Interference alignment aided by non-regenerative relays

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Traditionally, relays are used for range extension in radio communication networks, i.e., for improving the performance in noise limited scenarios. In contrast to this, we will focus on interference limited scenarios. In such scenarios, relays can be used for interference reduction following the ideas of interference alignment. The investigated scenario consists of several pairs of nodes which want to communicate with each other. Furthermore, there are several relays aiding the communication. Especially bidirectional communication shall be considered. In this case, significant performance improvements are possible following the ideas of two way relaying which up to now have not been considered in conjunction with interference alignment. Each node may be equipped with several antennas, but realistically the number of antennas at the relays will be too small to successfully decode all the received information. For this reason we assume linear, non regenerative relays. Going beyond determining the degrees of freedom, questions concerning the required number of relays and relay antennas, the signal processing techniques for the relays and the precoding at the nodes for achieving interference alignment will be answered within the project. Also, numerical performance evaluations helping the improvement of the algorithms for not purely interference limited scenarios, but with significant noise will be carried out. The two project partners will start their research towards the general case of multiple relays with multiple antennas from two special cases of this scenario. The starting point for Technische Universität Darmstadt will be a scenario with a single relay with multiple antennas enabling a joint signal processing at the relay whereas Universität Rostock will start with a scenario with many relays with a single antenna each.