Sub-band notification method and terminal apparatus

• US 20070232238A1
• Filed: 06/30/2006
• Published: 10/04/2007
• Est. Priority Date: 03/28/2006
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kawasaki, Yoshihiro
• Granted Patent: US 8,010,049 B2
• Time in Patent Office: Days
• US Class Current: 455/69
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0085 when channel conditions change
• CPC Class Codes: H04L 5/0096 Indication of changes in allocation
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 36/302 due to low signal strength
• CPC Class Codes: H04W 36/362 Conditional handover

Abstract

The present invention relates to a sub band notification method and apparatus in which a terminal notifies a base station of an optimum sub band that is determined based on radio link quality of a plurality of sub bands. The terminal apparatus measures the radio link quality of a current sub band that is currently assigned to it, and the radio link quality of the sub bands on both sides of the current sub band, compares the radio link quality of each sub band, then generates sub-band-change-request data that specifies that the optimum sub band is the sub band having a higher frequency than the current sub band, or the sub band having a lower frequency, and transmits that sub-band-change-request data to the base station.

Claims

1. A sub band notification method for notifying a base station from a terminal of an optimum sub band that is determined based on the radio link quality of a plurality of sub bands, comprising:

a step of measuring the radio link quality of a terminal for a current sub band which is currently assigned to the terminal and for sub bands on both sides of the current sub band;

a step of comparing said line quality of each sub band, and generating sub-band-change-request data that specifies that the optimum sub band is the sub band having a higher frequency than the current sub band, or the sub band having a lower frequency; and

a step of transmitting said sub-band-change-request data to the base station.

2. The sub band notification method of claim 1 further comprising:

a step in which a terminal measures the radio link quality of all sub bands at the start of transmission and determines the sub band having the best quality to be the optimum sub band, then notifies the base station of the ID number of that sub band.

3. The sub band notification method of claim 1 wherein

said sub-band-change-request data comprises 2 bits, and whereby those 2 bits specify whether said optimum sub band is the sub band having a higher frequency than the current sub band, or is the sub band having a lower frequency, or whether to maintain the current sub band as said optimum sub band.

4. The sub band notification method of claim 1 wherein

said sub-band-change-request data comprises 3 bits, and whereby those 3 bits specify whether said optimum sub band is the first or second adjacent sub band having a higher frequency than the current sub band, or is the first or second adjacent sub band having a lower frequency, or whether to maintain the current sub band as said optimum sub band.

5. The sub band notification method of claim 1 or claim 3 further comprising:

a step of specifying by said sub-band-change-request data whether said optimum sub band is the nth adjacent sub band having a higher frequency than the current sub band, or the nth adjacent sub band having a lower frequency, and setting the value of n to a fixed value, or controlling the value of n according to the radio link quality.

6. The sub band notification method of claim 1 comprising:

a step of monitoring whether conditions are met for changing from a first mode to a second mode, in the first mode the radio link quality of the current sub band is compared with that of the sub bands on both sides of the current sub band, and said sub-band-change-request data is transmitted to the base station from the terminal, and in the second mode the radio link quality of all of the sub bands are measured and the base station is notified of the ID number of the sub band having the best radio link quality;

a step of measuring the radio link quality of all sub bands when said conditions are met, and notifying the base station of the ID number of the sub band having the best quality; and

a step of then changing back to said first mode.

7. The sub band notification method of claim 6 comprising

a step of identifying in said second mode the sub band having the best radio link-quality based on the average value of m number of radio link measurements, and setting the value of m to a fixed value, or controlling the value of m according to the radio link quality.

8. The sub band notification method of claim 1 comprising:

a step of determining whether the number of times that sub-band-change-request data has been continuously generated has reached a specified number of times k in a first mode, in which the radio link quality of the current sub band is compared with that of the sub bands on both sides of that sub band, and said sub-band-change-request data is transmitted to the base station from the terminal;

a step of changing from the first mode to a second mode, when the number of times that said sub-band-change-request data has been continuously generated has reached said specified number of times k, measuring the radio link quality for all sub bands in the second mode, and notifying the base station of the ID number of the sub band having the best radio link quality; and

a step of then changing back to said first mode.

9. The sub band notification method of claim 8 comprising

a step of setting the value of k to a fixed value, or controlling the value of k according to the radio link quality.

10. The sub band notification method of claim 1 comprising:

a step of saving the sub-band ID number after the ID number of the sub band having the best radio link quality is received from the terminal, and transmitting data to that terminal using that sub band;

a step of updating said saved optimum sub band based on received data when control data is received from said terminal specifying that the optimum sub band is a sub band having a higher frequency than the current sub band, or a sub band having a lower frequency; and

a step of transmitting data to the terminal using the updated sub band.

11. A terminal apparatus for notifying a base station of an optimum sub band from among a plurality of sub bands that is determined based on radio link quality, and comprising:

a radio-qual ity-measurement unit that measures the radio link quality of current sub band that is currently assigned to the terminal apparatus and the radio link quality of sub bands on both sides of the current sub band;

an optimum-sub-band-determination unit that compares said line quality of each sub band, and determines whether the optimum sub band is the sub band having a higher frequency than the current sub band, or the sub band having a lower frequency; and

a transmission unit that generates sub-band-change-request data based on said determination, and transmits that sub-band-change-request data to the base station.

12. The terminal apparatus of claim 11 further comprising:

a measurement-mode change judgment unit that determines whether conditions are satisfied for changing to a second mode, in the first mode, the radio link quality of the current sub band and the sub bands on both sides of the current sub band are compared and said sub-band-change-request data is transmitted to the base station, and in the second mode the radio link quality for all of the sub bands are measured and the base station is notified of the ID number of the sub band having the best radio link quality, wherein

when said conditions are satisfied, said optimum-sub-band-determination unit refers to the radio link quality of all of the sub bands that are output from said radio-quality-measurement unit, and determines the sub band having the best quality as the optimum sub band, and said transmission unit notifies the base station of the ID number of that sub band.

13. The terminal apparatus of claim 11 comprising:

a measurement-mode change judgment unit for determining whether the number of times that sub-band-change-request data has been continuously generated has reached a specified number of times k in a first mode, in which the radio link quality of the current sub band and the sub bands on both sides of the current sub band are compared and said sub-band-change-request data is transmitted to the base station; and

wherein

when the number of times that said sub-band-change-request data has been generated has reached said specified number of times k, said optimum-sub-band-determination unit changes a mode from the first mode to a second mode, and in the second mode, refers to the radio link quality of all of the sub bands that are output from said radio-quality-measurement unit, and determines the sub band having the best quality as the optimum sub band, and said transmission unit notifies the base station of the ID number of the optimum sub band.

14. The terminal apparatus of claim 12 or claim 13 wherein, when in said second mode said optimum-sub-band-determination unit identifies the sub band having the base quality based on the average value of m number of radio link measurements, a unit is provided for controlling the value of m according to the radio link quality.

15. The terminal apparatus of claim 13 comprising

a unit that controls said value of k according to the radio link quality.

16. A base station apparatus that uses a plurality of sub bands to perform frequency-division-multiplexing transmission for transmitting data to a plurality of terminals, and comprising:

a memory unit that, when a sub-band ID number is received from a terminal as the ID number of the sub band having the best radio link quality, saves said sub-band ID number in correspondence with the terminal;

an update-control unit that, when control data is received from said terminal specifying that the optimum sub band is a sub band having a higher frequency than the current sub band, or is a sub band having a lower frequency, updates said saved optimum sub band based on that received data; and

a data-transmission unit that uses the optimum sub band for each terminal to transmit data to the terminal.