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作者： Tunali, Nihat Engin Texas A&M University

学位级别：Ph.D.

Compute-and-forward is a novel relaying paradigm in wireless communications in which relays in a network directly compute or decode functions of signals transmitted from multiple transmitters and forward them to a central destination. In this dissertation, we study three problems related to compute-and-forward. In the first problem, we consider the use of lattice codes for implementing a compute-and-forward protocol in wireless networks when channel state information is not available at the transmitter. We propose the use of lattice codes over Eisenstein integers and we prove the existence of a sequence of lattices over Eisenstein integers which are good for quantization and achieve capacity over an additive white Gaussian noise (AWGN) channel. Using this, we show that the information rates achievable with nested lattice codebooks over Eisenstein integers are higher than those achievable with nested lattice codebooks over integers considered by Nazer and Gastpar in [6] in the average sense. We also propose a separation-based framework for compute-and-forward that is based on the concatenation of a non-binary linear code with a modulation scheme derived from the ring of Eisenstein integers, which enables the coding gain and shaping gain to be separated, resulting in significantly higher theoretically achievable computation rates. In the second problem, we construct lattices based on spatially-coupled low-density parity check (LDPC) codes and empirically show that such lattices can approach the Poltyrev limit very closely for the point-to-point unconstrained AWGN channel. We then employ these lattices to implement a compute-and-forward protocol and empirically show that these lattices can approach the theoretically achievable rates closely. In the third problem, we present a new coding scheme based on concatenating a newly introduced class of lattice codes called convolutional lattice codes with LDPC codes, which we refer to as concatenated convolutional lattice codes

关键词： physical layer network coding lattices Thesis

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Design of Two Way Relay network Using Space-Time Block Coded network coding and Linear Detection

Design of Two Way Relay Network Using Space-Time Block Coded...

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IEEE 79th Vehicular Technology Conference (VTC-Spring)

作者： Duc Hiep Vu Van Bien Pham Xuan Nam Tran Chi Hieu Ta Le Quy Don Tech Univ Cau Giay Ha Noi Vietnam

ISBN: (纸本)9781479944828

This paper presents a design of two-way two-hop relay network using physical layer network coding (PNC) in which multiple antennas are used at all nodes. For transmission over the multiple-input multiple-output channels, the Alamouti's space-time block code (STBC) is used for transmission while linear detection is used for signal estimation at all nodes. In order to facilitate linear detection, we develop an equivalent multiuser STBC model for the proposed network and design the sum-and-difference matrix which is suitable for signal estimation. Simulation results show that the proposed network achieves diversity order 2 with polynomial complexity.

关键词： MIMO communication antenna arrays computational complexity matrix algebra network coding relay networks (telecommunication) signal processing space-time block codes Alamouti space-time block code MIMO channels PNC diversity order 2 equivalent multiuser STBC model linear detection multiple antennas multiple-input multiple-output channels physical layer network coding polynomial complexity signal estimation sum-and-difference matrix two-way two-hop relay network design Antennas Estimation MIMO network coding Relay networks (telecommunications) Vectors linear detection network coding Signal estimation space time block coding multiple antenna PNC MIMO communication matrix algebra Antenna arrays multiple input multiple output systems ANTENNA signal processing complexity classes Relay networks

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physical layer network-coded MAC strategy

Physical layer network-coded MAC strategy

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International Conference on Cyberspace Technology (CCT 2014)

作者： Yu Zhang Ge Xiong School of Computer and Communication Engineering University of Science and Technology Beijing 100083 China School of Software Beihang University 100191 China

ISBN: (纸本)9781510802704

This paper introduces physical layer network coding into multiple access system and then proposes a physical layer network coded MAC strategy (PNC-MAC). The detail steps of the PNC-MAC are presented. To show the performance of the algorithm, we compare the throughput and average delay induced by the new algorithm with that by modified ALOHA strategy and tree algorithm via simulations. The results showed that when operated with our proposed PNC-MAC, multiple access system can achieve a larger throughput while the frames bear shorter average delay. Besides, in many users case, the throughput increases slightly while the average delay ascends drastically.

