Unified performance analysis of several multicarrier spread-spectrum multiple-access systems in correlated Rayleigh fading channels

Abstract

Abslracl-In this paper, we propose a mvel mnlticarrier spreadspectrum multiple-access system, called MC-FH-CDMA, m which the ideas behind two other multiple-access systems, namely MC-CDMA and MGFH, are used to support multimedia multi-rate services, though improving or preserving the system performance without increasing complexity. We develop a unified approach for the performance analysis of these three systems in a correlated Rayleigh fading uplink channel with BPSK modulation and MRC combining, and compare the results with each other.Kewwords: spread-specuum, multiple-access, multimedia, MC-CDMA, MC-FH, BPSK, MRC. I. LNTRODUCTIONIn the new proposed multicanier spread specuum multiple access system, called MC-FH-CDMG two signature sequences are assigned to each user. The first signature acts as in a MC-FH system [ l ] and distinguishes between different users; i.e., it determines the set of carriers, each belonging to one frequency slot, to be used by the user in each bit interval. The second signature, the length of which is equal to the number of carriers in each bit interval, modulates the carriers. selected by the first signature, as in a MC-CDMA system [2] [3], and in fact, differentiates between different multimedia (multi-rate) services of the same user, or alternatively, between users with the same first signature sequences.The advantage of this new system lies in its support of multimedia multi-rate services, and less PAPR (with respect to MC-CDMA), because of its sparser subcarriers in the frequency domain, just like MC-FH. Also, the stable orthogonality of the FH codes can compensate for the distorted orthogonality of the DS codes caused by the channel gain fluctuations in a fading environment. In this scheme, like the other two systems, the transmitter and receiver can be simply implemented through FTT techniques, without increasing complexity due to introducing the second signature code. This paper is organized as follows. In Section 2, we describe a MC-FH-CDMA system, including general configurations and the channel model needed for analyzing the three systems. We provide the performance analysis of the three systems in Section 3. Numerical results are presented in Section 4, and finally, we conclude this paper in Section 5.