Carrier search methods and apparatus

• US 7,092,353 B2
• Filed: 10/14/2004
• Issued: 08/15/2006
• Est. Priority Date: 10/17/2003
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Stanski, Charles
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Davis, Cynthia L.
• Application Number:
  US10/964,965
• Publication Number:
  US 20050085214A1
• Time in Patent Office: 670 Days
• Field of Search: None
• US Class Current: 370/210
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0039 Frequency-contiguous, i.e. with no allocation of frequencies for one user or terminal between the frequencies allocated to another
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 48/10 using broadcasted information
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information

Abstract

Transmitting signals, e.g., high power narrow band signals on a periodic basis to facilitate detection of a frequency band and/or carrier signal to be used for communication with a basestation are described. The detected frequency band may be a downlink frequency band. The uplink frequency band to be used can be determined from a know frequency relationship between the detected downlink carrier and a corresponding uplink carrier or by monitoring the detected downlink frequency band for information indicating the uplink frequency band/carrier to be used. Carrier search methods involving searching for the narrowband high power signals used to provide carrier information and/or to indicate the frequency band to be monitored are described. Power detection methods can be used to detect the high power signals avoiding the need for symbol timing synchronization and/or channel estimation with regard to detection of the signals used to locate the frequency band to be used.

Claims

1. A method of operating a plurality of base stations in a communication system, said plurality of base stations including at least a first and a second base station located in different geographic regions, said first base station using a first frequency band, said second base station using a second frequency band which is different from said first frequency band, the method comprising:

operating a first base station transmitter located at said first base station to transmit a plurality of beacon signals during a first time period, said plurality of beacon signals including a beacon signal of a first type and a beacon signal of a second type, said first time period including a fixed number of non-overlapping second time intervals, said step of operating a first base station transmitter to transmit including;

transmitting at least one beacon signal within said first frequency band in each of said second time periods, beacon signals of different types being transmitted on different tones within said first frequency band, a beacon signal of said first type and a beacon signal of said second type being transmitted at least once during said first time period, beacon signals of the first type having at least 10 times the average per tone signal energy of signal tones used to transmit user data during said first time period; and

operating a second base station transmitter located at the second base station to transmit a second plurality of beacon signals during a third time period, said plurality of beacon signals including a beacon signal of said first type and a beacon signal of said second type, said third time period including a fixed number of non-overlapping fourth time periods, said step of operating a second base station transmitter to transmit including;

transmitting at least one beacon signal within said second frequency band in each of said fourth time periods, beacons of different types being transmitted on different tones within said second frequency band, a beacon signal of said first type, and a beacon signal of said second type being transmitted at least once during said third time period.

2. The method of claim 1, wherein said first and second base station transmitters transmit orthogonal frequency division multiplexed (OFDM) signals in parallel on a plurality of tones during said first and third time periods, said first and third time periods including a plurality of at least 10.000 OFDM symbol transmission time periods.

3. The method of claim 1, wherein transmitting at least one beacon signal within said first frequency band in each of said second time periods includes transmitting the first type of beacon signal at most once during said first time period and transmitting said second type beacon signal at least twice during said first time period.

4. The method of claim 1, wherein transmitting at least one beacon signal within said second frequency band in each of said fourth time periods includes transmitting the first type of beacon signal at most once during said third time period and transmitting said second type beacon signal at least twice during said third time period.

5. The method of claim 4, wherein the first and third time periods have the same length.

6. The method of claim 5, wherein the second and fourth time periods have the same length.

7. The method of claim 6, wherein the first and third time periods are ultra slots, said second and fourth time periods are beacon slots, and wherein each beacon slot includes multiple symbol transmission time periods.

8. The method of claim 1,

wherein transmitting at least one beacon signal within said first frequency band in each of said second time periods includes transmitting a beacon signal of a third type at least once during said first time period;

and

wherein transmitting at least one beacon signal within said second frequency band in each of said fourth time periods includes transmitting a beacon signal of said third type at least once during said third time period.

