Question

mention some RFID anti-collision protocols ?

Answer 1

Some of the RFID anti- collision protocols are -

1. Aloha Protocols

Aloha-based protocols use a random-access strategy in order to successfully identify the number

of tags in an interrogation area .They belong to the group of probabilistic protocols because the

tags transmit their own ID in randomly selected slots in a frame in order to reduce the possibility of

a collision. However, there is no guarantee that all of the tags will be identified in the interrogation

process. These protocols suffer from the well-known tag starvation problem, in the sense that a tag

may not be correctly read during a reading cycle due to an excessive number of collisions with that

same tag. Every frame consists of a certain number of slots, and the tags can only respond once per

frame The main Aloha-based protocols can be divided into four subgroups: Pure Aloha (PA),

Slotted Aloha (SA), Frame Slotted Aloha (FSA) and Dynamic Frame Slotted Aloha (DFSA) protocols.

2. Tree-Based Protocols

One of the main features of tree-based protocols is that they are deterministic, since ideally,

they are designed to identify the whole set of tags in the interrogation area . These protocols

have simple design tags and work very well with a uniform set of tags.

Tree-based protocols usually work with a muting capability since they need the identified tags to

remain quiet after their identification. These protocols usually work using queries, which are broadcast

commands transmitted by a reader to require the tags to respond. If a tag’s ID does not match the

query, the reader command is rejected.

First, the most popular tree-based protocols are presented here. Then, a selected group of protocols

will be presented with the common feature of the use of Manchester coding. The first group includes:

Query Tree (QT), Query Window Tree (QwT), and Smart Trend Transversal (STT). Another group

consists of tree-based protocols that use Manchester coding: Binary Search (BS), Collision Tree (CT),

Optimal Query Tracking Tree (OQTT), and Collision Window Tree (CwT).

3. Hybrid Protocols

Hybrid protocols combine the advantages of tree-based and Aloha-based protocols to avoid their

problems and provide better features in tag identification . Most of them first implement

a tree-based procedure and tag estimation procedure in order to predict the number of tags.

Therefore, the combined Aloha-based and tree-based protocol procedures are known for their high

complexity and hardware demands. This kind of protocol can significantly increase performance as

compared to the previous ones.

Recent proposals include the Tree Slotted Aloha (TSA) and Binary Tree Slotted Aloha (BTSA).

TSA uses a tree structure, and the tag’s responses are organized in slots, as in FSA. In the BTSA protocol,

tags randomly choose a slot after the reader query.