Methods and apparatus of improving inter-sector and/or inter-cell handoffs in a multi-carrier wireless communications system

• US 7,720,479 B2
• Filed: 11/03/2005
• Issued: 05/18/2010
• Est. Priority Date: 10/16/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Lane, Frank A.
• Primary Examiner(s): Nguyen; Duc
• Assistant Examiner(s): Nguyen; Hai V
• Application Number:
  US11/266,643
• Publication Number:
  US 20060052108A1
• Time in Patent Office: 1,657 Days
• Field of Search: 455/436, 455/439
• US Class Current: 455/436
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 5/0042 intra-user or intra-terminal allocation
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 36/08 Reselecting an access point

Abstract

A wireless communications system, e.g., an OFDM system, uses a plurality of carrier frequencies each with an associated frequency band. A base station sector transmitter in the system transmits ordinary signaling, e.g., user data, in its own assigned band. In addition the sector base station transmitter periodically transmits beacon signals into its own frequency band and the frequency bands used by adjacent sector transmitters for their ordinary signaling. Beacon signals, being short duration high power signals with sector transmission power concentrated on one or a few tones, are easily detectable. Each beacon signal may be identified as to the source base station sector transmitter, e.g., based on tone. A mobile node, tuned to a single carrier band, receives a plurality of beacon signals, identifies the sources of the received beacons, compares the received strength of the beacons, and makes handoff decisions, without having to switch carrier band.

Claims

1. A device comprising:

a processor configured to control a base station transmitter to implement a method, the method comprising;

i) transmitting into a first frequency band during a first period of time during which said base station transmitter does not transmit into a second frequency band; and

ii) transmitting into a second frequency band during a second period of time which is shorter than said first period of time, said base station transmitter transmitting into said second frequency band for a period of time which is less than 1/N the period of time said base station transmitter transmits into said first frequency band, where N is a positive value greater than 2, transmitting into the second frequency band during the second period of time including concentrating at least 60 percent of a transmitted power on one or more tones occupying less than one fifth of the second frequency band.

2. The device of claim 1, wherein steps i and ii are repeated over time at periodic intervals such that the amount of time said base station transmitter transmits into said first frequency band remains on average greater than the amount of time it transmits into said second frequency band.

3. The device of claim 1, wherein during said second period of time said base station transmitter does not transmit into said first frequency band.

4. A computer readable medium embodying machine executable instructions for controlling a base station transmitter to implement a method, the method comprising:

i) transmitting into a first frequency band during a first period of time during which said base station transmitter does not transmit into a second frequency band; and

ii) transmitting into a second frequency band during a second period of time which is shorter than said first period of time, said base station transmitter transmitting into said second frequency band for a period of time which is less than 1/N the period of time said base station transmitter transmits into said first frequency band, where N is a positive value greater than 2, transmitting into the second frequency band during the second period of time including concentrating at least 60 percent of a transmitted power on one or more tones occupying less than one fifth of the second frequency band.

5. The computer readable medium of claim 4, wherein steps i and ii are repeated over time at periodic intervals such that the amount of time said base station transmitter transmits into said first frequency band remains on average greater than the amount of time said base station transmitter transmits into said second frequency band.

6. The computer readable medium of claim 4, wherein during said second period of time said base station transmitter does not transmit into said first frequency band.

7. A base station, comprising:

a transmitter configured to transmit signals into a first frequency band and a second frequency band;

a control module configured to control said transmitter to;

i) transmit into a first frequency band during a first period of time during which said first transmitter does not transmit into a second frequency band;

ii) transmit into a second frequency band during a second period of time which is shorter than said first period of time, said transmitter transmitting into said second frequency band for a period of time which is less than 1/N the period of time said transmitter transmits into said first frequency band, where N is a positive value greater than 2, transmitting into the second frequency band during the second period of time including concentrating at least 60 percent of a transmitted power on one or more tones occupying less than one fifth of the second frequency band.

8. The base station of claim 7, wherein during said second period of time said transmitter does not transmit into said first frequency band.

9. The base station of claim 7, wherein said transmitter transmits into said first frequency band at least 20 times as much, in terms of time, as said transmitter transmits into said second frequency band.

10. A base station, comprising:

means for transmitting signals into a first frequency band and a second frequency band;

means for controlling said means for transmitting to;

i) transmit into a first frequency band during a first period of time during which said means for transmitting do not transmit into a second frequency band; and

ii) transmit into a second frequency band during a second period of time which is shorter than said first period of time, said means for transmitting transmitting into said second frequency band for a period of time which is less than 1/N the period of time said means for transmitting transmits into said first frequency band, where N is a positive value greater than 2, transmitting into the second frequency band during the second period of time including concentrating at least 60 percent of a transmitted power on one or more tones occupying less than one fifth of the second frequency band.

