Operation Manual

134
Appendix A: Technical Information on GSM Operation
A.3 Environmental Influences on Data and
Telefax Communications over GSM
A basic characteristic of Mobile ISDN by AVM is its high
reliability. Nonetheless, mobile telephone networks, as
compared with the fixed 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 mobile 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 mobile
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 mobile network operator
Doppler shifts: 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.