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An Efficient Symbol Timing Synchronization Scheme for IEEE 802.11n MIMO-OFDM based WLAN Systems  

Cho, Mi-Suk (Yonsei University)
Jung, Yun-Ho (Korea Aerospace University)
Kim, Jae-Seok (Yonsei University)
Publication Information
Journal of the Institute of Electronics Engineers of Korea TC / v.46, no.5, 2009 , pp. 95-103 More about this Journal
Abstract
An efficient symbol time synchronization scheme for IEEE 802.11n MIMO-OFDM based WLAN systems using cyclic shift diversity (CSD) preamble is proposed. CSD is used to prevent unintentional beamforming when the same preamble signal is transmitted through transmit antennas. However, it is difficult to find a proper starting-point of the OFDM symbol with the conventional algorithms because of time offset by multi-peaks which are result from cross-correlation of received CSD preamble with a known short training symbol. In addition, the performance of symbol time sync. is affected by AGC and packet detection position. In this paper, an optimal symbol time synch. algorithm which is composed of the boundary detection scheme between LTS and OFDM symbols, the verification scheme for enhancement of boundary detection accuracy, and the SNR-varying threshold estimation scheme is proposed. Simulation result show that the proposed algorithm has performance gains of 4.3dB in SNR compared to the conventional algorithms at the rate of 1% sync. failure probability for $2{\times}2$ MIMO-OFDM system and 18dB at 0.1% when maximum frequency offset exists. It also can be applied to $4{\times}4$ MIMO-OFDM system without any modification. Hence, it is very suitable for MIMO-OFDM WLAN systems using CSD preamble.
Keywords
MIMO-OFDM; WLAN; Symbol time synchronization; CSD;
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