{C11} H. J. Yang, W.-Y. Shin, B. C. Jung, and A. Paulraj, “Opportunistic Interference Alignment for MIMO IMAC: Effect of User Scaling Over Degrees-of-Freedom,” in Proceedings on IEEE International Symposium on Information Theory (ISIT), Cambridge, MA, July 2012, pp. 2646-2650.

[C11] H. J. Yang, W.-Y. Shin, B. C. Jung, and A. Paulraj, “Opportunistic Interference Alignment for MIMO IMAC: Effect of User Scaling Over Degrees-of-Freedom,” in Proceedings on IEEE International Symposium on Information Theory (ISIT), Cambridge, MA, July 2012, pp. 2646-2650.

Abstract

We consider a new opportunistic interference alignment (OIA) for the K-cell multiple-input multiple-output (MIMO) interfering multiple-access channel (IMAC) with timeinvariant channel coefficients, where each cell consists of a base station (BS) with M antennas and N mobile stations (MSs) having L antennas each. In this paper, we propose three OIA techniques: antenna selection-based OIA, singular value decomposition (SVD)-based OIA, and vector-quantized (codebookbased) OIA. Then, their performance is analyzed in terms of user scaling law required to achieve KS degrees-of-freedom (DoF), where S(≤ M) denotes the number of simultaneously transmitting MSs per cell. As our main result, it is shown that the antenna selection-based OIA does not fundamentally change the user scaling required to achieve KS DoF if L is fixed, compared with the single-input multiple-output (SIMO) IMAC case. In contrast, it is shown that the SVD-based OIA can greatly reduce the required user scaling to SNR (K−1)S−L+1 through optimizing weight vectors at each MS. Furthermore, we show that the vectorquantized OIA can achieve the same user scaling as the SVDbased OIA case if the codebook size is beyond a certain value. For the vector-quantized OIA, we analyze a fundamental tradeoff between the quantization level (i.e., codebook size) and the required user scaling.