宽带无线通信中发射分集技术的研究-信号与信息处理专业论文.docxVIP

摘 摘 要 《‘33s8主 一～【随着无线话音用户的快速增长、以及Intemet的发展和移动计算设备的应用，使得在以 后时几年里通信技术必须能够提供高速的无线Internet接入。同时数字处理和射频技术的进 步使得小型化集成化终端的使用成为可能。人们对高速率和高质量的无线通信提出越来越高 的需求，然而无线信道系统所处物理环境的限制给可靠的无线通信提出了技术上的挑战。 无线通信中最主要的两个问题是由于传播环境所引起的多径衰落和来自其它用户的同 频干扰。采用分集技术能够有效的对抗无线信道的衰落，为系统提供可靠的信息传输。 在发送端配置多个天线的分集技术是一种有效，并且具有广阔应用前景的对抗无线信道 衰落的分集技术)本文首先介绍了提高平衰落无线通信系统性能的发射分集技术：其次，我 们对适合频率选择性衰落信道的空频码提出了一些独到，就有创新性的想法，并用仿真做了 验证。 首先，我们回顾了提高平衰落无线通信系统性能的发射分集技术。其主要包括了分层空 时码，空时格码和空时分组码。并且对于这些空时码，我们做了大量的仿真，以考察其系统 的性能。 其次，我们对适合频率选择性衰落信道的空频码提出了一些独创性的想法。我们根据空 频码的设计准则，得到达到最大可达分集增益时空频码所满足的充要条件；并根据这个条件， 设计出了一种达到最大可达分集增益的空频码。 ．II． ABSTRACTThe ABSTRACT The rapid growth of wireless voices subscribers，the growth of the Intamat,and the increasing use of portable computing devices suggest that wireless Internet access will rise rapidly over next few years．The push toward higher data rates and higher quality in wireless communications is expected to continue．However physical limitations on wireless channels present a fundamental technical challenge to reliable communications． The two major impairment of wireless communication are the fading caused by destructive addition of multipaths in the propagation scenario and interference from other users．Diversity is the single most important contributor to reliable wireless eommunication． Transmit diversity,multiple antennas at the receiver,is all effective and promising approach． This dissertation introduces the transmit diversity in frequency—flat fading channels and provides some novel ideals oftransmit diversity in frequency-selective fading channels， First，the dissertation provides a review of transmit diversity to improve the performance for frequency-flat fading wireless communications．The layered space-time codes，space-time trellis codes．space-time block codes and some other space-time block codes are introduced．Some results ofthese codes are verifled Wim simulations． Next．We provide some novel ideas for space-frequency codes m frequency-selective fading wireless communications．