Enhanced Intercell Interference Coordination in HetNets: Single vs. Multiflow Approach

In this article, we focus on enhanced Inter-Cell Interference Coordination (e-ICIC) techniques in heterogeneous network (HetNet) deployments, whereby macro-and picocells autonomously optimize their downlink transmissions in time and frequency domain and with minimum coordination. This problem is cast as a multi-agent system, in which the macro-and picocells (i.e., agents) learn their optimal transmission strategies (power levels, cell range expansion (CRE) bias and frequency), with minimum information exchange. Specifically, we examine the frequency domain ICIC scenario, and propose a two-level learning procedure in which picocells learn their optimal CRE bias and transmit power allocation, as well as suitable frequency bands for multi-flow transmission. In turn, the macrocell optimizes its downlink transmission by serving its users, while adhering to the picocell interference constraint. To substantiate our theoretical findings, Long Term Evolution Advanced (LTE-A) based system level simulations are carried out. Interestingly, it is shown taht the proposed dynamic multi-flow solution outperforms the single-flow approach. Improvements of 60% in total throughput and 240% in cell-edge UE throughput are obtained in the case of dynamic multi-flow approach with 8 picocells per macrocell.