(PER) ASN.1 encoding rules for producing a compact transfer syntax for data structures described in ASN.1, defined in 1994.
PER provides a much more compact encoding then BER. It tries to represents the data units using the minimum number of bits. The compactness requires that the decoder knows the complete abstract syntax of the data structure to be decoded, however.
Documents: ITU-T X.691, ISO 8825-2.