Wireless terminal methods and apparatus for use in a wireless communications system that uses a multi-mode base station

• US 20070066273A1
• Filed: 09/19/2005
• Published: 03/22/2007
• Est. Priority Date: 09/19/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Das, Arnab, Laroia, Rajiv, Rangan, Sundeep, Anigstein, Pablo
• Granted Patent: US 7,567,791 B2
• Time in Patent Office: Days
• US Class Current: 455/343.200
• CPC Class Codes: H04W 52/0206 in access points, e.g. base stations access point devices per se H04W88/08
• CPC Class Codes: H04W 52/0235 where the received signal is a power saving command
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Wireless terminal for use with a multi-mode base station that supports a transmit standby mode and an active mode is described. Transmit standby mode of base station operation is a low power/low interference level of operation as compared to active mode. In transmit standby mode at least some of the synchronization signaling such as pilot tone signaling is reduced in power level and/or rate with respect to the active mode. In transmit standby mode, the base station has no active state registered wireless terminals being serviced but may have some sleep state registered wireless terminals being serviced. Mode transitions from active to transmit standby may be in response to: a detected period of inactivity, scheduling information, base station mode change signals, and/or detected wireless terminal state transition. Mode transitions from transmit standby to active may be in response to: scheduling information, access signals, wake-up signals from the wireless terminal, hand-off signals, etc.

Claims

1. A method of operating a wireless terminal, the method comprising:

determining if the base station to which the wireless terminal is seeking to establish a user data channel is in a reduced synchronization signaling mode of operation; and

when said wireless terminal determines that said base station is in a reduced synchronization signaling mode of operation, transmitting a signal used to trigger the base station to transition into a more active synchronization signaling mode of operation.

2. The method of claim 1, wherein said determining includes:

receiving synchronization signals from said base station; and

making said determination based on the received synchronization signals.

3. The method of claim 2, wherein said making of said determination based on the received synchronization signals includes evaluating signal power levels to determine a base station mode of operation.

4. The method of claim 3, wherein higher signal power levels are indicative of a full on mode of base station operation than lower signal power levels which are indicative of a reduced synchronization signaling mode of operation.

5. The method of claim 4, wherein said synchronization signals include at least two types of signals and wherein the relative power of the two types of signals is indicative of the base station mode of operation.

6. The method of claim 5, wherein said at least two types of signals includes a first type of signal which is an OFDM beacon signal and a second type of signal which is a pilot tone signal;

and

wherein said beacon signal has a per tone power at least three times the per tone signal power of said pilot tone signal.

7. The method of claim 2, wherein making said determination based on the received synchronization signals includes:

determining a rate at which a first type of synchronization signals are received.

8. The method of claim 7, wherein the first type of synchronization signals are pilot tone signals.

9. The method of claim 7, wherein said base station is determined to be in a reduced synchronization signaling mode of operation when said determined rate is below a predetermined threshold.

10. The method of claim 2, wherein said signal used to trigger the base station to transition into a more active synchronization signaling mode of operation is a wakeup signal.

11. The method of claim 10, wherein said wakeup signal includes less than 5 OFDM tones.

12. The method of claim 11, wherein said wakeup signal is transmitted for a continuous period of time lasting more than one OFDM symbol transmission time period.

13. The method of claim 12, wherein a predetermined set of tones is used for said wakeup signal.

14. The method of claim 13, wherein said predetermined set of tones includes at most one tone.

15. The method of claim 2, wherein said signal used to trigger the base station to transition into a more active synchronization signaling mode of operation is a wakeup signal which is transmitted by said wireless terminal at a per tone power level that is higher than the average per tone power level used by the wireless terminal to transmit user data.

16. The method of claim 15, wherein said wakeup signal is transmitted at the highest per tone power level used by said wireless terminal.

17. The method of claim 2, wherein said signal used to trigger the base station to transition into a more active synchronization signaling mode of operation is an access request signal, and

wherein said wireless terminal operates differently following transmission of the access request signal if the transmission was to a base station in a reduced synchronization mode of signaling operation than if the transmission was to a base station in a full-on mode of synchronization signaling operation.

18. The method of claim 1, wherein said wireless terminal is connected by a wireless link to a current base station located adjacent to said base station;

and

wherein transmitting a signal used to trigger the base station to transition into a more active synchronization signaling mode of operation is transmitted through said current base station as part of a handoff operation.

19. The method of claim 2, wherein said wireless terminal is already registered with said base station and said wireless terminal is in a sleep mode of operation in which said wireless terminal does not transmit user data;

and

wherein said signal used to trigger the base station to transition into a more active synchronization signaling mode of operation is a state transition request signal.

20. A wireless terminal for communicating with a base station which supports a reduced synchronization signaling mode of operation and a full on synchronization mode of operation, the wireless terminal comprising:

a transmitter;

a base station mode determination module for determining if said base station is operating in said reduce synchronization signaling mode of operation; and

a wakeup signal module coupled responsive to said base station mode determination module for controlling said transmitter to transmit a signal used to trigger the base station to transition into a more active synchronization signaling mode of operation.

21. The wireless terminal of claim 20, further comprising:

a receiver for receiving synchronization signals from said base station; and

wherein said base station mode determination module processes received synchronization signals to evaluate at least one of i) synchronization signal power levels and ii) a rate of at least some synchronization signals.

22. The wireless terminal of claim 21, wherein said base station mode determination module includes:

a relative power level determination module for determining the relative power levels of at least two different type of received synchronization signals.

23. The wireless terminal of claim 21, wherein said at least two different types of received synchronization signals are pilot tone signals and OFDM beacon signals.

24. The wireless terminal of claim 21, wherein said base station mode determination module further includes a base station mode decision module for determining the mode of base station operation based on the relative power level of at least two different synchronization signals.

25. The wireless terminal of claim 21, wherein said base station mode determination module determines the mode of base station operation based on the rate of at least one type of synchronization signal;

and

wherein said base station mode determination module includes a rate analysis module for distinguishing between received synchronization signal rates corresponding to different modes of base station operation.

26. The wireless terminal of claim 25, wherein said synchronization signals are pilot tone signals.