GENERALIZED LIKELIHOOD-RATIO DETECTION OF MULTIPLE-HOP FREQUENCY-HOPPING SIGNALS

A noncoherent, soft-decision combining processor for the multiple-hop detection of frequency-hopping signals is developed, based on a genera lised likelihood-ratio test argument. Hop rate, hop transition times, and the set of candidate carrier frequencies are assumed to be known t hroughout. The proposed receiver has a simple structure: it consists o f a bank of per-hop envelope detectors, a per-hop 'select-the-maximum' operation, a soft-decision accumulator over hops, and a final thresho ld comparison. For a large number of observed signal hops, this receiv er is analysed on the basis of a Gaussian, central-limit theorem type of argument for the decision statistic. A simple formula that relates the detection probability, the false alarm probability, and the signal -to-noise ratio is derived and found adequate for performance purposes . This line of analysis is well supported by extensive simulation. It is shown analytically that the performance of the soft-decision receiv er is better than the noncoherent hard-decision combining receiver, wh ich is typically referred to in the literature as the 'multiple-hop ma ximum-likelihood receiver'.