Does call between GSM users go through PSTN?

[chingkui]

Hi, I was told that GSM is an access network, does this mean that any call between two GSM users of the same network has to go through PSTN (or some other networks external to GSM)? Does that depend on the location of the two GSM subscribers? What if they are in the same cell (or same location area)?

Thanks.

 

[frankyu]

it's depends, if the carrier has their own transmission system, they needn't let the call through PSTN, for a MS(mobile subscriber) to MS call, MSC/VLR first analyse the called party number(it's a SS7 process,happen in STP-signal transmit point ), if it's belong to the same network, the STP overlay these signal to called party's HLR, to inquire the called party's current location, any return it to the calling party MSC/VLR to building circut, then do the paging.