ssible, but their performance does not sig- nificantly differ from that of these two basic ones. Throughout this work, the stored reference systems are assumed and in this chapter two simple exam- ples are studied. The assumption that the jammer does not know which subset of the many possible signal coordinates the signal uses at any given time is generally achieved by having identical synchronized pseudorandom (PN) sequence generators at both the transmitter and receiver. These continuously running PN generators are used by the transmitter and receiver to choose signal coor- dinates that continuously change in time. This PN generator pair must use a common key without which they would not work in unison. Throughout this book, we assume that the PN generator key is available to the trans- mitter and intended receiver, but not to the jammer. This, in fact, is the only information not available to the jammer. Our basic assumption concerning Models and Fundamental Parameters the jammer is: THE JAMMER HAS COMPLETE KNOWLEDGE OF THE SPREAD-SPECTRUM SYSTEM DESIGN EXCEPT HE DOES NOT HAVE THE KEY TO THE PSEUDORANDOM SEQUENCE GENERATORS. Indeed, the jammer can have identical copies available (stolen perhaps) of the spread-spectrum transmitter and receiver, and certainly can try vari- ous keys; but without knowledge of the actual key used by the spread-spec- trum system, the jammer cannot generate the same pseudorandom numbers used by the spread-spectrum transmitter and receiver. Chapter 5 of Part 1 reviews the properties and design of pseudorandom number generators. 3.2 MODELS AND FUNDAMENTAL PARAMETERS The basic system is shown in Figure 3.1 where the following system para- meters are fixed: Wss = total spread - spectrum signal bandwidth available Rb = data rate in bits per second S = signal power at input to the intended receiver (3.2) J = jammer power TRANSMIT TER RECEIVER Wss = BANDWIDTH Rb = BIT RATE (BITS/SEC) S = POWER = -TO-SIGNAI - POWER RATIO N , Eb = J/S JAMMER J = JAMMER POWER Figure 2.1. System overview. Basic