## 2 Related Research Work  
Keeping in view the need for a more efficient and robust electric grid, a conceptual framework was proposed by the National Institute of Standards and Technology (NIST) in SGs Interoperability Standards Roadmap [28,29]. According to this conceptual framework, there is a need to have an inter domain and intra domain communication between key building blocks like operations, markets, service providers, generation, transmission, distribution and consumer [28,29]. The NIST framework states that SGs should support the information flow and electrical flow between all key building blocks. Figure 1: Illustration of wireless sensor network (WSN) adopting working–sleeping cycle strategy with opportunistic node connections in neighborhood area network (NAN). blocks. Information flow includes data acquisition, data processing and data dissemination between the desired energy subsystems of SGs, while the electrical flow deals with the generation, transmission and distribution of energy [29]. The main objective of information flow is to monitor and control the energy whereas the electrical flow is responsible for power delivery, demand and asset optimization, etc. [29]. In [30; 31; 32], several key technologies have been identified by the National Energy Technology Laboratory (NETL) for SGs:  
1. Full-duplex and high-speed communication infrastructure for the information exchange between different SG entities. 2. State-of-the-art sensing network infrastructure which will be responsible for the measurement and relaying of physical data. This sensor network can be used to prevent power theft, improve demand response, etc. 3. Fabrication of components related to power electronics, superconductivity and energy storage should be needed based on the contemporary research being conducted for SGs. 4. Seamless and real-time decision making at the prosumer end should be possible by improving the prosumer interface with operations, markets and service providers. The general overview of SGs concept is presented in [11; 12]. The communication architecture and application needs of SGs are explained in detail in [30]. Moreover, the mechanisms for data collection and SGs sensing network is surveyed in [13] and strategies for improving information flows in SGs is mentioned in [33]. Technologies like high speed communication network architecture for SGs have been studied in [30]. Due to the decentralized and lightweight architecture of WSNs, it can be efficiently used in SGs and micro-grids [13]. [PERSON] et al. in [33] presented that WSNs can be used in various SG applications like generation, transmission, distribution and consumption as the WSN can deliver the information needed by the intelligent algorithms running in the control center of SGs. An overview of opportunities and challenges of WSNs in SGs is presented in [34]. Likewise, different researchers have focused on proposing different routing protocols for WSNs based on parameters like network lifetime, delay, bandwidth, packet to delivery ratio and node mobility [23; 24; 25; 26]. As mentioned in a detailed survey for energy efficient and energy balanced routing protocols for a WSN [35], most of these protocols emphasize on improving energy consumption during network transmission activities but very few researches can be found about improvement in energy consumption with node mobility. In a typical WSN topology, all nodes including the sink nodes are static. This leads to a situation in which the adjacent or neighboring nodes of the sink node deplete their limited battery powers as they have to participate in managing more traffic loads for forwarding the sensing data to the sink node as compared to the nodes which are far from the sink node. This typical scenario is known as hot-spot problem and adversely affects the network lifetime in any WSN application [14; 15]. For this particular reason, the node mobility concept is introduced by many researchers, which exploits the movement of the sink node in the WSN to overcome the hot-spot problem [36; 37].