(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(19) World Intellectual Property Organization __
`International Bureau
`
`I ‘
`
`(43) International Publication Date
`16 July 2009 (16.07.2009)
`
`(51) International Patent Classification:
`[1043 7/02 (2006.01)
`
`(21) International Application Number:
`PCT/KR2009/000084
`
`(22) International Filing Date:
`
`8 January 2009 (08.01.2009)
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`English
`
`English
`
`(30) Priority Data:
`61/019, 843
`10-2008-0135367
`
`8 January 2008 (08.01.2008)
`
`29 December 2008 (29.12.2008)
`
`US
`
`KR
`
`(71) Applicant (for all designated States except US): LG
`ELECTRONICS INC.
`[KR/KR]; 20, Yeouido-dong,,
`Yeongdeungpo-gu, Seoul 150-721 (KR).
`
`(72) Inventors; and
`(75) Inventors/Applicants (for US only): LEE, Moon H
`[KR/KR]; LG Institute, Hogye 1(il)-dong,, Dongan-gu,
`Anyang-si,, Gyeonggi-do 431-080 (KR). CHUNG, Jae
`
`(10) International Publication Number
`
`WO 2009/088225 A2
`
`Hoon [KR/KR]; LG Institute, Hogye 1(il)-dong,, Don-
`gan-gu, Anyang-si,, Gyeonggi-do 431-080 (KR). KWON,
`Yeong Hyeon [KR/KR]; LG Institute, Hogye 1(il)-dong,,
`Dongan—gu, Anyang-si,, Gyeonggi-do 431-080 (KR).
`
`Agent: KIIVI, Yong In; KBK & Associates, 7th Floor,
`Hyundae Building, 175-9, Jamsil-dong, Songpa-ku, Seoul
`138-861 (KR).
`
`Designated States (unless otherwise indicated, for eveiy
`kind of national protection available): AE, AG, AL, AM,
`AO, AT, AU, AZ, BA, BB, BG, BH, BR, BW, BY, BZ, CA,
`CH, CN, CO, CR, CU, CZ, DE, DK, DM, DO, DZ, EC, EE,
`EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID,
`IL, IN, IS, JP, KE, KG, KM, KN, KP, KZ, LA, LC, LK, LR,
`LS, LT, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX,
`MY, MZ, NA, NG, NI, NO, NZ, OM, PG, PH, PL, PT, RO,
`RS, RU, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TJ, TM,
`TN, TR, Tl‘, TZ,, LIA, UG, US, UZ, VC, VN, ZA, ZM, ZW.
`
`Designated States (unless otherwise indicated, for eveiy
`kind of regional protection available): ARIPO (BW, GH,
`GM, KE, LS, MW, MZ, NA, SD, SL, SZ, TZ, UG, ZM,
`ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM),
`European (AT, BE, BG, CII, CY, CZ, DE, DK, EE, ES, FI,
`
`[Continued on next page]
`
`(54) Title: METHOD FOR TRANSMITTING AND RECEIVING CHANNEL STATE INFORMATION PERIODICALLY OR
`APERIODICALLY
`
`FIG. 4
`
`[Apetiodic PUSCH feedback]
`
`UL Grant
`(CQI Reguest)
`
`S402
`
`CQI/PMI/RI using PUSCH
`
`Subframe 11
`
`SubIiameln+4
`
`(57) Abstract: A method for transmitting and receiving channel state information (CSI) periodically and aperiodically is disclosed.
`The method for aperiodically transmitting channel state information (CSI) by a terminal includes receiving an indicator requesting
`a channel state information report of a downlink channel from a base station over a downlink control channel, and aperiodically
`transmitting the channel state information (CSI) to the base station over a physical uplink shared channel (PUSCH) upon receiving
`the indicator from the base station.
