“…EC-based improved GRs have been developed for many specific sensor networks in recent years [27,28,29,30,31]. However, we only reviewed studies that are relevant to our proposed work, that is, those that address energy efficiency [31,32,33,34,35,36], load balancing [37,38,39], and spatial query issues [40,41,42,43]. We organized this review by discussing energy-efficiency and load-balancing EC algorithms, followed by several spatial query efficiency GR issues.…”