Research On Key Techniques And Applications Of Broadband Impulse Radio Communications

Impulse Radio (IR) is the oldest wireless communication technology which candate back to the end of19th century. However, wireless communication tends todevelop towards carrier transmission due to the technical limitations. In the past40years, Impulse radio Ultra-wide band (UWB) systems was first used in military field,such as military radar and some other communication systems with low interceptionrate and low detection rate. From1990s, Scientists have been working on standardizebroadband impulse radio technology for civilian and commercial use. Until thebeginning of21century, many countries opened3.1-10.6GHz and above part ofspectrum resources for commercial use, and then UWB and60GHz technology havebeen developing fast.Broadband impulse radio has become one of the main streams of wirelesscommunication because it has many advantages, such as simple structure, stronganti-interference capability, high security and low power consumption. It has beenwidely used in the fields of wireless sensor networks (WSN), medical systems andprecise positioning systems, etc. In this thesis, based on the existing techniques ofIR-UWB and IR-60GHz systems, some new technologies are proposed as follows,a. The traditional modulation employed in IR-UWB systems, pulse positionmodulation (PPM), needs both time slot and symbol synchronization which increasesthe complexity and power consumption of systems. While differential pulse positionmodulation (DPPM) doesn’t need symbol synchronization at the receiver since everyDPPM symbol ends with a pulse. And it also can provide high transmission rate byremoving redundant time slots. Therefore, DPPM has the advantage over PPM interms of system structure, data rate and power consumption.b. A new modulation, differential pulse position and amplitude modulation (DPPAM) is proposed in this thesis. DPPAM combines DPPM and pulse amplitudemodulation (PAM). According to the theoretical and simulation results,2×N-aryDPPAM can provide UWB systems better performance than DPPM and PPM with thesame modulation dimension, while M×N-ary (M>2) DPPAM provide a compromisechoice between system performance and computation complexity.c. Three pulse design methods are proposed for IR-60GHz systems which arehigh UWB pulse functions, reverse derivation method and spectrum shift methodseparately. According to the study in this thesis, one conclusion is obtained which ispulses with fast-decayed autocorrelation functions can provide IR-60GHz systemswith correlation receiver lower bit error rate (BER) and better capacity.Additionally, the application for impulse radio systems is also studied.a. A selective approach to improve the performance of UWB imagetransmission system is proposed. Image information is divided into key and secondaryinformation after discrete wavelet transform (DWT) process. Key information will betransmitted with good channel condition, while secondary information otherwise. Thethreshold of channel condition can be derived from the cumulative distributionfunction (CDF) of indoor fading distribution. Simulation results show the quality ofthe received images using this approach improves a lot.b. The potential application of IR-UWB in home energy management system ofsmart grid is also analyzed. Home energy management system is introduced first, andthe requirements for wireless technologies in the system are also analyzed. Comparedwith other popular techniques, like Wi-Fi and Zigbee, the advantages of IR-UWB inhome WSN are concluded.