A SUITABLE CHANNEL EQUALIZATION SCHEME FOR IEEE 802.11B

This paper discusses suitable methods for channel equalization for the IEEE 802.11b wireless LAN standard and the complexity of implementation of channel equalization in a programmable DSP processor. Because of the complementary code keying used for data rates of 5.5 and 11 Mbit/s, a rake receiver is not suitable for this standard, instead the use of a sparse FIR filter is recom-mended. The RAKE receiver and FIR filter are in fact equivalent for direct sequence spread spec-trum (DSSS) modulation, which is the technique used in 802.11b at 1 and 2 Mbit/s. Two schemes for channel estimation are also investigated: LMS adaptive filtering and correla-tion with the spreading sequence. In both cases the 128 symbol preamble of the 802.11b frame is used for channel estimation. The correlation method has been found more suitable for imple-mentation in a DSP processor. 1