Spatial Diversity with LDPC Codes

Wireless links are impaired by random fluctuations in signal level across space, time and frequency known as fading. Spatial diversity is an attractive solution to improve system capacity as well as system performance by providing array gain or increased SNR. Satellites (GEO,MEO) and High Altitude platform stations(HAPS) also exploit spatial diversity in LOS/NLOS envirornment. Exact nature of the diversity system depends on satellite antenna configuration. One of such configuration is SIMO diversity system that realizes receive diversity. LDPC codes have outstanding performance in some cases than that of turbo codes, with iterative decoding algorithm which is easy to implement and parallelizable in hardware. LDPC codes when implemented along with SIMO system with Maximum Ratio Combining (MRC) under the combination of AWGN and multipath fading is optimum from the standpoint of maximising SNR at combiner output. In addition when operating in interference scenario optimum combining can be employed that maximizes the output SINR. In this paper it is shown that LDPC codes with optimum combining (LDPC-OC) system improves SINR by 1.98 dB and 2.62 dB with 3 and 4 receive antennas respectively in multipath fading channel in the presence of a single interferer.