7-20 Using the Internal Modem
Writer: Carey Gregg Saved by: Rebecca Wiggins Saved date: 02/06/98 11:07 AM
Part Number: 314932-001 File name: Ch07.doc
How the Environment Affects Cellular Performance
Cellular data communications can be used from most locations
where you are able to connect with a cellular phone. However,
cellular networks were designed for voice communications and do
not work as well for data communications. Due to the inherent
nature of communication lines in a cellular environment, you must
have different performance expectations for cellular data
communications than for traditional noncellular communications.
Some characteristics encountered when sending data over cellular
networks are:
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Noise
■
Handoffs
■
Dead spots and dropouts
■
Bandwidth limitations
■
Signal strength
■
Network voice compression
■
Low signal strength
■
Unavailable channel
■
Power-down requests
■
Data bursts
Noise
Radio interference is common in metropolitan areas where cellular
phones are prevalent. The interference includes other cellular
users as well as electronic appliances and equipment.
Handoffs
As the mobile user changes cells, the signal strength on the
channel drops, and the MTSO (Mobile Telephone Switching
Office) may change (handoff) the user to a different cell and
frequency where the signal is stronger. This handoff may interrupt
the channel for 200 to 1200 milliseconds. A cell handoff may also
occur even when stationary because of varying traffic loads.
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