Least Pair-Wise Collision Beam Schedule for mmWave Inter-Cell Interference Suppression

The narrow beamwidth characteristic in millimeter wave (mmWave) makes the level of inter-cell interference depend on the beams used by adjacent cells, which indicates that a well-designed schedule of the beams in neighboring cells can reduce the inter-cell interference. In this paper, we investigate a time-domain mmWave beam scheduling problem for interference suppression in a two-cell scenario, where each cell may transmit one or multiple beams simultaneously. Specifically, the beams are one-to-one paired between two adjacent cells, and the simultaneous transmission of two beams in one pair can cause severe inter-cell interference, which is referred to as a pair-wise collision. Instead of optimizing the sum rate of network, we minimize the number of pair-wise collision time slots under the constraint of the service demand of each beam. In this way, the channel state information is not required, and the global optimal solution can be found by our proposed least pair-wise collision (LPC) algorithm, which is a recursive algorithm with linear computational complexity. After that, we extend LPC algorithm to more complicated models, including an asymmetric model and a full-dimension model. Finally, simulations are conducted to verify the efficiency of our methodology.