Improved bit error probability analysis for maximal ratio combining in asynchronous CDMA channels

The paper provides a general framework for accurately analyzing the bit error probability of the maximal ratio combining (MRC) diversity receiver in CDMA systems. In previous research on MRC receivers for direct sequence code division multiple access (DS-CDMA), compromising assumptions have been made to simplify the analysis, including a Gaussian approximation for interference or constant equal cross correlations. These assumptions can produce inaccurate results, especially when the number of users is small or when the diversity order is high, as will increasingly be the case in high-rate CDMA systems. We derive a novel closed-form bit error probability expression without these assumptions and verify through simulations that this new framework is highly accurate.