Energy-efficient spectram access for ultra low power sensor networks

This paper investigates a dynamic spectrum access (DSA) scheme for ultra low power sensor networks (ULPSN) in an open spectrum where multiple systems coexist and interfere with each other. Low transmission power and simple communication protocol are significant obstacles for ULPSN to operate in the open spectrum. The DSA has been researched to solve this problem by assuming that coexisting systems can perfectly detect each other. However, this assumption is limited for ULPSN because detection of ULPSN in coexisting system is difficult due to sensitivity limitation of spectrum sensing. As a result, available spectrum is more scarce for ULP system than other coexisting systems. Thus, we derive a new Markov chain model of open spectrum access. Based on the Markov chain mode, we design a DSA scheme to maximize the energy efficiency and investigate the channel access and switch policy of the proposed DSA within the framework of partially observable Markov decision process (POMDP). The simulation results demonstrate that the proposed DSA scheme yields improved energy efficiency and lifetime compared to a random channel selection for ULPSN.