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Channel coding and Decoding in a Relay System Operated with physical-layer network coding

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2009年第5期27卷 788-796页

作者： Zhang, Shengli Liew, Soung-Chang Chinese Univ Hong Kong Dept Informat Engn Hong Kong Hong Kong Peoples R China Shenzhen Univ Dept Commun Engn Shenzhen Peoples R China

This paper investigates link-by-link channel-coded PNC (physical layer network coding), in which a critical process at the relay is to transform the superimposed channel-coded packets received from the two end nodes (plus noise), Y-3 = X-1 + X-2+W-3, to the network-coded combination of the source packets, S-1 circle plus S-2. This is in contrast to the traditional multiple-access problem, in which the goal is to obtain both S-1 and S-2 explicitly at the relay node. Trying to obtain S-1 and S-2 explicitly is an overkill if we are only interested in S-1 circle plus S-2. In this paper, we refer to the transformation Y-3 -> S-1 circle plus S-2 as the Channel-decoding-network-coding process (CNC) in that it involves both channel decoding and network coding operations. This paper shows that if we adopt the Repeat Accumulate (RA) channel code at the two end nodes, then there is a compatible decoder at the relay that can perform the transformation Y-3 -> S-1 circle plus S-2 efficiently. Specifically, we redesign the belief propagation decoding algorithm of the RA code for traditional point-to-point channel to suit the need of the PNC multiple-access channel. Simulation results show that our new scheme outperforms the previously proposed schemes significantly in terms of BER without added complexity.

关键词： physical layer network coding channel coding belief propagation repeat accumulate code

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A physical layer network coding Based Modify-and-Forward with Opportunistic Secure Cooperative Transmission Protocol

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MOBILE networkS & APPLICATIONS 2019年第2期24卷 464-479页

作者： Quoc-Tuan Vien Tuan Anh Le Nguyen, Huan X. Tho Le-Ngoc Middlesex Univ Fac Sci & Technol London England McGill Univ Dept Elect & Comp Engn Montreal PQ Canada

This paper investigates a new secure relaying scheme, namely physical layer network coding based modify-and-forward (PMF), in which a relay node linearly combines the decoded data sent by a source node with an encrypted key before conveying the mixed data to a destination node. We first derive the general expression for the generalized secrecy outage probability (GSOP) of the PMF scheme and then use it to analyse the GSOP performance of various relaying and direct transmission strategies. The GSOP performance comparison indicates that these transmission strategies offer different advantages depending on the channel conditions and target secrecy rates, and relaying is not always desirable in terms of secrecy. Subsequently, we develop an opportunistic secure transmission protocol for cooperative wireless relay networks and formulate an optimisation problem to determine secrecy rate thresholds (SRTs) to dynamically select the optimal transmission strategy for achieving the lowest GSOP. The conditions for the existence of the SRTs are derived for various channel scenarios.

关键词： Wireless relay networks physical layer network coding Decode-and-forward Modify-and-forward Cooperative jamming

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Wireless Bidirectional Relaying Using physical layer network coding With Heterogeneous PSK Modulation

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2018年第3期67卷 2335-2344页

作者： Arunachala, Chinmayananda Buch, Saket D. Rajan, B. Sundar Indian Inst Sci Dept Elect Commun Engn Bengaluru 560012 India Indian Inst Sci Dept Elect Engn Bengaluru 560012 India ISRO Space Applicat Ctr Ahmadabad 380015 Gujarat India

In bidirectional relaying using physical layer network coding (PLNC), it is generally assumed that users employ same modulation schemes in the multiple access phase. It may not be desirable for the users to always use the same modulation schemes, particularly when user-relay channels are not equally strong. Such a scheme is called heterogeneous PLNC where users employ different modulation schemes. In this paper, we provide a general analytical framework to find the network coding maps to be used at the relay during the broadcast phase, when the users employ heterogeneous, but symmetric phase-shift keying modulations. The fade state plane is partitioned into regions, where given network coding maps are employed. This partition has been obtained analytically, which is computationally efficient when compared to the computationally intensive approach taken by Zhang et al. which uses brute force computer-based search. Performance results are provided in terms of relay error rate and bit error rate.

