WO2007064953A2

WO2007064953A2 - Hf radio network frequency management

Info

Publication number: WO2007064953A2
Application number: PCT/US2006/046121
Authority: WO
Inventors: John W. Ballard; John M. Goodman; David Mansoir
Original assignee: Radio Propagation Services, Inc.
Priority date: 2005-12-01
Filing date: 2006-11-30
Publication date: 2007-06-07
Also published as: EP1955446A2; WO2007064953A3; EP1955446A4; WO2007064953A8

Abstract

Determining a HF radio contact list is disclosed. A plurality of target radio station locations is received. For each target radio station location, one or more HF radio operating frequencies is received, and HF radio communication suitability to each target radio station location is determined using the one or more operating frequencies. A HF radio contact list is determined.

Description

HF RADIO NETWORK FREQUENCY MANAGEMENT

CROSS REFERENCE TO OTHER APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application

No. 60/742,090 entitled HG NETWORK FREQUENCY MANAGEMENT filed December 1, 2005 which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

[0002] Radio communication over long distances (e.g., thousands of kilometers) is possible using high frequency (HF) radio wave communications. One positive aspect of HF communication is that it does not rely on expensive satellites in order to achieve communication over these long distances. However, the ability of HF radio communication to reach a given location from a transmitter is dependent on the frequency of the radio transmission and the properties of the ionosphere, an ionized layer of the atmosphere that refracts the HF radio waves of the transmission back down to a receiver station. The properties of the ionosphere vary depending on solar conditions, and in some cases, the ionospheric conditions are such that radio waves do not refract downward appropriately such that communication between two stations for any operating frequency may not be possible.

[0003] Reliable HF service requires the invocation of substantial space and frequency diversity. Today, ships at sea and air transport aircraft over oceans are each served by a ground network of approximately 25 stations, each of which has approximately ten frequencies, resulting in a standing menu of approximately 250 choices, of which generally a dozen frequency-station pairs will work well. The subset of choices that works well is determined by the effects of highly variable solar radiation on the earth's ionosphere, a very complicated set of processes into which the ship or aircraft commander has no effective view. Trying to communicate by attempting contact on each of a large array of frequency-station pairs can be very time consuming. Trying a few frequency-station pairs arrived at by guesswork, heuristic, or intuition generally results in poor reliability, poor service, and long times to complete a communication link.

[0004] It would be beneficial to be able to communicate using HF radio without the accompanying reliability issues and with being able to avoid a long period of time required to establish a communication link. .

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Various embodiments of the invention are disclosed in the following detailed description and the accompanying drawings.

[0006] Figure 1 is a block diagram illustrating an embodiment of a HF network.

[0007] Figure 2 is a block diagram illustrating an embodiment of a system for

HF radio network frequency management.

[0008] Figure 3 is a flow diagram illustrating an embodiment of a process for

HF radio network management by determining a HF radio contact list.

[0009] Figure 4 is a flow diagram illustrating an embodiment of a process for determining reliabilities for communicating with target radio stations from the mobile station.

DETAILED DESCRIPTION

[0010] The invention can be implemented in numerous ways, including as a process, an apparatus, a system, a composition of matter, a computer readable medium such as a computer readable storage medium or a computer network wherein program instructions are sent over optical or communication links. In this specification, these implementations, or any other form that the invention may take, may be referred to as techniques. A component such as a processor or a memory described as being configured to perform a task includes both a general component that is temporarily configured to perform the task at a given time or a specific component that is manufactured to perform the task. In general, the order of the steps of disclosed processes maybe altered within the scope of the invention.

[0011] A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.

