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Distributed MIMO Broadcasting: Reverse Compute-and-Forward and Signal-Space Alignment

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2017年第1期16卷 581-593页

作者： Yang, Tao Univ Technol Sydney Global Big Data Technol Ctr Ultimo NSW 2007 Australia

We study a downlink distributed MIMO system where a central unit (CU) broadcasts messages to K' users through K distributed BSs. The CU is connected to the BSs via K independent rate-constrained fronthaul (FH) links. The distributed BSs collectively serve the users through the air. We propose a new network coding based distributed MIMO broadcasting scheme, using reverse compute-and-forward and signal-space alignment. At the CU, a network coding generator matrix is employed for pre network coding of the users' messages. The network coded messages are forwarded to the BSs, where the FH rate-constraint determines the actual number of network-coded messages forwarded to the BSs. At the BSs, linear precoding matrices are designed to create a number of bins, each containing a bunch of spatial streams with aligned signal-spaces. At each user, post physical-layer network coding is employed to compute linear combinations over the NC messages with respect to the bins, which reverses the prenetwork coding and recovers the desired messages. We derive an achievable rate of the proposed scheme based on the existence of NC generator matrix, signal-space alignment precoding matrices, and nested lattice codes. Improved rate and degrees of freedom over existing interference alignment and compress-and-forward schemes are shown. Numerical results demonstrate the performance improvement, e.g., by as much as 70% increase in throughput over benchmark schemes.

关键词： Cloud RAN CoMP MIMO distributed MIMO broadcast channel physical-layer network coding compute-and-forward interference alignment

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Multiple-Input Multiple-Output Two-Way Relaying: A Space-Division Approach

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IEEE TRANSACTIONS ON INFORMATION THEORY 2013年第10期59卷 6421-6440页

作者： Yuan, Xiaojun Yang, Tao Collings, Iain B. Chinese Univ Hong Kong Inst Network Coding Hong Kong Hong Kong Peoples R China CSIRO ICT Ctr Marsfield NSW 2122 Australia

We propose a novel space-division-based network-coding scheme for multiple-input multiple-output (MIMO) two-way relay channels (TWRCs), in which two multiantenna users exchange information via a multiantenna relay. In the proposed scheme, the overall signal space at the relay is divided into two subspaces. In one subspace, the spatial streams of the two users have nearly orthogonal directions and are completely decoded at the relay. In the other subspace, the signal directions of the two users are nearly parallel, and linear functions of the spatial streams are computed at the relay, following the principle of physical-layer network coding. Based on the recovered messages and message-functions, the relay generates and forwards network-coded messages to the two users. We show that, at high signal-to-noise ratio, the proposed scheme achieves the asymptotic sum-rate capacity of the MIMO TWRC within 1/2 log (5/4) approximate to 0.161 bits per user-antenna, for any antenna configuration and any channel realization. We perform large-system analysis to derive the average sum-rate of the proposed scheme over Rayleigh-fading MIMO TWRCs. We show that the average asymptotic sum-rate gap to the capacity is at most 0.053 bits per relay-antenna. It is demonstrated that the proposed scheme significantly outperforms the existing schemes.

关键词： Multiple-input multiple-output (MIMO) physical-layer network coding space-division precoding two-way relay channel (TWRC)

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Improving LDPC-Coded PNC Decoders via Informed Dynamic Scheduling

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IEEE COMMUNICATIONS LETTERS 2023年第8期27卷 1949-1953页

作者： Huang, Caizheng Chen, Pingping Xie, Zhaopeng Fang, Yi Fuzhou Univ Dept Elect Informat Fuzhou 350108 Fujian Peoples R China Singapore Univ Technol & Design Dept Math Singapore 487372 Singapore Guangdong Univ Technol Sch Informat Engn Guangzhou 510006 Peoples R China

To decode the transmit message pairs and then obtain the exclusive OR (XOR) message, this letter proposes the double-reliability-based decoding (DRB) algorithms with informed dynamic scheduling (IDS) for low-density parity-check (LDPC) coded physical-layer network coding (PNC) systems. The proposed DRB decoding with informed stability (IS-DRB) utilizes a new stability measure to determine the update order of the check nodes. Moreover, by exploiting the principle of PNC decoding, we present an improved IS-DRB (IIS-DRB) decoding to select the check node with unsatisfied PNC mapped checksum and the large stability to update first. This is due to that message propagated from this check node can quickly correct the variable node that causes unsatisfied checksum. Simulation results show that the proposed algorithms can realize significant performance improvement of about 0.5 dB over the conventional DRB decoding with the limited increase in complexity.

