Providing timing reference for femto cell in wireless communication networks

• US 8,274,947 B1
• Filed: 10/06/2008
• Issued: 09/25/2012
• Est. Priority Date: 10/05/2007
• Status: Active Grant

• Current Assignee: ZTE Corporation
• Original Assignee: ZTE Corporation
• Inventors: Fang, Yonggang, Zhu, Keqiang
• Primary Examiner(s): Wu, Jianye
• Assistant Examiner(s): Russell, Wanda Z
• Application Number:
  US12/246,487
• Time in Patent Office: 1,450 Days
• Field of Search: 370/331, 455/517
• US Class Current: 370/331
• CPC Class Codes: H04B 1/7073 Synchronisation aspects
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

Apparatus, techniques and systems are described for providing timing reference from acquired wireless communication signals of adjacent cells and synchronizing a base station to a network based on such a timing reference without directly relying on a satellite-based timing reference.

Claims

1. A method for providing a timing reference to a femto base station (Femto BS) in wireless communications in a Code Division Multiple Access (CDMA) network, comprising:

operating a CDMA Mobile Station (MS) receiver in the Femto BS to provide receiving functions in the Femto BS;

using the CDMA MS receiver to search and acquire CDMA signals from adjacent cells on at least one CDMA channel in one frequency band;

selecting a CDMA signal from the adjacent cells with Pilot Pseudorandom Noise (PN) Offset of an earliest timing shift to be a timing reference for the Femto BS;

operating the Femto BS to monitor the CDMA signals from adjacent cells in the CDMA network to update the timing reference;

supporting a handoff between cells in the CDMA network and the Femto BS using a virtual Femto BS at a position different from an actual location of the Femto BS by a distance equal to a transmission delay from base station of the cell having the earliest timing shift; and

using the Femto BS to provide timing reference relay so that the Femto BS and one or more other femto base stations form a timing reference network that is synchronized to a single timing source.

2. The method as in claim 1, comprising:

operating the Femto BS to boost its transmit power to help adjacent Femto BS to acquire CDMA timing.

3. The method as in claim 1, comprising:

detecting whether the monitored signal is on the same CDMA channel and band as the Femto BS; and

if the monitored signal is on the same CDMA channel and band as the Femto BS, operating the Femto BS to monitor the CDMA signals from adjacent cells at an idle state of the Femto BS.

4. The method as in claim 1, comprising:

operating the Femto BS to turn off the transmission during the monitoring of the CDMA signals from adjacent cells.

5. The method as in claim 1, comprising:

setting the Femto BS to operate at an operating channel and a frequency band to be different from the operating channel and the frequency band under monitoring by the CDMA MS receiver.

6. A method for providing a timing reference to a femto base station (Femto BS) in wireless communications in a Code Division Multiple Access (CDMA) network, comprising:

operating a CDMA mobile station (MS) receiver in the Femto BS to perform acquisition of CDMA signals from adjacent cells in the CDMA network while turning off a CDMA base station modem in the Femto BS;

turning on and operating the Femto BS modem and associated RF circuitry after the CDMA MS receiver has acquired CDMA signals from adjacent cells; and

processing the acquired CDMA signals from adjacent cells to produce a timing reference for the Femto BS to synchronize with the CDMA network.

7. The method as in claim 6, comprising:

operating CDMA MS receiver to continue monitoring CDMA signals from adjacent cells after the CDMA MS receiver has acquired CDMA signals from adjacent cells and the timing reference is generated; and

adjusting the generated timing reference from the monitored CDMA signals from adjacent cells after the synchronization with the CDMA network based on a previously generated timing reference is lost.

8. A method for providing a timing reference to a femto base station (Femto BS) in wireless communications in a wireless network, comprising:

operating the Femto BS to acquire wireless signals from adjacent cells in the wireless network;

processing the acquired wireless signals from adjacent cells to extract timing information from the acquired wireless signal;

selecting the extracted timing information in one of the acquired wireless signals to be a timing reference for the Femto BS to synchronize with the wireless network, without directly using a timing reference in a satellite-based positioning signal; and

supporting a handoff to and from the Femto BS based on a virtual Femto BS at a position different from an actual location of the Femto BS by a distance equal to a transmission delay from a base station of the one of the acquired wireless signals selected to be the timing reference.

9. The method as in claim 8, wherein the wireless network is a Code Division Multiple Access (CDMA) network.

10. The method as in claim 8, wherein the wireless network is a Wideband Code Division Multiple Access (WCDMA) network.

11. The method as in claim 8, wherein the wireless network is a High-Speed Downlink Packet Access (HSDPA) network.

12. The method as in claim 8, wherein the wireless network is a High-Speed Uplink Packet Access (HSUPA) network.

13. The method as in claim 8, wherein the wireless network is a High Speed Packet Access (HSPA) network.

14. The method as in claim 8, wherein the wireless network is a Ultra Mobile Broadband (UMB) network.

15. The method as in claim 8, wherein the wireless network is a Long Term Evolution (LTE) network.

16. The method as in claim 8, wherein the selected one of the acquired wireless signals is from the closest cell adjacent to the Femto BS.

17. The method as in claim 8, comprising:

operating the Femto BS to turn off the transmission during acquiring the wireless signals from adjacent cells to obtain the timing reference; and

resuming transmission of the Femto BS after the wireless signals from adjacent cells for the timing reference are acquired.

18. The method as in claim 8, wherein the Femto BS is operated to acquire the wireless signals from adjacent cells to obtain the timing reference when there is no communication traffic at the Femto BS.

19. The method as in claim 8, comprising:

operating the Femto BS and one or more other femto base stations to form a timing reference network that is self synchronized to a single timing source.

20. A wireless communication system, comprising:

a radio access network comprising a plurality of base stations to provide radio access to wireless mobile stations, each base station comprising a positioning signal receiver that receives a satellite-based positioning signal that provides a satellite-based timing signal;

a gateway providing communications between the radio access network and a core network; and

a femto base station that provides radio access to wireless mobile stations and is in wireless communications with one or more base stations of the radio access network, the femto base station in communication with the gateway to access the core network,

wherein the femto base station comprises a receiver module that acquires wireless signals from the one or more base stations and one or more other femto base stations, processes the acquired wireless signals to extract timing information from the acquired wireless signal, and selects the extracted timing information in one of the acquired wireless signals to be a timing reference for the femto base station to synchronize with the wireless communication system, without directly using a timing reference in a satellite-based positioning signal.

21. The system as in claim 20, wherein the femto base station comprises:

a mechanism to turn off the transmission of the femto base station for communications with one or more mobile stations during acquiring the wireless signals from to obtain the timing reference and to resume transmission of the femto base station after the wireless signals from adjacent cells for the timing reference are acquired.

22. The system as in claim 20, wherein the femto base station comprises:

A mechanism that controls the femto base station to acquire the wireless signals obtain the timing reference when there is no communication traffic at the femto base station for communicating with one or more mobile stations.