IrLAP – Infrared Link Access Protocol
ByMary Hsieh and Peggy Shen
Points that will be addressed
The services that IrLAP providesThe assumptions that are made about the environment when the protocol is executedThe vocabulary of messages used to implement the protocolThe encoding of the messagesThe procedures
Intro – Bit and Byte Ordering
Datagram formBinary formHex formMultiple Byte Form
Note: Half Duplex
Intro (background info) – OSI and TCP/IP Models
OSI ModelApplication
PresentationSession
TransportNetwork
Data LinkPhysical
TCP/IP ModelApplication
TransportInternet
Host-to-Network
Services – Definition
RequestIndicationResponseConfirm
Upper Layer Upper Layer
IrLAP Layer IrLAP Layer
Request IndicationResponse
Confirm
Packets transferring
Data Link Services – (Continued)
Discovery Services Discover what devices are ready or
compatible
Address Conflict Services Resolves device address conflict issues
Unit Data Services Unreliable, connectionless way to send
data, usually through broadcasting
Connection Oriented Service
Connect ServicesSniffing ServicesData ServicesStatus ServicesReset ServicesDisconnect Services
Example: IrLAP_service.request(Handle)
Environment and Operational Characteristics - Configurations
Point to point, point to multipointHalf duplexHidden nodesNarrow infrared cone (15 degree half angle)Synchronize transmission speedNo collision detection
Data Link States and Modes
Connection state Has a connection
Contention state Waiting for a connection
Modes NRM – Normal Response Mode NDM – Normal Disconnect Mode
Frame Structure
To determine where the frame begins and endsTo determine whether the frame is intended for that stationTo determine what actions to perform with the information receivedTo detect the occurrence of transmission errors in received framesTo acknowledge its receipt of frames to the transmitting station
Example of a Packet
A normal packet
Elements of the IrLAP Frame
Address Field – 8 bits ( least significant bit is the command/response identifier bit)Control Field U – unnumbered S - supervisory I - Information
Information Field Must be a multiple of 8 bits
IrLAP Description of Procedures
Steps to Connect, Transfer, and Disconnect
Conclusion
What may be useful for our project We can use the broadcast command to send
out signal We know what the packets look like, so we
can use the oscilloscope to see what they look like in analog form
If we can’t use the IrDA port to transmit and receive signals through the skin, we could at least use it to transmit data that has been collected
Conclusion - Continued
What would impede our project Half Duplex – if data cannot move in both
directions at the same time, it may be difficult to send signals and get them back in a timely fashion
Start/End Header – if we send a signal to the skin, the skin would not be able to generate a packet with headers that tells the IrDA port to get ready for data reception
Bit Representation – it would be hard for us to control what is sent out in bits, etc.
Conclusion - Continued
Therefore, we have concluded that we cannot use the IrDA port to do what we would like it to do. We would need a separate piece of hardware between the PDA and the laser diode to do the job.
Bibliography
http://www.irda.org/standards/specificationsoldest.asp