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<p>The Joint Tactical Information Distribution System (JTIDS)) is a hybrid frequency-hopped, direct sequence spread spectrum system which used cyclic code-shift keying (CCFK) for M-ary symbol modulation and minimum shift-keying (MSK) for chip modulation.  In addition JTIDS uses a (31, 15) Reed Solomon (RS) code for channel coding.  In this thesis an alternative waveform consistent with the original JTIDS waveform is analyzed.  The system to be considered uses a concatenated code consisting of a (31, k) Reed Solomon inner code and a 4/5 convolutional outer code.  The coded symbols are transmitted on the in-phase (I) and quadrature (Q) components of the carrier using 32-ary orthogonal signaling with 32 chip basedband waveforms such as Walsh functions.  Performance with both coherent and noncoherent detection is analyzed.  For noncoherent detection only one five bit symbol is transmitted on the I and Q components of the carrier per symbol duration, so the data throughput for noncoherent detection 1/2 that of coherent detection.  No diversity, consistent with JTIDS single-pulse structure, and a sequential diversity of two, consistent with JTIDS double-pulse structure, are both considered.  For the double-pulse structure, performance is examined both for the case of linear soft diversity combining and also for soft diversity combining with perfectside information.  Performance is examined for both AWGN only, as well as for AWGN and pulse-noise interference.  Based on the results of this thesis, the proposed waveform is found to outperform the existing JTIDS/Link-16 waveform in all cases considered in this research.  Indeed, the best performance for the atlernative waveform is obtained when an (31, 25) RD inner code is used.  When only AWGN is present, the proposed waveform with no diversity has a gain of 2.6 dB and 2.5 dB as compared to the existing JTIDS/Link-16 wavefoorm for coherent and noncoherent demodulation, respectively, when Pb =10-5.  Likewise in an AGWN only environment with a diversity of two, the proposed waveform outperforms the existing JTIDS/Link-16 waveform by 3.15 dB and 23 dB for coherent and noncoherent detection, respectively.  When PNI is also present, the proposed waveform performs significantly better than the existing JTIDS waveform in all cases considered.  Finally, the use of a concatenated code consisting of a (31, 25) RS inner code and a 4/5 convolutional outer code results in a 33% improvement in throughput as compared to the existing JTIDS/Link-16 waveform.
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<br>Subjects: Noise; Electrical engineering; Sound</div>
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Aivaliotis, Theodoros.</div>
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