Viterbi decoding strategies for 5 GHz wireless LAN systems

Standards for the operation of wireless local area network (WLAN) technology in the 5 GHz band have been developed in Europe, North America and Japan. These systems employ orthogonal frequency division multiplexing (OFDM) technology, and utilize forward error correction (FEC) coding, based on a 1/2-rate convolutional encoder, to combat frequency selective fading caused by multipath channels. This paper examines methods, based on the popular Viterbi algorithm, for maximum-likelihood (ML) decoding of this convolutional code within the WLAN baseband receiver. Although the paper focuses on the European HIPERLAN/2 standard, because of international physical (PHY) layer harmonization, the work is equally applicable to the North American and Japanese WLAN systems. Received error rate results, based on a software simulation of the HIPERLAN/2 PHY layer, are presented for both hard and soft decision decoding strategies. In addition, the effect of quantization on soft decision decoding is investigated. The results highlight the importance of the decoder design on the performance of the WLAN.