| Ultra-wideband radio, conveying data by transmitting narrow pulses without carrier, is a promising communication technology. Transmitted reference method can work with cross-correlation receivers, which have simple channel estimation and multipath diversity acquirement as well as low sampling frequency, to make a low cost application available. Optimal and suboptimal single user receivers for ultra-wideband transmitted reference (UWB TR) systems in multipath environments are derived, based on both the average likelihood ratio test and generalized likelihood ratio test. These theoretically derived receivers are compared to the ad hoc cross-correlation receivers in structures and bit error probability (BEP) performance.; A weighted cross-correlation receiver is obtained by applying a weighting function which has a priori channel information to a conventional cross-correlation receiver to improve the BEP performance with restrictive receiver complexity. How to construct of a theoretical-weighting function and a rectangular-weighting function as well as the performance improvement by using weighted cross-correlation receivers are discussed in detail. This thesis also proposes a generalized UWB TR signal model which combines the traditional TR and differential TR (uses the previous data-modulated pulse as a reference by utilizing the differential encoding method) techniques to increase power efficiency and improve BEP. In addition, this generalized TR scheme can transmit data by using either binary or M-ary modulation. In the binary system, transmitted signals are designed so that the noise level in a correlator template can be reduced within a restrictive complexity. The M-ary modulation approach with a conventional or weighted cross-correlation receiver can enhance the BEP performance by transmitting data bits through block codes instead of repetition codes.; The multiple access performance of TR and differential TR systems with rectangular-weighted cross-correlation receivers is evaluated in multipath environments. The structure and probability distribution of the multiple access interference are studied, and the closed-form solution of BEP is theoretically analyzed under the Gaussian multiple access interference assumption. |
