ion to be answered is whether these codes are powerful enough for this type of non-stationary, non-Gaussian channel. Table 2.15 Comparison of several Reed-Solomon outer codes concatenated with binary convolutional inner codes and FH/MFSK signalling in worst case partial-band noise and multitone jamming. Inner codes consist of (7,1) Oldenwalder code for K = log2M = 1, and (7, 1/) and (7,1) Trumpis codes for K = 2 and K = 3 respectively. Eb/N,, dB for Pb = 10-5 Noise Multitone RS Code RS Code Inner Code K = 1 K = 3 K = 3 127,63 1.30 X 10-1 1.970 X 10-2 11.74 10.23 10.81 255,191 6.51 X 10-2 8.379 X 10-3 10.16 511,447 3.33 X 10-2 3.756 X 10-3 1023,959 1.72 X 10-2 1.733 X 10-3 Coding Countermeasures Suppose we add diversity to the codes analyzed above; we will employ the usual scheme of transmitting each M-ary symbol as m chips on separate hops. Effectively, we will have a concatenated coding system with an m-fold rep- etition code as the innermost code. We will then determine the optimum diversity Mopt for a given coded FH/MFSK structure in worst case partial- band noise or multitone jamming. If the outer code has sufficient redundancy and is well matched to the jamming environment, we should find that Mopt = 1. If instead we discover that Mopt is significantly larger, the implication is that diversity is required to boost the capabilities of the given code. As in Table 4.3, Volume I, an m-fold repetition code has G(D) - M D " (2.158) for an M-ary orthogonal channel. As a result, all of the performance expres- sions in the previous section remain valid, except that D is replaced by Dm for m-diversity. That is, (2.130) and (2.131) become noise jamming (2.159) multitone jamming. Aside from this change of arguments, the functional form of G() for the various codes in (2.146)-(2.151) remains the same. Depending on the type of jamming, D is computed from (2.132), (2.134), (2.138), or (2.139), with EJN, related to Eb/N, by the overall code rate R. Since the diversity inner- most code rate is 1/m, it is convenient to use (2