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Short-Packet physical-layer network coding

IEEE TRANSACTIONS ON COMMUNICATIONS 2020年第2期68卷 737-751页

作者： Ullah, Shakeel Salamat Liew, Soung Chang Liva, Gianluigi Wang, Taotao CU Coding Hong Kong Peoples R China Chinese Univ Hong Kong Dept Informat Engn Hong Kong Peoples R China German Aerosp Ctr DLR Inst Commun & Networking D-82234 Wessling Germany Shenzhen Univ Guangdong Lab Artificial Intelligence & Digital E Shenzhen 518060 Peoples R China

This paper explores the application of physical-layer network coding (PNC) for short-packet transmissions. PNC can potentially reduce the communication delay in relay-assisted wireless networks and can thus be instrumental in realizing short-packet communication systems with stringent delay requirements. In this work, first, we first derive an achievability bound for channel-coded short-packet PNC systems. Based on the random-coding error-exponent, the bound serves as a benchmark for short-packet PNC operating with traditional preamble-aided channel estimation and XOR channel decoding. Second, we design a blind channel estimation algorithm and a code-aided channel estimation algorithm for short-packet PNC systems. Both outperform the traditional preamble-aided channel estimation for PNC systems operating with mismatched channel-state-information. As a case study, we compare the three algorithms for packets of 128 symbols over a two-way relay channel. The results show that the blind algorithm outperforms the code-aided algorithm and preamble-aided algorithm by almost 0.2 and 1.5 dB respectively. Furthermore, the blind algorithm achieves the target packet error rate of 10(-4) within 0.5 dB of the random coding bound of an imaginary system in which perfect channel-state-information is available at the relay at no cost (i.e., channel estimation is not required in the imaginary system). The bound and the algorithms give us a fundamental framework for applying PNC to short-packet transmissions.

关键词： Channel estimation Decoding Delays Relays Uplink Estimation Benchmark testing physical-layer network coding short-packet transmissions random coding bound mismatched channel-state-information expectation-maximization belief-propagation

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Channel-Coded physical-layer network coding With OFDM Modulation

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IEEE ACCESS 2018年 6卷 22267-22280页

作者： Xie, Ling Fu Ho, Ivan Wang-Hei Stiu, Zhen Hui Lu, Lu Lu, Weidang Ningbo Univ Fac Elect Engn & Comp Sci Ningbo 315211 Zhejiang Peoples R China CETC Sci & Technol Commun Networks Lab Shijiazhuang 050081 Hebei Peoples R China Hong Kong Polytech Univ Dept Elect & Informat Engn Hong Kong Hong Kong Peoples R China Chinese Acad Sci Technol & Engn Ctr Space Utilizat Key Lab Space Utilizat Beijing 100864 Peoples R China Zhejiang Univ Technol Coll Informat Engn Hangzhou 310023 Zhejiang Peoples R China

This paper addresses the carrier frequency offset (CFO) problem in OFDM modulated physical-layer network coding (PNC) operated in a two-way relay channel (TWRC). CFO, caused by node-motion induced Doppler shifts and/or asynchronous oscillators, induces inter-carrier interference (ICI) between OFDM subcarriers and hence, degrades PNC performance. To mitigate the CFO/ICI effect in PNC, this paper considers channel-coded PNC and focuses on the receiver design at the relay. CFO compensation, signal detection, and channel decoding are the three basic signal processing blocks at the relay node. For the latter two, we consider both a joint and a separate design. For the joint design, we construct a factor graph to integrate channel coding with ICI, and then, propose a scheme based on belief propagation. For the separate design, two low-complexity schemes differing in channel decoding are proposed. Our simulation results, using repeat-accumulate channel codes, reveal that (1) a CFO compensation approach that amounts to positioning the relay's oscillator frequency at the middle of the received frequencies from the two end nodes is bit error rate (BER)-optimal for all the three schemes;(2) the joint design is superior at low SNR and/or high CFO levels;and (3) more importantly, with the joint design, for low-to-medium CFO levels, the BER of the channel-coded PNC is comparable with that of traditional point-to-point communications without CFO, thus manifesting itself as a promising technique in OFDM modulated TWRC with practical CFO constraints.

