On Research And Simulation Of OFDMA Transmission Systems Based On IEEE802.16e Standard

With the fast development of Information Industry, computer and communication technologies continue to merge. The flourish of Internet accelerates the process of mergence. Nowadays the global communication industry displays the traits of Mobility, Broadband and IP-based Architecture. And the appearance of IEEE802.16e meets the trend of development. WIMAX systems that support IEEE802.16e standard hold all the traits of Next Generation Mobile Communication systems. So Mobile WIMAX is a very promising Broadband Wireless Access technology.IEEE802.16e provides specifications for non line of sight, mobile wireless communications in the frequency range of 2-6 GHz. It is well implemented by using OFDMA as its physical layer scheme. Hence OFDMA systems are discussed. The critical technologies of OFDMA systems that support IEEE802.16e are researched in this dissertation. Through theoretical analysis and simulation, the algorithms and processes for OFDMA physical layer are systematically investigated. A relative integrated and feasible scheme is proposed in this dissertation.In Chapter I, the development of IEEE802.16 standard is retrospected, and its technology traits are discussed. After that, the principle of OFDM and OFDMA is briefly introduced, and the advantages and disadvantages of them are investigated.In Chapter II, the transmission principle of OFDMA system that support IEEE802.16e is introduced, and the wireless fading channel for IEEE802.16e is modeled in this chapter.In Chapter III, the influence of synchronization errors in downlink and uplink OFDMA are theoretically analyzed at first. Then the synchronization flow of OFDMA system is proposed, and corresponding synchronization algorithms are introduced. At the second part, channel estimation of OFDMA system is investigated, and a feasible channel estimation scheme is proposed. At last, a simplified channel equalization and soft demodulation algorithm is derived. Also the system simulation results are given.In Chapter IV, the cell-searching problem of OFDMA system is researched. The effective frame detection and cell identification algorithms are proposed. According to these algorithms, the cell-searching processes are constructed. The performances of algorithms and processes are evaluated at the end of the chapter.In Chapter V, the ranging problem of OFDMA system is investigated. The ranging parameters and adjusting aims are discussed at first. Then the fundamental ranging processes are introduced. The effective ranging-code searching and validation algorithms are proposed. And the simulation results of the ranging algorithms are given in the end.In Chapter VI, the encoding and decoding algorithms of LDPC codes supported byIEEE802.16e are researched. Low complexity encoding and decoding algorithms are derived according to the structure of block LDPC codes. Also the performances of LDPC codes are given.