Preventive Cyclic Retransmission(PCR) is a procedure for error correction. The PCR method is used in the message transfer part( MTP) of the signaling system No. 7. Preventive Cyclic Retransmission supports Message Transfer Part Level 2 (MTP2), for example, when the signaling link between the signaling link terminal and the signaling transfer point( STP) is via a satellite link.
Preventive Cyclic Retransmission is used if the sender has no new frames to send or if a positive acknowledgement( ACK) is not received. In this case, it then continues to send the unconfirmed frames as a preventive measure.