ER INTERLEAVER MODULATOR SPREADER PROBE-LONG-TERM CHANNEL JAMMER STATE Noise INFORMATION Fading Jamming MEASUREMENT-LONG-TERM DECODER DEINTERLEAVER DEMODULATOR DESPREADER Figure 1.6. AJ system overview. Coherent Direct-Sequence Systems RATE = 1/3, K = 41, SEQUENTIAL RATE = 1/2, K = 41, SEQUENTIAL RATE 1/2, K = 7, VITERBI, SOFT DECISION RATE 1/3, K = 7, VITERBI, SOFT DECISION RATE 1/2, K=7 VITERBI, HARD DECISION RATE 1/3, K = 7, VITERBI, HARD DECISION UNCODED Eb/No Figure 1.7. A comparison of the bit error probability performances of rate 1/2 and 1/3, hard and soft decision Viterbi and sequential decoders. These curves serve as basic reference coded bit error probabilities from which we can derive coded performance for all other jamming channels. The only difference in the various jamming cases will be in the value of D and R0 for each coded symbol to equivalent jammer noise ratio, Eb/N1. 1.5.2 Jamming Channels For the constant power jammer, regardless of the waveform used by the jam- mer, the bit error probability was bounded by the bit error probability of coherent BPSK modulation with the additive white Gaussian noise channel where No = N, the equivalent jammer noise density. This assumes the Central Limit Theorem applies and in the case of CW jammers the system uses the same data in the inphase and quadrature coordinates of a direct- sequence spread QPSK modulation. In this case, the results for the additive white Gaussian noise channel shown in Figure 1.7 apply where Eb/No is replaced by Eb/N1. Standard Codes and Cutoff Rates The only remaining case of interest is when there is a pulse jammer that transmits pulses with power J/p for p fraction of the time. When the pulse is on, assume the jammer waveform is equivalent to additive white Gaussian noise with single-sided spectral density No = N/p. For pulse jamming, values of D are shown in Table 4.1 of Chapter 4, Part 1, for various cases of hard and soft decision metrics, which may or may not include jammer state information. These are all shown as a function 