WO2011081410A2 - Method and apparatus for reporting channel status information in a wireless communication system - Google Patents

Abstract

A base station in a downlink of a wireless communication system requires downlink channel status information of terminals to transmit link-adaptive transmission to the terminals. This channel status information is generated as a terminal receives a reference signal to be transmitted via the downlink, and fed back to the base station through a control channel of the uplink. Therefore, an increase in the transmission cycle of the reference signal and the feedback cycle of the channel status information may increase a difference between the channel status having been fed back from a terminal to the base station and the channel status at the point when data is actually transmitted to the terminal, thereby causing inefficient link-adaptive transmission and deteriorating the system performance. The present invention thus provides a method and apparatus for designing an uplink periodic feedback structure for reducing the channel status difference in case a reference signal for the estimation of a downlink channel status is transmitted over a prolonged cycle, and distributing a feedback overhead of terminals in terms of the system.

Description

Method and device for reporting channel status information in wireless communication system

The present invention relates to an apparatus and method for reporting a channel state in a cellular wireless communication system. In particular, the present invention relates to a channel state according to a feedback information characteristic of a time change when a reference signal for downlink channel estimation is transmitted over a long period. A method and system for determining and reporting feedback order of information.

The mobile communication system is evolving into a high speed, high quality wireless packet data communication system for providing data service and multimedia service, instead of providing a voice-oriented service in the early days. Recently, various mobile communication standards such as 3GPP's High Speed Downlink Packet Access (HSDPA), HSUPA (High Speed Uplink Packet Access), 3GPP2's High Rate Packet Data (HRPD), and IEEE's 802.16 are high-speed, high-quality wireless packet data transmission services. Was developed to support it.

Existing third generation wireless packet data communication systems such as HSDPA, HSUPA, HRPD, etc. use techniques such as Adaptive Modulation and Coding (AMC) and channel sensitive scheduling to improve transmission efficiency. By utilizing the AMC method, the transmitter can adjust the amount of data to be transmitted according to the channel state. In other words, if the channel condition is bad, the amount of data to be transmitted can be reduced to a desired level, and if the channel condition is good, the amount of data to be transmitted can be increased so that a large amount of information can be effectively transmitted while the reception error probability is set to a desired level. When the channel sensitive scheduling resource management method is used, the system capacity is increased compared to allocating and serving a channel to one user because the transmitter selectively services a user having a good channel condition among several users. This increase in capacity is called the multi-user diversity gain. In short, the ACM method and the channel sensitive scheduling method are a method of applying an appropriate modulation and coding scheme at a time when it is determined to be most efficient by receiving partial channel state information from a receiver.

Recently, studies are being actively conducted to convert CDMA (Code Division Multiple Access), which is used in second and third generation mobile communication systems, to orthogonal frequency division multiple access (OFDMA) in a next generation system. 3GPP and 3GPP2 have begun standardizing on evolutionary systems using OFDMA. It is known that the capacity can be increased in the OFDMA method as compared to the CDMA method. One of various causes of capacity increase in the OFDMA scheme is that frequency domain scheduling can be performed on the frequency axis. Just as the channel gains capacity gains through channel-sensitive scheduling as the channel changes over time, more capacity gains can be achieved if the channel utilizes different characteristics depending on frequency.

1 is a diagram illustrating a downlink subframe structure in a conventional LTE system.

Referring to FIG. 1, one subframe 115 is composed of 14 OFDM symbols 100 to 113, and a region allocated for a physical downlink control channel (hereinafter, referred to as PDCCH) is defined as 3 in the front. Number of OFMA symbols 100 to 102, and a region allocated for a physical downlink data channel (PDSCH) is the remaining OFDM symbols 103 to 113. The PDCCH is transmitted over the entire system band in the PDCCH region 100 to 102, but the PDSCH is transmitted based on a resource block (RB) 114, which is a basic scheduling unit. Here, each RB consists of 12 subcarriers, and the total number of RBs varies according to system bandwidth. The reason why the area for the PDCCH is located at the beginning of the subframe is that the UE first checks the PDCCH and then takes a micro sleep mode when there is no data corresponding to the UE to reduce power consumption of the UE in the data channel area. For sake.

2 is a diagram illustrating a transmission structure of a downlink common reference signal (CRS) for four transmission antennas in a conventional LTE system.

