ITU-T Recommendation V.110¶

V.110 is an ITU standard for bit-rate adaptation of low-speed async serial signals (600, 1200, 2400, 4800, 7200, 9600, 12000, 14400, 19200, 24000, 28800 or 38400 bit/s) to 64 kbit/s ISDN B-channels. It was primarily used in the context of interworking between GSM Circuit Switched Data (CSD) and ISDN.

Details¶

Frame structure¶

The protocol uses an 80bit (10 byte) frame. The Frame contains a frame sync pattern (similar to e.g. E1 TS0 or TRAU frames) consisting of the first byte and the first bit of every following byte.

Each frame consists of

• 17 bits of above-mentioned frame sync pattern plus:
• 48 D-bits (D1..D48)
• 7 E-bits (E1..E7)
• 8 S/X-bits (S1,S3,S4,S6,S8,S9)

Rate Adaptation Functions¶

RA1¶

The rate-adaptation function RA1 converts from the V-series rates (e.g. 2400bps) to an intermediate rate of 8/16/32/64 kbit/s.

RA2¶

RA2 converts from the RA1 output rate of 8/16/32/64 kbit/s to 64 kbit/s and is actually specified in I.460