dth" of the transmit- ted signal. The one-sided noise spectral density is N1 = J/W ss. Since an equivalent white Gaussian noise process is encountered in all parts of the total spread-spectrum band, the bit error probability for the uncoded FH/BFSK system of Figure 3.23 is the same as that for conventional BFSK in white Gaussian noise, namely (3.76) where Eb/N1 is still given by (3.39). This is the baseline performance of the FH/BFSK system. ENERGY DETECTOR FREQUENCY FREQUENCY MODULATION DEHOP ENERGY DETECTOR wotson GENERATOR GENERATOR TRANSMITTER CHANNEL RECEIVER Figure 3.23. Uncoded FH/BFSK system. Basic Concepts and System Models 3.6.2 Partial-Band Noise Jammer Next, consider the impact of partial-band noise jamming where the jammer transmits noise over a fraction p of the total spread-spectrum signal band. Denoting the jammed frequency band by W, then p is given by (3.10) and in the jammed part of the band, the equivalent single-sided noise spectral density is given by (3.11). Assume that W1 is large compared to the bandwidth of the unhopped BFSK signal and the effects of the signal hopping onto the edge of this band are negligible. That is, ignore the possibility that when a signal is sent it is frequency-hopped to the edge where only part of the instantaneous band of the signal is jammed. This assumes either a signal is hopped into the jammed band or not. In addition, the jammer is allowed to change the band it is jam- ming and SO the transmitter and receiver never known a priori which fre- quency range is being jammed. We again introduce the jammer state parameter Z for each T interval where now signal in jammed band (3.77) signal not in jammed band with probability distribution as in (3.41). The bit error probability is then given by Pb=Pr{e+>e_d=-1} = : Pr{e+ > e d - 1, = Z = = 1}Pr{Z = 1} + Pr{e+ > e_d = -1, Z = 0} (3.78) where there are no errors when the signal hops out of the jammed band. Figure 3.24 illustrates the bit error probability for various values of p. The value of p that maximizes Pb is ea