User Equipment Adjustment of Uplink Satellite Communications

• US 20110256865A1
• Filed: 04/15/2010
• Published: 10/20/2011
• Est. Priority Date: 04/15/2010
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Inventors: Wilkus, Stephen A., Sayeed, Zulfiquar
• Granted Patent: US 8,538,327 B2
• Time in Patent Office: Days
• US Class Current: 455/427
• CPC Class Codes: H04B 7/18589 Arrangements for controlling an end to end session, i.e. for initialising, synchronising or terminating an end to end link
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time

Abstract

User equipment of a communication system in one aspect obtains data indicative of the position of a satellite, and obtains data indicative of the position of the user equipment. The user equipment computes a delay measure based on the data indicative of the position of the satellite and the data indicative of the position of the user equipment, and adjusts the timing of a communication transmitted from the user equipment to the satellite based on the delay measure. In an illustrative embodiment, the user equipment receives data indicative of position and velocity of the satellite, and adjusts both timing and frequency of the communication based on the position and velocity data. The timing and frequency adjusted communication may then be transmitted to the satellite over a unicast uplink channel.

Claims

1. A method comprising:

obtaining in user equipment data indicative of position of a satellite;

obtaining data indicative of position of the user equipment;

computing a delay measure based on the data indicative of position of the satellite and the data indicative of position of the user equipment; and

adjusting a timing of a communication transmitted from the user equipment to the satellite based on the delay measure.

2. The method of claim 1 wherein the obtaining data indicative of position of a satellite comprises receiving data indicative of position and velocity of the satellite.

3. The method of claim 2 wherein the data indicative of the position and velocity of the satellite comprises ephemeris data given by:

4. The method of claim 3 wherein the ephemeris data is received in the user equipment over a channel other than a unicast downlink channel of the satellite.

5. The method of claim 4 wherein the ephemeris data is received in the user equipment over a broadcast channel of the satellite.

6. The method of claim 3 wherein computing the delay measure comprises computing a measure of distance between the user equipment and the satellite and computing the delay measure based on the distance measure.

7. The method of claim 6 wherein the distance measure is computed as follows:

D<sub>i→

S</sub>(t)=√

{square root over ((X(t)−

X_i)²+(Y(t)−

Y_i)²+(Z(t)−

Z_i)²)}{square root over ((X(t)−

X_i)²+(Y(t)−

Y_i)²+(Z(t)−

Z_i)²)}{square root over ((X(t)−

X_i)²+(Y(t)−

Y_i)²+(Z(t)−

Z_i)²)}

where X_i, Y_i and Z_i denote respective x, y and z coordinates of the position of the user equipment, and X(t), Y(t) and Z(t) denote respective x, y and z coordinates of the position of the satellite.

8. The method of claim 7 wherein adjusting the timing of the communication comprises adjusting the timing by an amount given by:

delay(t)=τ

<sub>i→

S</sub>(t)−

τ

_ref(t)

where τ

_ref(t) is a designated reference delay and τ

<sub>i→

S</sub>(t) is computed as follows;

9. The method of claim 8 wherein the designated reference delay τ

_ref(t) comprises a minimum delay τ

_min(t) that is determined relative to a minimum delay location in a coverage area of the satellite.

10. The method of claim 1 wherein adjusting the timing of the communication comprises adjusting the timing based on the delay measure and another delay measure computed by other user equipment.

11. The method of claim 10 wherein adjusting the timing of the communication comprises adjusting the timing by an amount given by:

Δ

τ

_1,2=τ

<sub>1→

S</sub>−

τ

<sub>2→

S</sub>

where τ

<sub>1→

S</sub> denotes delay between first user equipment and the satellite and τ

<sub>2→

S</sub> denotes delay between second user equipment and the satellite.

12. The method of claim 2 further including the step of adjusting a frequency of the communication transmitted from the user equipment to the satellite based on the data indicative of position and velocity of the satellite.

13. The method of claim 12 wherein adjusting the frequency of the communication comprises adjusting the frequency by an amount given by:

14. The method of claim 12 wherein adjusting the frequency of the communication comprises adjusting the frequency based on a first frequency variation computed by first user equipment and a second frequency variation computed by second user equipment.

15. The method of claim 14 wherein adjusting the frequency of the communication comprises adjusting the frequency by an amount given by:

Δ

f_1,2=Δ

f<sub>1→

S</sub>−

Δ

f<sub>2→

S</sub>

where Δ

f<sub>1→

S</sub> denotes frequency variation between the first user equipment and the satellite and Δ

f<sub>2→

S</sub> denotes frequency variation between the second user equipment and the satellite.

16. The method of claim 1 further comprising transmitting the timing adjusted communication to the satellite over a unicast uplink channel.

17. A computer-readable storage medium having embodied therein executable program code that when executed by a processor of the user equipment causes the user equipment to perform the steps of the method of claim 1.

18. An apparatus comprising:

user equipment configured for communication with a satellite;

the user equipment being operative to obtain data indicative of position of a satellite, to obtain data indicative of position of the user equipment, to compute a delay measure based on the data indicative of position of the satellite and the data indicative of position of the user equipment, and to adjust a timing of a communication transmitted from the user equipment to the satellite based on the delay measure.

19. The apparatus of claim 18 wherein the user equipment comprises:

a processor;

a memory coupled to said processor; and

a network interface adapted for communication with the satellite.

20. An integrated circuit comprising the apparatus of claim 18.