Research on Behavior of Two New Random Entity Mobility Models in 3-D Space

Mobile data collectors that can be used without a central control mechanism currently have common use in many fields. Because they do not need a central unit, each node in a network can move independently. The field literature offers various group- or entity-based models to define the functioning of mobile data collectors. In this study, a random entity mobility model (REMM) research was performed. The study was based on the models random walk (RW) and random waypoint (RWP), used in several former studies mentioned in the literature. Furthermore, the models random point (RP) and random journey (RJ) proposed by Bilgin [1] for two-dimensional (2D) space were transferred to three-dimensional (3D–cubic) to be used in the study. Study findings obtained by defining a various number of fixed nodes in areas of various sizes were analyzed using 4 different metrics. It was observed that 4 different metric values decreased for 4 REMMs when the cubic area was enlarged by increasing the edge lengths (150–200–250 pixel) of the cubic. When the cubic’s edge length is 150-200-250 pixel, respectively, connected node ratio (CNR) metric value is 98.04%–95.8%–91.34% for RP and 96.83%-83.23%-70% for RJ. Provided that the cubic area remains constant, the increases in the number of nodes generally tend to increase, although there are slight fluctuations on the results. When the cubic edge is 200 and the node numbers are 4–6–8–10, the message delay is 13.345–16.566–27.386–40.050 seconds for RW and 6.579–9.124–11.431–13.456 seconds for RWP. In the comparisons made by taking the average of the values obtained according to the size of the cubic area and the number of nodes, the RP model reached the highest values for all metrics. For example, the visited node ratio (VNR) metric average for the cubic edge 200 pixels is 98.76% for RP and 94.68%–87.38%–94.78% for RW–RWP–RJ. The VNR metric for the cubic edge 250 is 96.55%–93.7%–87.45%–51.27% for the RP–RW–RWP–RJ. Similarly, the average values obtained for other metrics prove this situation. In addition, when the results of the study are examined, it has been measured that the RP model can deliver the message to the base with less delay than other models. The average delay for the cubic edge 150 is 2.933–27.667–23.236–5.698 second for the RP–RW–RWP–RJ and 2.846–24.337–10.148-4.293 second when the edge is 200. When the average results obtained were examined, the success ranking in the delay metric was RP–RJ–RWP and RW, while the other metrics were formed as RP–RJ–RW–RWP. Considering all the obtained results, it was seen that the proposed two models achieved better results than the existing models in 3D after 2D.