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The Dirty MIMO Multiple-Access Channel

IEEE TRANSACTIONS ON INFORMATION THEORY 2017年第9期63卷 6031-6040页

作者： Khina, Anatoly Kochman, Yuval Erez, Uri Tel Aviv Univ Dept Elect Engn Syst IL-69978 Tel Aviv Israel CALTECH Dept Elect Engn Pasadena CA 91125 USA Hebrew Univ Jerusalem Rachel & Selim Benin Sch Comp Sci & Engn IL-91904 Jerusalem Israel

In the scalar dirty multiple-access channel, in addition to Gaussian noise, two additive interference signals are present, each known non-causally to a single transmitter. It was shown by Philosof et al. that for strong interferences, an independent identically distributed ensemble of codes does not achieve the capacity region. Rather, a structured-codes approach was presented that was shown to be optimal in the limit of high signal-to-noise ratios, where the sum capacity is dictated by the minimal ("bottleneck") channel gain. In this paper, we consider the multiple-input multiple-output (MIMO) variant of this setting. In order to incorporate structured codes in this case, one can utilize matrix decompositions that transform the channel into effective parallel scalar dirty multiple-access channels. This approach, however, suffers from a "bottleneck" effect for each effective scalar channel and, therefore, the achievable rates strongly depend on the chosen decomposition. It is shown that a recently proposed decomposition, where the diagonals of the effective channel matrices are equal up to a scaling factor, is optimal at high signal-to-noise ratios, under an equal rank assumption. This approach is then extended to any number of transmitters. Finally, an application to physical-layer network coding for the MIMO two-way relay channel is presented.

关键词： Multiple-access channel dirty-paper coding multiple-input multiple-output channel matrix decomposition physical-layer network coding two-way relay channel

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Multi-Pair MIMO Two-Way Relaying: A Principal-Angle Perspective

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2016年第2期64卷 380-394页

作者： Xin, Haiyang Yuan, Xiaojun Liew, Soung-Chang Chinese Univ Hong Kong Dept Informat Engn Hong Kong Hong Kong Peoples R China ShanghaiTech Univ Sch Informat Sci & Technol Shanghai 200031 Peoples R China

This paper studies and analyzes a multi-pair MIMO two-way relay (TWR) system from a principal-angle perspective. In this system, users are grouped into pairs and two users in each pair exchange information through a common relay. The transmission scheme consists of two phases. In the uplink phase, the relay's receive signal space is divided into two subspaces for each pair: in one subspace, the signals of the two users are near-parallel, and physical-layer network coding (PNC) decoding is applied to retrieve network-coded messages;in the other subspace, the two user signals are near-orthogonal, and complete decoding (CD) is applied to retrieve individual user messages. In the downlink phase, the relay's transmit signal space is split into orthogonal subspaces for each pair, and in each subspace a common message is broadcasted to the two users. Our main contribution is to establish a critical link between the transmission scheme and the concept of principal angle in linear algebra. In particular, principal angle quantizes the degree of orthogonality between the user signals and helps determining how to partition the relay's receive signal space into PNC decoding subspace and CD decoding subspace. Building on that, we discuss the optimal design of user/relay precoders for both uplink and downlink phases to maximize the asymptotic sum-rate of the proposed scheme at high signal-to-noise ratio (SNR). The analysis and numerical results indicate that our scheme performs close to the cut-set outer bound and significantly outperforms the existing schemes in the literature.

关键词： Multi-input multi-output physical-layer network coding principal angles/vectors two-way relay channel

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physical-layer Secret Key Agreement in Two-Way Wireless Relaying Systems

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IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY 2011年第3期6卷 650-660页

作者： Shimizu, Takayuki Iwai, Hisato Sasaoka, Hideichi Doshisha Univ Grad Sch Engn Kyotanabe 6100394 Japan

We consider secret key agreement based on radio propagation characteristics in a two-way relaying system where two legitimate parties named Alice and Bob communicate with each other via a trusted relay. In this system, Alice and Bob share secret keys generated from measured radio propagation characteristics with the help of the relay in the presence of an eavesdropper. We present four secret key agreement schemes: an amplify-and-forward (AF) scheme, a signal-combining amplify-and-forward (SC-AF) scheme, a multiple-access amplify-and-forward (MA-AF) scheme, and an amplify-and-forward with artificial noise (AF with AN) scheme. In these schemes, the basic idea is to share the effective fading coefficients between Alice and Bob and use them as the source of the secret keys. The AF scheme is based on a conventional amplify-and-forward two-way relaying method, whereas in the SC-AF scheme and the MA-AF scheme, we apply the idea of physical-layer network coding to the secret key agreement. In the AF with AN scheme, the relay transmits artificially generated noise, as well as channel information signal, in order to conceal the latter. Simulation results show that the MA-AF scheme outperforms the other schemes in Rayleigh fading channels, whereas the AF with AN scheme is suitable for Rician fading channels.

