Independent adaptive control of surviving symbol replica candidates at each stage based on minimum branch metric in QRM-MLD for OFCDM MIMO multiplexing [mobile radio]

This paper proposes independent adaptive control of the number of surviving symbol replica candidates, S_m, to calculate branch metrics, i.e., squared Euclidian distances, at each stage based on the minimums accumulated branch metric of each state in maximum likelihood detection, applying QR decomposition and the M-algorithm (QRM-MLD hereafter) for orthogonal frequency and code division multiplexing (OFCDM) MIMO multiplexing. In the proposed algorithm, the number of surviving symbol replica candidates at the m-th stage is independently controlled using the threshold value calculated from the minimum accumulated branch metric at the stage and estimated noise power. Computer simulation results show that the average number of squared Euclidian distance computations for the proposed adaptive independent S_m control method is decreased to approximately 1/3 that of the adaptive common S_m control and to approximately 1/6 that of the fixed S_m method for all stages, assuming for all control methods an identical achievable average block error rate.