Multi-level data transmission over mobile radio channels

Describes how the transparent tone in band technique (TTIB) can be optimally used for data transmission. This involves baseband spectral manipulations most effectively performed on a DSP device to generate a system which provides the required coherent carrier reference and also symbol timing information, independent of the modulation type. Results have previously been presented which demonstrated the feasibility of using TTIB based data transmission. These results were generated using a standard V29 telephone modem as the modulation source, with carrier recovery and bit timing synchronisation implemented by the modem. Significant improvements in performance have been made by utilising the full capabilities of the TTIB technique. The hardware implementation has also been greatly simplified to a single TMS 320C25 DSP device for both modulator and demodulator