TABLE OF CONTENTS It is well known that the CDMA scheme is robust to frequency selective fading and has been successfully introduced in commercial cellular mobile communications systems such as IS-95 and 3G systems [1 3]. On the other hand, as shown in Chapter 4, the OFDM scheme is also inherently robust to frequency selective fading. Therefore, no one would expect any synergistic effect in combination of the OFDM and CDMA schemes.
In 1993, the MC-CDM/CDMA system, which is indeed a combination of the two schemes, was independently proposed by three different groups [4 6]. So far, the MC-CDM/CDMA system has drawn a lot of attention, and we have conducted intensive research on this interesting system [7 18]. Now, in 2002, the MC-CDM/CDMA system is considered to be one of candidates as a physical layer protocol for 4G mobile communications, because 4G systems require high scalability and adaptability in the possible transmission rate and the MC-CDMA has the potential.
This chapter discusses the MC-CDMA system in detail. Section 9.2 modifies the channel model introduced in Chapter 2 to discuss the BER performance of a multiplexing system in downlink and a multiple access system in uplink. Section 9.3 presents the principle of a direct sequence (DS)-CDMA system and analyzes the BER lower bound. Section 9.4 discusses the MC-CDMA system. The section presents the principle of the MC-CDMA system with four singleuser combining schemes in downlink and two multiuser detection schemes in uplink, shows a head/tail guard interval insertion method not only to eliminate ISI and...
