# A Survey on an Energy-Efficient and Energy-Balanced Routing Protocol for Wireless Sensor Networks
## 2 Related Work
Furthermore, the authors presented the main research development found in literature on these mentioned categories. Conversely, this paper is aimed at providing directions to researchers for optimizing the energy consumption by SNs in a WSN. We review different literature on energy-efficient and energy-balanced routing protocols for WSNs. As such, we classified the surveyed energy-efficient and energy-balanced routing protocols based on their mode of communication towards the BS, the solution types or algorithms, and the design variables used in each of the studied routing algorithms. The authors in [34] provided a comprehensive survey on energy conservation in WSNs. Their survey work concentrates on the energy consumed by the SN hardware components. Firstly the authors broke down the energy consumption for the components of a classic SN and divided the SN into four major components, namely: sensing subsystems, processing subsystem, radio subsystem, and power supply unit. In addition, the authors introduced a systematic and extensive taxonomy through which they classified the energy saving schemes into duty-cycling, data-driven, and mobility-based. The mobility-based energy saving was introduced in [34] as a novel energy saving scheme in order to extend the network lifetime of SNs. They further emphasised the importance of conserving the energy consumed by the SNs component, as in the case of the energy consumed during the network data transmission phase. However, as mentioned earlier in Section 1, the emphasis of this paper is on optimizing the energy consumption by SNs during the network data transmission phase, rather than the energy consumed by SN hardware components. Therefore, our discussion is based on the energy-efficient and energy-balanced routing protocols for WSNs. We classified these surveyed routing protocols and created a possible research direction for researchers and practitioners in this area. A survey on energy-efficient routing protocols for wireless multimedia sensor networks (WMSNs) is provided in [35]. The authors compared the twenty-five surveyed papers based on their performance issues. Additionally, the authors defined the design challenges and limitations of energy-efficient routing protocols for WMSNs. The authors finally classified the surveyed energy-efficient routing protocols based on some metric such as QoS requirement, data delivery model, type of multimedia data, etc. Although the survey in [35] looked at energy-efficient routing protocols, it is only based on routing protocols for WMSNs. In this paper, we concentrate on both energy-efficient and energy-balanced routing protocols and emphasise the importance of a reliable energy-balanced routing protocol. In [36], an exhaustive survey on routing protocols for WSNs developed based on the swarm intelligence approach is provided. An overview of the principles and applications of swarm intelligence-based routing in WSNs is discussed. The authors proposed a new taxonomy for swarm intelligence-based routing protocols in WSNs. Accordingly, they classified the surveyed swarm intelligence routing protocols based on this taxonomy. They explained the challenges with the use of the swarm intelligence technique for routing in WSNs, thereby identifying the future areas of research. On the other hand, we surveyed swarm intelligence-based energy-efficient and energy-balanced routing protocols for WSNs. We classified these swarm intelligence-based energy-efficient and energy-balanced routing protocols in order to provide direction for interested readers. Moreover, we grouped these swarm intelligence-based energy-efficient and energy-balanced routing protocols according to the defined input decision variables used in the algorithm. A comprehensive survey is provided in [4; 37] on energy-efficient routing protocols for WSNs. The paper in [37] provides a survey on energy-efficient routing protocols for WSNs based on the three categories (data-centric, hierarchical and location-based routing) outlined in [32].