Energy efficiency is one of the main challenges of Machine-to-Machine (M2M) networks, since they aim at connecting devices with limited access to power sources and operate without human intervention. It has been shown in the past that the use of short-range cooperation between wireless devices equipped with multiple Radio Access Technologies (RATs) can achieve energy savings and extend the lifetime of cellular wireless networks. Devices with cellular connectivity can become temporary gateways to provide energy-constrained devices within the short-range cluster with access to the long range cellular infrastructure. To this end, the devices need to discover their neighbours using their short-range radio interface to identify and select potential gateway candidates. Existing neighbour discovery mechanisms perform poorly in terms of delay and energy consumption to maintain, continuously at each device, complete neighbourhood information, and thus may not be suitable for energy-constrained M2M networks. In this paper, we focus on distributed neighbour discovery mechanisms that are initiated dynamically and spontaneously by a single device to discover only its single-hop neighbours. We formulate accurate delay and energy models of three discovery mechanisms based on frame slotted-ALOHA and contention tree algorithms, and compare their performance in terms of delay and energy consumption.

Peer Reviewed