Physical Layer Network Coding in Two-Way Relaying Systems with Multiple-Antenna Relays or Distributed Single-Antenna Relays

协作通信是实现无线系统性能、可靠性和覆盖扩展的一个非常有前途的候选方案。通过中间中继站支持两个节点之间的传输降低了有效路径损耗，但由于半双工约束也限制了频谱效率。为了克服这个缺点，可以应用利用无线链路的广播性质和网络编码原理的双向中继系统。为了彼此交换信息，两个参与的源节点同时向中继器发送它们的消息，并且中继器然后向两个节点发送联合消息，这两个节点可以最终使用先前发送的信息来估计相反的消息。在这种情况下，最具挑战性的任务是基于由两个源消息的叠加给出的受扰接收信号来构建中继消息。在这个项目中，我们的目标是通过应用多天线中继或分布式中继概念来提高系统性能。联合信道解码和物理层网络编码的新方法将被设计用于这两个概念和技术，以利用分布式中继之间的合作将被开发。一个主要的焦点在于在物理层的实现方面，如同步，分布式节点的信道估计以及检测和解码算法。为了证实这些理论研究，双向中继方法的选择将使用实时硬件平台实现。因此，理论和实践中的收益可以进行比较，同时考虑到实施的复杂性。

Cooperative communication is a very promising candidate to realize enhanced system performance, reliability, and coverage extension for wireless systems. Supporting the transmission between two nodes by intermediate relay stations reduces the effective path loss but also limits spectral efficiency due to the half-duplex constraint. To combat this drawback bidirectional relaying systems exploiting the broadcast nature of the wireless link and the principle of network coding can be applied. In order to exchange information with each other the two participating source nodes transmit their messages simultaneously to the relay and the relay then transmits a joint message to both nodes, which can finally estimate the contrary message using the information transmitted previously. The most challenging task in this context is the construction of the relay message based on the disturbed receive signal given by the superposition of both source messages. Within this project, we aim to improve the system performance by the application of multiple-antenna relays or distributed relaying concepts. New approaches for joint channel decoding and physical layer network coding will be designed for both concepts and techniques to exploit cooperation between distributed relays will be developed. A major focus lies on implementation aspects in the physical layer like synchronization, channel estimation for distributed nodes as well as detection and decoding algorithms. In order to confirm these theoretical investigations, a selection of bidirectional relaying approaches will be implemented using real-time hardware platforms. Thus, the gains in theory and practice can be compared taking the implementation complexity into account.