Engineering topics

Hunt, Brandon

Publications and source records attributed to Hunt, Brandon.

4 records

DOE OSTI2023

A Method of Estimating Sparse and Doubly-Dispersive Channels

The large delay and Doppler spreads of skywave high-frequency (HF) channels complicates channel acquisition, especially in low-SNR conditions. Using pilot-symbol assisted modulation, we develop a robust method to acquire channel information by first estimating the power-delay profile (PDP) of the channel, then applying that estimate to obtain the channel coefficients only where the PDP is nonzero. We find the presented approach to be robust at low-SNRs, making it suitable for spread-spectrum and underlay waveforms. We show that this two-stage channel acquisition procedure has three advantages: i),the channel is estimated with fewer terms, reducing complexity; ii), the MSE of the channel estimate is lower than assuming a fixed channel length; and iii), each propagation mode is reliably recovered in high-Doppler conditions. We conclude this paper by presenting results of the developed techniques as applied to a filter-bank multicarrier spread-spectrum (FBMC-SS) waveform.

42 ENGINEERING↗

DOE OSTI2023

The Performance of FBMC-SS in Challenging HF Channel Environments

Provide overview of FBMC-SS waveform Discuss parameters used for simulated results herein Present simulated results in challenging channel environments Cases: 2 path channel with 2nd path frequency offset 2 path MLD and “VP” channels Large narrowband interferer Highly congested interference case Highly dynamic interference case Clarify previously presented results Make conclusions from presented results

99 GENERAL AND MISCELLANEOUS↗

DOE OSTI2022

Evaluation and Comparison of a New Robust Waveform Against Direct Sequence Spread Spectrum for HF

This paper provides a comprehensive performance comparison between a filter bank multicarrier spread-spectrum (FBMC-SS) waveform and a current robust military waveform; namely, MIL-STD-188-110D, Waveform 0, proposed for communications through ionospheric/skywave HF channels. Waveform 0 is effectively a direct sequence spread spectrum waveform that uses the Walsh multi-codes to enhance the information transmission rate. It may thus be referred to as Walsh-DSSS. FBMC-SS, on the other hand, makes use of filter banks to provide excellent performance when the received signal is subject to partial band interference. Successful application of FBMC-SS for communications across skywave HF channels has been previously demonstrated, both theoretically and through experimental work. However, very little has been done to contrast FBMC-SS against Walsh-DSSS. The goal of this paper is to first add new features to FBMC-SS to bring it on par with Walsh- DSSS. These features include: (i), introduction of multi-codes that achieve a comparable (or better) data rate to the Walsh-DSSS; and (ii), addition of a scrambling step applied to the multi-codes to make the receiver detection robust against widely spread multipaths. With this established, in the second part of the paper, we examine the performance of the developed FBMC-SS against Walsh-DSSS when both are applied for communications across skywave HF channels. The two waveforms are compared both through a theoretical study and through experimental works across several skywave channels ranging from hundreds to thousands of kilometers.

99 GENERAL AND MISCELLANEOUS↗

DOE OSTI2021

Examining the Performance of Walsh-DSSS Against FBMC-SS in HF Channels

Abstract—Filter bank multicarrier spread spectrum (FBMCSS) has proven to be a robust and reliable waveform choice for communication over high frequency (HF) skywave links. However, the performance of this waveform has yet to be contextualized against typical robust HF waveforms, such as the Walsh-encoded waveform detailed in the MIL-STD-188-110D, Appendix D document. In this paper, we first outline the advantages of both the Walsh and FBMC-SS waveforms as well as present their developments. Simulation results are then presented for ideal, simulated HF, and HF with interference channel conditions. Lastly, skywave-HF results are presented for these two waveforms both with and without interference.

99 GENERAL AND MISCELLANEOUS↗