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IEEE Global Communications Conference

作者： Shen Feng Soung C. Liew Dept. of Information Engineering The Chinese University of Hong Kong

ISBN: (纸本)9781479913510

This work investigates the maximum broadcast throughput and its achievability in multi-hop wireless networks with half-duplex node constraint. We allow the use of physical-layer network coding (PNC). Although the use of PNC for unicast has been extensively studied, there has been little prior work on PNC for broadcast. Our specific results are as follows: 1) For single-source broadcast, the theoretical throughput upper bound is n/(n+1), where n is the "min vertex-cut" size of the network. 2) In general, the throughput upper bound is not always achievable. 3) For grid and many other networks, the throughput upper bound n/(n+1) is achievable. Our work can be considered as an attempt to understand the relationship between max-flow and min-cut in half-duplex broadcast networks with cycles (there has been prior work on networks with cycles, but not half-duplex broadcast networks).

关键词： Wireless broadcast physical-layer network coding

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Practical NOMA-Based Coordinated Direct and Relay Transmission

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IEEE WIRELESS COMMUNICATIONS LETTERS 2021年第1期10卷 170-174页

作者： Pan, Haoyuan Liang, Jiaxin Liew, Soung Chang Shenzhen Univ Coll Comp Sci & Software Engn Shenzhen 518060 Peoples R China Chinese Univ Hong Kong Dept Informat Engn Hong Kong Peoples R China

This letter puts forth a practical non-orthogonal multiple access (NOMA)-based coordinated direct and relay transmission (CDRT) scheme, referred to as network-coded multiple access CDRT (NCMA-CDRT). We consider a two-user uplink scenario, where a near user communicates directly to a base station (BS), whereas a far user needs the assistance of a decode-and-forward relay. While prior NOMA-CDRT studies focused extensively on theoretical analysis, its superiority has not been well investigated through practical communication schemes. In particular, successive interference cancellation (SIC), a predominant NOMA decoding technique, does not work well if transmitters with comparable received powers transmit together. We investigate NCMA-CDRT to tackle this practical issue. A distinguishing feature of NCMA-CDRT is the joint use of physical-layer network coding (PNC) and multiuser decoding at both the relay and the BS. We design packet relaying strategies that can forward the PNC packets decoded at the relay to boost system throughput. Experiments on software-defined radio indicate that the total throughput of NCMA-CDRT significantly outperforms the SIC-based NOMA-CDRT. Overall, NCMA-CDRT is a viable solution for cooperative NOMA systems.

关键词： Non-orthogonal multiple access physical-layer network coding cooperative NOMA implementation

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Backbone-Assisted Wireless Local Area network

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2021年第3期20卷 830-845页

作者： Pan, Haoyuan Liew, Soung Chang Chinese Univ Hong Kong Dept Informat Engn Hong Kong Peoples R China

This article presents a cross-layer design of backbone-assisted wireless local area network (WLAN) for dense WLAN deployment. The popularity of 802.11-based WLANs leads to dense WLAN deployment in geographically limited space, including dense access points (AP) and dense users. With dense APs, an AP could overhear packets destined for other APs. Backbone-assisted WLAN is a new system architecture where cooperative APs share the overheard packets through a backbone network, thereby reducing packet retransmission and improving system throughput. Conventional WLAN, such as Wi-Fi, uses Stop-and-Wait ARQ. This article argues that Stop-and-Wait does not work well with backbone-assisted WLAN because of large backbone delays. We first show that with a variant of Selective Repeat ARQ tailored for backbone-assisted WLAN, a single-user backbone-assisted WLAN system can achieve substantial throughput improvement over that with Stop-and-Wait ARQ. Then, we put forth a new system architecture targeted for dense users, referred to as network-coded backbone-assisted WLAN, in which multiple users are allowed to transmit simultaneously. A distinguishing feature of this system is the joint use of physical-layer network-coding (PNC) decoding and multiuser decoding (MUD) in multipacket reception. This article is the first attempt to design an ARQ for multiuser backbone-assisted WLAN. Our overall system design solves a PNC sequence obfuscation problem and addresses long packet latency in Selective Repeat ARQ. Experiments on our software-defined radio prototype indicate that network-coded Ethernet-backbone-assisted WLAN can achieve high system throughput and low packet latency. Specifically, the system throughput can outperform an MUD-only multiuser WLAN and a single-user WLAN by 60 and 100 percent, respectively. Overall, we believe that network-coded backbone-assisted WLAN is a viable solution for boosting throughput and reducing latency in dense WLAN environments.

