Channel and frequency offset estimation for a MIMO-OFDM system

An OFDM technique has been utilized for wireless local area networks (WLANs). Spatial division multiplexing using a multiple-input multiple-output (MIMO) technique has been studied to increase the transmission rate to over 100 Mbps. Before we can detect the transmitted data, we need AGC adjustment, timing synchronization, frequency offset estimation, and channel estimation using a preamble. The current WLAN system with a single transmit antenna, based on the IEEE 802.11a standard, uses a four OFDM symbol duration preamble. However, the preamble period proposed so far for the MIMO-OFDM system grows linearly with the transmit antenna number. This results in an increased overhead, and the conventional technique is not efficient. In this paper, we present a channel and frequency offset estimation scheme using a preamble with four OFDM symbol duration for the MIMO-OFDM system in WLANs. This preamble has the same duration as that of the IEEE 802.11a standard, and does not increase the overhead. Computer simulation results are provided to demonstrate the performance of the proposed scheme.