A novel spatial modulation scheme over correlated fading channels

Abstract — A novel spatial modulation (SM) scheme suitable for correlated Rician fading scenario is proposed with the help of the key idea of Ungerboeck’s set partitioning. The motivation is based on the fact that the different error performance exists between the antenna domain and modu-lation signal domain in the traditional SM scheme. And the total system error performance is mainly determined by the worse case. We analyze the unequal error protection (UEP) performance and find that the error performance of the antenna selection is mainly determined by the correlation coefficient and Rician factor. If the correlation coefficient or Rician factor is large, the error performance will be bad. Considering the error performance of the modulation signal domain is mainly determined by the minimum Euclidean distance between pair of signal points, the error performance of two domains will differ significantly over the fading channels with strong correlation or large Rician factor. The main idea of the novel scheme is to establish the relationship between the antenna domain and modulation signal domain by expanding the signal constellation to carry all the input information bits. The expanded constellation is then partitioned into subsets by using Ungerboeck’s set partitioning. The bits mapping to the antenna index are also used to select the partitioned subset, while the remaining bits are used to determine the transmit signal in the selected partitioned subset. In this way, the error performance of the bits mapping to the antenna index is improved, while the error performance of the other bits is preserved by maximizing the minimum Euclidean distance between any pair of signal points in the partitioned subset. Performance analysis and simulation results show that the novel SM scheme could improve the error system performance greatly when the correlation coefficient or Rician factor become larger. Index Terms — MIMO, spatial modulation, set partitioning, spatial correlation, unequal error protection (UEP) I