Abstract
Orthogonal frequency division multiplexing (OFDM) has been selected as the basis for the new IEEE 802.11a standard for high-speed wireless local area networks (WLANs). We consider doubling the transmission data rate of the IEEE 802.11a system by using two transmit and two receive antennas. We propose a preamble design for this multi-input multi-output (MIMO) system that is backward compatible with its single-input single-output (SISO) counterpart as specified by the IEEE 802.11a standard. Based on this preamble design, we devise a sequential method for the estimation of the carrier frequency offset (CFO), symbol timing, and MIMO channel response. We also provide a simple soft detector based on the unstructured least square approach to obtain the soft information for the Viterbi decoder. This soft detector is very simple since it decouples the multidimensional QAM symbol detection into multiple one-dimensional QAM symbol-and further PAM symbol-detections. Both the sequential parameter estimation method and the soft detector can provide excellent overall system performance and are ideally suited for real-time implementations. The effectiveness of our methods is demonstrated via numerical examples.
Highlights
Orthogonal frequency division multiplexing (OFDM) has been selected as the basis for several new high-speed wireless local area network (WLAN) standards [1], including IEEE 802.11a [2], IEEE 802.11g, and HIPERLAN/2
We provide a simulation example to show the effectiveness of the multi-input multi-output (MIMO) channel estimator and the packet error rate (PER) performance of the MIMO soft detector
Based on the IEEE 802.11a standard, even if only one error occurs in a packet, the entire packet is discarded.) In Figure 6, we show the 104 Monte Carlo simulation results of the PER performance of our soft detector as a function of the signal-to-noise ratio (SNR) for the MIMO system, with tr being 50 nanoseconds for the Chayat channels, when the transmission data rate is 108 Mbps
Summary
Orthogonal frequency division multiplexing (OFDM) has been selected as the basis for the new IEEE 802.11a standard for highspeed wireless local area networks (WLANs). We propose a preamble design for this multi-input multi-output (MIMO) system that is backward compatible with its single-input single-output (SISO) counterpart as specified by the IEEE 802.11a standard Based on this preamble design, we devise a sequential method for the estimation of the carrier frequency offset (CFO), symbol timing, and MIMO channel response. We provide a simple soft detector based on the unstructured least square approach to obtain the soft information for the Viterbi decoder This soft detector is very simple since it decouples the multidimensional QAM symbol detection into multiple one-dimensional QAM symbol—and further PAM symbol—detections. Both the sequential parameter estimation method and the soft detector can provide excellent overall system performance and are ideally suited for real-time implementations. Keywords and phrases: MIMO system, OFDM, WLAN, symbol timing, carrier synchronization, channel estimation
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