关键词： Belief propagation carrier frequency offset inter-carrier interference OFDM physical-layer network coding

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An Algebraic Framework for End-to-End physical-layer network coding

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IEEE TRANSACTIONS ON INFORMATION THEORY 2018年第6期64卷 4480-4495页

作者： Gorla, Elisa Ravagnani, Alberto Univ Neuchatel CH-2000 Neuchatel Switzerland

We propose an algebraic framework for end-to-end physical-layer network coding based on submodules transmission. Our approach is motivated by nested-lattice-based network coding schemes, that naturally induce end-to-end channels where the ambient space has the structure of a module over a principal ideal ring. The setup is compatible with previously proposed approaches for finite chain rings, and extends them to arbitrary principal ideal rings. We introduce a distance function between modules, and describe how it relates to information loss and errors. We also show that computing the distance between modules reduces to computing the length of certain ideals in the base ring. We then propose a definition of submodule error-correcting code, and establish two upper bounds for the cardinality of these codes. Finally, we present some constructions of submodule codes, showing that they have asymptotically optimal cardinality for certain choices of the parameters.

关键词： physical-layer network coding nested lattices submodule (ring theory) submodule distance submodule code

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Design of Irregular Repeat-Accumulate Coded physical-layer network coding for Gaussian Two-Way Relay Channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2013年第3期61卷 897-909页

作者： Huang, Tao Yang, Tao Yuan, Jinhong Land, Ingmar Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW 2052 Australia CSIRO WNTL Sydney NSW Australia Univ S Australia Inst Telecommun Res Adelaide SA 5001 Australia

This paper addresses the design of irregular repeat accumulate (IRA) codes for coded physical-layer network coding (PNC) for the binary-input Gaussian two-way relay channel, assuming perfect synchronization and equal received power at the relay. The design is based on a nontrivial extension of EXIT-chart based design. Specifically, we analyze the components of the IRA-PNC scheme and propose an approach to model the soft information exchanged between these components. Then, we develop upper and lower bounds on the extrinsic information transfer functions to characterize the iterative process of computing the network-coded information. Based on that, we construct optimized IRA codes to minimize the computation error at the relay. The optimized IRA-PNC has considerable performance improvement over the existing regular RA coded PNC. For a rate 3/4 code, as an example, we observed improvements of 2.6 dB, and the optimized IRA-PNC scheme is only about 1.7 dB away from the capacity upper bound of the Gaussian two-way relay channel.

关键词： Two-way relay channel physical-layer network coding compute-and-forward Repeat-Accumulate codes convergence analysis EXIT chart

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Spatial-Modulated physical-layer network coding Based on Block Markov Superposition Transmission for Maritime Relay Communications

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China Communications 2020年第3期17卷 26-35页

作者： Yao Shi Liming Zheng Wenchao Lin Xiao Ma School of Data and Computer Science Sun Yat-sen UniversityGuangzhou 510006China Guangdong Key Laboratory of Information Security Technology Sun Yat-sen UniversityGuangzhou 510006China

As an alternative to satellite communications,multi-hop relay networks can be deployed for maritime long-distance *** from terrestrial environment,marine radio signals are affected by many factors,e.g.,weather conditions,evaporation ducting,and ship rocking caused by *** ensure the data transmission reliability,the block Markov superposition transmission(BMST)codes,which are easily configurable and have predictable performance,are applied in this ***,the physical-layer network coding(PNC)scheme with spatial modulation(SM)is adopted to improve the spectrum *** the BMST-SMPNC system,we propose an iterative algorithm,which utilizes the channel observations and the a priori information from BMST decoder,to compute the soft information corresponding to the XORed bits constructed by the relay *** results indicate that the proposed scheme outperforms the convolutional coded SM-PNC over fast-fading Rician ***,the performance can be easily improved in high spatial correlation maritime channel by increasing the memory m.

