Research Of Transmitted Reference UWB Receiver Technology

When designing short distance wireless communication systems for future, the universal characteristic of correspondence and"Connection of anybody in any time and any place"in 3G should be considered. This requests that the new wireless world is the synthesis of present and future wireless communication systems, connecting all kinds of different equipments, including computers and all kinds of recreational facilities. In order to achieve the goal, the new wireless technology is needed. Ultra wideband (UWB) wireless communication system has several advantages, such as high data rate, large signal bandwidth, high robustness in multipath environments, low power consumption, easy to entire digitization and so on, so it has become the preferred scheme for the transmission of mid-and-short distance high speed data transmission at present.The ultimal goal of any communication systems is effectively receiving signal and restoring its information, therefore the receiver technology is a core content of UWB system, and have become an important research field now. Although, UWB system's unique characteristic, such as directly transmitted narrow pulse with unmodulated, makes its receiving method different with the former narrow band system. The receiver design and the receiving algorithm become more important, which are the bottle-neck of receiving the signal effectively and accurately. Because of the use of the ns level extremely narrow pulse and the multipath UWB channel, the complexity and sensitivity of UWB receiver are increased in order to resolve the multipath signal. In addition, the serious frequency selectivity of UWB channel and the low transmitted power limits of UWB system is a great design challenge to the receiver.Rake receiver is mostly used during to its good collecting resolvable multipath components and the improvement of receiving performance. But combing many paths using a Rake receiver significantly increases the complexity of implementation, also the channel estimation is difficult completed for high rate sampling. To overcome these difficulties, Transmitted Reference (TR) technique is applied to UWB systems with demonstrated demodulation capability in unknown multipath channels, which may be advantageous to the practical application. The main research of this dissertation focuses on the receiver performance. Based on the research of the basic transmitted reference (TR) receiver and the differential transmitted reference (DTR) receiver, a modified transmitted reference (MTR) receiver is proposed with the principle research and the performance analysis. In addition, a time reversed technology is used in these transmitted reference systems to enhance the data rate and to resist the inter symbol interference (ISI).This dissertation consists of six chapters. The basic knowledge and the common receiver algorithms of UWB are introduced in the first three chapters; The author's main research work is introduced in the fourth and fifth chapters; The last chapter gives the conclusion of the whole dissertation.The main contents are sum-up as follows.In chapter one, Based on the historical background and research actuality of UWB, the research significance and the contents of the dissertation are given.In chapter two, the fundamental knowledge of UWB is introduced, including UWB pulse choice, modulation as well as channel model, which is the foundation of the following research.In chapter three, UWB receiver technology is mainly investigated. The transmitter and receiver structure is introduced, also the basic principle and algorithms are told. The usual UWB Rake receiver technology is more analyzed subsequently, the transmitted reference receiver is elicited at last.In chapter four, the principle and structure of UWB TR receiver and DTR receiver are researched, and the BER performance of them is analyzed at the same time. On this basis, a modified transmitted reference receiver is proposed in view of ultra-wide band channel accurate static state characteristic, the principle and performance is analyzed in the performance simulation. In addition, the three receiving algorithms are compared in detail.In chapter five, a technique called time reversal is investigated, which can resist inter symbol interference, and it succeeds in applying to the three UWB transmitted reference receivers researched in chapter four for improving the signal data rate and resisting ISI.In chapter six, a summary of the dissertation is given. The suggestion for future research related TR receiving algorithms is put forward. The main contribution of the dissertation are listed as follows.1,A modified transmitted reference receiver model is proposed for UWB communications in a single user multipath environment. Using the accurate static state characteristic of the UWB channel, this receiver transmitted a reference pulse with many data pulses in a bit period. The transmission, propagation and receiving process is detailed analyzed, and the performance is deducted with the simulation analysis. Analysis and simulations show that, because of the only transmitted reference pulse in a bit period, the performance and data rate of MTR receiver is better than that of TR receiver without much complexity increase of the structure; compared with DTR receiver, the MTR complexity of transmitter and receiver is much lower as a result of no use of differential coding and decoding, nevertheless the receiving performance and the data rate is closed to it.2,For the problem of easy to bring ISI with the high data rate of UWB, the time reversal technology which can resist inter symbol interference and improve data rate is researched. After using it to the TR and DTR receiver, the process of using it to MTR receiver is analyzed, also with many performance simulations in different UWB channels. Analysis and simulations show that, using the characteristic of TiR spatial focusing and temporal focusing, TiR can improve the data rate and performance of UWB TR systems with resisting ISI.At the same time, the dissertation have some groping action to the following three questions.(1) The receiving algorithms of TR UWB systems resisting both narrowband interference and inter symbol interference.(2) The high rate transmitted receiving algorithms of TR UWB systems without interference in the multiuser situation.(3) The research and simulation of transmitted reference receiver in IEEE802.15.4 high-speed channel.