The performance of a hybrid slow frequency hopped direct sequence multiple frequency shift keyed (SFH/DS MFSK) communication link in the presence of partial band multitone jamming is considered. The communication signal is characterized by a DS-spread MFSK signal bandwidth that may exceed the FH slot spacing, and the signal consists of multiple M-ary symbols per DS code period. An equation for the bit error rate (BER) is developed for the signal in the presence of multitone jamming. The equation is flexible enough to allow examination of optimization of jamming strategy. It is shown that the jamming strategy may be optimized by varying the number of tones, their placement, or both. It is shown that in the presence of optimized jamming, overlapping systems are more resistant to jamming than nonoverlapping systems with equal parameters (except for the number of FH slots). It is also demonstrated that, in some cases, the addition of DS spreading to an FH system, without increasing the total system bandwidth, can significantly improve the system's resistance to partial band multitone jamming.>

The authors characterize multiple-access interference for cellular mobile networks, in which users are assumed to be Poisson-distributed in the plane and use frequency-hopped spread-spectrum signaling with a transmitter-oriented assignment of frequency-hopping patterns. Exact expressions for the bit error probabilities are derived for binary coherently demodulated systems without coding. Approximations for the packet-error probability are derived for coherent and noncoherent systems and these approximations are applied when forward-error-control coding is used. In all cases, the effects of varying interference power are accurately taken into account according to some propagation law. Numerical results are given in terms of bit-error probability for the exact case and throughput for the approximate analyses. Comparisons are made with previously derived bounds, and it is shown that these tend to be very pessimistic.>

In this paper we address the problem of combatting combined interference in spread-spectrum communication links. We consider frequency-hopped spread-spectrum systems withM-ary FSK modulation and noncoherent demodulation which employ forward-error-control coding. The interference consists of partial-band noise jamming, nonselective Rician fading, other-user interference, and thermal noise. The coding schemes which we analyze include: ReedSolomon codes (with or without diversity and error-only, erasure-only, or parallel erasure/error decoding), binary, nonbinary, and dual-kconvolutional codes with and without side information (information about the state of the channel), and concatenated schemes (Reed-Solomon outer codes with either inner detection-only block codes or inner convolutional codes). In all cases we derive 1) the minimum signal-to-jammer energy ratio required to guarantee a desirable bit error rate as a function of ρ, the fraction of the band which is jammed, when the number of interfering users is fixed; and 2) the maximum number of users that can be supported by the system as a function of ρ, when the signal-to-jammer energy ratio is fixed.