On Providing Downlink Services in Collocated Spectrum-Sharing Macro and Femto Networks

TL;DR

This paper analyzes downlink outage probabilities in collocated macro and femto networks sharing spectrum, proposing a decentralized power regulation strategy for femtocells to ensure reliable services and improve spatial reuse.

Contribution

It introduces a novel decentralized femtocell self-regulation strategy based on distance from macro base stations, ensuring reliable downlink services in spectrum-sharing networks.

Findings

Closed-form lower bounds of DL outage probabilities are tight.

The proposed strategy guarantees reliable services while enhancing spatial reuse.

Effective even with dense femtocell deployment.

Abstract

Femtocells have been considered by the wireless industry as a cost-effective solution not only to improve indoor service providing, but also to unload traffic from already overburdened macro networks. Due to spectrum availability and network infrastructure considerations, a macro network may have to share spectrum with overlaid femtocells. In spectrum-sharing macro and femto networks, inter-cell interference caused by different transmission powers of macrocell base stations (MBS) and femtocell access points (FAP), in conjunction with potentially densely deployed femtocells, may create dead spots where reliable services cannot be guaranteed to either macro or femto users. In this paper, based on a thorough analysis of downlink (DL) outage probabilities (OP) of collocated spectrum-sharing orthogonal frequency division multiple access (OFDMA) based macro and femto networks, we devise a decentralized strategy for an FAP to self-regulate its transmission power level and usage of radio resources depending on its distance from the closest MBS. Simulation results show that the derived closed-form lower bounds of DL OPs are tight, and the proposed decentralized femtocell self-regulation strategy is able to guarantee reliable DL services in targeted macro and femto service areas while providing superior spatial reuse, for even a large number of spectrum-sharing femtocells deployed per cell site.