Method and system for synchronizing a base station of a wireless communication system and a subscriber communication equipment

• US 20070019767A1
• Filed: 06/30/2006
• Published: 01/25/2007
• Est. Priority Date: 07/01/2005
• Status: Active Grant

• Current Assignee: Sequans Communications SA
• Original Assignee: Sequans Communications SA
• Inventors: Buda, Fabien, Lemois, Emmanuel, Debray, Bertrand
• Granted Patent: US 7,706,823 B2
• Time in Patent Office: Days
• US Class Current: 375/355
• CPC Class Codes: H04L 7/0029 interpolation of received data signal

Abstract

The method for synchronising a base station of a wireless communication system and a subscriber communication equipment located in the coverage area of the base station comprises the steps of compensating a sampling frequency offset in the subscriber equipment by interpolating input and/or output signals of a radio frequency part (30) of the communication equipment to generate samples corresponding to the original symbol timing of the base station, and compensating the carrier frequency offset from the estimate of the sampling clock error.

Claims

1. Method for synchronising a base station of a wireless communication system and a subscriber communication equipment located in the coverage area of the base station, characterised in that it comprises the steps of compensating a sampling frequency offset in the subscriber equipment by interpolating input and/or output signals of a radio frequency part (30) of the communication equipment to generate samples corresponding to the original symbol timing of the base station, and compensating a carrier frequency offset from the estimate of the sampling clock error.

2. Method according to claim 1, characterised in that the steps of compensating the carrier frequency offset are carried out by generating control signal and providing the radio frequency part (30) of the subscriber communication equipment with said control signals.

3. Method according to claim 1, characterised in that the sampling frequency in the subscriber equipment is adjusted to the original symbol timing using a feedback loop (50), and in that frequency error (X) between master clock frequency on the subscriber equipment side and the master clock frequency on the base station side is estimated from the increment value of a numerically controlled oscillator (NCO) of the feed back loop.

4. Method according to claim 3, characterised in that the frequency error is estimated from the relation:

$\frac{\mathrm{NCOIncr}}{{\mathrm{NCOIncr}}_{\mathrm{theory}}}=1+\hat{X}$

with;

$\left(1+X\right)=\left(\frac{F_{\mathrm{BS}}+\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>F_{\mathrm{SS}/\mathrm{BS}}}{F_{\mathrm{BS}}}\right)$

and in which;

F_BS is the base station master clock frequency;

Δ

_FSS/BS is a subscriber equipment master clock offset with respect to the base station;

X is subscriber master clock error with respect to base station (expressed in parts per million) and {circumflex over (X)} is its estimate;

NCOIncr_Theory is the theoretical increment of the numerically controlled oscillator; and

NCOIncr is the measured increment of the numerically controlled oscillator

5. Method according to claim 3, characterised in that it further comprises the step of calculating the downlink carrier frequency by the subscriber equipment from its master clock frequency error.

6. Method according to claim 5, characterised in that the downlink carrier frequency is calculated from the relation:

${\mathrm{DLFrequency}}_{\mathrm{SS}}=\frac{1}{1+\hat{X}}<br><br>\mathrm{DLFrequency}$

in which DLFrequency denotes the downlink carrier frequency of the subscriber equipment.

7. Method according to claim 5, characterised in that the uplink carrier frequency is calculated from the relation:

${\mathrm{ULFrequency}}_{\mathrm{SS}}=\frac{1}{1+\hat{X}}<br><br>\mathrm{ULFrequency}$

in which ULFrequency denotes the uplink carrier frequency of the subscriber equipment.

8. Method according to claim 6, characterised in that the computed carrier frequency is divided into a coarse carrier frequency applied to the radio frequency part (30) of the subscriber communication and a fine carrier frequency applied to a digital rotator (46) used to compensate the carrier offset in addition to said radio frequency part.

12. Method according to claim 2, characterised in that the sampling frequency in the subscriber equipment is adjusted to the original symbol timing using a feedback loop (50), and in that frequency error (X) between master clock frequency on the subscriber equipment side and the master clock frequency on the base station side is estimated from the increment value of a numerically controlled oscillator (NCO) of the feed back loop.

13. Method according to claim 4, characterised in that it further comprises the step of calculating the downlink carrier frequency by the subscriber equipment from its master clock frequency error.

14. Method according to claim 7, characterised in that the computed carrier frequency is divided into a coarse carrier frequency applied to the radio frequency part (30) of the subscriber communication and a fine carrier frequency applied to a digital rotator (46) used to compensate the carrier offset in addition to said radio frequency part.

9. Device for synchronising a base station of a wireless communication system and a subscriber communication equipment located in the coverage area of the base station, characterised in that it comprises an interpolator (48) for interpolating input and/or output signals of a radio frequency part of the communication equipment to generate samples corresponding to the original symbol timing of the base station, and calculating means (51) for compensating the carrier frequency offset from the estimate of the sampling clock error.

10. Device according to claim 9, characterised in that it further comprises an feedback loop (50) for controlling timing of the interpolator to compensate sampling frequency offset, said feedback loop having a numerically controlled oscillator, and in that calculating means (51) comprise means for estimating a frequency error (X) between a master clock frequency on the subscriber equipment side and a master clock frequency on the base station side from the value of the numerically controlled oscillator.

11. Wireless telecommunication equipment, characterised in that it comprise a device for synchronising a base station of a wireless communication system and the wireless telecommunication equipment when located in the coverage area of the base station according to claim 9.

15. Wireless telecommunication equipment, characterised in that it comprise a device for synchronising a base station of a wireless communication system and the wireless telecommunication equipment when located in the coverage area of the base station according to claim 10.