`
`N <
`
`3
`In
`
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`Published:
`FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MK,
`MT, NL, NO, PL, PT, RO, SE, SI, SK, TR), OAPI (BF, BJ, — without international search report and to be republished
`CF, CG, CI, CM, GA, GN, GQ, GW, ML, MR, NE, SN,
`upon receipt of that report
`TD, TG)A
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`WO 2009/088225
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`Description
`
`METHOD FOR TRANSMITTING AND RECEIVING CHANNEL
`
`STATE INFORMATION PERIODICALLY OR APERI-
`
`Technical Field
`
`ODICALLY
`
`The present invention relates to a method for enabling a terminal to periodically and/
`
`or aperiodically report channel state information to a base station, and a method for
`
`enabling the base station to receive the channel state information, wherein it is
`
`assumed that the channel state information for use in a multi—antenna system (i.e., a
`
`Multiple—Input Multiple—Output (MIMO) system) includes a channel quality indicator
`
`(CQI), a precoding matrix index (PMI), and a rank indicator (RI).
`
`Background Art
`
`Generally, a multi—antenna technology (hereinafter referred to as an MIMO
`
`technology) will hereinafter be described in detail.
`
`In brief, the MIMO technology is an abbreviation of the Multi—Input Multi—Output
`
`technology. The MIMO technology uses multiple transmission (Tx) antennas and
`
`multiple reception (Rx) antennas to improve the efficiency of transmission/reception
`
`(Tx/Rx) data, whereas a conventional art has generally used a single transmission (Tx)
`
`antenna and a single reception (Rx) antenna. In more detail, the MIMO technology is
`
`not dependent on a single antenna path to receive a single entire message, and
`
`completes the entire message by collecting a plurality of data fragments received via
`
`several antennas. As a result, the MIMO technology ca11 increase a data transfer rate
`
`within a specific range, or can increase a system range at a specific data transfer rate.
`
`FIG. 1 is a block diagram illustrating a conventional MIMO system.
`
`lf the number of antennas of a reception end and the number of antennas of a
`
`reception end are simultaneously increased as shown in FIG. 1, theoretical channel
`
`transmission capacity increases in proportion to the number of antennas in a different
`
`way from a conventional art in which only a transmitter or a receiver uses multiple
`
`antennas, such that a frequency efficiency can be greatly improved.
`
`The MIMO technology can be classified into a spatial diversity scheme and a spatial
`
`multiplexing scheme. The spatial diversity scheme increases transmission reliability
`
`using symbols passing various channel paths. The spatial multiplexing scheme simul-
`
`taneously transmits a plurality of data symbols via a plurality of Tx antennas, so that it
`
`increases a transfer rate of data. In addition, the combination of the spatial diversity
`
`scheme and the spatial multiplexing scheme has also been recently researched to
`
`properly acquire unique advantages of the two schemes.
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`[7]
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`Detailed descriptions of the spatial diversity scheme, the spatial multiplexing
`
`scheme, and the combination thereof will hereinafter be described in detail.
`
`Firstly, the spatial diversity scheme will hereinafter be described. The spatial
`
`diversity scheme is classified into a space—time block code scheme and a space—time
`
`Trellis code scheme which simultaneously uses a diversity gain and a coding gain.
`
`Generally, a bit error ratio (BER) improvement performance and a code— generation
`
`degree of freedom of the space—time Trellis code scheme are superior to those of the
`
`space—time block code scheme, whereas the calculation complexity of the space—time
`
`block code scheme is superior to that of the space—time Trellis code scheme. A spatial
`
`diversity gain corresponds to the product or multiplication of the number of Tx
`
`antennas and the number of Rx antennas. In the meantime, if a space—time coding
`
`scheme is applied to a frequency domain instead of a time domain, this space—time
`
`coding scheme may also be considered to be a frequency—space coding scheme, and a
`
`coding scheme applied to this frequency—space coding scheme is equal to that of the
`
`space—time coding scheme.
`
`Secondly, the spatial multiplexing scheme will hereinafter be described. The spatial
`
`multiplexing scheme is adapted to transmit different data streams via individual Tx
`
`antennas. In this case, a receiver may unavoidably generate mutual interference
`
`between data fragments which have been simultaneously transmitted from a
`
`transmitter. The receiver removes this mutual interference using a proper signal
`
`processing technique, so that it can receive the resultant data having no interference. In
`
`order to remove noise from the received data, a maximum likelihood receiver, a ZF
`
`receiver, a MMSE receiver, a D—BLAST, or a V—BLAST may be used. Specifically, if
`
`a transmission end is able to recognize channel information, a Singular Value Decom-
`
`position (SVD) scheme may be used to remove the noise.
