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Achievable Degrees of Freedom of MIMO Cellular Interfering Networks Using Interference Alignment
Bowei ZHANG Wenjiang FENG Le LI Guoling LIU Zhiming WANG
Publication
IEICE TRANSACTIONS on Communications
Vol.E99B
No.12
pp.26002613 Publication Date: 2016/12/01 Publicized: 2016/07/05 Online ISSN: 17451345
DOI: 10.1587/transcom.2016EBP3019 Type of Manuscript: PAPER Category: Wireless Communication Technologies Keyword: cellular interfering networks, degrees of freedom, interference alignment,
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Summary:
In this paper, we investigate the degrees of freedom (DoF) of a MIMO cellular interfering network (CIN) with L (L≥3) cells and K users per cell. Previous works established the DoF upper bound of LK(M+N)/(LK+1) for the MIMO CIN by analyzing the interference alignment (IA) feasibility, where M and N denote the number of antennas at each base station (BS) and each user, respectively. However, there is still a gap between the DoF upper bound and the achievable DoF in existing designs. To address this problem, we propose two linear IA schemes without symbol extensions to jointly design transmit and receive beamforming matrices to align and eliminate interference. In the two schemes, the transmit beamforming vectors are allocated to different cluster structures so that the intercell interference (ICI) data streams from different ICI channels are aligned. The first scheme, named fixed cluster structure (FCSIA) scheme, allocates ICI beamforming vectors to the cluster structures of fixed dimension and can achieve the DoF upper bound under some system configurations. The second scheme, named dynamic cluster structure IA (DCSIA) scheme, allocates ICI beamforming vectors to the cluster structures of dynamic dimension and can get a tradeoff between the number of antennas at BSs and users so that ICI alignment can be applied under various system configurations. Through theoretical analysis and numerical simulations, we verify that the DoF upper bound can be achieved by using the FCSIA scheme. Furthermore, we show that the proposed schemes can provide significant performance gain over the time division multiple access (TDMA) scheme in terms of DoF. From the perspective of DoF, it is shown that the proposed schemes are more effective than the conventional IA schemes for the MIMO CIN.

