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An unusually long period of very low solar activity was of great interest. Investigation of the characteristics of radio propagation in the European region during this period shows that correspondence between the experimental and IRI model parameters foF2, hmF2, TEC, M3000, MUF3000 may be worse than during moderate activity periods. The disturbed state in this period is characterized by the index...
A physics-based technique for interpolating magnetic and electric field disturbances of external origin across large spatial areas can be achieved by employing the Spherical Elementary Current System (SECS) method using data from ground-based magnetic observatories. The SECS method represents complex electrical current systems as a simple set of equivalent currents placed at a specific height in the...
The spectrum time ‘waterfall’ of a received DRM (Digital Radio Mondiale) signal contains information about the ionosphere around the half-way point of the path between transmitter and receiver. Typical DRM signals have a flat-topped spectrum that is 9kHz or 10kHz wide. The most easily observed patterns in the spectra are caused by multipath interference mainly between one-hop and two-hop paths. The...
This paper presents and demonstrates a system for very high data rate (about 80 kbps) multimedia transmissions over HF channels. Optimizations are proposed at various levels of the OSI/ISO protocol stack, to enable efficient use of standard multimedia and data IPv6 applications in HF, in a way that is completely transparent for the end user. A demonstration test-bed was built, in order to evaluate...
This paper presents a comparison of Chilton ionosonde critical frequency measurements against vertical-incidence HF propagation predictions using ASAPS (Advanced Stand Alone Prediction System) and VOACAP (Voice of America Coverage Analysis Program). This analysis covers the time period from 1996 to 2010 (thereby covering solar cycle 23) and was carried out in the context of UK-centric near-vertical...
Traditional use of the HF band is limited mostly to 3 KHz for both voice and data transmission, and therefore, most of the transceivers bandwidths are also adapted to this profile. However, there are some initiatives that clearly state that much broader bandwidths may be use with the corresponding data rate increase and performance improvement in the HF band [1,5]. Due to the increased bandwidth,...
The US MIL-STD-188-110B has been revised to MIL-STD-188-110C and includes Appendix D defining a family of wideband HF data waveforms supporting bandwidths from 3 kHz to 24 kHz in increments of 3 kHz. This waveform family, designed by engineers at Harris Corporation and Rockwell Collins, extends the high performance serial tone modem technology of the original versions of the standard to wider bandwidths...
This paper begins with a brief overview of HF data transport requirements leading to waveform design and interoperability considerations for the expanded bandwidths provided with MIL-STD-188-110C Appendix D Wideband HF (WBHF). Over-the-air (OTA) performance test results of the WBHF suite of data waveforms, focusing upon shorter data bursts used in Automatic Repeat-Request (ARQ) and networking applications...
A new artificial ionospheric modification (AIM) experiment, known as Metal Oxide Space Clouds (MOSC) is briefly described. In support of this experiment a new HF sounder has been designed and is described in the paper.
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,...
Conventional methods for planning radio services at medium frequencies can lead to pitfalls. ITU Recommendation P.1147 favours idealised antennas with no room for real patterns or reflection heights, which can result in anomalies going un-noticed. One idealised antenna is the anti-fade monopole, conventionally optimised assuming fixed layer height, and a perfect ground. A small residual sky-lobe is...
The nominally vertical E-field of a ground wave is classically predicted to tilt forward in the direction of wave travel. Past measurements confirming this have been made at four spot frequencies between 5.25 and 28MHz by NTIA in Boulder, Colorado, USA reported in 1984. The ellipticity of the wave motion was also measured. A novel tuned loop based wavetilt equipment has been devised to make measurements...
A new approach to predicting the quality of binary message transmission via a narrowband shortwave channel is proposed. This approach is based on using the simulation adaptive model of a channel which describes actual mechanisms of short wave propagation in magneto-active spatially non-uniform ionosphere in connection to specific helio- and geophysical conditions. Resultantly, the quality of transmission...
This paper presents an assessment of GNSS receiver signal tracking performance under scintillating conditions, through the analysis of receiver Phase Lock Loop (PLL) jitter variance maps, a concept introduced in [15]. These maps are constructed for scintillation events observed at three stations in Brazil: (1) Presidente Prudente (22.1°S, 51.4°W, dip latitude ∼ 12.3°S), located close to the Equatorial...
A new US military HF data modem standard defining a family of wideband HF data waveforms supporting bandwidths from 3 kHz to 24 kHz in increments of 3 kHz has recently been completed and ratified. The discussion begins with a brief overview of HF data transport requirements leading to the waveform design and interoperability considerations for the expanded bandwidth. The scope of the test results...
We present the results of application high-orbital (GPS/GLONASS) and low-orbital (Parus/TRANSIT) satellite navigation systems to the study of different-scale irregularities in the ionospheric total electron content (TEC), such as troughs, crests of equatorial anomaly, traveling ionospheric disturbances and so on. We also present the results of the comparison of the global ionospheric maps (GIM) of...
It is well known that the ionosphere affects radio waves propagation on Earth-space paths. One of the ionosphere characteristics influencing such propagation is the total electron content (TEC) that the wave encounters in his course. The knowledge of TEC behaviour under different time, geographical and solar activity conditions and its variability is important for satellite communication system planning...
This paper describes the architecture of an IP Gateway system implementing various enhancements to enable efficient and transparent use of standard multimedia and data IPv6 applications over strongly varying and bandwidth-limited wireless links such as HF radio. Three optimizations are proposed : (a) an HF-oriented Performance Enhancing Proxy (PEP) to improve the Quality of Service (QoS) of TCP/IP...
Multi-carrier modulations are widely employed in ionospheric communications to mitigate the adverse effects of the HF channel. In this paper we show how performance achieved by these modulations can be further increased by means of CSI-based precoding techniques in the context of our research on interactive digital voice communications. Depending on communication constraints and channel parameters,...
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