Research On The UWB Range Extension Communication Technology

At present, UWB systems are mainly applied to short range wireless communications with low transmission power. However, the history of UWB technology has proved that the strict power spectral density limit can not guarantee the electromagnetic compatibility of UWB communication. Such factors as relatively low theoretical channel capacity, high processing losses and severe frequency selective fading will greatly restrict the communication rate and distance. The high implementation complexity and high power consumption of the high rate communication system also restrict the promotion and application of the UWB technology. Limitations of UWB technology chiefly used for short-range communications have made it impossible to secure sufficient market space, which is becoming an important constraint for the development and application of UWB technology.To extend the application field of UWB technology, this dissertation conducts a research on UWB range extension communication technology. The research is supported by the subproject"Medium and long range UWB inter-network connection technology"of the National 863 Key Project of China"Development and application demonstration of the UWB wireless communication system", the subproject"Application demonstration of UWB range extension"of the National Science and Technology Major Project of China"Development and application demonstration of carrier-based UWB high-speed wireless communications chips", and the Program for New Century Excellent Talents in University. Through the analyses of the six system design strategies and four network access strategies for UWB range extension communication, we have pointed out that in current UWB range extension communication, there is a lack of link budget assessment, electromagnetic compatibility evaluation and system design strategies for range extension application, and that there exist such problems as low spectrum efficiency. Taking these as starting points, the present research deals with the following issues:1. Some novel methods are proposed for evaluating the performance of the link budget and electromagnetic compatibility for UWB range extension communication system. Based on the available test results, the comprehensive analyses are made of the link budget and interference radius in the UWB range extension communication system, while a comparison is conducted with the IEEE 802.11a system. Under the conditions where UWB signal and other communication signals are treated as equivalent to white Gaussian noise, the electromagnetic compatibility assessment approach based on interference temperature is proposed for the UWB range extension communication system. The relationships between the channel capacity of the UWB system and that of other communication systems with different bandwidths are presented, while the quantitative evaluation of electromagnetic compatibility is implemented. Besides, in view of the relatively high spreading gain in the UWB range extension communication system, the electromagnetic compatibility assessment approach based on time-frequency analysis is proposed for the UWB range extension communication system, and the differences are indicated in electromagnetic compatibility between UWB spread spectrum signals with various time-frequency characteristics. Moreover, the general expressions have been deduced of the relationships between the bit error rate and signal-to-interference ratio of other communication systems with different bandwidths under the interference of the UWB signal equivalent to white Gaussian noise and four UWB spread spectrum signals which pass through AWGN channel. The derived expressions are validated by Monte Carlo simulations. The conclusions can be used as important references for the electromagnetic compatibility performance evaluation and the spread spectrum scheme selection of the UWB range extension communication system.2. The key technologies and system implementation schemes for UWB range extension communication are analyzed. The implementation model for the UWB communication system is established. Based on the researches and application scenario analysis of baseband modulation, anti-multipath processing, spread spectrum and frequency carrier technologies in the UWB communication system, and taking the communication rate, communication distance, implementation complexity and power consumption as the main evaluation criteria, the application scenarios of typical implementation schemes for the UWB communication system are provided. The researches are significant in the implementation scheme selection and optimized design for the UWB range extension communication system. Meanwhile, the specific analyses are made of six UWB communication system design methods suitable for range extension applications.3. Two UWB range extension communication system design methods based on Dechirp are proposed. In view of the problems in the range extension applications, the UWB range extension communication system design method based on Dechirp and sliding correlation is proposed. In order to save time needed for sliding search and enhance the anti-multipath capability, the idea of channelization is introduced, and the UWB range extension communication system design method based on Dechirp and polyphase filter is proposed. In both methods, such factors as the frame structure design, signal detection, synchronization and demodulation are taken into consideration, and the integrated system level simulation models are established. The analyses are made of the bit error rate performance by using OOK demodulation based on energy detection. The Monte Carlo simulation validates the theoretical deduction, and further evaluations are made of the system performance in different transmission channels. Our research group has now completed the design and implementation of the prototypes of the UWB range extension communication systems by means of the two design methods, and they have passed the over 1km distance communication test.4. The network access method for UWB range extension communication based on shared carrier vertical network transformation (SCVNT) is proposed. Through the research status analysis of the dynamic spectrum allocation, vertical handoff and multi-mode base stations, aiming at different optimization objectives, the SCVNT algorithm based on minimum total blocking probability (MTBP) and the SCVNT algorithm based on minimum redundant channel difference (MRCD) are proposed. The cellular system model and user mobility model are established, and using fixed channel allocation and dynamic channel allocation in each network, the theoretical analysis and simulation experiments are made in different user mobility conditions, different distribution of the number of users, different network transformation judgment periods and different thresholds of the redundant channel difference. The theoretical analysis and simulation results indicate that SCVNT algorithm can effectively improve the overall spectrum efficiency in heterogeneous wireless networks, enhance fairness in the resource allocation, and make is possible to achieve a smooth upgrade. With good compatibility and high applicability, it can provide a solution for shared carrier networking of different UWB range extension communication systems.