Wireless communications system, base station, and mobile station

• US 20060126577A1
• Filed: 05/17/2005
• Published: 06/15/2006
• Est. Priority Date: 12/14/2004
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yano, Tetsuya, Obuchi, Kazuhisa, Miyazaki, Shunji
• Granted Patent: US 8,665,839 B2
• Time in Patent Office: Days
• US Class Current: 370/337
• CPC Class Codes: H04B 7/2643 using time-division multiple access [TDMA] H04B7/2615, H04B7/2618 take precedence
• CPC Class Codes: H04B 7/2656 for structure of frame, burst
• CPC Class Codes: H04W 36/0088 Scheduling hand-off measurements
• CPC Class Codes: H04W 36/38 by fixed network equipment
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames

Abstract

A wireless communications system including a mobile station MS and base stations BS1 and BS2, wherein one or both of the mobile station MS and the base stations BS1 and BS2 is provided with a unit for notifying information of a frame position with the possibility of transmission of packets based on detection of deterioration of a reception quality and wherein the mobile station MS is provided with a unit for determining a frame position without the possibility of transmission of packets and shifting to a peripheral cell detection mode at this frame position based on information of a frame position with the possibility of transmission of packets, whereby it is possible to shift to a peripheral cell detection mode without lowering the transmission efficiency and without complicating the processing.

Claims

1. A wireless base station for sequentially transmitting wireless frames containing data addressed to a mobile station selected from among a plurality of mobile stations, comprising:

a detection function unit for detecting a specific mobile station requiring measurement of a received signal from a peripheral cell; and

a control function unit for discontinuously generating wireless frames not containing data for a specific mobile station among sequentially transmitted wireless frames after detection by the detection function unit and including the specific mobile station in candidates of said selection for the wireless frames between discontinuously generated adjacent wireless frames.

2. A wireless base station as set forth in claim 1, wherein said discontinuously generated wireless frames store data addressed to other mobile stations.

3. A wireless base station for sequentially transmitting wireless frames containing data addressed to a mobile station selected from among a plurality of mobile stations, comprising:

a detection function unit for detecting a specific mobile station requiring measurement of a received signal from a peripheral cell;

a notification function unit for notifying the specific mobile station of information enabling identification of discontinuous wireless frames not containing data for the specific mobile station; and

a control function unit for generating discontinuous wireless frames not containing data for the specific mobile station after notification by the notification function unit and including the specific mobile station in said candidates of selection for the wireless frames between the discontinuously generated adjacent wireless frames.

4. A wireless base station as set forth in claim 3, wherein said information which enables identification is information enabling identification of said discontinuous wireless frames based on pre-announcement of transmission of wireless frames containing data addressed to said specific mobile station or information identification of said discontinuous wireless frames based on the wireless frames containing data addressed to said specific mobile station.

5. A mobile station for receiving a wireless signal from a wireless base station sequentially transmitting wireless frames containing data addressed to a mobile station selected from among a plurality of mobile stations, comprising:

an evaluation function unit for receiving and evaluating a wireless signal from a wireless base station different from the above wireless base station in a period of discontinuous wireless frames not containing data for itself generated by the wireless base station when it requires measurement of a received signal from a peripheral cell.

6. A mobile station as set forth in claim 5, wherein:

said mobile station is notified of information enabling identification of said discontinuous wireless frames from said wireless base station.

7. A wireless communications system for packet communications between a mobile station and a base station, wherein:

at least one mobile station and base station is provided with a function unit for notifying a frame position with the possibility of transmission of packets, and

said mobile station is provided with a function unit for shifting to a peripheral cell detection mode at a frame position without the possibility of transmission of packets other than said frame position with the possibility of transmission of packets.

8. A wireless communications system as set forth in claim 7, further provided with a function unit for notifying said frame position with the possibility of transmission of packets by a single signaling between said mobile station and said base station.

9. A wireless communications system as set forth in claim 7, wherein said mobile station is provided with a function unit for determining that a next frame position is a frame position with the possibility of transmission of packets when packet transmission is actually carried out at a frame position with the possibility of transmission of packets determined between said mobile station and said base station, determining that a next frame is a frame without the possibility of transmission of packets when packet transmission is not actually carried out at the frame position with the possibility of transmission of packets, and shifting to the peripheral cell detection mode at the frame without the possibility of transmission of packets.

10. A wireless communications system as set forth in claim 7, wherein at least one of said mobile station and said base station is provided with a function unit for notifying said frame position with the possibility of transmission of packets based on the frame period and the offset value of said packet transmission and making at least one of said frame period and said offset value different for at least one of said mobile station and said base station and notifying the same between said mobile station and said base station.

11. A base station for packet communications with a mobile station, provided with:

a function unit for notifying a frame position with the possibility of transmission of packets to said mobile station and

a control function unit for activating this function unit when it is detected that the reception quality falls to less than a threshold value by reception quality information from said mobile station.

