Minimum-cost deployment of adjustable readers to provide complete coverage of tags in RFID systems

In Internet of things (IoT), radio frequency identification (RFID) plays an important role to help people rapidly obtain information of objects associated with tags. Passive tags are cheap and require no batteries to operate, so they are widely used in RFID applications. Readers, on the other hand, have to provide power to activate passive tags to get their data. However, collision occurs when two readers send signals to a tag at the same time. Therefore, it is critical to decide the locations of readers, namely reader deployment, to avoid collision. This paper considers adjustable readers, whose transmitted power is configurable to provide different communication range, and proposes a minimum-cost RFID reader deployment (MR2D) problem. Given the positions of tags, it determines how to deploy readers and adjust their transmitted power to cover all tags, such that we can use the minimum number of readers and save their energy. To facilitate data transmission and reduce hardware cost, we restrict the number of tags that each reader can cover and allow readers to have few overlapped tags in their communication range. Then, we develop an efficient solution to the MR2D problem by clustering tags into groups and placing a reader to cover each group to meet the above conditions. Simulation results show that our proposed solution not only saves the number of RFID readers but also reduces their energy consumption, as compared with existing methods.