# A Survey on an Energy-Efficient and Energy-Balanced Routing Protocol for Wireless Sensor Networks
## 2 Related Work
The authors in [39] classified clustering routing protocols based on their objectives, and methods of cluster head selection, cluster formation, data aggregation and data communication. They provided a taxonomy to the protocols in each of these phases. The authors also discussed the strengths and weaknesses of the techniques used in the studied clustering routing protocols. Finally, the authors summarised the issues and solutions of the attributes and characteristics of clustering approaches. In [15], the author presented the advantages and applications of clustering techniques in WSNs. In this regard, the author introduced a taxonomy to classify clustering routing protocols for WSNs. The author compared these clustering routing protocols based on different measures such as scalability, energy efficiency, cluster stability, and load balancing. On the contrary, we focus more on energy-efficient and energy-balanced routing protocols for WSNs. Interestingly, clustering techniques are extensively used to optimize energy consumption in WSNs. Thus, we review the clustering routing protocols that focus on optimizing the energy consumption in WSNs, and classified these clustering algorithms based on their mode of communication towards the BS. Our survey includes both homogeneous and heterogeneous energy-efficient and energy-balanced clustering routing protocols for WSNs. Additionally, we grouped these clustering routing algorithms, based on the cluster size formulation, into unequal and equal clustering routing algorithms. Survey on multipath routing protocols for WSNs is presented in [16; 17; 18; 19]. The authors in [16] explain the notion and challenges of multipath routing protocols for WSNs. They presented a taxonomy to classify the surveyed multipath routing protocols and provided the strengths and weaknesses of these surveyed multipath routing protocols. The authors [16] also provided a comparison to summarise these multipath routing protocols based on their network applications. In [17], the authors provided a survey on multipath routing protocols for WSNs. Afterwards, the authors classified these multipath routing protocols into three categories (infrastructure-based, non-infrastructure-based, and coding-based) and compared these multipath routing protocols based on these categories. The authors finally explained the evaluation metric, objectives, and challenges in designing multipath routing protocols for WSNs. The authors in [18] investigated the advantages of different multipath routing protocols and classified these surveyed multipath routing protocols based on their features. The survey in [19] compares different multipath routing protocols for WMSNs based on their working operations and provided the advantages and disadvantages of these multipath routing protocols. In contrast to the survey in [16; 17; 18; 19], this paper pays attention to multipath routing protocols designed mainly to optimize energy consumption in WSNs. We review the multipath routing protocols developed to optimize energy consumption in WSNs. Accordingly, we classified these multipath routing protocols based on the solution types or algorithms, and the design decision variables used in the algorithms. We therefore summarise the related survey work on WSNs in Table 1. The table provides the major relevance and contribution of each related survey work and the year of the survey. These surveys provide good insight into the applications, challenges and implementations of WSNs. Although some of the survey papers focus on energy-efficient routing protocols for WSNs, we provide a systematic survey on both energy-efficient routing protocols and load-balanced energy routing protocols. Moreover, we emphasised the importance and challenges of developing a load-balanced energy routing protocol. We discussed the pros and cons of the reviewed energy-efficient routing protocols and load-balanced energy routing protocols for WSNs.