Abstract: The error probability performance for MIMO WCDMA systems with the space-time block codes and convolutional codes employed at the transmitter, maximal-ratio-combining antenna diversity and soft decoding schemes employed at the receiver is investigated under the condition of multiple access interference. Based on the alternative representations of Q(x) and the moment generating function of SINR, the pairwise error probability of a convolutional coded system and union upper bound of error performance are derived under the condition of multiple access interference and nonidentical average transmitted power at each transmit antenna in Nakagami-m fading channels.The performance of a space-path diversity receiver in various coding schemes is illustrated. Numerical results show that the combination of convolutional coding and spatial combining leads to a dramatic performance improvement for MIMO WCDMA systems. The analysis result can be applied to uplink and downlink of MIMO WCDMA systems.