Load-aware Reader Placement Algorithms for RFID Networks

Radio Frequency Identification (RFID) technology has been used in a wide variety of tracking, monitoring, and access control applications. The spreading adoption of RFID and its large scale deployments have given importance to some planning and coverage problems in this field. Tags coverage in RFID networks is one of these problems that can be defined generally as finding the number and locations of RFID readers needed to identify a set of RFID tags in a particular area. Accurate coverage is crucial in RFID systems as failing to cover a tag may result in missing an important event and/or losing asset and revenue. Furthermore, several technical issues, such as balancing the load among readers and avoiding tags/readers interference, make this placement problem challenging and different from other classical placement problems. In this paper, we look into the problem of placing RFID readers to cover a set of RFID tags with the objectives of minimizing the number of readers, reducing overlapping among readers interrogation ranges, and balancing the load among readers. We propose an approximation algorithm for the problem of covering all tags using the minimum number of readers. We then extend this algorithm to add the objective of reducing overlapping and interference among the coverage areas of readers. We finally present two load balancing algorithms that evenly distribute the tags identification load among different readers. The first load balancing algorithm assumes a fixed interrogation range for the RFID reader and the second one assumes a dynamic interrogation range. We also present our RFID planning tool which is a software that implements our algorithms to produce detailed plans for RFID networks. And finally, we present comprehensive simulations to study the performance of our algorithms.