The bit error probability for quadrature amplitude modulation (QAM) with L -fold space diversity in Rayleigh fading channels using earlier Log-likelihood ratio (LLR) approach is presented in this article. Two combining techniques, Maximal Ratio Combiner (MRC) and Selection Combining (SC) are considered for the analysis. LLR is used for the individual bits forming a QAM symbol to derive expression for the probability of error for various bits in the QAM symbol on flat fading channels with MRC and SC space diversity. The average bit error rate (BER) is determined from this expression. The analytical results show that the probability of bit error decreases with the order of diversity for both cases of MRC and SC. The derived formula can be used to achieve the desired BER at specific order of diversity in wireless mobile communication systems employing QAM modulation.
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