Researchs On Key Techniques Of Ultra Wideband (UWB) Wireless Communication Systems

This thesis mainly studies the key techniques of impulse-based ultra wideband (UWB) wireless communication systems. It is jointly sponsored by National 863 projects"Study on key techniques of UWB wireless communications"and"Study and development of transmission techniques of UWB wireless communications".The main contents include: the basic principles; multi-path channel models and characteristics; system schemes design and their performance simulations; performance analyses and multi-user code study; coexistence with the IEEE802.11b WLAN narrowband wireless communication system; design and analysis of narrow pulse generators, and finally the RAKE receiver's implementation structures and performances of the impulse-based UWB wireless communication systems.Chapter 1 is the introduction. In chapter 2, the models and characteristics of UWB wireless multi-path channel are presented as the basis of the following chapters. The following chapters 3 to 6 are mainly original research works and worth of reference both in theory and application.Two impulse-based UWB multi-user wireless communication system schemes, each with the link data rate more than 100Mbps, i.e., first the time hopping pulse position modulation (TH-PPM) direct impulse system, and second the direct spreading bi-phase shift keying (DS-BPSK) direct impulse system are designed. Their system performances in indoor multi-path channels are simulated and analyzes. The key design factors are pointed out and main conclusions are given in chapter 3.In chapter 4, system performance analyses are mainly studied. The channel models presented in chapter 2 are used here again for analyzing and simulation. First, the performance and receiver outputs'statistical first-order and second-order distance characteristics of TH-PPM impulse-based UWB systems in indoor multi-user and dense multi-path environment are presented. Then, the BER close expression, which is a direct function of channel parameters, pulse parameters and system user numbers, of the DS-BPSK impulse-based UWB systems in the same environment is derived in detail. Theory analytical results fit the simulation results quite well. Next, the performance of multi-user code is studied and a practical code selection scheme is given. Finally, the receiver output signals are derived, and the system multi-access performance are simulated with Gold sequence and PN codes. Simulation results well prove the scheme.Coexistence property is studied in chapter 5. It is an important research area on theinterference and coexistence of UWB devices with traditional narrow-band systems. The evaluation method and main results provided by FCC are summarized. Then, the interference of IEEE802.11b wireless local area network (WLAN) , which is also an main high speed technique for indoor short range communication in the same 2.4GHz frequency band, to our TH-PPM and DS-BPSK impulse-based UWB systems are analyzed and simulated. The allowable distance between IEEE802.11b device and UWB receiver are derived with the restriction that two UWB transceivers spaced in different distances should achieve certain BER performance so that they can operate correctly.In chapter 6, key modules and their implementation of the base-band transceiver in our presented TH-PPM and DS-BPSK impulse-based UWB systems are studied. The high repeat frequency sub-nanosecond narrow pulse generators, the RAKE and its channel estimator or local match template estimator structures for our TH-PPM and DS-BPSK systems are designed.Parts of the research results have got and applied patents or published in journals and meetings.