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Optimal Energy-Efficient Power Allocation and Outage Performance Analysis for Cognitive Multi-Antenna Relay network Using physical-layer network coding

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KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS 2013年第12期7卷 3018-3036页

作者： Liu, Jia Zhu, Ying Kang, GuiXia Zhang, YiFan Beijing Univ Posts & Telecommun Minist Educ Key Lab Univ Wireless Commun Beijing 100876 Peoples R China Guilin Univ Elect Technol Dept Teaching & Practicing Guilin 541004 Peoples R China

In this paper, we investigate power allocation scheme and outage performance for a physical-layer network coding (PNC) relay based secondary user (SU) communication in cognitive multi-antenna relay networks (CMRNs), in which two secondary transceivers exchange their information via a multi-antenna relay using PNC protocol. We propose an optimal energy-efficient power allocation (OE-PA) scheme to minimize total energy consumption per bit under the sum rate constraint and interference power threshold (IPT) constraints. A closed-form solution for optimal allocation of transmit power among the SU nodes, as well as the outage probability of the cognitive relay system, are then derived analytically and confirmed by numerical results. Numerical simulations demonstrate the PNC protocol has superiority in energy efficiency performance over conventional direct transmission protocol and Four-Time-Slot (4TS) Decode-and-Forward (DF) relay protocol, and the proposed system has the optimal outage performance when the relay is located at the center of two secondary transceivers.

关键词： physical-layer network coding energy-efficient power allocation cognitive relay system

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Design and Analysis of Multi-Level physical-layer network coding for Gaussian Two-Way Relay Channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2014年第6期62卷 1803-1817页

作者： Chen, Zhiyong Xia, Bin Hu, Zixia Liu, Hui Shanghai Jiao Tong Univ Dept Elect Engn IWCT Shanghai 200240 Peoples R China Qualcomm San Jose CA 95110 USA

In this paper, we propose a multi-level physical-layer network coding (MPLNC) scheme that optimizes the relay performance for both symmetric and asymmetric traffic in a Gaussian two-way relay channel. The proposed MPLNC scheme enables each source to employ multiple linear binary codes for encoding, one per modulation level, and the relay node to decode superimposed network codewords at each modulation level. We first derive the achievable rate for the transmission of arbitrary constellations and then prove that MPLNC with multistage decoding (MPLNCMSD) can achieve the achievable rate if binary code rates are properly chosen for both sources. Furthermore, the design criteria for the proposed MPLNC scheme is investigated, which includes the rate design rule and the labeling strategy. Moreover, we derive the error exponent and an upper bound of the overall error probability for MPLNC. Our analysis and simulation results show that MPLNCMSD has a significant performance advantage in comparison to the existing bit-interleaved coded modulation (BICM)-based PLNC scheme.

关键词： Two-way relay channels multilevel coding physical-layer network coding symmetric and asymmetric relaying error exponent

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Mobile Lattice-Coded physical-layer network coding with Practical Channel Alignment

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2018年第8期17卷 1908-1923页

作者： Tan, Yihua Liew, Soung Chang Huang, Tao Chinese Univ Hong Kong Dept Informat Engn Shatin Hong Kong Peoples R China Nanjing Univ Nanjing Shi 210008 Jiangsu Sheng Peoples R China

physical-layer network coding (PNC) is a communications paradigm that exploits overlapped transmissions to boost the throughput of wireless relay networks. A high point of PNC research was a theoretical proof that PNC that makes use of nested lattice codes could approach the information-theoretic capacity of a two-way relay network (TWRN), where two end nodes communicate via a relay node. The capacity cannot be achieved by conventional methods of time-division or straightforward network coding. Many practical challenges, however, remain to be addressed before the full potential of lattice-coded PNC can be realized. Two major challenges are: (1) for good performance in lattice-coded PNC, channels of simultaneously transmitting nodes must be aligned;(2) for lattice-coded PNC to be practical, the complexity of lattice encoding at the transmitters and lattice decoding at the receiver must be reduced. We address these challenges and implement a first lattice-coded PNC system on a software-defined radio (SDR) platform. Specifically, we design and implement a low-overhead channel precoding system that accurately aligns the channels of distributed nodes. In our implementation, the nodes use low-cost temperature-compensated oscillators (TCXO) only-a consequent challenge is that the channel alignment must be done more frequently and more accurately compared with the use of expensive oscillators. The low overhead and accurate channel alignment are achieved by (1) a channel precoding system implemented over FPGA to realize fast feedback of channel state information;(2) a highly-accurate carrier frequency offset (CFO) estimation method;and (3) a partial-feedback channel estimation method that significantly reduces the amount of feedback information from the receiver to the transmitters for channel precoding at the transmitters. To reduce lattice encoding and decoding complexities, we adapt the low-density lattice code (LDLC) for use in PNC systems. Experiments show that our impl

