Channel and frequency offset estimation for a MIMO-OFDM system

Abstract

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 over 100 Mbps. Before we detect 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 the 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 the 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. 0-7803-8521-7/04/$20.00 (C) 2004 IEEE 1523 0-7803-8521-7/04/$20.00 © 2004 IEEE * m,1 (t) and x m,2 (t)x * m,2 (t). We calculate complex quantities p prc m as follows: p prc m = 63 t=0 x m,1 (t)x * m,1 (t) * x m,2 (t)x * m,2 (t) . (13) 0-7803-8521-7

Multiuser MIMO OFDM Based TDD/TDMA for Next Generation Wireless Communication Systems

“…Following these schemes, M t times K -IFFT for OFDM modulation, M t times K -FFT for OFDM demodulation and M t * K times division are needed to estimate all the spatial channels between all the transmit antennas and the receive antenna. However, M t * L samples must be observed at one receive antenna to estimate the M t spatial channel impulse responses in the time approaches [74,75]. The training sequences transmitted at different antennas only occupy M t * L samples.…”

An Elaborate Frequency Offset Estimation for Ofdm Systems

“…The frequency offset estimation using the CP is included in data packet. A preamble can be also used for frequency offset estimation [20][21][22][23]. A preamble is used for estimating the offset of one packet itself.…”