# A New Resource Allocation Protocol for the Backhaul of Underwater Cellular Wireless Networks
###### Abstract  
In this paper, an underwater base station initiating (UBSI) resource allocation is proposed for underwater cellular wireless networks (UCWNs), which is a new approach to determine the backhaul capacity of underwater base stations (UBSs). This backhaul is a communication link from a UBS to a UBS controller (UBSC). Contrary to conventional resource allocation protocols, a UBS initiates to re-determine its backhaul capacity for itself according to its queue status; it releases a portion of its backhaul capacity in the case of experiencing resource under-utilization, and also requests additional backhaul capacity to the UBSC if packet drops are caused due to queue-overflow. This protocol can be appropriate and efficient to the underwater backhaul link where the transmission rate is quite low and the latency is unneglectable. In order to investigate the applicability of the UBSI resource allocation protocol to the UCWN, its performance is extensively analyzed via system level simulations. In our analysis, considered performance measures include average packet drop rate, average resource utilization, average message overhead, and the reserved capacity of the UBSC. In particular, the simulation results show that our proposed protocol not only utilizes most of the given backhaul capacity (more than 90 percent of resource utilization on the average), but also reduces controlling message overheads induced by resource allocation (less than 2 controlling messages on the average). It is expected that the simulation results and analysis in this paper can be used as operating guidelines to apply our new resource allocation protocol for the UCWN. s 2018 8 178 201  
An underwater sensor network is a representative underwater wireless network, where multiple sensor nodes form a cluster. The data from a sensor node in one cluster is transmitted to that in another cluster by exchanging data between cluster heads. An underwater sensor network is advantageous due to its simplicity to build a network infrastructure, application versatility, and network expandability. However, this network type may suffer from severe latency, packet loss, and resource under-utilization induced by the bottleneck (e.g., due to heavily loaded traffic) occurred at a cluster head [7]. Moreover, message overhead can increase due to transferring routing messages among cluster heads and frequent re-routing owing to the mobility of nodes [8]. In order to reliably operate underwater applications and to overcome the weakness of an underwater sensor network, an underwater cellular wireless network (UCWN) was considered in the previous studies [8; 9]. In a UCWN, an underwater base station (UBS) located at the center of a cell controls underwater terminals (UTs) residing in its cell, which is very similar to a terrestrial cellular wireless network (TCWN) [10]. In one underwater cell, a UBS collects data from all the UTs, and forwards the data to a UBS controller (UBSC) which is located on the water surface and controls multiple underwater base station (UBSs). A UBSC can be fixed (like a buoy) or mobile (like a command ship) dependent upon applications. The communication link between a UBS and a UBSC is important because it is responsible for exchanging both control signaling and data traffic. This link is very similar to the backhaul link between a base station and a base station controller in a TCWN. Thus, it can also be regarded as a backhaul link between a UBS and a UBSC. A UCWN can improve performance in terms of latency by avoiding multi-hop communications, thus enhancing network efficiency [11]. Furthermore, a UCWN may increase the communication reliability in harsh underwater environments where frequent transmission failure due to high bit error rate (BER) occurs and network traffic is heavily loaded caused by the advance of underwater applications [11; 12]. Previously, several studies for a UCWN have been done since the introduction of the concept of a UCWN in literature [8; 9; 10].