms of Tmaxand L'q.

[0121] The tensor rank decomposition block estimates the signals xf k, the user-specific signal 403, by solving the following MP-ALS formulated problem:

[0122] Step 3 - Phase offset correction and LLR demapping:

[0123] On each signal xi k, perform a phase offset correction and then a Log-Likelihood Ratio (LLR) demodulation to recover the binary subsequence.

[0124] Step 4 - CRC check:

[0125] Merge the previously recovered d binary subsequences, giving one sequence of B’ bits. On the obtained binary sequence, perform an FEC decoding and then a CRC check.

[0126] Step 5 - Rebuilding signals:

[0127] Reconstruct the correctly decoded signals xf kto use them for the next SIC iteration.

[0128] Step 6 - Combiner:

[0129] Merge the correctly decoded binary sequence 404 with the m bits previously used for user group identification.

[0130] Notably, on the receiver side, the “Combiner” block should consider as a parameter or input the list of indices of the m bits used for identifying the user group, i.e., the same list used on the transmitter side.

[0131] The general context of this disclosure can be summarized as follows. A set (of random cardinality) of users (i.e., transmitters) transmit simultaneously a message (represented by a sequence of B bits), under highly frequency-selective channels. Each message is modulated into a sequence of T symbols mapped on T physical time-frequency resources and transmitted to a multiantenna receiver. This disclosure tackles the problem of transceiver design within the described context, modulation scheme, and transmission conditions.

[0132] FIG. 11 shows a method 1100 according to an embodiment of the disclosure. In a particular embodiment, the method 1100 is performed by the transmitting device 100 shown in one of FIG. 1 , FIG. 2, or FIG. 7. The method 1100 comprises a step 1101 of obtaining a payload 101, wherein the payload 101 comprises a sequence of B bits, wherein B is a positive integer; a step 1102 of extracting m bits 1011 from the sequence of B bits 101, wherein m is a positive integer less than B; a step 1103 of identifying a user group index 1012 for the user based on the extracted m bits 1011, wherein the transmitting device 100 is a user in a user group identified by the user group index 1012. The method 1100 further comprises a step 1104 of encoding the sequence of B-m bits 102 to obtain an encoded signal 103; a step 1105 of assigning a set of resource elements from T available time-frequency resource elements based on the identified user group index 1012, wherein T is a positive integer; and a step 1106 of transmitting the encoded signal 103 using the set of resource elements. Possibly, the encoded signal 103 is transmitted to a receiving device 400 shown in one of FIG. 4, FIG. 5, or FIG. 10. Optionally, a TBM encoder is used in the method 1100 for encoding of the sequence of B-m bits 102.

[0133] In particular, the encoding of the sequence of B-m bits using the TBM encoder comprises: encoding the sequence of B-m bits 102 using an FEC encoder to generate a sequence of coded bits; splitting the sequence of coded bits into a plurality of subsequences; modulating the plurality of subsequences to produce a plurality of encoded subsequences; generating the encoded signal based on the plurality of encoded subsequences.

[0134] Optionally, the method 1100 also comprises modulating each of the plurality of subsequences using a respective non-coherent constellation modulator to produce an encoded subsequence, wherein each encoded subsequence is a symbol vector.

[0135] Optionally, the method 1100 also comprises generating the encoded signal 103 by computing a Kronecker product of the plurality of symbol vectors.

[0136] Optionally, the method 1100 also comprises mapping the encoded signal 103 to the set of resource elements according to a mapping function and the user group index 1012.

[0137] Possibly, the set of resource elements assigned to a user group index comprises a set of contiguous frequency subcarriers.

[0138] FIG. 12 shows a method 1200 according to an embodiment of the disclosure. In a particular embodiment, the method 1200 is performed by the receiving device 400 shown in one of FIG. 4, FIG. 5, or FIG. 10. The method 1200 comprises a step 1201 of obtaining a plurality of user group-specific signals 402 from a received signal 401 based on a plurality of user group indices, wherein each user group-specific signal 402 is for a user group of that is identified by a user group index 1012; a step 1202 of decomposing each user group-specific signal 402 into a plurality of user-specific signals 403, wherein each user-specific signal 403 is associated with a respective user in the user group; a step 1203 of decoding each user-specific signal 403 to obtain a decoded sequence 404; and a step 1204 of generating a decoded payload 101 for a respective user based on the decoded sequence 404 and the user group index 1012.

[0139] Optionally, in the method 1200, a MP-ALS algorithm is used for decomposing each user group-specific signal 402 into the plurality of user-specific signals 403, wherein each decomposed user-specific signal comprises a plurality of subsequences.

[0140] Possbily, the MP-ALS algorithm is parameterized by an estimated channel delay spread and an estimated number of multipaths.

