Software for Telecoms & Audio
V.17 Modem TMS320C5000 DSP Code
implements the ITU Data Modem function V.17, which provides half-duplex
data transmission at rates of 14.4, 12, 9.6, & 7.2kb/s over the telephone
network for use in Group 3 Fax equipment. Good error performance is assured
by the use of trellis coding and adaptive equalisation. A fast-train algorithm
is implemented for resynchronisation after initial training. The assembler
software is in the form of callable subroutines, eg for initialisation
and for main-routine processing of input/output sample blocks and data.
The user is responsible for interfacing samples and data to hardware.
at the sample interface, the code can operate at 8.0kHz and 9.6kHz sample
rates. Transmit and receive samples are transferred on a common clock,
to which the transmit clock is synchronised. The receive clock is interpolated
in the DSP code for synchronisation to the far-end modem. At the data
interface, data is transferred in buffers under pointer control.
Performance: sophisticated techniques have been incorporated into the software to give excellent performance under noisy or poor line conditions. Over flat channels, near matched-filter performance is obtained. Over very severe channels such as the TAS Telephone Network Emulator ConUS Poor Voice channel 30dB attenuation across the 3kHz band the modem code will still operate at 14.4kb/s. SNR for 10-6 Error Rate at 14.4kb/s (4kHz BW noise):
#figures are for TMS320C54x operation with the assembler interface
Availability: NOW - sale is under licence - integration support offered