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The recently promulgated US military standard MIL-STD-188-110C contains an appendix (Appendix D) defining a new family of wideband HF data waveforms supporting bandwidths from 3 kHz to 24 kHz in increments of 3 kHz. This family of waveforms extends the high performance serial tone modem technology of the MIL-STD-188-110B standard to wider bandwidths and much higher data rates, allowing users the option...
This paper will examine the subtle interdependencies of physical layer waveforms and RF power amplifiers when applied to a battery-powered High Frequency (HF) tactical radio system. Traditional physical layer analysis usually compares the signal-to-noise ratio (SNR) required to achieve a desired bit error rate (BER) but does not consider how the peak-power to average-power ratio (PAPR) of the waveform...
The area of digital communications has undergone a significant transformation in the last twenty years due mostly to the discovery of iterative forward error correction (FEC) codes (such as turbo codes) and iterative demodulation techniques (such as turbo equalization). Waveforms developed for the High Frequency (HF) band typically place an interleaver between the FEC scheme and the transmitted symbols...
Constant envelope, spread spectrum modulation is highly desirable for low-power, battery-operated systems - but only if the cost of any increase in receiver complexity or reduction in bit error rate performance is offset by a realizable reduction in either the transmit power or DC power requirements for the system. This paper defines and analyzes a novel approach to a constant envelope spread spectrum...
Constant envelope orthogonal frequency division multiplexing (CE-OFDM) is a modification to OFDM which eliminates the large peak power to average power ratio (PAPR) inherent in OFDM. For uncoded waveforms, CE-OFDM has been shown to offer some significant performance advantages over OFDM on high frequency (HF) multipath fading channels. However, when coding and interleaving are added to the waveforms,...
Modern single-carrier HF waveforms require tight digital and analog filters in order to meet current HF bandwidth allocations. Unfortunately, this filtering process produces a variation in the peak-power of the waveform relative to the average-power. The effect of this variation is that a back-off is required at the input to a power-amplifier (PA) (when using a peak-power limited PA) to avoid operating...
Research continues to explore mechanisms to increase data throughput over HF circuits. Several of these techniques rely on the use of multiple 3 kHz channels to increase the overall bandwidth and therefore the data capacity available to the user. Depending on the particulars of the technique, some may be sensitive to the variability of HF channel conditions across the set of utilized channels. This...
Power amplifiers (PAs) convert low-power radio frequency (RF) signals into high-power RF signals. Most wireless communication systems employ power amplifiers in order to increase the operating range of the system. However, this conversion process can have some undesired effects on the underlying physical layer waveforms that are used for communicating. This paper will investigate these undesired effects...
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