 Chapter 5 and Part 2, Chapter 1. Thus, this result seems to say that, regardless of the type of jammer, the performance of DS/BPSK is essentially the same as for the baseline jammer, namely the broadband Gaussian noise jammer. This is not true, as shown in the next example. 3.4.2 Pulse Jammer Suppose that the jammer transmits broadband noise as in the previous sec- tion, but for only a fraction of the time with larger power. In particular, let p be the fraction of time the jammer is "on" and Nj/p be the jammer power spectral density where N is given by (3.8). Note that the time-averaged jam- mer power is assumed to be J, although the actual power during a jamming pulse duration is J/p. Also assume that the jammer pulse duration is greater than Tb, the data bit time, and that a particular transmitted data bit either encounters a channel with jammer "on" with probability p or jammer "off" with probability 1 - p. We ignore the cases where the jammer might be "on" only a fraction of the transmitted data bit time. We model the pulse jammer case as shown in Figure 3.6 with the detec- tor output now given as r = dVE, + Zn (3.40) Uncoded Direct-Sequence Spread Binary Phase-Shift-Keying where n is the jammer noise term which is a Gaussian random variable with zero mean and variance Nj(2p). Here Z is a random variable independent of n that has probability, Pr{Z = 1} = p Pr{Z = 0} = 1 - p. (3.41) The random variable Z specifies whether or not the jammer is "on" during a particular T data bit time interval when one BPSK signal is transmitted. The bit error probability is then P,=Pr{Zn > VEB} + r{Zn>VEbZ=0}Pr{Z =0} Pr{n > VEb}p (3.42) where with jammer pulse "off" Pr|Zn>VE}|Z=0}=0 = (3.43) This ignores the effects of noise and assumes the jammer signal "on" error term is much larger than the jammer signal "off" error term. Figure 3.7 shows values of Pb versus EIN = N/(J/S) for various values of p, the fraction of time the jammer pulse is on with power J/p. Note that the value of p that maximizes the bit error probability, Pb