Design and implementation of the Interactive Communications Simulator (ICS)

This report describes the development and capabilities of a fairly comprehensive system for the digital simulation of a wide variety of point-to-point digital communication systems. This system is called the Interactive Communications Simulator (ICS). The ICS is a flexible, graphics oriented, high speed, and highly interactive hardware/software system consisting of a PDP 11-40 minicomputer acting as host to a fast peripheral array processor, the Floating Point Systems AP-120B. Its modeling structure is the classical breakout of the various generic signal processing functions in any communication link, from source to sink. The signal processing functions are predominantly modeled in terms of their complex envelope representations for uniformity, ease, and accuracy of analyses. It is fully supported by an extensive graphics support package and many powerful analysis subroutines, to facilitate user-interactions, analyses, and output displays. The modeling and simulation tasks are optimally partitioned between the PDP 11/40 host and the AP-120B peripheral array processor to ensure ease-of-use and highly efficient manipulations. The ICS also features realistic channel models, in addition to the analytically expedient Additive White Gaussian Noise (AWGN) channel, so that the performance and behavior of all modeled transceiver functions can be more exactly assessed and specified. All simulation modules are written in the AP Assembly Language, and the system software, graphics support package and analysis subroutines are written in DEC FORTRAN IV.