] R. H. Barker, "Synchronising arrangements for pulse code systems," U.S. Patent 2 721 318, Oct. 18,1955 (filed in U.S. Feb 16, 1953; in Great Britain, Feb. 25, 1952). [228] S. O. Rice, "Communication in the presence of noise; probability of error for two encoding schemes," Bell System. Tech J., Jan. 1950. [229] R. M. Fano, "Signal-to-noise ratio in correlation detectors," M.I.T. Res. Lab. Electron., Tech. Rep. 186, Feb. 19, 1951 (PB 110543, ATI 103043). [230] Y. W. Lee and J.B. Wiesner, "Correlation functions and communication appli- cations," Electronics, June 1950, pp. 86-92. [231] A. Hodges, Alan Turing: The Enigma, New York: Simon & Schuster, 1983. [232] D. Kahn, "Cryptology and the origins of spread spectrum," IEEE Spectrum, vol. 21, no. 9, pp. 70-80, September 1984. Chapter Chapter 3 BASIC CONCEPTS AND SYSTEM MODELS This chapter introduces the basic design approach for anti-jam communi- cations and presents two simple idealized examples of such systems, specif- ically coherent direct-sequence spread, binary phase-shift-keying (DS/ BPSK), and non-coherent frequency-hopped binary frequency-shift-keying (FH/BFSK) systems opposed by various jammer waveforms. Ideal signal parameter acquisition and synchronization is assumed throughout this chap- ter. Ground rules for system performance analysis are specified by stating assumptions regarding jammers and anti-jam systems along with definitions of the fundamental system parameters used throughout this three-volume work. Because coding and interleaving are extremely important in anti-jam system design, the impact of these techniques is illustrated with examples. The purpose of this chapter is to exemplify basic concepts with simple exam- ples which serve as an introduction to the more advanced material in Part 1, Chapter 4, and Part 2, Chapters 1 and 2. The material in this and the previ- ously mentioned chapters is based in part on the works of Jacobs and Viterbi [1], Houston [2], Scholtz [3], Viterbi [4], Clark and Cain [5], and Pickholtz et al. [6]. 3.1 DESIGN A