Robust cooperative spatial processing and power control for interference mitigation in cellular networks

不同通信链路之间的干扰原则上可以通过通过各自的媒体接入方案在时间和频率上正交化传输来对抗。然而，最先进的干扰缓解技术能够通过组合的线性空间处理和功率控制来联合优化链路集合来提供更高的频谱效率。在这方面，最重要的方法优化了单个用户传输相对于发射功率限制的信干噪比(SINR)、均方误差(MSE)，反之亦然。这两个指标可以相互链接，同时它们都连接到网络运营商特别感兴趣的可实现数据速率。由于在这些设置中空间自由度的增加，这些技术非常适合与利用协作基站的新型蜂窝技术结合使用。然而，上述干扰缓解技术需要了解基本的无线电信道。虽然它们的性能已经在完全了解信道的假设下得到了很好的研究，但在实际设置中几乎没有完整的信道状态信息(CSI)。除了CSI的损伤的经典来源，例如频分双工(FDD)系统中的有限速率反馈之外，协作方案引入了新的劣化来源，例如速率和等待时间中的回程限制。此外，每组天线的多个发射功率约束的集成导致了特别具有挑战性的优化问题。在这篇文档中，我们首先给出自上次项目报告以来我们的最新成果。在信道信息不完全可用的情况下，我们提出了一种新的稳健协作干扰抑制技术。根据最新的解决分布式协作传输的项目阶段，我们提出了解决方案。CSI准确性和干扰缓解。此外，我们提出了一个新的项目阶段，该阶段涵盖了在CSI条件不完善的情况下存在的更多方面。我们相信，在这个附加阶段的调查完成了该项目，从而解决了在不理想的CSI条件下合作干扰缓解的主要挑战。

Interference between different communication links can in principle be combated by orthogonalizing transmissions in time and frequency through respective medium access schemes. However, state of the art interference mitigation techniques are able to provide much higher spectral efficiencies by optimizing a collection of links jointly through combined linear spatial processing and power control. In this regard, the most prominent approaches optimize signal-to-interference-and-noise-ratios (SINRs), mean-square-errors (MSEs) of individual user transmissions with respect to limits on the transmit powers or vice versa. Both metrics can be linked among each other, while they are both connected to the achievable data rate, which is of particular interest for network operators. These techniques lend themselves very well for use in conjunction with novel cellular technologies utilizing cooperative base stations due to the increased number of spatial degrees of freedom in these setups.However, the interference mitigation techniques mentioned above require knowledge of the underlying radio channel. While their performance has been well investigated under the assumption of perfect knowledge of the channel, complete channel state information (CSI) is barely available in practical setups. Besides the classical sources of impairments of CSI such as, e.g., limited rate feedback in frequency division duplex (FDD) systems, cooperative schemes introduce new sources of deterioration, such as backhaul restrictions in rate and latency. Additionally, the integration of multiple transmit power constraints per group of antennas lead to particularly challenging optimization problems.In this document, we first give an update on our latest achievements since our last project report. We account for our novel robust cooperative interference mitigation techniques where channel information is only imperfectly available. According to the latest project phase which addresses distributed cooperative transmission we present solutions w.r.t. CSI accuracy and interference mitigation . In addition we propose a new project phase which covers further aspects present in the context of imperfect CSI conditions. We belief that the investigations in this additional phase complete the project, such that the main challenges of cooperative interference mitigation under imperfect CSI conditions have been addressed.