关键词： Wireless LAN Throughput Multiuser detection Decoding Ethernet Delays Protocols Wireless local area network backbone physical-layer network coding multiuser detection ARQ implementation

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Lattice-Code Multiple Access: Architecture and Efficient Algorithms

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IEEE Transactions on Vehicular Technology 2025年

作者： Yang, Tao Yu, Fangtao Liu, Rongke Lyu, Shanxiang Thompson, John Beihang University School of Electronic and Information Engineering Beijing100191 China Shenzhen Institute of Beihang University Shenzhen518000 China Jinan University College of Cyber Security Guangzhou510632 China University of Edinburgh Institute for Digital Communications School of Engineering EdinburghEH9 3JL United Kingdom

This paper studies a K-user lattice-code based multiple-access (LCMA) scheme. Each user equipment (UE) encode its message with a practical lattice code, where we suggest a 2m-ary ring code with symbol-wise bijective mapping to 2m-PAM. The coded-modulated signal is spread with its designated signature sequence, and all K UEs transmit simultaneously. The LCMA receiver choose some integer coefficients, computes the associated K streams of integer linear combinations (ILCs) of the UEs' messages, and then reconstruct all UEs' messages from these ILC streams. To execute this, we put forth new efficient LCMA soft detection algorithms, which calculate the a posteriori probability of the ILC over the lattice. The complexity is of order no greater than O(K), suitable for massive access of a large K. The soft detection outputs are forwarded to K ring-code decoders, which employ 2m-ary belief propagation to recover the ILC streams. To identify the optimal integer coefficients of the ILCs, a new " bounded independent vectors problem" (BIVP) is established. We then solve this BIVP by developing a new rate-constraint sphere decoding algorithm, significantly outperforming existing LLL and HKZ lattice reduction methods. Then, we develop optimized signature sequences of LCMA using a new target-switching steepest descent algorithm. With our developed algorithms, LCMA is shown to support a significantly higher load of UEs and exhibits dramatically improved error rate performance over state-of-the-art multiple access schemes such as interleave-division multiple-access (IDMA) and sparse-code multiple-access (SCMA). The advances are achieved with just parallel processing and K single-user decoding operations, avoiding the implementation issues of successive interference cancelation and iterative detection. © 1967-2012 IEEE.

关键词： coded modulation compute-forward iterative detection lattice reduction lattice-codes MIMO Multiple access physical-layer network coding soft detection

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physical layer network coding Based on Integer Forcing Precoded Compute and Forward

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FUTURE INTERNET 2013年第3期5卷 439-459页

作者： Gupta, Smrati Vazquez-Castro, M. A. Autonomous Univ Barcelona Dept Telecommun & Syst Engn E-08193 Barcelona Spain

In this paper, we address the implementation of physical layer network coding (PNC) based on compute and forward (CF) in relay networks. It is known that the maximum achievable rates in CF-based transmission is limited due to the channel approximations at the relay. In this work, we propose the integer forcing precoder (IFP), which bypasses this maximum rate achievability limitation. Our precoder requires channel state information (CSI) at the transmitter, but only that of the channel between the transmitter and the relay, which is a feasible assumption. The overall contributions of this paper are three-fold. Firstly, we propose an implementation of CF using IFP and prove that this implementation achieves higher rates as compared to traditional relaying schemes. Further, the probability of error from the proposed scheme is shown to have up to 2 dB of gain over the existent lattice network coding-based implementation of CF. Secondly, we analyze the two phases of transmission in the CF scheme, thereby characterizing the end-to-end behavior of the CF and not only one-phase behavior, as in previous proposals. Finally, we develop decoders for both the relay and the destination. We use a generalization of Bezout's theorem to justify the construction of these decoders. Further, we make an analytical derivation of the end-to-end probability of error for cubic lattices using the proposed scheme.

