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DNF-SC-PNC: a new physical-layer network coding scheme for two-way relay channels with asymmetric data length

WIRELESS networkS 2019年第7期25卷 3727-3734页

作者： Yang, Hongjuan Li, Bo Liu, Gongliang Liu, Xin Peng, Xiyuan Harbin Inst Technol Weihai Sch Informat & Elect Engn Weihai Peoples R China Harbin Inst Technol Auto Test & Control Inst Harbin Peoples R China Dalian Univ Technol Sch Informat & Commun Engn Dalian Peoples R China

To improve the bit error rate (BER) performance of physical-layer network coding (PNC) in data length asymmetric two-way relay channels (TWRC), a new PNC scheme named combined denoise-and-forward and superposition coded physical-layer network coding (DNF-SC-PNC) is proposed, and the decoding algorithm of the scheme is improved. In the new scheme, the mixed information is denoised and superposed at the relay node, which will be broadcasted to the destination nodes. The destination nodes can use successive interference cancellation (SIC) or likelihood rate (LLR) algorithm for decoding. Theoretical analysis and simulation results show that DNF-SC-PNC can provide better BER performance and better throughput rate performance when the data length is asymmetric. Furthermore, we also proved that LLR algorithm can provide better performance than SIC algorithm in data length asymmetric TWRC.

关键词： physical-layer network coding Asymmetric data length SIC algorithm LLR algorithm

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Unsaturated Throughput Analysis of physical-layer network coding Based on IEEE 802.11 Distributed Coordination Function

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第11期12卷 5544-5556页

作者： Lin, Shijun Fu, Liqun Xiamen Univ Dept Commun Engn Xiamen Fujian Peoples R China Chinese Univ Hong Kong Inst Network Coding Shatin Hong Kong Peoples R China

In this paper, we investigate the throughput performance of physical-layer network coding (PNC) under the IEEE 802.11 distributed coordination function (DCF). We consider the wireless network that two client groups communicate with each other across one relay node, and focus on the unsaturated network case. The difficulty in modeling the relay systems under the IEEE 802.11 DCF is that the minimum contention window sizes of the client nodes and the relay node may be different, which makes the traditional throughput analysis methods for the non-relay wireless networks inapplicable. Fortunately, we find that the relay system can be decomposed into four parts and respectively modeled. Analytical results show that the throughput gain of PNC scheme is heavily affected by the probability that a transmitted network-coding (NC) packet contains the information of two packets. The implication is that the throughput benefit of PNC is more significant for bidirectional isochronous traffic with rate requirements. We further derive an approximate closed-form solution of the optimal transmission probability of client nodes that maximizes the PNC network throughput. We validate our analytical model through extensive simulations and discuss the relationship between the PNC network throughput and other system parameters, such as the minimum contention window sizes of both the client nodes and the relay node.

关键词： physical-layer network coding IEEE 802.11 DCF unsaturated throughput analysis

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Asynchronous physical-layer network coding With Quasi-Cyclic Codes

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2015年第2期33卷 309-322页

作者： Wang, Ping-Chung Huang, Yu-Chih Narayanan, Krishna R. Texas A&M Univ Dept Elect & Comp Engn College Stn TX 77843 USA

Communication in the presence of bounded timing asynchronism, which is known to the receiver but cannot be easily compensated, is studied. Examples of such situations include point-to-point communication over intersymbol interference (ISI) channels and asynchronous wireless networks. In these scenarios, although the receiver may know all the delays, it is often not an easy task for the receiver to compensate the delays as the signals are mixed together. A novel framework, which is called interleave/deinterleave transform (IDT), is proposed to deal with this problem. It is shown that the IDT allows one to design the delays so that quasi-cyclic (QC) codes with a proper shifting constraint can be used accordingly. When used in conjunction with QC codes, IDT provides significantly better performance than existing schemes relying solely on cyclic codes. Two instances of asynchronous physical-layer network coding, namely, the integer-forcing equalization for ISI channels and asynchronous compute-and-forward, are then studied. For integer-forcing equalization, the proposed scheme provides improved performance over using cyclic codes. For asynchronous compute-and-forward, the proposed scheme shows that there is no loss in the achievable information rates due to delays that are integer multiples of the symbol duration. Furthermore, the proposed approach shows that delays introduced by the channel can sometimes be exploited to obtain higher information rates than those obtainable in the synchronous case. The proposed IDT can be thought of as a generalization of the interleaving/deinterleaving idea proposed by Wang et al., which allows the use of QC codes, thereby substantially increasing the design space.

关键词： Compute-and-forward physical-layer network coding integer-forcing receiver

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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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On the relay selection for cooperative wireless networks with physical-layer network coding

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WIRELESS networkS 2012年第6期18卷 653-665页

作者： Zheng, Zeyu Fu, Shengli Lu, Kejie Wang, Jianping Chen, Biao Univ N Texas Dept Elect Engn Denton TX 76207 USA City Univ Hong Kong Dept Comp Sci Hong Kong Hong Kong Peoples R China Univ Puerto Rico Dept Elect & Comp Engn Mayaguez PR 00681 USA Univ Macau Fac Sci & Technol Dept Comp & Informat Sci Macau Peoples R China

In this paper, we investigate a large cooperative wireless network with relay nodes, in which cooperation is enabled through physical-layer network coding (PLNC). Specifically, we study the impact of the relay selection on the network capacity with power constraints in two scenarios. First, we consider the basic PLNC model (a.k.a., the ARB model), in which one pair of source nodes (A, B) exchange messages via a selected relay node (R). Given the power constraint, we derive the optimal relay selection and power allocation that maximize the sum capacity, defined as the summation of the capacity for two source-destination channels. Based on results obtained above, we then consider a more general scenario with multiple pairs of source nodes. Assuming the constant power constraint, we derive the upper bound of the minimal sum capacity of any source pair. The optimal power allocation among multiple source pairs is also derived. To validate these theoretical results, we also provide two relay selection strategies: a modified optimal relay assignment strategy and a novel middle point strategy for maximizing the minimal sum capacity of any source pair.

