Spectral occupancy of fixed and mobile allocations within the high frequency band

Abstract

Power levels in the High Frequency (HF) band from 3 to 30 MHz were measured to determine channel occupancy statistics including patterns in time and frequency. Congestion in Canadian spectrum allocations for fixed and mobile users and patterns in the ambient radio noise power across the HF band were examined. A receiver site was set up in Ottawa, Canada using a spectrum analyzer and an omni-directional, horizontally polarized antenna having an elevation pattern optimized for reception of signals arriving via sky wave propagation. Diurnal and random fluctuations in channel occupancy, congestion, and noise measurements were observed and sample data plots for fixed and mobile allocations were presented and discussed. The availability of unoccupied channels in bandwidth increments of 3, 12, and 24 kHz for each 1 MHz frequency range is discussed and may be used to inform future assignments for fixed and land mobile services in the Canadian Table of Frequency Allocations. Hourly variations in channel occupancy show that there are ample spans of contiguous unoccupied spectrum to support channel bandwidths up to 24 kHz during most hours of the day; however, during the most congested times, even 3 kHz contiguous channels are not available in the frequency ranges that are optimal for propagation. These results suggest that spectrum availability in the region can support the use of wideband HF modems; however, the optimal modulation bandwidth will vary according to the time of day and the number of channels required.