Towards reliable and high data-rate wireless communication systems

近年来，住宅、商业和移动用户将高速互联网接入与语音和视频等实时应用相结合，从而产生了高数据速率的无线通信系统。在这些系统中，由于多径衰落，实现高可靠性是一项非常具有挑战性的任务。最近提出的多输入多输出(MIMO)技术为这一问题提供了解决方案。MIMO传输方案的一个共同缺点是它们在速率和性能之间的权衡不灵活。已经报道了一些工作来解决这个问题，但需要更新的方法来解决移动用户日益增长的数据速率需求。MIMO系统的另一个缺点是由于多个天线的可用性而导致移动接收器的复杂性。为了在今天的多速率无线系统中更有效地利用带宽，信令参数必须适应不同的信道条件和所需的服务质量。因此，必须开发自适应编码和调制，这是包括MIMO-ofdm在内的现代无线系统的标准特征。设计一种新的空时频扩频技术是本课题要完成的另一项重要工作。除了通过分集提高性能外，空时频扩展还在多址调度中提供了更多的自由度。在WiMax标准中分数频率重用的激励下，多址接入调度方案将被开发，以充分利用MIMO ofdm-cdma中增加的自由度。

In recent years, residential, business and mobile users are combining high speed internet access with real-time applications such as voice and video which results in high data rate wireless communication systems. In these systems, achieving high reliability is a very challenging task due to multi-path fading. The recent technology called "Multiple-Input Multiple-Output" (MIMO) promises a solution for this problem.A common drawback of MIMO transmission schemes is that they are not flexible in rate-performance tradeoff. Some work has been reported to address this problem but more novel approaches are required for addressing increasing data-rate requirement of mobile users. Another drawback of MIMO systems is complexity of the mobile receiver due to availability of multiple antennas. To resolve this problem, technologies will be developed to achieve small and low cost mobile units.For more efficient use bandwidth in today's multi-rate wireless systems, signaling parameters must adapt to varying channel conditions and required quality of service. Therefore, adaptive coding and modulation which is a standard feature of modern wireless systems including MIMO-OFDM has to be developed. This is another topic to be investigated in the proposed research.Design of a new Space, Time and Frequency spreading technique for MIMO OFDM-CDMA is another important task to be performed in this project. In addition to improved performance via diversity, space-time-frequency spreading offers increased degrees of freedom in multiple access scheduling. Motivated by the fractional frequency reuse in WIMAX standard, multiple access scheduling schemes will be developed to fully taking advantage of the increased degrees of freedom in MIMO OFDM-CDMA.