## Appendix C. Probabilities and Stochastic Processes

Communication systems, particularly computer networks, often encounter random arrivals of tasks as packets. Such systems require analysis using the theory of probabilities, as seen in various chapters. This appendix reviews principles of probability theory, random variables, and random processes.

### C.1 Probability Theory

Let’s first consider a random experiment, such as producing random logic 0s and 1s. The *sample space* of the experiment, usually denoted by the symbol *S*, consists of the set of all possible *outcomes*, indicated by *w*. In this case, for integers 0 and 1, the sample space is *S* = {0, 1}. We define an *event*, A, to be a subset of sample space, which may consist of any number of sample ...