Referring to FIG. 2, one resource element (RE) refers to one subcarrier 203 in one OFDM symbol 201 and one RB 202 in one subframe 200. ) Consists of 12X14 REs. The receiver receives the CRSs 210 to 213 corresponding to the antennas 204 to 207 to estimate the channel state for each transmission antenna. To this end, as shown in FIG. 2, each antenna 204-207 transmits a null signal 208 to the RE region of the CRS transmitted from another antenna. That is, in antenna port 0 (204), the null signal 208 at the RE position of the CRSs 211 to 213 transmitted from the other antenna ports 1-3 (205 to 207). Send it. In one RB 202, CRSs 210 and 211 for antenna port 0 204 and antenna port 1 205 are transmitted to eight REs, respectively, antenna port 2 206 and antenna port 3 207. CRSs 212 and 213 for each are transmitted to four REs. Therefore, in case of four transmission antennas, CRSs are transmitted using a total of 24 REs per one RB 202. The receiver receives the CRS, estimates the channel, and then uses the PDSCH 209 to demodulate or generate downlink channel state information. Here, if the use of the CRS is limited to generating downlink channel state information rather than channel estimation for demodulation, the number of REs of the CRS transmitted to one RB 202 will decrease. This is because the channel estimation error required for demodulation is smaller than the required error for generating downlink channel state information.

The receiver receives a CRS as shown in FIG. 2 for all RBs in every subframe, estimates a channel, and then rank rank (RI) and channel quality indicator representing a downlink channel state. Indicator, CQI) and Precoding Matrix Indicator (PMI) are generated.

3 is a diagram illustrating a structure of uplink periodic feedback in a conventional LTE system.

Referring to FIG. 3, the terminal transmits RI, CQI, and PMI information indicating the channel state to the base station as shown in FIG. 3. In FIG. 3, parameters P (= Np), K, M, and O, which determine a feedback structure, are transmitted to the UE through higher signaling, and definitions and ranges of the respective parameters are as follows.

K: number of representative subbands for CQI reporting, K {1, 2, 3, 4},

O: offset between RI reporting point and wideband CQI / PMI reporting point, O {0, -1,... ,-(P-1), -P},

M = M _RI : RI reporting period, M {1, 2, 4, 8, 16, 32, OFF},

Np, N _{OFFSET, CQI} : period and offset for subband CQI feedback, determined by cqi-pmi-ConfigurationIndex,

-M _RI , N _{OFFSET, RI} : RI reporting period and offset, determined by ri-ConfigurationIndex.

Here, the subband means a group consisting of one or a plurality of consecutive RBs. The time sensitive subband CQI feedback period 302 is relatively shorter than the RI 303 and wideband CQI / PMI feedback 305 periods. And since subband CQI feedback must be performed for all K representative subbands in the J frequency band portion, when wideband CQI / PMI feedback occurs once, CQI feedback for all J * K subbands is performed. 304, thus the wideband CQI / PMI feedback period is (J * K + 1) * P (300,301). Since RI is very insensitive to time, it is fed back at the longest period, and is offset O 306 to prevent transmission collisions with other feedback information.

4 is a diagram illustrating a transmission structure and a downlink feedback structure of a downlink reference signal in an LTE-Advanced (hereinafter, LTE-A) system.

Referring to FIG. 4, channel state information reference signals (CSI-RSs) 402 and 403 for downlink channel state estimation are transmitted in a frame period 404. That is, the CSI-RS is transmitted only in one specific subframe within the frame (400, 401) section consisting of 10 subframes. The reason why the CSI-RS is transmitted is because it is used only for downlink channel state estimation as mentioned above. After receiving the CSI- RSs 402 and 403, the terminals 407 to 409 respectively transmit the corresponding channel state information to the uplink after the minimum calculation time 410 and 411 required for generating the downlink channel state information has elapsed. Feedback (412-414). In this case, due to the long CSI-RS transmission period 404, the receiver feeds back a plurality of subband channel state information and broadband channel state information in the transmission period, and the base station determines when the terminal feeds back what information the terminal receives from the base station. Determine the error of the downlink channel state used. Therefore, it is necessary to design an uplink feedback structure in consideration of the characteristics of the feedback channel state information. In addition, when a plurality of terminals perform feedback immediately after channel estimation from the CSI-RS in order to reduce the error of the channel state, uplink overhead may be concentrated in one subframe. Accordingly, there is a need for a feedback structure design for distributing uplink feedback overhead while maintaining uniformity among the terminals, with respect to channel state information fed back by multiple terminals.

