RETURN LINK DESIGN FOR PSD LIMITED MOBILE SATELLITE COMMUNICATION SYSTEMS

• US 20070026795A1
• Filed: 09/28/2006
• Published: 02/01/2007
• Est. Priority Date: 09/28/2000
• Status: Active Grant

• Current Assignee: Michael De La Chapelle
• Original Assignee: Michael De La Chapelle
• Inventors: de La Chapelle, Michael
• Granted Patent: US 7,630,683 B2
• Time in Patent Office: Days
• US Class Current: 455/13.400
• CPC Class Codes: H04B 7/18506 Communications with or from aircraft, i.e. aeronautical mobile service
• CPC Class Codes: H04B 7/18508 with satellite system used as relay, i.e. aeronautical mobile satellite service
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/283 Power depending on the position of the mobile

Abstract

A system and method for managing access to a satellite-based transponder by a plurality of aircraft each having a mobile radio frequency (RF) system. The system employs a ground-based, central control system for managing access to the satellite-based transponder so that the aggregate power spectral density (PSD) of the RF signals of all the mobile systems does not exceed, at any time, limits established by regulatory agencies to prevent interference between satellite systems. This is accomplished by a dual control loop arrangement for monitoring the signal-to-noise ratio (Eb/No) of the RF signal transmitted by the satellite-based transponder. A ground-based control loop is used whereby a ground-based central controller monitors the Eb/No and transmits commands to the aircraft (via the satellite transponder) to maintain the Eb/No of the transmitted signal within a predetermined range. A fast scan angle compensation is used by the mobile system of the aircraft to implement another control loop to further adjust the transmit power. This control loop maintains the Eb/No of the signal transmitted to the satellite-based transponder at the commanded level inbetween updates from the ground-based central controller.

Claims

1. A method of determining a power spectral density (PSD) of a wireless signal from a mobile platform having a communications system in communication with a space-based communications device, said method comprising:

a) estimating, from a location remote to a space-based communications device and remote to said mobile platform, a signal quality value of a wireless signal emanating from an output of said space-based communications device, said wireless signal originating from an antenna of a mobile platform and being transponded by said space-based communications device;

b) using said estimated signal quality value to determine an effective isotropic radiated power (EIRP) value of a signal being radiated from said antenna of said mobile platform, and denoting said EIRP value as a target EIRP; and

c) using said target EIRP to assist in determining said PSD of said wireless signal reaching said space-based communications device.

2. The method of claim 1, wherein operation c) comprises:

using said target EIRP to determine an actual EIRP of said wireless signal reaching a GEO arc within which said space-based communications device resides.

3. The method of claim 2, wherein operation c) comprises:

using said determined actual EIRP to determine said PSD of said wireless signal reaching said GEO arc.

4. The method of claim 1, further comprising:

using a signal pattern of said antenna of said mobile platform in determining said PSD of said signal reaching said GEO arc.

5. The method of claim 1, further comprising:

using a location and an attitude of said mobile platform, reported by said mobile platform to a controller located at said remote location, in determining said PSD.

6. The method of claim 1, wherein said signal quality value of said wireless signal comprises a quotient of energy per bit divided by noise spectral density (Eb/No).

7. The method of claim 6, wherein the operation of using said target EIRP to determine said actual EIRP comprises determining said target EIRP using a formula:

EIRP_t=16π

²d²R(E_b/N_o)(kT+I_o)/(L G_rλ

²)

where;

d=slant range from mobile platform to the space-based communications device;

R=return link data rate;

E_b/N_o=receive Eb/No at the controller;

K=Boltzmann'"'"'s constant;

T=noise temperature of a transponder of the space-based communications device;

I_o=interference noise spectral density;

L=atmospheric plus rain attenuation on uplink from mobile platform to the space-based communications device;

G_r=a receive antenna gain of a receive antenna of said space-based communications device; and

λ

=wavelength of transmission.

8. The method of claim 7, wherein said actual EIRP of said wireless signal from said mobile platform reaching said GEO arc is determined as a function of offset angle θ

along the GEO arc and calculated using a known antenna transmit directivity pattern, G(θ

) for said antenna on the mobile platform.

