ENHANCED CELL SCANNING

• US 20090227255A1
• Filed: 08/07/2008
• Published: 09/10/2009
• Est. Priority Date: 03/10/2008
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: THAKARE, Kiran
• Granted Patent: US 8,311,030 B2
• Time in Patent Office: Days
• US Class Current: 455/434
• CPC Class Codes: H04W 48/10 using broadcasted information
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Cell scanning operations are enhanced making them more time and power efficient. A base station communicates with mobile radios in a cellular communication system. The base station transmits in a cell a known symbol sequence over a broadcast channel to permit mobiles to detect and synchronize to the base station. It transmits a time indicator indicating when the base station will transmit service information from which a mobile may determine whether the base station can provide a desired communications service. After a time period associated with the time indicator, the base station transmits the service information. A mobile radio in or near the cell scans for and detects the broadcast signal. A decoder in the mobile decodes the broadcast signal and detects a time period associated with receiving the broadcast information. Based on the time period, the decoder halts further decoding of the broadcast signal. Later, the decoder resumes decoding of the broadcast signal in accordance with the time period and acquires the broadcast information from the broadcast signal.

Claims

1. A method implemented in a base station for communicating with mobile radio devices in a cellular radio communication system, the method comprising:

transmitting in a cell associated with the base station a known symbol sequence over a broadcast channel to permit mobile radios to detect and synchronize to the base station;

transmitting a time indicator indicating when the base station will transmit service information from which a mobile radio may determine whether the base station can provide a desired communications service; and

after a time period associated with the time indicator, transmitting the service information.

2. The method in claim 1, wherein the cellular radio communication system supports one or more IEEE 802.16 standards.

3. The method in claim 1, wherein the service information includes system information and cell-specific information.

4. The method in claim 3, wherein the service information includes a network identifier identifying a network to which the base station belongs, a base station identifier, information for sending uplink communications from a mobile radio to the base station, supported frequency bands, a transmit power profile, and a paging area identifier.

5. The method in claim 1, wherein:

the known symbol sequence is a preamble provided in a frame of information transmitted by the base station,

the frame further includes a frame control header,

each frame includes the preamble and the frame control header,

the time indicator is included in the frame control header.

6. The method in claim 5, wherein only periodic ones of the frames include the service information.

7. The method in claim 6, wherein the service information is included in a downlink charmer descriptor (DCD)/uplink channel descriptor (UCD).

8. The method in claim 7, wherein the time indicator is a DCD/UCD offset defining an offset from a current time to the next time the base station will transmit the DCD/UCD.

9. The method in claim 8, wherein the time indicator includes a bit to indicate whether a DCD/UCD offset is included in the current frame and multiple other bits to define the DCD/UCD offset amount if a DCD/UCD offset is included in the current frame.

10. The method in claim 8, wherein the time indicator includes multiple bits to define the DCD/UCD offset amount if a DCD/UCD offset is included in the current frame.

11. The method in claim 8, wherein the frame control header includes frame number and frame duration information in addition to the DCD/UCD offset.

12. The method in claim 1, wherein the service information is included in a downlink media access protocol (MAP) portion of the frame.

13. The method in claim 12, wherein the service information is included in a synchronization field in the downlink MAP portion of the frame or as a separate information element in the downlink MAP portion of the frame.

14. The method in claim 1, wherein the time indicator is constructed in the base station or a node communicating with the base station.

15. A method implemented in a mobile radio device for communicating in a cellular radio communication system that includes multiple base stations, each base station transmitting system information to multiple mobile radio devices, the method comprising:

scanning for and detecting a broadcast signal from a base station;

decoding the broadcast signal and detecting a time period associated with receiving broadcast information from the base station from which the mobile radio devices may determine whether the base station can provide a desired communications service;

based on the time period, halting further decoding of the broadcast signal; and

resuming decoding of the broadcast signal in accordance with the time period and acquiring the broadcast information from the broadcast signal.

16. The method in claim 15, further comprising:

moving to a battery conserving state for at least a portion of time after halting decoding of the broadcast signal, and

leaving the battery conserving state to a more active state to resume decoding of the broadcast signal at a time when the broadcast information is expected to be received by the mobile radio.

17. The method in claim 15, further comprising:

after halting decoding of the broadcast signal, scanning and detecting one or more other base station signals broadcast by one or more other base stations, and

resuming decoding of the broadcast signal at a time when the broadcast information is expected to be received by the mobile radio.

18. The method in claim 15, further comprising:

selecting one of the base stations to obtain the desired communications service.

19. The method in claim 15, wherein the cellular radio communication system supports one or more IEEE 802.16 standards.

20. The method in claim 15, wherein the service information also includes a network identifier identifying a network to which the base station belongs, a base station identifier, and information for sending uplink communications from a mobile radio to the base station.

21. The method in claim 15, wherein:

the known symbol sequence is provided in a frame of information transmitted by the base station,

the frame further includes a frame control header,

each frame includes the preamble and the frame control header,

the time indicator is included in the frame control header, and

only periodic ones of the frames include the service information.

22. The method in claim 21, wherein the service information is included in a downlink channel descriptor (DCD)/uplink, channel descriptor (UCD) and the time indicator is a DCD/UCD offset defining an offset from a current time to the next time the base station will transmit the DCD/UCD.

23. The method in claim 22, wherein the time indicator includes a bit to indicate whether a DCD/UCD offset is included in the current frame and multiple other bits to define the DCD/UCD offset amount if a DCD/UCD offset is included in the current frame.

