Cooperative Mobile Sensing for Dynamic Spectrum Access in Community Cellular Networks

Abstract

Many communities in the world, especially in rural and underdeveloped regions, still have no access to cellular connectivity. The low return of investment for telecommunication companies prevent the entry of middle and last mile infrastructure, consisting of relatively expensive equipment, in these places. Although advances in software-defined radio technology have lowered operation costs of installing Base Transceiver Stations (BTSs), access to appropriate spectrum resources still hinders the deployment and sustainable operation of these technologies in these settings. In a scenario where both licensed and unlicensed networks are allowed to co-exist and share spectrum resources, the unlicensed network must proactively detect transmissions from other networks to avoid interfering with incumbent GSM networks (primary user or PU) while maintaining radio link between base stations and mobiles. In this paper, we present a dynamic spectrum access (DSA) protocol for secondary networks operating in the GSM-900 band. In the proposed DSA protocol, the secondary BTS distributes frequency lists over active mobiles for sensing, on top of energy detection by the BTS for detecting PUs in the current channel it considers to use. Using IEEE 802.22 requirements for Wireless Regional Access Networks, we show that for a false alarm rate of 10%, beacon transmissions as low as -95 dBm over 30 frequency channels can be scanned every 960 ms with 90% detection probability using uplink measurement reports transmitted through the Slow Associated Control Channel. Under same sensing requirements, we show that downlink GSM signals as low as -80.1 dBm can be detected using BTS-side energy detection. The sensing performance of the DSA protocol helps assure licensed networks of non-interference while enabling unlicensed networks to provide basic cellular communications in unserved and underserved communities.