关键词： Latin rectangles physical layer network coding wireless two-way relaying

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On the Use of Cooperative physical layer network coding for Energy Efficient Routing

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IEEE TRANSACTIONS ON COMMUNICATIONS 2013年第4期61卷 1498-1509页

作者： Akhtar, Auon Muhammad Nakhai, Mohammad Reza Aghvami, A. Hamid Kings Coll London Inst Telecommun London England

In this paper, we focus on energy efficient routing in wireless ad hoc networks. We exploit modulo combining of continuous-time signals arriving at a receiving node from a number of synchronized transmitting nodes and introduce a cooperative physical layer network coding (CPLNC) scheme. To demonstrate the effectiveness of the proposed scheme in reducing energy consumption, we propose two routing algorithms that utilize CPLNC as a basic building block. Through analysis, we show that with sufficiently long packets, the proposed algorithms can achieve energy saving gains of up to 37% and 62% with respect to the conventional shortest-path routing algorithm in regular line and grid networks, respectively, using less number of hops. We incorporate CPLNC into two major energy efficient routing algorithms and derive threshold distances that enable the current node to intelligently decide whether it should use CPLNC or point to point transmission to the next hop. Simulation results confirm that the proposed and the modified algorithms based on CPLNC outperform their conventional counterparts in terms of achieving significant energy saving gains in networks of randomly distributed nodes.

关键词： Cooperative transmission energy efficiency physical layer network coding Rayleigh fading routing wireless ad hoc networks

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Analysis of Channel Estimation Error in physical layer network coding

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IEEE COMMUNICATIONS LETTERS 2011年第10期15卷 1029-1031页

作者： Yasami, Keyvan Razi, Abolfazl Abedi, Ali Univ Maine Dept Elect & Comp Engn Orono ME 04469 USA

This article investigates the effect of erroneous channel estimation on performance of physical layer network coding over fading channels. In this scenario, the relay maps the superimposed noisy modulated data, received from the two end terminals, to network coded combination of the source packets. We consider channel estimation error to be Gaussian distributed and formulate the network coding error by the distance between real and estimated points in the channel coefficients plane. Using this model, we present a statistical lower bound on variance of estimation error that can be tolerated by the relay terminal without imposing a network coding error on the system.

关键词： Channel estimation error physical layer network coding cooperative relaying network throughput

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Space-Time Coded Spatial Modulated physical layer network coding for Two-Way Relaying

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2015年第1期14卷 331-342页

作者： Unnikrishnan, K. G. Rajan, B. Sundar Indian Inst Sci Dept Elect Commun Engn Bangalore 560012 Karnataka India

Using the spatial modulation approach, where only one transmit antenna is active at a time, we propose two transmission schemes for two-way relay channel using physical layer network coding with space time coding using coordinate interleaved orthogonal designs (CIODs). It is shown that using two uncorrelated transmit antennas at the nodes, but using only one RF transmit chain and space-time coding across these antennas can give a better performance without using any extra resources and without increasing the hardware implementation cost and complexity. In the first transmission scheme, two antennas are used only at the relay, adaptive network coding (ANC) is employed at the relay and the relay transmits a CIOD space time block code (STBC). This gives a better performance compared to an existing ANC scheme for two-way relay channel which uses one antenna each at all the three nodes. It is shown that for this scheme at high SNR the average end-to-end symbol error probability (SEP) is upper bounded by twice the SEP of a point-to-point fading channel. In the second transmission scheme, two transmit antennas are used at all the three nodes, CIOD STBCs are transmitted in multiple access and broadcast phases. This scheme provides a diversity order of two for the average end-to-end SEP with an increased decoding complexity of O(M-3) for an arbitrary signal set and O(M-2 root M) for square QAM signal set. Simulation results show that the proposed schemes performs better than the existing ANC schemes under perfect and imperfect channel state information.

关键词： Coordinate interleaved orthogonal designs denoise-and-forward physical layer network coding spatial modulation wireless two-way relaying

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Optimal energy-efficient scheme for two-way relay channel using physical layer network coding

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The Journal of China Universities of Posts and Telecommunications 2011年第6期18卷 51-58页

作者： ZHOU Min CUI Qi-mei WANG Hui TAO Xiao-feng TIAN Hui MIKKO Valkama Key Laboratory of Universal Wireless Communications Beijing University of Posts and Telecommunications Beijing 100876 China Department of Communications Engineering Tampere University of Technology Tampere PF1-33101 Finland

Systems are always designed and optimized based on full traffic load in the current literatures. However, practical systems are seldom operating at full load, even at peak traffic hours. Instead of maximizing system rate to achieve the full load, an optimal energy-efficient scheme to minimize the transmit power with required rates is investigated in this article. The considered scenario is a two-way relay channel using amplify-and-forward protocol of physical layer network coding, where two end nodes exchange messages via multiple relay nodes within two timeslots. A joint power allocation and relay selection scheme is designed to achieve the minimum transmit power. Through convex optimization theory, we firstly prove that single relay selection scheme is the most energy-efficient way for physical layer network coding. The closed-form expressions of power allocation are also given. Numerical simulations demonstrate the performance of the designed scheme as well as the comparison among different schemes.

