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

原则上可以通过经由相应的介质接入方案在时间和频率上正交化传输来对抗不同通信链路之间的干扰。然而，现有技术的干扰减轻技术能够通过经由组合的线性空间处理和功率控制联合地优化链路的集合来提供高得多的频谱效率。在这方面，最突出的方法相对于发射功率的限制来优化单个用户传输的信号干扰噪声比（SINR）、均方误差（MSE），反之亦然。这两个指标可以相互联系，而它们都与可实现的数据速率有关，这对网络运营商来说特别重要。这些技术由于在这些设置中增加了空间自由度的数量而非常适合与利用协作基站的新颖蜂窝技术结合使用。虽然它们的性能已经得到了很好的研究假设下，完美的知识的信道，完整的信道状态信息（CSI）几乎是在实际设置。除了CSI的损伤的经典来源之外，有限的速率反馈在频分双工（FDD）系统中，协作方案引入了新的恶化源，例如速率和等待时间的回程限制。此外，每组天线的多个发射功率约束的集成导致特别具有挑战性的优化问题。在本文中，我们首先给出了自上次项目报告以来的最新成果的更新。我们占我们的新的强大的合作干扰缓解技术，信道信息是不完全可用。根据最新的项目阶段，解决分布式合作传输，我们提出的解决方案w.r.t. CSI准确性和干扰减轻。此外，我们提出了一个新的项目阶段，其中包括在不完善的CSI条件的背景下存在的进一步方面。我们相信，在这个额外的阶段完成项目的调查，这样的合作干扰缓解在不完美的CSI条件下的主要挑战已经得到解决。

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.