`
`Thirdly, the combination of the spatial diversity scheme and the spatial multiplexing
`
`scheme will hereinafter be described. Provided that only a spatial diversity gain is
`
`acquired, a performance—improvement gain is gradually saturated in proportion to an
`
`increasing diversity order. Otherwise, provided that only the spatial multiplexing gain
`
`is acquired, a transmission reliability of a radio frequency (RF) channel is gradually
`
`deteriorated. As a result, a variety of schemes capable of acquiring both the afore-
`
`mentioned two gains simultaneously while solving the above—mentioned problems
`
`have been intensively researched by many companies or developers, for example, a
`
`double—STTD scheme and a space—time BICM (STBICM) scheme.
`
`in the meantime, a general communication system performs coding of transmission
`
`information of a transmission end using a forward error correction code, and transmits
`
`the coded information, so that channel errors can be corrected by a reception end. The
`
`reception end demodulates a received (Rx) signal, performs decoding of forward error
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`correction code, and recovers transmission information. By the decoding process,
`
`errors of the RX signal caused by the channel can be corrected.
`Each of all forward error correction codes has a maximum—correctable limitation in a
`
`channel error correction. In other words, if a reception (RX) signal has an error
`
`exceeding the limitation of a corresponding forward error correction code, a reception
`
`end is unable to decode the Rx signal into information having no error. Therefore,
`
`there is a need for the reception end to determine the presence or absence of an error in
`
`the decoded information. In this way, a specialized coding process for performing error
`
`detection is required, separately from the forward error correction coding process.
`
`Generally, a Cyclic Redundancy Check (CRC) code has been used as an error
`detection code.
`
`The CRC method is an exemplary coding method for performing the error detection
`
`instead of the error correction. Generally, transmission information is coded by the
`
`CRC method, and then the forward error correction code is applied to the CRC—coded
`
`infoimation. A single unit coded by the CRC and the forward error correction code is
`
`generally called a codeword. Respective codewords are mapped to streams corre-
`
`sponding to ranks, and the mapped result is transmitted, where the number of streams
`
`is equal to the number of ranks corresponding to independent channels of a MIMO
`
`communication system.
`
`Meanwhile, in the above—mentioned MIMO system, a transmission end perfoims
`
`precoding of TX data, and transmits the precoded TX data, and a reception end receives
`
`signals using a precoding vector used by the transmission end.
`
`The precoding vector for performing the above precoding is set to any one of
`
`precoding vectors which have been predefined as a codebook format in transmission/
`
`reception ends. In this case, a transmission scheme of the transmission end can be
`
`classified into an open—loop transmission method and a closed—loop transmission
`
`method according to specific information indicating whether or not the precoding
`
`vector of the transmission end requests feedback information from the reception end.
`
`In case of the open—loop transmission method, the transmission end selects a
`
`precoding vector without using feedback information of the reception end, and
`
`transmits signals. Otherwise, in case of the closed—loop transmission method, the
`
`reception end indicates a specific precoding vector among predefined codebooks
`
`according to a reception end, and feeds back channel information associated with the
`
`specific precoding vector, such that the transmission end transmits signals using such a
`
`feedback signal.
`
`In the meantime, in order to implement effective communication, there is a need for
`
`channel information to be notified along a feedback path, downlink channel in-
`
`formation is uploaded to an uplink, and uplink channel information is downloaded to a
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`downlink. The downlink or uplink channel information is represented by a channel in-
`
`formation indicator (CQI), i.e., a channel quality indicator (CQI). This CQI can be
`
`generated by various methods. For example, a method for quantizing chaimel state i11-
`
`formation without any change and uploading the quantized channel state information, a
`
`method for calculating an SINR and uploading the calculated SINR, and a method for
`
`notifying a channel s actual application state as in a modulation coding scheme (MCS)
`can be used.
`
`In this MIMO system, channel state information (CS1) to be notified to a base station
`
`by a terminal may include the above CQI, the precoding matrix index (PMI), and the
`
`rank indicator (RI) indicating the number of independent channels. This chaimel state
`
`information is periodically notified to a base station over a Physical Uplink Control
`
`Channel (PUCCH) and/or a Physical Uplink Shared Channel (PUSCH).
