| Ultra wideband(UWB)communication was first used in the military field.UWB technology has some characteristics,such as low cost,high speed,easy implementation and high robustness to multipath fading,which makes it become one of the key technologies for high speed short range wireless communications since it was authorized for civil use in 2002.The bandwidth of UWB system is from 3.1GHz to 10.6 GHz.According to Shannon formula,UWB technology can achieve higher channel capacity in the same signal to noise ratio(SNR)and have a higher transmission speed than narrowband system.UWB communication has been widely used in wireless personal area network and wireless body area network because of its advantages.The research on UWB communication plays an important role in the future development of wireless communication technology.With the increasing demands of wireless communications,the effective utilization of spectrum resources become a more and more important research topic.Higher bit transmission rate,lower complexity,and more robustness to multipath fading channel and other interferences are the key requirements for the high efficient modulation design in UWB system.The research on UWB high speed communication is mainly divided into two aspects.One is to adopt the M-ary modulation in transmitter,which can transmit more information bits by modulating the amplitude,phase,shape,etc.The other is to transmit the information through multiple transmit antennas.But the conventional high-level UWB modulation schemes always bring high complexity and poor system performance.In order to design the UWB efficient transmission scheme which can optimize the system performance and spectrum efficiency,the main work of this thesis mainly focuses on the following three parts.Firstly,analysis and simulations of the orthogonal complementary code(OCC)-selected based high efficient UWB modulation scheme is given.In this scheme,OCC used as spread code can mitigate the multipath interference and improve the spectral efficiency.The moment generating function(MGF)based theoretical analysis method is given to derive the bit error rate(BER)expression.Then the simulation results under two different multipath channel models are obtained and compared with the traditional transmission scheme to show its superiority.Secondly,we design UWB spatial modulation(SM)scheme to improve the transmission efficiency of multi-antenna UWB system.In the multi-antenna system,the data transmission rate is improved by activating a transmit antenna.At the same time,the system performance can be optimized by the diversity gain of multiple receive antennas.Then,simulation results of the proposed scheme under additive white Gaussian noise(AWGN)channel and multipath channel are obtained.Finally,in order to further optimize the spectral efficiency and BER performance of UWB SM system,the OCC-selected based high efficient UWB SM system is proposed.This scheme combines the characteristics of OCC-selected modulation scheme and spatial modulation technology to achieve better performance.The transmitted bits are sent through three ways to achieve higher transmission speed compared with the previous two schemes.In the aspect of system theoretical performance analysis,the MGF based approach is adopted to derive BER expression.The performance comparisons of this scheme and the UWB SM scheme are shown in simulation results,which shows that this scheme can obtain better system BER performance.In summary,the OCC-selected based high efficient SM UWB system can optimize system performance and improve data transmission rate. |
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