FEMTO CELL SYNCHRONIZATION AND PILOT SEARCH METHODOLOGY

• US 20090097452A1
• Filed: 10/09/2008
• Published: 04/16/2009
• Est. Priority Date: 10/12/2007
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gogic, Aleksandar M.
• Application Number:
  US12/248,836
• Publication Number:
  US 20090097452A1
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04B 7/269 Master/slave synchronisation
• CPC Class Codes: H04W 16/32 Hierarchical cell structures
• CPC Class Codes: H04W 56/001 Synchronization between nodes
• CPC Class Codes: H04W 56/004 compensating for timing error of reception due to propagation delay

Abstract

A system, a method and computer product for synchronizing of a femto cell with a macro cell, the method comprising: placing a forward link receiver into the femto cell; receiving by a micro cellular network the femto cell transmission timing; and synchronizing the femto cell transmission timing with the macro cellular network transmission timing in reliance on the forward link receiver signal. Further, a system, a method and computer product for allocating pilot phases to femto cells, the method comprising: creating at least as many new potential pilot phases for femto cells as there are for macro cells; and allowing a mobile device on a macro cell to search and find a femto cell pilot without explicitly listing femto pilot phases in the neighbor list.

Claims

1. A method for synchronizing a femto cell with a macro cell, the method comprising:

receiving the femto cell transmission timing from a macro cell due to a forward link receiver in the femto cell; and

synchronizing the femto cell transmission timing with the macro cell transmission timing in reliance on the forward link receiver signal.

2. The method of claim 1, wherein the forward link receiver implements a zero-IF receiver.

3. The method of claim 1, wherein the forward link receiver permits a fast timing acquisition by a femto cell.

4. The method of claim 1, wherein the forward link receiver assists in determining geographical location of the femto cell.

5. The method of claim 4, wherein the femto cell receiver configuration comprises a high gain antenna, including a steer beam antenna.

6. The method of claim 1, wherein the synchronization timing derived at the femto cell from the macro cell forward link signal is shifted in time due to propagation delay from a macro cell transmitter to the femto cell receiver;

wherein the propagation delay from the macro transmitter to the femto cell receiver is corrected by advancing the synchronization timing at the femto cell accordingly.

7. An apparatus comprising:

a forward link receiver for receiving macro cell transmission timing,

wherein the femto cell synchronizes femto cell transmission timing with the macro cell transmission timing in reliance on the forward link receiver signal.

8. The apparatus of claim 7, wherein the forward link receiver implements a zero-IF receiver.

9. The apparatus of claim 7, wherein the forward link receiver permits a fast timing acquisition of macro cells.

10. The apparatus of claim 7, wherein the forward link receiver assists in determining geographical location of the femto cell.

11. The apparatus of claim 10, wherein the femto cell receiver configuration comprises a high gain antenna, including a steered beam antenna

12. The apparatus of claim 7, wherein the synchronization timing derived at the femto cell from the macro cell forward link signal is shifted in time due to propagation delay from a macro cell transmitter to the femto cell receiver;

wherein the propagation delay from the macro transmitter to the femto cell receiver is corrected by advancing the synchronization timing at the femto cell accordingly.

13. A computer program product, comprising:

a computer-readable medium, comprising;

a first set of codes operable to cause a computer to receive the femto cell transmission timing from a micro cell, due to a forward link receiver in the femto cell; and

a second set of codes operable to cause a computer to synchronize the femto cell transmission timing with the macro cell transmission timing in reliance on the forward link receiver signal.

14. An apparatus for synchronizing a femto cell with a macro cell, the apparatus comprising:

means for receiving the femto cell transmission timing from a macro cell, due to a forward link receiver in the femto cell; and

means for synchronizing the femto cell transmission timing with the macro cell transmission timing in reliance on the forward link receiver signal.

15. The apparatus of claim 14, wherein the forward link receiver implements a zero-IF receiver.

16. The apparatus of claim 14, wherein

the femto cell receiver configuration comprises a high gain antenna;

the said high gain antenna is steerable.

17. The apparatus of claim 14, wherein the forward link receiver permits a fast timing acquisition of femto cells.

18. The apparatus of claim 14, wherein the forward link receiver assists in determining geographical location of the femto cell.

19. The apparatus of claim 14, wherein the synchronization timing derived at the femto cell from the macro cell forward link signal is shifted in time due to propagation delay from a macro cell transmitter to the femto cell receiver, wherein the propagation delay from the macro transmitter to the femto cell receiver is corrected by advancing the synchronization timing at the femto cell accordingly.

20. A method for setting femto cell pilot phases, the method comprising:

dividing 2π

into a plurality macro phase offsets;

inserting a plurality of femto phase offsets among macro phase offsets, wherein each femto phase offset is inserted between two adjacent macro phase offsets; and

creating at least the same number of pilot phase offsets for femto cells as there are for macro cells.

