In standard GSM 03.09 there are listed two possible variants:
1. simple switch from old path to new path (e.g. in case of inter BSC hadover switching of voice channel from path oldBSC-MSC-other party involved in call to newBSC-MSC-other party involved in call)
2. there exist some intermediate state in time of that it is conneted together two paths oldBSC-MSC-other party involved in call, newBSC-MSC-other party involved in call. through connection is done by means of three party bridge.
Does anybody have idea how is usually implemented switching of voice path in MSC during handover? If the first variant or the second one is used or both are implemeted together and MSC’s administrator can chose one of them? THANKS.
Part of GSM 03.09 specs:
The handover device can either be a three-party bridge or a switching facility without three-party
connection capabilities. For a three-party bridge configuration the states of the handover device are as
shown in table 1. The three-party configuration exists in the intermediate state. This type of handover
device may reduce the interruption time. However, this may require noise reduction if one of the radio
channels is unterminated at some time in the intermediate state.
For a handover device consisting of a simple switch there will be no intermediate state.