Concatenated coding techniques are applied to slow frequency-hop packet radio communications for channels with partial-band interference. Binary orthogonal signaling (e.g., binary FSK) is employed with noncoherent demodulation, Reed-Solomon codes are employed for the outer code while both block and convolutional codes are considered for the inner code. Hard-decision and soft decision decoding methods are considered for the inner codes. A method is devised for estimating the reliability of the outer Reed-Solomon code symbols, and this estimate is used to determine which code symbols should be erased. Comparisons are made between the performance of concatenated codes and the performance of Reed-Solomon codes alone.

It is shown that the method presented by C. Schlegel (see ibid., vol.37, no.3, p.627-34, May 1991) for evaluating the distance spectra of trellis codes on channels with intersymbol interference is incorrect. A counterexample is presented along with comments on the feasibility of correcting the method.>

The statistical dependence of hits due to multiple-access interference in an asynchronous slow-frequency-hop packet radio network in which the radios employ memoryless hopping patterns is described. Models in which hits are conditionally independent given the number of interfering packets are investigated. It is shown that if the conditional probability of a hit is chosen appropriately, the distribution function for the number of hits in a packet for these models can be used to compute upper and lower bounds on the true distribution function for the number of hits. Conditions are described for which these models can be used to compute upper and lower bounds on the codeword and packet error probabilities. It is shown that if the ratio of the number of interfering packets to the number of frequency slots is held constant, hits in the asynchronous frequency-hop network are asymptotically independent in the limit as the number of frequency slots increases. This result suggests that when the number of frequency slots is large, error probabilities can be closely approximated by using the distribution for the number of hits that results from assuming that hits are independent.>

The authors demonstrate that contrary to the claim made in the above named work (ibid., vol.36, Jun., p.720-3, 1988), the sequence of hits in an asynchronous frequency hop multiple-access system is not a Markov process. Comments of the use of a model in which the hits are independent are also given.>