Energy-Aware Algorithm for Assignment of Relays in LP WAN

Abstract

The Low Power Wide Area Networks allow maintaining connectivity with devices over a distance of a few kilometres. However, due to the presence of obstacles the communication range in an urban environment may be shorter, which creates multiple blind spots or areas with limited coverage. The nodes acting as relays may solve this problem by forwarding the data from other devices with poor connectivity. We propose and investigate a novel algorithm that assigns devices to the relay role while keeping the battery constraints. We define the algorithm, describe the simulation testbed, and present performance evaluation in several scenarios, including real-life topologies of IoT networks. The proposed relay selection scheme allows increasing the lifetime of the network by selecting the relay taking into account the current battery capacity. Additionally, it outperforms a previously proposed relay selection algorithm for LP WAN, showing an average 4% decrease in transmission time and an order of magnitude lower computation complexity.

A Nature-Inspired Approach to Energy-Efficient Relay Selection in Low-Power Wide-Area Networks (LPWAN)

“…where E + w is the daily energy surplus (in mA) of the relay candidate w, calculated on the basis of the device's battery level and remaining operation time [20]. The energy budget analysis includes the energy cost of switching to relay mode (1440 mAs).…”

“…The in [ 20 ] presented an algorithm for selecting relays, wherein a single relay is assigned multiple weak nodes; however, such an approach may not be viable in systems where end devices transmit relatively frequently, such as parking, alarm, or security systems. Theoretically, an end device operating on SF = 7 could transmit dozens of times daily for up to ten years (including the duty cycle regulation).…”

“…Each edge is assigned a weight describing the quality of link between devices corresponding to nodes u and w . The formula for determining an edge weight is provided by the heuristic function , where is the daily energy surplus (in mA) of the relay candidate w , calculated on the basis of the device’s battery level and remaining operation time [ 20 ]. The energy budget analysis includes the energy cost of switching to relay mode (1440 mAs).…”

“…This model iteration builds upon the framework presented in a previous investigation [ 36 ], which concentrated on the collision probability derived from radio signal propagation models accessible in OMNeT++. In this study, the simulation model detailed in [ 20 ] is utilized.…”