 distribution of Aj; namely, (1.130) Since, on the average, the fraction p of the total number of detection inter- vals is jammed, the average bit error probability over all detection intervals (jammed and unjammed) is given by (1.57) where (1.131) represents the average bit error probability of duobinary QPSK in the absence of jamming. Note that the average bit error probability perfor- mance of duobinary, as given by [7, Eq. (4.114)], agrees only with the lead- ing term of (1.131) and is thus only asymptotically correct as Eb/No approaches infinity. The symbol error probability of duobinary QPSK is, as for any QPSK sys- tem, the probability that either the in-phase or the quadrature bit is in error. Thus, (1.132) which when averaged over all symbols (jammed and unjammed) gives the result in (1.24) where Ps, is given by (1.17) together with now (1.122) and (1.133) Note that the first two terms of (1.133) resemble the functional form of the average symbol error probability expression for QASK-16 as in (1.51). There, however, E'b is related to the true bit energy Eb by E'b = (2/5). Eb. Figure 1.19 is a typical plot of Pb as evaluated from (1.57) versus p, with Eb/N as a parameter and Eb/No = 20 dB. One again observes that, by fixing Eb/No and E/N, there exists a value of p which maximizes Pb and thus rep- resents the worst case multitone jammer situation. Figure 1.20 is a plot of Performance of FH/QPR in the Presence of Partial-Band Multitone Jamming Figure 1.19. Pb versus p for FH/QPR in tone jamming with E/ = 20 dB. worst case p versus EIN, with Eb/No as a parameter. Figure 1.21 illustrates the corresponding plot of Phmax versus Eb/N, with Eb/No fixed. As was true for the FH/QPSK and FH/QASK modulations considered previously, it is of interest to study the limiting behavior of FH/QPR in the presence of multitone jamming as the Gaussian noise (e.g., No) goes to zero. (1.134) Then, for FH/QPR, we obtain the following results: Eg/No->00 lim Pbs (1.135) Coherent Modulation Techniques Ep=4 dB ED=9da Eb/Ny, dB Figure 