# Multi-Hop Routing Protocols for Oil Pipeline Leak Detection Systems
## 3 System Architecture, Scenarios of Multi-Hop LoRa, and Results  
In our envisaged system for monitoring the oil transport infrastructures, the pipeline is considered to run through the desert where wired connections and power supplies are not usually available. The pipeline length is up to 1200 km. Furthermore, 266 km of the pipeline run through the desert where there are no cities around [3]. In this research, the system is designed supposed to use a WSN consisting of two types of sensors: temperature and pressure sensors, both battery-powered. The sensors send the measurements to the gateway (GW) in a multi-hop fashion. The GW needs a power source, so it is under consideration for placement in the nearest town. The data are sent from the GWs to the control center where they are analyzed to detect leakages. LoRaWAN multi-hop technology will be considered, assuming a bandwidth of 125 kHz.  
Three different scenarios are tested to build and evaluate our model. The first scenario is the simplest multi-hop formation, according to which the source node sends the packet to its neighbor (and then on each node to its immediate neighbor) until reaching the GW. The node only connects to the previous and next neighbors. This type of communication is easy to develop. In this scenario, all nodes will be involved in the communication. In the second scenario, not all nodes cooperate in the communication. Each node will send packets to the third neighbor. In the last scenario, the node will transmit packets to its ninth neighbor. Both scenarios 2 and 3 increase the time of sleep state for network nodes. Figure 1 shows the three scenarios. In each scenario, we estimate network capacity and coverage planning and calculate the energy consumed when receiving and sending packets of various sizes towards the gateway. In LoRa technology, sending the packets to a specific neighbor node is done in two ways, either by broadcasting using address 0 or using the neighbor node's address [47]. Since in our scenario the node may send the packets to its second or third neighbor, the communication in our model is achieved through the node's addresses.  
Furthermore, a comparison between flat and two hierarchical topologies is presented. In flat topologies, the nodes are arranged in a line, and each node connects with its adjacent neighbors (next and previous). The packets are sent from one node to another until they reach the GW. On the other hand, in the first hierarchical topologies, the area is divided into clusters. Each cluster has a cluster head (CH) and three nodes. The communication is done from each node to its CH and then from the CH to the GW through other CHs. In the second hierarchical scenario, each cluster has nine nodes instead of three. The two hierarchical scenarios are shown in Figure 2. As can be seen, in each scenario, nodes are numbered  
Figure 1: Multi-hop communication scenarios.  
sequentially, and cluster heads nodes are labeled with CH and a number representing their order in the sequence of all nodes of the scenario.  
We evaluate our model to validate the network parameters and assumptions. In this section, we show and discuss our results. We compare the consumed energy and number of bytes for different transmission ranges.  
The results will be presented in the following four sections. The first section studies the measurement ranges and the traffic size, whereas the second section focuses on the energy consumption of LoRa devices. The third section examines two different types of sensors, and the last section compares the energy consumption of LoRa devices in a flat and hierarchical topology. All tests focus on flat topology, except the fourth one; it compares flat and hierarchical topologies.