Asymmetric signal processing for indoor wireless LANs

Asymmetric signal processing is introduced and a number of asymmetric structures are proposed for indoor wireless LAN applications. Applied to equalization, an asymmetric structure has both its equalizers, in a two-way link, located at the base station to result in reduced complexity at the portable. A decision feedback equalizer (DFE) would equalize data from the portable while a Tomlinson-Harashima precoder with its forward filter located at the base station (TH-FF) would preequalize transmission to the portable. Methods are proposed for characterizing the DFE and the TH-PF filters using available information at the base station only. Performance results reported include: 1) bit error rate (BER), 2) signal powers; 3) power spectral densities (PSDs); and 4) sensitivity to automatic gain control (AGC). Using today's custom-designed ASIC, the required complexity at the base station appears feasible for up to 20 Mb/s. Potential applications include portable wireless computers and indoor LAN's for the Ethernet standard (>10 Mb/s).