User's Manual

Boomer-III User Manual & Integrator’s Guide__________________________ Appendix D - Application Development
BM310012WT04 125 Copyright Wavenet Technology © October 2003
new channel scan) is about 9 minutes for DataTAC 4000 networks.
DataTAC 5000 networks respond typically in 1.5 Power-Save protocol
frame times, or about 96 seconds.
Wireless Data Systems Considerations
The wireless modems application developer must account for the
limitations of a wireless data system to minimize their impact on the
user.
Limited Data Capacity on Radio Frequency Channels
The channels available to wireless modems are narrow-band and have
limited information carrying capacity (bandwidth) when compared to
traditional wire line communications. Additional capacity can be
gained only by increasing the number of channels, improving the
hardware technology, or by developing more efficient applications. As
a result of all these limitations, it is not surprising that wireless
networks are often more expensive to operate on a per-packet basis
than wire line Wide Area Networks (WAN). To address this concern,
the NCL has been designed to provide the most efficient way of using
the limited channel bandwidth.
Message Delivery Cannot Be Guaranteed
Because a wireless device can roam without restriction, it can exit the
network RF coverage area, leaving it unable to receive or successfully
transmit messages. When a device is outside the coverage area, the
applications are informed of failed inbound delivery. The application is
required to take appropriate recovery action.
Variation in Message Transit Times Across the Network
The time interval messages transit the network is affected by the RF
protocol, the message load on the network, and the length of a
message. These variations might need to be taken into account by the
application.
The following sections address some of these shortcomings in more
detail.
Application Efficiency
One goal of application development is to provide the required
functionality with the least amount of messaging. The consideration
here is to minimize the number of interactions in an information
exchange. Doing so addresses the limited data capacity and increased
costs of wireless messaging. In addition, the pricing structure of
network operators encourages efficient application design. In fact,
applications can be designed to use data compression or to apply
techniques that send only data fields that change between transactions.
Large Message Transfer
Message size is a key factor affecting response times in wireless data
systems. To efficiently accommodate typical data applications, the