Modeling Broadcast Teletext Systems for Analysis and Computer Simulation Studies

An isomorphism is derived between a typical bandpass broadcast television system to be used in transmitting teletext data and its complex baseband equivalent representation for use in analysis and computer simulations. The distortions introduced by a multipath channel are discussed. The complex noise process is modeled by a mixture of Gaussian and impulsive noise, and the parameters of the noise model are derived. The video signal-to-noise ratio SNRTVis related to other parameters such as the input noise variance, output noise power, and the carrier-to-noise density ratio. A complete simulation model for broadcast television transmission and reception is shown in block diagram form. The remaining components of the computer simulation model are briefly discussed and references given. These include topics such as amplitude control, computer generation of ensembles of complex impulse responses, simulation of synchronous, quasi-synchronous and envelope detectors, bit slicers, bit synchronizers, error-correcting codes, estimation of error statistics and bit error rates, and adaptive equalization. Validation is also briefly noted with references. Several examples of simulation results are given. Some of the implementation details, simulation results, and a flow diagram of the simulation program are provided. This teletext computer simulation model appears to be the most complete one created to this time and has been used extensively in performance analyses to evaluate new designs and gain insights into design improvements.