Multi-layer approach for energy efficient opportunistic routing protocol in underwater sensor networks

Abstract

The Underwater Sensor Networks (USN) are known to be an emerging technology due to numerous applications in aqueous environments. The traditional routing protocols used in terrestrial sensor networks could not be applied for underwater due to the various unique characteristics of USN such as unreliable link, inadequate bandwidth, short life span of battery power, high packet drop rate, and attenuation. Therefore, routing protocols are specifically designed to conform to the characteristics of USN. A multi-layer Opportunistic Routing (OR) approach is an example that offers a promising method to overcome those limitations. Research indicated three critical problems in relation to designing USN: selecting the next reliable energy-efficient forwarding nodes, optimal forwarding path, and communication void. Three protocols were proposed to overcome these problems. First, in dealing with improper high energy consumption and candidate nodes selection problem, an Energy-Efficient Opportunistic Routing (EE-OR) protocol is developed aiming to select the next candidate nodes using depth information and energy metrics. Second, the EE-OR protocol is enhanced aiming to manage the unnecessary forwarding suppression problem using a multi-layer OR approach. The Optimal Path Energy-Efficient Routing (OPEE-OR) protocol is designed to reduce the number of transmissions and control path selection. Third, Energy-Efficient Void Avoidance Opportunistic Routing (EEVA-OR) protocol (a modified version of OPEE-OR) is designed aiming to identify void nodes and avoid these nodes during the process of forwarding data packets. Further, in order to evaluate the performance of the respective developed protocols, several simulations were conducted using AquaSim. Findings were compared to Depth Based Routing (DBR), Energy Efficient Depth Based Routing (EEDBR), Reliable and Energy Efficient Pressure-Based Routing (RE- PBR), Enhanced Void Avoidance Routing (E-VAR), and Void Aware Pressure Routing (VAPR). In addition, findings were also compared in terms of network lifetime, total energy consumption, packet delivery ratio, total number of data packets forwarded, and total number of forwarded void detection packet. Finally, findings also indicated that the EE-OR, OPEE-OR and EEVA-OR protocol performed better regarding network lifetime, total energy consumption (6-24%, 19-32%, 17-32%), packet delivery ratio (3-16.6%, 2-14%, 1.5-13%) and the total number of data packet forwarded (4-18%, 18-31%, 5-28%) respectively. In conclusion, the proposed energy efficient void avoidance opportunistic routing protocol tends to improve energy efficiency and packet delivery ratio; and this leads to the expansion of the corpus of knowledge in the area of underwater sensor networks.