关键词： physical-layer network coding The ARB model Relay selection Power constraints Sum capacity

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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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Modulated Retro-Reflector-Based physical-layer network coding for Space Optical Communications

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IEEE ACCESS 2021年 9卷 44868-44880页

作者： Jia Yanmei Lyu Congmin Shen Pengfei Lu Lu Univ Chinese Acad Sci Sch Aeronaut & Astronaut Beijing 100049 Peoples R China Chinese Acad Sci Technol & Engn Ctr Space Utilizat Key Lab Space Utilizat Beijing 100094 Peoples R China

We propose a Modulated Retro-Reflector (MRR) based physical-layer network coding (PNC) framework for space two-way relay (TWR) optical communications. MRR PNC simplifies the end node's design by replacing pointing, acquisition and tracking mechanisms which require large size, weight, and power (SWaP) consumption. Each end node modulates its data on top of the interrogating beam from the relay node so that the two end nodes' frequencies are synchronized and there is no carrier frequency offset between the two end nodes and the relay. However, the transmitted signal based on the interrogating beam and twice the channel fading leads to noise aggregation. We analyze the impact of this noise aggregation by deriving the bit error rate (BER) for MRR PNC and performing simulations in Gamma-Gamma fading channels. The simulation results show that MRR PNC has a 3 dB optical signal noise ratio penalty compared with MRR "point-to-point" systems. The overall system throughput of MRR PNC is 99% higher than the traditional non-network-coded scheme in the >= 6 dB (for BPSK, >= 9 dB for QPSK) signal noise ratio regime. We propose using low-density parity-check (LDPC) codes to mitigate the problem of the degradation of the BER caused by the noise aggregation in MRR PNC. Our simulation results show that a rate 1/2 LDPC code can achieve 2 dB coding gain on BER 10(-3). We show that the asynchrony penalty is 3 dB on BER 10(-3) compared with a synchronous system. The implication is that when channel coding is used, the system can still work. Our findings show that MRR PNC can double the system throughput while keeping low values of SWaP, is feasible for space TWR optical communications.

关键词： Relays Laser beams Throughput Bit error rate Modulation network coding High-speed optical techniques physical-layer network coding two-way relay channel modulated retro-reflector MRR PNC MRR ANC throughput

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A Framework for Evaluating physical-layer network coding Gains in Multi-Hop Wireless networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2019年第12期18卷 2725-2739页

作者： Naves, Raphael Khalife, Hicham Jakllari, Gentian Conan, Vania Beylot, Andre-Luc Thales Commun & Secur F-92622 Gennevilliers France Univ Toulouse ENSEEIHT Dept Telecommun & Networks F-31000 Toulouse France

physical-layer network coding (PLNC) was first introduced as a solution to increase the throughput of a two-way relay channel communication. Unlike most wireless communication techniques which try to avoid collisions, PLNC allows two simultaneous transmissions to a common receiver. In basic topologies, this technique has been shown to significantly enhance the throughput performance compared to classical interference-free communications. However, quantifying the impact of PLNC in large multi-hop networks remains an open question. In this work, we introduce the first theoretical framework that, given a particular network topology and traffic matrix, can evaluate the optimal network throughput subject to a fairness constraint relative to the initial demand of each flow, when PLNC is adopted. Based on linear programming, our solution ensures to respect the particularities imposed by PLNC. We use this framework to evaluate three state-of-the-art PLNC schemes across a variety of topologies and traffic matrices. Our numerical analysis reveals that while in simple toy topologies PLNC can significantly increase the network throughput, in large topologies the verdict is mixed. For certain topologies and traffic patterns adopting PLNC can double the throughput while in others, depending on the scheme used for implementing PLNC, the gain can be as high as 60 percent or as low as 0 percent when compared to traditional interference-free transmissions.

关键词： Throughput network coding network topology Topology Relays Spread spectrum communication Wireless communication physical-layer network coding interference management scheduling

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Identification of superposed modulations for two-way relaying MIMO systems with physical-layer network coding

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IET COMMUNICATIONS 2017年第2期11卷 225-231页

作者： Ben Chikha, Wassim Chaoui, Slim Attia, Rabah Carthage Univ Tunisia Polytech Sch SERCOM Lab La Marsa 2078 Tunisia

The automatic modulation identification of a detected signal represents an essential task for an intelligent receiver and plays an important role in demodulating the intercepted signals for several communication systems. In this study, the authors propose an efficient algorithm of superposed modulations identification dedicated for two-way relaying multiple-input multiple-output systems with physical-layer network coding (PLNC). The aim of this work is to identify a pair of sources modulations from the superposed constellation, when PLNC is applied. For this purpose, the authors use the higher order statistics-based features in conjunction with genetic algorithm and information theory as a features selection method and the random forests as a classifier. Simulations are provided to assess the accuracy of the proposed algorithm through the average probability of correct identification for different modulation scheme pairs. It is shown that the algorithm achieves high-modulation identification in acceptable signal-to-noise ratio level at different relay position.

关键词： feature selection genetic algorithms higher order statistics radio receivers signal detection relay networks (telecommunication) network coding MIMO communication two-way relaying MIMO system superposed modulation identification physical-layer network coding automatic modulation identification signal detection intelligent receiver two-way relaying multiple-input multiple-output system PLNC source modulation superposed constellation relay position signal-to-noise ratio level random forest feature selection method information theory genetic algorithm higher order statistics-based feature

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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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