Comtron: a tool for the simulation of communication systems

The simulation of communication systems is of fundamental importance for engineering and economical purposes, Authe moment there am many tools that can simulate many aspects of communication systems but their use is often very complex. In this work a relatively simple metalanguage is described, which is particularly suited for the simulation of this kind of systems. The structure of this language is essentially´ descriptive and not procedural. The user describes the colmuruication @ystcrri defining first of all a sequence of blocks. The user´s file. then, is sent to a parser using a clasisical.Top-down predictive parsing algorithm that provides some additional features to avoid recursion since it is intended for use on PC type HW platforms which exhibit relative, limitations in stack allocation. The fundamental data processing unit is the block, which is seen as a black-box with an input and an output poM to insert and extract data. The functionalities performed by the blocks am of different kinds. ~ The source block, is used to create a data flow representing a message to be tted with a given probability. ~ The coder block receives in input a bit stream (the message) and performs some block code or convolutional code manipulation. The output of the block is the coded message. ~ The modulator block presents some -additional difficulties since in the real world output of a modulator is an analog signal. In our tool this signal is sampled at the appropriate frequency fixed in agmement with the Nyquist´s rale.