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Rate Adaptation for wireless network coding using Partial Overhearing

IEEE COMMUNICATIONS LETTERS 2009年第12期13卷 890-892页

作者： Hwang, Chan-Soo Moon, Hichan Samsung Electronics Co. Ltd. South Korea

This letter investigates rate adaptation of network coding (NC) in a wireless network. In the network, two independent data flows intersect at a relay and a receiver can overhear the data flow of which it is not the intended destination. We propose NC schemes which actively exploit the overhearing channels by adapting the transmission rate to the direct- and overhearing-channel conditions. The proposed schemes allow a receiver to overhear only part of the data-flow by rate splitting, thus significantly improving the throughput in poor overhearing-channel conditions.

关键词： Adaptive modulation wireless network coding

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Opportunistic Scheduling for wireless network coding

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IEEE TRANSACTIONS ON wireless COMMUNICATIONS 2009年第6期8卷 2766-2770页

作者： Yomo, Hiroyuki Popovski, Petar Aalborg Univ Dept Elect Syst Antenna Propagat & Networking Grp Aalborg Denmark

This letter addresses a scheduling problem for wireless network coding (WNC). In our previous work, we have theoretically shown that the optimum number of nodes to be included into a network-coded packet as well as its transmission rate depends on time-varying link condition between a transmitting node and receiving nodes [1]. Based on this observation, this letter designs practical scheme which opportunistically selects scheduled nodes, packets to be coded and an employed modulation level according to time-varying channel conditions and packet length. The numerical results show that the proposed opportunistic scheduling can improve the overall throughput as compared with non-opportunistic approach.

关键词： wireless network coding fading rate adaptation adaptive modulation opportunistic scheduling

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Cooperative Peer-to-Peer Information Exchange via wireless network coding

Cooperative Peer-to-Peer Information Exchange via Wireless N...

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IEEE Global Telecommunications Conference (GLOBECOM 09)

作者： Fan, Yanfei Jiang, Yixin Zhu, Haojin Shen, Xuemin (Sherman) Univ Waterloo Dept Elect & Comp Engn Waterloo ON N2L 3G1 Canada

ISBN: (纸本)9781424441471

network coding has been widely recognized as a promising information dissemination approach for wireless networks. However, in practical wireless networks enabled with network coding, different peer sending sequences make significant impact on overall network throughput and transmission delay. In this paper, we study the peer scheduling problem, which is defined as how to intelligently schedule the sending sequence among a group of peers to maximize the wireless coding gain. By conducting an in-depth investigation on the peer scheduling principles in wireless network coding, we propose a cooperative Peer-to-peer Information Exchange (PIE) scheme with an efficient and light-weight peer scheduling algorithm. The PIE scheme can not only fully exploit the broadcast nature of wireless channels, but also utilize the advantage of cooperative peer-to-peer information exchange. Finally, the effectiveness and efficiency of the PM scheme are demonstrated through qualitative analysis and extensive simulations.

关键词： Cooperative peer-to-peer wireless network coding scheduling

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Threshold-Based One-Bit Soft Forwarding for a network Coded Multi-Source Single-Relay System

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IEEE TRANSACTIONS ON COMMUNICATIONS 2014年第5期62卷 1604-1620页

作者： Li, Jun Lin, Zihuai Vucetic, Branka Xu, Jin Xiao, Ming Chen, Wen Univ Sydney Sch Elect & Informat Engn Sydney NSW 2006 Australia ZTE Prod R&D Syst Wireless Technol Preres Dept Shenzhen Peoples R China Royal Inst Technol Sch Elect Engn Stockholm Sweden Shanghai Jiao Tong Univ Dept Elect Engn Shanghai 200030 Peoples R China

In this paper, we propose a threshold-based one-bit soft forwarding (TOB-SF) protocol for a multi-source relaying system with network coding, where two sources communicate with the destination with the help of a relay. Specifically in the TOB-SF protocol, the relay calculates the log-likelihood ratio (LLR) value of each network coded symbol, compares this LLR value with a pre-optimized threshold, and determines whether to transmit or keep silent. We are interested in optimizing the TOB-SF protocol in fading channels, and consider both the uncoded and low-density parity check coded systems. In the uncoded system, we first derive the bit error rate (BER) expressions at the destination, based on which, we derive the optimal threshold. Then we theoretically prove that the system can achieve the full diversity gain by using this threshold. Further, we optimize the power allocation at the relay to achieve a higher coding gain. In the coded system, we first optimize the LLR threshold. Then we develop a methodology to track the BER evolution at the destination by using Gaussian approximations. Based on the BER evolution, we further optimize the power allocation at the relay which minimizes the system BER. Simulation results show that the proposed TOB-SF protocol outperforms other conventional relaying protocols in terms of error performance.

