Decode-and-forward two-path half-duplex relaying: Diversity-multiplexing tradeoff analysis

Two-path or successive relaying has recently emerged as a promising cooperative communication protocol to improve spectral efficiency in half-duplex relaying networks. In this paper, we consider decode-and-forward (DF) version of the two-path relaying protocol. We analyze the fundamental performance of this protocol in terms of the diversity-multiplexing tradeoff (DMT). We first derive the DMT for this protocol, where perfect decoding at the relays is assumed, and show that it approaches the 3 × 1 multiple-input single-output (MISO) DMT. We then remove the assumption of perfect decoding at the relays and derive the closed-form expression of the achievable DMT based on the relative distances between nodes. Specifically, we found that for sufficiently long transmission length, if the average source-relay SNR is at least 2.5 times (measured in dB) of other links, the 3 × 1 MISO DMT is achieved. Successive interference cancellation at the relays is also proposed to further improve the performance of the DMT.