[0012] HF radio network management is disclosed. A HF radio contact list is determined. A plurality of target radio station locations is received. For each target radio station location, one or more HF radio operating frequencies is received and HF radio communication suitability — for example, expected signal to noise ratio (SNR), reliability, signal strength, multipath spread, etc. - is determined to each target radio station location using the one or more operating frequencies. A HF radio contact list is determined as ordered by communication suitability of the target radio station and operating frequency that are used to communicate with the target radio station, hi some embodiments, reliable HF radio communication is achieved from a mobile HF station (e.g., a boat, a ship, an airplane, a balloon, a dirigible, a car, a truck, etc.) by having a list of multiple operating frequency/target radio station pairs to communicate with at any time from any location. By having the ability to rank a number of operating frequencies and target radio stations, the mobile station is enabled to have reliable (or effective) communication with at least one target radio station that can relay or connect the communication using other communication networks (e.g., land line phone, Internet, wireless phone, etc.). In some embodiments, the reliable HF radio communications network enables emergency communications. [0013] In some embodiments, Reliability, R, is the probability that the evaluated SNR is greater than the required SNR (or RSNR) for a specified grade of service. A circuit is generally described as "reliable" if its computed "Reliability" is >0.90. There are circumstances whereby a value of R < 0.90 may be considered "acceptable". The situation can be different for networks. For example, a star network, which is the type generally dealt with, the Reliability may be some value less than 90% for individual "legs" or circuits of the network (taking all possible frequencies into account), but the combined reliability can achieve a value much greater than 90%, as a result of station and frequency diversity. The effective network reliability of a diversity network must be ~ 99% or more, with the proviso that timely and accurate specification of an ordered list of best stations and frequencies is available. A potential network reliability of 99% is not always acceptable if it takes too long to achieve it.

[0014] In some embodiments, analytical and computational tools are used to assess all possible frequency-station pairs to the ship or aircraft rapidly (e.g., in a matter of a few seconds), and thereby are able to present a mobile station user or operator (e.g., the ship or aircraft commander) a brief list of selections, ranked generally by reliability, and all of which are highly likely to provide rapid and reliable (or a "timely and effective") service.

[0015] Figure 1 is a block diagram illustrating an embodiment of a HF network, hi the example shown, a mobile station 100 desires to communicate using High Frequency (HF) Radio, which includes radio communication at frequencies between 3 and 30 MHz. Mobile station 100 can be a boat, a ship, an airplane, a balloon, a dirigible, a car, a truck, or any other mobile item/platform that desires communication. At the HF frequencies, the radio waves travel upward and may be refracted downward by an ionized layer of the atmosphere, the ionosphere, allowing communication between two stations that are thousands of kilometers apart, hi some cases, the communication signals are transmitted by a radio transmitter connected to an antenna, and the radio signals travel upward and are refracted downward, making one hop, to be received by an antenna attached to a radio receiver, hi other cases, the transmitted radio signals can make multiple hops by also reflecting off the ground or ocean before being received by a radio receiver. At any time, there are a plurality of target radio stations of the HF network to communicate with using HF radio, represented in Figure 1 by 102, 104, 106, 108, and 110. Each of the target radio stations has a set of operating frequencies. The reliability for mobile station 100 to communicate with the HF network increases with the number of target radio stations available and the number of operating frequencies available, hi some embodiments, if four target radio stations and eight operating frequencies (e.g., yielding 32 independent possibilities) are always available to the mobile station, then reliable communications are almost always available (e.g., greater than 99% of the time), even though many of the individual circuits (defined by independent station designations and frequency specifications) in the 32 possibilities may have reliabilities R of much less than 99%. It only takes one of the 32 candidates to have a high reliability.

[0016] HF communications are most distressed during magnetic storms, when the earth's magnetic field, through a process of opening and reconnecting magnetic field lines, sequentially injects energetic particles into the high latitude region. The ionosphere is heated, the electron density profile becomes profoundly deformed, and electron density patterns in the lower ionosphere that are most sensitive for HF communication, are forced away from the medians of climatological models. These disturbances propagate equatorward, over a period of hours. Predominantly the ionospheric response to geomagnetic storms is determined by the geomagnetic latitude concerned. For geomagnetic storms, and in the absence of other effects, the modification of the electron density can be defined by a structure modification function m (h,λ,t) where h represents ionospheric height, λ represents geomagnetic latitude, and t represents time. The function m is the ratio of the (estimated) true electron density to the climatological median. In some embodiments, this fairly general expression, is simplified so that the functional relation to one or more m- factors representing the most important ionospheric layer or layers. In some embodiments, one m-factor corresponding to an ionospheric layer - for example, the F2 layer - is used. In some embodiments, a typical characterization of the situation imposes a single time-dependent m-factor, m(λ, t), which varies between about 0.25 and 1.5. hi some embodiments, an array of m-factors accounts for multiple layers, a specified array of geomagnetic latitudes, and for a finite duration of time (i.e., up to 36 hours).