关键词： One-bit soft forwarding log-likelihood ratio wireless network coding power allocation

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The Effect of wireless Channel on network coding Opportunities

The Effect of Wireless Channel on Network Coding Opportuniti...

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20th IEEE Symposium on Personal, Indoor and Mobile Radio Communications

作者： Gkelias, Athanasios Leung, Kin K. Ling, Cong Imperial Coll London London England

ISBN: (纸本)9781424451234

The impact of wireless network coding on multiuser diversity gain is investigated. A generic framework to calculate the CDF of the opportunistic channel gain, for different communication scenarios with a single relay, when scheduling or network coding are used, is presented. The CDF and PDF of the log-normal and Rayleigh opportunistic channels for these scenarios are calculated and the average system capacity is derived. Numerical results show that while wireless network coding most of the time can provide significant throughput gain, for low mean received SNR and high channel variations it may result to lower ergodic capacity than simple opportunistic scheduling, especially when transmission overhearing is required. For these cases, we show that although a coding gain is achieved, there may be a larger reduction on the multiuser diversity gain which results to overall lower average system capacity compare to traditional opportunistic scheduling.

关键词： wireless network coding Rayleigh Fading Log-normal Shadowing Multiuser Diversity Gain

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Physical Layer network coding for Two-Way Relaying with QAM

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IEEE TRANSACTIONS ON wireless COMMUNICATIONS 2013年第10期12卷 5074-5086页

作者： Namboodiri, Vishnu Venugopal, Kiran Rajan, B. Sundar Qualcomm India Private Ltd Hyderabad 500081 Andhra Pradesh India IISc Bangalore Dept ECE Bangalore 560012 Karnataka India

The design of modulation schemes for the physical layer network-coded two-way relay network has been studied in literature and it is known that every network coding map that satisfies the exclusive law is representable by a Latin Square. This relationship has been used to get network coding maps satisfying the exclusive law. But, only the scenario in which the end nodes use M-PSK signal sets has been addressed previously. In this paper, we address the case in which the end nodes use M-QAM signal sets. In a fading scenario, for certain channel conditions gamma e(j theta), termed singular fade states, the end-to-end performance is greatly reduced. By formulating a procedure for finding the exact number of singular fade states for QAM, we show that square QAM signal sets give lesser number of singular fade states compared to PSK signal sets. This reduces the computational complexity at the relay node. It is shown that the criterion for partitioning the complex plane, for the purpose of using a particular network code for a particular fade state, is different from that used for M-PSK. Using a modified criterion, we describe a procedure to analytically partition the complex plane representing the channel condition. We show that when M-QAM (M > 4) signal set is used, the conventional XOR network mapping fails to remove the ill effects of gamma e(j theta) = 1, which is a singular fade state for all signal sets of arbitrary size. We show that a doubly block circulant Latin Square removes this singular fade state for M-QAM. Finally it is shown that M-QAM gives superior performance over M-PSK.

关键词： Latin square network coding relay channel two-way relaying wireless network coding

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Multi-Flow Scheduling for Coordinated Direct and Relayed Users in Cellular Systems

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IEEE TRANSACTIONS ON COMMUNICATIONS 2013年第2期61卷 669-678页

作者： Chan Dai Truyen Thai Popovski, Petar Kaneko, Megumi de Carvalho, Elisabeth Aalborg Univ Dept Elect Syst Aalborg Denmark Kyoto Univ Grad Sch Informat Kyoto Japan

There are two basic principles used in wireless network coding to design throughput-efficient schemes: (1) aggregation of communication flows and (2) interference is embraced and subsequently cancelled or mitigated. These principles inspire design of many novel multi-flow transmission (MFT) schemes. Such are the Coordinated Direct/Relay (CDR) schemes, where each basic transmission involves two flows to a direct and a relayed user. Usage of MFT schemes as building blocks of more complex transmission schemes essentially changes the problem of scheduling, since some of the flows to be scheduled are coupled in a signal domain and they need to he assigned a communication resource simultaneously. In this paper we define a novel framework that can he used to analyze MFT schemes and assess the system-level gains. The framework is based on cellular wireless users with two-way traffic and it sets the basis for devising composite time-multiplexed MFT schemes, tailored to particular optimization criteria. Those criteria can he formulated by adapting well-known schedulers in order to incorporate MFT schemes. The results show rate advantages brought by the CDR schemes in pertinent scenarios. Another key contribution is the proposed framework, which can he used to evaluate any future multi-flow transmission scheme.

