Throughput-Reliability Tradeoff in Decode-and-Forward Cooperative Relay Channels: A Network Information Theory Approach

Cooperative transmission protocols are always designed to reach the largest diversity gain and the largest network capacity simultaneously. The concept of diversity-multiplexing tradeoff (DMT) in MIMO systems put forward by Zheng and Tse has been extended to this field. However, the concept of multiplexing gain in DMT constrains a better understanding of the asymptotic interplay between transmission rate, frame error probability (FEP) and signal-to-noise ratio (SNR), and also fails to predict FEP curves accurately. Two improved methods are then put forward. One is by Narasimhan who proposes finite-SNR diversity-multiplexing gain tradeoff which gives a tighter lower bound of the FEP curves by applying nonlinear programming in MIMO systems, and the other is by Azarian and Gamal who propose a new rule called the throughput-reliability tradeoff (TRT) which avoids the limitation of the conception of multiplexing and elucidates the linearly asymptotic trends exhibited by the FEP curves in block-fading MIMO channels. The finite-SNR diversity-multiplexing gain tradeoff has already been applied to cooperative relay channels. However, this method is time-consuming in computation since nonlinear programming is used, especially in large networks. In this paper, we will use TRT rule to give the relationship between transmission rate, FEP and SNR in decode-and-forward (DF) cooperative protocols. We also exhibit the FEP curves predicted by TRT. To do this, We first propose a symbol based slotted decode-and-forward (SSDF) protocol as the infrastructure. Network information theory is also used to bound the capacity of the protocol.