[0141] Optionally, the step 1203 of decoding each user-specific signal 403 comprises: estimating a user-specific phase offset based on the user-specific signal 403; performing phase offset correction on each subsequence of the plurality of subsequences based on the estimated user-specific phase offset; demapping each phase offset corrected subsequence to obtain a plurality of demapped subsequences; merging the plurality of demapped subsequence to obtain a user-specific sequence; and decoding the userspecific sequence and verify the integrity of the decoded user-specific sequence.

[0142] Optionally, the method 1200 further comprises generating a reconstructed signal based on the plurality of decoded user-specific sequences, for which the integrity is successfully checked; and performing interference cancellation iterations for the plurality of decoded user-specific sequences, for which the integrity is successfully checked, based on the reconstructed signal.

[0143] Optionally, the method 1200 further comprises determining a sequence of m bits 1011 based on the user group index 1012; and combining the sequence of m bits 1011 with the decoded user-specific sequence 404 to generate the decoded pay load 101 for each user. Optionally, the method 1200 further comprises obtaining, for each user group, a user group-specific signal 402 through a resource demapping so that the user group-specific signal 402 corresponds to the received signal 401 at a set of resource elements of that user group, wherein the set of resource elements is assigned to the user group at the transmitting device 100 from T available time-frequency resource elements based on the user group index 1012.

[0144] To summarize, embodiments of the present application propose at the transmitter side user groups grouping and resource assignment. This allows supporting a higher number of users than using the full physical resources for all users and attenuating the effect of the channel’s frequency selectivity as well, resulting in better transmission performance for a higher number of users within the context of frequency-selective (and highly selective) channels. Embodiments of the present application propose at the receiver side the MP-ALS algorithm for user signal separation at the receiver. This algorithm allows separating TBM- coded signals for highly correlated rank-one tensors, resulting in better decoding performance under frequency-selective (and highly selective) channels.

[0145] The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed embodiments of the disclosure, from the studies of the drawings, this disclosure, and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutually different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.

[0146] Furthermore, any method according to embodiments of the disclosure may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer-readable medium of a computer program product. The computer-readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

[0147] Moreover, it is realized by the skilled person that embodiments of the transmitting device 100 or the receiving device 400 comprise the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements, and functions are processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, trellis-coded modulation (TCM) encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc., which are suitably arranged together for performing the solution.

[0148] Especially, the processors) of the transmitting device 100 or the receiving device 400 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some, or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Claims

CLAIMS1. A transmitting device (100), configured to: obtain a payload (101), wherein the payload (101) comprises a sequence of B bits, wherein B is a positive integer; extract m bits (1011) from the sequence ofB bits (101), wherein m is a positive integer less than B; identify a user group index (1012) based on the extracted m bits (1011), wherein the transmitting device (100) is a user in a user group identified by the user group index (1012); encode the sequence of B minus m bits (102) to obtain an encoded signal (103); assign a set of resource elements from T available time-frequency resource elements based on the identified user group index (1012), wherein T is a positive integer; and transmit the encoded signal (103) using the set of resource elements.

2. The transmitting device (100) according to claim 1, configured to: encode the sequence of B minus m bits (1012) using a tensor-based modulation, TBM, encoder (104), to obtain the encoded signal (102).

3. The transmitting device (100) according to claim 2, to encode the sequence of B minus m bits (102) using the TBM encoder (104), being configured to: encode the sequence of B minus m bits (102) using a forward error correction encoder to generate a sequence of coded bits; split the sequence of coded bits into a plurality of subsequences; modulate the plurality of subsequences to produce a plurality of encoded subsequences; and generate the encoded signal (103) based on the plurality of encoded subsequences.

4. The transmitting device (100) according to claim 3, configured to: modulate each of the plurality of subsequences using a respective non-coherent constellation modulator to produce an encoded subsequence, wherein each encoded subsequence is a symbol vector.

5. The transmitting device (100) according to claim 4, configured to: generate the encoded signal (103) by computing a Kronecker product of the plurality of symbol vectors.

6. The transmitting device (100) according to one of the claim 1 to 5, configured to: map the encoded signal (103) to the set of resource elements according to a mapping function and the user group index (1012).

7. The transmitting device (100) according to one of the claims 1 to 6, wherein the set of resource elements assigned to a user group index comprises a set of contiguous frequency subcarriers.

8. A receiving device (400), configured to: obtain a plurality of user group-specific signals (402) from a received signal (401) based on a plurality of user group indices, wherein each user group-specific signal (402) is for a user group that is identified by a user group index (1012); decompose each user group-specific signal (402) into a plurality of user-specific signals (403), wherein each userspecific signal (403) is for a respective user in the user group; decode each user-specific signal (403) to obtain a decoded sequence (404); andgenerate a decoded pay load (101) for the respective user based on the decoded sequence (404) and the user group index (1012).

