Data gathering in wireless sensor networks with multiple mobile collectors and SDMA technique sensor networks

In this paper, we consider data gathering in wireless sensor networks (WSNs) by utilizing multiple mobile collectors and spatial-division multiple access (SDMA) technique. In particular, multiple mobile collectors, for convenience, called SenCars in this paper, are deployed in a WSN and work independently and simultaneously to collect data. The sensing field is divided into several non-overlapping regions, each having a SenCar. Each SenCar gathers data from sensors in the region while traversing their transmission ranges. Sensors directly send data to their associated SenCars without relay in order to achieve uniform energy consumption. We also consider exploiting SDMA technique by equipping each SenCar with two antennas. With the support of SDMA, two distinct compatible sensors in the same region can successfully make concurrent data uploading to their associated SenCar. Intuitively, if each SenCar can always simultaneously communicate with two compatible sensors, the data uploading time in each region can be cut into half in the ideal case. We focus on the problem of minimizing maximum data gathering time among different regions, which consists of two parts: the data uploading time of the sensors in this region and the moving time of the associated SenCar on a tour. We refer to this problem as data gathering with multiple mobile collectors and SDMA, or DG-MS for short, and formalize it into an integer linear program. We then propose a region-division and tour-planning algorithm to provide a practically good solution to the problem. Simulation results demonstrate that the proposed scheme significantly outperforms other non-SDMA or single mobile collector schemes by efficiently shortening and balancing the data gathering time among different regions.