Enhancing the Spectrum Utilization in the Cellular Band: A Study of GSM Ad-Hoc Inter-Working<br /> DOI: 10.14209/jcis.2004.8

Abstract

There is a strong belief that the spectrum both in the public and private sectors in the United States is getting scarce. This has driven research into developing efficient protocols and mechanisms for improving wireless spectrum utilization. While using more efficient schemes can certainly help improve the spectrum utilization, most of these works ignore the fact that the actual amounts of spectrum utilized by deployed systems on an average, is quite low. In this paper, a network architecture and MAC protocol that enables adaptive spectrum sharing based on the concept of primary-secondary (PS) system is presented. In a PS system, there is a main user or the primary user to whom the spectrum is licensed. Nevertheless operation of secondary systems in conjunction with the primary is allowed and encouraged. The deployment of such systems can be regulated by a central body such as the FCC. Our study uses the well known Global System for Mobile Communications (GSM) for the primary system. The secondary consists of an ad-hoc overlay whose existence is transparent to GSM. The issues involved in achieving this inter-working between GSM and the ad-hoc network are exposed. A novel MAC protocol for the ad-hoc network which we call Ad-hoc Secondary MAC (AS-MAC) is proposed. We show that our AS -MAC improves the spectrum utilization by up to 70%.