Time and Frequency Synchronization

• US 20130089065A1
• Filed: 05/14/2012
• Published: 04/11/2013
• Est. Priority Date: 10/06/2011
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Koorapaty, Havish, Cheng, Jung-Fu, Frenne, Mattias, Guey, Jiann-Ching, Larsson, Daniel
• Granted Patent: US 9,144,045 B2
• Time in Patent Office: Days
• US Class Current: 370/330
• CPC Class Codes: H04J 11/00 Orthogonal multiplex systems, e.g. using WALSH codesH04J13/00 takes precedence
• CPC Class Codes: H04J 2011/0096 Network synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0057 Physical resource allocation for CQI
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04W 56/001 Synchronization between nodes
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase
• CPC Class Codes: H04W 72/044 based on the type of the allocated resource

Abstract

The scheduling flexibility of CSI reference signals enables time and frequency synchronization using multiple non-zero CSI-RSs transmitted in the same subframe, or using CSI-RSs transmitted in the same subframe with other synchronization signals. Also, multiple synchronization signals may be scheduled in the same subframe to enable fine time and frequency synchronization without cell-specific reference signals.

Claims

1. A method of transmitting reference signals for synchronization in an Orthogonal Frequency Division Multiplexing (OFDM) system, said method comprising:

transmitting a first channel state information (CSI) reference signal in a first slot of a plurality of subframes in accordance with a first configuration of transmission resources, wherein the first configuration of transmission resources defines a first allocation of time and frequency resources for the first CSI reference signal;

transmitting a second CSI reference signal in a second slot of one or more of the plurality of subframes in accordance with a second configuration of transmission resources, wherein the second configuration of transmission resources defines a second allocation of time and frequency resources for the second CSI reference signal, and

wherein transmitting the first CSI reference signal in accordance with the first configuration and transmitting the second CSI reference signals in accordance with the second configuration comprises transmitting the first and second CSI reference signals from the same antenna port in both the first slot and the second slot of at least a first subframe of the plurality of subframes.

2. The method of claim 1 wherein:

transmitting the first CSI reference signal in accordance with the first configuration comprises periodically transmitting the first CSI reference signal in the first slot of two or more subframes with a first repetition frequency; and

transmitting the second CSI reference signal in accordance with the second configuration comprises periodically transmitting the second CSI reference signal in the second slot of two or more of the subframes with a second repetition frequency different from the first repetition frequency.

3. The method of claim 1 wherein:

the first configuration of transmission resources supports transmission of CSI reference signals from a first set of antenna ports;

the second configuration of transmission resources supports transmission of CSI reference signals from a second set of antenna ports;

the first and second sets of antenna ports have a different number of antenna ports; and

the first and second sets of antenna ports include at least one common antenna port for transmission of the first and second CSI reference signals

4. The method of claim 3 wherein the first set of antenna ports has a larger number of antenna ports than the second set, and wherein the repetition frequency of the first CSI reference signal is shorter than the second CSI reference signal.

5. The method of claim 1 further comprising transmitting configuration information for the first and second CSI reference signals to the user terminal on a downlink broadcast channel.

6. A base station in an Orthogonal Frequency Division Multiplexing (OFDM) system, said base station comprising:

a transceiver circuit configured to communicate with a user terminal over a wireless communicate channel; and

a control circuit providing reference signals for transmission to the user terminal via the transceiver circuit, said control circuit being configured to;

transmit a first channel state information (CSI) reference signal in a first slot of one or more subframes;

transmit a second CSI reference signal in a second slot of one or more of the same subframes; and

transmit the first and second CSI reference signals from the same antenna port.

7. The base station of claim 6 wherein the control circuit is further configured to:

periodically transmit the first CSI reference signal in the first slot of the two or more subframes with a first repetition frequency; and

periodically transmit the second CSI reference signal in the second slot of two or more of the subframes with a second repetition frequency different from the first repetition frequency.

8. The base station of claim 7 wherein the control circuit is further configured to:

transmit a first set of CSI reference signals in the first slot from a first set of antenna ports;

transmit a second set of CSI reference signals in the second slot from a second set of antenna ports having a different number of antenna ports from the first set; and

wherein the first and second sets of antenna ports include at least one common antenna port for transmission of the first and second CSI reference signals.

9. The base station of claim 8 wherein the first set of antenna ports has a larger number of antenna ports than the second set, and wherein the repetition frequency of the first set of CSI reference signals is shorter than the second set of CSI reference signals.

