UWB Autocorrelation Receivers Based On Transmitted Reference Technology

In recent years, with the fast development and successful applications in business of wireless communication technologies, our life changes a lot. With the emergence of the third generation and the fourth generation wireless communication systems and the replace of the wired conjunction by Wi-Fi and blue teeth, consumers can connect into a great deal of information at anywhere and at anytime. With the continuous increase of consumers' requirement for higher capacity, faster service and more safer wireless conjunction, we have to look for a new technology in the limited wireless spectrum resources. Ultra wideband (UWB) technologies supply a prospect solution for the coexistence of present wireless systems and avoid the expensive fee of allowance for the spectrum resources.The final purpose of any communications is to receive signals and recover the transmitted information of signals effectively. Preventing from the interference, the transmitted power of UWB systems is limited very low, thus how to design UWB receivers to make it capable of detecting a weak high speed rate UWB signal from the background noises becomes a key problem within the realization of UWB technique. Recently there are two methods of UWB receiver: Rake receivers and UWB autocorrelation receivers based on transmitted reference technology.Rake receivers are constituted by many correlating parts and combining parts, they use diversity receiving multipath to raise the signal-to-noise ratio of the receiving parts. UWB signals have extremely wide spectrum, their extremely wide bandth making receive signals good capable of disfiguring times and declining, and it is easy for UWB to use Rake receivers to realize multipath. But because of the characteristics of UWB signal itself, the design of Rake receivers is more difficult than other wireless systems. Because it is difficult for channel estimate and synchrony, and there are many correlating parts, so it is not suitable for application of the low cost bottom. This thesis uses Matlab simulating ARake, SRake and PRake, and simulations show that the performance of ARake is the best, it can achieve the bottom limit of the ber, but it is not realized; when handling the same multipath ingredients, the ber of SRake is lower than PRake; when handling different multipath ingredients, both ber decrease with the number of multipath ingredients, and it shows that more correlating parts better ber, but the cost is a structure more complicated.Core research of this thesis takes according to UWB autocorrelation receivers based on transmitted reference technology. Its basic thought is transmitting a signal doublet consisting of a reference signal and a modulated data signal, and using the receiver signal of the former as template to demodulate the behind after channel transmission. It needs only autocorrelation receivers rather than lots of Rake correlating parts to capture multipath ingredients; each frame including a reference pulse and a data pulse, and in a frame time, the characteristics of channel keep constant. Both pulses path the same fading, so the transmitted reference pulses provide a good template with the information of channel. It does not need to channel estimate. For each data bit, by transmitting frames to increase bit length, the requirement of synchronous is decreased to only bit synchronous not frame synchronous.The thesis first introduces the transmit signals and receiver model, and adopts the Gaussian approximation to analyze the ber of the three receviers, then uses Matlab to simulate STR and ATR receivers for their key fator (the integral time and the numbers of the average received reference pulses). The simulation adopt the Gauss second derivative pulse, BPSK modulation and multipath channel model recommended by IEEE802.3a. The simulation shows that the ber of STR does not increase or decrease with the integral integration, but there is a so-called integration interval optimization and the performance of ATR can only improve while the number of average received reference pulses is less.The drawback of TR autocorrelation receivers is the adoption of received signals with noises for template, in the correlation additional noises multiply noises items and reference multiply noises items are produced, and they lower the performance of signals. In moving from TR to DTR a 3dB improvement in performance was attained. The thesis introduces a modified DTR based on the research of DTR, which generates a reference by combining two consecutively generated symbol waveforms. It is realized by increase an additional delay line and an addition unit. The simulation adopts the Gauss second derivative pulse, BPSK modulation and multipath channel model recommended by IEEE802.3a. The results show that the SNR of the received reference signals in modified DTR attains 3dB improvement comparing with DTR, and the performance of this system is better than DTR.The last section summarized this dissertation and made prospect of UWB autocorrelation receivers based on TR technologies: how to use sampling expansion approaches to calculate the ber of TR autocorrelation; how to research the performance of TR autocorrelation in the presence of intersymbol interference; how to research the performance of TR autocorrelation under the multiuser circumstance.