APPARATUS AND METHOD FOR OPERATING HIERARCHICAL CELL IN BROADBAND WIRELESS COMMUNICATION SYSTEM

• US 20090252073A1
• Filed: 04/01/2009
• Published: 10/08/2009
• Est. Priority Date: 04/03/2008
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: KWUN, Jong-Hyung, KIM, Yung-Soo
• Granted Patent: US 8,676,220 B2
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: H04W 48/12 using downlink control channel
• CPC Class Codes: H04W 52/0206 in access points, e.g. base stations access point devices per se H04W88/08
• CPC Class Codes: H04W 52/0241 where no transmission is received, e.g. out of range of the transmitter
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

An apparatus and method for operating a hierarchical cell in a wireless communication system are provided. A femto BS transitions into a sleep mode if there is no accessed MS for a predefined time. The femto BS transmits a FEMTO-ADV message in the sleep mode to notify of the presence of the femto BS. The femto BS releases the sleep mode upon receiving a MOB-FEMTO-AWAKE-REQ message from an MS receiving the FEMTO-ADV message. Thereafter, the femto BS communicates with the MS.

Claims

1. A method for an operation of a femto Base Station (BS) in a wireless communication system, the method comprising:

transitioning into a sleep mode if there is no accessed Mobile Station (MS) for a predefined time;

transmitting a FEMTO ADVertisement (FEMTO-ADV) message in the sleep mode to notify of the presence of the femto BS; and

releasing the sleep mode upon receiving a MOBile FEMTO AWAKE REQuest (MOB-FEMTO-AWAKE-REQ) message from an MS that has received the FEMTO-ADV message.

2. The method of claim 1, wherein the transmitting of the FEMTO-ADV message comprises controlling the transmit (TX) power of the FEMTO-ADV message to be substantially equal to at least one of the TX power of a common control channel and a broadcast channel of the femto BS.

3. The method of claim 1, wherein the transmitting of the FEMTO-ADV message comprises transmitting the FEMTO-ADV message periodically through a portion of radio resources of a macro BS.

4. The method of claim 3, wherein the transmitting of the FEMTO-ADV message comprises generating a signal including the FEMTO-ADV message in a substantially same way as generating a signal by the macro BS.

5. The method of claim 4, wherein the FEMTO-ADV message signal comprises at least one of a pilot symbol and a preamble.

6. The method of claim 1, further comprising:

notifying a macro BS of the transition to the sleep mode; and

notifying the macro BS of the release of the sleep mode.

7. A method for an operation of a Mobile Station (MS) in a wireless communication system, the method comprising:

receiving a FEMTO ADVertisement (FEMTO-ADV) message from a femto Base Station (BS) in a macro cell;

transmitting a MOBile FEMTO AWAKE REQuest (MOB-FEMTO-AWAKE-REQ) message to the femto BS upon receiving the FEMTO-ADV message; and

accessing the femto BS.

8. The method of claim 7, wherein the receiving of the FEMTO-ADV message comprises determining whether the FEMTO-ADV message is periodically received through a portion of radio resources of a macro BS.

9. The method of claim 7, wherein the transmitting of the MOB-FEMTO-AWAKE-REQ message comprises:

comparing a accessible Closed Subscriber Group (CSG) identifier list and a CSG identifier included in the FEMTO-ADV message; and

transmitting the MOB-FEMTO-AWAKE-REQ message if the CSG identifier is included in the CSG identifier list.

10. The method of claim 7, further comprising:

estimating a channel between the MS and the femto BS by using at least one of a preamble and a pilot symbol included in a signal comprising the FEMTO-ADV message; and

compensating a channel distortion by using a result of the channel estimation.

11. A method for an operation of a macro Base Station (BS) in a wireless communication system, the method comprising:

allocating a portion of radio resources of the macro BS as a radio resource for transmitting a FEMTO ADVertisement (FEMTO-ADV) message of a femto BS when notified of a sleep mode transition by the femto BS in a macro cell;

prohibiting the use of the radio resource for transmitting the FEMTO-ADV message; and

broadcasting the allocation information of the radio resource for transmitting the FEMTO-ADV message.

