Service manual

• Digital Air Interface – The GSM phone will provide an entirely digital link
between the telephone and the base station, which is, in turn, digitally linked
into the switching subsystems and on into the PSTN.
• ISDN compatibility – ISDN is a digital communications standard that many
countries are committed to implementing.. It is designed to carry digital voice
and data over existing copper telephone cables. The GSM phone will be able to
offer similar features to the ISDN telephone.
• Security and Confidentiality – Telephone calls on analogue systems can very
easily be overheard by the use of a suitable radio receiver. GSM offers vastly
improved confidentiality because of the way in which data is digitally encrypted
and transmitted.
• Better Call Quality – Co-channel interference, handover breakes, and fading will
be dealt with more effectively in the digital system. The call quality is also
enhanced by error correction, which reconstructs lost information.
• Efficiency – The GSM system will be able to use spectral resources in a
much more efficient way than previous analogue systems.
In the figure below, the area bounded by bold lines represents the total coverage area of a
hypothetical system. This area is divided into several cells, each containing a cell site
(base station) operating on a given set of channels which interfaces radiotelephone
subscribers to the telephone switching system.