Ultra wideband impulse radio signal interference to code division multiple access system

The ultra wideband (UWB) interference to code division multiple access (CDMA) system is analyzed. Two popular UWB modulation schemes, the time hopping pulse position modulation (TH-PPM) and time hopping pulse amplitude modulation (TH-PAM), are considered. The pulse repetition rate (PRR) of UWB impulse radio signal and the frequency band of the CDMA system play the primary roles in the BER performance of the CDMA system receiver in the presence of UWB interference. The characteristics of an aggregation of multiple UWB signals are somehow different from that of a single UWB device, especially for the TH-PPM scheme, where discrete spectral lines maybe exist in the band of CDMA system receiver. The system parameters of TH-PPM such as the modulation index and maximum shift incurred by the time hopping code determine the amplitude of the discrete spectral lines. In multiuser case of TH-PPM, sometimes one discrete spectral line in the band of CDMA system receiver should degrade the BER performance dramatically. It is observed by theoretical analysis and simulations that the interference to CDMA system receiver from single UWB device is very little in common case.