Code division multiple access employing orthogonal filter banks

Abstract

Wavelet filters computed from a wavelet transform are used for encoding, transmitting, receiving, and decoding spread spectrum signals on multiple parallel frequency channels. The transmitter encodes the data stream via a mapping to a basis set of wavelets which are orthogonal across the time domain. The spread spectrum data is parsed from a serial bit stream to several parallel streams. The number of bits per symbol need not remain constant. Signals are created from each symbol by first up sampling by inserting zeros between successive symbols. These signals are passed through a bank of low-pass and high-pass filters derived from a wavelet packet transform. The resulting signal is transmitted in the base band of the transmission system, or transmitted by modulating the carrier of the transmission system. At the receiver, the steps are reversed to recover the symbols. Symbol decisions are made through any one of a number of methods.