High-Resolution Impulse Radio Ultra Wideband Ranging

We propose a high resolution ranging algorithm for impulse radio Ultra-wideband (UWB) communication systems in gaussian noise. We pose the ranging problem as a Maximum Likelihood (ML) estimation problem for the channel delays and attenuations and phase offset at receiver. Then we translate the obtained delay estimates into an estimate of the distance. The ML problem is very non linear and hard to solve. Some previous works focused on finding alternative estimation procedures, for example by denoising. In contrast, we tackle the ML estimation problem directly. First, we use the same transformation as the first step of Iterative Quadratic Maximum Likelihood (IQML) and transform the ML problem into another optimization problem that gets rid of the amplitude coefficients. Second, we solve the remaining optimization problem with a gradient descent approach ("pseudo-quadratic maximum likelihood"). We show that our algorithm performs significantly better than previously published heuristics. We tested the approach on a real non-line of sight system and obtained good accuracy.

I. Introduction

Ultra-wideband (UWB) radio, a new carrierless communication scheme using impulses, is a candidate technology for future communication and ranging applications. Recent progress on both in the technical and regulatory side of this technology has made this possible. The fine time resolution and material penetration capability of UWB signals has created a vision of novel ranging and positioning applications to augment existing narrowband systems operating in dense multipath environments.