Novel Techniques for Improved Performance of Dynamic Differential Frequency Hopping Under Partial Band Jamming

Differential Frequency Hopping (DFH) is a spread-spectrum communication technique in which the current hop frequency is determined by a Frequency Transfer Function (FTF) that relies only upon the current data symbol and previous hop frequency. This dissertation proposes two methods invented by the author which will increase DFH system resiliency to noise or deliberate jamming and improve system error performance. The first method provides a DFH transmitter enhancement for hop frequency assignment randomization which improves over earlier efforts of other authors by dynamically expanding the signal space for a single user for improved jammer resiliency without increasing encoder complexity, scales easily while maintaining its randomization characteristics, dynamically assigns random hop frequencies to encoder states every hop period, retains an underlying Error Correction Code (ECC) encoder structure for improved error performance, is easy to understand, and provided in sufficient detail so as to be reproducible by others. The second method provides a DFH receiver enhancement for missed hop error correction which improves over earlier efforts of other authors in that it operates off of the received sequence only, tracks piece-wise solution convergence as a means to remain computationally efficient over the length of a received message, can work in cascade with other error correction techniques (e.g., Viterbi decoding) for improved overall information error performance in an end-end system, it is simple to implement, easy to follow, and described in sufficient detail so as to be reproduceable by others. These improvement methods are combined and presented in an end-end system which will be evaluated under the presence of partial band jamming. Overall hop error rate and bit error rate performance will be evaluated for several different DFH encoder models and jamming conditions. It will be shown that with the selection of an appropriate Error Correcting Code (ECC) with sufficiently large free distance for encoder state generation, improved error performance can be realized through the cooperative effects of random hopping, hop error correction, and bit error correction