关键词： physical-layer network coding two-way relay network compute-and-forward lattice codes low-density lattice codes channel alignment

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Asynchronous Convolutional-Coded physical-layer network coding

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2015年第3期14卷 1380-1395页

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

This paper investigates the decoding process of asynchronous convolutional-coded physical-layer network coding (PNC) systems. Specifically, we put forth a layered decoding framework for convolutional-coded PNC consisting of three layers: symbol realignment layer, codeword realignment layer, and joint channel-decoding network coding (Jt-CNC) decoding layer. Our framework can deal with phase asynchrony (phase offset) and symbol arrival-time asynchrony (symbol misalignment) between the signals simultaneously transmitted by multiple sources. A salient feature of this framework is that it can handle both fractional and integral symbol misalignments. For the decoding layer, instead of Jt-CNC, previously proposed PNC decoding algorithms (e. g., XOR-CD and reduced-state Viterbi algorithms) can also be used with our framework to deal with general symbol misalignments. Our Jt-CNC algorithm, based on belief propagation, is BER-optimal for synchronous PNC and near optimal for asynchronous PNC. Extending beyond convolutional codes, we further generalize the Jt-CNC decoding algorithm for all cyclic codes. Our simulation shows that Jt-CNC outperforms the previously proposed XOR-CD algorithm and reduced-state Viterbi algorithm by 2 dB for synchronous PNC. For both phase-asynchronous and symbol-asynchronous PNC, Jt-CNC performs better than the other two algorithms. Importantly, for real wireless network experimentation, we implemented our decoding algorithm in a PNC prototype built on the USRP software radio platform. Our experiment shows that the proposed Jt-CNC decoder works well in practice.

关键词： physical-layer network coding convolutional codes symbol misalignment phase offset joint channel-decoding network coding cyclic codes

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Channel Decoding for Nonbinary physical-layer network coding in Two-Way Relay Systems

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2019年第1期68卷 628-640页

作者： Chen, Pingping Shi, Long Liew, Soung Chang Fang, Yi Cai, Kui Fuzhou Univ Dept Elect & Informat Fuzhou 350108 Fujian Peoples R China Singapore Univ Technol & Design Sci & Math Cluster Singapore 487372 Singapore Chinese Univ Hong Kong Dept Informat Engn Hong Kong Peoples R China Guangdong Univ Technol Sch Informat Engn Guangzhou 510006 Guangdong Peoples R China Southeast Univ Natl Mobile Commun Res Lab Nanjing 210096 Jiangsu Peoples R China

In this paper, we propose a generalized channel decoding scheme for nonbinary physical-layer network coding (CD-NC) in two-way relay channels (TWRCs), where two source nodes A and B exchange their nonbinary symbols via a relay. The two sources use the same nonbinary low-density parity-check (LDPC) channel code over the integer ring Z(M) and M-pulse-amplitude modulation, respectively. The existing channel decoding schemes for nonbinary network coding suffer severe rate loss compared with the cut-set bound of TWRC, especially in the low-to-medium signal-to-noise ratio regime. The proposed CD-NC can decrease the rate loss. Our contributions are as follows: 1) We develop a generalized nonbinary sum product algorithm (G-SPA) for CD-NC according to the principle of virtual encoding of the superimposed symbols. Simulation results show that our CD-NC can achieve significant performance gains over the conventional non-binary network coding for both additive white Gaussian noise and fading channels;and 2) We exploit two-dimensional fast-Fourier-transform-based belief propagation (2-D-FFT-BP) and extended min-sum (EMS) decoding algorithms to reduce the decoding complexity of G-SPA. Simulation results show that the 2-D-FFT-BP has the same performance asG-SPA, while EMS can greatly reduce the decoding complexity of G-SPA at the cost of slight performance degradation.