`
`Disclosure of Invention
`
`Technical Problem
`
`Accordingly, the present invention is directed to a method for transmitting and
`
`receiving channel state information periodically or aperiodically, that substantially
`
`obviates one or more problems due to limitations and disadvantages of the related art.
`
`There are needed a method for allowing a terminal to periodically transmit channel
`
`state information to a base station, and a method for allowing the terminal to aperi-
`
`odically transmit the channel state information to the base station upon receiving a
`
`request from the base station.
`
`Technical Solution
`
`In order to solve the above—1nentioned problems, an object of the present invention is
`
`to provide a method for allowing the terminal to effectively transmit channel state in-
`
`formation aperiodically.
`
`Also, if the chaimel state information is periodically transmitted, a11 error detection
`
`capability is insufficient for current PUCCH transmission, such that a space for
`
`inserting an error detection code used to supplement the insufficient error detection ca-
`
`pability may encounter unexpected problems.
`
`ln order to solve the above—mentioned problems, another object of the present
`
`invention is to provide a method for effectively solving PUCCH channel capacity
`
`problems while the terminal periodically transmits channel state information.
`
`Additional advantages, objects, and features of the invention will be set forth in part
`
`in the description which follows and in part will become apparent to those having
`
`ordinary skill in the art upon examination of the following or may be learned from
`
`practice of the invention. The objectives and other advantages of the invention may be
`
`realized a11d attained by the structure particularly pointed out in the written description
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`5
`
`and claims hereof as well as the appended drawings.
`
`To achieve these objects and other advantages and in accordance with the purpose of
`
`the invention, as embodied and broadly described herein, a method for aperiodically
`
`transmitting channel state information (CS1) by a terminal, the method includes:
`
`receiving an indicator requesting a channel state information report of a downlink
`
`channel from a base station over a downlink control channel; and aperiodically
`
`transmitting the channel state infoiination (CS1) to the base station over a physical
`
`uplink shared channel (PUSCH) upon receiving the indicator from the base station.
`
`The channel state information (CS1) may include at least one of a precoding matrix
`
`index (PM1), a channel quality indicator (CQ1), and a rank indicator (R1).
`
`The physical uplink shared channel (PUSC1-1) may attach a CRC to a transmission
`
`control signal in order to detect a CRC error from the transmission control signal, such
`
`that the resultant transmission control signal including the CRC may be transferred. lt
`
`is assumed that the transmission control signal includes a CQ1 and a PMI transferred
`
`over a physical uplink shared channel (PUSCH). A rank indicator (R1) transferred over
`
`the physical uplink shared channel (PUSCH) may have no CRC, such that the resultant
`
`rank indicator (R1) having no CRC may be transferred.
`
`The method further may include periodically transmitting the channel state in-
`
`formation (CS1) to the base station over a physical uplink control channel (PUCCH).
`
`The physical uplink control channel (PUCCH) may have an error detection capability
`
`Weaker than that of the physical uplink shared channel (PUSCH).
`
`The method may further includes, upon receiving the indicator requesting the
`
`channel state information report at a specific subframe, transmitting the channel state
`
`information (CS1) over the physical suplink shared channel (PUSCH) after a lapse of 4
`
`subframes from the specific subframe.
`
`The channel state information may include a Wideband precoding matrix index and a
`
`subband precoding matrix index, in which if the subband precoding matrix index is
`
`transferred, a precoding matrix index for each subband is cyclically transmitted in an
`
`entire system band or is transferred from an upper layer higher than a physical layer
`
`according to a predetermined order.
`
`In another aspect of the present invention, there is provided a method for periodically
`
`transmitting channel state information (CS1) by a terminal, the method including:
`
`transmitting channel quality information including both a channel quality indicator
`
`(CQ1) and a precoding matrix index (PM1) to a base station; and transmitting a rank
`
`indicator (R1) to the base station, in which the channel quality information and the rank
`
`indicator (R1) are transferred over a physical uplink control channel (PUCCH) at
`different times.
