Radio Frequency Identification (RFID) technology uses radio waves to identify objects wirelessly. The RFID system has many components. Among these the most important are the tags, the readers and the antenna. Both the tag and the reader have many subcomponents for their operation. The object is recognized by the reader in terms of transmitting the signal to the tag [4]. The RFID system has the following characteristics such as long life, less maintenance, no need for line of sight, non-contact technology, working in harsh environments and difficult tag duplication [10]. A tag collision occurs if more than one tag tries to communicate with a reader at the same time. The algorithm used to resolve tag collision is called anti-collision algorithm [4]. Previous classification of algorithms based on multiple access techniques [7]. They are as follows: SDMA (Space Division Multiple Access), FDMA (Frequency Division Multiple Access), CDMA (Code Division Multiple Access), and TDMA (Time Division Multiple Access). TDMA comprises the largest group of anti-collision algorithms, these are divided into reader-driven (reader speaks first) and tag-driven (speaks to tag first). In Reader Talk First (RTF), tags remain silent until addressed by the reader. In Tag Talk First (TTF), a tag advertises itself to the reader by transmitting its IDs. Between the two, TTF is very slow. RTF has two types such as ALOHA and Tree. ALOHA has three types: Pure Aloha (PA), Slotted Aloha (SA), and Framed SA (FSA). The FSA is divided into three types. They are: Basic FSA (BFSA), Dynamic FSA (DFSA) and Enhanced DFSA (EDFSA). The next major type is tree-based protocols. The types are Tree Splitting (TS), Query Tree (QT), Binary Search (BS), and Bitwise Arbitration (BTA) [7].TS sp...... middle of the document ...... read 20 tags ).As shown in fig. 4, collision cycles are reduced but it may not be able to identify all tags upon reentry, due to the tag starvation problem (PRB requires 14 cycles to read 19 out of 20 tags).VI. CONCLUSION The reinsertion issues involved in RFID tags are explained. The comprehensive investigation and classification of anti-collision algorithms of RFID tags have been described. This paper also analyzes the effect of the tag indentation problem in variants of binary tree algorithms. Due to the occurrence of collisions, both ABS and SRB algorithms are inefficient in handling the tag re-insertion problem and it is also difficult for the PRB algorithm due to the shortage of tags. Consequently, the ABS, SRB and PRB algorithms are essential to handle the tag indentation problem. These problems can be solved by including the frame information in the tag after the identification process