The Parallel Space-Time Coding for CMMB-MIMO Systems

It is well known that MIMO-OFDM technology can improve the diversity gain and system capacity, increase spectrum efficiency and overcome frequency selective fading. However, few MIMO testbeds or prototypes have been considered for CMMB standards. In this work, we present a novel 2x2 MIMO structure for CMMB system. A parallel Alamouti coding is designed to decrease the complexity of MIMO implementation without any BER performance loss. The design of differential pilot for dual antenna transmission structure aims at distinguishing the two antennas and accomplishing MIMO channel estimation. Rayleigh propagation channel model and configuration is considered for each diversity scheme. Moreover, the interpolation filtering scheme was utilized to improve the LS channel estimation accuracy. The benefits of these techniques are studied by comparing 2x2 MIMO, 2x1 MISO, 1x2 SIMO and SISO systems. As is shown in simulation results, the diversity gain improved by MIMO over SISO system is 66.2% under QPSK modulation and 53.3% under 16QAM modulation.