e consider the local minimum to be Mopt in each curve, arbi- trarily low Pb's can be achieved for sufficiently large values of m; for the more pow- erful codes, these larger amounts of diversity are small enough to be of practical interest. Coding Countermeasures and the factor y varies with the type of jamming according to WC partial-band noise (2.164) WC n = 1 band multitone with the definition of B in Table 2.7 extended to include B = 1 for K = 1. Of course, for smaller values of Eb/N, Mopt = 1 and the performance is based on formulas in Section 2.3.2. In Figures 2.66-2.75, we compared the performance of convolutionally coded FH/MFSK systems in worst case noise and tone jamming for 1 < K < 5. We are now in a position to extend the scope of that comparison to include optimum diversity inner codes; the results are illustrated in Figures 2.87-2.96. These graphs contain no major surprises: the more powerful codes without diversity still provide better performance with optimum diversity. Orthogonal convolutional codes continue to be relatively inade- quate, although they manage to slightly outperform uncoded systems with optimum diversity. In all of the graphs, the performance of the rate 1/2 and 1/3 dual-K convolutional codes with optimum diversity converges for low Pb's. Furthermore, these systems are consistently 3 dB better than uncoded MFSK signals with optimum diversity for small enough Pb's. These obser- vations are explained analytically later in this section. WC PARTIAL-BAND NOISE OPTIMUM DIVERSITY UNCODED DUAL - 1, RATE 1/2 CONVOLUTIONAL CODE DUAL - I, RATE 1/3 CONVOLTIONAL (7, 1/2) BINARY (7, 1/3) BINARY CONVOLUTION- CONVOLUTIONAL Figure 2.87. Comparison of performance of uncoded and several convolutionally coded FH/binary FSK systems with optimum diversity in worst case partial-band noise. With the addition of optimum diversity, the dual-1 system performance is almost identical for both code rates considered. Non-Coherent Frequency-Hopped Systems WC PARTIAL-BAND NOISE OPTIMUM DIVERSITY DUAL - 2, RATE 1/