VIDEO SENSOR OVER ULTRA-LOW POWER RELAY WIRELESS NETWORKS

Abstract

Ultra-low-power wireless networks have a vast array of potential applications, which are becoming increasingly achievable as technology gets smaller. Before these systems can be used to their full potential, however, efficient methods of data transfer are imperative in order to keep power consumption low while allowing the devices to cooperate as one unit or group. The transfer of large files, such as image data, presents a particular challenge because of the size limits imposed by the 802.15.4 MAC protocol. Operating sensory nodes at larger distances than normal also results in significant data loss. This paper presents a solution to this issue using a modified sensor network that includes nodes dedicated to listening for packet recovery. A set of algorithms is devised in order to allow nodes to detect missing data from a source as well as offer the ability to request that missing data from one of the dedicated relay nodes. The methods described were tested with the iMote2 device and found to almost double the distance at which two nodes can be placed from each other while still maintaining reliable data transfer. It was also concluded that the Linux driver in charge of passing values from the 802.15.4 chip to the MAC layer does not properly pass the Cyclical Redundancy Check (CRC) result into the MAC frame. As a result, it is not possible to filter out corrupt data at the application layer.