9. The method of claim 8, wherein said first type beacon signal is a carrier beacon signal used to communicate information about the carrier frequency used for downlink communications by the base station transmitter transmitting the carrier beacon signal.

10. The method of claim 9, wherein said second type of beacon signal is a cell type identifier beacon signal which communicates information identifying the cell from which the second type beacon signal is transmitted and wherein said third type of beacon signal is a sector type identifier beacon signal which provides information about a base station sector into which the base station transmitter which transmitted the third type beacon signal transmits.

11. The method of claim 8, further comprising:

repeating said step of operating said first base station transmitter to transmit a plurality of beacon signals during a first period of time during multiple sequential first periods of time; and

repeating said step of operating said first base station transmitter to transmit a plurality of beacon signals during a third period of time during multiple sequential third periods of time, said first and third periods of time overlapping each other.

12. The method of claim 11, wherein each first period of time includes at least 16 of said second periods of time.

13. The method of claim 12, wherein said first and second base station transmitters are not timing synchronized with each other.

14. A method of operating a plurality of base stations in a communication system, said plurality of base stations including at least a first and a second base station located in different geographic regions, said first base station using a first frequency band, said second base station using a second frequency band which is different from said first frequency band, the method comprising:

operating a first base station transmitter located at said first base station to transmit a plurality of beacon signals during a first time period, said plurality of beacon signals including a beacon signal of a first type and a beacon signal of a second type, said first time period including a fixed number of non-overlapping second time intervals, said step of operating a first base station transmitter to transmit including;

transmitting at least one beacon signal within said first frequency band in each of said second time periods, beacon signals of different types being transmitted on different tones within said first frequency band, a beacon signal of said first type and a beacon signal of said second type being transmitted at least once during said first time period; and

operating a second base station transmitter located at the second base station to transmit a second plurality of beacon signals during a third time period, said plurality of beacon signals including a beacon signal of said first type and a beacon signal of said second type, said third time period including a fixed number of non-overlapping fourth time periods, said step of operating a second base station transmitter to transmit including;

transmitting at least one beacon signal within said second frequency band in each of said fourth time periods, beacons of different types being transmitted on different tones within said second frequency band, a beacon signal of said first type, and a beacon signal of said second type being transmitted at least once during said third time period; and

wherein beacon signals of the first type are transmitted using a tone having a fixed frequency offset to a lowest tone in the frequency band in which said first type beacon signal is transmitted, the fixed frequency offset being the same for first type signals transmitted by said first and second base stations, the frequency band in which said first type beacon signal is transmitted being a downlink frequency band.

15. The method of claim 14,

wherein said tone used to transmit first type beacon signals also has a fixed frequency relationship to the tones in an uplink frequency band to be used for communicating information to the base station transmitting said first type beacon signal.

16. The method of claim 15, wherein said uplink and downlink frequency bands are disjoint and separated from one another by more than the spacing between tones an said downlink frequency band.

17. The method of claim 14, wherein said first type beacon signals are transmitted in downlink frequency bands, said first and second frequency bands being downlink frequency bands, the method further comprising:

operating the first base station transmitter to periodically transmit in said first frequency band information indicating the frequency location of an uplink frequency band to be used in transmitting signals to the first base station; and

operating the second base station transmitter to periodically transmit in said second frequency band information indicating the frequency location of an uplink frequency band to be used in transmitting signals to the second base station.

18. The method of claim 14, wherein said first type of beacon signal has a fixed frequency which is lower or higher than all the other types of beacon signals transmitted in the frequency band into which the first type beacon signal is transmitted.

