Section 7.6. Summary

7.6. Summary

UWB systems are inherently overlay systems, so that coexistence is a fundamental issue. Coexistence requires the interference question be addressed from both the narrowband and UWB point of view. Although the FCC-stipulated emission limit from any single UWB radio is rather small, the aggregate effect from multiple radios can be large, both on victim narrowband systems, as well as on wideband systems, including other UWB systems. We have derived the conditional BER of a victim narrowband radio, given interference from multiple UWB sources in addition to AWGN. This quantifies the impact in terms of an impairment factor that depends upon the the signal-to-interference bandwidth ratio as well as the traditional signal-to-interference power ratio (SINR). In order to analyze the impact of aggregate interference, we have derived the interference asymptotic pdf. We also developed expressions for the BER of narrowband signals on a UWB radio, and found Chernoff bounds on the BER of a UWB system, in the presence of interference from other UWB radios. Our analysis explicitly takes into account the effect of duty-cycling the radios. Tradeoffs in the robustness to interference of time-hopped and DS-type radios were considered.