Title :
Linear MMSE space-time equalizer for MIMO multicode CDMA systems
Author :
Kim, Byoung-Hoon ; Zhang, Xiaoxia ; Flury, Manuel
Author_Institution :
Qualcomm, Inc., San Diego, CA
Abstract :
We propose an enhanced chip-level linear space-time (ST) equalizer for multiple-input multiple-output (MIMO) multicode code-division multiple-access (CDMA) systems. In the MIMO multicode CDMA systems, the reuse of the same spreading codes in different transmit antennas significantly degrades the equalization performance if the ST equalizer uses a minimum mean-squared error (MMSE) weighting vector that minimizes the mean-squared error of the equalizer output chip sequence. As the CDMA despreader concatenated to an ST equalizer distorts interstream interference components differently from multipath interference and background noise components, the chip-level MMSE weighting vector usually steers in suboptimal directions in the signal space. Therefore, we propose a new MMSE weighting vector that takes the despreading effect into account in this paper. Simulation results show a substantial performance improvement through the new weighting vector
Keywords :
MIMO systems; antenna arrays; code division multiple access; equalisers; interference (signal); least mean squares methods; transmitting antennas; MIMO multicode CDMA systems; background noise components; enhanced chip-level linear space-time equalizer; equalization performance; equalizer output chip sequence; interstream interference components; linear MMSE space-time equalizer; minimum mean-squared error weighting vector; multicode code-division multiple-access systems; multipath interference; multiple-input multiple-output systems; spreading codes; transmit antennas; Background noise; Concatenated codes; Degradation; Distortion; Equalizers; Interference; MIMO; Multiaccess communication; Transmitting antennas; Vectors; Code-division multiple access (CDMA); minimum mean-squared error (MMSE); multiple-input multiple-output (MIMO); space–time (ST) equalizer;
Journal_Title :
Communications, IEEE Transactions on
DOI :
10.1109/TCOMM.2006.881339