**Interference Engineering:** Developed a mathematical model for coexistence analysis in wireless networks composed of both narrowband (NB) and UWB nodes. Our work accounts for the spatial distribution of interferers, and the propagation characteristics of the wireless environment. Specific contributions include:

**Probabilistic Invariance of Aggregate Interference with Application to FCC Rule Making:**Proved that cumulative interference from radiators located at points of a Poisson random set obeys stable laws and possesses a surprising invariance with respect to essentially any fading distribution. Hence, these results are valid for a large class of fading environments and are helpful in characterizing the effect of unlicensed transmitters in the context of rule making by the FCC in the US and equivalent regulatory agencies in Europe and Asia-Pacific.**Spectral Outage:**Characterized the spectrum of the aggregate interference at any location in the Poisson plane, and put forth the new concept of spectral outage probability (SOP). The SOP can be used to quantify and limit the impact of network interference on a given frequency band, and serves as an insightful network design criterion.**Error and Capacity Performance:**Derived the performance expressions (in terms of error probability and channel capacity) for a NB/UWB link subject to cumulative UWB/NB interference, fading, and additive white Gaussian noise (AWGN). Our work generalizes the conventional analysis of linear detection in the presence of AWGN and fast fading, allowing the traditional results to be extended to include the effect of aggregate interference.