11. The base station of claim 10, wherein during said second period of time said means for transmitting does not transmit into said first frequency band.

12. The base station of claim 10, wherein said means for transmitting transmits into said first frequency band at least 20 times as much, in terms of time, as said means for transmitting transmits into said second frequency band.

13. A device operable to control a base station transmitter, comprising:

a processor configured to;

transmit into a first frequency band during a first period of time during which said base station transmitter does not transmit into a second frequency band, said base station transmitter transmitting user data into said first frequency band on a plurality of different tones during said first period of time; and

transmit into a second frequency band during a second period of time which is shorter than said first period of time, said base station transmitter transmitting into said second frequency band for a period of time which is less than 1/N the period of time said base station transmitter transmits into said first frequency band, where N is a positive value greater than 2, said base station transmitter transmitting transmitter information but no user specific data into said second frequency band during said second period of time, said transmitter information being transmitted using at least one tone, said base station transmitter transmitting at least M times an amount of power on said at least one tone than base station transmitter transmits on any one tone used to transmit user data during said first period of time into said first frequency band, where M is a positive integer greater than 2.

14. The device of claim 13, wherein M is at least 5.

15. A computer readable medium embodying machine executable instructions for controlling a base station transmitter to implement a method, the method comprising:

i) transmitting into a first frequency band during a first period of time during which said first base station transmitter does not transmit into a second frequency band, said first base station transmitter transmitting user data into said first frequency band on a plurality of different tones during said first period of time; and

ii) transmitting into a second frequency band during a second period of time which is shorter than said first period of time, said base station transmitter transmitting into said second frequency band for a period of time which is less than 1/N the period of time said base station transmitter transmits into said first frequency band, where N is a positive value greater than 2, said base station transmitter transmitting transmitter information but no user specific data into said second frequency band during said second period of time, said transmitter information being transmitted using at least one tone, said base station transmitter transmitting at least M times an amount of power on said at least one tone than said base station transmitter transmits on any one tone used to transmit user data during said first period of time into said first frequency band, where M is a positive integer greater than 2.

16. The computer readable medium of claim 15, wherein M is at least 5.

17. A base station, comprising:

a transmitter configured to transmit signals into a first frequency band and a second frequency band;

a control module configured to control said first transmitter to;

i) transmit into a first frequency band during a first period of time during which said transmitter does not transmit into a second frequency band, said transmitter transmitting user data into said first frequency band on a plurality of different tones during said first period of time; and

ii) transmit into a second frequency band during a second period of time which is shorter than said first period of time, said transmitter transmitting into said second frequency hand for a period of time which is less than 1/N the period of time said transmitter transmits into said first frequency band, where N is a positive value greater than 2, said transmitter transmitting transmitter information but no user specific data into said second frequency band during said second period of time, said transmitter information being transmitted using at least one tone, said transmitter transmitting at least M times an amount of power on said at least one tone than said transmitter transmits on any one tone used to transmit user data during said first period of time into said first frequency band, where M is a positive integer greater than 2.

18. The base station of claim 17, wherein M is at least 5.

19. A base station, comprising:

means for transmitting signals into a first frequency band and a second frequency band;

means for controlling said means for transmitting to;

transmit into a first frequency band during a first period of time during which said means for transmitting does not transmit into a second frequency band, said means for transmitting transmitting user data into said first frequency band on a plurality of different tones during said first period of time; and

transmit into a second frequency band during a second period of time which is shorter than said first period of time, said means for transmitting transmitting into said second frequency band for a period of time which is less than 1/N the period of time means for transmitting transmits into said first frequency band, where N is a positive value greater than 2, said means for transmitting transmitting transmitter information but no user specific data into said second frequency band during said second period of time, said transmitter information being transmitted using at least one tone, said means for transmitting transmitting at least M times an amount of power on said at least one tone than the means for transmitting transmits on any one tone used to transmit user data during said first period of time into said first frequency band, where M is a positive integer greater than 2.

20. The base station of claim 19, wherein M is at least 5.

21. A device operable to control a base station transmitter, comprising:

a processor configured to;

transmit into a first frequency band during a first period of time during which said base station transmitter does not transmit into a second frequency band; and

transmit into a second frequency band during a second period of time which is shorter than said first period of time, said base station transmitter transmitting into said second frequency band for a period of time which is less than 1/N the period of time said base station transmitter transmits into said first frequency band, where N is a positive value greater than 2, transmitting into a second frequency band during a second period of time including transmitting a tone with at least 20 times an average per tone power used to transmit tones in a preceding 1 second time interval.

