GSM Voice Mail Service TDM Call Control

Sammanfattning: The Voice Mail Service (VMS) enables forwarding of calls to a dedicated Voice Mail Server (VMS) on behalf of the call receiving subscriber during certain conditions such as 'busy subscriber', 'no answer', 'always', etc. The standardization forum 3GPP has specified the Global System for Mobile communication (GSM) while the standardization forum ITU-T has specified the Integrated Services Digital Networks  (ISDN) User Part (ISUP) call control protocol. Both of these standards rely on the use of Time Division Multiplex (TDM) as a media bearer and SS7 as signalling bearer, where both bearers require use of very expensive telecom-specific hardware. The thesis proposes the solution to use RTP as media bearer and IP as signalling bearer towards the handset in GSM and only use TDM as media bearer and SS7 as signalling bearer towards the VMS. The thesis demonstrates  the feasibility and the advantages provided, by creating an implementation in Erlang/OTP and testing it to check if it confirms to the specification.