On exploiting white spaces in WiFi networks for opportunistic M2M communications

Machine to machine (M2M) communications are expected to form one of the fundamental building blocks of the future Internet of Things (IoT). In view of the scarcity of spectrum and the service requirements of traditional users, providing network access to the extremely large number of devices in IoT and M2M scenarios is one of the fundamental problems for network designers and operators. As a possible solution to this issue, this paper explores the possibility of using the unlicensed industrial, scientific and medical (ISM) band for supporting M2M communications while co-existing with traditional users of this band. Since IEEE 802.11 or WiFi based networks are the most common networking technology in the ISM band, this paper presents an evaluation of “white spaces” in WiFi networks (i.e. periods where the WiFi network is not using the channel) that may be used opportunistically for M2M communications. Using a MMPP/G/1/K queue to model the operation of a WiFi access point, we characterize the WiFi white spaces in terms of their frequency, duration, and their probability distribution. Our results show that WiFi white spaces provide considerable transmission opportunities that may be exploited for M2M communications.