User's Guide

User’s Guide CDPD Operation

2110059 Rev 1.1 Proprietary and Confidential Page 55

To ensure that you can enter the complete string, you cannot set the maximum packet length less

than 5. You must also provide sufficient time in the PAD Inter-Character Timer to enter each

character. If this is to be manually typed, the value should be set quite high (or disabled

altogether). You must also avoid setting the PAD Primary Forwarding Character (+WS64) to one

of the three characters in the TIES string (A=65 ,T=84 ,+=43 ).

5.10. Data and Telemetry Applications

If you are communicating data files or telemetry using one of the modem’s PAD services (UDP or

TCP) that do not involve direct human interaction, you should make appropriate changes to the

packet management features of the modem.

Exact settings will depend on the nature of your application and the quality of your network

connection. What follows are some issues to consider.

If binary data is being communicated, you should disable the PAD Primary Forwarding Character

feature (+WS63=0) and use the PAD Inter-Character Timer (+WS70=5) instead. This will

prevent unusually small packets where the forwarding character might occur frequently in the

binary data. It will also ensure data is forwarded to the network within a roughly known period.

This allows the server to detect if problems have occurred at the client end.

The maximum packet length (+WS74) should be set as best suits the size of the data or telemetry

files you are sending. Remember that, in areas of poor network connectivity where

retransmissions are frequent, overall throughput may be improved by using smaller packet sizes.

Specific modem configuration samples for particular case studies may be available soon from the

Sierra Wireless Internet site at