关键词： ALOHA strategy Medium access control physical layer network coding Tree algorithm Medium access control mean delay physical layer Multi access systems hierarchical network Throughput MAXIMUM ACCEPTABLE CONTAMINATION Media Access Protocol

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Multiple-source multiple-destinations relay channels with network coding

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IET COMMUNICATIONS 2013年第17期7卷 1958-1968页

作者： Luo, Chunbo McClean, Sally Parr, Gerard Ren, Peng Gong, Yu Univ West Scotland Sch Comp Paisley Renfrew Scotland Univ Ulster Sch Comp & Informat Engn Coleraine BT52 1SA Londonderry North Ireland China Univ Petr Huadong Coll Control & Informat Engn Qingdao Peoples R China Univ Loughborough Sch Elect Elect & Syst Engn Loughborough Leics England

The essential broadcasting feature of radio propagation channels provides an opportunity for multiple nodes to exchange information and work cooperatively, where each node, for example, mobile sensor or robot, plays both the role of transmitter and receiver. Especially in such machine-to-machine communication scenarios, the network performance and redundancy of information from different providers highly affect the work efficiency of each individual node and the whole system. To address these problems, a relay assisted centralised network model with physical layer network coding implemented in the relay is proposed in this study. This structure has the advantage of flexible data exchange and the capability to reduce redundancy in information. Its theoretical performance is analysed by the diversity multiplexing tradeoff, which proves the proposed model is versatile in reliable and high spectral-efficiency information exchange. Experiments of multiple nodes in a machine-to-machine scenario - unmanned aerial vehicles, further reveal its potential in improving efficiency of communication and cooperation.

关键词： broadcasting multiplexing redundancy telecommunication channels network coding autonomous aerial vehicles relay networks (telecommunication) multiple-source multiple-destinations relay channels radio propagation channels information exchange machine-to-machine communication scenarios network performance information redundancy relay assisted centralised network model physical layer network coding flexible data exchange diversity multiplexing tradeoff spectral-efflciency information exchange machine-to-machine scenario unmanned aerial vehicles

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A Compute-and-Forward Scheme for Gaussian Bi-Directional Relaying with Inter-Symbol Interference

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IEEE TRANSACTIONS ON COMMUNICATIONS 2013年第3期61卷 1011-1019页

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

We provide inner and outer bounds on the capacity region for the Gaussian bi-directional relaying over inter-symbol interference channels. The outer bound is obtained by the conventional cut-set argument. For the inner bound, we propose a compute-and-forward coding scheme based on lattice partition chains and study its achievable rate. The coding scheme is a time-domain coding scheme which uses a novel precoding scheme at the transmitter in combination with lattice precoding and a minimum mean squared error receiver to recover linear combinations of lattice codewords. The proposed compute-and-forward coding scheme substantially outperforms decode-and-forward schemes. While it is well known that for the point-to-point communication case, both independent coding along sub-channels and time-domain coding can approach the capacity limit, as a byproduct of the proposed scheme, we show that for the bi-directional relay case, independent coding along sub-channels is not optimal in general and joint coding across sub-channels can improve the capacity for some channel realizations.

关键词： Bi-directional relay channels two way relay channels compute and forward physical layer network coding and inter-symbol interference

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Wireless network coding for MIMO Two-Way Relaying

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第7期12卷 3566-3577页

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

The design of modulation schemes for the physical layer network-coded two-way MIMO relaying scenario is considered, with the denoise-and-forward protocol which employs two phases: Multiple Access phase and Broadcast phase. It is shown that for MIMO two-way relaying, the minimum distance of the effective constellation at the relay becomes zero when all the rows of the channel fade coefficient matrix belong to a finite number of vector subspaces referred to as the singular fade subspaces. The singular fade subspaces can be classified into two kinds based on whether their harmful effects can be removed or not: (i) the removable and (ii) the non-removable singular fade subspaces. It is shown that network coding maps obtained by the completion of appropriate partially filled Latin Rectangles can remove the harmful effects of all the removable singular fade subspaces. For 2(lambda)-PSK signal set, the removable and non-removable singular fade subspaces are characterized and, it is shown that the number of non-removable singular fade subspaces is a small fraction of the total number of singular fade subspaces and this fraction tends to zero as the constellation size tends to infinity. The Latin Rectangles for the case when the end nodes use different number of antennas are shown to be obtainable from the Latin Squares for the case when they use the same number of antennas. Also, the network coding maps which remove all the removable singular singular fade subspaces are shown to be obtainable from a small set of Latin Squares. The removal of all the singular fade subspaces by properly choosing the network coding map, provides a gain of 5.5 dB over the conventional Exclusive-OR network coding, in a Rayleigh fading scenario with 2 antennas at the end nodes and one antenna at the relay node, for 4-PSK signal set.

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

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Joint Channel Estimation and Decoding for Trellis-Coded MIMO Two-Way Relay networks

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2013年第8期31卷 1455-1468页

作者： Lehmann, Frederic Telecom SudParis Inst Telecom Dept CITI UMR CNRS 5157 F-91011 Evry France

We present a method for joint decode-and-forward physical layer network coding in two-way relay networks. The two source nodes send their packets simultaneously over time-varying channels to a relay node, then the relay broadcasts the received superimposed packets to the source nodes using network coding. The nodes use trellis coding for the sake of error correction and multi-antenna equipments to combat multipath fading. A challenging multiple access problem occurs at the relay node, which performs joint channel estimation and decoding for the individual source packets. We design message passing algorithms based on factor-graphs to solve this problem. The relay has two separate modules that perform channel estimation and decoding for the packets received from each source node. The interference generated by the other source node is taken into account by exchanging messages between the two modules.

