Alternatives to satellite signals for synchronization in macro network

Patent metadata

Field	Value
Publication number	US-9844014-B2
Application number	US-201414531767-A
Country	US
Kind code	B2
Filing date	Nov 3, 2014
Priority date	Jun 11, 2010
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

Disclosed herein are methods and systems that may help a base station provide high-speed data communication under a protocol such as LTE or WiMAX, even when a GPS signal is not available to the base station. In an exemplary embodiment, a base station may acquire a high-stability reference signal via a subcarrier of a terrestrial broadcast signal, such as an FM radio signal, and may coordinate the timing frame transmissions with other nearby base stations, instead of relying upon a GPS signal for such functionality.

First claim

We claim:

1. A method comprising:
a first base station in a cellular macro network receiving a terrestrial broadcast signal from a broadcast station, wherein the signal comprises a subcarrier signal, and wherein the terrestrial broadcast station has phase-locked the subcarrier signal to a GPS signal;
the first base station decoding the terrestrial broadcast signal to acquire the subcarrier signal;
the first base station using the subcarrier signal to stabilize a local oscillator at the base station, wherein the local oscillator is used by the first base station to maintain signal stability for wireless communications;
the first base station receiving a first signal from a second base station in the macro network, wherein the first signal comprises frames;
the first base station synchronizing a frame-start timing signal with the frames in the first signal;
the first base station determining a time-of-flight delay between the second base station and the first base station;
the first base station adjusting timing of the frame-start timing signal to account for the time-of-flight delay between the second base station and the first base station;
the first base station using the adjusted frame-start signal to determine timing for transmission of frames of a second signal by the first base station; and
the first base station transmitting the second signal, wherein the frames of the second signal are transmitted according to the determined timing.

2. The method of claim 1 , further comprising:
the first base station receiving a plurality of FM radio signals, wherein the terrestrial broadcast signal is one of the plurality of received FM radio signals; and
the first base station using the plurality of received FM radio signals as a basis for determining a geographic location of the first base station.

3. The method of claim 2 , wherein each of the received FM radio signals is broadcast at a certain broadcast frequency by an FM radio station in the given telecommunications market, and wherein using the plurality of received FM radio signals as a basis for determining a geographic location of the first base station comprises:
for each received FM radio signal, determining an angle of arrival of the FM radio signal at the base station;
sending a location request to a network operations center, wherein the location request comprises the broadcast frequency and the determined angle of arrival for each of the FM radio signals; and
receiving a response to the location request from the network operations center, wherein the response indicates the geographic location of the first base station, and wherein the broadcast frequency and the determined angle of arrival for each of the FM radio signals are both used as a basis to determine the geographic location.

4. The method of claim 1 , further comprising:
determining that a GPS signal is unavailable at the first base station; and
perform the method of claim 1 in response to the determination that the GPS signal is unavailable at the first base station.

5. The method of claim 1 , wherein the first base station wirelessly transmits the second signal according to a Long Term Evolution (LTE) protocol.

6. A system of a first base station comprising:
at least one receiver configured to receive a terrestrial broadcast signal, wherein the broadcast signal comprises a subcarrier signal that has been phase-locked to a GPS signal by the terrestrial broadcast station;
a decoder configured to decode the terrestrial broadcast signal to acquire the phase-locked subcarrier signal;
a local oscillator that is operable to stabilize wireless signal transmissions by a base station;
at least one receiver configured to receive a first signal from a second base station in the macro network, wherein the first signal comprises frames;
a non-transitory tangible computer-readable medium; and
program instructions stored on the non-transitory tangible computer-readable medium and executable by at least one processor to cause the core-network entity to:
use the phase-locked subcarrier signal to stabilize the local oscillator;
synchronize a frame-start timing signal with the frames in the first signal;
determine a time-of-flight delay between the second base station and the first base station:
adjust timing of the frame-start timing signal to account for the time-of-flight delay between the second base station and the first base station;
use the adjusted frame-start signal to determine timing for transmission of frames of a second signal from the first base station; and
operate a transmitter of the first base station to transmit the second signal, wherein the frames of the second signal are transmitted according to the determined timing.

7. The system of claim 6 , wherein the at least one receiver configured to receive the terrestrial broadcast signal comprises one or more receivers configured to receive a plurality of FM radio signals, and wherein the terrestrial broadcast signal is one of the plurality of received FM radio signals, the system further comprising:
program instructions stored on the non-transitory tangible computer-readable medium and executable by at least one processor to use the plurality of received FM radio signals as a basis for determining a geographic location of the first base station.

8. The system of claim 7 , wherein each of the received FM radio signals is broadcast at a certain broadcast frequency by an FM radio station in the given telecommunications market, and wherein the program instructions stored on the non-transitory tangible computer-readable medium and executable by at least one processor to use the plurality of received FM radio signals as a basis for determining a geographic location of the first base station comprise program instructions stored on the non-transitory tangible computer-readable medium and executable by at least one processor to:
for each received FM radio signal, determine an angle of arrival of the FM radio signal at the base station;
send a location request to a network operations center, wherein the location request comprises the broadcast frequency and the determined angle of arrival for each of the FM radio signals; and
receive a response to the location request from the network operations center, wherein the response indicates the geographic location of the first base station, and wherein the broadcast frequency and the determined angle of arrival for each of the FM radio signals are both used as a basis to determine the geographic location.

9. The system of claim 6 , wherein the terrestrial broadcast signal comprises an FM radio signal, the system further comprising program instructions stored on the non-transitory tangible computer-readable medium and executable by at least one processor to stabilize the local oscillator by phase-locking the local oscillator to the FM radio signal.

10. The system of claim 9 , wherein the terrestrial broadcast signal comprises an FM radio signal, the system further comprising program instructions stored on the non-transitory tangible computer-readable medium and executable by at least one processor to stabilize the local oscillator by:
phase-locking the local oscillator to the FM radio signal;
periodically receiving phase-error indications, wherein each received phase-error indication indicates phase drift of the FM radio signal; and
using each received phase-error indication to adjust the phase of the local oscillator in order to account for phase drift of the FM radio signal.

11. The system of claim 9 , further comprising program instructions stored in a tangible computer readable medium and executable by at least one processor to:
select a local-osci

Assignees

• Sprint Spectrum Lp

Inventors

• Rausch Walter
• Perlow Harry

Classifications

• H04W72/30

  Resource management for broadcast services · CPC title

• H04H60/50

  of broadcast or relay stations · CPC title

• H04H20/34

  using an out-of-band subcarrier signal · CPC title

• H04H20/18

  Arrangements for synchronising broadcast or distribution via plural systems · CPC title

• H04W56/00

  Synchronisation arrangements · CPC title