L- BAND NOISE E6/NJ,dB Figure 2.100. Same as Figure 2.99, except for (7,1) Odenwalder code; this is the only code of those considered in this section which is powerful enough by itself (mopt = 1) to combat worst case non-adaptive jamming. In the noise case, the code is insen- sitive to p (Pwc is not much worse than p=1), = but performance is about 1.5 dB bet- ter in multitone jamming. (7, 1/2) 4 -ARY - CONVOLUTIONAL CODE WC n= I BAND MULTITONE WC PARTIAL- BAND NOISE Eb/N, dB Figure 2.101. Effect of optimum diversity on FH/4-ary FSK system with Trumpis (7,1) code in worst case noise and multitone jamming. Optimum diversity provides a moderate improvement: e.g., it cuts the degradation due to worst case partial-band noise approximately in half. Non-Coherent Frequency-Hopped Systems DUAL-4, RATE 1/2 CONVOLUTIONAL CODE WC n= I BAND MULTITONE WC PARTIAL BAND NOISE Eb/Ns, dB Figure 2.102. For FH/16-ary FSK system with dual-4, rate 1/2 convolutional code, diversity provides a major performance improvement; for example, optimum diver- sity recovers most of the degradation inflicted by worst case partial-band noise. minimum Eb/N1 to achieve this Pb in any kind of non-adaptive jamming. Recall from Table 2.12 that without diversity, the Odenwalder (7,1) binary convolutional code gained this distinction with EbIN1 = 10.38 dB; with the addition of optimum diversity, the Trumpis (7,1) 4-ary convolutional code is the overall winner with Eb/N, = 9.43 dB, an improvement of almost 1 dB over the best convolutional code alone and nearly 5 dB better than optimum diversity alone (E/N, = 14.21 dB at K = 2). Not surprisingly, Mopt is much smaller for the concatenated convolutionally coded systems (we already noted that the (7,1) binary convolutional code has Mopt = 1). In fact, Mopt is small enough that the overall code rate R = R'Imopt for the concatenated systems with the exception of the M-ary orthogonal codes is approximately double that of the uncoded systems with optimum diversity for a given K. Table 2.16 reiterates the close per