# On Reliable and Efficient Data Gathering Based Routing in Underwater Wireless Sensor Networks
## 2 Related Work  
In source node based retransmission techniques, acknowledgement from the receiver node stops further re transmissions of the same packet. However, the source node is subjected to several retransmissions which makes network unstable. In [6], authors improve the ARQ protocol such that the receiver node asks for retransmission of the same packet from the cooperative nodes. Thus, it leads to network stability which in turn leads to network lifetime prolongation. In [7] Dynamic node cooperation in UWSNs is presented for UWSNs. This mechanism never asks retransmissions from the same node whose data was not-decoded formerly. The receiver asks for a  
Figure 1: Paper hierarchy. retransmission from the node that has overheard the same packet and got better channel conditions. In this protocol the relay nodes are preferred on the basis of link quality and SNR. Similarly [8] uses channel statistical information to select the best relay. It takes into account both the incurred propagation delay and transmission time. The authors also formulated an optimum one way packet transmission (OPT) time. This protocol is biased towards source relay channel as compare to relay destination channel. In [9], authors present a unique cooperating nodes selection norm which is based on propagation delay. This scheme considerably minimizes the amount of required retransmissions among the nodes. Thus, the selection of cooperating node may leads to efficacious energy consumption of the network. Cooperative communication is an energy expensive technique due to retransmissions of same data packet. In [10] sink mobility is introduced to minimize the energy consumption cost of the network. AUV follows an elliptical trajectory and takes sojourn stops after regular intervals. In this way, the communication distance between the nodes and surface sink is minimized which leads to network lifetime prolongation. In [11] EASR protocol has been proposed. It performs sink reallocation for network lifetime prolongation. Sink is triggered for a next shift in its position depending upon the residual energy of some specific region inside the network. Maximum Capacity Path (MCP) is a dynamic routing method that has been adopted to report data from source to sink. Moreover nodes are also considered to be capable of energy aware transmission range control program. \((ACH)^{2}\) a routing scheme for maximizing throughput and network lifetime has been proposed in [12]. It is cluster based scheme whose uniqueness is uniform distributed load over the cluster heads. Cluster head selection is performed in two separate phases; first is the random nodes' selection, followed by the filtering of the candidate nodes on the basis of their residual energies; Secondly, for the sake of well distributed cluster heads their number is optimized by determining their intermediate distances. Moreover nodes receiving better signal strength from central base station communicate directly to it, hence, shorter transmission paths. Co-UWSN proposed in [13] is a routing protocol that combats fading in data transmission process using cooperative communication among nodes. Relay nodes are selected on the basis of the signal strength and distance information. Therefore, significant decrease in path loss consequently, better throughput and enhanced data integrity. [PERSON] and few others have proposed a balance transmission mechanism in [14]. It divides the data routing process into two segments. In the first step, it creates a tree of nodes which is actually a path, a packet follows in data transmission process. This path is created on the basis of optimum transmission distance. On the second stage data routing algorithm is designed. Multihop and single hop both methods of communication are employed to balance the energy consumption. Energy gradation concept is also used in order to decide the transmission mode of nodes. Simulations and results prove the reliability of the protocol in the enhancement of network lifetime.