User's Manual

Boomer II User Manual & Integrator’s Guide __________________________ Appendix D - Application Development
BM210012WT37 119 Copyright Wavenet Technology © November 2003
Roaming Issues
During development, consider how the coverage for your wireless
enabled application could be affected by a user moving in and out of
the network coverage area. Coverage can be temporarily impacted by
moving from one side of a building to another. Coverage can be lost for
a longer time by moving beyond the network coverage boundary.
In application development, addressing this temporary or longer term
gap in coverage, even in midst of an application transaction, is
essential.
You can address this consideration by providing a transport level
protocol that can account for the following roaming related situations
when used with a DataTAC wire-less modem:
 Inbound SDU failure
 Outbound SDU failure
 Loss of network contact
These situations are discussed in detail from page 121.
In this case, the transport level protocol must have components both
within the server and client application environment. This transport
level protocol can be provided using existing third party software for
DataTAC systems. Alternatively, you can develop a transport level
protocol with your application in mind.
Roaming Requirements
The roaming algorithms for the wireless modem are described as
follows:
Note: In each case, re-establishing network contact requires the
wireless modem to scan all likely channels and to handshake with the
network.
Send a quick (bounded) response to SDU transmit requests
When the wireless modem loses network contact, SDUs are returned
with an out-of-range failure code. In this case, the wireless modem also
indicates that it is out-of-range via an NCL event. When network
contact is re-established, the wireless modem indicates an in-range
event. The client application then resubmits any SDU last rejected with
an out-of-range response.
Acquire the channel quickly
All channels are scanned quickly, starting with the dynamic channel
list that contains the last used channel and its neighbours. (This list is
broadcast periodically by the network.) If you cannot establish network
contact using the dynamic channel list, the wireless modem scans
quickly using the pre-programmed, network-specific static channel list.
If network contact is not established using either list, this sequence is
repeated after a delay interval. See “Conserve battery life when out of
range” below.