关键词： physical-layer network coding low-density parity-check codes informed dynamic scheduling

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Design of CPM-PNC Using the Titled-Phase Model over AWGN Channels

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2019年第2期E102A卷 476-479页

作者： Sha, Nan Guo, Mingxi Gao, Yuanyuan Chen, Lihua Xu, Kui Army Engn Univ PLA Commun Engn Coll Nanjing 210007 Jiangsu Peoples R China

In this letter, a physical-layer network coding (PNC) scheme based on continuous phase modulation (CPM) signal using the titled-phase model, i.e., TIP-CPM-PNC, is presented, and the combined titled-phase state trellis for the superimposed CPM signal in TIP-CPM-PNC is discussed. Simulation results show that the proposed scheme with low decoding complexity can achieve the same error performance as CPM-PNC using the traditional-phase model.

关键词： physical-layer network coding continuous phase modulation titled-phase decoding complexity

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Lattices Over Algebraic Integers With an Application to Compute-and-Forward

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IEEE TRANSACTIONS ON INFORMATION THEORY 2018年第10期64卷 6863-6877页

作者： Huang, Yu-Chih Narayanan, Krishna R. Wang, Ping-Chung Natl Taipei Univ Dept Commun Engn New Taipei 23741 Taiwan Texas A&M Univ Dept Elect & Comp Engn College Stn TX 77843 USA Intel Corp San Diego CA 92131 USA

In this paper, we extend Construction A of lattices to the ring of algebraic integers of a general imaginary quadratic field that may not form a principal ideal domain (PID). We show that such a construction can produce good lattices for coding in the sense of Poltyrev and for MSE quantization. As an application, we then apply the proposed lattices to the compute-and-forward paradigm with limited feedback. Without feedback, compute-and-forward is typically realized with lattice codes over the ring of integers, the ring of Gaussian integers, or the ring of Eisenstein integers, which are all PIDs. A novel scheme called adaptive compute-and-forward is proposed to exploit the limited feedback about the channel state by working with the best ring of imaginary quadratic integers. Simulation results show that by adaptively choosing the best ring among the considered ones according to the limited feedback, the proposed adaptive compute-and-forward provides a better performance than that provided by the conventional compute-and-forward scheme which works over Gaussian or Eisenstein integers solely.

关键词： Algebraic integers compute-and-forward lattice codes physical-layer network coding

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MIMO Multiway Relaying With Clustered Full Data Exchange: Signal Space Alignment and Degrees of Freedom

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2014年第12期13卷 6795-6808页

作者： Yuan, Xiaojun ShanghaiTech Univ Sch Informat Sci & Technol Shanghai 200031 Peoples R China

Recently, much research interest has been focused on the design of efficient communication mechanisms for multiple-input-multiple-output (MIMO) multiway relay channels (mRCs). In this paper, we investigate achievable degrees of freedom (DoFs) of the MIMO mRC with L clusters and K users per cluster, where each user is equipped with M antennas and the relay with N antennas. Our analysis is focused on a new data exchange model, termed clustered full data exchange, i.e., each user in a cluster wants to learn the messages of all the other users in the same cluster. Novel signal alignment techniques are developed to jointly and systematically construct the beamforming matrices at the users and the relay for efficient implementation of physical-layer network coding. Based on this, we derive an achievable DoF of the MIMO mRC with an arbitrary network configuration of L and K, as well as with an arbitrary antenna configuration of M and N. We show that our proposed scheme achieves the DoF capacity when M/N <= 1/(LK - 1) and M/N >= ((K - 1) L + 1)/KL. The DoF results derived in this paper can serve as fundamental benchmarks in evaluating the performance of practical communication systems over MIMO mRCs and provide guidance and insights into the design of wireless relay networks.

关键词： Multiway relay channels degrees of freedom multiple-input multiple-output systems physical-layer network coding signal and interference alignment

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Power allocation based on SEP minimisation in three-user two-way channel

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IET COMMUNICATIONS 2019年第15期13卷 2327-2335页

作者： Jin, Xianglan Pusan Natl Univ Dept Elect & Comp Engn Busan 46241 South Korea

A three-user two-way channel in which three users exchange their messages through a two-way communication is considered by applying the physical-layer network coding and the superposition coding. The equivalent squared minimum distance (ESMD) is derived as a criterion for power allocation by analysing the average symbol error probability (SEP). Optimal and suboptimal power allocations are proposed based on the ESMD maximisation under total power constraint. Inspired by the result, a proportional power allocation is proposed under per-node power constraint. This scheme improves SEP at high signal-to-noise ratio (SNR) and consumes significantly less power. The average power consumption for each node is mathematically derived as a closed form. Furthermore, a compensation algorithm is introduced, which saves power and simultaneously achieves remarkable SEP improvement over entire SNR range. The numerical simulations over Rayleigh fading channels confirm the superiority of the proposed algorithms.