关键词： wireless relay wireless network coding interference cancellation coordinated transmission

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network Coded Modulation for Random Channel Class in WNC with HDF Relaying Strategy

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IEEE COMMUNICATIONS LETTERS 2013年第5期17卷 818-821页

作者： Sykora, Jan Burr, Alister Czech Tech Univ CR-16635 Prague Czech Republic Univ York York YO10 5DD N Yorkshire England

A standard NCM (network Coded Modulation) for WNC (wireless network coding) with HDF (Hierarchical Decode & Forward) strategy requires that each node has full knowledge of the connectivity pattern to other nodes and this knowledge affects the design of NCM and HNC (Hierarchical network Code) maps at each transmitting (source) and receiving (relay) node respectively. The final destination has to have full knowledge of all HNC maps used and the composite overall HNC map needs to be invertible to recover the source data. This approach collapses if nodes do not have a full knowledge of the connectivity pattern and thus cannot adjust their HNC maps properly. We design the NCM and HNC maps for WNC with HDF strategy that works regardless of this knowledge. It is based on a concept of a channel class which is a discrete (random) parameter describing the channel behavior and which becomes a part of HNC maps and the NCM hierarchical constellation. We analyze the rate regions for this design and compare it to the standard NCM and HNC map solution suffering from random channel outages.

关键词： wireless network coding random channel class network coded modulation

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Bi-directional multi-antenna relay communications with wireless network coding

Bi-directional multi-antenna relay communications with wirel...

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67th IEEE Vehicular Technology Conference

作者： Yuen, Chau Chin, Woon Hau Guan, Yong Liang Chen, Wenhua Tee, Taoyi Inst Infocomm Res I2R Singapore Singapore Nanjing Univ Technol Singapore Singapore

ISBN: (纸本)9781424416448

In this paper, we consider a two-way or bidirectional communications system with a relay equipped with multiple antennas. We show that when the downlink channel state information is not known at the relay, the benefit of having additional antennas at the relay can only be obtained by using decode and forward (DF) but not amplify and forward (AF). The gain becomes significant when we employ transmit diversity together with wireless network coding. We also demonstrate how the performance of such system can be improved by performing antenna selection at the relay. Our results show that if downlink channel state information is known at the relay, network coding may not provide additional gain than simple antenna selection scheme.

关键词： wireless network coding two-way or bidirectional communications multi-antenna relay transmit diversity

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A Joint network and Channel coding Strategy for wireless Decode-and-Forward Relay networks

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IEEE TRANSACTIONS ON COMMUNICATIONS 2011年第1期59卷 181-193页

作者： Li, Qiang Ting, See Ho Ho, Chin Keong Nanyang Technol Univ Sch Elect & Elect Engn Singapore 639801 Singapore ASTAR Inst Infocomm Res Singapore 138632 Singapore

In this paper, we consider a wireless multicast network with multiple sources, relays, and destinations. We adopt a multi-hop decode-and-forward relay protocol such that two canonical subnetworks are relevant, namely broadcast channel with receiver side information (BC-RSI) and orthogonal multiple access channel with correlated sources and receiver side information (MAC-CS-RSI). A joint network and channel coding (JNCC) strategy is proposed by exploiting ARQ, RSI, and correlated sources. The proposed JNCC strategy does not require the knowledge of RSI nor any transmit channel state information, such that each transmitter simply performs retransmissions until the intended receivers have accumulated enough mutual information to successfully decode all desired messages. This successful decoding is then conveyed from the receivers to the respective transmitters via an acknowledgement message. To measure the performance of the proposed JNCC strategy with ARQ, we derive closed-form expressions of network throughput by applying the renewal-reward theorem. Analytical results show that the proposed JNCC strategy outperforms, in terms of network throughput, the conventional separate network and channel coding strategy with random linear network coding.

关键词： wireless network coding joint network and channel coding broadcast channel multiple access channel

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