Time-Varying Coding for Space-Time Ambiguities
The paper first formulates the error propagation effect that is caused by certain ambiguities in joint data detection/channel tracking algorithms for space-time (ST) schemes. The occurrence of any combination of two types of ambiguities, phase ambiguity (PhA) and permutation ambiguity (PeA), initiated in deep fades, produces error propagation in joint channel estimation/data detection for the dual transmit diversity method. A new time-varying space-time coding (TVST) scheme is suggested as a bandwidth efficient method to combat the PeA impairment. This coding scheme, in conjunction with a differential detector, can resolve the ambiguity problem. Finally, some remedies used to prevent error propagation are listed. These remedies are called space-time ambiguity remedies (STARs).