Bandwidth-effecient cooperative diversity techniques for wireless systems

无线电信道作为可靠的高速通信的传输介质提出了严峻的挑战。当信号通过无线信道传播时，由于反射和衰减的变化，它会经历时间上的随机波动。信道质量的这种随机变化通常被称为衰落，并且它是无线传输性能差的主要原因。分集通过向接收器提供相同信息的多个副本来提供对抗衰落的有效解决方案，所述相同信息以独立信道增益有效地传输。使用多个发射和/或接收天线的空间分集是最有效和最有吸引力的分集方法。然而，实现全分集增益需要将多个天线放置得足够远，这对于尺寸有限的终端是有问题的。在不使用多个天线的情况下提供空间分集的替代方法是协作通信。这种方法的动机是这样的事实，即从不同的用户到目的地的无线信道可能会独立衰落，用户可以帮助彼此与他们的消息的传输。由于信息被多次传输，一次来自用户本身，然后来自合作用户（或中继），因此可以实现空间分集。协作分集技术被认为是未来无线自组织网络和无线传感器网络的一种非常有前途的解决方案。本文研究的主要内容是开发实用的传输方案来实现协作分集，包括用户协作分集和利用中继和网络编码的协作分集。与以往的工作不同，我们的重点放在高带宽效率的合作计划，以支持高数据速率传输。研究工作包括分析和计算机模拟，以开发和评估新技术的性能。拟议的研究计划的成功应提高加拿大在提供先进的宽带无线通信系统的竞争地位。

The wireless radio channel poses a severe challenge as a transmission medium for reliable high-speed communications. As a signal propagates through a wireless channel, it experiences random fluctuations in time due to changing reflections and attenuation. This random variation of the channel quality is generally referred to as fading and it is the main reason for poor performance of wireless transmission. Diversity offers an effective solution to combat fading by providing the receiver with multiple copies of the same information that are effectively transmitted with independent channel gains. Spatial diversity with the use of multiple transmit and/or receive antennas is the most effective and attractive diversity method. Achieving the full diversity gain, however, requires multiple antennas be placed sufficiently far apart, which is problematic for size-limited terminals. An alternative approach to provide spatial diversity without using multiple antennas is cooperative communications. This approach is motivated by the fact that the wireless channels from different users to the destination are likely to fade independently and users can assist each other with the transmission of their messages. Because information is transmitted multiple times, once from the user itself and then from the partnering users (or relays), spatial diversity can be achieved. Cooperative diversity has been recognized as a very promising solution for future wireless ad-hoc and wireless sensor networks. Developing practical transmission schemes to realize cooperative diversity is the main subject of this proposed research, which includes both user-cooperation diversity and cooperative diversity with the help of relays and network coding. Different from the previous works, our emphasis is placed on the high bandwidth efficiency of the cooperative schemes in order to support high data-rate transmission. The research work includes both analysis and computer simulation to develop and evaluate the performance of the new techniques. The success of the proposed research program should enhance Canada's competitive position in providing advanced broadband wireless communications systems.