VoIP Voice and Fax Signal Processing

14.11 V.17 MODEM

The V.17 modem operates in full-duplex and half-duplex mode with a continuous or controlled carrier. V.17 with a half-duplex modem is used for high-speed facsimile applications that operate at data rates of 14,400, 12,000, 9600, and 7200 bps. The transmitter and receiver of V.17 modems make use of Trellis coded modulations (TCMs) for intermediate bits coding and QAM for final modulations. The V.17 receiver implements the receive side of a V.17 modem, which demodulates the modulated signal and produces the bit stream. The V.17 transmitter implements the transmit side of a V.17 modem, which takes the coded data and produces a modulated signal. V.17 uses 2400 symbols per second and bits varying in each symbol. After considering one bit per symbol for Trellis coding, this gives usable bit rates of 7200, 9600, 12,000, and 14,400 bps. Refer to [ITU-T-V.17 (1991), Berg (2000), URL (SPRA073), URL (ADI Vol-2)] for more details on V.17. V.17 data transmission and signal details are listed below:

Baud rate and modulation: 2400 symbols, TCM coding followed by QAM modulations. Inclusion of data scramblers, adaptive equalizer, and eight-state trellis coding

Two sequences for training and synchronization: long train and resynchronization

Data rates: 14,400, 12,000, 9600, and 7200 bit/s synchronous

Center frequency: 1800 ± 1 Hz and no separate pilot tones are used

Power levels: Power output should not exceed 1 mW, and nominal level −13 dBm as per V.2

Signal detection: Signal is ...