Received: 28 February 2018 Revised: 6 April 2018 Accepted: 31 May 2018 DOI: 10.1002/cpe.4772 SPECIAL ISSUE PAPER Position adjustment–based location error–resilient geo-opportunistic routing for void hole avoidance in underwater sensor networks Mehreen Shah 1 Zahid Wadud 2 Arshad Sher 3 Mahmood Ashraf 4 Zahoor Ali Khan 5 Nadeem Javaid 3 1 The University of Lahore, Islamabad 44000, Pakistan 2 University of Engineering and Technology Peshawar, Peshawar 25000, Pakistan 3 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan 4 Federal Urdu University of Arts, Science and Technology, Islamabad 44000, Pakistan 5 CIS, Higher Colleges of Technology, Fujairah Campus, Fujairah 4114, UAE Correspondence Nadeem Javaid, COMSATS Institute of Information Technology, Islamabad 44000, Pakistan. Email: nadeemjavaidqau@gmail.com Summary This paper presents four routing protocols for Underwater Sensor Networks (USNs): Location Error–resilientTransmission Range adjustment–based protocol (LETR), Mobile Sink–based GEo- graphic and Opportunistic Routing (MSGER), Mobile Sink–based LETR (MSLETR), and Modified MSLETR (MMS-LETR). LETR considers transmission range levels for finding neighbor nodes. If a node fails to find any neighbor node within its defined maximum transmission range level, it recov- ers from communication void regions using depth adjustment technology. MSGER and MSLETR avoid depth and transmission range adjustment and overcome the problem of communication void regions using MSs, whereas MMS-LETR takes into account noise attenuation at various depth levels, elimination of retransmissions using multi-path communication and load balanc- ing. The performance of our proposed protocols is evaluated through simulations using different parameters. The simulation results show that MSS-LETR supersedes all counterpart schemes in terms of packet loss ratio. LETR significantly improves network performance in terms of energy consumption, packet loss ratio, fraction of void nodes, and the total amount of depth adjustment. KEYWORDS depth adjustment, geographic routing, mobile sink, transmission range levels, underwater sensor networks 1 INTRODUCTION Underwater Sensor Networks (USNs) recently came up with hundreds of applications like harbor monitoring, oceanographic data collection, seaquakes monitoring, submarine tracking, etc. 1 In traditional USNs, a number of tethered sensor nodes are dropped in the targeted network area for monitoring. However, the inherent challenges like high bit error rate, limited bandwidth, and large end-to-end delay have very bad impact on deployment and in design of USNs. Nevertheless, high end-to-end delay is observed in USNs due to speed of sound in water, ie, 1500 m/s. 1 the acous- tic signals are the most preferred way of communication in acoustic environment because radio waves get absorbed in water due to high-frequency ranges, whereas optical waves are applicable only to short-range transmissions and face heavy scattering. Besides sensing, many senor nodes have the capability to locate themselves using positioning system. Global positioning systems provide an expensive and power consuming solution to the localization problem. Therefore, local positioning system is the most feasible and cost-effective tech- nique for localization underwater. However, erroneous nature of local positioning system effects communication between network nodes. Besides localization errors, one of the major challenges is the efficient utilization of limited node battery, which directly affects the network performance. Further, it is quite difficult to replace sensor node's battery in harsh aquatic environment. Thus, need of efficient and reliable routing mechanism emerges, which can ensure error-resilient and energy-efficient communication between sensor nodes. Geographic routing is considered as the most promising data transmission technique to address the key USN's issues because it is simple and scalable. 2 Moreover, complete route establishment and maintenance toward sink is not required, whereas locally optimal routes are selected at each hop until the packet reaches its destination. Geo-opportunistic routing adds more benefits for data transmission in terms of high packet delivery Concurrency Computat Pract Exper. 2018;e4772. wileyonlinelibrary.com/journal/cpe © 2018 John Wiley & Sons, Ltd. 1 of 18 https://doi.org/10.1002/cpe.4772