Ultra-wideband (UWB) communication using carrierless amplitude phase modulation.
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Ultra-Wideband (UWB) technology can be used for high data rate, very low power communication. Pulse Position Modulated (PPM) based time domain schemes for UWB communication have been investigated in this thesis. When implemented via the time domain techniques, it is usually referred to as impulse radio UWB (IR-UWB). There is currently a need to increase the data rate of IR-UWB systems for them to be considered as a viable alternative to existing short range communication techniques. This thesis develops a time domain based two dimensional phase incoherent Impulse Radio UWB (IR-UWB) communication scheme called pulse position modulated IR-UWB. It is based in part on the concept of carrierless amplitude phase modulation (CAP). Initially, we develop and analyse an IR-UWB system employing an M-ary time orthogonal modulation scheme, namely PPM, in an additive white Gaussian noise (AWGN) channel. Signal detection is based on maximum likelihood (ML) techniques and system performance is evaluated both analytically and by simulation and presented using bit error rate (BER) plots. We then consider M-ary PPM IR-UWB transmission in a multipath channel environment. Both matched filter and Rake receiver structures are considered. Simulation results show that the Rake offers the best performance. To help maintain high transmitted data rates, the thesis develops an M-ary PPM IR-UWB system using a two-dimensional modulation based on the concept of CAP. The resulting scheme is called M-ary PPM-CAP IR-UWB. A Rake is used at the receiver to mitigate the effects of the multipath channel. This thesis focuses on single user phase-incoherent uncoded communication based on these orthogonal modulation formats. System performance results assume an IEEE 802.15.3a multipath channel model. Finally, the thesis develops and evaluates an open loop synchronization technique for PPM-CAP IR-UWB. Synchronization in PPM based systems is equivalent to estimating the start time of a frame. This estimate is obtained by a feed-forward ML detector implemented within the receiver. Symbol synchronization is then obtained by means of a counter operating at the symbol rate that is initiated at the start of a frame and counts to the number of symbols in the frame. Simulation results with ML based synchronization are presented as a function of various combinations of system parameters. Results show that this synchronization scheme provides accurate data frame time estimate with less pilot symbol overhead.