关键词： physical-layer network coding physical-layer security radio propagation secret key agreement two-way relaying

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network-Coded Multiple Access II: Toward Real-Time Operation With Improved Performance

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2015年第2期33卷 264-280页

作者： You, Lizhao Liew, Soung Chang Lu, Lu Chinese Univ Hong Kong Dept Informat Engn Shatin Hong Kong Peoples R China Chinese Univ Hong Kong Inst Network Coding Shatin Hong Kong Peoples R China

This paper presents a first real-time network-coded multiple access (NCMA) system that jointly exploits physical (PHY)-layer network coding (PNC) and multiuser decoding (MUD) to boost the throughput of a wireless local area network (WLAN). NCMA is a new design paradigm for multipacket reception wireless networks, in which the access point can receive and decode several packets simultaneously transmitted by multiple users. Conventionally, multipacket reception is realized using MUD only, whereas the key idea of NCMA is to use PNC together with MUD to realize multipacket reception. Although the feasibility of NCMA has previously been studied by the authors, our previous NCMA prototype was a version with offline signal processing. In addition, our previous investigation left open a number of theoretical and implementation issues, the resolution of which is critical to the adoption of NCMA in real practice. The current investigation makes the following state-of-the-art contributions toward NCMA: 1) we demonstrate a first NCMA system with integrated real-time PHY- and MAC-layer decoding;2) we construct a new unified framework for MAC-layer decoding that yields higher throughput with faster decoding-the faster decoding is one of the key enablers of our real-time implementation;and 3) we design new PHY-layer decoding techniques that overcome the poor performance of the first-generation NCMA prototype at low SNR. Experimental results show that, compared with the previous NCMA prototype, our new NCMA prototype improves real-time throughput by more than 100% at medium-high SNR (>= 8 dB).

关键词： network coding physical-layer network coding multiuser detection multiple access network-coded multiple access implementation

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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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Exploiting Interference for Intelligent Relaying in Integrated Space and Terrestrial networks Based on PNC and SIC

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MOBILE networkS & APPLICATIONS 2019年第6期24卷 1947-1954页

作者： Wang, Hailong Wang, Gang Li, Bo Liu, Gongliang Lu, Weidang Harbin Inst Technol Commun Res Ctr Harbin Peoples R China Harbin Inst Technol Weihai Sch Informat Sci & Engn Weihai Peoples R China Zhejiang Univ Technol Coll Informat Engn Hangzhou Peoples R China

The integrated space and terrestrial networks which incorporate various satellite systems and ground networks could provide a wide variety of services and global seamless network access. The integrated network is composed of multiple heterogeneous nodes and sub-networks which requires intelligent and efficient physical layer transmission techniques to maintain high-speed links between these subsystems. As a traditional technology in satellite communications, relay could still work as an important part in these heterogeneous and complex networks. In this paper, two interference exploitation schemes, i.e., physical-layer network coding (PNC) and successive interference cancellation (SIC) which can efficiently increase data exchange rate for relay systems are studied, and an intelligent relaying scheme combining both the advantages of these two schemes is proposed. Simulation results show the proposed adaptive transmission scheme achieves a smoother sum-rate gain while being more robust to dynamic topologies.

关键词： Integrated space and terrestrial networks physical-layer network coding Successive interference cancellation Intelligent relaying

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Optimal DoF Region for the Asymmetric Two-Pair MIMO Two-Way Relay Channel

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2017年第7期65卷 1700-1711页

作者： Liu, Kangqi Tao, Meixia Yuan, Xiaojun Shanghai Jiao Tong Univ Dept Elect Engn Shanghai 200240 Peoples R China ShanghaiTech Univ Sch Informat Sci & Technol Shanghai 201210 Peoples R China

In this paper, we study the optimal degrees of freedom (DoF) region for the two-pair MIMO two-way relay channel (TWRC) with asymmetric antenna setting, where two pairs of users exchange information with the help of a common relay. Each user i is equipped with M-i antennas, for i = 1, 2, 3, 4, and the relay is equipped with N antennas. First, we prove the converse of the DoF region by using the cut-set theoremand the genie-message approach. Then, we present new transmission schemes to achieve the optimal DoF region at different antenna configurations. Due to the asymmetric data exchange, where the two users in each pair can communicate a different number of data streams, we not only need to form the network-coded symbols but also need to process the additional asymmetric data streams at the relay. This is realized through the joint design of relay compression matrix and source precoding matrices. After obtaining the optimal DoF region, we study the optimal sum DoF by solving a linear programing problem. Our DoF analysis reveals that in the asymmetric antenna setting, some antennas at certain source nodes are redundant and cannot contribute to enlarge the DoF region. It is also found that there is no loss of optimality in terms of the sum DoF by enforcing symmetric data exchange within each user pair.

