Performance analysis of amplify and forward technique in region based cooperative routing for underwater wireless sensor networks Sheraz Hussain 1 , Nadeem Javaid 1,* , Muhammad 1 , Israr Ahmad 1 , Umar Qasim 2 , Zahoor Ali Khan 3,4 1 COMSATS Institute of Information Technology, Islamabad, 44000, Pakistan 2 University of Alberta, Edmonton, AB, T6G 2J8, Canada 3 Internetworking Program, FE, Dalhousie University, Halifax, NS B3J 4R2, Canada 4 CIS, Higher Colleges of Technology, Fujairah Campus, 4114, UAE * nadeemjavaidqau@gmail.com; www.njavaid.com Abstract—In this paper, we propose a region based cooperative routing protocol (RPCRP). This protocol performs analysis of amplify and forward technique over Rayleigh fading channels. The source node sends the sensed signal to the destination and available relay nodes. At the destination node, bit error rate (BER) is checked on the basis of which, either positive or negative acknowledgement (ACK or NACK) is sent to the source and relay nodes. If the positive feedback is received from the destination node, the relay nodes drop the packet. However, in case of negative feedback, the best relay node amplifies the signal. After the signal is amplified, it is forwarded to the destination node. Moreover, the mobile sinks (MSs) change their position after some time and cover the whole network are also deployed. The nodes that lie within the transmission range of MSs forward their data directly to the sink. Also, the mathematical equations for the total SNR gain and outage probability are verified by simulations. Results show that RBCRP outperforms incremental best ralay technique (IBRT) in terms of throughput and network lifetime. Also, the mathematical analysis for outage probability shows that RBCRP is 62 % more better than IBRT. I. I NTRODUCTION In underwater wireless sensor networks (UWSNs), wireless ad-hoc networks, cellular networks, etc., cooperative commu- nication has gained much attention. In cooperative communi- cation, the sensor nodes act as source, relay and destination. There are two most common relaying methods: amplify and forward (AF) and decode and forward (DF). In the previous method, the relay node amplifies the received signal from source node and forwards it to the destination node. However, the relay node decodes the noisy version of the signal received from the source and then forwards it to the destination node in later technique. [1], [2]. The performance analysis of AF cooperative scheme with the calculation of signal to noise ratio (SNR) and outage probability has been extensively studied in [1]–[3]. But with the relay selection strategy and mobile sinks (MSs) along with analysis of relaying technique to improve the performance of network, there have been very few cooperative routing techniques. In [3] and [4], the exact and closed form for the calculation of SNR and outage probability are derived assuming independent and identical distribution (i.i.d) over Rayleigh fading channels. A. Problem statement Incremental best relay technique IBRT over Rayleigh fading channels is a cooperative routing technique for UWSNs [5]. In this section, we discuss the parameters and flaws not considered in IBRT. 1) Selection of relay node: In IBRT, the SNR of links between source and relay nodes is calculated on the basis of which relay node is selected. The link with the highest SNR is the best link, and the relay node that lie in the qualified link is considered as the best relay node. In this case, there are more chances of having more load of relaying data on the selected relay node. In this way, residual energy of the relay node is sharply reduced and the network life time is degraded. 2) More packet drop: As the underwater environment is noisy and due to the poor quality of link and multi path fading, the chances of packet drop are very high. In IBRT, the cooperative routing is performed to transfer the sensed signal from source node to destination node. But, to deliver the data of nodes deployed at higher depths, towards the sink is very challenging task, because sink is deployed at the surface of the water. So, in this case, the throughput of IBRT is degraded and large number of packets are dropped. 3) Analysis of outage probability and SNR: In IBRT, the expressions for the end to end SNR and outage probability are derived and formulated. In the expression of outage probability in IBRT, the outage probability depends on the number of relay nodes, SNR threshold γ and residual energy of the selected relay node. If the number of relay nodes and γ are kept constant, the outage probability depends on the residual energy of the relay node. As in IBRT, the relay selection criteria is only the SNR of the link. So, if the node with low residual energy is selected as the best relay node then the outage occurs at destination. The chances of packet drop due to poor quality of the link and less remaining energy of the node are shown in Fig.1. 2016 10th International Conference on Innovative Mobile and Internet Services in Ubiquitous Computing 978-1-5090-0984-8/16 $31.00 © 2016 IEEE DOI 10.1109/IMIS.2016.138 33