[0015A] The ionosphere is highly variable and often departs from a simple m- factor recipe whether geomagnetic storms are in evidence or not. For this situation, a more general array for the F2 layer m-factor is used: m = m(θ, φ, t) where θ and φ represent geographic latitude and longitude, and t represents time (as before). The granularity in space and time is defined by the physics, but in practice a sparse array for m that is determined by available sensor data along with spatial extrapolation models are specified. In various embodiments, sensor data comprise satellite imagery data, coronal hole data, coronal mass ejection data, solar flare data, satellite measurement data of solar particle flux including number and energy distribution data, interplanetary wind data, magnetic field data, total electron content data measured between GPS satellites and the ground, vertical or oblique ionospheric sounding data, m factor data, or any other appropriate data relevant to ionospheric conditions.

[0017] During the course of a storm, through modeling and monitoring current ionospheric assessment tools, a series of useful estimates of the distribution of the m factor as a function of magnetic latitude is developed and is used to modify the electron density at the reflection points of each path in the computational model employed. These estimated distributions of the m factor change as the storm in question develops, matures and decays.

[0018] Figure 2 is a block diagram illustrating an embodiment of a system for

HF radio network frequency management. In the example shown, computational engine 200 has as inputs mobile station location, ionospheric measurement data, target radio station list with operating frequency list for each target radio station, and a calculation frequency list (if any). Computation engine 200 includes prediction module 202. In various embodiments, prediction module 202 incorporates portions of one or more climatological models or calculation models of the ionosphere available in the public domain - for example, HF communication performance programs such as Voice of America Coverage Analysis Program (VOACAP), Ionospheric Communications Enhanced Profile Analysis and Circuit (ICEPAC), or the propagation prediction model based on the International Telecommunication Union's (ITU) propagation model Recommendation ITU-R PI.533 (REC533). Computation engine 200 has as output a HF radio contact list. The HF radio contact list is a list of target radio station/operating frequency pairs that are listed in order of calculated suitability for communication from the mobile station.

[0019] In some embodiments, target radio station locations are derived from a database of radio station locations. The database includes other associated information including operating frequencies.

[0020] In some embodiments, ionospheric model data includes satellite imagery data which may include proton precipitation data and/or electron precipitation data, ultra-violet remote sensing data, coronal hole data, coronal mass ejection data, solar wind data, solar active region data, interplanetary magnetic field data, solar flare data, in-situ satellite measurement data which may include x-ray flux data, particle flux and energy distribution data, topside sounder data, vertical incidence sounder data, oblique incidence sounder data, geomagnetic field data which may include Dst, Kp, and Ap index data and/or magnetogram data, Faraday rotation polarimeter total electron content data, ground based monitors exploiting global positioning system (GPS) constellation waveform total electron content data, m factor data, global maps (e.g., a map derived from the fusion of multiple independent electron density measurements and techniques such as global assimilation of ionospheric measurements (GAIM) technology), or any other appropriate data relevant to ionospheric conditions. In various embodiments, the ionospheric model data is quasi-real-time, predicted (e.g., up to a day in advance, predicted based on current or projected magnetic storm data, or any other appropriate time relevant window data.

[0021] In some embodiments, ionospheric model data is provided by a server which preprocesses data to be appropriate for input to a computational engine such as computation engine 200.

[0022] In some embodiments, m factor data comprises a measure of the modification of the electron density as a function of magnetic latitude. In some embodiments, the m factor used in the computation of the radio contact list is based at least in part on an estimate of the m factor as a function of magnetic latitude and the magnetic latitude of the reflection point between the mobile station location and a given target radio station location. In some embodiments, the calculation frequency list is a sampling of all possible frequencies in the HF spectrum that represent the possible operating frequencies. Actual operating frequencies for a given target radio station are generally selected that are immediately below the top ranked calculation frequency that reliably communicated with the given target radio station. Selecting frequencies which are immediately below the calculation frequencies protects against choosing frequencies that are above the Maximum Useable Frequency (MUF), at the expense of some modest diminution of signal-to-noise ratio. In some embodiments, there are instances when signal-to-noise ratio is deemed more important than assured linking on the first few choices, in these cases frequencies are selected that are above the calculation frequencies.

