User Manual

Application Development
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Boomer II User Manual & Integrator’s Guide
Wavenet Technology 84 BM210012WT09
In DataTAC 5000 systems, unsolicited outbound messages (or
messages that have missed the previous transmit opportunity) are
delivered in the “root” (that is, home) window for the recipient device.
Once the device is thus awakened, it remains awake for about n
seconds after each message or ACK transmission from the device.
During the wake time the network delivers messages to the device as it
would to a device that is non-compliant with the PowerSave protocol.
(Default n = 20 seconds for DataTAC 4000 networks and 8 seconds for
DataTAC 5000 networks.)
Roaming and location update reporting to the network happens more
slowly because the PowerSave protocol device takes longer to respond
to changes in the RF environment. The infrequent worst case latency in
responding to external stimuli (resulting in either a location update or
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 wireline 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 wireline 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.