56k PCM Modem Software Available from GAO

Toronto, Canada: GAO Research & Consulting Ltd., a leading supplier of modem technology, has developed 56k PCM modem software called GAO 56K, which complies with the draft of the forthcoming International Telecommunications Union standard and will comply with the final version. GAO 56K is implemented in ANSI C, running as a software modem in a host Pentium. GAO 56K has been tested using a TSB37A model and a TSB38 test suite. Several leading communications and electronics companies have just signed deals to license the software.

GAO 56K is a practical technique to extend V.34 analog modem capabilities. An internet service provider (ISP) is assumed to be digitally connected to the internet and to a telephone company’s central office (CO). The CO extends the downstream connection via a line card with a digital to analogue converter (DAC), providing a pulse amplitude modulation (PAM) analog signal to GAO 56K. The downstream signal consists of 8 thousand symbols per second with each symbol maximally coded from 7 bits of each 8 bit pulse code modulation (PCM) word. This translates into 128 possible amplitude levels in the PAM signal compensating for µ-law companding effects. On the upstream side (using GAO 56K to upload to the internet), data rates of 28.8 kbps or 33.6 kbps are available.

GAO is porting GAO 56K to other platforms including the DSPs of Texas Instruments and Analog Devices, as well as MIPS, ARM and other RISC processors. GAO also offers a complete suite of modem software, including V.34 in fixed and floating-point C for microprocessors such as Pentium and ARM, and assembly languages for DSPs such as TMS320C6x/54x and ADSP21xx.