Interference management via opportunistic user selection in wireless communication systems

Abstract

In this dissertation, we propose interference management schemes via opportunistic user selection in wireless communications. First, we propose opportunistic interference alignment (OIA) for three-transmitter multiple-input multiple output (MIMO) interference channel (IC). In the proposed OIA scheme, each transmitter has its own user group that consists of $N$ users, and each transmitter opportunistically selects the user whose received interference signals are most aligned. 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 $N_T\ge M$), we prove that each transmitter can achieve $M$ degrees of freedom (DoF) as the number of users in each group goes to infinity ($N\to\infty$), in comparison with the $\frac{2M}{3}$ DoF known to be achievable in the three-transmitter $M \times 2M$ MIMO IC. We also show that the user scaling $N\propto P^{\alpha M^2}$ enables the network to achieve $M$ DoF per transmitter where $P$ is transmit power, and $\alpha$ is the relative path loss of the interfering channel in decibels. Then, we investigates how multiuser dimensions can effectively be exploited for target DoF in interfering broadcast channels (IBC) consisting of $K$-transmitters having a single antenna. In the IBC, each transmitter selects and serves a single user in its user group so that a $K$-user IC is constructed after user selection. Without help of multiuser diversity, $K-1$ interfering signals cannot be perfectly removed in the $K$-user IC since the number of receive antennas at each user is assumed to be smaller than or equal to the number of interferers. Only with proper user selection, non-zero DoF per transmitter is achievable as the number of users increases. Through geometric interpretation of int...