24. The method in claim 22, wherein the time indicator includes multiple bits to define the DCD/UCD offset amount if a DCD/UCD offset is included in the current frame.

25. The method in claim 22, wherein the frame control header includes frame number and frame duration information in addition to the DCD/UCD offset.

26. The method in claim 15, wherein the service information is included in a downlink media access protocol (MAP) portion of the frame.

27. The method in claim 26, wherein the service information is included in a synchronization field in the downlink MAP portion of the frame or as a separate information element in the downlink MAP portion of the frame.

28. Apparatus in a base station for communicating with mobile radio devices in a cellular radio communication system, comprising:

a radio transmitter;

control circuitry for providing information to be transmitted by the radio transmitter,

wherein the radio transmitter is configured to;

transmit in a cell associated with the base station a known symbol sequence over a broadcast channel to permit mobile radios to detect and synchronize to the base station;

transmit a time indicator indicating when the base station will transmit service information from which a mobile radio may determine whether the base station can provide a desired communications service and

after a time period associated with the time indicator, transmit the service information.

29. The apparatus in claim 28, wherein the cellular radio communication system supports one or more IEEE 802.16 standards.

30. The apparatus in claim 28, wherein the service information includes a network identifier identifying a network to which the base station belongs, a base station identifier, information for sending uplink communications from a mobile radio to the base station, supported frequency bands, a transmit power profile, and a paging area identifier.

31. The apparatus in claim 28, wherein:

the known symbol sequence is a preamble provided in a frame of information transmitted by the base station,

the frame further includes a frame control header,

each frame includes the preamble and the frame control header,

the time indicator is included in the frame control header,

wherein only periodic ones of the frames include the service information.

32. The apparatus in claim 31, wherein:

the service information is included in a downlink channel descriptor (DCD)/uplink channel descriptor (UCD), and

the time indicator is a DCD/UCD offset defining an offset from a current time to the next time the base station will transmit the DCD/UCD, and

33. The apparatus in claim 31, wherein the time indicator includes a bit to indicate whether a DCD/UCD offset is included in the current frame and multiple other bits to define the DCD/UCD offset amount if a DCD/UCD offset is included in the current frame.

34. The apparatus in claim 31, wherein the time indicator includes multiple bits to define the DCD/UCD offset amount if a DCD/UCD offset is included in the current frame.

35. The apparatus in claim 31, wherein, wherein the frame control header includes frame number and frame duration information in addition to the DCD/UCD offset.

36. The apparatus in claim 28, wherein the service information is included in a downlink media access protocol (MAP) portion of the frame.

37. Apparatus in a mobile radio device for communicating in a cellular radio communication system that includes multiple base stations, each base station transmitting system information to multiple mobile radio devices, the apparatus comprising:

scanning circuitry that scans for and detects a broadcast signal from a base station;

decoding circuitry that decodes the broadcast signal and detects a time indicator associated with receiving broadcast service information from the base station from which the mobile radio devices may determine whether the base station can provide a desired communications service; and

control circuitry configured to halt the decoding circuitry'"'"'s further decoding of the broadcast signal based on the time indicator and to have the decoding circuitry resume decoding of the broadcast signal in accordance with the time indicator and acquiring the broadcast information from the broadcast signal.

38. The apparatus in claim 37, wherein the mobile radio device is battery-operated and the control circuitry is configured to move the mobile radio device into a battery conserving state for at least a portion of time after halting decoding of the broadcast signal and to leave the battery conserving state to enter a more active state to resume decoding of the broadcast signal at a time when the broadcast information is expected to be received by the mobile radio.

39. The apparatus in claim 37, wherein the scanning circuitry is configured to scan and detect one or more other base station signals broadcast by one or more other base stations after halting decoding of the broadcast signal, and

wherein the decoding circuitry is configured to resume decoding of the broadcast signal at a time when the broadcast information is expected to be received by the mobile radio.

40. The apparatus in claim 39, wherein when the mobile radio device is in an active mode, the mobile radio device, after acquiring one or more time indicators, sends a request to a serving base station to align one or more base station scanning interval gaps in transmissions from the serving base station to the mobile radio device with times when scanned base stations are broadcasting broadcast service information.

41. The apparatus in claim 37, wherein the cellular radio communication system supports one or more IEEE 802.16 standards.

42. The apparatus in claim 41, wherein:

the known symbol sequence is provided in a frame of information transmitted by the base station,

the frame further includes a frame control header,

each frame includes the preamble and the frame control header,

the time indicator is included in the frame control header,

the service information is included in a down link channel descriptor (DCD)/uplink channel descriptor (UCD), and

the time indicator is a DCD/UCD offset defining an offset from a current time to the next time the base station will transmit the DCD/UCD.

43. The apparatus in claim 42, wherein the time indicator includes a bit to indicate whether a DCD/UCD offset is included in the current frame and multiple other bits to define the DCD/UCD offset amount if a DCD/UCD offset is included in the current frame.

44. The apparatus in claim 42, wherein the time indicator includes multiple bits to define the DCD/UCD offset amount if a DCD/UCD offset is included in the current frame.

45. The apparatus in claim 42, wherein the frame control header includes frame number and frame duration information in addition to the DCD/UCD offset.

46. The apparatus in claim 37, wherein the service information is included in a downlink media access protocol (MAP) portion of the frame.