12. The method of claim 11, further comprising:

buffering transmit (TX) data destined for a mobile station (MS) when a gap period for transmitting a MOBile FEMTO AWAKE REQuest (MOB-FEMTO-AWAKE-REQ) message is requested from the MS receiving the FEMTO-ADV message; and

transmitting the TX data upon expiration of the gap period.

13. An apparatus for a femto Base Station (BS) in a wireless communication system, the apparatus comprising:

a transmitter for transmitting a FEMTO ADVertisement (FEMTO-ADV) message in a sleep mode to notify of the presence of the femto BS;

a mode determiner for transitioning into the sleep mode if there is no accessed Mobile Station (MS) for a predefined time, and for releasing the sleep mode upon receiving a MOBile FEMTO AWAKE REQuest (MOB-FEMTO-AWAKE-REQ) message from an MS which has received the FEMTO-ADV message; and

a communication controller for communicating with the MS.

14. The apparatus of claim 13, further comprising a power controller for controlling the transmit (TX) power of the FEMTO-ADV message to be substantially equal to at least one of the TX power of a common control channel and a broadcast channel of the femto BS.

15. The apparatus of claim 13, wherein the transmitter transmits the FEMTO-ADV message periodically through a portion of radio resources of a macro BS.

16. The apparatus of claim 15, wherein the transmitter generates a signal including the FEMTO-ADV message in a substantially same way as a signal is generated by the macro BS.

17. The apparatus of claim 16, wherein the FEMTO-ADV message signal comprises at least one of a pilot symbol and a preamble.

18. The apparatus of claim 13, wherein the mode determiner notifies a macro BS of the transition to the sleep mode, and notifies the macro BS of the release of the sleep mode.

19. An apparatus for a Mobile Station (MS) in a wireless communication system, the apparatus comprising:

a receiver for receiving a FEMTO ADVertisement (FEMTO-ADV) message from a femto Base Station (BS) servicing a shadow area in a macro cell;

a transmitter for transmitting a MOBile FEMTO AWAKE REQuest (MOB-FEMTO-AWAKE-REQ) message to the femto BS upon receiving the FEMTO-ADV message; and

a communication controller for accessing the femto BS.

20. The apparatus of claim 19, wherein the receiver receives the FEMTO-ADV message periodically through a portion of radio resources of a macro BS.

21. The apparatus of claim 19, wherein the communication controller compares a stored accessible Closed Subscriber Group (CSG) identifier list and a CSG identifier included in the FEMTO-ADV message, and the transmitter transmits the MOB-FEMTO-AWAKE-REQ message if the CSG identifier is included in the CSG identifier list.

22. The apparatus of claim 19, further comprising:

a channel estimator for estimating a channel between the MS and the femto BS by using at least one of a preamble and a pilot symbol included in a signal comprising the FEMTO-ADV message; and

an equalizer for compensating a channel distortion by using a result of the channel estimation.

23. An apparatus for a macro Base Station (BS) in a wireless communication system, the apparatus comprising:

a resource allocator for allocating a portion of radio resources of the macro BS as a radio resource for transmitting a FEMTO ADVertisement (FEMTO-ADV) message of a femto BS when being notified of a sleep mode transition by the femto BS in a macro cell;

a communication controller for prohibiting use of the radio resource for transmitting the FEMTO-ADV message; and

a transmitter for broadcasting allocation information of the radio resource for transmitting the FEMTO-ADV message.

24. The apparatus of claim 23, wherein the communication controller performs a control operation for buffering transmit (TX) data destined for a mobile station when a gap period for transmitting a MOBile FEMTO AWAKE REQuest (MOB-FEMTO-AWAKE-REQ) message is requested from the MS receiving the FEMTO-ADV message, and transmitting the TX data upon expiration of the gap period.