Power Minimisation Techniques for Space-Based Wireless Sensor Networks

Wireless sensor networks (WSNs) have received much attention in recent years. Such networks comprise spatially distributed sensors to monitor various parameters. Space-based wireless sensor networks (SB-WSNs) consisting of tiny, low power, inexpensive satellites flying in a fleet with a close formation can offer a wide range of applications. Since communication is typically the major factor in power consumption, the activity of the transceiver should be reduced to increase the nodes’ lifetime. To understand the network power behaviour, a space-based wireless sensor network consisting of 40 nodes was designed as an experimental testbed. Several tests were undertaken to investigate the nodes’ lifetime and the packet loss with various sleep/wake up methods. The study found that the nodes with shorter paths to the sink benefit from improvement in their lifetime. In contrast, the other nodes with routes including many hops obtain less enhancement in their lifetime and high packet loss. To further reduce the power consumption, a novel sleep/wake up technique where the nodes have different sleep periods based on their locations has been proposed and tested. This modification enhanced the network operation time by 24% and increased the total delivered packets by 51% compared to when the nodes stay active all their duty cycle. Another concern was uneven power consumption due to the extra packet-relaying duties imposed on central nodes. This was addressed first by altering the connectivity of the network, and then by adding extra nodes dedicated to this task. The proposed sleep/wake up scheme was extended further through the adoption of transmission power control (TPC) and the introduction of multiple sinks. Both mechanisms were used to decrease the power budget required to deliver a packet from source to destination by reducing the number of hops in the paths. This improves the nodes’ lifetime and the total amount of collected data. Findings in this research have direct relevance to the use of commercial off the shelf (COTS) nodes in a SB-WSN and will provide an impetus for accurate estimation of the performance and design of such a network.