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PCRAbbreviation for preventive cyclic retransmission in SS7 signaling. It is a non-compelled, positive acknowledgement, cyclic retransmission, forward error correction system. Mainly used for satellite links. A signal unit which has been transmitted is retained at the transmitting signaling link terminal until a positive acknowledgement for that signal unit is received. During the period when there are no new signal units to be transmitted all the signal units which have not yet been positively acknowledged are retransmitted cyclically. The forced retransmission procedure is defined to ensure that forward error correction occurs in adverse conditions (e.g. high error rate and/or high traffic loading). When a predetermined number of retained, unacknowledged signal units exists, the transmission of new signal units is interrupted and the retained signal units are retransmitted cyclically until the number of unacknowledged signal units is reduced. |