关键词： fading channels network coding error statistics Rayleigh channels physical-layer network coding superposition coding equivalent squared minimum distance average symbol error probability suboptimal power allocations ESMD maximisation total power constraint proportional power allocation per-node power constraint high signal-to-noise ratio average power consumption remarkable SEP improvement Rayleigh fading channels SEP minimisation

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Transmit power minimisation for full-duplex two-way relaying systems with asymmetric packet-rates and quality-of-service requirements

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IET COMMUNICATIONS 2020年第13期14卷 2098-2109页

作者： Qian, Chong Ji, Xiaodong Cao, Zhanghua Li, Wenhua Nantong Univ Sch Informat Sci & Technol Nantong 226019 Peoples R China Wenluo Corp Elect Sci & Technol Jiangsu Nantong 226019 Peoples R China

This study solves the transmit power minimisation problem subject to a target quality-of-service constraint of a full-duplex (FD) two-way decode-and-forward relaying system with asymmetric packet-rates, where the two-way relaying system can operate in two different styles, i.e. half-duplex sources with full-duplex relaying (HDS-FDR) and full-duplex sources with full-duplex relaying (FDS-FDR) styles. For the FDS-FDR style, the relay node can use two strategies to handle the received signals from the sources, namely, physical-layer network coding (PNC) and physical-layer superposition coding (PSC), both of which are referred to as FDS-FDR-PNC and FDS-FDR-PSC styles, respectively. By transforming the transmit power minimisation problem into a two-stage problem, optimum power control (OPC) techniques are developed for the HDS-FDR, FDS-FDR-PNC and FDS-FDR-PSC styles, respectively, giving closed-form solutions for individual transmit power at the relay and the sources. Computer simulations are conducted and the results validate the proposed OPC techniques. It is shown that the FDS-FDR-PNC style performs best in terms of energy saving when the two sources' packet-rates are moderately asymmetric or symmetric. For the case that the packet-rates are strongly asymmetric, the FDS-FDR-PSC style can save more energy than the other two styles.

关键词： relay networks (telecommunication) power control network coding quality of service telecommunication control decode and forward communication HDS-FDR FDS-FDR-PSC style individual transmit power FDS-FDR-PNC style asymmetric packet-rates quality-of-service requirements transmit power minimisation problem subject target quality-of-service constraint half-duplex sources full-duplex sources full-duplex relaying styles FDS-FDR style relay node physical-layer superposition coding optimum power control techniques full-duplex two-way decode-and-forward relaying system physical-layer network coding

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Node Symbol Timing Error Estimator for physical-layer network-Coded Relay

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2015年第12期E98A卷 2733-2737页

作者： Dang, Xiaoyu Li, Qiang Xiao, Hao Wan, Cheng Nanjing Univ Aeronaut & Astronaut Dept Elect Informat Engn Nanjing Jiangsu Peoples R China

network coding on the physical-layer has recently been widely discussed as a potentially promising solution to the wireless access problem in a relay network. However, the existing research on physical-layer network coding (PNC), usually assumes that the symbol timing of the nodes is fully synchronized and hardly investigates the unavoidable symbol timing errors. Similar to many telecommunication systems, symbol timing plays a critical role in PNC and precise alignment has to be provided for the encoding. In this work, we propose a novel symbol timing algorithm with a low oversampling factor (samples per symbol) based on the a priori knowledge of the transmitted pulse shape. The proposed algorithm has the dual advantages of the low oversampling rate and high precision. The mean square error (MSE) performance is verified by simulations to be at least one order of magnitude better than that of the conventional optimum phase (OP) algorithm for a signal noise ratio (SNR) greater than 5 dB.

关键词： physical-layer network coding two-way relay channels symbol timing estimation pulse shape

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Beyond Integer-Forcing Receiver for Lattice-Code Based Multi-User MIMO System

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IEEE COMMUNICATIONS LETTERS 2023年第10期27卷 2553-2557页

作者： Yang, Tao Beihang Univ Sch Elect & Informat Engn Beijing 100191 Peoples R China

This letter studies a lattice-code based multi-user MIMO system. In the uplink, K single-antenna users encode their messages with the same q -ary linear code mapped to q -PAM, belonging to the ensemble of lattice codes. The NR -antenna receiver attempts to compute K independent streams of integer-combinations (ICBs) of the users' messages. To this end, we put forth a new interference-whitening (IW) based ICB detection method, which reduces the loss of the linear filtering operation in existing integer-forcing (IF). The soft detection outputs are forwarded to K channel-code decoders to recover the messages. For practical configurations with moderate-to-large K , the proposed ICB detection exhibits an enlarged achievable mutual information and considerably improved FER performance, over existing IF.

关键词： Receivers Lattices MIMO communication Codes Linear codes Iterative decoding Indexes Multiple access multi-user MIMO massive access lattice-codes compute-forward physical-layer network coding iterative decoding soft detection

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