Research On Tag Anti-collision Algorithms Of UHF RFID System

RFID(Radio Frequency Identification, RFID) uses radio frequency signals with electromagnetic coupling technology to achieve non-contact automatic identification. RFID can work in harsh environments without human intervention, RFID can also identify fast moving objects, read multiple targets from remote distance. Now, RFID is widely used in industrial automation,transportation, logistics, manufacturing, security etc, and has become a focus of the current researches.Tag collision problem seriously affects the data integrity of RFID system and greatly reduces the performance of the system. Therefore, it's of great significance for the entire system to achieve low complexity tag anti-collision algorithm with high throughput rate under the control of costs.The thesis firstly introduces the composition and basic principle of RFID system, makes analysis and simulation on the existing tag anti-collision algorithm. Then, the thesis proposes an adaptive multi-tree anti-collision algorithm based on prefix detection on the basis of existing deterministic anti-collision collision algorithm(AMPD algorithm). AMPD detects collision branches by introducing controllable idle time slots, which thereby avoids the generation of more free time slots and collision slots. Theoretical analysis and simulation results show that AMPD has higher system throughput rate than the existing deterministic anti-collision algorithm. The thesis also proposes an enhanced bit-slot group frame slotted ALOHA algorithm(EBGFSA algorithm) based on the existing probabilistic anti-collision algorithm, EBGFSA introduces bit-slots to recognize the collision slots, which makes the system throughput rate nearly doubled based on the conventional ALOHA algorithm. When the number of tags is large, EBGFSA uses appropriate grouping and combining strategies to maintain high system throughput rate, it also greatly reduces the number of query cycles. The thesis also presents a set of tag estimation algorithm for EBGFSA. theoretical analysis and simulation results show that the estimation error is less than 5%. At last, the thesis proposes a sectional bit-slot group frame slotted ALOHA algorithm(SBGFSA algorithm) on the basis of EBGFSA, SBGFSA divides the bit-slot segment into two isometric parts, while maintaining the high system throughput rate, the query cycles are further reduced, which improves the stability of the system.