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Researchers Submit Patent Application, "Radio Communication System, Feedback Method, User Terminal, and Radio Base Station Apparatus", for Approval

September 10, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Nagata, Satoshi (Tokyo, JP); Abe, Tetsushi (Tokyo, JP); Kishiyama, Yoshihisa (Tokyo, JP), filed on October 1, 2012, was made available online on August 28, 2014.

The patent's assignee is Ntt Docomo, Inc.

News editors obtained the following quote from the background information supplied by the inventors: "In the UMTS (Universal Mobile Telecommunications System) network, for the purposes of improving spectral efficiency and improving the data rates, system features based on W-CDMA (Wideband Code Division Multiple Access) are maximized by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). For this UMTS network, for the purposes of further increasing high-speed data rates, providing low delay and so on, long-term evolution (LTE) has been under study (non-patent literature 1).

"In the third-generation system, it is possible to achieve a transmission rate of maximum approximately 2 Mbps on the downlink by using a fixed band of approximately 5 MHz. Meanwhile, in the LTE system, it is possible to achieve a transmission rate of about maximum 300 Mbps on the downlink and about 75 Mbps on the uplink by using a variable band which ranges from 1.4 MHz to 20 MHz. Furthermore, in the UMTS network, for the purpose of achieving further broadbandization and higher speed, successor systems of LTE have been under study as well (for example, LTE-Advanced (LTE-A))."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Technical Problem

"Now, as a promising technique for further improving the system performance of the LTE system, there is inter-cell orthogonalization. For example, in the LTE-A system, intra-cell orthogonalization is made possible by orthogonal multiple access on both the uplink and the downlink. That is to say, on the downlink, orthogonalization is provided between user terminal UEs (User Equipment) in the frequency domain. On the other hand, between cells, like in W-CDMA, interference randomization by repeating one-cell frequency is fundamental. So, in the 3GPP (3rd Generation Partnership Project), coordinated multiple-point transmission/reception (CoMP) is under study as a technique for realizing inter-cell orthogonalization. In this CoMP transmission/reception, a plurality of cells are coordinated and perform signal processing for transmission and reception for one user terminal UE or for a plurality of user terminal UEs. For example, for the downlink, simultaneous transmission of a plurality of cells, and coordinated scheduling/beam forming, which adopt precoding, are under study. By adopting these CoMP transmission/reception techniques, improvement of throughput performance is expected, especially with respect to user terminal UEs located on cell edges.

"When CoMP transmission/reception is adopted, radio base station apparatuses that are arranged in a plurality of cells coordinate and transmit data, and therefore a user terminal UE is required to feed back channel state information, from which adequate received quality can be calculated, when CoMP transmission is adopted.

"The present invention has been made in view of the above, and it is therefore an object of the present invention to provide a radio communication system, a feedback method, a user terminal and a radio base station apparatus which make it possible to feed back channel state information, from which adequate received quality can be calculated, when CoMP transmission is adopted.

"Solution to Problem

"A radio communication system according to the present invention is a radio communication system including a plurality of radio base station apparatuses and a user terminal that is configured to be able to communicate with the plurality of radio base station apparatuses, and, in this radio communication system: the radio base station apparatuses include: a transmission section configured to transmit a reference signal for channel state measurement to the user terminal; and a receiving section configured to receive channel state information generated in the user terminal based on the reference signal; and the user terminal includes: a channel state information generating section configured to be able to generate a plurality of pieces of channel state information, including channel state information from which interference from a coordinated cell is cancelled, when the plurality of radio base station apparatuses coordinate and perform transmission; and a transmission section configured to transmit the plurality of pieces of channel state information to the radio base station apparatus.

"A feedback method according to the present invention is a method of feeding back channel state information from a user terminal when a plurality of radio base station apparatuses coordinate and perform transmission, and this method includes the steps in which: a radio base station apparatus transmits a reference signal for channel state measurement to the user terminal; the user terminal generates a plurality of pieces of channel state information, including channel state information from which interference from a coordinated cell is cancelled, based on the reference signal transmitted from the radio base station apparatus; and the user terminal transmits the plurality of pieces of channel state information to the radio base station apparatus.

"A user terminal according to the present invention is a user terminal which is configured to be able to communicate with a plurality of radio base station apparatuses, and this user terminal includes: a receiving section configured to receive a reference signal for channel state measurement from a radio base station apparatus; a channel state information generating section configured to be able to generate a plurality of pieces of channel state information, including channel state information from which interference from a coordinated cell is cancelled, based on the reference signal, when the plurality of radio base station apparatuses coordinate and perform transmission; and a transmission section configured to transmit the plurality of pieces of channel state information to the radio base station apparatus.

"A radio base station apparatus according to the present invention is a radio base station apparatus which is configured to be able to perform coordinated transmission with another radio base station apparatus, for a user terminal, and this radio base station apparatus includes: a transmission section configured to transmit a reference signal for channel state measurement to the user terminal; and a receiving section configured to, upon coordinating with the other radio base station apparatus and performing transmission, receive a plurality of pieces of channel state information, which is generated based on the reference signal and which includes channel state information from which interference from a coordinated cell is cancelled, from the user terminal.

"Technical Advantage of the Invention

"According to the present invention, it is possible to feed back channel state information, from which adequate received quality can be calculated, when CoMP transmission is adopted.

BRIEF DESCRIPTION OF DRAWINGS

"FIG. 1 provides diagrams to explain coordinated multiple point transmission;

"FIG. 2 provides schematic diagrams to show configurations of radio base station apparatuses that are adopted in coordinated multiple point transmission/reception;

"FIG. 3 is a schematic diagram to explain a CQI generation method in a user terminal;

"FIG. 4 provides diagrams to explain CSI-RS allocation patterns in resource blocks;

"FIG. 5 provides diagrams to explain muting in CQI measurement using CSI-RSs;

"FIG. 6 is a diagram to explain radio resources on the uplink;

"FIG. 7 provides schematic diagrams to show CQI transmission timing on the uplink;

"FIG. 8 is a diagram to explain a system configuration of a radio communication system;

"FIG. 9 is a block diagram to show an overall configuration of a radio base station apparatus;

"FIG. 10 is a block diagram to show an overall configuration of a user terminal;

"FIG. 11 is a block diagram to show a configuration of a baseband processing section in a centralized control-type radio base station apparatus;

"FIG. 12 is a block diagram to show a configuration of a baseband processing section in an autonomous distributed control-type radio base station apparatus; and

"FIG. 13 is a block diagram to show a configuration of a baseband signal processing section in a user terminal."

For additional information on this patent application, see: Nagata, Satoshi; Abe, Tetsushi; Kishiyama, Yoshihisa. Radio Communication System, Feedback Method, User Terminal, and Radio Base Station Apparatus. Filed October 1, 2012 and posted August 28, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4176&p=84&f=G&l=50&d=PG01&S1=20140821.PD.&OS=PD/20140821&RS=PD/20140821

Keywords for this news article include: Electronics, Ntt Docomo, Ntt Docomo Inc., Signal Processing.

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Source: Electronics Newsweekly


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