In this paper, we propose opportunistic interference alignment (OIA) for three-transmitter multiple-input multipleoutput (MIMO) interference channels (ICs). In the proposed OIA scheme, each transmitter has its own user group that consists of K users, and each transmitter opportunistically selects the user whose received interference signals are most aligned. Thus, three-transmitter MIMO IC is opportunistically constructed by three transmitters and their selected users. Contrary to conventional IA, perfect channel information for all of the interference links is not required at the transmitter. Each user just needs to feed back one scalar value in the proposed OIA scheme. When the number of receive antennas is N R (with N R = 2M ) and the number of transmit antennas is N T (with N T ≥ M ), we prove that each transmitter can achieve M degrees of freedom (DoF) as the number of users in each group goes to infinity (K → ∞), in comparison with the 2M 3 DoF known to be achievable in the three-transmitter M × 2M MIMO IC. We also show that the user scaling K ∝ P αM 2 enables the network to achieve M DoF per transmitter where P is transmit power, and α is the relative path loss of the interfering channel in decibels. The computational complexity of the proposed OIA scheme is analyzed and compared with conventional user selection schemes.
Lee and Choi REF proposed a three-transmitter MIMO OIA network in which each transmitter has its own user group and only the user at which the interference signals from other transmitters in the network are most aligned is selected.
On the Achievable DoF and User Scaling Law of Opportunistic Interference Alignment in 3-Transmitter MIMO Interference Channels
Mathematics Computer Science