Ofdm Key Technology Research And Its Software Radio Implementation

VHF/UHF wireless communication transmitting requires only moderate transmitting power and reasonable equipment cost, also the channel is very difficult to be destroyed. These merits make its development very promising. Wireless communication systems are expected to provide ubiquitous, high quality, and high-rate mobile multimedia transmission. However, to achieve this objective, various technical challenges must be overcome. For example, the deployment of broad-band wireless access systems would require a transmission technique which can mitigate the detrimental effects of frequency selective fading. In recent years, there has been a lot of interest in applying orthogonal frequency division multiplexing (OFDM) in wireless systems because of its various advantages in lessening the severe effects of frequency selective fading. However, OFDM systems are vulnerable to synchronization errors. For example, carrier frequency offsets, which are caused by the inherent instabilities of the transmitter and receiver carrier frequency oscillators, can lead to severe system degradation due to inter-carrier interference (ICI). Symbol timing synchronization must also be achieved in order to avoid inter-symbol interference (ISI).Base on the study of wireless communication channel characteristics, the article gives an analysis on the existing problems and proposes a solution: Implanting the OFDM technique in a software radio platform. In the article, detailed design architecture is given, together with a comparison among he different algorithms. Further more, a preliminary solution in favor to the black ground of frequency hopping (FH) is suggested after an overall consideration of both performance and cost.In the chapter one, the article gives a brief introduction of the VHF/UHF wireless communication. Some problems encountered are analyzed. OFDM theory and its advantages and disadvantages are also introduced here. The development of software radio and the anticipation of the materialization of OFDM technique on software radio platform are discussed.Chapter two gives a study on the characteristics of the wireless mobile communication channel. Several models are compared under simulations and one model is selected as the base of following discussion.According to the OFDM theory, chapter three gives the block diagrams for the transmitter and receiver for OFDM communication system, transmitting parameters are also given. Frame synchronization and channel estimation under the certain implication are the focus of this chapter. The preliminary OFDM transmitting frame structure and processing architecture are proposed for the frequency hopping application.Chapter four is detailed presentation of our hardware platform, software architecture and the field-test result of our software platform. A summary of the problems we encountered in construction of our system is also organized here.