19. A method of operating a plurality of base stations in a communication system, said plurality of base stations including at least a first and a second base station located in different geographic regions, said first base station using a first frequency band, said second base station using a second frequency band which is different from said first frequency band, the method comprising:

operating a first base station transmitter located at said first base station to transmit a plurality of beacon signals during a first time period, said plurality of beacon signals including a beacon signal of a first type and a beacon signal of a second type, said first time period including a fixed number of non-overlapping second time intervals, said step of operating a first base station transmitter to transmit including;

transmitting at least one beacon signal within said first frequency band in each of said second time periods, beacon signals of different types being transmitted on different tones within said first frequency band, a beacon signal of said first type and a beacon signal of said second type being transmitted at least once during said first time period; and

operating a second base station transmitter located at the second base station to transmit a second plurality of beacon signals during a third time period, said plurality of beacon signals including a beacon signal of said first type and a beacon signal of said second type, said third time period including a fixed number of non-overlapping fourth time periods, said step of operating a second base station transmitter to transmit including;

transmitting at least one beacon signal within said second frequency band in each of said fourth time periods, beacons of different types being transmitted on different tones within said second frequency band, a beacon signal of said first type, and a beacon signal of said second type being transmitted at least once during said third time period;

wherein transmitting at least one beacon signal within said first frequency band in each of said second time periods includes transmitting a beacon signal of a third type at least once during said first time period;

wherein transmitting at least one beacon signal within said second frequency band in each of said fourth time periods includes transmitting a beacon signal of said third type at least once during said third time period;

wherein said second type of beacon signal is a cell type identifier beacon signal which communicates information identifying the cell from which the second type beacon signal is transmitted and wherein said third type of beacon signal is a sector type identifier beacon signal which provides information about a base station sector into which the base station transmitter which transmitted the third type beacon signal transmits;

wherein said first type beacon signal uses a fixed tone;

wherein a tone used for said second beacon signal is hopped during said first time period; and

wherein a tone used for said third type beacon signal is also hopped during said first time period.

20. A communication system, comprising:

a plurality of base stations in a communication system, said plurality of base stations including at least a first and a second base station located in different geographic regions,

wherein said first base station uses a first frequency band, the first base station including;

i) a first base station transmitter; and

ii) first transmission control module for controlling said first base station transmitter to transmit a plurality of beacon signals during a first time period, said plurality of beacon signals including a beacon signal of a first type and a beacon signal of a second type, beacon signals of different types being transmitted on different tones within said first frequency band, said first time period including a fixed number of non-overlapping second time intervals, said first transmission control means causing said first base station transmitter to transmit at least one beacon signal within said first frequency band in each of said second time periods, at least one beacon signal of said first type and one beacon signal of said second type being transmitted at least once during each first time period; and

wherein said second base station uses a second frequency band which is different from said first frequency band, the second base station including;

i) a second base station transmitter; and

ii) second transmission control module for controlling said second base station transmitter to transmit a plurality of beacon signals during a third time period, said plurality of beacon signals including a beacon signal of said first type and a beacon signal of said second type, beacon signals of different types being transmitted on different tones within said second frequency band, said second time period including a fixed number of non-overlapping second time intervals, said transmission control means causing said second base station transmitter to transmit at least one beacon signal within said second frequency band in each of said third time periods, at least one beacon signal of said first type and one beacon signal of said second type being transmitted at least once during each third time period; and

wherein said first and second transmitter control modules control the transmission of beacon signals of the first type so that beacon signals of the first type are transmitted using a tone having a fixed frequency offset to a lowest tone in the frequency band in which said first type beacon signal is transmitted, the fixed frequency offset being the same for first type signals transmitted by said first and second base stations.

21. The system of claim 20, wherein said first and second base station transmitters are orthogonal frequency division multiplexed (OFDM) signal transmitters which transmit orthogonal frequency division multiplexed (OFDM) signals in parallel on a plurality of tones during said first and third time periods, said first and third time periods including a plurality of at least 10,000 OFDM symbol transmission time periods.

22. The system of claim 20, wherein the frequency band in which said first type beacon signal is transmitted is a downlink frequency band.

23. The system of claim 22,

wherein said tone used to transmit first type beacon signals also has a fixed frequency relationship to the tones in an uplink frequency band to be used for communicating information to the base station transmitting said first type beacon signal.