`
`[33]
`
`The channel quality information may include Wideband channel quality information
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`and subband channel quality information, in which the wideband channel quality in-
`
`formation and the subband channel quality information are transferred over the
`
`physical uplink control channel (PUCCH) at different times.
`
`The rank indicator (RI) may have a transmission period, which is different from a
`
`transmission period of the channel quality information.
`
`The transmission period of the rank indicator (RI) may be longer than the
`
`transmission period of the channel quality information.
`
`The subband channel quality information may be transferred at a specific time
`
`between transmission times of two successive wideband channel quality information
`
`parts.
`
`In another aspect of the present invention, there is provided a method for allowing a
`
`base station to aperiodically receive channel state information (CS1) from a terminal,
`
`the method including: transmitting an indicator requesting a channel state information
`
`report of a downlink channel over a downlink control channel; and aperiodically
`
`receiving a report of the channel state information (CS1) from the terminal over a
`
`physical uplink shared channel (PUSCH).
`
`The channel state information may include at least one of a precoding matrix index
`
`(PMI), a channel quality indicator (CQI), and a rank indicator (RI), and the physical
`
`uplink shared channel (PUSCH) attaches a CRC to a transmission signal in order to
`
`detect a CRC error from the transmission signal, such that the resultant transmission
`
`control signal including the CRC is transferred.
`
`The method further includes periodically receiving the channel state information
`
`(CS1) from the terminal over a physical uplink control channel (PUCCH).
`
`Advantageous Effects
`
`The present invention may provide a method for allowing a terminal to aperiodically
`
`transmit channel state information to a base station upon receiving a request from the
`
`base station. In more detail, the base station prescribes an indicator for transmitting
`
`aperiodic channel state information to the terminal in a downlink control channel, such
`
`that aperiodic channel state information can be effectively transmitted. Transmission
`
`over a PUSCH is prescribed, such that the error detection capability of the base station
`
`can be guaranteed.
`
`Also, the present invention transmits various channel state information transmitted
`
`over a PUCCH, for example, a wideband PMT/CQI, a subband PMI/CQI, and an RI at
`
`different times, resulting in a guarantee of PUCCH capacity.
`
`lt is to be understood that both the foregoing general description and the following
`
`detailed description of the present invention are exemplary and explanatory and are
`
`intended to provide further explanation of the invention as claimed.
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`Brief Description of the Drawings
`
`The accompanying drawings, which are included to provide a further understanding
`
`of the invention and are incorporated in and constitute a part of this application,
`
`il-
`
`lustrate e1nbodiment(s) of the invention and together with the description seive to
`
`explain the principle of the invention. In the drawings:
`
`FIG. 1 is a block diagram illustrating a conventional MIMO system;
`
`FIGS. 2 a11d 3 illustrate methods for allowing a terminal to periodically transmitt
`
`channel state information to a base station;
`
`FIG. 4 is a conceptual diagram illustrating a method for allowing a terminal to aperi-
`
`odically transmit channel state information over a PUSCH according to the present
`
`invention; and
`
`FIG. 5 is a conceptual diagram illustrating a method for periodically transmitting a
`
`wideband CQl/PMI, a subband CQl/PMI, and an R1 over a PUCCH according to the
`
`present invention.
`
`Mode for the Invention
`
`Reference will now be made in detail to the preferred embodiments of the present
`
`invention, examples of which are illustrated in the accompanying drawings. Wherever
`
`possible, the same reference numbers will be used throughout the drawings to refer to
`
`the same or like parts. The following embodiments of the present invention may be
`
`modified into various formats, and the scope of the present invention is not limited to
`
`only the following embodiments and can also be applied to other examples.
`
`For the convenience of description and better understanding of the present invention,
`
`the following detailed description will disclose a variety of embodiments and modi-
`
`fications of the present invention. However, those skilled in the art will readily un-
`
`derstand and implement the embodiments and modifications of the present invention.
`
`In some cases, in order to prevent ambiguous concepts of the present invention from
`
`occurring, conventional devices or apparatus well known to those skilled in the art will
`
`be omitted and be denoted in the form of a block diagram on the basis of the important
`
`functions of the present invention. Wherever possible, the same reference numbers will
`
`be used throughout the drawings to refer to the same or like parts.