According to an embodiment of the present invention, when a reference signal for downlink channel estimation is transmitted in a long period in a wireless communication system, the feedback order of channel state information is determined in consideration of the characteristics of feedback information about time change, and the cyclic transmission of the feedback information is performed. Suggest a method. That is, according to the embodiment of the present invention, when the period of the reference signal transmitted for the downlink channel state estimation in a wireless communication system is long, the base station feedback channel from the terminal and the channel at the time of actually transmitting data to the terminal Provided are a method and apparatus for designing an uplink periodic feedback structure that reduces an error with a state and distributes overhead generated by feedback of a plurality of terminals from a system perspective.

According to an embodiment of the present invention, a method of transmitting feedback information includes generating first feedback information, transmitting the first feedback information at a first time point of a first period, and a second feedback. Generating information and transmitting the second feedback information at a second time point of a second period, wherein the first time point and the second time point correspond to the first period and the second time period. Characterized in that it is a different time point from the starting point.

The feedback information is calculated based on the channel state information reference signal (CSI-RS) transmitted at a predetermined time period. In addition, when the first feedback information is subband channel state information (SB-CSI) and the second feedback information is wideband channel state information (WB-CSI), a first time point at a start time point of the first period and the second period Is located closer than the second time point. In addition, the terminal transmits the feedback information, and the terminal receives the feedback transmission pattern information from a base station, generates feedback information, and a subframe to perform feedback transmission based on the feedback transmission pattern. And determining, and transmitting the feedback information to the base station. The feedback transmission period is set based on the CSI-RS transmission period.

In addition, according to an embodiment of the present invention, a method for receiving feedback information in a communication system may include receiving first feedback information at a first time point of a first period and receiving second feedback information at a second time point of a second period. The first time point and the second time point are different points from the start point of the first period and the second period.

The apparatus for transmitting feedback information in a communication system according to an embodiment of the present invention may generate first feedback information and be transmitted at a first time point of a first period, and generate second feedback information to generate a second time point of a second period. And a controller for transmitting the first and second feedback information by the controller, wherein the first time point and the second time point are mutually different from the starting point of the first period and the second period. It is characterized by another point in time.

Also, in an embodiment of the present invention, an apparatus for receiving feedback information in a communication system includes: a receiver for receiving first feedback information at a first time point in a first period and receiving second feedback information at a second time point in a second period. And a controller for analyzing a state of a downlink channel from the first and second feedback information, wherein the first time point and the second time point are different time points from the start points of the first period and the second period. It is done.

As described above, the present invention determines a feedback order of channel state information in consideration of characteristics of feedback information for time variation when a reference signal for downlink channel estimation is transmitted in a long period, and proposes a cyclic transmission method of the feedback information. . Through this, the error of the channel state used in the base station can be reduced, and the channel state error performance for a plurality of feedback information can be obtained evenly. In addition, the cell-characterized feedback pattern length and the method for setting a feedback transmission pattern for each terminal proposed in the present invention can efficiently operate the system by distributing feedback overhead generated from multiple terminals from a system perspective, and channel for each terminal. It allows to maintain fairness in terms of performance of state error.

1 illustrates an OFDM based downlink subframe structure;

2 is a diagram illustrating a structure in which a common reference signal is transmitted in a subframe in case of four transmission antennas in an LTE system downlink;

3 illustrates a periodic feedback structure transmitted through an uplink control channel in an LTE system;

4 illustrates a downlink reference signal transmission structure and an uplink feedback structure in an LTE-Advanced system;

5 is a diagram illustrating an uplink feedback structure and method for one terminal according to a first embodiment of the present invention;

6 illustrates an uplink feedback structure and method for multiple terminals according to a second embodiment of the present invention;

7 illustrates a feedback window based uplink feedback structure and method for multiple terminals according to a third embodiment of the present invention.

