Networked RFID Systems for the Internet of Things

The Internet of Things (IoT) utilizes trillions of uniquely identifiable smart objects to connect anything at anytime and anywhere. Radio frequency identification (RFID) techniques are a powerful promising enabler for realizing the IoT. Around how to build hierarchical networked RFID systems for the IoT, this dissertation formulates and addresses problems in three key areas, i.e., communication protocols, simulation approaches, and RFID applications. Communication protocols are essential for designing high-performance networked RFID systems. First, we propose to use time hopping pulse-position modulation (TH-PPM) impulse radio ultra wideband (IR-UWB) for the tag-to-reader link. We analyze different parts of the system delay and propose relevant strategies to shorten the delay. Second, we give the concept of code division multiple access (CDMA) UWB RFID systems. We analyze the asynchronous matched filter receiver and decorrelating receiver for multi-tag detection, and propose a new communication process that fully exploits the multiple-access capability of the two detection schemes. Simulations are widely used to evaluate the performance of wireless networks. We propose a new approach for simulating networked RFID systems with multiple wireless standards within one case in OMNeT++. It is realized by partitioning and modeling the protocol stacks of different standards and designing a multi-radio module. Moreover, we propose a CO-Simulation framework with MATLAB and OMNeT++ (COSMO). COSMO has the ability of self-validation. It combines the strengths of MATLAB and OMNeT++ by compiling prebuilt models in MATLAB to header files and shared libraries and integrating them into OMNeT++. RFID technology gains popularity because it can be used to track and monitor objects in real time. We implement two typical networked RFID applications, i.e., wide area RFID sensor network and item-level indoor RFID localization. We design a two-layered wide area RFID sensor network for fresh food tracking. It adopts GSM/GPRS for the communication between the server and master nodes, and semi IR-UWB for the communication between master nodes and slave nodes. We develop the control platform and implement the all-in-one sensor nodes. For indoor RFID localization, we give insights about the influence of tag interaction on tag antenna radiation pattern and localization accuracy. Two examples, i.e., the k-NN algorithm and the Simplex algorithm, are taken to show how to utilize tag interaction analysis to improve the design of localization algorithms.