Integrating Sub-6 GHz and Millimeter Wave to Combat Blockage: Delay-Optimal Scheduling

TL;DR

This paper proposes an integrated scheduling approach for sub-6 GHz and mmWave networks to minimize delay, demonstrating significant delay reductions and improved performance over existing policies through theoretical analysis and numerical results.

Contribution

It introduces a threshold-based scheduling policy for integrated sub-6 GHz and mmWave systems, optimizing delay performance under intermittent connectivity.

Findings

Threshold policy is optimal for delay minimization.

Integrating sub-6 GHz reduces delay by up to 70%.

Proposed policy outperforms MaxWeight in delay reduction.

Abstract

Millimeter wave (mmWave) technologies have the potential to achieve very high data rates, but suffer from intermittent connectivity. In this paper, we provision an architecture to integrate sub-6 GHz and mmWave technologies, where we incorporate the sub-6 GHz interface as a fallback data transfer mechanism to combat blockage and intermittent connectivity of the mmWave communications. To this end, we investigate the problem of scheduling data packets across the mmWave and sub-6 GHz interfaces such that the average delay of system is minimized. This problem can be formulated as Markov Decision Process. We first investigate the problem of discounted delay minimization, and prove that the optimal policy is of the threshold-type, i.e., data packets should always be routed to the mmWave interface as long as the number of packets in the system is smaller than a threshold. Then, we show that the results of the discounted delay problem hold for the average delay problem as well. Through numerical results, we demonstrate that under heavy traffic, integrating sub-6 GHz with mmWave can reduce the average delay by up to 70%. Further, our scheduling policy substantially reduces the delay over the celebrated MaxWeight policy.