Spatial Pre-Coding with Phase Flipping for Wireless Communications

Abstract

The performance of spatial pre-coding schemes depends on the amount of channel state information available at the transmitter. A novel approach is spatial pre-coding with phase flipping investigated in this paper. The scheme is referred to as spatial phase coding (SPQ). Two flipping criteria, the angle criterion (AC) and the absolute value criterion (AVC), are proposed which change the phase relation of the signals between multiple transmit antennas such that the probability of constructive superposition of the signals at the receiver antenna is increased. Compared to known pre-coding schemes, SPC AVC does not need knowledge about the channel from each transmit antenna for pre-coding. Instead, it requires only information about the absolute value of the superimposed channel. This paper shows that SPC can achieve an array gain additional to the diversity gain. This is not possible with schemes like transmitter antenna selection diversity (SD). The lower bounds for SPC are defined by equal gain transmission (EGT) and maximum ration transmission (MRT).