IrLAP – Infrared Link Access Protocol

1. IrLAP – Infrared Link Access Protocol By Mary Hsieh and Peggy Shen

2. 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

3. Intro – Bit and Byte Ordering • Datagram form • Binary form • Hex form • Multiple Byte Form • Note: Half Duplex

4. OSI Model Application Presentation Session Transport Network Data Link Physical TCP/IP Model Application Transport Internet Host-to-Network Intro (background info) – OSI and TCP/IP Models

5. Services – Definition • Request • Indication • Response • Confirm Upper Layer Upper Layer Response Indication Request Confirm IrLAP Layer IrLAP Layer Packets transferring

6. 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

7. Connection Oriented Service • Connect Services • Sniffing Services • Data Services • Status Services • Reset Services • Disconnect Services • Example: IrLAP_service.request(Handle)

8. 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

9. 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

10. 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

11. Example of a Packet • A normal packet

12. 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

13. IrLAP Description of Procedures

14. Steps to Connect, Transfer, and Disconnect

15. 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

16. 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.

17. 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.

18. Bibliography • http://www.irda.org/standards/specificationsoldest.asp