Research On Wireless Transmission Technology Based On Multi-dimensional Spreading

In the wireless communication channel, the presence of time domain selectivefading and frequency domain selective fading restricts the performance of the system;however, the signal spread technology can obtain diversity gain against fading. Thesignal design dimension has been extended to the space, time and frequency domain. Ifthe signal is designed in multiple dimensions, the diversity gain of multiple dimensionscould be got to improve the system performance.The superiority of multiple dimensionsis centralized by multi-dimensional signal spread technology, and it gradually arousesgeneral interest.Theoretically, the multi-dimensional signal spread technology could provide highertransmission reliability and effectiveness. However, the signal processing must beoperated on multiple dimensions. Therefore, firstly the equalization detection algorithmof time domain and frequency domain needs to be studied and the system performanceneeds to be enhanced also. Secondly, as the new interleaving multiple access is differentfrom the traditional code division multiple access, the research of the detectionalgorithm of the interleaving multiple access is required. Thirdly, as the multi-antennainterference has restricted the system performance, the detection algorithm to resist themulti-antenna interference is required. Lastly, with the evolution of technology, thestudy for diversity schemes and its detection algorithms are also inevitable.This thesis works for above-mentioned problems of multi-dimensional signalspread technology as follows:Chapter1introduces the fading channel characteristics and the key technologies ofanti-fading. The major work and structure are also described.Chapter2evaluates the signal spread technology in wireless communicationsystem. The spread technologies in time domain, frequency domain and space domainare all given and evaluated.Chapter3studies multi-dimensional signal spread technology based on orthogonal code. Firstly, with introducing the new multi-antenna technologies to the evolutionsystem of wideband Code Division Multiple Access (CDMA) system, the performanceof all kinds of space-time programs is compared. Then, the Orthogonal Frequency andCode Division Multiplexing (OFCDM) system is studied in detail. With the introductionof new type of multi-antenna technology, an iteration detection algorithm, which couldgreatly improve the system performance, is proposed.Chapter4investigates multi-dimensional signal spread technology based oninterleaver. First, the concept of Interleave Division Multiple Access (IDMA) and thedetection algorithm are all elaborated in detail, and the performance advantage isevaluated compared to CDMA. Secondly, the superposition coded modulation system isstudied in detail, and an iteration detection algorithm is proposed. At last, an interleavediversity scheme is proposed, whose performance and the ability of relay system basedon interleaver that overcomes the problem of asynchronous are all evaluated.Chapter5concludes this dissertation and discusses the possible future researchdirections.