Performance investigation of STBC-OFDM with code-division multiplexing in time-varying channels

Orthogonal frequency division multiplexing (OFDM) is sensitive to carrier frequency offset and channel estimation error, which destroy the subcarrier orthogonality and give rise to intercarrier interference (ICI). This paper addresses the performance degradation due to imperfect parameters in an orthogonal frequency and code division multiplexing (OFDM-CDM) system with multiple transmit antennas. For the performance evaluation, the average bit error rate (BER) impairment due to imperfect channel information and frequency offset is investigated taking into account the effect of time-varying channels. Derived results show that a space-time block coded (STBC) OFDM-CDM system experiences a severe BER degradation regardless of the number of users.