Page 129 - DCAP311_DCAP607_WIRELESS_NETWORKS

Unit 7: Wireless LAN

Once the session was started, application startup was not an issue at all, which was Notes
expected since the applications run on an application server that has a high speed LAN
connection to back-end services. Screen updates for all applications tested (MAXIMO, Web
client and GroupWise) ranged from 10 to 15 seconds. This was about the same speed as a
remote Web client but significantly faster than a remote MAXIMO client.
The biggest problem with using MetaFrame, however, is that it is not tolerant of
intermittent connections. Even in the absence of any application processing, driving out
of range of the Metricom base station would terminate the MetaFrame session as well
as all the application sessions. With this architecture, text input proved very slow for all
applications—not surprising since every character typed by the user would have to be
echoed over the wireless link by the application server.

Wireless Middleware
The last architecture tested was wireless middleware. The particular middleware chosen
for testing was Smart IP* from Nettech Systems, Inc. Smart IP has a number of different
capabilities, but the one of greatest interest is its ability to make IP communications more
efficient over wireless networks. It achieves its efficiency through a number of mechanisms,
including compression as well as replacing TCP with its own wireless-optimized transport
protocols. These transport protocols are used over the wireless connection between the
middleware client software that is installed on the mobile computer and the mobile server
as Figure 3 shows. The net result is transmission of fewer and smaller packets.
Actual test results with Smart IP showed noticeable data transfer gains. Using a browser
application, Smart IP reduced the time required to download pages by an average of about
25%. For example, a page that took 20 seconds to download without Smart IP would on
average take 15 seconds with Smart IP. The utility tried to configure Smart IP to operate
directly with MAXIMO, but tests were postponed due to configuration difficulties.
The utility found that different applications worked better using different approaches.
Only through testing could the utility determine how their applications would function in a
wireless environment. Though applications generally ran slower than over dial-up modem
connections, with the right approach, applications run well enough to be deployed in the
field. The utility also found that the number of software approaches available increased
during the course of its project.
The Changing Application Landscape
Computer technology continues to evolve rapidly, as software vendors keep revising
and improving their applications. The utility experienced a number of changes that had
implications on their wireless strategy. In particular, the number of software approaches
available to support wireless networking expanded.
The utility upgraded from GroupWise version 4.1 to version 5.2. With the older 4.1 version
there was no easy way to provide remote access other than by using Citrix MetaFrame. But
version 5.2 includes TCP/IP support as well as a Web browser client thus adding two new
paths for providing remote wireless access. The most attractive approach appears to be the
TCP/IP client; testing is under way to confirm this.
Another change involves PSDI, the maker of MAXIMO. Realizing the importance of wireless
communications for field service workers, PSDI began to architect their next generation
of software to better support wireless networking. In the new version, MAXIMO offers
a Web-based interface to mobiles using HTML protocols. HTML is a far more efficient
approach than extending the SQL database protocols all the way to the mobile computer.
This new "wireless friendly" version of MAXIMO is release 4 and the utility plans to
upgrade from release 3. Once it does, the Web interface to MAXIMO will probably be the
preferred approach for mobile field workers.
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