Digital mobile battlefield environments impose challenging obstacles to battle group communications and data management. As future communication capabilities cascade from tactical commanders to individual soldiers, spectral clutter and hostile jamming complicate the task of preserving data throughput. Frequency hop (FH) and direct sequence (DS) methodologies have inherent strengths that must be exploited to overcome communication obstacles. In this paper, we present a hybrid methodology that combines FH waveforms with pulse concealment and transform domain signal processing in order to overcome interference, hostile detection, and jamming. Rejection algorithms are demonstrated which significantly improve system performance in the presence of high-power partial-band jammers, co-site communication signals, and fading.
The objective of this paper is to show the eflect on speech quality by examining the trade08 between the coding gain, provided by channel coding;and modulation adjustments, such as rate-and type-changes. Two basic types of system are utilized to examine the performance tradeojjs. The first sysfem performs a tradeojj between the voice codec and channel codec bit rates, but with a fured symbol rate modulation (FRM). The second sysfem is represented by a similar adaptive-rate voice codec as in thefirst sysfem, but wifh frred-rafe channel coding and adaptiverate modulation (ARM). Within both the FRM and ARM system, we also examine the ejject of changing modulation type. For fhis study, power-efjicient and bandwidth-efficient modulation signaling sets are considered. For the power-efjicient modulation, we utilized M-ay pulse position modulation (PPM) types. M-ary quadrature amplitude modularion (QAM) types were utilized for the bandwidth efjicient modulations. In addition, orthogonal frequency division multiplexing (OFDM) was utilized as the method 10 format and multiplex the digifal data at bmeband. Simulation results show, for higher order modulafions, that the ARM and FRM approaches, respectively, work besr for power-efficient and bandwidth-efjicienf modulations.
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