10. The base station of claim 7 wherein the control circuit is further configured to transmit configuration information for the first and second CSI reference signals to the user terminal on a downlink broadcast channel.

11. A method of synchronization in an Orthogonal Frequency Division Multiplexing (OFDM) system, said method comprising:

receiving a first channel state information (CSI) reference signal in a first slot of a plurality of subframes in accordance with a first configuration of transmission resources, wherein the first configuration of transmission resources defines a first allocation of time and frequency resources for the first CSI reference signal;

receiving a second CSI reference signal in a second slot of one or more of the plurality of subframes in accordance with a second configuration of transmission resources difference from the first configuration, wherein the second configuration of transmission resources defines a second allocation of time and frequency resources for the second CSI reference signal;

wherein receiving the first CSI reference signal in accordance with the first configuration and receiving the second CSI reference signal in accordance with the second configuration comprises receiving CSI reference signals transmitted on the same antenna port during both the first slot and the second slot of at least a first subframe of the plurality of subframes; and

synchronizing with the OFDM system using the first and second CSI reference signals received during the first subframe.

12. The method of claim 11 wherein:

receiving the first CSI reference signal in accordance with the first configuration of transmission resources comprises periodically receiving the first CSI reference signal in the first slot of the two or more subframes with a first repetition frequency; and

receiving the second CSI reference signal in accordance with the second configuration of transmission resources comprises periodically receiving the second CSI reference signal in the second slot of two or more of the subframes with a second repetition frequency different from the first repetition frequency.

13. The method of claim 12 wherein:

the first configuration of transmission resources supports transmission of CSI reference signals from a first set of antenna ports;

the second configuration of transmission resources supports transmission of CSI reference signals from a second set of antenna ports;

the first and second sets of antenna ports have a different number of antenna ports; and

the first and second sets of antenna ports include at least one common antenna port for receiving of the first and second CSI reference signals.

14. The method of claim 13 wherein the first set of antenna ports has a larger number of antenna ports than the second set, and wherein the repetition frequency of the first set of CSI reference signals is shorter than the second set of CSI reference signals.

15. The method of claim 13 further comprising receiving configuration information for the first and second CSI reference signals on a downlink broadcast channel.

16. A user terminal in an Orthogonal Frequency Division Multiplexing (OFDM) system, said user terminal comprising:

a transceiver circuit configured to communicate with a base station over a wireless communicate channel; and

a control circuit for synchronizing with the OFDM system, said control circuit being configured to;

receive a first channel state information (CSI) reference signal in a first slot of a plurality of subframes in accordance with a first configuration of transmission resources, wherein the first configuration of transmission resources defines a first allocation of time and frequency resources for the first CSI reference signal;

receive a second CSI reference signal in a second slot of one or more of the plurality of subframes in accordance with a second configuration of transmission resources difference from the first configuration, wherein the second configuration of transmission resources defines a second allocation of time and frequency resources for the second CSI reference signal;

receive the first and second CSI reference signals on the same antenna port in at least one of the plurality of subframes; and

synchronize with the OFDM system using the first and second CSI reference signals.

17. The user terminal of claim 16 wherein the control circuit is further configured to:

periodically receive the first CSI reference signal in the first slot with a first repetition frequency; and

periodically receive the second CSI reference signal in the second slot with a second repetition frequency different from the first repetition frequency.

18. The user terminal of claim 16 wherein the control circuit is further configured to:

receive a first set of CSI reference signals in the first slot of two or more subframes from a first set of antenna ports; and

receive the second CSI reference signal in the second slot of two or more of the same subframes with a second repetition frequency different from the first repetition frequency.

19. The user terminal of claim 16 wherein the first set of antenna ports has a larger number of antenna ports than the second set, and wherein the repetition frequency of the first CSI reference signal is shorter than the second CSI reference signal.

20. The user terminal of claim 16 wherein the control circuit is further configured to receive configuration information for the first and second CSI reference signals on a downlink broadcast channel.

21. A method of transmitting reference signals for synchronization in an Orthogonal Frequency Division Multiplexing (OFDM) system, said method comprising:

transmitting a synchronization signal over a first antenna port in a first slot of a plurality of subframes; and

transmitting a CSI reference signal over the first antenna port in a second slot of one or more of the plurality of subframes used for the transmission of the synchronization signal.

22. The method of claim 21 further wherein:

transmitting the synchronization signal comprises periodically transmitting the synchronization signal in the first slot of the plurality of subframes with a first repetition frequency; and

transmitting the CSI reference signal comprises periodically transmitting the CSI reference signal in the second slot of two or more of the subframes with a second repetition frequency different from the first repetition frequency.