关键词： compute and forward lattices relaying probability of error precoding physical-layer network coding signal-to-noise ratio

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Decoding Strategies at the Relay with physical-layer network coding

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2012年第12期11卷 4503-4513页

作者： Bhat, Uttam Duman, Tolga M. Arizona State Univ Sch Elect Comp & Energy Engn ECEE Tempe AZ 85287 USA Bilkent Univ Dept Elect & Elect Engn TR-06800 Ankara Turkey

A two-way relay channel is considered where two users exchange information via a common relay in two transmission phases using physical-layer network coding (PNC). We consider an optimal decoding strategy at the relay to decode the network coded sequence during the first transmission phase, which is approximately implemented using a list decoding (LD) algorithm. The algorithm jointly decodes the codewords transmitted by the two users and sorts the L most likely pair of sequences in the order of decreasing a-posteriori probabilities, based on which, estimates of the most likely network coded sequences and the decoding results are obtained. Using several examples, it is observed that a lower complexity alternative, that jointly decodes the two transmitted codewords, has a performance similar to the LD based decoding and offers a near-optimal performance in terms of the error rates corresponding to the XOR of the two decoded sequences. To analyze the error rate at the relay, an analytical approximation of the word-error rate using the joint decoding (JD) scheme is evaluated over an AWGN channel using an approach that remains valid for the general case of two users adopting different codebooks and using different power levels. We further extend our study to frequency selective channels where two decoding approaches at the relay are investigated, namely;a trellis based joint channel detector/physical-layer network coded sequence decoder (JCD/PNCD) which is shown to offer a near-optimal performance, and a reduced complexity channel detection based on a linear receiver with minimum mean squared error (MMSE) criterion which is particularly useful where the number of channel taps is large.

关键词： Two-way relay channels physical-layer network coding union bounds joint decoding list decoding performance analysis frequency-selective channel MMSE detection

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Asynchronous physical-layer network coding

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2012年第2期11卷 819-831页

作者： Lu, Lu Liew, Soung Chang Chinese Univ Hong Kong Dept Informat Engn Shatin Hong Kong Peoples R China

A key issue in physical-layer network coding (PNC) is how to deal with the asynchrony between signals transmitted by multiple transmitters. That is, symbols transmitted by different transmitters could arrive at the receiver with symbol misalignment as well as relative carrier-phase offset. A second important issue is how to integrate channel coding with PNC to achieve reliable communication. This paper investigates these two issues and makes the following contributions: 1) We propose and investigate a general framework for decoding at the receiver based on belief propagation (BP). The framework can effectively deal with symbol and phase asynchronies while incorporating channel coding at the same time. 2) For unchannel-coded PNC, we show that for BPSK and QPSK modulations, our BP method can significantly reduce the asynchrony penalties compared with prior methods. 3) For QPSK unchannel-coded PNC, with a half symbol offset between the transmitters, our BP method can drastically reduce the performance penalty due to phase asynchrony, from more than 6 dB to no more than 1 dB. 4) For channel-coded PNC, with our BP method, both symbol and phase asynchronies actually improve the system performance compared with the perfectly synchronous case. Furthermore, the performance spread due to different combinations of symbol and phase offsets between the transmitters in channel-coded PNC is only around 1 dB. The implication of 3) is that if we could control the symbol arrival times at the receiver, it would be advantageous to deliberately introduce a half symbol offset in unchannel-coded PNC. The implication of 4) is that when channel coding is used, symbol and phase asynchronies are not major performance concerns in PNC.

