## 1 Introduction
The typical clustering routings protocols in WSNs include Low-energy Adaptive Clustering Hierarchy (LEACH) [14], Hybrid Energy-Efficient Distributed clustering (HEED) [15], Distributed Weight-based Energy-efficient Hierarchical Clustering protocol (DWEHC) [16], Position-based Aggregator Node Election protocol (PANEL) [17, 18], Two-Level Hierarchy LEACH (TL-LEACH) [19], Unequal Clustering Size (UCS) model [20], Energy Efficient Clustering Scheme (EECS) [21, 22], Energy-Efficient Uneven Clustering (EEUC) algorithm [23], Algorithm for Cluster Establishment (ACE) [24], Base-Station Controlled Dynamic Clustering Protocol (BCDCP) [25], Power-Efficient Gathering in Sensor Information Systems (PEGASIS) [26], Threshold sensitive Energy Efficient sensor Network protocol (TEEN) [27], The Adaptive Threshold sensitive Energy Efficient sensor Network protocol (APTEEN) [28], Two-Tier Data Dissemination (TTDD) [29], Concentric Clustering Scheme (CCS) [30], Hierarchical Geographic Multicast Routing (HGMR) [31], and _etc._ Clustering routing is becoming an active branch of routing technology in WSNs on account of a variety of advantages, such as more scalability, data aggregation/fusion, less load, less energy consumption, more robustness, _etc._  
In the last few years, a relatively large number of clustering routing protocols have been developed for WSNs. This paper is an attempt to comprehensively review and critically discuss the most prominent clustering routing algorithms that have been developed for WSNs. The goals of this survey can be summarized as follows: (1) To make a large audience aware of the existence and of the usually good performance of a number of clustering routing protocols in WSNs; (2) To facilitate the reading as well as to provide a sound framework by a detailed taxonomy of clustering routing algorithms; (3) To highlight a few strengths and weaknesses of the proposed algorithms with respect to the performance of the clustering routing methods in WSNs; (4) To help application designers identify alternative solutions and select appropriate strategies by comparison of different clustering routing approaches. Recently, a few surveys of clustering routing methods for WSNs have been presented. These surveys mainly aim at outlining some characters of clustering and summarizing some popular clustering routing algorithms with comparison based on different attributes and performances. In this study, we present a comprehensive survey of different clustering routing protocols proposed in recent years. Our work differs from other surveys of WSN clustering routing algorithms as follows: (1) As far as we know, this survey is the first attempt to comprehensively review and critically discuss the most prominent clustering routing methods developed for WSNs; (2) It presents a novel taxonomy of clustering methods for WSNs, which is, to the best of our knowledge, the most comprehensive and fine-grained taxonomy of WSN clustering approaches at present; (3) This is the first time that the popular clustering routing protocols are surveyed based on the classification of different algorithm-stages; (4) It summarizes the previous surveys of WSN clustering routing protocols. As far as we know, our work is the first attempt to outline these contributions made by other researchers. The remainder of this paper is organized as follows: Section 2 provides an overview of related work on clustering routing methods in WSNs. Section 3 outlines the advantages and objectives of clustering for WSNs. In Section 4, we present a novel taxonomy of clustering routing algorithms in WSNs. In Section 5, we systematically analyze the prominent WSN clustering routing protocols with discussion on their respective merits and demerits. In Section 6, we compare different approaches for WSN clustering routing. Finally, Section 7 summarizes and concludes this paper.