[0023] Figure 3 is a flow diagram illustrating an embodiment of a process for

HF radio network management by determining a HF radio contact list. In some embodiments, the process of Figure 3 is executed by computation engine 200 of Figure 2. In the example shown, in 300 ionospheric model data, a target radio station location list, an operating frequency list for each station, and a mobile station location are received. In some embodiments, a calculation frequency list is also received. In some embodiments, no ionospheric model data is received and the suitability calculation uses built in "average" data for the ionosphere, hi some embodiments, the target radio station list and operating frequency lists for each target radio station are preloaded or are already saved and do not need to be input for the generation of the contact list, hi 302, suitabilities are determined for communicating with target radio stations from the mobile station. There are one or more operating frequencies for which communication suitabilities are determined, hi 304, a rank ordered contact list is determined for the mobile station. The rank ordered list lists, in order of suitability, operating frequency - target radio station pairs that can be used to communicate between the mobile station and the HF radio network reliably. [0024] In various embodiments the suitabilities are calculated for the present or for some time in the future - for example, up to a day in advance.

[0025] In some embodiments, a mobile station may wish to avoid interfering with or being heard by a particular target radio station. In this case, the rank ordered contact list for the mobile station lists, in order of reliability, operating frequency - target radio station pairs that can be used to communicate between the mobile station and the HF radio network reliably and that communication for those frequencies with the particular undesired target radio station is unreliable or very unreliable. In some embodiments, this is achieved by choosing frequencies to communicate with that are above the maximum observed frequency (MOF) to communicate between the mobile station and the undesired target radio station, as these are very likely to be of lower reliability or suitability.

[0026] As to selection of reliable frequency values, it should be noted that maximum usable frequency (MUF) results are monthly median values of a set of all MOF results, whereas MOF results are instantaneous values, hi the case where realtime ionospheric information is available, the MOF results are used to select reliable frequencies to communicate with because the best reliability frequencies (in terms of signal to noise ratio) for communicating are close to, but not exceeding, the MOF.

[0027] Figure 4 is a flow diagram illustrating an embodiment of a process for determining suitability for communicating with target radio stations from the mobile station, hi some embodiments, the process of Figure 4 is used to implement 302 of Figure 3. In the example shown, the ionospheric model data is included, if necessary. In the case where ionospheric data is input (e.g., into the computation engine such as computation engine 200), the data is incorporated appropriately for the calculation of suitability of communication, hi 402, a target radio station is selected, hi 404, a frequency is selected. In various embodiments, the frequency comprises an operating frequency of the target radio station or the frequency comprises a frequency selected for the calculation (e.g¹., a frequency of a sampled set of frequencies that spans the HF radio frequency band). In 406, communication suitability is calculated between the mobile station and the selected target radio station using the selected frequency. In 408, it is determined if there is another frequencies for the selected target radio station for which a suitability is to be calculated. If so, control passes to 404. If not, it is determined in 410 if there is another target radio station for which a suitability is to be calculated. If so, control passes to 402. If not, the then process ends. In some embodiments, all possible paths or frequencies to all possible target radio stations are computed. In some embodiments, a subset of all possible paths or frequencies to a subset of all possible target radio stations are computed. In various embodiments, suitability comprises one or more of the following: reliability, signal strength, expected SNR, multipath spread, number of f days, or any other appropriate measure of quality for communication between two radio stations.

[0028] In some embodiments, HF radio communication suitability to each target radio station location for a set of operating frequencies is determined by selecting a set of calculation frequencies that partition an HF propagation band efficiently, determining HF radio communication suitability for the set of calculation frequencies, and determining HF radio communication suitability for each of the set of operating frequencies based on the HF radio communication suitability of at least one of the calculation frequencies (e.g., a calculation frequency that is the closest frequency that is higher than the operating frequency).

[0029] In some embodiments, HF radio communication suitability, or rather unsuitability, to an unfriendly radio station location or a plurality of unfriendly radio station locations is calculated by finding the least suitable (e.g., reliable) frequencies to communicate on. In some embodiments, it is desirable to communicate with a friendly set of target with an unfriendly set of targets receiving little or none of a given message. This can be achieved by choosing a high suitability frequency or high suitability frequencies to communicate with for friendly target radio stations which are at the same time a low suitability frequency or low suitability frequencies for unfriendly target radio stations.

[0030] Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, the invention is not limited to the details provided. There are many alternative ways of implementing the invention. The disclosed embodiments are illustrative and not restrictive.

