Throughput-Optimal Half-Duplex Cooperative Scheme with Partial Decode-Forward Relaying

We study a cooperative communication system consisting of two users in half duplex mode communicating with one destination over additive white Gaussian noise (AWGN). Cooperation is performed between the two users by partial decode-forward relaying over 3 time slots with variable duration. During the first two slots, each user alternatively transmits and partially decodes while during the last time slot, both users cooperate to forward information to the destination. We establish the achievable rate region of this scheme. Then using the Lagrangian method, we analyze the optimal power allocations and the optimal time duration that maximize its individual and sum rates for the symmetric channel. Results show a significant improvement of the rates compared to the classical multiple access channel (MAC) when the inter-user channel quality is better than that between each user and the destination.