关键词： block Markov superposition transmission maritime relay communications physical-layer network coding Rician fading spatial modulation

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A Non-Orthogonal Multiple-Access Scheme Using Reliable physical-layer network coding and Cascade-Computation Decoding

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2017年第3期16卷 1633-1645页

作者： Yang, Tao Yang, Lei Guo, Y. Jay Yuan, Jinhong Univ Technol Sydney Global Big Data Technol Ctr Ultimo NSW 2007 Australia Univ New South Wales Sydney NSW 2052 Australia

This paper studies non-orthogonal transmission over a K-user fading multiple access channel. We propose a new reliable physical-layer network coding and cascade-computation decoding scheme. In the proposed scheme, K single-antenna users encode their messages by the same practical channel code and QAM modulation, and transmit simultaneously. The receiver chooses K linear coefficient vectors and computes the associated K layers of finite-field linear message combinations in a cascade manner. Finally, the K users' messages are recovered by solving the K linear equations. The proposed can be regarded as a generalized onion peeling. We study the optimal network coding coefficient vectors used in the cascade computation. Numerical results show the performance of the proposed approaches that of the iterative maximum a posteriori probability detection and decoding scheme, but without using receiver iteration. This results in considerable complexity reduction, processing delay, and easier implementation. Our proposed scheme significantly outperforms the iterative detection and decoding scheme with a single iteration, for example, by 1.7 dB for the two user case. The proposed scheme provides a competitive solution for non-orthogonal multiple access.

关键词： Multiuser detection MIMO physical-layer network coding compute-and-forward iterative decoding

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ARQ for physical-layer network coding

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2016年第7期15卷 1614-1631页

作者： He, Jianghao Liew, Soung-Chang Chinese Univ Hong Kong Dept Informat Engn Hong Kong Hong Kong Peoples R China

This paper investigates Automatic Repeat request (ARQ) designs for physical-layer network coding (PNC) systems. Most prior work related to PNC explores its use in Two-Way Relay Channel (TWRC). We have previously found that, besides TWRC, there are many other PNC building blocks-building blocks are simple small network structures that can be used to construct a large network. In some of these PNC building blocks, the receivers can obtain side information through overhearing. Although such overheard information is not the target information that the receivers desire, the receivers can exploit the overheard information together with a network-coded packet received to obtain a desired native packet. This can yield substantial throughput gain. Our previous study, however, assumed what is sent always gets received. In practice, that is not the case. Error control is needed to ensure reliable communication. This paper focuses on ARQ designs for ensuring reliable PNC communication. The availability of overheard Information and its potential exploitation make the ARQ design of a network-coded system different from that of a non-network-coded system. In this paper, we lay out the fundamental considerations for such ARQ designs: 1) we put forth a framework to track the stored coded packets and overheard packets to increase the chance of packet extraction, and derive the throughput gain achieved therefore;2) we investigate two variations of PNC ARQ, coupled and non-coupled ARQs, and prove that non-coupled ARQ is more efficient;3) we show how to optimize parameters in PNC ARQ-specifically the window size and the ACK frequency-to minimize the throughput degradation caused by ACK feedback overhead and wasteful retransmissions due to lost ACK.

