In this thesis work, a 2400bps full-duplex all digital MODEM(ITU V.22bis) for public telephone channel is fully discusssed and implemented in real-time by using real-time communication processing system.
Full-duplex operation on two-wire line requires the ability to separate a receiver signal from the reflection of the transmitted signal. This is accomplished by FDM(Frequency Division Multiplexing) in which the signals in the two directions occupy different frequency bands and are separated by filtering.
The real-time communication processing system consists of TMS320C40 digital signal processor, CPU board(MC68040), DMA boards, and VME buses. Eight TMS320C40 DSP processors can be cross communicated with orther through DMA channels. Therefore it makes possible to implement the our system in parallel and multi channel mode. Using with this parallel processing capability, a calling modem receiver and answering modem receiver are implemented in parallel.
The algorithms which we implemented V.22bis for PSTN(Public Switched Telephone Network) consists of AGC, energy detect, tone detect, phase splitter, symbol timing recovery, adaptive equalizer, carrier recovery, and character converter parts.
