 R > Rh. For each received M-ary chip, after the FH carrier has been demodulated, the received signal is input to M non-coherent detectors which measure the energy at each of the possible tone frequencies over the chip duration 1/Rc (refer to Figure 2.1). To ensure that none of the signal energy is detected by the M - 1 energy detectors at the untransmitted frequencies, the spacing between adjacent FH slots (within an M-ary band) must be an integer mul- tiple of Rc; if the minimum separation is used, then the number of available frequencies (2.56) decreases with the amount of diversity m per M-ary symbol¹ (see Figure 2.3). In addition to the M detected energies per chip, the receiver may have some channel state side information available to aid the data decision process [8]. We will assume that the receiver knows with certainty whether each hop is jammed or not. One way to derive this information in practice is to imple- ment automatic gain control (AGC) in the receiver, which may be monitored to determine whether jamming power is corrupting a given hop [2,p.288]. However, we will instead use an approach suggested by trumpis [7]; since only one of the energy detector outputs will be high2 on a given chip trans- mission in the absence of jamming, we will declare a chip to be jammed when two or more energy detector outputs are high. Since the channel statistics can change at the pleasure of the jammer, any decision metric will be suboptimum for some form of jamming. For sim- plicity, we will use the following procedure based on the soft decision energy detector outputs for the M tones and m diversity transmissions relevant to a given M-ary symbol, along with the corresponding jamming state side infor- mation. If any of the m chips is not jammed, an error-free M-ary decision can be made; otherwise, select the largest of the metrics (2.57) Superscript(1)Viterbi and Jacobs [2] and others prefer the parameter L = m/K, which is the diversity per bit. Actually, since we are neglecting receiver thermal noise, the other M 