Description
Like the later GAN/UMA standard, GIP makes use of a technology that doesn't require licensed spectrum to expand capacity and allow end users, in theory, to improve coverage in areas difficult to reach via large, external, cell towers.
GIP is a DECT profile, meaning a set of protocols that runs over the base DECT system. The most popular profile for DECT is GAP, which is used to provide cordless phone service, but this is not used for GIP.
In GIP, several of the GSM lower level protocols are replaced by DECT-friendly equivalents. Voice channels make use of 32 kbit/s ADPCM channels rather than 13 kbit/s FR/EFR/AMR channels, for example.
The system supports handoff, and authentication is done via the GSM SIM card as normal. However, DECT terminals need to authenticate themselves against the base station, and this added layer is implementation dependent.
The base station is usually connected back to the GSM network via an ISDN line. An "A interface" is implemented over the ISDN line just as it would be for a BSC. This allows multiple GSM calls and GSM control data to be multiplexed over the 64 kbit/s ISDN B channels.
Read more about this topic: GSM Interworking Profile
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