23. The method of claim 21 wherein transmitting the CSI reference signal comprises transmitting multiple CSI reference signals over a set of two or more multiple antenna ports including the first antenna port.

24. The method of claim 21 wherein the synchronization signal comprises a secondary synchronization signal.

25. The method of claim 21 further comprising transmitting a control signal including configuration information for the CSI reference signal to the user terminal on a downlink broadcast channel.

26. A base station in an Orthogonal Frequency Division Multiplexing (OFDM) system, said base station comprising:

a transceiver circuit configured to communicate with a user terminal over a wireless communicate channel; and

a control circuit providing reference signals for transmission to the user terminal via the transceiver circuit, said control circuit being configured to;

transmit a synchronization signal in a first slot of one or more subframes;

transmit a CSI reference signal in a second slot of one or more of the same subframes used for the transmission of the synchronization signal; and

transmit the CSI reference signal and the synchronization signal over the same antenna port.

27. The base station of claim 26 wherein the control circuit is further configured to:

periodically transmit the synchronization signal in the first slot with a first repetition frequency; and

periodically transmit the CSI reference signal in the second slot with a second repetition frequency different from the first repetition frequency.

28. The base station of claim 26 wherein the control circuit is further configured to:

transmit the synchronization signal from a first antenna port; and

transmit multiple CSI reference signals a set or two or more multiple antenna ports including the first antenna port.

29. The base station of claim 26 wherein the synchronization signal comprises a secondary synchronization signal.

30. The base station of claim 26 wherein the control circuit is further configured to transmit a control signal including configuration information for the CSI reference signal to the user terminal on a downlink broadcast channel.

31. A method of synchronization in an Orthogonal Frequency Division Multiplexing (OFDM) system, said method comprising:

receiving a synchronization signal that is transmitted over a first antenna port in a first slot of a plurality of subframes;

receiving a CSI reference signal that is transmitted over the first antenna port in a second slot of one or more of the plurality of subframes used for the transmission of the synchronization signal; and

synchronizing with the OFDM system using the CSI reference signal and synchronization signal.

32. The method of claim 31 further wherein:

receiving the synchronization signal comprises periodically receiving the synchronization signal in the first slot with a first repetition frequency; and

receiving the CSI reference signal comprises periodically receiving the CSI reference signal in the second slot with a second repetition frequency different from the first repetition frequency.

33. The method of claim 31 wherein receiving the CSI reference signal comprises receiving multiple CSI reference signals that were transmitted over a set or two or more multiple antenna ports including the first antenna port.

34. The method of claim 31 wherein the synchronization signal comprises a secondary synchronization signal.

35. The method of claim 31 further comprising receiving a control signal including configuration information for the CSI reference signal over a downlink broadcast channel.

36. A user terminal in an Orthogonal Frequency Division Multiplexing (OFDM) system, said base station comprising:

a transceiver circuit configured to communicate with a base station over a wireless communicate channel; and

a control circuit for synchronizing with the OFDM system, said control circuit being configured to;

receive a synchronization signal that is transmitted in a first slot of a plurality of subframes over a first antenna port;

receive a CSI reference signal that is transmitted in a second slot of one or more of the plurality of subframes over the first antenna port; and

synchronize with the OFDM system using the CSI reference signal and synchronization signal.

37. The user terminal of claim 36 wherein the control circuit is further configured to:

periodically receive the synchronization signal in the first slot with a first repetition frequency; and

periodically receive the CSI reference signal in the second slot with a second repetition frequency different from the first repetition frequency.

38. The user terminal of claim 36 wherein the control circuit is further configured to:

receive a first set of synchronization signals in the first slot of one or more subframes over a first set of first antenna ports; and

receive the CSI reference signal in the second slot of one or more of the same subframes from one of said antenna ports in said first set of antenna ports.

39. The user terminal of claim 36 wherein the synchronization signal comprises a secondary synchronization signal.

40. The user terminal of claim 36 wherein the control circuit is further configured to receive a control signal including configuration information for the CSI reference signal over a downlink broadcast channel.

