A sequential reading strategy to improve the performance of RFID anti-collision algorithm in dense tag environments

In general, RFID system consists of a reader and number of tags (embedded in the objects to track them). During the identification process, invoked by the reader to collect the tags´ information, multiple tags transmit their information (or IDs) using a shared wireless channel. If multiple tags have concurrent transmissions then the reader perceives it as a collision. The frequency of collision increases when the number of tags inside the identification zone increases, in result the performance of the system degrades heavily in terms of identification efficiency. One of the commonly adopted anti-collision algorithm is Frame slotted Aloha (FSA) which has been standardized in EPC Global G2. This algorithm attempts to adjust the frame size with estimated number of tags and shows good performance results when the number of tags to identify is small. However, due to unknown tag population, the allocation of suitable frame size becomes unreliable for large set of tags. In this paper we propose a Sector and Power based Grouping (SPG) algorithm that confines the tags within the interrogation zone in small groups. The identification process for each group is then operated sequentially. Indeed, grouping of large set of tags highly decreases the collision ratio and further allows us to allocate a reliable frame size which substantially increases the efficiency of the system.