IrLAP – Infrared Link Access
Protocol
By
Mary Hsieh and Peggy Shen
Points that will be addressed
The services that IrLAP provides
The assumptions that are made about
the environment when the protocol is
executed
The vocabulary of messages used to
implement the protocol
The encoding of the messages
The procedures
Intro – Bit and Byte Ordering
Datagram form
Binary form
Hex form
Multiple Byte Form
Note: Half Duplex
Intro (background info) – OSI and
TCP/IP Models
OSI Model
Application
Presentation
Session
Transport
Network
TCP/IP Model
Application
Transport
Internet
Data Link
Physical
Host-to-Network
Services – Definition
Request
Indication
Response
Confirm
Upper Layer
Request
Upper Layer
Confirm
Response
Indication
IrLAP Layer
IrLAP Layer
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 Services
Sniffing Services
Data Services
Status Services
Reset Services
Disconnect Services
Example: IrLAP_service.request(Handle)
Environment and Operational
Characteristics - Configurations
Point to point, point to multipoint
Half duplex
Hidden nodes
Narrow infrared cone (15 degree half
angle)
Synchronize transmission speed
No 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
ends
To determine whether the frame is intended
for that station
To determine what actions to perform with
the information received
To detect the occurrence of transmission
errors in received frames
To 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/specifica
tionsoldest.asp