`
`In the following description, a terminal may include a user equipment (UE), a mobile
`
`terminal (Mobile Terminal), and a mobile station (MS), and may also be called any one
`
`of them as necessary. Also, the base station may include a Node—B and an eNode—B,
`
`and may also be called either of them.
`
`One embodiment of the present invention provides a method for allowing a terminal
`
`to effectively transmit channel state information aperiodically. Presently, channel state
`
`infonnation including a CQI, a PMI and an RI may be periodically transferred from the
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`[52]
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`[53]
`
`terminal to the base station over the PUCCH.
`
`FIGS. 2 and 3 illustrate methods for allowing a terminal to periodically transmitt
`channel state information to a base station.
`
`Referring to FIGS. 2 and 3, a user equipment (UE) transmits a CQI, a PMI and an RI
`
`over a PUCCH and/or a PUSCH at lI1tC1‘V'<1lS of a predetermined period, such that the
`
`UE need not receive a special grant signal for transmitting channel state information
`
`from the base station. The user equipment (UE) feeds back channel state infoimation
`
`(CQI, PMI, and RI) over a PUCCH or PUSCH at intervals of a specific period (e.g., A
`
`frame under PUCCH transmission or a B frame under PUSCH transmission) con-
`
`structed by an upper layer (e.g., an RRC layer).
`
`Generally, due to the limitation of given capacity, the PUCCH signal is transmitted
`under the condition that there is no additional error detection code such as a CRC.
`
`Also, channel state information is transferred over a PUSCH due to the limitation of
`
`PUCCH capacity. In case of the PUSCH, this channel state information includes an
`
`error detection code such as a CRC, such that the resultant channel state information is
`
`transmitted over the PUSCH.
`
`However, in some cases, there is needed a specific procedure for a base station to
`
`report channel state information to a user equipment (UE) at a specific time, separately
`
`from another procedure for allowing the base station to periodically report the channel
`
`state information. If a channel state information transmission event (i.e., eNB triggered
`
`CSI reporting event) induced by the base station occurs, there is a need for the base
`
`station to infonn the user equipment (UE) of the eNB triggered CSI reporting event
`
`over a downlink control channel by an indicator. Therefore, scheduling information for
`
`an uplink channel can be carried out, and it is more preferable for an uplink grant (UL
`
`Grant) signal for a PUSCH to be carried out as described above. There is no need for
`
`the above—mentioned indicator to have a long length, such that an uplink channel in-
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`formation transmission request such as a CQI report request may be transferred to the
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`user equipment (UE) by a signaling process of one bit. In case of applying an aperiodic
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`channel state report scheme to a PUSCH—based channel state report scheme except for
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`a PUCCH—based periodic channel state information report scheme in a method for
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`reporting channel state information such as a CQI, a PMI, or an RI, in order to add an
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`indication function of at least one channel state information requested from among
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`several channel state information including the above three channel state information, a
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`signaling process of N bits (where N 2) instead of one bit may be contained in an
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`uplink acknowledgement (ACK) signal for the PUSCH.
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`In the meantime, an error detection capability of the PUCCH may be less than that of
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`the PUSCH as described above. Therefore, channel state information aperiodically
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`reported by the user equipment (UE) may be transferred over the PUSCH capable of
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`TELEFONAKTIEBOLAGET LM ERICSSON AND
`ERICSSON INC. EX. NO. 1010
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`WO 2009/088225
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`PCT/KRZUU9/000084
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`detecting CRC errors. As a result, the base station is able to detect RX errors of the
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`CQI, PMI, and RI, and is able to aperiodically acquire channel state information.
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`Channel state information transferred by the user equipment (UE) may be either
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`wideband channel state information of all system bands or subband channel state in-
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`formation of an arbitrary frequency band contained in an overall system band. In case
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`of transferring the subband channel state information (e. g., subband PMI), each
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`subband PMI may be cyclically transferred in an overall system band, or may also be
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`transferred over an upper layer according to a predetermined order.
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`FIG. 4 is a conceptual diagram illustrating a method for allowing the user equipment
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`(UE) to aperiodically transmit channel state information over a PUSCH according to
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`the present invention.
