LAUSR

Precoding-aided spatial modulation (PSM) is a multi-antenna communication scheme, which jointly modulates information bits into both the spatial index and the signaling constellation. Specifically, the spatial bits are conveyed by the index of a receive antenna, which is steered at by precoding at the transmitter. In this paper, the indices of the receive antennas are called a spatial constellation in contrast to the signaling constellation. We investigate the symbol error rate (SER) of the PSM scheme to strike a fine tradeoff between the signaling and the spatial constellation, i.e., the signaling-spatial constellation tradeoff, which minimizes the system's SER. First, we formulate the SER of the PSM scheme. Then, an explicit upper bound on the SER is determined based on an approximation using a weighted sum of exponentials. By minimizing the SER upper bound, we show that for phase-shift keying modulation, it achieves a sufficiently good tradeoff when the size of the signaling constellation is 4, i.e., the quadrature phase-shift keying. The numerical results show that the signaling-spatial constellation tradeoff determined by the derived SER upper bound significantly outperforms other PSM schemes with equal spectral efficiency.