8 is a diagram illustrating a transmission procedure of a base station according to an embodiment of the present invention;

9 is a diagram illustrating a transmission and reception procedure of a terminal according to an embodiment of the present invention;

10 is a diagram showing the structure of a transmission apparatus of a base station according to the present invention;

11 is a diagram showing the structure of a transmitting and receiving device of a terminal according to the present invention;

Hereinafter, embodiments of the present invention will be described in detail with the accompanying drawings. In addition, in describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Further, in describing the embodiments of the present invention in detail, an OFDM-based wireless communication system, in particular the 3GPP EUTRA standard will be the main target, but the main subject of the present invention is another communication system having a similar technical background and channel form. In addition, it is possible to apply with a slight modification in the range without departing greatly from the scope of the present invention, which will be possible in the judgment of those skilled in the art.

In downlink of a wireless communication system, a base station uses downlink channel state information of terminals for link adaptive transmission to terminals. The channel state information is generated by the terminal receiving a reference signal transmitted in downlink, which is fed back to the base station through the uplink control channel. Therefore, an increase in the transmission period of the reference signal and the feedback period of the channel state information increases the error between the channel state fed back from the terminal and the channel state at the time when data is actually transmitted to the terminal, resulting in inefficient transmission and system performance. Deteriorates. The present invention proposes a method and apparatus for designing an uplink periodic feedback structure that reduces a channel state error when a reference signal for downlink channel state estimation is transmitted in a long period and distributes feedback overhead of terminals from a system point of view.

In the following description of the present invention, the term "period" and "window" will be used interchangeably as terms related to the period for transmitting feedback. In addition, as shown by the drawings of the present invention, the feedback pattern is determined by an offset between a period or a window and a time point at which feedback is transmitted from a start point of the period or window.

The first embodiment of the present invention proposes a feedback structure in consideration of the temporal change characteristic of the channel state information in order to reduce the error of the channel state. The subband channel state information SB-CSI is channel state information representing a subband and is more sensitive to a change in time than the wideband channel state information WB-CSI. Therefore, when delaying the SB-CSI feedback, the error of the channel state generated will be larger than when delaying the WB-CSI feedback. By using such characteristics of channel state information, a method of performing SB-CSI feedback sensitive to time change before WB-CSI feedback is proposed. Also, in order to prevent non-uniformity of subband channel estimation error generated when SB-CSI for a plurality of subbands is transmitted through a plurality of subframes, a cyclic transmission method of a plurality of subbands is provided every feedback period. do.

A second embodiment of the present invention proposes a cell-specific feedback transmission pattern length and a method for setting a feedback transmission pattern for each terminal for distributing feedback overhead transmitted from multiple terminals from a system perspective. And in order to maintain the equilibrium of feedback transmission between words, the feedback transmission pattern of each terminal is configured to uniformly use the available feedback resources within the pattern length.

The third embodiment of the present invention proposes a feedback window for setting the length of a cell-specific feedback transmission pattern and a feedback transmission pattern for each terminal for distributing feedback overhead transmitted from multiple terminals from a system perspective. . This feedback window prevents duplication of feedback transmitted during the subframe period from the time of CSI-RS measurement to the completion of feedback information generation, and enables efficient management of feedback resources of multiple terminals from a system perspective.

Hereinafter, the method and apparatus for designing a periodic uplink feedback structure of downlink channel state information proposed by the present invention will be described in detail.

First embodiment

5 is a diagram illustrating a periodic uplink feedback structure and method for one terminal according to the first embodiment of the present invention.

Referring to FIG. 5, it is assumed that the CSI- RSs 504 and 505 for channel state estimation are transmitted in the second subframe of each frame 500 and 501 through the downlink 502. In this case, if the CSI-RS transmission period is long, the terminal performs channel estimation, and then periodically generates a plurality of channel state information (eg, a plurality of subband CQI and wideband CQI / PMI information) through a plurality of subframes. This is transmitted to the base station through the uplink feedback channel. At this time, as the uplink feedback time is farther from the downlink channel estimation time, an error between the channel state used in the base station and the channel state at the actual data transmission time increases. Therefore, in order to reduce the error of the channel state, it is desirable to consider the temporal change characteristic of the channel state information. In the first embodiment of the present invention, the feedback structure of the terminal as shown in FIG. 5 is designed.

