Performance of several OFDM transceivers in the indoor radio channels in 17 GHz band

Orthogonal frequency division multiplexing (OFDM) modulation has been proposed for many wireless local area network (WLAN) modems. The multipath phenomenon in the wireless channels causes frequency-selective fading, which can seriously degrade the OFDM system performance. Several techniques used to combat the impact of selective fading in the OFDM systems have been compared. The simplest possibility is the equalization in the frequency domain. The bit and power loading is a very well known and optimum technique. Additionally, the pre-equalization and spreading of the QAM symbols in the frequency domain by the Walsh-Hadamard transform (WHT) have been considered. Newly developed 17 GHz channel models have been used for simulations. Due to the channel model statistics the alternative techniques do not bring a substantial performance gain in comparison to the simple equalization, on the contrary to the results presented by Dlugaszewski and Wesolowski (see Proceedings of the EPMCC 2001, Vienna, 2001).