Optimum design of closed-loop macro diversity scheme for cooperative base stations

The optimum design of the cooperative precoding matrix is investigated for the system consisted of cooperative multi-antenna base stations and one multi-antenna mobile terminal. A mathematical model is first established for the cooperative precoding matrix optimization which is based on the minimization of the mean squared error. In order to deal with the difficulty as a result of the block diagonal structure of the cooperative precoding matrix, the original problem is then converted into an equivalent problem which involves a long column vector consisted of all non-zero elements in the block diagonal cooperative matrix. With the equivalent problem, the Lagrangian multiplier method is finally employed to obtain the optimum solution in an analytical form to the original problem. Moreover, based on this analytical expression of Cooperative Multi-Points (CoMP) precoder, an iterative algorithm is developed to jointly optimize the precoder of CoMP and the receiver of MT. Numerical simulations show the effectiveness of the proposed cooperative precoding schemes in terms of bit error rate, symbol error rate and the spectral efficiency of the whole system.