BASE STATION AND METHOD OF CALCULATING CORRECTION VALUE

• US 20140233522A1
• Filed: 09/27/2012
• Published: 08/21/2014
• Est. Priority Date: 09/28/2011
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Iwami, Masashi, Tokairin, Takeshi
• Granted Patent: US 9,374,147 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/061 using feedback from receiving side
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 5/0058 Allocation criteria
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

In a base station, a downlink radio resource and an uplink radio resource to be used for transmission of a known signal from a communication terminal are associated for null steering to be performed based on the known signal. A correction value calculating unit calculates a first correction value used to correct a downlink quality value obtained by a communication terminal. The correction value calculating unit calculates a second correction value used to correct a downlink quality value obtained by a communication terminal.

Claims

1. A base station, comprising:

a communication unit that makes communication using a plurality of antennas, the communication unit controlling the transmission directivity of the antennas based on a known signal transmitted from a communication terminal, when performing downlink communication; and

a correction value calculating unit that obtains a correction value used to correct a downlink quality value indicating a downlink communication quality which a communication terminal obtains based on a signal transmitted from said communication unit, wherein

a downlink radio resource and an uplink radio resource to be used for transmission of said known signal from a communication terminal are associated for null steering to be performed based on said known signal,

said correction value calculating unit calculates a first correction value used to correct said downlink quality value obtained by a communication terminal, the first correction value being calculated based on a response signal indicating whether the communication terminal has properly received a signal which said communication unit transmits to this communication terminal using an associated downlink radio resource associated with an uplink radio resource used by this communication terminal for transmission of said known signal, and

said correction value calculating unit calculates a second correction value used to correct said downlink quality value obtained by a communication terminal, the second correction value being calculated based on a response signal indicating whether the communication terminal has properly received a signal which said communication unit transmits to this communication terminal using a nonassociated downlink radio resource not associated with an uplink radio resource used by this communication terminal for transmission of said known signal.

2. The base station according to claim 1, further comprising a scheduling executing unit that makes downlink scheduling of allocating a use downlink radio resource to a communication terminal, the use downlink radio resource being used by said communication unit for downlink communication with the communication terminal,

wherein for said downlink scheduling, said scheduling executing unit uses a downlink communication quality indicated by said downlink quality value corrected with said first correction value as a downlink communication quality at performing downlink communication using said associated downlink radio resource, said scheduling executing unit using a downlink communication quality indicated by said downlink quality value corrected with said second correction value as a downlink communication quality at performing downlink communication using said nonassociated downlink radio resource.

3. The base station according to claim 1, further comprising an MCS determining unit that determines an MCS (modulation and coding scheme) to be applied to a transmission signal to be transmitted from said communication unit, wherein

said MCS determining unit determines, based on said downlink quality value corrected with said first correction value, an MCS to be applied to a transmission signal to be transmitted using said associated downlink radio resource, and

said MCS determining unit determines, based on said downlink quality value corrected with said second correction value, an MCS to be applied to a transmission signal to be transmitted using said nonassociated downlink radio resource.

4. The base station according to claim 1, wherein

said correction value calculating unit updates said first correction value by adding a first adjustment value to or subtracting the first adjustment value from said first correction value,

said correction value calculating unit updates said second correction value by adding a second adjustment value to or subtracting the second adjustment value from said second correction value, and

said second adjustment value is set to be smaller than said first adjustment value.

5. A method of calculating a correction value used to correct a downlink quality value indicating a downlink communication quality, the method being implemented in a base station that makes communication using a plurality of antennas, the base station controlling the transmission directivity of the antennas based on a known signal transmitted from a communication terminal, when performing downlink communication,

in said base station, a downlink radio resource and an uplink radio resource to be used for transmission of said known signal from a communication terminal being associated for null steering to be performed based on said known signal,

the method comprising:

(a) a step of calculating a first correction value used to correct a downlink quality value indicating a downlink communication quality which a communication terminal obtains based on a signal transmitted from said base station, the first correction value being calculated based on a response signal indicating whether the communication terminal has properly received a signal which said base station transmits to this communication terminal using an associated downlink radio resource associated with an uplink radio resource used by this communication terminal for transmission of said known signal; and

(b) a step of calculating a second correction value used to correct said downlink quality value obtained by a communication terminal, the second correction value being calculated based on a response signal indicating whether the communication terminal has properly received a signal which said base station transmits to this communication terminal using a nonassociated downlink radio resource not associated with an uplink radio resource used by this communication terminal for transmission of said known signal.