Title :
Space-time coding ambiguities in joint adaptive channel estimation and detection
Author :
Gazor, Saeed ; Rad, Hamidreza Saligheh
Author_Institution :
Dept. of Electr. & Comput. Eng., Queen´´s Univ., Canada
Abstract :
This paper studies the error propagation effect that is caused by certain ambiguities in joint data detection-channel tracking algorithms for transmission diversity schemes. Here, we use a space-time (ST) receiver based on the maximum a posteriori (MAP) method that takes into account the channel estimation error assuming the unknown channel to have a given complex multivariate Gaussian probability density function (pdf) (i.e., a Ricean channel). The decision criterion that is expressed in quadratic form represents either a linear detector or a noncoherent-nonlinear detector in extreme cases. Then, the channel pdf for the next iteration is updated by estimates of the second-order statistics of the channel coefficients, and a very simple decision-directed adaptive algorithm is derived for adaptive channel estimation. The adaptive algorithm can efficiently track a fast Rayleigh fading channel and, as a result, achieves robust performance. However, the occurrence of two types of ambiguities initiated in deep fades result in error propagation. Some remedies called space-time ambiguity remedies (STARs) are proposed to prevent error propagation. A new time-varying space-time coding (TVST) scheme is suggested as a bandwidth-efficient method to combat the permutation ambiguity impairment. This coding scheme, in conjunction with a differential detector, can resolve the ambiguity problem.
Keywords :
Gaussian processes; Rayleigh channels; Rician channels; adaptive signal detection; bandwidth allocation; channel estimation; diversity reception; iterative methods; maximum likelihood estimation; radio receivers; space-time codes; Gaussian probability density function; MAP; adaptive channel detection; adaptive channel estimation; bandwidth-efficient method; decision-directed adaptive algorithm; error propagation; fast Rayleigh fading channel; linear detector; maximum a posteriori; noncoherent-nonlinear detector; permutation ambiguity; second-order statistics; space-time coding ambiguities; time-varying space-time coding scheme; transmit diversity; Adaptive algorithm; Bandwidth; Channel estimation; Channel state information; Degradation; Detectors; Fading; Maximum likelihood detection; Robustness; Time-varying channels;
Journal_Title :
Signal Processing, IEEE Transactions on
DOI :
10.1109/TSP.2003.820987