# An Enhanced Energy Balanced Data Transmission Protocol for Underwater Acoustic Sensor Networks  
[PERSON] 1,*  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 2  
2 Allama Iqbal Open University, Islamabad 44000, Pakistan; [EMAIL_ADDRESS]  
[PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 3  
3 King Saud University, Riyadh 11451, Saudi Arabia; [EMAIL_ADDRESS]  
[PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 3  
3 King Saud University, Riyadh 11451, Saudi Arabia; [EMAIL_ADDRESS]  
[PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 3  
3 King Saud University, Riyadh 11451, Saudi Arabia; [EMAIL_ADDRESS]  
[PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 3  
3 King Saud University, Riyadh 11451, Saudi Arabia; [EMAIL_ADDRESS]  
[PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; [EMAIL_ADDRESS] (A.A.); [EMAIL_ADDRESS] (M.L.K.) [PERSON] 1  
1 COMSATS Institute of Information Technology, Islamabad 44000, Pakistan; ashfaqcomsats@gmail. In UASNs, acoustic communication is preferred over radio communication because underwater environment hinders radio waves communication. The unique features of underwater environment do not allow the algorithms used in WSNs to be applied directly in UASNs. An acoustic modem's energy consumption is quite different from typical radio transceiver [3]. Thus, either novel routing mechanisms or tailored ones are needed for UASNs that take into account the challenges of aquatic environment, and with the objective of network lifetime prolongation. In this regard, many routing protocols are proposed for UASNs [4; 5; 6; 7; 8]. Though these works increase the network lifetime, however, not to the extent that is needed. Sensor nodes use one of the three ways to transmit data: direct, multi-hop and hybrid. In the first technique, nodes far away from sink die earlier due to high transmit power needed at longer distance. The second technique exhausts sensor nodes nearer to the sink due to more data transmission burden. The third one combines both direct and multi-hop transmission modes to somehow balance the load. Several existing works like [3; 9; 10] address energy balancing in both small and large-scale UASNs by exploiting the hybrid data transmission technique. Both [9; 10] balance energy consumption in small-scale UASNs, however, their performance is worst in large-scale UASNs due to distant communication. Similarly, the protocols proposed in [3] are mainly designed for linear networks and perform well only under sparse network conditions. Though the authors in [5; 6; 9], and [11] have contributed towards network lifetime prolongation (refer to Table 1), performance of these protocols degrades (in terms of lifetime, throughput and path loss) as the number of nodes are increased or the network area is increased. BTM's performance degrades as the network area is increased because it is based on the direct communication mode. The transmit energy (in UASNs) is 100 times more expensive than receiving energy [12; 13] which means that balanced use of the transmit energy among sensor nodes contributes to longer network functioning time as well as high throughput.