41. A method of transmitting reference signals in an Orthogonal Frequency Division Multiplexing (OFDM) system for synchronizing with a periodic radio frame comprising a plurality of subframes, wherein each of the subframes comprises a plurality of slots, said method comprising:

transmitting a primary synchronization signal in a first subframe of a frame and a second subframe of the frame;

transmitting a first secondary synchronization signal in a first slot of the first subframe over a first antenna port; and

transmitting a second secondary synchronization signal in a second slot of the first subframe over the first antenna port

42. The method of claim 41, wherein:

the primary synchronization signal indicates a physical layer cell identity associated with a base station; and

the first secondary synchronization sequence and the second secondary synchronization signal indicate a cell identity group associated with the base station.

43. The method of claim 41, wherein transmitting the first and the second secondary synchronization signal comprises transmitting the first and the second secondary synchronization signal on a plurality of resource blocks that are contiguous in the frequency domain.

44. The method of claim 41 wherein transmitting the second secondary synchronization signal comprises transmitting the second synchronization signal in the last symbol of the second slot.

45. The method of claim 41 further comprising periodically transmitting the first and second secondary synchronization signals with the same repetition frequency.

46. The method of claim 41 further comprising periodically transmitting the first and second secondary synchronization signals with different repetition frequencies.

47. A base station in an Orthogonal Frequency Division Multiplexing (OFDM) system, said base station comprising:

a transceiver circuit configured to communicate with a user terminal over a wireless communicate channel; and

a control circuit providing reference signals for transmission to the user terminal via the transceiver circuit, said control circuit being configured to;

transmit a primary synchronization signal in a first subframe of a frame and a second subframe of a frame;

transmit a first secondary synchronization signal in a first slot of the first subframe over a first antenna port;

transmit a second secondary synchronization signal in a second slot of the first subframe over the first antenna port; and

transmit the first secondary synchronization signal and the second secondary synchronization signal on the same antenna port.

48. The base station of claim 47 wherein the control circuit is configured to:

transmit the first synchronization signal in the first slot; and

transmit the second synchronization signal in the last symbol of the second slot;

49. The base station of claim 47 wherein the control circuit is configured to periodically transmit the first and second synchronization signals with the same repetition frequency.

50. The base station of claim 47 wherein the control circuit is configured to periodically transmit the first and second synchronization signals with different repetition frequencies.

51. A method of synchronizing, in an Orthogonal Frequency Division Multiplexing (OFDM) system, with a periodic radio frame comprising a plurality of subframes, wherein each of the subframes comprises a plurality of slots, said method comprising:

receiving a primary synchronization signal that is transmitted in a first subframe of a frame and a second subframe of the frame;

receiving a first secondary synchronization signal that is transmitted by a first antenna port in a first slot of the first subframe;

receiving a second secondary synchronization signal that is transmitted by the first antenna port in a second slot of the first subframe; and

synchronizing with the OFDM system using the primary synchronization, the first secondary synchronization signal, and the second secondary synchronization signal.

52. The method of claim 51, wherein:

the primary synchronization signal further indicates a physical layer cell identity associated with a base station; and

the first secondary synchronization sequence and the second secondary synchronization signal further indicate a cell identity group associated with the base station.

53. The method of claim 51, wherein receiving the first and the second secondary synchronization signal comprises receiving the first and the second secondary synchronization signal on a plurality of resource blocks that are contiguous in the frequency domain.

54. The method of claim 51 wherein receiving the second secondary synchronization signal comprises receiving the second secondary synchronization signal in the last symbol of the second slot.

55. The method of claim 51 further comprising periodically receiving the first and second secondary synchronization signals with the same repetition frequency.

56. The method of claim 51 further comprising periodically receiving the first and second secondary synchronization signals with different repetition frequencies.

57. A user terminal in an Orthogonal Frequency Division Multiplexing (OFDM) system, said user terminal comprising:

a transceiver circuit configured to communicate with a base station over a wireless communicate channel; and

a control circuit for synchronizing with the OFDM system, said control circuit being configured to;

receive a primary synchronization signal that is transmitted in a first subframe of a frame and a second subframe of the frame;

receive a first secondary synchronization signal transmitted over a first antenna port in a first slot of the first subframe;

receive a second secondary synchronization signal transmitted over the first antenna port in a second slot of the first subframe;

and

synchronize with the OFDM system using the first and second synchronization signals.

58. The user terminal of claim 57 wherein the control circuit is configured to:

receive the first synchronization signal in the first slot; and

receive the second set of synchronization signal in the last symbol of the second slot.

59. The user terminal of claim 57 wherein the control circuit is configured to periodically receive the first and second synchronization signals with the same repetition frequency.

60. The user terminal of claim 57 wherein the control circuit is configured to periodically receive the first and second secondary synchronization signals with different repetition frequencies.