关键词： energy-efficient two-way relay channel physical layer network coding power allocation relay selection rate constraints

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Analysis and Implementation of Asynchronous physical layer network coding

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2015年第12期14卷 6595-6607页

作者： Marcum, Andrew C. Krogmeier, James V. Love, David J. Sprintson, Alex Purdue Univ Sch Elect & Comp Engn W Lafayette IN 47907 USA Raytheon Co Waltham MA 02451 USA Texas A&M Univ Dept Elect & Comp Engn College Stn TX 77843 USA

physical layer network coding has attracted extensive theoretical interest, although relatively little research has been done in support of deployment to wireless networks where internode synchronization is difficult to achieve. In particular, wireless networks constructed with inexpensive and commercially available software defined radio technology, or more generally, radio front-end samplers connected to internet-based remote processors (i.e., the Internet of Things network) may exhibit large time, frequency, and phase offsets that are difficult to control. In this paper, we define an asynchronous discrete-time model that accounts for these impairments as part of the information transfer between network users and a relay. Derived from this model are maximum likelihood algorithms for relay parameter estimation and a symbol decoder inspired from asynchronous multi-user detection. Additionally, null space-based frequency offset estimation that reduces computational complexity is proposed. Simulation results and the design and performance of a two-user system implemented with the Universal Software Radio Peripheral (USRP) platform and GNU radio are included to demonstrate the proof of concept. Our results indicate that the physical layer network coding technique can be successfully deployed and yields significant benefits even in the presence of impairments found in practical settings.

关键词： physical layer network coding software defined radio estimation synchronization

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Performance Analysis of Adaptive physical layer network coding for Wireless Two-Way Relaying

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第3期12卷 1328-1339页

作者： Muralidharan, Vijayvaradharaj T. Rajan, B. Sundar Indian Inst Sci Dept Elect Commun Engn Bangalore 560012 Karnataka India

The performance analysis of adaptive physical layer network-coded two-way relaying scenario is presented which employs two phases: Multiple access (MA) phase and Broadcast (BC) phase. The deep channel fade conditions which occur at the relay referred as the singular fade states fall in the following two classes: (i) removable and (ii) non-removable singular fade states. With every singular fade state, we associate an error probability that the relay transmits a wrong network-coded symbol during the BC phase. It is shown that adaptive network coding provides a coding gain over fixed network coding, by making the error probabilities associated with the removable singular fade states contributing to the average Symbol Error Rate (SER) fall as SNR-2 instead of SNR-1. A high SNR upper-bound on the average end-to-end SER for the adaptive network coding scheme is derived, for a Rician fading scenario, which is found to be tight through simulations. Specifically, it is shown that for the adaptive network coding scheme, the probability that the relay node transmits a wrong network-coded symbol is upper-bounded by twice the average SER of a point-to-point fading channel, at high SNR. Also, it is shown that in a Rician fading scenario, it suffices to remove the effect of only those singular fade states which contribute dominantly to the average SER.

关键词： Denoise-and-forward physical layer network coding wireless two-way relaying

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Performance Analysis of physical layer network coding in Massive MIMO Systems With M-QAM Modulations

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2021年第5期70卷 4631-4645页

作者： Okyere, Bismark Musavian, Leila Mumtaz, Rao Univ Essex Sch Comp Sci & Elect Engn CSEE Colchester CO4 3SQ Essex England GS Lda P-3750101 Agueda Portugal

In this paper, we develop a practical approach for deploying physical layer network coding (PNC) in multi-user M-Ary Quadrature Amplitude Modulation (M-QAM) Massive Multiple-Input Multiple-Output (MIMO) systems. We formulate a PNC mapping scheme as a function of clusters of estimated summation and difference (SD) of the transmitted symbols from user pairs. Utilizing existing linear detection schemes, such as Zero Forcing (ZF) and Minimum Mean Square Error (MMSE), a cluster of SD symbols are detected using an SD linearly transformed channel matrix. Furthermore, utilizing Maximum a Posteriori (MAP) soft decoding, the SD symbols are mapped to the PNC symbols, leveraging on the PNC symbol that maximizes the likelihood function. For each variant of M-QAM, we derive and simplify a specialization of the generalized PNC mapping function. The error performance results, through simulation, reveal that the proposed PNC scheme achieves twice the spectral efficiency in Massive MIMO, without changing the latter's underlying framework and without any degradation in the bit-error-rate (BER). In fact, our investigation has proved that the BER of the proposed Massive MIMO and PNC is slightly better than that of the conventional Massive MIMO. The feasibility of deploying our proposed PNC scheme in Massive MIMO systems paves way for NC applications to be realized in cellular systems.

关键词： Massive MIMO physical layer network coding End-to-end simulation

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