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We investigate a two-way relay (TWR) fading channel where two source nodes wish to exchange information with the help of a relay node. Given traditional TWR protocols, transmission rates in both directions are known to be limited by the hop with lower capacity, i.e., the min operations between uplink and downlink. In this paper, we propose a new transmission protocol, called alternative awaiting and broadcast (AAB), to cancel the min operations in the TWR fading channels. The operational principles, a new upper bound on ergodic sum capacity (ESC), and a convergence behavior of the average delay of signal transmission (ST) (in the relay buffer) for the proposed AAB protocol are analyzed. Moreover, we propose a suboptimal encoding/decoding solution for the AAB protocol and derive an achievable ergodic sum rate (ESR) with a corresponding average delay of ST. Numerical results show that 1) the proposed AAB protocol significantly improves the achievable ESR compared with the traditional TWR protocols, and 2) considering the average delay of system service (SS) (in the source buffer), the average delay of ST induced by the proposed AAB protocol is very small and negligible. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]