| Summary: | 碩士 === 國立交通大學 === 資訊工程系所 === 93 === Direct Sequence Spreading Spectrum (DSSS) and Orthogonal Frequency Division Multiplexing (OFDM) are widely used in modern wireless communications systems. Unlike the wire channel, wireless communication uses radio as its medium and has more uncertainty with it. Therefore, WLAN frame format generally contains preamble field for packet diction and synchronization.
In this thesis, an efficient automatic gain control (AGC), timing synchronization for DSSS based WLAN defined in IEEE 802.11b\g and 802.11b\a had been proposed. The proposed methods enables a rapid and accurate front-end signal process even under very low SNR, carrier frequency offset multi-path fading and path loss channel by using preamble at the start of every frame. Unlike the general system, the proposed timing synchronization algorithms could work correctly under one times sampling. To get familiar with IEEE standards, simulation platforms were set up with Matlab mathematical software which let us have a chance to probe signals in every place inside the system and visual view of the channel effects. And with this system, our algorithms could be verified. Some simulation results were shown in this thesis and the accomplishment of the proposed algorithms are also verified with these simulation results.
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