9. The receiving device (400) according to claim 8, configured to: decompose each user group-specific signal (402) into the plurality of user-specific signals (403) using a multipath alternating least squares algorithm, wherein each decomposed user-specific signal comprises a plurality of subsequences.

10. The receiving device (400) according to claim 9, wherein the multipath alternating least squares algorithm is parameterized by an estimated channel delay spread and an estimated number of multipaths.

11. The receiving device (400) according to claim 8 or 9, to decode each user-specific signal (403), being configured to: estimate a user-specific phase offset based on the user-specific signal (403); perform phase offset correction on each subsequence of the plurality of subsequences based on the estimated userspecific phase offset; demap each phase offset corrected subsequence to obtain a plurality of demapped subsequences; merge the plurality of demapped subsequence to obtain a user-specific sequence; and decode the user-specific sequence and verify the integrity of the decoded user-specific sequence.

12. The receiving device (400) according to claim 11, configured to: generate a reconstructed signal based on the plurality of decoded user-specific sequences, for which the integrity is successfully checked; and perform interference cancellation iterations for the plurality of decoded user-specific sequences, for which the integrity is successfully checked , based on the reconstructed signal.

13. The receiving device (400) according to one of the claims 8 to 12, configured to: determine a sequence of m bits (1011) based on the user group index (1012); and combine the sequence of m bits (1011) with the decoded user-specific sequence (404) to generate the decoded payload (101) for each user.

14. The receiving device (400) according to one of the claims 9 to 13, configured to: obtain, for each user group, a user group-specific signal (402) through a resource demapping so that the user groupspecific signal (402) corresponds to the received signal (401) at a set of resource elements of that user group, wherein the set of resource elements is assigned to the user group at the transmitting device (100) from T available timefrequency resource elements based on the user group index (1012).

15. A method (1100) performed by a transmitting device (100), comprising: obtaining (1101) a payload (101), wherein the payload (101) comprises a sequence of B bits, wherein B is a positive integer; extracting (1102) m bits (1011) from the sequence of B bits (101), wherein m is a positive integer less than B; identifying (1103) a user group index (1012) for the user based on the extracted m bits (1011), wherein the transmitting device (100) is a user in a user group identified by the user group index (1012); encoding (1104) the sequence of B minus m bits (102) to obtain an encoded signal (103); assigning (1105) a set of resource elements from T available time-frequency resource elements based on the identified user group index (1012), wherein T is a positive integer; andtransmitting (1106) the encoded signal (103) using the set of resource elements.

16. The method (1100) according to claim 15, comprising: encoding the sequence of B minus m bits (102) using a tensor-based modulation, TBM, encoder (104), to obtain the encoded signal (103).

17. The method (1100) according to claim 15, wherein the encoding the sequence of B minus m bits (102) using the TBM encoder (104) comprises: encoding the sequence of B minus m bits (102) using a forward error correction encoder to generate a sequence of coded bits; splitting the sequence of coded bits into a plurality of subsequences; modulating the plurality of subsequences to produce a plurality of encoded subsequences; and generating the encoded signal (103) based on the plurality of encoded subsequences.

18. A method (1200) performed by a receiving device (400), comprising: obtaining (1201) a plurality of user group-specific signals (402) from a received signal (401) based on a plurality of user group indices, wherein each user group-specific signal (402) is for a user group of that is identified by a user group index (1012); decomposing (1202) each user group-specific signal (402) into a plurality of user-specific signals (403), wherein each user-specific signal (403) is associated with a respective user in the user group; decoding (1203) each user-specific signal (403) to obtain a decoded sequence (404); and generating (1204) a decoded payload (101) for a respective user based on the decoded sequence (404) and the user group index (1012).

19. The method (1200) according to claim 18, comprising: decomposing each user group-specific signal (402) into the plurality of user-specific signals (403) using a multipath alternating least squares algorithm, wherein each decomposed user-specific signal comprises a plurality of subsequences.

20. The method (1200) according to claim 18 or 19, wherein the decoding each user-specific signal (403) comprises: estimating a user-specific phase offset based on the user-specific signal (403); performing phase offset correction on each subsequence of the plurality of subsequences based on the estimated userspecific phase offset; demapping each phase offset corrected subsequence to obtain a plurality of demapped subsequences; merging the plurality of demapped subsequence to obtain a user-specific sequence; and decoding the user-specific sequence and verify the integrity of the decoded user-specific sequence.

21. A computer program product comprising a program code for carrying out, when implemented on a processor, the method according to one of the claims 15 to 17, or the method according to one of the claims 18 to 20.

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