g Countermeasures Table 2.8 Parameters associated with performance of FH/MFSK signals with diversity in worst case band multitone jamming. Yo, dB 2.395 1.1381 2.395 .3232 1.072 .6305 1.072 .5835 1.745 .5784 1.163 .6361 2.395 .5691 1.197 .6465 .5767 .6379 .4723 .7790 1.169 .4237 .8682 1.488 .4009 .9177 1.804 .3894 .9446 2.106 .3832 .9601 2.394 .3794 .9697 .6354 1.070 .5790 .5023 .7324 .4297 .8560 .3844 .9571 .3541 1.0388 1.064 .3335 1.1031 1.213 .3193 1.1523 1.827 .2933 1.2545 2.394 .2845 1.2929 -1.12 .7771 1.376 .4734 2.395 .2276 1.6162 -2.08 that Mopt does not vary monotonically with K. Also, the best performance with optimum diversity is realized when K = 3, for the selected case n = 2 and Eb/N, = 13 dB; in fact, it will be shown below that this observation true whenever EIN, is large enough, and it extends to the n = 3 and 4 cases as well. For the special case n = M, (2.110) reduces to F = min (2.112) which implies that for n = M, B is inversely proportional to K in (2.111); consequently, the performance improves with K for n = M as shown in Figure 2.54. Also, (2.112) reveals that the worst case jamming parameter a0 is independent of K under this condition, an observation that is reinforced in Table 2.8. Non-Coherent Frequency-Hopped Systems E6/IN = 9 dB n = M DIVERSITY m CHIPS/SYMBOL Figure 2.54. Special case of band multitone jamming where n = M, i.e., every sym- bol of a jammed M-ary band contains a jamming tone. For the record, the perfor- mance improves with K; however, this is a relatively ineffective jamming strategy which would probably not be used in practice. Based on (2.111), we can define the optimum diversity condition: P.S. where Mopt = SEb/Nj awc = ao (2.113) provided SO that Mopt 1. We must also verify that we are not in the saturation region: that is, (2.114) 85 <1. The validity of this condition is demonstrated in Table 2.8, which also lists values of 8 and Yo. We observed in connection with Figure 2.52 that the performance for arbi- trary m and fixed K improves with n, since Table 2.8 shows 