Resumen de Dynamic and scalable strategies to lower the identification time and energy consumption in Aloha-based RFID anti-collision protocols
The fourth industrial revolution is coming, promising to bring together the worlds of production and network connectivity in an Internet of Things (IoT). One capable and feasible technology to build in intelligence to a product is Radio Frequency Identification (RFID) technology. This technology uses a spectrum of radio frequency to transfer the identification information between two communication devices: reader and tags. A remarkable characteristic of this technology is that it does not need a direct line of sight between the reader and the tags to establish communication. In addition, it is a low-intrusive technology, which can be easily adapted to the IoT paradigm. The core application of RFID technology is to read a code stored in the tags’ internal memory, which uniquely identifies them. Thus, tags can be attached to a large number of different items for numerous pplications, highlighting activity recognition, localization systems, tracking, and mobile sensing applications.
The coexistence of several tags in the same identification zone of the reader provides RFID technology with a great flexibility at the expense of the tag collision problem. Tags share the same communication channel (the air) and may respond simultaneously to the same reader command, interfering and garbling their waveforms. The reader then is unable to interpret the information received from the tags, requiring tags to re-transmit their messages. As a result, tags collisions extend the time employed by the reader to identify the tag set and also the energy consumed in the process. Anti-collision protocols are then proposed to arbitrate the tags’ responses, with the main goal of maximizing the number of tags identified by a time unit and minimizing the energy consumed by the reader during the identification process.
Most RFID manufacturers currently follow the EPCglobal Class 1 Generation 2 (EPC C1G2) standard. This standard employs the Slot Counter anticollision protocol, which belongs to the Dynamic Frame Slotted Aloha (DFSA) category. DFSA protocols are characterized by providing tags a set of time slots where tags must randomly choose one time slot to transmit their message. The main challenge that DFSA protocols aim to solve is determining the number of time slots that are contained in one set. The Slot Counter protocol follows a set of recommendations from the current standard to face this challenge, but the exact values of some configuration parameters are not specified. Furthermore, the Slot Counter protocol does not scale efficiently to large tag set sizes, because it presents a smooth behaviour. This lack of definition provides large improvement possibilities in the field of DFSA protocols. Consequently, many DFSA algorithms have recently appeared in the literature to improve the performance of the Slot Counter protocol.
This dissertation provides a solution to the tag collision problem by proposing two dynamic and scalable strategies for DFSA protocols: fuzzy logic and tag estimation. These two strategies are then applied to a traditional DFSA protocol based on the current standard, resulting in four novel anticollision protocols. The proposed protocols improve the performance of existing DFSA protocols, including the Slot Counter, in terms of the tags identification time and the energy efficiency in passive RFID systems. Finally, a physical RFID experimentation system is presented to implement and evaluate user-configurable DFSA protocols based on EPC C1G2.