关键词： Multiple-input multiple-output two-way relay channel interference alignment physical-layer network coding signal alignment degrees of freedom

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A Multiple-Relay Communication Protocol for Achieving Fairness in Dense networks

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IEEE ACCESS 2018年 6卷 6740-6754页

作者： Torrea-Duran, Rodolfo Rosas, Fernando Pollin, Sofie Vandendorpe, Luc Moonen, Marc Katholieke Univ Leuven Dept Elect Engn ESAT B-3000 Leuven Belgium Katholieke Univ Leuven STADIUS Ctr Dynam Syst Signal Proc & Data Analyt B-3000 Leuven Belgium Katholieke Univ Leuven MICAS Microelect & Sensors B-3000 Leuven Belgium Katholieke Univ Leuven TELEMIC Telecommun & Microwaves B-3000 Leuven Belgium Catholic Univ Louvain ICTEAM Inst Digital Commun Grp B-1348 Louvain La Neuve Belgium

Increasing the density of base stations deployment is regarded as a means to satisfy the growing demand of wireless connectivity over a shared bandwidth, however, increasing the disparity in the service received by each user. Fairness can be realized by dynamically allocating resources to users using detailed channel state information at the transmitter (CSIT), which constitutes an expensive overhead, especially, for dense networks. One solution to improve the fairness without CSIT is to introduce spatial diversity through the use of relays in combination with physical-layer network coding (PNC). Most relaying-PNC solutions focus on the particular case of the two-way relay channel or they require additional relays and a large transmission time. In this paper, we propose a multiple-relay communication protocol (MRCP) for achieving fairness in dense networks. It exploits spatial diversity without requiring additional relays since it uses the base stations as relays. Furthermore, MRCP is applicable to an arbitrary number of base stations and users, while keeping a small transmission time. We show that our approach achieves the highest max-min fairness among users and almost full diversity with asymmetric transmissions.

关键词： Fairness physical-layer network coding relaying dense networks

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Backbone-Assisted Wireless Local Area network

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2021年第3期20卷 830-845页

作者： Pan, Haoyuan Liew, Soung Chang Chinese Univ Hong Kong Dept Informat Engn Hong Kong Peoples R China

This article presents a cross-layer design of backbone-assisted wireless local area network (WLAN) for dense WLAN deployment. The popularity of 802.11-based WLANs leads to dense WLAN deployment in geographically limited space, including dense access points (AP) and dense users. With dense APs, an AP could overhear packets destined for other APs. Backbone-assisted WLAN is a new system architecture where cooperative APs share the overheard packets through a backbone network, thereby reducing packet retransmission and improving system throughput. Conventional WLAN, such as Wi-Fi, uses Stop-and-Wait ARQ. This article argues that Stop-and-Wait does not work well with backbone-assisted WLAN because of large backbone delays. We first show that with a variant of Selective Repeat ARQ tailored for backbone-assisted WLAN, a single-user backbone-assisted WLAN system can achieve substantial throughput improvement over that with Stop-and-Wait ARQ. Then, we put forth a new system architecture targeted for dense users, referred to as network-coded backbone-assisted WLAN, in which multiple users are allowed to transmit simultaneously. A distinguishing feature of this system is the joint use of physical-layer network-coding (PNC) decoding and multiuser decoding (MUD) in multipacket reception. This article is the first attempt to design an ARQ for multiuser backbone-assisted WLAN. Our overall system design solves a PNC sequence obfuscation problem and addresses long packet latency in Selective Repeat ARQ. Experiments on our software-defined radio prototype indicate that network-coded Ethernet-backbone-assisted WLAN can achieve high system throughput and low packet latency. Specifically, the system throughput can outperform an MUD-only multiuser WLAN and a single-user WLAN by 60 and 100 percent, respectively. Overall, we believe that network-coded backbone-assisted WLAN is a viable solution for boosting throughput and reducing latency in dense WLAN environments.

关键词： Wireless LAN Throughput Multiuser detection Decoding Ethernet Delays Protocols Wireless local area network backbone physical-layer network coding multiuser detection ARQ implementation

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Compute-Compress-and-Forward: Exploiting Asymmetry of Wireless Relay networks

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2016年第2期64卷 511-524页

作者： Tan, Yihua Yuan, Xiaojun Chinese Univ Hong Kong Inst Network Coding Dept Informat Engn Hong Kong Hong Kong Peoples R China ShanghaiTech Univ Sch Informat Sci & Technol Shanghai Peoples R China

Compute-and-forward (CF) harnesses interference in a wireless network by allowing relays to compute combinations of source messages. The computed message combinations at relays are correlated, and so directly forwarding these combinations to a destination generally incurs information redundancy and spectrum inefficiency. To address this issue, we propose a novel relay strategy, termed compute-compress-and-forward (CCF). In CCF, source messages are encoded using nested lattice codes constructed on a chain of nested coding and shaping lattices. A key difference of CCF from CF is an extra compressing stage inserted in between the computing and forwarding stages of a relay, so as to reduce the forwarding information rate of the relay. The compressing stage at each relay consists of two operations: first to quantize the computed message combination on an appropriately chosen lattice (referred to as a quantization lattice), and then to take modulo on another lattice (referred to as a modulo lattice). We study the design of the quantization and modulo lattices and propose successive recovering algorithms to ensure the recoverability of source messages at destination. Based on that, we formulate a sum-rate maximization problem that is in general an NP-hard mixed integer program. A low-complexity algorithm is proposed to give a suboptimal solution. Numerical results are presented to demonstrate the superiority of CCF over the existing CF schemes.

关键词： Compute-and-forward compute-compress-and-forward modulo nested lattice codes physical-layer network coding quantization wireless relaying

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