【作者】 金莹；

【导师】 王新梅；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2006， 硕士

【摘要】 超宽带(UWB)是一种以较低的能量来高速发送数据的技术。脉冲无线电是超宽带的最主要形式,它使用脉冲宽度级数为几百皮秒的短脉冲进行通信。由于具有较短的脉冲宽度,相比于传统的窄脉冲通信,它在接收端具有更多的可接收的多径分量。因此,它是多径环境下短距离通信的可行后选者。众所周知,在多径情况下,MIMO系统能够改善系统的性能。特别地,能够利用发送天线和接收天线之间的多径分量来抵抗信道衰落影响,并且改善通信链路可靠性。通过使用空时编码技术,MIMO系统能够同时提供空间和编码增益,因此获得较高的谱效率和明显的性能改进。为了要利用UWB和MIMO的优点,提出了UWB空时编码方案。全文的工作总结如下:首先介绍了IEEE UWB信道模型,调制和多址接入方式,几种不同的rake接收机。具体地给出了分组空时码,分层空时码的编码技术。提出了UWB分组空时码方案并推导了最终统计判决结果。使用IEEE UWB信道模型进行仿真,比较了单天线和两天线系统的性能。提出了UWB分层空时码方案及其译码算法,然后给出了UWB级联分层空时码方案,通过介绍串行级联码的迭代译码算法,推导了UWB级联分层空时码的译码算法,其中的外码为Turbo码。最后仿真比较了不同方案的性能。更多还原

【Abstract】 Ultra Wideband (UWB) is seen to be a technology for delivering very high data rates at very low power spectral densities. The most common form of UWB is Impulse Radio, which communicates using very short pulses, typically on the order of hundreds of picoseconds. Due to the short pulse duration of the pulses, UWB signals have significantly more resolvable multipath as compared to narrow signals. Therefore, UWB is a viable candidate for short range communications in dense multipath environments.Multiple-Input Multiple-Output(MIMO)system is well known for its potential of improving system performance under multipath scenarios. In particular, a large number of propagation paths between transmit and receive antennas can be utilized to combat channel fading effect and gain link reliability. By the use of Space-Time(ST)coding techniques, MIMO can provide both diversity and coding advantages simultaneously, and hence yield high spectral efficiency and remarkable quality improvement.To exploit the advantages of both UWB and MIMO systems, we propose UWB ST coded scheme. All the work can be summarized as follows:The IEEE UWB channel model, the ways of modulation and multiple access and some kinds of rake receivers are introduced here. Space-time coding technology for space-block codes and layered space-time codes are given in detail.Based on the system models of single-antenna DS-UWB, how to obtain multipath diversity are given with the combination of FS rake receiver with MRC(maximum ratio combination). UWB space-time block codes scheme is presented with the finally statistical decision results .The simulation results with IEEE UWB channel model are given to compare the system performance of single-antenna with that of two antennas.The scheme for UWB layered space-time codes are proposed with its decoding algorithm. Then UWB serially concatenated layered space-time codes are presented, then the decoding algorithm of the scheme is given by the introduction of iterative soft-decision decoding algorithm for the serially concatenated system. The simulation results are used to compare system performances of the two schemes.更多还原