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`Referring to FIG. 4, the user equipment (UE) is able to receive an indicator (indicator
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`of 1 bit or N bits) requesting aperiodic transmission of channel state information from
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`a base station over a downlink control channel at step S401. The indicator received at
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`the step S401 may be used as an UL Grant signal. For the convenience of description,
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`this indicator may hereinafter be referred to as a CQI Request having a length of 1 bit.
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`However, the CQI Request may have more bits to indicate whether subband channel
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`state information is requested, as well as to inform the UE of additional information
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`such as a subband position.
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`In the meantime, the user equipment (UE) having received the CQI Request signal as
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`described above answers the CQI Request signal after the lapse of a predetermined
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`time, such that it is able to transfer aperiodic channel state infonnation such as CQI/
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`PMI/RI over a PUSCH at step S402. Preferably, if the UE receives the CQI Request at
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`the N—th subframe, it is able to transmit CQI/PMI/RI over the PUSCH to answer the
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`CQI Request at the (n+4)—th subframe,
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`PUSCH may further include a CRC for detecting errors of a TX signal, such that the
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`resultant PUSCH may be transferred. So, the base station having received aperiodic
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`channel state information determines the presence or absence of errors in channel state
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`information received from the user equipment (UE), such that the determined result
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`may be notified as confirmation information to the user equipment (UE). In this case,
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`in association with all categories of channel state information transferred over the
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`PUSCH, the CRC may be attached to channel state information of some categories
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`according to a control information multiplexing scheme, an amount of information,
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`and a requested reliability, such that the CRC—attached channel state information may
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`be transferred. Specifically, confirmation information, indicating that the latest PMI
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`reported from the UE to the base station has been used by the base station, may be
`referred to as PMI confirmation information.
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`In the meantime, in case of using PMI confirmation information in a downlink
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`TELEFONAKTIEBOLAGET LM ERICSSON AND
`ERICSSON INC. EX. NO. 1010
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`WO 2009/088225
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`PCT/KRZUU9/000084
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`10
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`control channel, it is very important for the base station to detect errors in a subband
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`PMI, a wideband PMI decided as either a designated frequency area or a total system
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`band, and a rank information feedback.
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`Therefore, if the number of bits of control information (CQI, PMI, and/or RI) fed
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`back over an arbitrary PUCCH is less than a maximum number of transmittable in-
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`formation bits which satisfy a QoS requested by the PUCCH in an arbitrary feedback
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`event (i.e.._ if there is a redundant space in transmission bits capable of satisfying a QoS
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`designated on the PUCCH without using an additional addition process), it is
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`preferable for a specific code for strengthening an error detection capability to be
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`inserted into the PUCCH. For example, this specific code may be a parity check code
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`(e.g., even/odd parity, Hamming code). By this parity check code, an error detection
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`capability based on a syndrome check of an algebraic code based coding of the
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`PUCCH can be assigned. But, the error detection capability based on the afore-
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`mentioned algebraic code based coding may be damaged by length adaptation for a
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`code sequence. Therefore, additional error detection codes may be inserted into the
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`PUCCH, such that it is preferable that the error detection capability is strengthened.
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`If the number of bits of control information (CQI, PMI, and/or RI) fed back over an
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`arbitrary PUCCH in an arbitrary feedback event is higher than a maximum number of
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`transmittable information bits which satisfy a QoS requested by the PUCCH (i.e., if
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`any redundant bit capable of satisfying a QoS requested on the PUCCH does not exist),
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`the insertion of additional error detection codes or the strengthening of arbitrary error
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`detection capability may have unexpected difficulty.
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`Therefore, in order to always provide the error detection capability of a PUCCH
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`control information feedback, it is preferable that the control information be fed back
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`with a prescribed margin to prepare for the maximum number of control information
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`bits which satisfy a QoS in all PUCCH transmissions simultaneously While being fed
`back.
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`Therefore, if channel state information is periodically transferred over the PUCCH,
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`one embodiment of the present invention provides a method for transferring CQI/PMI
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`information and RI information at different times. Also, if the wideband CQI/PMI and
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`the subband CQI/PMI are simultaneously transmitted, it is pref