# Multi-Hop Routing Protocols for Oil Pipeline Leak Detection Systems
## 2 Related Work
### Related Leuk Detection Systems  
Over the last years, researchers have proposed pipeline leak detection systems based on WSNs. The systems use different types of sensors to monitor the different types of pipelines. Additionally, they use diverse communication technologies such as ZigBee and Bluetooth. In this part, we highlight some of these leak detection systems to define the main specifications of these systems such as the type of sensors they used, WSN technology, and the type of communication being they applied.  
In [25], the Steamflood and Waterflood Pipeline Monitoring System (SWATS) design is presented. The system detects leakage in aboveground pipelines. It provides good coverage but consumes energy. The system uses temperature and pressure sensors. A different system for underwater applications was proposed in [26]. The channel-aware routing protocol (CARP) enhances the link quality by using the link state as one of the parameters to select the route. This system can be used in underwater oil pipes and monitoring pollution in the sea. CARP uses multi-hop routing.  
A hierarchical network was proposed as a solution with single-hop communication as in [27; 28] and with multi-hop communication [29; 30]. In [27], a hierarchical representation of LSN was proposed. Dividing the networks into layers, first, they have the Basic Sensor Node (BSN), then the Relay Node (RN), Data Dissemination Node (DDN), and finally Network Control Center (NCC). Each layer uses different wireless standards, the first one uses Zigbee, and Bluetooth and the layer after that used caller technology. An improved scheme was designed, along with a routing protocol and an addressing scheme considering the Zigbee standard [27]. In this work, they used different standards at each layer. That can be used in our pipeline system. The author in [28] introduced monitoring systems for underground water pipelines (PIPENET) using Bluetooth considering a hierarchical topology with different standards that are different from the ones used in the previous work. The disadvantages are high delay and energy consumption, as well as low reliability. Another system that is described in [29] is magnetic induction-based wireless sensor networks. This study addressed the requirements of an underground pipeline monitoring (MISE-PIPE) system using a hierarchical, cluster-based system including pressure, acoustic, and temperature sensors. Additionally, the work in [31] presented a Sensor-based PipelineAutonomous Monitoring and Maintenance System (SPAMMS) for monitoring an above-ground water pipe using a heterogeneous network (the network has three devices basic sensors, mobile sensors, and robot agent). SPAMMS requires a large amount of energy. Furthermore, the authors in [32] present an oil and gas leakage detection system, called Reliable Monitoring of Oil and Gas Pipelines using Wireless Sensor Network (REMONG), which was designed for above-ground pipes. It uses two types of sensors for temperature and pressure. It uses Zigbee technology and AODV routing protocol. The limitations are low scalability and the network lifetime, and the fact that when the density of the network increases it consumes high energy. Table 2 shows detailed specifications of these systems.