Sum-Rate Optimization for Alamouti Distributed Space-Time Coding in Bi-Directional Cooperative Communications

In this correspondence, we develop the optimization strategy to optimize the sum-rate of the bi-directional cooperative communication networks applying Alamouti distributed space-time coding scheme. Instead of optimizing the sum-rate directly, we transform the sum-rate optimization problem into power optimization one under the quality of service constraints. This approach transforms the non-convex optimization problem for the sum-rate into the linear programming problem of the relay power which is more convenient to solve. Furthermore, we investigate the sum-rate of the fixed amplify-and-forward and optimized bi-directional cooperative communication networks in comparison to the fixed amplify-and-forward one-way cooperative communication one. The optimized scheme outperforms to the two others. Finally, we validate the symbol error rate of these schemes based on the results of the Monte Carlo simulations. The simulations shows that the symbol error rate of the optimized scheme is lower than the fixed amplify-and-forward and fixed amplify-and-forward one-way cooperative communication networks in low, moderate, and quite high SNR regimes.