A New MIMO HF Data Link: Designing for High Data Rates and Backwards Compatibility

High frequency (HF) radios (the 3-30 MHz range) provide tactical communications with the ability to communicate over long distances and around large obstructions without supporting infrastructure (e.g., satellite links). Unfortunately, spectrum is scarce in the low HF operating frequencies. To improve spectral efficiency, commercial UHF/SHF systems have offered multiple antennas with intelligent signal processing (MIMO). MIMO not only amplifies spectral efficiency, but also reduces transmit power, rejects jamming, and increases link reliability. In a companion paper, we demonstrated HF MIMO feasibility with compact cross-polarized arrays through measurements. In this paper, we leverage those measurements to design a new MIMO HF physical layer based on the existing single-antenna MIL-STD-188-110C-Appendix-D wideband HF standard. We include simulation results based on our channel measurements to show that this new standard provides 116% improvement in overall throughput and a 15 dB signal-to-noise ratio (SNR) improvement over the highest-rate single-antenna modes due to greater reliability and reduced sensitivity to amplifier nonlinearities.