Subband Channel State Information (SB-CSI) 507 and 508 are channel state information representing subbands, and are referred to as Wideband Channel State Information (WB-CSI) 510. More relatively sensitive to changes in time. Therefore, when delaying the SB-CSI feedback, the error of the channel state generated will be larger than when delaying the WB-CSI feedback. By using such characteristics of channel state information, a method of performing SB-CSI feedback sensitive to time change before WB-CSI feedback is proposed. In addition, in order to prevent non-uniformity of the subband channel estimation error generated when the SB-CSI for the plurality of subbands is transmitted through the plurality of subframes, cycling of the plurality of subbands in each feedback period (511). We propose the transmission method. That is, as shown in FIG. 5, when feeding back SB-CSI 1 and SB-CSI 2 for each of two subbands, the UE transmits SB-CSI 1 507 and SB-CSI at regular intervals in frame # 0 500. 2 (508), WB-CSI (510) in the order of feedback, frame # 1 (501) in the order of SB-CSI 2 (511), SB-CSI 1 (511), WB-CSI (510) in the order of feedback do. Here, the SB-CSI 1 507, the SB-CSI 2 508, and the WB-CSI 510 are transmitted in a period shorter than the CSI-RS transmission period.

Second embodiment

6 is a diagram illustrating an uplink feedback structure and method for multiple terminals according to a second embodiment of the present invention.

Referring to FIG. 6, in order to distribute feedback overhead transmitted from multiple terminals from a system perspective, the second embodiment of the present invention provides a terminal 606 and a length of a cell-specific feedback transmission pattern. A method of setting the respective feedback transmission patterns 602 to 604 is proposed. As the number of terminals increases, the length 606 of the feedback transmission pattern increases to maintain a uniform dispersion of feedback overhead and an average uniformity of channel estimation error. In addition, the feedback transmission pattern of the terminals sets the terminals to uniformly use possible feedback resources within the pattern length. This is to maintain the fairness of the feedback transmission between the terminals.

FIG. 6 shows feedback patterns of the UEs 602 ˜ 604 when the cell-specific feedback pattern length is three frames and CSI-RS 600 transmission occurs in every second subframe. When the CSI-RS 600 is received, each terminal performs a feedback transmission during the feedback pattern length 606 by a predetermined pattern after the minimum calculation time 605 required for channel estimation has elapsed. As shown by the reference numeral 602, the terminal # 1, as shown by the reference numeral 602, the terminal # 3 performs the feedback transmission in a different pattern in the cell-specific feedback pattern length as shown by the reference numeral 604. Here, the number of each pattern means a subframe number that assumes a subframe after the minimum calculation interval 605 as a starting point. In this case, the terminal # 1 transmitting the pattern 024 (change pattern of the subframe transmitting the feedback information) has a subframe # 5 from the frame # 0 (607) (pattern 0: 0th subframe after the minimum calculation interval) (610). ), Subframe # 7 in frame # 1 608 (pattern 2: second subframe after minimum calculation interval) 611, subframe # 9 in frame # 2 609 (pattern 4: 4 after minimum calculation interval) The first subframe) (612). Each terminal-specific pattern may be generated by cyclic shifting a predetermined pattern in any one terminal. That is, in the UE UE # 1 of FIG. 6, the subframe number for reporting the channel state information is cyclically repeated in subframes # 5, # 7, # 9, # 5, --- as shown by reference numeral 602. Therefore, in case of the UE # 1, the subframe change pattern is the subframe # 5 of the 0th change pattern in frame # 0 and the subframe of the second change pattern in frame # 1 after performing the minimum calculation section 605. # 7), in frame # 2, feedback is performed in the subframe # 9 of the fourth change pattern. Therefore, if the pattern 024 of the terminal # 1 is cyclically moved, feedback patterns of other terminals may be determined. That is, when the last 4 of the terminal # 1 moves to the front, the pattern of the terminal # 2 becomes 402. Similarly, when the pattern of the terminal # 2 is cyclically moved, the pattern 240 of the terminal # 3 is determined. This method allows all terminals to use the feedback resources equally. In addition to this method, a pattern of a corresponding terminal may be determined using a random variable generator based on a unique ID of each terminal, and the pattern of each terminal may be updated with a feedback pattern length period or a longer period.

Third embodiment

FIG. 7 is a diagram illustrating a feedback window-based uplink feedback structure and method for multiple terminals according to the third embodiment of the present invention.

Referring to FIG. 7, a third embodiment of the present invention uses a feedback window to distribute feedback overhead transmitted from multiple terminals from a system perspective. That is, the length 1106 of the cell-specific feedback transmission pattern and the feedback transmission patterns 1102 to 1104 for each terminal are set using the feedback window 1120. The feedback window 1120 prevents duplication of feedback transmitted during the subframe period from the CSI-RS measurement time to the completion of feedback information generation, and the system can efficiently manage feedback resources of a plurality of terminals.

