Cooperative and Delay Minimization Routing Schemes for Dense UnderwaterWireless Sensor Networks

Abstract

Symmetry in nodes operation in underwater wireless sensor networks (WSNs) is crucial sothat nodes consume their energy in a balanced fashion. This prevents rapid death of nodes close towater surface and enhances network life span. Symmetry can be achieved by minimizing delay andensuring reliable packets delivery to sea surface. It is because delay minimization and reliability arevery important in underwaterWSNs. Particularly, in dense underworks, packets reliability is of seriousconcernwhen a large number of nodes advance packets. The packets collide and are lost. This inefficientlyconsumes energy and introduces extra delay as the lost packets are usually retransmitted. This is furtherworsened by adaptation of long routes by packets as the network size grows, as this increases the collisionprobability of packets. To cope with these issues, two routing schemes are designed for dense underwaterWSNs in this paper: delay minimization routing (DMR) and cooperative delay minimization routing(CoDMR). In the DMR scheme, the entire network is divided into four equal regions. The minor sinknodes are placed at center of each region, one in each of the four regions. Unlike the conventionalapproach, the placement of minor sink nodes in the network involves timer based operation and isindependent of the geographical knowledge of the position of every minor sink. All nodes havingphysical distance from sink lower than the communication range are able to broadcast packets directlyto the minor sink nodes, otherwise multi-hopping is used. Placement of the minor sinks in the fourregions of the network avoids packets delivery to water surface through long distancemulti-hopping,which minimizes delay and balances energy utilization. However, DMR is vulnerable to informationreliability due to single path routing. For reliability, CoDMR scheme is designed that adds reliabilityto DMR using cooperative routing. In CoDMR, a node having physical distance from the sink greaterthan its communication range, sends the information packets by utilizing cooperation with a singlerelay node. The destination and the relay nodes are chosen by considering the lowest physical distancewith respect to the desired minor sink node. The received packets at the destination node are merged byfixed ratio combining as a diversity technique. The physical distance computation is independent of thegeographical knowledge of nodes, unlike the geographical routing protocols. This makes the proposedschemes computationally efficient. Simulation shows that DMR and CoDMR algorithms outperformthe counterpart algorithms in terms of total energy cost, energy balancing, packet delivery ratio (PDR),latency, energy left in the battery and nodes depleted of battery power.