# Self-Organizing and Scalable Routing Protocol (SOSRP) for Underwater Acoustic Sensor Networks
## 1 Introduction
The author proposes a centralized model, providing a mechanism for scheduling and data transmission processing. The protocol enhances the energy efficiency and network throughput through power monitoring solutions. In BEEC [6] routing protocol, a circular field is divided into ten sub regions and each region is further divided into eight sectors. The data is collected from the sectors using two mobile sinks, moving in circular patterns where each covers five different sectors in sequence. The protocol increases the performance of network in term of lifetime, energy consumption, throughput and stability. However, the sink nodes follow a fixed circular pattern which leads to packet loss and higher delay because of unawareness of network conditions. Additionally, to collect the data from sensor nodes, Autonomous Underwater Vehicles (AUV) are used to move the sink which requires extra resources to operate the AUVs. A routing algorithm has been proposed through remodeling the Vector-Based Forwarding (VBF) protocol in Reference [7]. It considers the routing pipe radius as a function of node range, number of nodes and dimension of environment. The selection of guiding node is based on the residual energy of the receiving node, increasing or reducing the radius of pipe. The results indicate that the protocol decreases the energy consumption in the network with large number of nodes by changing the routing pipe's width in proportion to network density. In Reference [8], the proposed protocol routes the data based on its priority. The nodes are deployed in a cube considering the underwater scenario. The algorithm distinguishes the data based on two traffic classes: high priority and low priority. For traffic with high priority, the forwarder node is selected based on the minimum distance to the BS and residual energy present in the target cube. This improves the performance in terms of energy, end-to-end delay and packet loss. In Reference [9], the proposed protocol combines a Depth Based Routing (DBR) protocol with clustering approach to minimize the energy consumption and distribute the load among the nodes in the network. The classification of nodes (normal, CH and dead) in the network is performed based on the assignment of a random number between 0 and 1. In the CH detection phase, if the residual energy of the CH is less than threshold, it will be eliminated as CH and a new CH is formed. The approach has improved the energy efficiency through implementingclustering in depth-based routing. In Reference [10], Energy Efficient DBR (EEDBR) is compared with simple DBR and a hop-by-hop dynamic address based (H2-DAB) protocol. The protocol selects the next node based on lowest depth and highest residual energy from the neighboring nodes. The results show that both path loss and packet delivery ratio are almost same for DBR and EEDBR whereas H2-DAB has a higher end-to-end delay. The protocol proposed in this work is oriented to the network layer, so it is assumed that a free collision Medium Access Control (MAC) protocol has been previously implemented. There are many techniques applicable for UASNs [11; 12; 13; 14], being TDMA [15; 16] one of the most bandwidth efficient. The proposed protocol achieves stability as the network size increases, providing efficient paths to the sink node and fault tolerance through self-organizing the nodes in the network. In comparison to Reference [2], SOSRP follows a decentralized mechanism where failure of a single node does not disturb the communications within the network. However, in a clustering approach, the failure of a master node disconnects an entire cluster from the network. SOSRP is a hop-to-hop based communication protocol where nodes relay messages to the sink, whereas in Reference [6] Autonomous Underwater Vehicles (AUV) are required as mobile sinks to collect the data from the deployed nodes. Therefore, extra resources to control the AUVs are needed. In Reference [5], a hop-to-hop based power efficient protocol is proposed.