{J11} H. J. Yang, W.-Y. Shin, B. C. Jung, and A. Paulraj, “Codebook-based opportunistic interference alignment,” IEEE Transactions on Signal Processing, vol. 62, no. 11, p. 2292-2937, June 2014.

[J11] H. J. Yang, W.-Y. Shin, B. C. Jung, and A. Paulraj, “Codebook-based opportunistic interference alignment,” IEEE Transactions on Signal Processing, vol. 62, no. 11, p. 2292-2937, June 2014.

 

Abstract

For the multiple-input multiple-output interfering
multiple-access channels (IMACs), opportunistic interference
alignment (OIA) using the singular value decomposition
(SVD)-based beamforming at each user fundamentally reduces
the user scaling condition required to achieve any target DoF,
compared to that for the single-input multiple-output IMAC.
In this paper, we tackle two practical challenges of the existing
SVD-based OIA: 1) the need of full feedforward of the selected
users’ beamforming weight vectors and 2) a low rate achieved
based on the exiting zero-forcing receiver. We first propose a
codebook-based OIA, in which the weight vectors are chosen from
a predefined codebook with a finite size so that information of
the weight vectors can be sent to the belonging BS with limited
feedforward. We derive the codebook size required to achieve the
same user scaling condition as the SVD-based OIA case for both
Grassmannian and random codebooks. Surprisingly, it is shown
that the derived codebook size is the same for the two codebook
methods. Second, we introduce an enhanced receiver at the base
stations (BSs) in pursuit of further improving the achievable
rate. Assuming no collaboration between the BSs, the interfering
links between a BS and the selected users in neighboring cells are
difficult to be acquired at the belonging BS.We propose the use of
a simple minimum Euclidean distance receiver operating with no
information of the interfering links. With the help of the OIA, we
show that this new receiver asymptotically achieves the channel
capacity as the number of users increases.