关键词： Two-way relay network physical layer network coding time-varying MIMO channel trellis coding joint channel estimation and decoding message passing

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Wireless network-Coded Bidirectional Relaying Using Latin Squares for M-PSK Modulation

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IEEE TRANSACTIONS ON INFORMATION THEORY 2013年第10期59卷 6683-6711页

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

The design of modulation schemes for the physical layer network-coded two-way relaying scenario is considered with a protocol which employs two phases: multiple access (MA) phase and broadcast (BC) phase. It was observed by Koike-Akino et al. that adaptively changing the network coding map used at the relay according to the channel conditions greatly reduces the impact of MA interference which occurs at the relay during the MA phase and all these network coding maps should satisfy a requirement called the exclusive law. We show that every network coding map that satisfies the exclusive law is representable by a Latin Square and conversely, that this relationship can be used to get the network coding maps satisfying the exclusive law. The channel fade states for which the minimum distance of the effective constellation at the relay become zero are referred to as the singular fade states. For M - PSK modulation (M any power of 2), it is shown that there are (M-2/4 - M/2 + 1) M singular fade states. Also, it is shown that the constraints which the network coding maps should satisfy so that the harmful effects of the singular fade states are removed, can be viewed equivalently as partially filled Latin Squares (PFLS). The problem of finding all the required maps is reduced to finding a small set of maps for M - PSK constellations (any power of 2), obtained by the completion of PFLS. Even though the completability of M x M PFLS using M symbols is an open problem, specific cases where such a completion is always possible are identified and explicit construction procedures are provided. Having obtained the network coding maps, the set of all possible channel realizations (the complex plane) is quantized into a finite number of regions, with a specific network coding map chosen in a particular region. It is shown that the complex plane can be partitioned into two regions: a region in which any network coding map which satisfies the exclusive law gives the same best performa

关键词： Latin squares physical layer network coding wireless bidirectional relaying

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Subcarriers Suppression Methods for OFDM Systems with Decode-and-Forward network coding

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第12期12卷 6034-6042页

作者： Bartoli, Giulio Fantacci, Romano Marabissi, Dania Simoni, Renato Univ Florence Dept Informat Engn Florence Italy

This paper deals with the performance evaluation of Decode and Forward physical layer network coding schemes under multipath fading channel propagation conditions. physical layer network coding in Two Way Relay networks ideally allows to drastically increase the network throughput. However, under the assumption of actual channel propagation conditions, the performance quickly degrades due to high decoding error probability. With the aim of counteracting this drawback, the paper proposes a suitable approach for Orthogonal Frequency Division Multiplexing systems based on a signal pre-equalization technique. Furthermore, in order to lower the decoding error probability, three subcarriers suppression methods are introduced. These methods differ from each other for the performance achieved and the required amount of signaling that nodes have to exchange. An important result obtained here is that the combined use of channel inversion and subcarriers suppression allows to enhance the system reliability with a slight decrease of the throughput.

关键词： Decode and forward channel inversion OFDM physical layer network coding subcarriers suppression two way relay network

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Distributed Space Time coding for Wireless Two-Way Relaying

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2013年第4期61卷 980-991页

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

We consider the wireless two-way relay channel, in which two-way data transfer takes place between the end nodes with the help of a relay. For the Denoise-And-Forward (DNF) protocol, it was shown by Koike-Akino et al. that adaptively changing the network coding map used at the relay greatly reduces the impact of Multiple Access Interference at the relay. The harmful effect of the deep channel fade conditions can be effectively mitigated by proper choice of these network coding maps at the relay. Alternatively, in this paper we propose a Distributed Space Time coding (DSTC) scheme, which effectively removes most of the deep fade channel conditions at the transmitting nodes itself without any CSIT and without any need to adaptively change the network coding map used at the relay. It is shown that the deep fades occur when the channel fade coefficient vector falls in a finite number of vector subspaces of, which are referred to as the singular fade subspaces. DSTC design criterion referred to as the singularity minimization criterion under which the number of such vector subspaces are minimized is obtained. Also, a criterion to maximize the coding gain of the DSTC is obtained. Explicit low decoding complexity DSTC designs which satisfy the singularity minimization criterion and maximize the coding gain for QAM and PSK signal sets are provided. Simulation results show that at high Signal to Noise Ratio, the DSTC scheme provides large gains when compared to the conventional Exclusive OR network code and performs better than the adaptive network coding scheme.

关键词： Distributed space time coding physical layer network coding wireless two-way relaying

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