Phone Line Digital Communications

 

Telephone line QAM modem transmitting at 9600 bits/s.

 

This project required a design, simulation and real-time implementation on the DSP platforms (Motorola DSP 56002 and MASC 3500 were used). Initially, it was my graduation thesis. The basic problems that I had to solve were:

Adaptive equalization (the LMS gradient algorithm was applied)

Synchronization system (carrier and timing recovery)

Detector

 

I have designed and implemented the demodulator that was based on an internal modulator and a channel model that is estimated during the initial training procedures. The implementation was fully DSP oriented. Real-time communication sessions were tested on a physical model of the telephone line.

 

Filter bank for tone detection on telephone line.

It was a design, simulation and a real-time implementation on the DSP platform (Motorola DSP 56002 was used). It was tested on real telephone lines in the case of FAX communication sessions detecting initial fax-pilot tone.

 

DTMF transmitter and receiver.

This project required a design, simulation and real-time implementation on the DSP platform (MASC 3500 was used). The receiver design was based on a modified Goertzel algorithm.

 

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