Direction of arrival estimation of WiMedia UWB multipath signals in the presence of inband interferers

Abstract

The increasing popularity of wireless communications is making usable frequency spectrum crowded. We will have to optimally share the spectrum between multiple users to meet this increasing demand. Restricting the transmission to desired direction is one way of optimizing the spectrum usage. By doing this, the power for the desired user is increased while reducing the interfering power for other users of the spectrum. The estimation of direction of arrival of multipath signals would help to decide the optimal transmission directions.

Both shorter range wideband and longer range narrowband systems will have to co-exist in the wireless environment. OFDM based systems are popular for wideband communications. WiMedia Ultra Wide Band (UWB) is a typical example of such a system. These systems will be operating along with narrowband systems like Wimax. This research work looks at estimation of direction of arrival of UWB multipath signals in typical propagation environments in the presence of interferers. The known pilot signals of UWB signals are exploited to develop a new scheme for achieving this. Focussing is used to combine the energy of different frequency components to enhance the threshold of estimation. A new focussing scheme not requiring coarse estimation of the direction of arrival is developed to eliminate the asymptotic bias seen in conventional focussing schemes. The superior performance of the new algorithm is demonstrated through simulation. A new receiver architecture which provides significant savings in required hardware is proposed in the thesis to facilitate economical implementation of the system. The thesis presents a new source enumeration technique suitable for estimating the number of multipaths while using the new algorithm.