ITR: Cooperative Communication Schemes for Wireless Networks

在无线网络中，邻近的多个通信设备形成自然的分布式天线阵列。如果一组这样的设备以某种协作的方式发送和接收，则可以显著提高系统性能。这项研究探索了使用多个设备进行协作发送和接收的技术。这种协作通信方法不同于传统的阵列处理，因为通信节点的分布式特性要求面向网络的设计方法和处理算法。特别是，将考虑允许利用集群中其他节点提供的信息的分布式和异步处理的技术。对于协作传输，将使用分布式空时编码来利用分布式阵列提供的发射分集。分布式空时编码的一个关键问题是节点之间只能实现粗略的同步。因此，需要考虑异步设置中的空时编码。这就需要研究异步分集和编码增益分析、符号波形设计以及在发送端同步的复杂度和译码过程的复杂度之间的权衡。对于协作接收，将采用分布式迭代译码来获得接收分集优势。在该方法中，多个节点通过协作处理接收信号来形成分布式天线阵。通过在分布式解码过程中交换信息，节点能够从信道中提取分集并对消息进行解码。这种方法的主要障碍是节点之间可以共享海量信息。这个问题可以通过使用迭代译码从每个节点的接收信号中提取重要信息来解决，并且只将该信息传递给其他节点。然后，每个节点将利用来自其他节点的信息来执行进一步的译码，以获得由附加信息提供的分集优势。目的是开发分布式处理技术，使我们能够从多个接收节点接收的信号中获得最大程度的分集优势，同时要求节点之间的信息交换最少。为了使上述协作通信方案发挥作用，必须设计一种控制信令策略来允许节点之间共享信息。更重要的是，系统的物理层通信性能将取决于控制信令策略。因此，这一信令设计问题将被一种跨层设计方法解决。将制定采用所提出的协作通信方案的系统设计的分析指南。这项研究的预期结果可用于许多不同的商业和军事通信网络，如蜂窝和传感器网络。

In a wireless network, multiple communications devices in close proximity form a natural distributed antenna array. If a group of such devices transmit and receive in some cooperative manner, then the system performance can be significantly improved. This researchexplores techniques for cooperative transmission and reception using multiple devices. This cooperative communication approach is differentfrom traditional array processing because the distributed nature ofthe communication nodes calls for network-oriented design approaches and processing algorithms. In particular, techniques that allow distributed and asynchronous processing that utilizes information provided by other nodes in a cluster will be considered.For cooperative transmission, distributed space-time coding will be employed to take advantage of transmit diversity provided by the distributed array. One crucial issue for distributed space-time coding is that only rough synchronization between the nodes can be achieved. Hence space-time coding in an asynchronous setting needs to be considered. This leads to research on asynchronous diversity and coding gain analysis, symbol waveform design, and tradeoff between the complexity of transmitter synchronization and complexity of the decoding process.For cooperative reception, distributed iterative decoding will be employed to obtain diversity advantage in reception. In this approach, multiple nodes form a distributed antenna array by collaboratively processing a received signal. By exchanging information in a distributed decoding process, the nodes are able to extract diversity from the channel and decode the message. The main obstacle to this approach is that there is a vast amount of information that can beshared between the nodes. This problem can be solved by using iterative decoding to extract important information from the received signal at each node, and only this information is passed to other nodes. Each node will then utilize the information from other nodes to perform further decoding to obtain the diversity advantage provided by the additional information. The objective is to develop distributed processing techniques that allow us to obtain the maximum degree ofdiversity advantage from the signals received at multiple receiving nodes, while requiring a minimum amount of information exchange between the nodes.In order to make the above cooperative communication schemes work, a control signaling strategy has to be designed to allow sharing of information between nodes. More importantly, the physical-layer communication performance of the proposed system will be dependent onthe control signaling strategy. Therefore this signaling design problem will be attacked by a cross-layer design approach.Analytical guidelines for designing systems employing the proposed cooperative communication schemes will be developed. The expected results of this research can be utilized in many different commercial and military communication networks, such as cellular and sensor networks.