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Adaptive equalization techniques for the mitigation of multipath effects in OFDM based wireless transmission systems.

机译：缓解基于OFDM的无线传输系统中多径效应的自适应均衡技术。

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摘要

Broadband wireless access is rapidly gaining ground as the technology of choice for voice and high speed data communications. The wireless channel is distinct and unpredictable because of factors such as shadow fading, multipath fading, Doppler spread and time dispersion. Due to the time-varying nature of radio channels, their multipath characteristics, and the demand for high transmission data rates, equalization schemes with fast convergence times are an essential requirement for conservation of end-to-end bit error rate. Several techniques exist to reciprocate the effect of these channel impairments. One such technique for adaptive equalization using quantized state methods, developed by Kumar and Moore, has been studied and its characteristics have been compared and contrasted with conventional equalization methods. The compromise between counter-active equalizer attributes of implementation complexity and convergence rate has been analyzed through simulation. A reference system based on an 802.11a OFDM modem has been used as a vehicle to demonstrate the effectiveness of these novel equalization methods in the presence of artifacts peculiar to a 5GHz mobile radio channel. Despite reduced convergence rates these equalization techniques provide extremely competitive bit error rate performance at a fraction of the original implementation cost. Simulation results also elucidate significant bandwidth conservation by allowing the system to operate at effectively double the specification prescribed data rates with only slight bit error deterioration. The gargantuan computational effort required by least-squares based recursive adaptive algorithms makes them extremely prohibitive for commercial applications. In this context the quantized state techniques present themselves as an ideal candidate for channel equalization in wireless systems.
机译：宽带无线接入作为语音和高速数据通信的首选技术正在迅速普及。由于诸如阴影衰落，多径衰落，多普勒扩展和时间分散之类的因素，无线信道是独特且不可预测的。由于无线电信道的时变性质，它们的多径特性以及对高传输数据速率的需求，因此具有快速收敛时间的均衡方案是保存端到端误码率的基本要求。存在几种技术来抵消这些信道损伤的影响。已经研究了一种由Kumar和Moore开发的使用量化状态方法进行自适应均衡的技术，并且已将其特性与常规均衡方法进行了比较和对比。通过仿真分析了实现复杂度和收敛速度的反主动均衡器属性之间的折衷。基于802.11a OFDM调制解调器的参考系统已被用作一种车辆，以证明在5GHz移动无线信道特有的伪像存在下，这些新颖的均衡方法的有效性。尽管收敛速率降低，但是这些均衡技术以极低的原始实现成本提供了极具竞争力的误码率性能。仿真结果还通过允许系统有效地以两倍于规范规定数据速率的速率运行，而仅轻微地降低了比特误差，从而显着节省了带宽。基于最小二乘法的递归自适应算法所需的庞大计算量使其对于商业应用极为不利。在这种情况下，量化状态技术将自己呈现为无线系统中信道均衡的理想候选者。

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  • 作者

    Khan, Mubeen Shahid.;

  • 作者单位

    California State University, Long Beach.;

  • 授予单位 California State University, Long Beach.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 M.S.
  • 年度 2006
  • 页码 136 p.
  • 总页数 136
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;
  • 关键词

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