The Study Of Adaptive Technology Based On Blockwise Multiple Access

Recently, block-wise transmission techniques have become a hot research field of broadband digital communication. The block-wise transmission techniques with frequency domain equalization include OFDM and SC-FDE. Both are featuring high frequency efficiency, robustness to frequency selective fading and simple equalization. The multiplexing techniques based on them have gained great interest, for example MC-CDMA, CP-CDMA, OFDMA, DFT-SOFDM and so on.Firstly, this thesis introduces the present multiplexing techniques, Optimal Signal Subspace theory and OSS-based adaptive SC-FDE system. The Optimal Signal Subspace theory is also the foundation of the adaptive algorithm proposed in this thesis.Secondly, this thesis proposes adaptive multiusers communication system,i.e.,adaptive CP-OSS-CDMA system and adaptive DFT-SOFDM system. These are established on Optimal Signal Subspace theory and the low-cost adaptive scheme that needs only 1 bit feedback information per subchannel. In order to employ the adaptive scheme in CP-CDMA, this thesis introduces CPA-DS-CDMA system and provides the adaptive CP-OSS-CDMA system. Because of low-cost complexity and only 1 bit feedback information per subchannel, the adaptive systems are very suitable for mobile broadband wireless communication.Because the adaptive DFT-SOFDM system, which bases on 1 bit feedback information per subchannel, assigns the subcarriers among the given subcarriers group, the adaptive DFT-SOFDM system can not exploit the Multiuser Diversity. So the frequency efficiency reduces. In order to exploit the multiuser diversity, the paper proposes a new algorithm that assignes the subcarriers among users. This effectively improves the system performance and frequency efficiency. However, the complexity of this system is higher and the feedback information is more. So the system is fit for the slowly fading channel.