Power control in two-tier femtocell networks

• Published in: IEEE transactions on wireless communications Vol. 8; no. 8; pp. 4316 - 4328
• Main Authors: Chandrasekhar, V., Andrews, J.G., Muharemovic, T., Zukang Shen, Gatherer, A.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.08.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptation; Algorithms; Applied sciences; base-station; Cellular; Cellular communication; Costs; distributed; Equipments and installations; Exact sciences and technology; femtocell; Femtocell networks; Frequency; Frequency reuse; Information, signal and communications theory; Instruments; Interference; Land mobile radio cellular systems; macrocell; Macrocell networks; Mathematical models; Mobile radiocommunication systems; Modulation, demodulation; Networks; overlay; Power control; Quality of service; Radiocommunications; Signal and communications theory; Signal to noise ratio; Studies; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); two-tier; Performance evaluation; Mobile radiocommunication; Frequency modulation; overlay; Worst case method; Hot spot; Base station; Wireless telecommunication; distributed; Cell network; two-tier; Algorithm; Frequency reuse; femtocell; Power control; Telecommunication network; Numerical simulation; Overhead line; interference; Signal to interference plus noise ratio; base-station; macrocell
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2009.081386

In a two tier cellular network - comprised of a central macrocell underlaid with shorter range femtocell hotspots - cross-tier interference limits overall capacity with universal frequency reuse. To quantify near-far effects with universal frequency reuse, this paper derives a fundamental relation providing the largest feasible cellular Signal-to-Interference-Plus-Noise Ratio (SINR), given any set of feasible femtocell SINRs. We provide a link budget analysis which enables simple and accurate performance insights in a two-tier network. A distributed utility- based SINR adaptation at femtocells is proposed in order to alleviate cross-tier interference at the macrocell from cochannel femtocells. The Foschini-Miljanic (FM) algorithm is a special case of the adaptation. Each femtocell maximizes their individual utility consisting of a SINR based reward less an incurred cost (interference to the macrocell). Numerical results show greater than 30% improvement in mean femtocell SINRs relative to FM. In the event that cross-tier interference prevents a cellular user from obtaining its SINR target, an algorithm is proposed that reduces transmission powers of the strongest femtocell interferers. The algorithm ensures that a cellular user achieves its SINR target even with 100 femtocells/cell-site (with typical cellular parameters) and requires a worst case SINR reduction of only 16% at femtocells. These results motivate design of power control schemes requiring minimal network overhead in two-tier networks with shared spectrum.