关键词： physical-layer network coding multi-hop wireless networks selective repeat ARQ selective acknowledgements wireless scheduling overheard information end-to-end design unicast

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The Performance of physical-layer network coding in Asymmetric Rayleigh Fading Two-Way Relay Channels

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MOBILE networkS & APPLICATIONS 2018年第2期23卷 301-307页

作者： Li, Bo Yang, Hongjuan Liu, Gongliang Peng, Xiyuan Harbin Inst Technol Weihai Weihai Peoples R China Sci & Technol Commun Networks Key Lab Shijiazhuang Hebei Peoples R China Harbin Inst Technol Harbin Heilongjiang Peoples R China

Up to now, most of the researches about physical-layer network coding (PNC) are based on symmetric two-way relay channels. In this paper, we mainly study PNC in asymmetric two-way relay Rayleigh fading channels and classify the systems into five asymmetric cases. So as to describe the asymmetric cases, we introduce the asymmetric factors. We simulate the bit error rate (BER) performance of PNC in both symmetric and asymmetric cases with asymmetric factors fixed. After that we analyze the BER performance of PNC with one of the asymmetric factors is variable when two channels are relatively unreliable. Finally, we give the conditions that one kind of asymmetric scenario transforming to other kind. Also, in the matter of anti-noise performance, uplink asymmetry has worst performance and the phase asymmetry-downlink is the best case.

关键词： physical-layer network coding Asymmetric two-way relay channels Bit error rate Rayleigh fading

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Asynchronous physical-layer network coding Scheme for Broadband Two-Way Relay Channels

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WIRELESS PERSONAL COMMUNICATIONS 2016年第1期89卷 149-163页

作者： Xia, Xiaochen Xu, Kui Xu, Youyun PLA Univ Sci & Technol Inst Commun Engn 2 Biaoying St Nanjing Jiangsu Peoples R China Shanghai Jiao Tong Univ Inst Wireless Commun Technol Shanghai 200030 Peoples R China

In OFDM based two-way relay channels, carrier frequency offsets (CFOs) between relay and terminal nodes introduce severe inter-carrier interference which degrades the performance of traditional physical-layer network coding. In this paper, we present a two-step asynchronous physical-layer network coding scheme, which consists of an interference cancelation step and a network coding mapping step, to deal with the frequency asynchrony in two-way OFDM relay system. We show through the average signal-to-interference-plus-noise ratio (SINR) and bit error rate (BER) that the proposed scheme can efficiently map the received superimposed signal, which is corrupted by the CFOs, into the exclusive OR of two terminals' transmitted symbols. Moreover, a simple upper bound of the average SINR for the proposed scheme is derived. Through the simulation results, it is shown that the exact average SINR curve of the proposed scheme is very close to the upper bound even when the normalized CFO is as large as 0.15. Finally, we show that the average SINR and BER performances of the proposed scheme outperform the reference schemes considerably.

关键词： Two-way relay channels physical-layer network coding Asynchronous SINR BER

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Space-Time physical-layer network coding

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2015年第2期33卷 323-336页

作者： Lee, Namyoon Heath, Robert W., Jr. Univ Texas Austin Dept Elect & Comp Engn Wireless Networking & Commun Grp Austin TX 78712 USA

A space-time physical-layer network coding (ST-PNC) method is presented for information exchange among multiple users over fully connected multiway relay networks. The method involves two steps: 1) side-information learning and 2) space-time relay transmission. In the first step, different sets of users are scheduled to send signals over networks, and the remaining users and relays overhear the transmitted signals, thereby learning the interference patterns. In the second step, multiple relays cooperatively send out linear combinations of signals received in the previous phase using space-time precoding so that all users efficiently exploit their side information in the form of 1) what they sent and 2) what they overheard in decoding. This coding concept is illustrated through two simple network examples. It is shown that ST-PNC improves the sum of degrees of freedom (sum-DoF) of the network compared to existing interference management methods. With ST-PNC, the sum-DoF of a general multiway relay network without channel knowledge at the users is characterized in terms of relevant system parameters, chiefly the number of users, the number of relays, and the number of antennas at relays. A major implication of the derived results is that efficiently harnessing both transmitted and overheard signals as side information brings significant performance improvements to fully connected multiway relay networks.

关键词： physical-layer network coding space-time precoding multi-way relay channels

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