Coding for Frequency-Hopped Spread-Spectrum Channels With Partial-Band Interference

141 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.The performance of codes on frequency-hopped spread-spectrum channels with partial-band interference is investigated. The asymptotic performance of codes is measured by the channel capacity and the random coding exponent. The performance of specific codes is measured by the bit error probability. The channel models we consider are quite general and include channels with unknown parameters, channels which change with time, and channels with memory. These models are applicable to frequency-hopped spread-spectrum communication systems as well as to several other communication systems.We formulate the problem of communicating over channels with unknown transition probabilities (i.e. communicating over channels with jamming) as a game theory problem with payoff function being the mutual information between the channel input and the channel output. Under certain restrictions it is shown that memoryless coding and jamming strategies are simultaneously optimal strategies. Next we develop simple, yet accurate, models for many channels with memory that arise in practice. The channel statistics are constant for blocks of symbols of fixed length. The receiver is said to have side information if it can determine the channel statistics for each block of symbols transmitted. We determine the capacity, cutoff rate, and random coding exponent for these channels. The capacity without side information is an increasing function of the memory length while the cutoff rate is a decreasing function of the memory length. We show that, for channels with memory and side information random-error correcting codes with interleaving and burst-error correcting codes have comparable performance, while for channels without side information random-error correcting codes with interleaving are inferior to burst-error correcting codes. As a particular example, we examine the performance of several forms of modulation and demodulation with partial-band jamming. Our conclusion is that partial-band jammers can be neutralized provided we use codes with rate less than a constant that depends on the form of modulation and demodulation.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD