Concepts of Integrated Adaptive Data Transmission Systems

Abstract

Telemetry systems require the transmission of information in analog, sampled, and digital forms. There also are requirements for spectrum conservation, for minimum spurious transmission outside the assigned band, and for highest flexibility in multiplexing and in accepting a wide range of sensors. The paper describes the conceptual design of an advanced information transmission system that operates basically in the sampled mode, but that can accept analog inputs through an information compressing sampler or digital inputs by taking one sample of each input bit and making binary decisions in the receiver. The system uses three different encoding processes in an integrated manner. The first encoding process is performed by a redundancy reducing computer-like subsystem called the contractive encoder. Its purpose is to eliminate unnecessary samples while keeping the essential samples at their correct place on the time scale. Repetition of already transmitted samples. or the insertion of samples from other channels will fill the space of samples that have been removed. The second encoding process is performed by a distributive encoder. The purpose of this part of the information processor is the protection of the information against sudden pulsive disturbances. The distributive encoder spreads the information content of each sample over tens to hundreds of other samples in an ordered manner. If, during transmission, one sample or a group of samples is heavily mutilated by pulsive disturbances, the corresponding decoder in the receiver will recover most of the information of these mutilated samples from the other undisturbed samples while spreading the energy of the pulsive disturbances over all samples so that it contributes only a negligibly small error to any one of them. The third encoding process is performed by the modulative encoder. This device has the task of shaping the samples that are produced by the distributive encoder into bandlimited waveforms so that a noise-like, bandlimited composite transmission signal with a uniform spectral distribution is finally fed into the communication channel. Many adaptive features and the option to use a return channel for repetitions of blocks of samples give the system high stability, high efficiency, and low error ratio.