Research On Key Technologies Of UWB Communication Systems Based On Parallel Combinatory Spread Spectrum

Toward the need of high-speed radio service, relying on the National Natrual ScienceFoundation project, combined with the virtue of parallel combinatory spread spectrum (PCSS)communication system and UWB communication system, the UWB communication systembased on parallel combinatory spread spectrum (PCSS-UWB) is established. To promote theworking performance and the communication security, some remarkable works onmodulation and demodulation, data-sequence mapping and demapping, time-hoppingmultiple access and other aspects have been done. The main contributions are concluded asfollows:Firstly, PCSS-UWB communication system is established. On the basis of multi-pulseposition modulation (MPPM) and multi-pulse amplitude modulation (MPAM), the theoreticalanalysis and simulation results show that the non-uniform distribution of the PCSSmodulation signal has different impacts on demodulation performance and system bit errorate (BER) performance. Furthermore, the MPAM system with joint receiver is proposed.This system combines pulse correlator and pseudo-noise sequence correlator with onedecision device, simplifies the system structure. The formula of this system’ BERperformance is given; and the simulation results show its validity and this improved MPAMsystem has better working performance.Secondly, an improved r-combinatory method, called controllable r-combinatorydata-sequence mapping algorigthm is proposed and appled to the PCSS-UWBcommunication system. On this basis, to improve the mapping efficiency, three newdata-sequence mapping algorithms are proposed: r-combinatory with reference sequence,r-combinatory with weighted sequence, r-combinatory with weighted sequence position. Allthree of them can not only improve the mapping efficiency and the rate of informationtransmission of the system; but also can greatly promote the communication security of thePCSS-UWB system.Thirdly, analyze two parallel combinatory spread spectrum parameters. Show how theyinfluence the PCSS system and the PCSS-UWB system differently, and point out that thereason why they have different charateristics in the two likely systems is that they havedifferent impart on the received energy of the correlators of pseudo-noise sequences. According to it, the selection rule of the two parameters is given. Then, new properties ofpseudo-noise sequence have been detected in the PCSS-UWB system. To analysis these newproperties, define it as added correlation property. Take Gold sequences, Walsh sequences,m_W sequences and chaotic spread spectrum sequence etc into consideration, analyze theiradded correlation property. And then apply these sequences into PCSS-UWB system; thesimulation results indicate that sequences’ added correlation property can representsequences’ performance well in PCSS-UWB system.Finally, PCSS-UWB system using time-hopping multiple access is proposed to study itsmulti-address performance. The theoretical and simulating results show that the MPAMPCSS-UWB system perfoms much better than the MPPM PCSS-UWB system, which is farsuperior to the conventional UWB system. And then, the BER performance formula of theimproved MPAM PCSS-UWB system with joint ceveiver is derived under the situation ofexstance of multi-users. The formula is not only limited to time-hopping multiple access, butalso is able to be adopted by direct sequence spread spectrum multiple access; also it explainsthe five main factors which are playing an important role of influencing the system’smulti-address performance. Compared with MPPM and MPAM systems, the improvedMPAM system with joint receiver also has a better working performance in multi-userinterference environment.