Algorithm Based On The Ieee 802.11a Ofdm Transmission System And Some Hardware

Nowadays, the wide application of networks, for instance, Internet, is developing fast in the direction of integrated broadband multimedia, which consists of data, voice, image and so on. Broadband Wireless Access (BWA) technology has become a hot spot of the market because of its many advantages. All kinds of advanced technology in microwave and wireless communications are introduced to BWA. During recent years many kinds of BWA technology are coming out, which mainly consists of 3.5 GHz BWA systems, 26GHz LMDS systems and Wireless Local Area Networks (WLAN).WLAN is generally considered as the 'last mile' in the connection of computers and wired networks. In 1997, IEEE started to frame and to approve WLAN standards, IEEE 802.11. And Orthogonal Frequency Division Multiplexing (OFDM) in IEEE 802.1 la is given more and more attention because of its various advantages in lessening the severe effects of frequency selective fading. This thesis presents the studies of the physical layer of IEEE 802.11 a, which is a packet-based OFDM transmission system. It gives feasible algorithms, and primary implementation of some key modules are discussed as well.Chapter I gives a brief survey of the development of Broadband Wireless Access. After an introduction of the characteristics of wireless access channels, we give out the application traits of OFDM and its basic principles.Chapter II studies the general content of IEEE 802.11 protocol, focusing on the Physical Layer Specifications of IEEE 802.11 a, which tells how the packet-based OFDM frame is composed and formed in burst transmission mode.Chapter III, as the kernel part of the thesis, constructs a system model taking consideration of WLAN fading channels at the very beginning. The quantitative analysis of channel parameter errors to received signals is derived then, and we pay special attention to key modules in OFDM transmission and advance hardware-realizable algorithms, such as Frame Synchronization, Timing Synchronization and Carrier Synchronization. Channel estimation and nonlinear compensation are also discussed. Relative theories of DPLL and Interpolation Filters are added in the end.Chapter IV advances two kinds of proposed systematic schemes of OFDM digital receivers in accordance with IEEE 802.1 la on the basis of the algorithms analysis in Chapter III. The system simulation model is constructed here, and some primary results are achieved. At the same time, it introduces the hardware implementation of an OFDM baseband transmission platform. Implementation of some key modules in OFDM digital receiver is studied as well.