nt 8 Type of Jammer K = 4 K = 5 Broadband Noise .5000 1.0000 1.5000 2.0000 2.5000 Partial-Band Noise .2500 .5000 .7500 1.0000 1.2500 Independent Multitone .3679 .5495 .5760 .5242 .4379 n = 1 Band Multitone .3679 .4631 .4493 .3839 .3014 (Exact) n = 2 Band Multitone .3232 .5835 .6379 .5790 .4734 n = M Band Multitone .3232 .6465 .9697 1.2929 1.6162 Coding Countermeasures tive than independent multitone jamming. The difference now is that the use of a detection metric that can make an error only if all m diversity trans- missions are jammed (perfect side information assumption) forces the jammer to use a much larger value of p; these values, shown in Table 2.11, are based on the optimum values of a and S shown in Table 2.9 and (2.115). Note that the probability that k slots in an M-ary are jammed is simply A relevant parameter is the likelihood that one slot in an M-ary band is jammed relative to the probability that two or more slots are jammed: (2127 Mp(1 - p)M-1 In the absence of diversity, P1 >> 1; with optimum diversity, Table 2.11 shows that P1 ~ 1. This means that a jammed band will often contain two or more jamming tones, which is different from, and apparently a less efficient use of available jamming power than the n = 1 band multitone structure, for which P1 is by definition infinite. Table 2.10 also reiterates the relative impotence of n = M band multitone jamming. All of these observations are illustrated graphically in Figures 2.62-2.64. Note that as indicated in Figure 2.64, the optimum diversity m Mopt varies with the type of jamming for a given K and EIN, Which raises an interesting point: with the exception of independent multitone jamming (refer to (2.124)), all of the remaining jammers have Mopt = SEb/N . (2.128) Now we know from (2.126) that a larger 8 ensures better performance for a given EbIN But (2.128) reminds us that this benefit is balanced by increased system complexity due to the need for more diversity. In designing an FH/MFSK system with diversity, it is prudent to select parameters th