IrDA Wireless Protocol

IrDA

• IrDA stands for the Infrared Data Association
  
• Founded in 1993 to “set and support hardware and software standards which createInfrared communications links”.
  
• IrDA technology is a connection technology that uses Infrared light to transfer data.
  

Features of IrDA Technology

• Point-to-point connection
  
• Line of sight transmission
  
• Maximum data rate of 4 Mbps
  
• Range <>
• Built in encryption CRC

IrDA Module

1. Transceiver
   
2. Packetiser
   
3. Encoder/Decoder
   
4. Processor
   

Data Rates

• Serial IR- 115.2 kbps
  
• Medium IR-1.152 Mbps(rarely used)
  
• Fast IR-4 Mbps(latest phones ,cameras etc support this standard)
  
• Very fast IR(16 Mbps)
  

Modulation

• Quality and speed of IR communications are mainly limited by the bandwidth of IR txrs
  
• Use a modulation technique with high BW efficiency and a low bit rate and high power efficiency
  
• IrDA has continuously improved the modulation techniques of its standards by introducing RZI for SIR mode, 4PPM for FIR and HHH for VFIR.
  

IrDA Standards

• It is a set of specifications for providing a universal two way wireless IR data communications
  
• Defines the physical characteristics of the interface, the communication protocols and the transmission speeds
  
• It is a set of specifications for providing a universal two way wireless IR data communications
  
• Defines the physical characteristics of the interface, the communication protocols and the transmission speeds

Architecture

Protocol Architecture

The IrDA Data Protocol consists of a mandatory set of protocols and a set of optional protocols.

Mandatory Protocols

1. IrPHY(Physical signaling layer)
   
2. IrLAP(Link Access Protocol)
   
3. IrLMP(Link Management Protocol)
   
4. IAS(Information Access Protocol)
   

Optional Protocols

1. IrCOMM (IR communication protocol)
   
2. Tiny-TP (Tiny transport protocol)
   
3. IrOBEX (IR object exchange protocol)
   
4. IrLAN (IR local area network protocol)
   

IrPHY

• Basic level of IrDA specifications
  
• Necessary in all IrDA devices
  
• Lays out the angle limits, speed range, distance range and modulation
  

IrLAP

• Responsible for performing device discovery and negotiation
  
• Provides a reliable transmission medium on which to build additional communications
  
• Based on HDLC protocol
  
• Responsible for preserving the physical connection
  
• Facilitates error detection, retransmission of lost or damaged packets & rudimentary flow control

IrLMP

• Allows one or more IrDA services to run over a single IrLAP connection
  
• Applications using an IrDA stack can read/write directly to IrLMP, or can use other higher level protocols that in turn, read/write to IrLMP
  

IAS

• It is the only required service available through IrLMP
  
• It is the mechanism by which applications advertise and access services
  
• Applications are given a specific selector called an LSAP(Link Services Access Point)selector ,by which the service can be accessed by other devices
  
• TinyTP-flow control is offered ensuring that device buffers do not overflow
  
• IrOBEX-allows transfer of files easily between devices.
  
• IrCOMM-allows emulation of serial and parallel ports.
  
• IrLAN-allows LAN access for the device.

Advantages

• Low power requirements
  
• Low circuitry cost:$2-$5 for the entire coding/decoding circuitry
  
• High noise immunity
  
• Higher security
  
• Few international regulatory constraints
  
• Simple circuitry
  
• portable
  

Disadvantages

• Low speed
  
• Very small range of coverage
  
• The device need to be within a 30 degree arc of each other.
  
• Distance between the devices can affect the rate of transfer

Applications

IrDA technology is used in

• Intrusion detectors
  
• Home entertainment control units
  
• Robot control systems
  
• Medium range LOS laser communications
  
• Cordless microphones, headsets, modems, printers & other peripherals