The effects of delay spread on multicode interference cancellation

We study the effects of delay spread on multicode modulation employing interference cancellation. This transmission technique was introduced to improve the signal quality for high-rate (10 Mbps or higher) wireless transmissions over non-line-of-sight frequency-selective fading channels. In this technique, the high-rate data are serial-to-parallel converted into low-rate symbol streams which are then modulated with Walsh and pseudo-noise (PN) concatenated codes. After using a RAKE receiver and fast Walsh transform (FWT) to process the received waveform, interference cancellation stages are applied to lower the bit error rate floor. Numerical results show that notable performance improvement can be achieved even though some multipath components may be too close to be resolved by the receiver. Potential applications of this modulation method include those that require variable and high peak transmission rates such as wireless Ethernet connection for multimedia communications