| Summary: | 碩士 === 國立交通大學 === 資訊科學與工程研究所 === 96 === DUE to the explosive growth demand for wireless communications, the next-generation wireless communication systems are expected to provide ubiquitous, high-quality, high-speed, reliable, and spectrally-efficient. However, to achieve this objective, several technical challenges have to be overcome attempt to provide high-quality service in this dynamic environment [1].
Orthogonal frequency division multiplexing (OFDM), one of the multi-carrier modulation schemes, turns out to be a strong candidate for the future wideband wireless systems because of its high spectral efficiency and simplicity in equalization. However, OFDM also has its drawbacks. The notable issues of OFDM system are more sensitive to synchronization errors than single carrier system [2], [3]. Most OFDM synchronization methods have one or some of the following limitations or drawbacks: have a limited range of operation, address only one task, have a large estimation variance, lack robust sync detection capability, and require extra overheads [4].
In this work, we introduce a timing synchronization algorithm for 4*4 MIMO-OFDM systems, and try to solve the problem which the signal power will enlarge or decade cause by multi-path channel. This problem will cause sampling phase error. Assume a multiphase generator is used to generate 22 different phases between one clock cycles, the difference between ideal sampling phase and sampling phase determined by this work is 3. Ten L-STS (Legacy Short Training Sequences) are defined in the 802.11n specification, we will perform timing synchronization by used four L-STS in multi-path channel environment and seven L-STS in time variance channel environment. Half L-STS will be used in multi-path channel, and full L-STS will be used in time variance channel.
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