Interference mitigation in multi-antenna systems

Ghaffar, Rizwan

Achieving enhanced spectral efficiency and increased reliability are the leading objectives of upcoming wireless systems. In the pursuit of these objectives, it is imperative to devise strategies taking into account the practical constraints so that the ensuing solutions are implementable in the real world. Our focus in this thesis is therefore on the practical communication systems.

In the first part of the thesis, we consider low dimensional MIMO systems and propose a low complexity intelligent receiver structure for such systems. This receiver is based on the matched filter (MF) outputs and it successfully reduces one complex dimension of the system. We compare the proposed receiver with MMSE receiver and show that the proposed receiver is characterized by full diversity whereas MMSE receiver suffers from a loss of diversity. Moreover the proposed receiver has a coding gain whereas MMSE suffers from a coding loss.
In the second part of the thesis, we look at interference suppression for the cell-edge users in cellular systems. We question the conventional Gaussian assumption for the interference in such scenario and emphasize that this interference has a structure that can be exploited in the detection process. To this end, we propose the extension of the earlier proposed receiver structure to this scenario and study the effect of the strength and rate of interference.
In the last part of the thesis, we consider multi-user (MU) MIMO mode in long term evolution (LTE) systems. We propose a precoding strategy for low resolution LTE precoders which encompass geometrical interference alignment at the base station followed by the exploitation of the residual interference structure by the users. We also look at the equal gain transmission (EGT) characteristic of LTE precoders and show that where EGT has full diversity in single-user mode, it loses diversity in MU mode.

Systèmes de Communication
Eurecom Ref:
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