Downlink Cell Association and Load Balancing for Joint Millimeter Wave-Microwave Cellular Networks

TL;DR

This paper introduces a novel cell association framework for joint millimeter-wave and microwave cellular networks, optimizing load balancing and rate performance by considering blockage and achievable rates.

Contribution

It proposes a new matching-based cell association scheme with minimum quota constraints, improving load balancing and network throughput over traditional methods.

Findings

Outperforms conventional max-RSSI and max-SINR schemes.

Effectively balances user association between mmW and μW base stations.

Achieves higher average sum rate and load distribution efficiency.

Abstract

The integration of millimeter-wave base stations (mmW-BSs) with conventional microwave base stations ($\mu$W-BSs) is a promising solution for enhancing the quality-of-service (QoS) of emerging 5G networks. However, the significant differences in the signal propagation characteristics over the mmW and $\mu$W frequency bands will require novel cell association schemes cognizant of both mmW and $\mu$W systems. In this paper, a novel cell association framework is proposed that considers both the blockage probability and the achievable rate to assign user equipments (UEs) to mmW-BSs or $\mu$W-BSs. The problem is formulated as a one-to-many matching problem with minimum quota constraints for the BSs that provides an efficient way to balance the load over the mmW and $\mu$W frequency bands. To solve the problem, a distributed algorithm is proposed that is guaranteed to yield a Pareto optimal and two-sided stable solution. Simulation results show that the proposed matching with minimum quota (MMQ) algorithm outperforms the conventional max-RSSI and max-SINR cell association schemes. In addition, it is shown that the proposed MMQ algorithm can effectively balance the number of UEs associated with the $\mu$W-BSs and mmW-BSs and achieve further gains, in terms of the average sum rate.