Spreading Code Design And Subcarrier Allocation Technologies Research For Multi-Carrier CDMA Systems

Since the Multiple-Input Multiple-Out-put (MIMO) systems can greatly increase system capacity, and the Orthogonal Frequency-Division Multiplexing (OFDM) can effectively confront the multi-path fading of radio channel, the MIMO-OFDM systems that combine these two technologies are regarded as a major scheme for PHY in next generation wireless communication system. And Code-Division Multiple Access (CDMA), as an access technology that can provide flexible access fashion and higher frequency reuse in multi-cell environment, can combine with the other two technologies mentioned before to construct new access schemes which have favorable application foreground.In this thesis, the author mainly works on the code design area of CDMA based MIMO-OFDM systems that combines these three above mentioned key technologies, as well as the subcarrier adaptive allocation technology over Multi-carrier CDMA (MC-CDMA) systems that combines CDMA and OFDM technologies. And the main tasks and innovations include: Based on the space-time-frequency spreading (STFS) code—Coupled orthogonal code (COC) that specially designed for CDMA-based MIMO-OFDM systems, this thesis proposes two generation schemes for COC to meet the requirements in different situations, they are Extended scheme and Rotated scheme respectively. In this thesis the author compares the codes that generated by these two schemes with traditional orthogonal codes, and the simulation results demonstrate that the new schemes can provide better system performance. For MC-CDMA systems, this thesis proposes two subcarrier and user allocation schemes systems: A Unitary Subcarrier Allocation Scheme and Proportional Fairness-based User and Subcarrier Allocation Scheme. And through system performance simulation, the results also prove that these two schemes are superior to the traditional schemes respectively.The contribution of this thesis is that for CDMA-based MEMO-OFDM systems the new COC design schemes not only provide more flexible design scheme, but also break the limit of Walsh-Hadamard code, improving the system frequency efficiency; for MC-CDMA systems, this thesis introduces the conceptions of group and user fairness, based on which the schemes have a great advancement on allocation efficiency, user balance.