12. A base station as set forth in claim 11, wherein the function unit for notifying said frame position with the possibility of transmission of packets is configured so as to make at least one of a period indicating said frame positions with the possibility of transmission of packets different for the cells or sectors and notifying the same to said mobile station.

13. A base station as set forth in claim 11, further provided with a function unit for making at least one of a period indicating said frame positions with the possibility of transmission of packets and an offset value different for said mobile station and notifying the same.

14. A mobile station for packet communications with a base station, comprising:

a function unit for receiving a signal from said base station, detecting a reception quality thereof, and transmitting a request for shifting to a peripheral cell detection mode to said base station when said reception quality falls to less than a threshold value and

a function unit for determining a frame position without the possibility of transmission of packets from a frame position with the possibility of transmission of packets notified to said base station and shifting to the peripheral cell detection mode at a frame position without the possibility of transmission of packets.

15. A mobile station as set forth in claim 14, further provided with:

a measurement function unit for receiving a signal from said base station and measuring a reception quality thereof;

a function unit for transmitting information of the reception quality measured by the measurement function unit to said base station;

a comparison function unit for comparing said reception quality and the threshold value;

a function unit for transmitting a request for shift to the peripheral cell detection mode to said base station when detecting that said reception quality falls to less than a threshold value by the comparison function unit; and

a function unit for discriminating said frame position without the possibility of transmission of packets according to information of a frame position allowing packet transmission based on the period and offset value notified to said base station and shifting to the peripheral cell detection mode at a frame position without the possibility of transmission of packets.

16. A mobile station as set forth in claim 14, further provided with a function unit for determining that a next frame position is a frame position with the possibility of transmission of packets when packet transmission is actually carried out at a frame position with the possibility of transmission of packets notified to said base station, determining that a next frame position is a frame position without the possibility of transmission of packets when packet transmission is not actually carried out at a frame position with the possibility of transmission of packets, and shifting to the peripheral cell detection mode at a frame position without the possibility of transmission of packets.

17. A mobile station for packet communications with a base station, said mobile station functioning in two modes:

a peripheral cell detection mode and a normal mode, said mobile station comprising;

a function unit for receiving a signal during said normal mode from said base station, detecting a reception quality thereof, and transmitting a request for shifting to said peripheral cell detection mode to said base station when said reception quality falls to less than a threshold value and

a function unit for determining a frame position without the possibility of transmission of packets from a frame position with the possibility of transmission of packets notified to said base station and shifting to said peripheral cell detection mode at a frame position without the possibility of transmission of packets.

18. A mobile station for packet communications requesting handover processing from a first base station employing a first wireless scheme to a second base station employing a second wireless scheme, said mobile station functioning in two modes:

a peripheral cell detection mode and a normal mode, said mobile station comprising;

a function unit for receiving a signal during said normal mode from said first base station, detecting a reception quality thereof, and transmitting a request for shifting to said peripheral cell detection mode to said base station when said reception quality falls to less than a threshold value;

a function unit for determining a frame position without the possibility of transmission of packets from a frame position with the possibility of transmission of packets notified to said first base station and shifting to said peripheral cell detection mode at a frame position without the possibility of transmission of packets, and

wherein, in said peripheral cell detection mode, the mobile station switches from said first wireless scheme to said second wireless scheme to measure the reception quality of said second base station, with handover processing is switched from said first base station to said second base station when the reception quality from the first base station falls to less than the reception quality of the second base station.

19. A method for detecting a peripheral cell without lowering transmission efficiency comprising:

(a) detecting conditions for shifting to a peripheral cell detection mode due to the drop in reception quality in a wireless link between a base station and a mobile station,

(b) communicating information of the base station and the mobile station regarding frames with the possibility of transmission of packets in the peripheral cell detection mode;

(c) acknowledging reception of information in (b);

(d) shifting the mobile station from a normal mode to a peripheral cell detection mode by confirming the acknowledgement; and

(e) monitoring signaling of the original base station and receiving any packets addressed to said mobile station in frames with the possibility of transmission of packets, detecting and measuring a peripheral cell in the peripheral cell detection mode during frames without the possibility of transmission of packets.

20. The method of claim 19, wherein said information in (b) comprises frame period and frame offset value.

21. A handover processing method comprising:

(a) measuring, in a normal mode, a first reception quality from a first base station employing a first wireless scheme;

(b) during a frame position without the possibility of transmission of packets, entering a peripheral cell detection mode and switching from said first wireless scheme to a second wireless scheme associated with a second base station to measure reception quality associated with said second base station; and

(c) requesting handover processing to switch from first base station employing said first wireless scheme to said second base station employing said second wireless scheme when said measured reception quality of said second base station is greater than the measured reception quality of said first base station.