Energy saving functionality for small cells in E-UTRA and E-UTRAN

1. A method comprising:

receiving, by a small cell base station in a wireless network, a switch-off-request message in an active state from a neighboring small cell base station, wherein the switch-off-request message contains a requesting time and a freeze-timeout value;

entering a frozen state, wherein the small cell base station freezes its own switch-off procedure in the frozen state, wherein the small cell base station starts a freeze timer with the freeze-timeout value upon entering the frozen state;

performing frozen-state procedures based on the received switching-off-request message; and

exiting the frozen state upon detecting one or more predefined exit-frozen-state events.

2. The method of claim 1 , wherein the frozen-state procedure involves:

detecting a switch-off condition, wherein the switch-off condition is an amount of traffic of the small cell base station is lower than a predefined low-load-threshold, and wherein the small cell base station switches off radio communications with user equipments (UEs) in the switched-off state;

staying in the frozen state without switching off radio communications with UEs.

3. The method of claim 1 , wherein the frozen-state procedure involves:

monitoring and determining an accept-handoff condition; and

sending a switch-off-acknowledgement message to the neighboring small cell base station before the freeze timer expires if the accept-handoff condition is positive, otherwise staying in the frozen state before the freeze timer expires without sending the switch-off-acknowledge message.

4. The method of claim 1 , wherein the switch-off-request message further comprises a required handoff traffic, and wherein the small cell base station determines an accept-handoff condition based on the switch-off-request and a predefined accept-handoff condition.

5. The method of claim 1 , further comprising:

receiving a load-request message from the neighboring small cell base station, wherein the load-request message informs the small cell base station to prepare for handoff traffic from the neighboring small cell base station; and

performing a handoff procedure with the neighboring small cell based on the load-request message.

6. The method of claim 1 , wherein the exit-frozen-state event is an expiration of the freeze timer.

7. The method of claim 1 , wherein the exit-frozen-state event is detecting a trigger event indicating the completion of a switch-off procedure from the neighboring small cell base station.

8. A method comprising:

receiving a switch-on-request message in a switched-off state by a small cell base station in a wireless network, wherein the switch-on-request message includes a switch-on timer value, and wherein the small cell base station turns off radio communications with user equipments (UEs) in the switched-off state;

broadcasting a switch-on-acknowledge message upon receiving the switch-on-request message, wherein the switch-on-acknowledge message includes an identifier of the small cell base station;

receiving a cell-activation-request message in the switched-off state, wherein the cell-activation-request message is in response to the switch-on-acknowledge message and includes an amount of handoff-traffic; and

performing a switch-on procedure upon receiving the cell-activation-request message, wherein the switch-on procedure involves determining a switch-on condition based the cell-activation-request message using a predefined cost-function, and wherein the cost-function tracks a total amount of handoff-traffic requested from all neighboring cells.

9. The method of claim 8 , wherein the identifier of the small cell base station is an E-UTRAN Cell Global Identifier (ECGI).

10. The method of claim 8 , wherein the switch-on procedure further involves:

switching on the small cell base station if the switch-on condition is positive, otherwise, staying in the switched-off state without switching on the small cell base station.

11. The method of claim 10 , wherein the cost-function further tracks a frequency of switch-on requests from all neighboring small cell base stations.

12. The method of claim 10 , wherein the switch-on condition is positive when the amount of handoff-traffic received by the small cell base station is greater than a predefined switch-on-traffic threshold.

13. A method comprising:

detecting an out-of-range load condition by an active-state small cell base station in a wireless network, wherein the out-of-range load condition is a low-load condition;

sending an energy-saving-request message to one or more neighboring cells based on the load condition, wherein the energy-saving-request message is a switch-off-request message, and wherein the switch-off-request message contains a requesting time and a freeze-timeout value;

receiving one or more response messages from a subset of the neighboring cells;

selecting one or more target cells based on a predefined algorithm and the received one or more response messages; and

sending one or more energy-saving-action messages to the corresponding one or more selected target cells, wherein energy-saving-action message is a load-request message.

14. The method of claim 13 , wherein a neighboring small cell is selected as the target cell if the small cell base station receives the switch-off-acknowledgment message from the neighboring small cell base station.

15. The method of claim 13 , further comprising:

sending a control-measurement message to one or more user equipment (UEs) served by the small cell base station;

receiving one or more measurement-reports messages from each UE served by the small cell base station, wherein the measurement-reports message includes the corresponding UE's traffic load and one or more neighboring cell IDs detected by the corresponding UE;

calculating a required handoff resource based on the one or more measurement-reports message, wherein the required handoff resource is included in the switch-off-request message;

selecting one or more handoff cells based on the detected neighboring cell IDs received from the one or more measurement-reports; and

sending the switch-off-request message to the selected one or more handoff cells.

16. The method of claim 13 , further comprising:

detecting a target-small-cell-fail condition, wherein the small cell base station receives no positive responses from neighboring small cell base stations; and

performing a handoff procedure with an over-lay macro cell base station of the small cell base station.

17. A method comprising:

detecting an out-of-range load condition by an active-state small cell base station in a wireless network;

sending an energy-saving-request message to one or more neighboring cells based on the load condition;

receiving one or more response messages from a subset of the neighboring cells;

selecting one or more target cells based on a predefined algorithm and the received one or more response messages; and

sending one or more energy-saving-action messages to the corresponding one or more selected target cells, wherein the out-of-range load condition is a high-load condition, and wherein the energy-saving-request message is a switch-on-request message, and wherein energy-saving-action message is a cell-activation-request message.

18. The method of claim 17 , wherein the switch-on-acknowledge message includes an identifier of the corresponding neighbor small cell base station that sends the switch-on-acknowledge message.

19. The method of claim 18 , wherein the identifier is an E-UTRAN Cell Global Identifier (ECGI).

20. The method of claim 17 , wherein the target cell is selected based on the identifier.

21. The method of claim 17 , further comprising:

determining an amount of handoff-traffic upon detecting the high-load condition; and

including a required resource information in the cell-activation-request message based on the amount of handoff-traffic.