Multiuser Interference Modeling and Suppression for Differential IR-UWB Systems

Project Type: Master/Diploma Thesis
Student: Steiner Christoph

 

 This thesis deals with a frame-differential, transmitted reference (TR), impulse radio (IR) UWB system, operating in a multipath propagation environment causing inter-symbol interference (ISI). Additionally there exists multi-access interference (MAI) due to multiple users transmitting over the same radio channel. In the discussed system, one data symbol is transmitted using a predefined number of UWB pulses. These pulses have a distance in time specified by a time-hopping code and are modulated with an amplitude code, both specific for each user enabling multiuser communications. The main part of this work is the modeling of the MAI and ISI, the investigation of the multiuser suppression capabilities of the discussed IR-UWB system and the development of signal processing multiuser detection (MUD) algorithms. The first challenge is to find an equivalent system model that relates the data symbols of the transmitter to the output of the receiver. The derived single-channel model is used to investigate the performance. Further improvement of the performance is achieved by extending the conventional single-channel system to a multichannel system. An adaptive least mean squares (LMS) algorithm is developed to calculate optimal weighting coefficients for combining the multichannel outputs to obtain an optimized decision variable. The performance results for the different detection techniques are visualized, discussed, and compared among each other.