PERFORMANCE ANALYSIS OF ORTHOGONAL FREQUENCY AND CODE DIVISION MULTIPLEXING (OFCDM)

Abstract

With the advancements in the multimedia and mobile devices, requirement of high data rate transmission is also increasing. High data rate demand is increasing especially for video conferencing, online gaming and real time broadcasting. The research in the field of wireless communication is focusing new modulation techniques which would provide reliable and high data rate communication. OFDM has provided the high data rate with simple modulation and detection techniques. While the research is progressing to make the communication more reliable, hence increase in the data rate. Combining the two dimensional spreading with OFDM developed the new modulation scheme named OFCDM, which provides the reliable transmission. OFCDM has two dimensional spreading, in time domain and in frequency domain. Spreading in the frequency domain provides the frequency diversity while spreading in time domain provides the flexible transmission rates. NTT DoCoMo has proposed OFCDM for future fourth (4th) generation wireless communication system by testing its prototype model in Japan. So it is getting popular and attractive modulation due to its advantages over OFDM. In this thesis we will focus on the performance analysis of OFCDM in different fading environments. In this research we will only consider the downlink transmission of OFCDM. So performance analysis of OFCDM is carried out in six SUI channels which are designed for fixed wireless applications. Initially some digital modulation techniques such as OFDM, CDMA, MC-CDMA and multipath fading environments such as Rayleigh, Rician and SUI channels are discussed. Then we will discuss the detection and equalization techniques at the receiver. Performance comparison of OFCDM with OFDM is presented as simulation results. Simulation in term of BER graph is shown to verify the performance in Rayleigh, Rician, and six SUI channels. For detection and equalization at the receiver zero forcing equalization technique is used. Due to presence of Doppler shift in the channel OFCDM also experiences the multi-code interference (MCI). While in this thesis all the simulations are carried out without MCI cancellation technique. Finally we will present the overall results and describes the attractiveness of this modulation technique by comparing the results with OFDM.