Space-time codes for high data rate wireless communication: Performance criteria in the presence of channel estimation errors, mobility, and multiplepaths

Space-time coding is a bandwidth acid power efficient method of communicati on over fading channels that realizes the benefits of multiple transmit ant ennas, Specific codes have been constructed using design criteria derived f or quasi-static flat Rayleigh or Rician fading, where channel state informa tion is available at the receiver. It is evident that the practicality of s pace-time codes will be greatly enhanced if the derived design criteria rem ain valid in the absence of perfect channel state information, It is even m ore desirable that the design criteria not be unduly sensitive to frequency selectivity and to the Doppler spread, This paper presents a theoretical s tudy of these issues beginning with the effect of channel estimation error, Here it is assumed that a channel estimator extracts fade coefficients at the receiver and for constellations with constant energy, it is proved that in the absence of ideal channel state information the design criteria for space-time codes is still valid. The analysis also demonstrates that standa rd channel estimation techniques can be used in conjunction with space-time codes provided that the number of transmit antennas is small. We also deri ve the maximum-likelihood detection metric in the presence of channel estim ation errors. Next, the effect of multiple paths on the performance of spac e-time codes is studied for a slowly changing Rayleigh channel. It is prove d that the presence of multiple paths does not decrease the diversity order guaranteed by the design criteria used to construct the space-time codes, Similar results hold for rapid fading channels with or without multiple pat hs, The conclusion is that the diversity order promised by space-time codin g is achieved under a variety of mobility conditions and environmental effe cts.