Low complexity delay-tolerant space-time block coding

未来的无线系统预计将涉及大量小型、低成本的通信节点，这些节点将广泛分布在城市的基础设施中，以提供真正无处不在的无缝通信和其他服务，如传感器网络。也许这些系统和所有无线通信中最根本的挑战是信道衰落。然而，在这些无处不在的无线系统中，由于成本和尺寸的限制，单个节点可能只配备一个天线。在上述系统中对抗信道衰落的一个强大策略是以分布式方式应用空时分组编码（STBC）：通过使无线节点集群相互中继信号并有效地创建分布式（或虚拟）天线阵列来创建和利用空间分集——每个中继节点充当STBC阵列中的一个天线元件。分布式STBC的一个主要挑战是系统基本上是异步的：来自中继节点的信号往往在不同的时间到达目的地节点。到目前为止，大多数现有的工作都集中在基于恢复的方案上。为了更有效地解决上述挑战，本提案将采用一种更基本和灵活的方法：开发固有延迟容忍（相干或非相干）的编码和调制结构。这样，我们至少把部分问题从接收机转移到了发射机。考虑到大多数无线节点都是由电池供电的事实，同样重要的是确保中继和接收器的低复杂性。该项目的成果将使迄今为止合作分集的主要理论优势在实际无线网络中得以实现。

Future wireless systems are expected to involve a plethora of small, low-cost communication nodes which will be widely distributed in the infrastructure of cities to provide truly pervasive and seamless communication and other services such as sensor networks. Perhaps the most fundamental challenge in these systems as in all wireless communications is channel fading. In these pervasive wireless systems, however, the individual nodes may be equipped with only a single antenna due to cost and size constraints. One powerful strategy to combat channel fading in the above systems is to apply space-time block coding (STBC) in a distributed fashion: creating and harnessing space diversity by enabling a cluster of wireless nodes to relay signals for each other and effectively create a distributed (or virtual) antenna array - with each relay node serving as one antenna element in the STBC array. A major challenge to distributed STBC is that the system is fundamentally asynchronous: signals from the relay nodes tend to arrive at the destination node at different times. Most existing works so far have focused on recerver based schemes. To tackle the above challenge more effectively, this proposal will employ a more fundamental and flexible approach: developing coding and modulation structures which are inherently delay-tolerant (coherent or non-coherent). In this way we move at least part of the problem from the receiver to the transmitter. Considering the fact that most wireless nodes are powered by batteries, equally important is to ensure low complexity both at the relays and at the receiver. The results of this project will enable the so far largely theoretical benefits of cooperative diversity to be realised in practical wireless networks.