PERFORMANCE ANALYSIS OF MULTICARRIER CDMA SYSTEM BASED ON COMPLEX WAVELET PACKET AND SPACE-TIME BLOCK CODES IN RAYLEIGH FADING CHANNEL

摘要

On the basis of analyzing the principle of multicarrier CDMA (MC-CDMA) technique and space-time coding technique, using the optimized complex wavelet packet as multicarrier modulation, a novel MC-CDMA system based on complex wavelet packet and space-time block codes is proposed. The bit error rate (BER) performance of the system is investigated in Rayleigh fading channel, and the corresponding BER expression is derived in detail. The system can overcome the decrease of spectrum efficiency of conventional MC-CDMA due to inserting cyclic prefix (CP). Moreover, the application of space-time coding technique strengthens the capability against fading channel significantly and perfects the system performance. Theoretical analysis shows that the proposed system with 2-transmitter antenna and 2-receiver antenna space-time block codes performs four times better than the single-antenna MC-CDMA system based on complex wavelet packet (CWP-MC-CDMA); the same conclusion is also reached by the simulation results in fading channel. As a result, the performance of the proposed CWP-MC-CDMA system outperforms a conventional MC-CDMA system based on DFT, it is close or superior to that of the conventional MC-CDMA with CP. Especially, the CWP-MC-CDMA system with space-time coding has superior ability to combat spatial fading and multi-access interference, and it slightly outperforms conventional MC-CDMA with CP and space-time coding.