9. The method of claim 8, wherein said actual EIRP is calculated using a formula:

EIRP_i(θ

)=L EIRP_tG(θ

)/G_t

where “

G_t”

represents a transmit gain of the antenna to the space-based communications device; and

“

L”

represents a loss term.

10. The method of claim 1, further comprising using said actual EIRP and said signal pattern to determine a PSD of said RF signal from said mobile platform at a location off of said Geo arc.

11. A method of determining a power spectral density (PSD) of an electromagnetic (EM) wave signal from a mobile platform reaching a geostationary orbit plane of a satellite transponder with which the mobile platform is using to form a communication link with a remotely located controller, said method comprising:

causing said mobile platform to transmit an EM wave signal to said satellite transponder which is transponded to a remotely located controller;

using said controller to determine a signal quality of said EM wave signal being transponded from an output of said satellite transponder, and received by said controller, wherein said signal quality is represented by a Eb/No (energy per bit/noise spectral density) value of the EM wave signal;

assuming that said Eb/No value of said EM wave signal received at said controller is approximately identical to a Eb/No value of said EM wave emanating from said output of said satellite transponder;

determining an effective isotropic radiated power (EIRP) value of a signal from an antenna of said mobile platform being received by said satellite transponder, as a function of said Eb/No of said EM wave signal being received by said controller, and denoting said EIRP value as a target EIRP;

using said target EIRP to determine an actual EIRP of an EM wave signal reaching a geostationary orbit plane in which said satellite transponder is orbiting; and

using said controller to determine, from said actual EIRP of said EM wave signal reaching said geostationary orbit plane, said PSD of said EM wave signal reaching said geostationary orbit plane.

12. The method of claim 11, further comprising using a signal pattern of said antenna of said mobile platform in determining said PSD of said signal reaching said GEO arc.

13. The method of claim 11, wherein using said controller comprises using a terrestrial based central controller.

14. The method of claim 11, further comprising using a location and an attitude of said mobile platform, reported by said mobile platform to said central controller, in determining said PSD reaching said geostationary orbit plane.

15. The method of claim 14, further comprising determining a total PSD reaching said geostationary arc as a result of EM wave signal transmissions from a plurality of mobile platforms using said satellite transponder.

16. The method of claim 11, wherein the operation of using said target EIRP to determine said actual EIRP comprises determining said target EIRP using a formula:

EIRP_t=16π

²d²R(E_b/N_o)(kT+I_o)/(L G_rλ

²)

where;

d=slant range from the mobile platform to the satellite transponder;

R=return link data rate;

E_b/N_o=receive Eb/No at the controller;

K=Boltzmann'"'"'s constant;

T=noise temperature of a transponder of the satellite transponder;

I_o=interference noise spectral density;

L=atmospheric plus rain attenuation on uplink from mobile platform to the satellite transponder;

G_r=the transponder receive antenna gain; and

λ

=wavelength of transmission.

17. The method of claim 16, wherein said actual EIRP of said EM wave signal from said mobile platform reaching said geostationary orbit plane is determined as a function of offset angle, “

θ

”

, along the geostationary orbit plane and calculated using a known antenna transmit directivity pattern, “

G(θ

)”

for said antenna on the mobile platform.

18. The method of claim 17, wherein said actual EIRP is calculated using a formula:

EIRP_i(θ

)=L EIRP_tG(θ

)/G_t

where “

G_t”

represents a transmit gain of the antenna to the transponded satellite; and

“

L”

represents a loss term.

19. A method for remotely determining an effective isotropic radiated power (EIRP) of an electromagnetic (EM) wave signal being radiated by an antenna of a mobile platform to a geostationary orbit plane of a satellite transponder, wherein the EM wave signal is being transponded by said satellite transponder to a remotely located controller, the method comprising:

a) using a remotely located controller to determine an Eb/No value for said EM wave signal as said EM wave signal is being received by said controller;

b) using said Eb/No value to determine an approximate Eb/No value for said EM wave signal when said EM wave signal is being transmitted from said satellite transponder; and

c) using said controller to determine, from said approximate Eb/No value, an actual effective isotropic radiated power (EIRP) value for said EM wave signal reaching said geostationary orbit plane.

20. The method of claim 19, wherein operation c) further comprises using said controller to remotely determine, using said actual EIRP value, a power spectral density (PSD) of said EM wave signal reaching said geostationary orbit plane.