关键词： physical-layer network coding two-way relay channel (TWRC) nonbinary LDPC channel decoding

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Relay denoising mapping approach design and performance analysis for heterogeneous physical-layer network coding with high-order modulation

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IET COMMUNICATIONS 2020年第10期14卷 1571-1580页

作者： Chen, Sixuan Zou, Weixia Zhou, Zheng Cui, Mingyang Beijing Univ Posts & Telecommun Key Lab Universal Wireless Commun MOE Beijing 100876 Peoples R China Southeast Univ State Key Lab Millimeter Waves Nanjing 210096 Peoples R China

In recent years, considerable studies have been devoted to physical-layer network coding (PLNC) in a two-way relay channel (TWRC) network with the symmetric channel. However, it may not be appropriate for the asymmetric channel in which the source-to-relay channels are not equally strong and the two sources may utilise different modulation. In this study, the authors studied the heterogeneous PLNC design in the asymmetric TWRC network with high-order modulation and proposed a relay denoising mapping approach to reduce the decoding error probability. Firstly, they put forward a cluster maximisation algorithm to enlarge one cluster by sucking the neighbour points, which satisfy the exclusive law. Then, based on this algorithm, they designed the heuristic nearest-neighbour denoising mapping (HNDM) approach. The HNDM algorithm divides the nearest neighbour superimposed constellation points into the same cluster as far as possible. Points in the same cluster are coded into a new symbol by a specific mapping that achieves a many-to-one mapping. Performance results are provided in terms of symbol error rate. Under diversity channel conditions, the performances of 16-quadrature amplitude modulator (16-QAM)-8-phase-shift keying and 16-QAM-quadrature phase-shift keying are evaluated.

关键词： network coding decoding error statistics quadrature amplitude modulation wireless channels phase shift keying denoising mapping approach design performance analysis physical-layer network coding high-order modulation considerable studies two-way relay channel network symmetric channel asymmetric channel source-to-relay channels different modulation heterogeneous PLNC design asymmetric TWRC network relay denoising mapping approach cluster maximisation algorithm neighbour points nearest-neighbour denoising mapping approach HNDM algorithm nearest neighbour specific mapping diversity channel conditions 16-quadrature amplitude modulator-8-phase-shift keying

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Implementation of DNN-Based physical-layer network coding

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2023年第6期72卷 7380-7394页

作者： Wang, Xuesong Lu, Lu Chinese Acad Sci Ctr Space Utilizat Key Lab Space Utilizat Technol & Engn Beijing 100094 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

physical-layer network coding (PNC) has been proposed to double the throughput of a wireless two-way relay network (TWRN) and has been adapted so that it can be applied in vehicular ad-hoc networks (VANETs). Deep neural network (DNN)-based physical-layer network coding (PNC) for the TWRN system has been studied in recent years, under the assumption that the channel state information (CSI) is available to the end nodes and the relay node. However, the state-of-the-art DNN-based PNC system was only feasible for theoretical simulations, and no practical system design has been studied. When moving from theory to practical wireless systems, there are two critical issues to tackle: 1) unlike conventional regularly shaped quadrature amplitude modulations (QAMs), the constellation points of a DNN-based PNC system's end nodes are irregular and unpredictable to the relay node;and 2) other than in high-precision simulations, the practical DNNbased PNC system's constellation points are not fixed, that is, there is usually a cluster of points that must be grouped together so that the transceiver's digital-to-analog converter (DAC) and analog-to-digital converter (ADC) can work properly. To solve the above issues, we proposed the DNN-PNC implementation that can be realized using the Universal Software Radio Peripheral (USRP) platform. The computational complexity of our simulated DNN-PNC is one order of magnitude smaller than that given in the literature, while maintaining a good bit error rate (BER). In the implementation phase, we find that the naturally-happened power imbalance between the two end nodes' signals in our implementation can significantly boost the PNC constellation recovery, and hence reduce the system BER. Our experimental results showed that the BER of DNN-PNC can be lower than 10(-4) when the signalto-noise ratio (SNR) is 16 dB for the 2-QAM case and 20 dB for the 4-QAM case, respectively. These results indicate that DNN-based PNC is feasible for VANET applica

