Optical Wireless Link Protocols


The acceleration in the use of mobile and portable computing in recent years has led to a growth in interest in the area of wireless data communications and networking. Infrared (IR) in particular is increasingly being used for short range indoor wireless data communications. It is projected that 1.3 Billion IrDA standard IR links in products alone will be enabled by 2003.

The advantages of IR are that it is inexpensive, has low power consumption, has no spectral regulation, can support high data rates, and the radiation is confined to room space operation, it offers low error rates, and small form factor.

The Infrared Data Association (IrDA) was established in 1993 to develop an open standard for short range IR data communication, with the goal of having ease of use, interoperability and low cost. IR communications was already available, but mostly with independent, non-interoperable systems.

The protocol developed by IrDA, specifies a protocol stack which includes hardware and software, with the bulk of the complexity in the software stack. The link access layer of the stack, known as IrLAP (IrDA Link Access Protocol) is based on the existing HDLC (High-level Data Link Control) protocol which, or variations of which, is extensively used in datacommunications networks. The software stack also includes the IrLMP (IrDA Link Management Protocol), and an optional transport entity, the IrDA Tiny TP.


The objectives of the project are:

1. To determine the throughput performance of IrLAP under various BER conditions.

2. To identify optimum link parameters such as window size, frame size and turnaround time which can be adopted when designing such links.

2. Use of the OPNET package to model the protocol. This will enable a range of performance results to be obtained under a range of conditions and parameter values. From this it can be seen where certain inadequacies or problems can arise with the present specification. The processes defined in the IrDA specification documents are laid out in a state transition format which is well suited for modelling in OPNET.

3. The modelling in OPNET can also be supported by mathematical modelling and analysis techniques. A large body of literature exists on performance analysis of data communications protocols including HDLC and its derivatives. These can be modified and applied to the IrDA protocol.

4. Comparison with results from the OPNET simulation will provide a level of mutual verification. The results can also be verified through physical measurement of performance using real systems.

5. The second part of the objective is the use the OPNET model of the IrDA protocol to modify the existing protocol to provide services and applications not yet supported. This will be aimed at providing network access services, principally using ISDN and ATM.