自适应技术在OFDM-UWB系统中的应用研究

【作者】 陈哲；

【导师】 王德强；

【作者基本信息】 山东大学 ， 通信与信息系统， 2007， 硕士

【摘要】 超宽带技术是一种新兴的无线宽带通信技术。与传统的窄带系统相比，超宽带技术具有低成本、低功耗、高传输速率和良好的多径分辨能力等优点，在商业、家庭和个人多媒体网络设备方面都有很好的应用前景，因而近年来倍受业界关注，而且IEEE已经将超宽带技术作为高速无线个域网物理层的实现方案。虽然超宽带技术具有巨大的优势，但就现在的研究情况而言仍然面临诸多挑战，如：针对短脉冲而进行的天线设计和同步方法；由于多址干扰和窄带干扰而造成的性能下降；如何利用高阶调制方案来改善吞吐量；如何发展链路层和网络层以充分发挥物理层上UWB传输的优势等。本文的研究对象是OFDM-UWB系统中的自适应技术。我们知道经过多径信道传输的OFDM系统，在其子载波上会呈现不同程度的衰落，这是由于信道呈现频率选择性衰落的原因。根据不同子载波的衰落程度，改变其辐射功率或承载的比特数据量都可以有效提高系统性能。在UWB信道环境下，频率选择性衰落会更加严重，而且严格的低辐射功率谱密度规定也说明了适合OFDM-UWB系统的自适应技术一定具有不同于传统自适应技术的独有的特点。本论文就是由此出发，经过研究得到了自适应子载波选择与功率分配方案和两种比特分配方案，并通过系统仿真对方案的性能做出评价。更多还原

【Abstract】 Ultra-wideband (UWB) technique is a new wireless communication technique. Compared with traditional narrowband communication, it has many advantages such as low cost, low power consumption, high transmission rate and good multipath resolution. So it has fine prospect in commercial, household and personal multimedia network, which makes it attract extensive attention home and abroad. IEEE proposes UWB as the realizing scheme of physical layer in wireless personal area network.Although UWB technique has lots of advantages, there are still many technical challenges in UWB deployment, such as antenna design for and synchronization of very short pulses, performance degradation due to multiple access interference and narrowband jamming, how to employ higher order modulation schemes to improve capacity or throughput, how to develop link and network layers to take advantage of the UWB transmission benefits at the physical layer.Our research object is the adaptive techniques in OFDM-UWB. It’s well known that the sub-carriers of the OFDM system undergoing multi-path will show different fade, because of the frequency selective of channels. Based on the level of fade of sub-carriers, the performance of system should be improved by changing the transmit power or bit number of different sub-carriers. The frequency selective fade of UWB will be more serious. The transmit power is very low and the power spectrum regulation is strict. All of the above-mentioned illustrate that there are some unique characters in the adaptive techniques of OFDM-UWB, different from classical adaptive techniques. Started with mis, an adaptive sub-carrier selection and power allocation scheme and two bit allocation schemes are obtained after analysis, and evaluated after simulation.更多还原