Throughput enhancement of OFDM based WLANs using space time block codes and time domain least squares channel estimation

HIPERLAN/2 802.11a, 802.11g and HiSWANa wireless local area networks (WLAN) employ coded orthogonal frequency division multiplexing (COFDM) and provide data rates of up to 54 Mbit/s in a 20 MHz bandwidth. In this paper, space-time block coding (STBC) techniques are considered as a means of enhancing the performance of COFDM WLAN. To perform channel estimation for multiple transmit and receive antennas, it is necessary to make transmitted pilot signals orthogonal in space and time. This was achieved using a Hadamard design. A time domain least square channel estimator was used to achieve high performance. Packet error rate (PER) performance results for, the case of 2 Tx and 2 Rx antennas are presented and throughput enhancements are evaluated. It is observed that STBC doubles the link throughput for low SNR values. For the case of an 802.11a/g network, results for different packet lengths are also presented.