The performance of trellis-coded FSK modulation with noncoherent detection is presented, as applicable to a frequency-hopped spread spectrum communication system or a conventional FSK system. Nonorthogonal tone spacing is considered as a parameter to control bandwidth occupancy of the hopped signal and to allow an increased number of users. Soft decision decoding with a maximum metric decoder is employed. The metrics considered are the energy metric with and without perfect jammer state information as well as a practical self-normalized metric that compensates for jamming or interference. Performance analyses for full and partial band, and both noise and multitone jammings are presented. For nonorthogonal tone spacing, the signals are correlated, and so Chernoff bounds on the pairwise error probability for energy detectors with correlated signals are presented and evaluated. These bounds supplement earlier performance estimates for trellis coded FSK. To assess the tightness of the bounds, simulations have been carried out, with results that come within 1 to 3 dB of the bounds. System performance is evaluated for 2, 4 and 8-state trellis codes with tone spacings of 1/3T, 1/2T, 2/3T and 1/T Hz.>

Frequency-hopped spread-spectrum transmission using band-efficient modulations that are phase-continuous during each hop, is presented. A range of system parameters is considered, including signaling spectrum, reception, system complexity, and performance in the presence of noise and jamming. The particular cases where the hopped modulation is minimum-shift-keying (MSK), duobinary minimum-shift-keying (DMSK), or tamed-FM (TFM), are studied in detail. Results are presented for various modulation indexes, rectangular and raised cosine pulse shapings, and a range of hop interval lengths. Sequence estimation on a hop-by-hop basis is considered. The noncoherent likelihood sequence receiver must keep all possible paths, and so the computation and complexity becomes large for system transmitting many bits per hop. Therefore, a simplified noncoherent Viterbi-like sequence estimation algorithm with reduced complexity is introduced. System performance has been evaluated in Gaussian noise, partial-band jamming and multiple-tone jamming, using bounds and a system simulation. The compact nature of the hopped spectrum, when a number of bits are transmitted per hop, offers greater spectrum utilization and the prospect of improved performance in the presence of multiple-tone jamming or interference.>