A compound tag number estimation scheme for aloha based anti-collision algorithm in RFID networks

For the aloha based anti-collision algorithm in RFID networks, the tag collisions could greatly reduce the throughput of the system. If the number of tags is gotten, the throughput can be greatly improved. Based on the different performance of the maximum likelihood estimation and the moment based estimation, the compound estimation scheme combines the advantages of these two estimation schemes to enhance the estimation accuracy. A Hysteresis comparator is introduced into the compound estimation scheme to avoid ping-pang effect during estimation. Simulation results show that the proposed scheme has high estimation accuracy whether the frame is short or long.