Claims

[0031] WHAT IS CLAIMED IS: CLAIMS

1. A method for determining a HF radio contact list comprising: receiving a plurality of target radio station locations; for each target radio station location: receiving one or more HF radio operating frequencies; determining HF radio communication suitability to each target radio station location using the one or more operating frequencies; and determining a HF radio contact list.

2. A method as in claim 1, wherein the HF radio contact list comprises a list of target radio stations and operating frequencies that is ordered by communication suitability from highest to lowest.

3. A method as in claim 1, wherein suitability comprises one or more of the following: reliability, signal strength, expected SNR, multipath spread, or number off days.

4. A method as in claim 1 , wherein determining HF radio communication suitability to each target radio station location using the one or more operating frequencies comprises: selecting a set of calculation frequencies that partition an HF propagation band efficiently; determining HF radio communication suitability for the set of calculation frequencies; and determining HF radio communication suitability for each of the one or more operating frequencies based at least in part on the HF radio communication suitability of one frequency of the set of calculation frequencies;

5. A method as in claim 3, wherein the HF radio communication suitability for one of the one or more operating frequencies is based at least in part on the HF radio communication suitability of one frequency of the set of calculation frequencies that is higher than the one of the one or more operating frequencies.

6. A method as in claim 1, wherein HF radio communication suitability is based at least in part on the received ionospheric model data.

7. A method as in claim 6, wherein the ionospheric model data comprises one or more of the following: satellite imagery data, proton precipitation data, electron precipitation data, ultra-violet remote sensing data, coronal hole data, coronal mass ejection data, solar wind data, solar active region data, interplanetary magnetic field data, solar flare data, in-situ satellite measurement data, x-ray flux data, particle flux and energy distribution data, topside sounder data, vertical incidence sounder data, oblique incidence sounder data, geomagnetic field data, Dst index data, Kp index data, Ap index data, magnetogram data, Faraday rotation polarimeter total electron content data, ground based monitors exploiting GPS constellation waveform total electron content data, m factor data, or global maps.

8. A method as in claim 6, wherein the ionospheric model data comprises one or more of the following: quasi-real-time data, predicted ionospheric model data, up to one day in advance predicted ionospheric model data, predicted ionospheric impact based at least in part on current magnetic storm data, or predicted ionospheric impact based at least in part on projected magnetic storm data.

9. A method as in claim 1, wherein the ionospheric model data is received from a server.

10. A method as in claim 1 , wherein determining HF radio communication suitability to each target radio station location is based at least in part on a HF communication performance program.

11. A method as in claim 10, wherein the HF communication performance program comprises one of the following: VOACAP, ICEPAC, or REC533.

12. A method as in claim 1, further comprising: receiving a plurality of unfriendly radio station locations; for each of the unfriendly radio station locations: receiving one or more HF radio operating frequencies; determining HF radio communication suitability to each unfriendly radio station location using the one or more operating frequencies; deteπnining a HF radio avoidance list, wherein the HF radio avoidance list includes frequencies that have low suitability for the unfriendly radio station locations; and determining a HF radio preferred list, wherein the HF radio preferred list includes operating frequencies that are suitable for the target radio station locations and low suitability for the unfriendly radio station locations.

13. A method as in claim 1, wherein the suitabilities are determined for one of the following: the present, the future, or a time up to one day in advance of the present.

14. A computer program product for determining a HF radio contact list, the computer program product being embodied in a computer readable medium and comprising computer instructions for: receiving a plurality of target radio station locations; for each target radio station location: receiving one or more HF radio operating frequencies; determining HF radio communication suitability to each target radio station location using the one or more operating frequencies; and determining a HF radio contact list.

15. A system for determining a HF radio contact list comprising: a processor; and a memory coupled with the processor, wherein the memory is configured to provide the processor with instructions which when executed cause the processor to: receive a plurality of target radio station locations; for each target radio station location: receive one or more HF radio operating frequencies; determine HF radio communication suitability to each target radio station location using the one or more operating frequencies; and determine a HF radio contact list.

16. A system for determining a HF radio contact list comprising: a processor; and a memory coupled with the processor, wherein the memory is configured to provide the processor with instructions which when executed cause the processor to: receive a request for ionospheric model data, wherein the ionospheric model data is used to: determine HF radio communication suitability for communicating with each of a plurality of target radio station locations using one or more operating frequencies; and determine a HF radio contact list based at least in part on the determined HF radio communication suitabilities; and transmitting the requested ionospheric model data.