Degrees of freedom for the constant MIMO interference channel with CoMP transmission

Abstract

The multiple-input multiple-output (MIMO) interference channel (IC) is considered with constant channel coefficients, N transmit and receive antennas at each user, and coordinated multipoint (CoMP) transmission, in which each message is jointly transmitted by M t successive transmitters. It is shown that the degrees of freedom with CoMP transmission using a two stage scheme involving both zero forcing (ZF) and interference alignment (IA) can be significantly greater than without CoMP transmission. In particular, all AT-users can achieve d degrees of freedom almost surely if d ≤ ⌊2N/K-M t ;1⌋ and M t ≤ K − 2. Additionally, the first M t − 1 users can achieve d 1 degrees of freedom and the last K − M t ; 1 users can achieve d 2 degrees of freedom almost surely if d 2 ≤ ⌊2N/K-M t ;1⌋, M t ≤ Κ-2, and d 1 ; (K − M t ; 1)d 2 ≤ 2N. Next, the analysis of the constant MIMO IC with CoMP transmission is applied to the development of iterative algorithms to design transmit and receive vectors analogous to those without CoMP transmission. The degrees of freedom analysis is shown through simulations to provide a good guideline for choosing how many beams each user should send.