Anti-Collision Protocols For Radio Frequency Identification(RFID) Systems

The "Internet of Things"(IoT)contains in an idea where objects turn out to be part of the Internet:every object has its sole identification,and is accessible from the network,providing an extended Future Internet.Radio Frequency Identification(RFID)is a wireless technology that has swapped barcodes.This technology is used in today's world to track assets and people.It comprises of three components:the tag,the reader,and the middleware.The RFID tag stores data,the reader is used to identify the data stored in the tag or write data to the tag,and the RFID middleware is the application that connects the data that the reader obtains from the tag with the company inventory or database.RFID technology is an intelligent identification technique.Related to traditional automatic identification technology,it has the perks of small volume,low cost,large storage,reusability and high security.In Contrast to barcode readers,an RFID reader is talented of reading multiple tags located in its range.When this occurs,the probability of tag collision at the reader's end is high.To evade tag collision,anti-collision protocols are implemented.Slotted Aloha is one of the main anti-collision protocols used with RFID.The first half of the dissertation highlights the basic anti-collision protocols and its mathematical derivation covering the pure ALOHA and slotted ALOHA.We have explained that Pure ALOHA algorithm doesn't incorporate the recovery and detection mechanism.It can only make the reader identify and receive the data signals sent by the tags correctly at a certain angle,which they send at a certain point of time.The reader perceives the received information,and decides whether it receives correctly or a collision occurs.If the collision happens,the tags will hold for a long time and resend information.The reader in the wait approach will send a request signal,and the tags in the reader range will identify the command and reply to the reader by randomly selecting a slot in order to send the tag identification number to the reader.Collision happens when more than one tag answers to the same slot.Collided tags need to be read again.If none of the tags responds to the request command,then the request command will be repeated at recurring intervals.If the reader recognizes the tag identification number without errors(collisions),then that detected tag can be selected using the select signal to perform the read/write operation without colliding with other tags.When a large number of tags are sent,there is a very high probability that there will be more than one tag within the reader zone at some point in time.When the tags transmit their responses simultaneously to the reader,collisions will happen because the communication is happened over a shared wireless channel.Therefore,this high probability of constructing collisions due to the high number of radio frequency identification devices available will be an important issue to be solved.This dissertation proposed a mathematical model and a simulator to examine the behavior of Slotted Aloha protocol without interference.Tag detection is directly related to tag strength detected by the reader.RF signals act differently when objects are present in the environment.For example,water absorbs radio signals.When water particles are present in,the environment,tag detection will not be effective,since radio signals will be absorbed by the water.Therefore,water is considered as an interference constraint in tag detection.This dissertation also proposed a mathematical model and a simulator to analyze the performance of the Slotted Aloha protocol with interference.A comparison of both sets of results shows that the proposed mathematical model and the simulator are accurate.Results of the analysis show that the time required to identify tags with interference is longer than the time required to identify tags without interference.