# A New Resource Allocation Protocol for the Backhaul of Underwater Cellular Wireless Networks
## Average resource utilization
#### 4.2.3 Simulation Summary  
In this section, we provide a summary of our SLS results and analysis, and an operational guideline for the backhaul resource allocation in the UCWN using proposed protocol. In our SLSs, we assumed that the total backhaul capacity of the UBSC is equal to 100 and the number of UBSs connected to the UBSC is 10. So, if the average packet arrival rate \(\lambda>10\), then it would be natural that most of the UBSs suffer the shortage of the backhaul capacity. Consequently, this results in high average packet drop rate, almost peak value (i.e., nearly equal to one) for average resource utilization, and almost lowest value (i.e., approximately zero) for average reserved capacity of the UBSC. We can find this phenomenon from the graphs in Sections 4.2.1 and 4.2.2. Therefore, in order to obtain operational guideline for the backhaul of the UCWN, we need to focus on the performance for \(\lambda\leq 10\) in the SLS results. SLS results and operational guideline for Scenario 1 can be summarized as follows. * Average packet drop rate is not dependent upon under-utilization limit (\(\rho_{LIM}\)), but more dependent upon the number of mobile UTs (\(N_{MN}\)) generating burst traffic and upon the average packet arrival rate \(\lambda\). * There is a close relationship (or a tradeoff) among the average resource utilization, the average message overhead, and the average reserved capacity of the UBSC for \(\lambda\leq 7\). Specifically, as \(\rho_{LIM}\) becomes higher, the average resource utilization becomes higher, the average message overhead also gets higher, and the reserved capacity of the UBSC also becomes higher. * This means that as \(\rho_{LIM}\) becomes higher, each UBS uses only required backhaul capacity and returns unused backhaul capacity to the UBSC. Accordingly, the reserved capacity of the UBSC becomes higher. However, to maintain only required backhaul capacity in each UBS, each UBS needs to send and receive the control signaling messages, which results in high average message overhead. Figure 14: Average Reserved Capacity of the UBSC for different \(\mu_{UBSmax}\) adjustment parameter (\(\beta\)) and the number of mobile UTs (\(N_{MN}\)). * Note that high reserved backhaul capacity in the UBSC can be helpful to cope with burst traffic with high packet arrival rate in some UBSs (mainly caused by the mobile terminals such as AUVs). SLS results and operational guideline for Scenario 2 can be summarized as follows. * Average packet drop rate increases as the \(\mu_{UBSmax}\) adjustment parameter (\(\beta\)) increases. Average packet drop rate becomes higher as the average packet arrival rate \(\lambda\) and the number of mobile UTs (\(N_{MN}\)) increases. * For \(\lambda\leq 7\) and the number of mobile UTs (\(N_{MN}\)) is equal to one, the average packet drop rate is almost the same as \(\beta\) and \(\lambda\) increase. This is because UBSs have sufficient backhaul capacities to support low packet arrival rate. * For \(\lambda\leq 7\), there is a close relationship (or a tradeoff) among the average resource utilization, the average message overhead, and the average reserved capacity of the UBSC. Specifically, as \(\beta\) becomes higher, the average resource utilization becomes lower, the average message overhead also gets higher, and the reserved capacity of the UBSC also becomes lower. * This means that as \(\beta\) becomes higher, a UBS can have higher the maximum backhaul capacity given by \(\frac{\mu_{UBSC}}{N}+\beta\). So, in this case, some UBSs can have larger backhaul capacity than \(\frac{\mu_{UBSC}}{N}\) (equal to 10 in the SLS) and the capacity may not be fully utilized due to small \(\lambda\), resulting in low resource utilization. Besides, when some UBSs have larger backhaul capacity than \(\frac{\mu_{UBSC}}{N}\) due to \(\beta>0\), the other UBSs will have lower capacity than \(\frac{\mu_{UBSC}}{N}\) since the total backhaul capacity is limited. Consequently, the reserved capacity of the UBSC becomes lower for larger \(\beta\).