Non Transparent communication utilises a special GSM network-based error correction facility called "Radio Link Protocol" (RLP) that ensures more robust transmission.
What this essentially means is that the GSM network's IWU will add special error correction codes to control the flow of data.
This ensures that the data transmitted first obtains a special acknowledgement signal from the receiver that informs the transmitter that the data has been received as transmitted and that the receiver is ready to receive the next set of data from the transmitter.
If there is no such acknowledgement signal from the receiver, the networks will utilise their "data buffering" feature by using a special "forward correction" technique to ensure uninterrupted data transmission throughout.
A non transparent data call can be started on V.110 (link a ISDN data call) or on V.32.( like in a PSTN modem). The benefit of a V.110 call is that the two modems ore synchonise faster then in a use of V.32.
The transmit by RLP has every time a small delay included. If you have to come to real time, then you have to use the not save transparent tranmission.