On Number of Almost Blank Subframes in Heterogeneous Cellular Networks

TL;DR

This paper analyzes the optimal number of almost blank subframes (ABSFs) in heterogeneous cellular networks to reduce cross-tier interference, providing a semi-analytical formula and demonstrating benefits through simulations.

Contribution

It introduces a semi-analytical formula to estimate the required ABSFs based on network parameters and user throughput needs, enhancing interference management strategies.

Findings

In macro/femto scenarios, residual ABSF interference is manageable.

In macro/pico scenarios, ABSFs significantly influence the number needed.

Using ABSFs improves victim user performance with minimal impact on high-percentile throughput.

Abstract

In heterogeneous cellular scenarios with macrocells, femtocells or picocells users may suffer from significant co-channel cross-tier interference. To manage this interference 3GPP introduced almost blank subframe (ABSF), a subframe in which the interferer tier is not allowed to transmit data. Vulnerable users thus get a chance to be scheduled in ABSFs with reduced cross-tier interference. We analyze downlink scenarios using stochastic geometry and formulate a condition for the required number of ABSFs based on base station placement statistics and user throughput requirement. The result is a semi-analytical formula that serves as a good initial estimate and offers an easy way to analyze impact of network parameters. We show that while in macro/femto scenario the residue ABSF interference can be well managed, in macro/pico scenario it affects the number of required ABSFs strongly. The effect of ABSFs is subsequently demonstrated via user throughput simulations. Especially in the macro/pico scenario, we find that using ABSFs is advantageous for the system since victim users no longer suffer from poor performance for the price of relatively small drop in higher throughput percentiles.