Spectrum Allocation in Two-Tier Networks

TL;DR

This paper proposes an optimal decentralized spectrum allocation method for two-tier cellular networks with femtocells, improving capacity by managing interference without centralized planning, and guarantees minimum QoS for users.

Contribution

It introduces a novel decentralized spectrum allocation policy optimized for two-tier networks with frequency division, considering QoS, interference, and hotspot density.

Findings

Optimal spectrum allocation depends on QoS, interference, and hotspot density.

The proposed policy maximizes Area Spectral Efficiency under QoS constraints.

Results demonstrate improved capacity and interference management in two-tier networks.

Abstract

Two-tier networks, comprising a conventional cellular network overlaid with shorter range hotspots (e.g. femtocells, distributed antennas, or wired relays), offer an economically viable way to improve cellular system capacity. The capacity-limiting factor in such networks is interference. The cross-tier interference between macrocells and femtocells can suffocate the capacity due to the near-far problem, so in practice hotspots should use a different frequency channel than the potentially nearby high-power macrocell users. Centralized or coordinated frequency planning, which is difficult and inefficient even in conventional cellular networks, is all but impossible in a two-tier network. This paper proposes and analyzes an optimum decentralized spectrum allocation policy for two-tier networks that employ frequency division multiple access (including OFDMA). The proposed allocation is optimal in terms of Area Spectral Efficiency (ASE), and is subjected to a sensible Quality of Service (QoS) requirement, which guarantees that both macrocell and femtocell users attain at least a prescribed data rate. Results show the dependence of this allocation on the QoS requirement, hotspot density and the co-channel interference from the macrocell and surrounding femtocells. Design interpretations of this result are provided.