COMSL: a communication system simulation language

In recent years, computer simulation has come to play an important role in the design of communication systems. Such systems frequently cannot be classified as either purely continuous or as purely discrete but are, instead, a combination of both continuous and discrete subsystems. The simulation of such hybrid systems cannot readily be carried out either in a discrete simulation language such as GPSS or in a continuous simulation language such as CSMP. As a consequence, most simulation models of communication systems are written in some general purpose higher level language, e.g., FORTRAN, ALGOL or PL-1. A notable exception to this general rule is BLODI and BLODIB described in Reference 4. The simulation of even moderately complicated communication systems in a general purpose language poses several major problems. First of all, the simulation model tends to be time consuming to write and debug, difficult to modify once written, and, unless considerable care is taken, requires an inordinate amount of time to execute. However, the most important weakness of a communication system simulation model written in a higher level language is that the model usually is written by someone with a limited knowledge of the actual system being simulated. As a consequence, there frequently exists the possibility that the simulation model differs in some significant, but unnoticed, respect from the actual system. Primarily to avoid this problem, a new simulation language, COMSL, is described which facilitates the simulation of a wide variety of communication systems.