21. The method as set forth in claim 20, wherein creating at least the same number of pilot phase offsets for femto cells as there are for macro cells further comprises decrementing the PILOT_INC while leaving macro phase offsets at even numbered increments of minimum phase spacing thus creating odd-numbered increments of phase spacing for PN Offsets for femto cells.

22. The method as set forth in claim 20, wherein the PILOT_INC is used to manage the size of PN offsets for femto cells as distinct from such phase offsets for macro cells.

23. The method as set forth in claim 20, wherein at a low density of femto cells a subset of odd numbered PN Offsets may be used for femto cells and explicitly included in a neighbor list.

24. The method as set forth in claim 20, wherein at a high density of femto cells a new femto-aware UE will have been fielded and configured to handle a set of femto PN offsets without their explicit inclusion in the neighbor list

25. A apparatus for setting femto cell pilot phases, comprising:

means for dividing 2π

into a plurality macro phase offsets;

means for inserting a plurality of femto phase offsets among macro phase offsets, wherein each femto phase offset is inserted between two neighboring macro phase offsets; and

means for creating at least the same number of pilot phases for femto cells and for macro cells.

26. The apparatus as set forth in claim 25, wherein means for creating at least the same number of pilot phases for femto cells and for macro cells further comprises means for decrementing the PILOT_INC while leaving macro phase offsets at even numbered increments of minimum phase spacing thus creating odd-numbered increments of phase spacing for PN Offsets for femto cells.

27. The apparatus as set forth in claim 25, wherein the PILOT_INC is used to manage the size of PN offsets for femto cells.

28. The apparatus as set forth in claim 25, wherein at a low density of femto cells a subset of odd numbered PN Offsets may be used for femto cells and explicitly included in a neighbor list.

29. The apparatus as set forth in claim 25, wherein at a high density of femto cells a new femto-aware UE will have been fielded and configured to handle a set of femto PN offsets without their explicit inclusion in the neighbor list.

30. An apparatus for setting femto cell pilot phases, comprising:

processor for dividing 2π

into a plurality macro phase offsets, for inserting a plurality of femto phase offsets among macro phase offsets, wherein each femto phase offset is inserted between two neighboring macro phase offsets, and for creating at least the same number of pilot phases for femto cells and for macro cells.

31. A computer-program product, comprising:

computer readable medium comprising codes for causing a computer to;

divide 2π

into a plurality macro phase offsets;

insert a plurality of femto phase offsets among macro phase offsets, wherein each femto phase offset is inserted between two neighboring macro phase offsets; and

create at least the same number of pilot phases for femto cells and for macro cells.

32. The computer-program product as set forth in claim 31, wherein codes for creating at least the same number of pilot phases for femto cells and for macro cells further comprises codes for causing a computer to decrement the PILOT_INC while leaving macro phase offsets at even numbered increments of minimum phase spacing thus creating odd-numbered increments of phase spacing for PN Offsets for femto cells.

33. The computer-program product as set forth in claim 31, wherein the PILOT_INC is used to manage the size of PN offsets for femto cells.

34. The computer-program product as set in claim 31, wherein at a low density of femto cells a subset of odd numbered PN Offsets may be used for femto cells and explicitly included in a neighbor list.

35. The computer-program product as set in claim 31, wherein at a high density of femto cells a new femto-aware UE will have been fielded and configured to handle a set of femto PN offsets without their explicit inclusion in the neighbor list.

36. A method of an idle hand in, the method comprising:

operating a legacy mobile station (“

MS”

) in idle state on a macro cellular network on a frequency on which femto cells are deployed;

detecting by the legacy MS a femto pilot signal of dominant strength;

demodulating a signal from a femto cell in idle mode;

detecting a new femto system network identification;

completing a femto cell selection; and

sending a registration message.

37. The method of claim 36, wherein the method of the idle hand in further comprises:

registering an authorized MS on the femto cell; and

servicing the authorized MS on the femto cell.

38. A computer-program product, comprising:

computer readable medium comprising codes for causing a computer to;

operate a legacy mobile station (“

MS”

) in idle state on a macro cellular network on a frequency on which femto cells are deployed;

detect by the legacy MS a femto pilot signal of dominant strength;

demodulate a signal from a femto cell in idle mode;

detect a new femto system network identification;

complete a femto cell selection; and

send a registration message.

39. The computer-program product of claim 38, wherein codes for the idle hand in further comprises codes for:

registering an authorized MS on the femto cell; and

servicing the authorized MS on the femto cell.

40. A apparatus for an executing an idle hand in, the apparatus comprising:

means for operating a legacy mobile station (“

MS”

) in idle state on a macro cellular network on a frequency on which femto cells are deployed;

means for detecting by the legacy MS a femto pilot signal of dominant strength;

means for demodulating a signal from a femto cell in idle mode;

means for detecting a new femto system network identification;

means for completing a femto cell selection; and

means for sending a registration message.

41. The apparatus of claim 41, wherein the means for the idle hand in further comprises:

means for registering an authorized MS on the femto cell; and

means for servicing the authorized MS on the femto cell.