RADIO BASE STATION, USER TERMINAL AND RADIO COMMUNICATION METHOD

• US 20170111874A1
• Filed: 03/13/2015
• Published: 04/20/2017
• Est. Priority Date: 03/19/2014
• Status: Abandoned Application

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Harada, Hiroki, Takeda, Kazuki, Kakishima, Yuichi, Nagata, Satoshi
• Application Number:
  US15/127,168
• Publication Number:
  US 20170111874A1
• Time in Patent Office: Days
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14
• CPC Class Codes: H04L 5/001 the frequencies being arranged in component carriers
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/38 TPC being performed in particular situations
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/0473 the resource being transmission power
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]

Abstract

The present invention is designed to reduce mutual interference and furthermore prevent the decrease of throughput in a radio communication system (LTE-U) to operate LTE in an unlicensed band. A radio base station communicates with a user terminal by using an unlicensed band, and has a detection section that detects signals transmitted from other transmission points in the unlicensed band, a power control section that controls DL transmission power to apply to the unlicensed band based on detection results in the detection section, and a transmission section that transmits signals by using the DL transmission power determined in the power control section, and, in this radio base station, control is executed so that information related to the DL transmission power is reported to the user terminal.

Claims

1. A radio base station that communicates with a user terminal by using an unlicensed band, the radio base station comprising:

a detection section that detects signals transmitted from other transmission points in the unlicensed band;

a power control section that controls DL transmission power to apply to the unlicensed band based on detection results in the detection section; and

a transmission section that transmits signals by using the DL transmission power determined in the power control section,

wherein control is executed so that information related to the DL transmission power is reported to the user terminal.

2. The radio base station according to claim 1, wherein control is executed so that, when the user terminal employs carrier aggregation using the unlicensed band and a licensed band, the information related to the DL transmission power is reported to the user terminal by using downlink control information that is transmitted in the licensed band.

3. The radio base station according to claim 1, wherein the transmission section reports the information related to the DL transmission power to the user terminal by using downlink control information that is transmitted in the unlicensed band, or by using a channel for the information related to the DL transmission power configured in the unlicensed band.

4. The radio base station according to claim 2, wherein DCI format 3/3A is used as a format for the downlink control information.

5. The radio base station according to claim 4, wherein, a bit location for the information related to the DL transmission power, configured in DCI format 3/3A, is reported to the user terminal through higher layer signaling.

6. The radio base station according to claim 4, wherein the detection section performs a detection operation based on an LBT (Listen Before Talk) mechanism, and reports the information related to the DL transmission power, determined in the power control section, to the user terminal, by using DCI format 3/3A of a specific subframe that is associated with the detection operation.

7. The radio base station according to claim 6, wherein the specific subframe associated with the detection operation is a next subframe following the subframe in which the detection operation is performed based on the LBT mechanism.

11. The radio base station according to claim 3, wherein DCI format 3/3A is used as a format for the downlink control information.

12. The radio base station according to claim 11, wherein, a bit location for the information related to the DL transmission power, configured in DCI format 3/3A, is reported to the user terminal through higher layer signaling.

13. The radio base station according to claim 11, wherein the detection section performs a detection operation based on an LBT (Listen Before Talk) mechanism, and reports the information related to the DL transmission power, determined in the power control section, to the user terminal, by using DCI format 3/3A of a specific subframe that is associated with the detection operation.

14. The radio base station according to claim 13, wherein the specific subframe associated with the detection operation is a next subframe following the subframe in which the detection operation is performed based on the LBT mechanism.

8. A user terminal that communicates with a radio base station by using an unlicensed band, the user terminal comprising:

a receiving section that receives a DL signal transmitted from the radio base station; and

a feedback control section that controls feed back of information related to received power to the radio base station, depending on a received power value of the DL signal received, wherein;

the receiving section receives information related to the DL transmission power to apply to the unlicensed band; and

the feedback control section controls an operation of sending a report to the radio base station based on the information related to the DL transmission power.

9. The user terminal according to claim 8, wherein, when the user terminal employs carrier aggregation by using the unlicensed band and a licensed band, the receiving section receives the information related to the DL transmission power by using the licensed band.

10. A radio communication method in a radio base station that communicates with a user terminal in an unlicensed band, the radio communication method comprising the steps of:

detecting signals transmitted from other transmission points in the unlicensed band;

controlling DL transmission power to apply to the unlicensed band based on detection results; and

transmitting signals by using the determined DL transmission power,

wherein control is executed so that information related to the DL transmission power is reported to the user terminal.