Performance Analysis of Multiband Complex Wavelet Based MC-CDMA System with Space Diversity Combining in Rayleigh Fading Channel

Abstract

In this paper, the multiband complex wavelet used as multi-carrier basis function is optimized. On the basis of analyzing the principle of multi-carrier code division multiple access (MC-CDMA), a new multiband complex wavelet based MC-CDMA (MBCW-MC-CDMA) system model is proposed, and space diversity combining (SDC) technique is employed to improve the system performance further. The uplink performance of proposed MBCW-MC-CDMA system with SDC technique is investigated in Rayleigh fading channel, and corresponding bit error rate (BER) analysis is given in detail. Without any cyclic prefix (CP), the system can avoid the decrease of spectrum efficiency and data rate of conventional MC-CDMA with CP. By comparison, our scheme outperforms real wavelet packet based MC-CDMA and slightly outperforms conventional MC-CDMA with CP via utilizing superior properties of the optimized multiband complex wavelet. Theoretical analysis and simulation result show that the application of SDC technique can improve the proposed system ability to combat spatial fading and various interferences effectively. Moreover, the proposed system based on SDC technique has superior BER performance over conventional DFT and SDC based MC-CDMA system and real wavelet packet and SDC based MC-CDMA system.

PERFORMANCE OF MULTIBAND COMPLEX WAVELET BASED MULTICARRIER DS-CDMA SYSTEM WITH MULTI-ANTENNA RECEIVER OVER NAKAGAMI-m FADING CHANNEL

“…The real wavelet does not perform well when it processes complex signals or in the case of many sub-band wavelet transforms being adopted to transmit mobile communication signals [8]. To implement superior performance, on the constrained condition of shifting orthogonality, we have optimized the coefficients of wavelet prototype filters to minimize the stop-band energy of wavelet filters.…”

“…Thus the optimized multiband complex wavelet can match complex channel frequency spectrum and benefit multicarrier communications. More details on the optimized multiband complex orthogonal wavelet can be seen in [8].…”

“…In this subsection, we develop a multicarrier DS-CDMA scheme based on the optimized multiband complex wavelet [8] and the modulation principle of multicarrier DS-CDMA [9] for the uplink, and conventional DFT/IDFT is replaced by multiband complex wavelet transform (a) Transmitter structure (MBCWT)/IMBCWT (inverse MBCWT) accordingly. Based on this scheme, we will investigate the system performance with multiple asynchronous CDMA users in Nakagami fading channel.…”

“…However, the performance of real wavelet system will be degraded in processing complex signal, and it can't adapt to complex channel well because of the spectrum characteristic of real wavelet. To overcome such a shortcoming, we present a class of multiband complex orthogonal wavelet through optimization in [8]. The optimized multiband complex wavelet not only has good properties that real wavelet packet possesses, such as shifting orthogonality, adaptability, time-frequency localization, etc., but also matches complex channel frequency spectrum well and suits multicarrier communications.…”

“…The optimized multiband complex wavelet not only has good properties that real wavelet packet possesses, such as shifting orthogonality, adaptability, time-frequency localization, etc., but also matches complex channel frequency spectrum well and suits multicarrier communications. Based on this, a multicarrier CDMA scheme based on the optimized multiband complex wavelet is developed in [8]. But the above scheme only gives the performance analysis in Rayleigh fading (a special case of Nakagami-m fading) channel.…”