Slides

RFID Readers

Definition

• RFID reader (interrogator) works as a transmitter as well as a receiver of radio frequency signals

• A signal is broadcast and received through antennas that are connected to the interrogator

Components of an RFID Reader

• RF transmitter + RF receiver (RF module)• Control unit (computer)• Communication channels going to antenna• Network or peripheral devices• Circulator (for mono-static antennas –

used to broadcast and receive from the same antenna port)

RF Transmitter Components

• Oscillator: creates a carrier frequency (the frequency the reader is operating on)

• Modulator: modulates the carrier wave from the oscillator in order to include data/commands intended for the RFID tag

• An amplifier that strengthens the signal before it is transferred to the antenna

RF Receiver Components

• Demodulator: extracts data from the received signal that comes from the tag through the interrogator’s antenna

• Amplifier: strengthened the demodulated signal before it is sent to the central unit for further processing

Control Unit Components• Microprocessor

– Controls functions of interrogator– Governs data transmission– Processes and filters received data– Sends data via network to middleware and other

applications– Communicates with memory

• Memory– RAM – ROM – where operating systems is stored (e.g. Linux

or Windows CE)

Read/Write Capability

• R/W ranges vary based on– Interrogator quality– Tuning– Characteristics of antenna– Tags– Environmental conditions

• Interference• RF noise• Materials• Humidity

Read Range

• Read range: the distance over which the reader can successfully read data from a tag

• Loss in read range follows the inverse square rule (1/d^2)

Write Range

• Write range – distance over which the reader can successfully write data to the tag

• Write range is usually a lot shorter than the read range – insures hire reliability of writing procedure

• Writing process is sensitive to environmental conditions

• Interference should be avoided

Devices Operated by a Reader

• Light stacks• Audible devices: horns and beepers• Gate triggers for opening the doors• Conveyor diverters• Box pushers using a hydraulic arm• Vehicle tollgates• Video Cameras

Configuring Reader

• A reader can be configured by:– Middleware– Reader deployment tool (ODIN EasyReader)– Reader’s GUI

Dumb/Smart Reader

• Dumb reader – can only read smart tags• Smart reader – has additional capabilities

Smart Reader Capabilities: Filtering

• Filtering – instead of reading all available data from tags and transferring the data to the host, a reader acquires only necessary data

Smart Reader Capabilities: Cycle Acquisition

• A reader can be set for continuous polling of tags or it can poll in preset time intervals (e.g. every 5 seconds)

• Reduces amount of data going through the system

Smart Reader Capabilities: Cycle Acquisition

• Real-Time: the reader transfers data as soon as it acquires them

• Batch: data collected and sent to the host in batches

• Triggered: Data are collected and sent to the host only when triggered by a certain event or by the user

Smart Reader Capabilities

• Managing sensors (e.g. motion sensors)• Triggering interrogation (from a sensor

signal, based on time, or manually)• Dense reader mode operations• Anticollision capabilities

Reader Communications

• Reader-talks-first (RTF)• Tag-talks-first (TTF) – a tag can beacon its

serial number to the environemnt

Frequency-Hopping Spread Spectrum

• Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver.

• Advantages:– Resistant to interference– Difficult to intercept– Can share a frequency band

Listen-Before-Talk

• Listen Before Talk: communication protocol that requires an interrogator (reader) to listen on a channel before transmitting to determine if that channel is being used by another device

• If the channel is already in use, the interrogator will switch to a different channel.

Transmission Restrictions by Region

Transmission Restrictions by Region

EPC Generation 2 Reader Commands

• Select – picks out a group of tags based on certain characteristics (e.g. manufacturer ID)

• Inventory – isolates individual tag from the group

• Access – addresses a specific tag– Lock– Kill

Firmware Upgrades

• Fixed bugs• New capabilities

Interrogator Types

• Fixes Interrogator• Mobile Interrogator

– Vehicle mounted– Handheld

Nokia Mobile RFID Kit

• The Nokia Mobile RFID Kit allows the user to launch services and access phone functions such as dial or send messages by touching an RFID tag

• Tasks, such as browsing the latest service instructions or logging time stamped data like meter readings, can be automated and initiated with just a touch.

Source: http://www.nokia.com/nokia/0,,55738,00.html

Nokia Mobile RFID KitColor: Black

Dimensions: 106.5 x 46.8 x 26.7 mm (with the phone)

Weight: 111.2 g (with the phone)

Display: Phone display: 27.3 x 27.3 mm,4096 colors in 128 x 128 pixels

5 lines for text in basic mode with 16-pixel font

Durability: Xpress-on™ RFID Reader Shells provide protection against splashes and dust

Power: Phone battery: BL-5B, 760mAh,talk time up to 2h-5h

Frequency: 13.56 MHz

Protocol: MIFARE® UltraLight

Read range: Typically 2-3 cm, tag dependent

Standard: ISO 14443A

Nokia Mobile RFID KitPotential Uses“Touch and Browse”

• Service Professional: Touch the item to be serviced and you will get up to date service information.

• Machine Operator: Touch a tag attached to the machine and a new work order is available from a web page.

• Database Search: Touch a tag to automate extensive search strings.

• Report Failure Reasons: Touch a tag and get linked to a page to enter the reason for failure.

• Report Materials Used: Touch a tag and get linked to a page to enter the materials used.

Nokia Mobile RFID KitPotential Uses“Touch and Record”

• Meter Reading: Touch a tag attached to a meter and the meter readings are recorded in the phone. Time stamp and tag information is available automatically.

• Security: Attach tags to sites that are visited by security guards. Get accurate time stamps and proof of work done.

• Recording Travel Expenses: Attach a tag to the dashboard of a car. Touch and enter beginning and ending mileage to have time stamped data for a travel expense form.

Nokia Mobile RFID KitPotential Uses

“Touch and Send Automated Message”• In a Car: Place a tag on the dashboard and order

operator text message services such as finding the nearest restaurant, florist, bank, post office, etc. Receive weather, traffic or news reports or information such as restaurant menus.

• Report Activities Back to Office: Report work done by sending confirmation back to office - e.g., confirm cargo delivery by having a tag at the customer premise. Preventative maintenance: touch the serviced machine/object and report work done.

• Time and Attendance System: Build your own time and attendance system. For example, personnel could use personal tags to touch a single phone in the office, at a construction site or filed office to clock in and out.

Nokia Mobile RFID KitPotential Uses

“Touch and Call”

• Visual Phone Directories: Attach a tag behind a person's photo to initiate a call to them. Simplify making phone calls for those not used to mobile phones or those who have physical limitations. Create a personal directory for children or the elderly.

• Distress Assistance: Touch a tag on your clothing such as a belt, and the phone initiates an emergency call.

Dwell Time

• The time tag is present in the zone

Antenna Design

• Mono-static antenna – one antenna for receiving and transmitting signal– Circulator

• Bi-static antenna - one antenna for receiving and one for transmitting signal

RFID Portal

Shielding

• Shielding each zone prevents interference and reading tags that belong to other zones

• Materials– Metal mesh with holes significantly smaller

than wavelength– Absorptive foam

Dense Reader Environment

• Environment where the number of readers is larger than the number of available channels– Slower read rate– Network traffic

• Solutions• LBT• Frequency hopping• Multiplexing

– Time– Frequency

Tag Anticollision

• Synchronous (deterministic)• Asynchronous (probabilistic)

– ALOHA (Q-Algorithm)