Technique for determining propagating and clear frequency to be used in wide area wireless data communications network

• US 5,640,442 A
• Filed: 09/24/1996
• Issued: 06/17/1997
• Est. Priority Date: 06/06/1995
• Status: Expired due to Term

• Current Assignee: HySky Technologies, Inc.
• Original Assignee: Flash Comm Incorporated (General Electric Company)
• Inventors: Belcher, Donald K., Fitzgerald, Brendan T., Nelson, Rodney, White, Jeffrey R., Powshok, Andrew T., Darby, Albert D. Jr.
• Primary Examiner(s): CUMMING, WILLIAM D
• Application Number:
  US08/719,307
• Time in Patent Office: 266 Days
• Field of Search: 379/57, 455/56.1, 455/134
• US Class Current: 340/7.21
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 84/022 One-way selective calling networks, e.g. wide area paging

Abstract

A two-way communications system that provides ubiquitous wireless data communication services, such as throughout the continental United States, by using a network of only a few, widely distributed radio base station (RBS) sites and the existing paging network infrastructure. The paging network infrastructure is used as an outbound link to request data from the remote field units. The outbound page message indicates a time and HF frequency at which the RBSs can expect to receive inbound data from the field units. A network hub or mission operation center (MOC) determines a radio frequency which is expected to be propagating and clear at the time that a particular field unit is to use the frequency as an inbound link. The MOC then issues the request for data to the field unit using an existing inexpensive wireless system such as the paging network infrastructure. The field units make use of paging receivers, and an HF transmitter to report remote data such as a geoposition or other sensor data when requested to do so.

Claims

1. A two-way wireless data communication system comprising:

an outbound messaging sub-system;

an inbound messaging sub-system consisting of at least one radio frequency base station for receiving inbound messages;

a frequency analysis processor (FAP) associated with each of the at least one radio frequency base station, each of the FAPs continuously sampling, at their respective locations, received power levels across a set of frequencies in an inbound radio frequency band, to determine an observed frequency availability level for the set of frequencies for each base station;

a propagation analysis processor (PAP) which determines a probability of propagation for the set of frequencies;

at least one remote field unit having an outbound message receiver and a tunable inbound message transmitter; and

a central control unit, wherein the central control unit uses the outbound messaging sub-system to send an outbound message to the remote field unit, and uses the inbound messaging subsystem as an inbound link to receive an inbound message from the field unit, and wherein the outbound message includes data fields indicating an inbound time and an inbound carrier frequency at which the field unit is to send each inbound message, and wherein the central control unit receives reports of the observed frequency availability levels from the FAPs, and the central control unit also receives reports of the probabilities of the frequencies propagating from the PAP, and wherein the central control unit selects the inbound carrier frequency depending upon both the frequency availability levels as reported by the FAPs as well as the probability of the frequency propagating as reported by the PAP, such that the probability that the inbound message will be received by at least one of the base stations without interference from another communication system is maximized.

2. A system as in claim 1 wherein the inbound messaging sub-system uses the high frequency (HF) radio frequency band as the inbound radio frequency band.

3. A system as in claim 2 wherein the outbound messaging sub-system is a paging sub-system.

4. A system as in claim 1 wherein the PAP additionally comprises:

database means, for maintaining a table of propagation probabilities, the propagation table containing an array of entries for each possible frequency and time of day.

5. A system as in claim 2 comprising multiple inbound links implemented by multiple radio base station receivers, and wherein the control unit assigns the carrier frequency depending upon the observed availability of that carrier frequency in each of the multiple radio base station receivers.

6. A system as in claim 4 comprising multiple inbound links implemented by multiple radio base station receivers, and wherein the PAP maintains a propagation table for each of the base station receivers.

7. A system as in claim 4 wherein the propagation table is initially written with propagation probability values determined by an analytic propagation model.

8. A system as in claim 4 wherein the PAP additionally updates the propagation table as successful and failed inbound message transmissions are reported by the MOC.

9. A method of operating a communications system to provide reliable and ubiquitous wireless data communication services between a mission operation center (MOC) an plurality of remote field units, by using a network of widely distributed radio base station (RBS) sites, the method comprising the steps of:

A. at a customer calling station, initiating a request to the MOC to communicate with a particular remote field unit, such as a request for the field unit to determine and report its location;

B. at the MOC site,

i. receiving reports from a propagation analysis processor (PAP), the PAP reports indicating a probability that a list of radio frequencies will propagate from field unit locations to RBS sites;

ii. receiving reports from frequency analysis processors (FAPs) located at the RBS sites, the FAP reports indicating a list of radio frequencies which are presently available for the field unit to send an inbound message back to one or more of the RBS sites;

iii. determining a frequency for the field unit response based upon both the data reported by the PAP as well as the data reported by the FAP;

iv. determining an available time for the field unit response;

v. formatting the determined time and frequency for the field unit response into an outbound page message;

iv. forwarding the page message to at least one of the paging systems;

C. in at least one of the paging system sites, communicating the page message to the field units over the paging system;

D. at the selected field unit,

i. receiving the page message;

ii. formulating a response to the page message by reading data available locally to the field unit;

iii. formulating a response as an inbound message back to the radio base stations;

iv. encoding the response in the form of a short duration burst message, to minimize the probability of interfering with existing broadcast or other communications at frequencies near the selected frequency;

v. at the indicated carrier frequency and time, transmitting the inbound message over the air;

E. at the RBS site,

i. receiving the inbound message from the field unit over the air; and

ii. forwarding the inbound message back to the MOC;

F. at the MOC site, forwarding the inbound message back to the customer calling station; and

G. at the calling station, receiving inbound message.

10. A method as in claim 9 wherein the calling stations are connected to the MOC through the land based public switched telephone network (PSTN).

11. A method as in claim 9 wherein the MOC is connected to the paging systems through the land based public switched telephone network (PSTN).

12. A method as in claim 9 wherein the MOC communicates with the RBSs over a land-based connection such as the public switched telephone network.

13. A method as in claim 9 wherein the MOC communicates with the RBSs over a land-based connection such as a leased private telephone circuits.

14. A method as in claim 9 additionally comprising the step of,

at the MOC, alerting one or more of the associated RBSs to expect a response from the indicated field unit at the specified frequency and time.

15. A method as in claim 14 additionally comprising the steps of,

H. at the RBS, if no such inbound message is received as alerted by the MOC, reporting a failed inbound message to the PAP;

and

I. at the PAP, updating a table of expected probabilities of propagation based upon the failed inbound message report.

16. A method as in claim 14 additionally comprising the steps of,

H. at the RBS, if an inbound message is received as alerted by the MOC, reporting a successful inbound message to the PAP;

and

I. at the PAP, updating a table of expected probabilities of propagation based upon the successful inbound message report.

17. A method as in claim 9 wherein each FAP additionally performs the step of periodically measuring a receive power level in each possible inbound frequency channel.

18. A method as in claim 9, additionally comprising the step of, at the field unit, collect data to be reported including a latitude and longitude from a geolocation system.

19. A method as in claim 9 wherein the short duration inbound message is encoded using spread spectrum modulation.

20. A method as in claim 9 wherein the MOC communicates with the RBSs over a Very Small Aperture Terminal (VSAT) network.