关键词： physical-layer network coding deep neural network wireless channel orthogonal frequency division multiplexing

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Generalized Signal-Space Alignment Based physical-layer network coding for Distributed MIMO Systems

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IEEE ACCESS 2019年 7卷 48430-48444页

作者： Cheng, Hai Yuan, Xiaojun Yang, Tao Univ Elect Sci & Technol China Ctr Intelligent Networking & Commun Natl Key Lab Sci & Technol Commun Chengdu 611731 Sichuan Peoples R China Beijing Univ Aeronaut & Astronaut Beijing 100083 Peoples R China

We study an uplink distributed multiple-input-multiple-output (D-MIMO) system, where multiple users are served by multiple base stations (BSs) connected to a common central unit (CU). We propose a generalized signal-space alignment (SSA)-based physical-layer network coding (PNC) scheme, termed G-SSA-PNC. In G-SSA-PNC, the multi-antenna users encode their messages by using nested lattice coding, linearly precode the nested lattice codewords for SSA, and then broadcast to the multi-antenna BSs. The BSs linearly post-process the received signals to extract signals at certain aligned directions. PNC decoding is applied to those extracted signals to generate network-coded message combinations, and the decoded message combinations are then forwarded to the CU for user messages decoding. Compared with the original SSA-PNC scheme, our scheme is different in the following three aspects. First, the G-SSA-PNC employs an individual shaping lattice for nested lattice coding at each source, as in contrast to the use of a common shaping lattice in original SSA-PNC. Second, we derive the feasibility condition of PNC decoding under the new nested lattice coding scheme and show that the SSA precoding and the nested lattice coding needs to be jointly designed to meet the feasibility condition. Third, we formulate a sum rate maximization problem and propose a suboptimal solution to the problem. The numerical results demonstrate the superiority of the G-SSA-PNC in performance over the benchmark schemes, including original SSA-PNC, compress-and-forward, and interference alignment.

关键词： Distributed MIMO systems interference alignment nested lattice coding physical-layer network coding signal-space alignment

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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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User-Antenna Selection for physical-layer network coding Based on Euclidean Distance

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IEEE TRANSACTIONS ON COMMUNICATIONS 2019年第5期67卷 3363-3375页

作者： Kumar, Vaibhav Cardiff, Barry Flanagan, Mark F. Univ Coll Dublin Sch Elect & Elect Engn Dublin D04 V1W8 Ireland

In this paper, we present the error performance analysis of a multiple-input multiple-output (MIMO) physical-layer network coding (PNC) system with two different user-antenna selection (AS) schemes in asymmetric channel conditions. For the first antenna selection scheme (AS1), where the user antenna is selected in order to maximize the overall channel gain between the user and the relay, we give an explicit analytical proof that for binary modulations, the system achieves full diversity order of min(N-A, N-B) x N-R in the multiple-access (MA) phase, where N-A, N-B, and N-R denote the number of antennas at user A, user B, and relay R, respectively. We present a detailed investigation of the diversity order for the MIMO-PNC system with AS1 in the MA phase for any modulation order. A tight closed-form upper bound on the average SER is also derived for the special case when N-R = 1, which is valid for any modulation order. We show that in this case, the system fails to achieve transmit diversity in the MA phase, as the system diversity order drops to 1 irrespective of the number of transmit antennas at the user nodes. Additionally, we propose a Euclidean distance (ED) based user-antenna selection scheme (AS2) that outperforms the first scheme in terms of error performance. Moreover, by deriving upper and lower bounds on the diversity order for the MIMO-PNC system with AS2, we show that this system enjoys both transmit and receive diversity, achieving full diversity order of min(N-A, N-B) x N-R in the MA phase for any modulation order. Monte Carlo simulations are provided which confirm the correctness of the derived analytical results.

关键词： physical-layer network coding wireless two-way relaying MIMO antenna selection Euclidean distance

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