Adaptive equalization for 100 Mbps OWSS wireless LANs

This paper utilizes a class of recently developed signaling pulses for 100 Mbps WLAN. Called OWSS (orthogonal wavelet spread spectrum) pulses, they are derived by spreading OWDM (orthogonal wavelet division multiplexing) pulses in the wavelet domain through a suitable family of PN codes. Significant advantages achieved are: wide time and frequency support, multi-user access capability, inherent frequency diversity hence robustness against frequency selective fading, and continuously pipelined operation - unlike OFDM. To effectively mitigate frequency selective multipath fading, equalization at the receiver is essential. Our OWSS receiver uses a forward equalizer (FE) and a decision feedback equalizer (DFE), together with LMS algorithm for adaptation. Theory as well as simulations experiments upon a 100 Mbit/s, 64QAM, OWSS based system over an indoor multipath channel with a maximum Doppler frequency of 5 Hz, show that a low BER can be achieved even without channel coding. Further, the paper demonstrates that the OWSS system passband spectrum is quite efficient.