The Research Of Ultra-Wide-Band Multiple Access And Time Delay Estimate Algorithm

Along with the development of communication technology, short distance wireless communication develops fast in resent years, and brings conveniences to people. UWB has attracted profound and comprehensive interests. It has a very broad bandwidth, very high data rate, and is suitable for the indoor multipath environment. It is superior to other wireless technologies.This paper first introduces the conception, the characteristic and the present research status of UWB radio. Then introduces the pulse waveform, the architecture of the UWB transceiver, the fading models of the signal, the indoor channel models, at last some multiple access systems are presented as follow.The current UWB multiple access communication systems, such as 2PPM-TH-UWB, 2PAM-TH-UWB, DS-UWB have some drawbacks and do not provide the variable rate service. However, in the next generation communication systems, the variable rate is a basic need. Thus, the hybrid OVSF-TH-UWB is proposed to address the above problems, and a corresponding correlation mask is designed. It uses the OVSF code to reduce the interference and uses the TH code to disperse the collision in time domain. Because UWB transmits the pulses immediately, so it can estimate the timedelay accurately. This makes it suitable for accurate positioning. But it still remains a difficult problem to estimate the time delay in an appropriate time interval. The accustomed method to estimate the delay is sliding correlation, but it is very time-consuming to implement. To improve the sliding correlation method, this paper presents the two-step rapid method to estimate the time delay. First step is to use the RSSI to implement the coarse-grained estimate, and then use the sliding correlation method to implement the fine-grained estimate. In theory, this algorithm can achieve the accuracy of one chip time.