A comprehensive survey on trajectory schemes for data collection using mobile elements in WSNs

Mobile elements trajectory optimization is one of the most important and efficient ways to enhance the performance of wireless sensor networks (WSNs). In the last 15 years, extensive research has been done in this area, but less effort has been devoted to providing a concise review of the broader area. This article surveys the role of mobile elements trajectory optimization in the performance improvement of WSNs. The complete survey has been done based on three major aspects: applications, trajectory techniques and domains used to formulate the trajectory. Under these three aspects, large numbers of schemes are discussed, along with their sub-aspects. A comparative analysis using eight important parameters, like trajectory pattern, number of mobile elements, speed, mobile element type, etc., is presented in a chronological fashion. The paper also points out the merits and demerits of each scheme described. Based on the current research, we have identified some research domains in this area that need more attention and further exploration.