Physical-layer Network Coding for Cooperative Wireless Networks

As a newly-emerged paradigm in the networking techniques, physical-layer network coding (PNC) [1, 5] takes advantage of the superimposition of the electromagnetic waves, and embraces the interference which was typically deemed as harmful, by performing exclusive-or mapping. Therefore, the spectral efficiency is utilized, which in turn boosts the network throughput. In the classical 2-way relay channel (2-WRC), PNC only spends two channel uses for the bi-directional data exchange. However, one challenge for such a paradigm is that the singular fading states in the uplink of 2-WRC, might result in ambiguity for decoding the network coded symbol. One major focus of this thesis is to address the fading issue for PNC in the 2-WRC. Another fundamental challenge for PNC is to extend the PNC from the 2-WRC to a multi-user network such as the multi-way relay channel (M-WRC) or the hierarchical wireless network (HWN). To tackle these two fundamental challenges of PNC, several solutions are proposed in this thesis, which are summarized as follows: First, we introduce two efficient fading correction strategies, i.e., the rotationally-invariant coded modulation and the soft-bit correction. Second, a novel multilevel coded linear PNC scheme with extended mapping for the Rayleigh fading 2-WRC is proposed. Third, we design a new type of linear PNC for the Rayleigh fading 2-WRC, based on rings. We refer to such design as linear PNC over the hybrid finite ring. Fourth, we redesign PNC for the HWN, which facilitates the multi-user data exchange. To combat the co-channel interference introduced by multi-user data exchange, two efficient interference exploitation strategies based on network coding are proposed: 1) PNC with joint decoding; and 2) analogue network coding with interference-aware maximum likelihood detection. Finally, we propose a multilevel coded LPNC for the data exchange in the M-WRC

Pairwise Check Decoding for LDPC Coded Two-Way Relay Block Fading Channels

Partial decoding has the potential to achieve a larger capacity region than full decoding in two-way relay (TWR) channels. Existing partial decoding realizations are however designed for Gaussian channels and with a static physical layer network coding (PLNC). In this paper, we propose a new solution for joint network coding and channel decoding at the relay, called pairwise check decoding (PCD), for low-density parity-check (LDPC) coded TWR system over block fading channels. The main idea is to form a check relationship table (check-relation-tab) for the superimposed LDPC coded packet pair in the multiple access (MA) phase in conjunction with an adaptive PLNC mapping in the broadcast (BC) phase. Using PCD, we then present a partial decoding method, two-stage closest-neighbor clustering with PCD (TS-CNC-PCD), with the aim of minimizing the worst pairwise error probability. Moreover, we propose the minimum correlation optimization (MCO) for selecting the better check-relation-tabs. Simulation results confirm that the proposed TS-CNC-PCD offers a sizable gain over the conventional XOR with belief propagation (BP) in fading channels.Comment: to appear in IEEE Trans. on Communications, 201

Self-concatenated code design and its application in power-efficient cooperative communications

In this tutorial, we have focused on the design of binary self-concatenated coding schemes with the help of EXtrinsic Information Transfer (EXIT) charts and Union bound analysis. The design methodology of future iteratively decoded self-concatenated aided cooperative communication schemes is presented. In doing so, we will identify the most important milestones in the area of channel coding, concatenated coding schemes and cooperative communication systems till date and suggest future research directions

Network-Coded Multiple Access

This paper proposes and experimentally demonstrates a first wireless local area network (WLAN) system that jointly exploits physical-layer network coding (PNC) and multiuser decoding (MUD) to boost system throughput. We refer to this multiple access mode as Network-Coded Multiple Access (NCMA). Prior studies on PNC mostly focused on relay networks. NCMA is the first realized multiple access scheme that establishes the usefulness of PNC in a non-relay setting. NCMA allows multiple nodes to transmit simultaneously to the access point (AP) to boost throughput. In the non-relay setting, when two nodes A and B transmit to the AP simultaneously, the AP aims to obtain both packet A and packet B rather than their network-coded packet. An interesting question is whether network coding, specifically PNC which extracts packet (A XOR B), can still be useful in such a setting. We provide an affirmative answer to this question with a novel two-layer decoding approach amenable to real-time implementation. Our USRP prototype indicates that NCMA can boost throughput by 100% in the medium-high SNR regime (>=10dB). We believe further throughput enhancement is possible by allowing more than two users to transmit together