Operation Manual

145
6 Possible Errors and Remedies
English
6.4 Environmental Influences on Data and
Telefax Communications over GSM
A basic characteristic of Mobile ISDN by AVM is its high
reliability. Nonetheless, cellular telephone networks, as
compared with the stationary ISDN network, may sacrifice
a certain degree of quality for the sake of mobility. The
error-correcting data link layer (RLP, Radio Link Protocol)
integrated in the Mobile ISDN-Controller guarantees error-
free transmission over the GSM link (BER<10
-8
). When the
radio connection is poor, however, the effective data
transmission speed may decline. To obtain the best
possible connection and maximum working speed, try to
optimize the following factors.
Signal intensity: Maximum microwave signal intensity is
advantageous. The signal strength can be displayed on
your cellular phone. Microwaves reflected by metal
objects in your environment may cause destructive
interference and weaken the signal. Inform your cellular
network operator about problems of this kind. Microwave
absorption can also result in a weak signal inside a
vehicle, or in or near reinforced concrete buildings.
EMI (Electromagnetic Interference): Interference effects
due to the emissions of other nearby cellular phones or
other electronic equipment may impair performance.
Handover: When traveling, or when network loads are
high, your telephone can be transferred from one GSM
cell to another during a connection. The change in carrier
frequency and signal intensity may result in delays in
communication. If this causes problems, please notify
your cellular network operator.
Doppler effects: Traveling at high speeds can cause a
shift in the effective transmission and reception carrier
frequencies. GSM allows the telephone to travel at a
maximum speed of about 250 km/h.