22. A computer readable medium embodying machine executable instructions for controlling a base station transmitter to implement a method, the method comprising:

transmitting into a first frequency band during a first period of time during which said base station transmitter does not transmit into a second frequency band; and

transmitting into a second frequency band during a second period of time which is shorter than said first period of time, said base station transmitter transmitting into said second frequency band for a period of time which is less than 1/N the period of time said base station transmitter transmits into said first frequency band, where N is a positive value greater than 2, transmitting into a second frequency band during a second period of time including transmitting a tone with at least 20 times an average per tone power used to transmit tones in a preceding 1 second time interval.

23. A base station, comprising:

a transmitter configured to transmit signals into a first frequency band and a second frequency band;

a control module configured to control said transmitter to;

i) transmit into a first frequency band during a first period of time during which said first transmitter does not transmit into a second frequency band; and

ii) transmit into a second frequency band during a second period of time which is shorter than said first period of time, said transmitter transmitting into said second frequency band tor a period of time which is less than 1/N the period of time said transmitter transmits into said first frequency band, where N is a positive value greater than 2, transmitting into a second frequency band during a second period of time including transmitting a tone with at least 20 times an average per tone power used to transmit tones in a preceding 1 second time interval.

24. A base station, comprising:

means for transmitting signals into a first frequency band and a second frequency band;

means for controlling said first transmitter means to;

transmit into a first frequency band during a first period of time during which said means for transmitting does not transmit into a second frequency band; and

transmit into a second frequency band during a second period of time which is shorter than said first period of time, said means for transmitting transmitting into said second frequency band for a period of time which is less than 1/N the period of time said means for transmitting transmits into said first frequency band, where N is a positive value greater than 2, transmitting into a second frequency band during a second period of time including transmitting a tone with at least 20 times an average per tone power used to transmit tones in a preceding 1 second time interval.

25. A base station comprising:

means for transmitting into a first frequency band during a first period of time during which said base station does not transmit into a second frequency band; and

means for transmitting into a second frequency band during a second period of time which is shorter than said first period of times said base station transmitting into said second frequency band for a period of time which is less than 1/N the period of time said base station transmits into said first frequency band, where N is a positive value greater than 2.

26. The base station of claim 25 wherein said means for transmitting into said first and second frequency bands includes means for transmitting repeatedly over time at periodic intervals such that the amount of time said means for transmitting transmits into said first frequency band remains on average greater than the amount of time said means for transmitting transmits into said second frequency band.

27. The base station of claim 25, wherein during said second period of time said base station does not transmit into said first frequency band.

28. The base station of claim 25 wherein the base station transmits into said first frequency band at least 20 times as much, in terms of time, as compared to transmitting into said second frequency band.

29. The base station of claim 25 wherein said first and second frequency bands are of the same size.

30. The base station of claim 29 wherein said means for transmitting into said second frequency band during a second period of time includes means for concentrating at least 60 percent of a transmitted power on one or more tones occupying less than one fifth of the second frequency band.

31. The base station of claim 29, wherein said means for transmitting into said second frequency band during a second period of time includes means for transmitting a tone with at least 20 times an average per tone power used to transmit tones in a preceding 1 second time interval.

32. The base station of claim 25 further comprising means for operating said base station to transmit into said first frequency band during said second period of time.

33. The base station of claim 25 wherein said means for transmitting into a first frequency band includes means for transmitting user data into said first frequency band on a plurality of different tones.

34. The base station of claim 33, wherein said user data includes at least one of voice, text, and user application data.

35. The base station of claim 33 wherein said means for transmitting into a second frequency band includes means for transmitting transmitter information but no user specific data.

36. The base station of claim 35 wherein said transmitter information includes at least one of cell identification information and sector identification information.

37. The base station of claim 35 wherein said means for transmitting into a second frequency band includes means for transmitting information on fewer tones than the number of tones used to transmit information into said first frequency band.

38. The base station of claim 35 wherein said number of tones used to transmit information into the second frequency band is less than 3.

39. The base station of claim 35 further comprising means for transmitting at least one OFDM signal including at least one complex symbol.

40. The base station of claim 39 wherein said means for transmitting into said second frequency band includes means for transmitting two OFDM symbols.

41. The base station of claim 35 wherein said transmitter information is transmitted using at least one tone, said base station transmits at least M times an amount of power on said at least one tone than any other tone used to transmit user data during said first period of time into said first frequency band, where M is a positive integer greater than 2.

42. The base station of claim 35 wherein said transmitter information is transmitted using at least one tone, said base station transmits said at least one tone using at least 20 times an average per tone power used to transmit tones during a preceding 1 second time interval.

43. The base station of claim 41 wherein M is at least 5.

44. The base station of claim 25 wherein the first period of time includes a plurality of symbol transmission time periods and wherein the second period of time includes fewer symbol transmission time periods than said first period of time.