关键词： physical-layer network coding network coding synchronization

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Distance Spectrum and Performance of Channel-Coded physical-layer network coding for Binary-Input Gaussian Two-Way Relay Channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2012年第6期60卷 1499-1510页

作者： Yang, Tao Land, Ingmar Huang, Tao Yuan, Jinhong Chen, Zhuo Commonwealth Sci & Ind Res Org CSIRO Wireless & Networking Technol Lab WNTL Sydney NSW Australia Univ S Australia Inst Telecommun Res Adelaide SA 5001 Australia Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW 2052 Australia

We investigate a channel-coded physical-layer network coding (CPNC) scheme for binary-input Gaussian two-way relay channels. In this scheme, the codewords of the two users are transmitted simultaneously. The relay computes and forwards a network-coded (NC) codeword without complete decoding of the two users' individual messages. We propose a new punctured codebook method to explicitly find the distance spectrum of the CPNC scheme. Based on that, we derive an asymptotically tight performance bound for the error probability. Our analysis shows that, compared to the single-user scenario, the CPNC scheme exhibits the same minimum Euclidean distance but an increased multiplicity of error events with minimum distance. At a high SNR, this leads to an SNR penalty of at most ln2 (in linear scale), for long channel codes of various rates. Our analytical results match well with the simulated performance.

关键词： Channel coding physical-layer network coding two-way relay channel distance spectrum compute-and-forward

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MAC for physical-layer network coding in VANETs

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INTERNATIONAL JOURNAL OF BUSINESS DATA COMMUNICATIONS AND networkING 2012年第4期8卷 84-106页

作者： Ndih, Eugene David Ngangue Cherkaoui, Soumaya Univ Sherbrooke Dept Elect & Comp Engn Sherbrooke PQ Canada

In this paper, the authors present VPNC-MAC, a PNC-based MAC protocol for efficient and reliable periodic beacon broadcasts in VANETs. In addition to PNC-based scheduled transmissions, VPNC-MAC makes use of CSMA/CA to ensure fairness and flexibility with transmissions from CSMA-based nodes. VPNC-MAC consists of two phases: In the setup phase, a quasi-optimal mechanism of selecting a relay node is proposed to take into account both the position, and the remaining time the relay needs for delivering its current beacon. In the packet exchange phase, they define two priority modes to deal with the cohabitation of both the CSMA-based and the VPNC-based nodes, and also with unpredictable events such as emergency broadcasts. Contrary to the high-priority mode, the VPNC-based nodes AIFS in the low-priority mode is set such that the medium access is granted prior to CSMA-based nodes. Simulations results show that the global PRR in high-priority mode outperforms existing MAC.

关键词： Dedicated Short-Range Communication (DSRC/802.11p) MAC Periodic Broadcast physical-layer network coding Reliability Vehicular Ad-Hoc networks (VANETs)

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Asymptotically Optimal Error-Rate Performance of Linear physical-layer network coding in Rayleigh Fading Two-Way Relay Channels

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IEEE COMMUNICATIONS LETTERS 2012年第7期16卷 1068-1071页

作者： Yang, Tao Collings, Iain B. CSIRO WNTL Sydney NSW Australia

We study a new linear physical-layer network coding (LPNC) scheme for fading two-way relay channels. In the uplink phase, two users transmit simultaneously. The relay selects some integer coefficients and computes a linear combination (in a size-q finite set) of the two users' messages, which is broadcast in the downlink phase. We develop a design criterion for choosing the integer coefficients that minimizes the error probability. Based on that, we derive an asymptotically tight bound, in a closed-form, for the error probability of the LPNC scheme over Rayleigh fading channels. Our analysis shows that the error-rate performance of the LPNC scheme becomes asymptotically optimal at a high SNR, and our designed LPNC scheme significantly outperforms existing schemes in the literature.

关键词： physical-layer network coding compute-and-forward code design relay channel

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