OGONAL CONVOLUTIONAL UNCODED, OPTIMUM DIVERSITY DUAL - 3, RATE 1/2 CONVOLUTIONAL CODE DUAL-3, RATE 1/3 CONVOLUTIONAL (7, 1/3) 8-ARY CONVOLUTION- AL CODE Eb/Nj, dB Figure 2.73. Same as Figure 2.68 for multitone jamming, which is more effective than partial-band noise. However, relative performance of codes is essentially unchanged, with Trumpis' (7,1) code on top. Coding Countermeasures WCn=1 BAND MULTITONE UNCODED, OPTIMUM DIVERSITY ORTHOGONAL CONVOLUTIONAL CODE DUAL - 4, RATE 1/2 2010-3 CONVOLUTIONAL CODE DUAL - 4, RATE 1/3 CONVOLUTIONAL Eb/N, dB Figure 2.74. Same as Figure 2.69, with worst case multitone jamming proving more effective than partial-band noise again (this is generally true for smaller Pb's and K = 2). WC n= I BAND MULTITONE UNCODED, OPTIMUM DIVERSITY ORTHOGONAL CONVOLUTIONAL CODE DUAL - -5, RATE 1/2 CONVOLUTIONAL CODE DUAL- -5, RATE 1/3 CONVOLUTIONAL CODE Eb/Ns, dB Figure 2.75. Same as Figure 2.70, except jamming is worst case n = 1 band multi- tone. Performance of dual-5, rate 1/3 code is about 6.5 dB worse than in partial-band noise, and 1.5 dB worse than for K = 4 in multitone jamming at Pb = 10-5. Non-Coherent Frequency-Hopped Systems for a given combination of FH/MFSK signals and jamming. No attempt has been made to similarly optimize the convolutional code rates. We will exam- ine this issue later in connection with block codes, particularly Reed- Solomon codes. Some specific observations about the relative effectiveness of the various convolutional codes in worst case jamming are included in the commentaries with Figures 2.66-2.75. Overall, the Odenwalder optimum binary convolu- tional codes and the Trumpis optimum 4-ary and 8-ary convolutional codes are a significant improvement over uncoded FH/MFSK with optimum diver- sity. At the other extreme, orthogonal convolutional coding is quite vulner- able to worst case jamming, especially for smaller values of K; in fact, for lower Ph's the performance curves exhibit the inverse linear dependence characteristic of uncoded signalling. In between