rtial-band jammer where N1 = QJ/Wss = QN1 (2.285) Nq0q=2,3,..,Q. D(J) = 1 + (2.286) Note that as Q 8, we have l 0 and thus (2.287) Since in general D(J) VI 1, this shows that the asymptotically worst noise jammer power distribution is the two-level partial-band jammer where the fraction of the sub-band that is jammed approaches zero. The above example points out the important fact that in coding systems the choice of metric is crucial even in Rayleigh fading channels where the broadband jammer is worst in the uncoded case. Here, without jammer state information, the usual energy metric which is optimum for a broadband noise jammer case gives very poor performance for the worst jammer noise power distribution. 2.6 WORST NOISE JAMMER DISTRIBUTION-SLOW FADING NON-UNIFORM CHANNEL Based on the work of Avidor [25] a consideration now follows of the non- uniform fading channel where there is Rayleigh fading that can be dif- ferent for each of the Q sub-bands. In particular, let the average energy of an FH/MFSK symbol transmitted in the q-th sub-band have average Worst Noise Jammer Distribution-Slov Fading Non-Uniform Channel energy Eq = a E (2.288) q=1,2,...,Q. Also assume that the noise jammer's power is non-uniformly attenuated across the band. For the q-th sub-band the jammer's single-sided noise power spectral density is constant at Nq=BqJq (2.289) where as before the jammer power distribution J = satisfies the constraint given by (2.242). The channel parameters A1, a2, aq and B1, B2, , BQ are fixed throughout this section. Since the channel is no longer uniform, assume the frequency hopping is also non-uniform across the total spread-spectrum frequency band. Certainly if Eq = 0, it does not make sense to hop into the q-th sub-band. Thus we let Pq be the probability that the FH/MFSK signal hops into the q-th sub-band and define the hopping probability vector (2.290) The non-uniform fading channel described here might model the HF channel where A1,A2, aq describe the propagation conditions across the HF band (3 MHz t