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2011
Conference Paper
Titel
Distributed interference alignment in cellular systems
Titel Supplements
Analysis and algorithms
Abstract
We characterized the degrees of freedom of cellular systems with an arbitrary number of antennas per base station and per user. We assumed a fast fading environment which enabled us to use symbol extensions to increase the dimensions of the available signaling space. Based on the insight achieved by the analysis we proposed two algorithms that possibly achieve the optimal degrees of freedom in cellular systems. In the simulations we found scenarios where the optimal degrees of freedom can be achieved with the proposed algorithms. We demonstrated that even if the optimal degrees of freedom can not be achieved, in some scenarios, an interference free transmission can be guaranteed. For other scenarios, we saw that even if an interference free transmission can not be guaranteed the proposed algorithms have huge advantages, in terms of sum rate, over uncoordinated schemes. We like to point out the following interesting problems which are left for future work. For arbitrary scenarios a crucial question remains the number symbol extensions and the number streams which are required to achieve the optimal degrees of freedom. Finding an analytic or algorithmic approach to this problem is a promising direction for future work. In this paper we focused on a fixed number of users. Future work may also consider user selections at the base stations. Further, the performance of the algorithms must be accessed under realistic constraints. For instance, one should consider also the rate constrained feedback channel and the limited capacity of the backhaul network as well as delays in the between available channel state information and the actual transmission.
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