Complementary Code And Its Applications In High Rate WLAN And Future Mobile Communications System

The 3rd generation (3G) mobile communications system and part of the 2nd generation (2G) mobile communications use PN sequences or Walsh codes as spread codes, and their system capacities are limited by the multiple access interference (MAI) from asynchronous transmitted signals.Complementary codes (CC) and complete complementary codes (CCC) have excellent orthogonality and correlation properties. When CCC are used for spreading codes, multiple access interference (MAI) is zero theoretically even under asynchronous transmission. If CC/CCC are used for spreading codes, one data symbol could be transmitted during one-chip duration. Therefore, data rate and system capacity of communications system are much higher than those in 2G and 3G mobile communications systems.This thesis focuses on the performance of complete complementary keying modulation and multi-carrier CDMA architecture based on complete complementary codes (CCC-CDMA). The main contents are as follows:The history of mobile communications is introduced, and then the basic features of 3G and beyond 3G (B3G) communications systems are also introduced.On analyzing properties of mobile channel, the fading channel models are described. The simulation method of baseband channel model is also presented.The definitions and primary properties of complementary codes and complete complementary codes are given, which is the theoretical foundation of CC/CCC application in wireless communications system.IEEE 802.11b baseband model and CCK modulation are studied. The closed-form performance formulae of CCK modulation are derived under AWGN channel and Rayleigh fading channel, whose validity is proved by simulations.Multi-carrier wideband CDMA architecture based on complete complementary codes spread (CCC-CDMA) has high spectrum efficiency without MAI theoretically, which meets the general requirements of B3G communications. Channel estimation and multipath diversity in the receiver are investigated in this thesis. An improved channel estimation scheme are offered, which resists noise efficiently and provides accurate channel estimation coefficient. A new channel estimation scheme is derived through taking advantage of properties of CCC. This new scheme provides accurate estimation and its complexity is low. In view of the error diffusion in CCC-CDMA, the multipath diversity algorithm is put forwards. The simulations show that the multipath diversity gain attains as much as l0dB.