The feedback transmission patterns 1102-1104 of the terminals set the terminals to use the feedback resources possible within the feedback pattern length 1106 uniformly. This is to maintain the fairness of the feedback transmission between the terminals. In this case, the feedback transmission patterns 1102 to 1104 are set in the feedback window 1120. The size of the feedback window 1120 may not be larger than the CSI-RS 1100 transmission period, and the size may be equally set for each frame 1107-1109 within the length 1106 of the transmission pattern, or It may be set differently. In addition, the start frame of the feedback window 1120 may also be set identically for each frame 1107-1109 within the length 1106 of the transmission pattern, or may be set differently.

FIG. 7 illustrates an example in which a CSI-RS transmission period is set to one frame, and the CSI-RS transmission period may be shorter or longer than this. Accordingly, one frame 10, which is a basic unit of the specified transmission pattern length, may be used. Same as subframes) may be short or long. In addition, the size of the feedback window 1120 and the feedback start subframe may be set identically or differently for each terminal. The size and start subframe number of the feedback window 1120 within the transmission pattern length may be transmitted to each terminal through higher signaling or broadcasted to all terminals through higher signaling. The feedback transmission pattern for each terminal may also be transmitted to each terminal through higher signaling.

FIG. 7 illustrates a feedback transmission pattern 1102-1104 of each terminal when a cell-specific feedback pattern length is three frames and CSI-RS 1100 transmission is generated in every second subframe. Each terminal performs channel estimation after receiving the CSI-RS 1100, and performs feedback transmission within the feedback window 1120 determined during the feedback pattern length 1106 by the predetermined pattern after performing channel estimation. Here, the feedback window 1120 may be set based on the size of the feedback window received through higher signaling and the starting subframe number, and the feedback transmission pattern is determined in the set feedback window 1120. For example, the terminal # 1 may use a pattern 023 (change pattern of a subframe transmitting feedback information) as shown by reference numeral 1102. Here, the feedback pattern 023 means a subframe number on the assumption that subframe # 5 is determined as a starting point. In this case, the terminal # 1 has a subframe # 5 (pattern 0: subframe # 5) 1110 in frame # 0 (1107) and a subframe # 7 (pattern 2: subframe ## in frame # 1 1108). Feedback is performed in subframe # 8 (pattern 4: third subframe after subframe # 5) 1112 in frame 211 1111 and frame # 2 1109. If the feedback pattern of each terminal is determined by any one terminal, the feedback pattern of each terminal may be generated by cyclic shifting the determined pattern. That is, in the UE # 1 in FIG. 7, the subframe number for reporting the channel state information is cyclically repeated # 5, # 7, # 8, # 5, ---. Accordingly, in the case of the UE # 1, the subframe change pattern is a subframe # 5 of the 0th change pattern in frame # 0, a subframe # 7 of the second change pattern in frame # 1, and a frame # 2 in frame # 2. In the subframe # 8 of the third change pattern, feedback is performed. Therefore, when the pattern 023 of the terminal # 1 is cyclically moved, the last 3 moves to the front, and the pattern of the terminal # 2 becomes 302, Likewise, if the pattern of UE # 2 is cyclically moved, the pattern 230 of UE # 3 is determined. This method allows all terminals to use the feedback resources equally. In addition to this method, a pattern of a corresponding terminal may be determined using a random variable generator based on a unique ID of each terminal, and the pattern of each terminal may be updated with a feedback pattern length period or a longer period.

 8 is a diagram illustrating a procedure for transmitting a CSI-RS by a base station according to an embodiment of the present invention.

Referring to FIG. 8, in step 700, the base station generates a period of a feedback transmission pattern and a feedback transmission pattern for each terminal in consideration of the number of terminals, feedback subbands, scheduling characteristics, and minimum time required for generating feedback information. do. Thereafter, in step 701, the base station transmits the period and feedback transmission pattern information of the feedback transmission pattern generated to each terminal through higher signaling. Here, the feedback transmission pattern period and the pattern information may have a structure as shown in FIG. 5, 6, or 7. That is, as shown in FIG. 5 of the first embodiment, the SB-CSI feedback sensitive to time change is performed before the WB-CSI feedback, and also every feedback period in order to prevent nonuniformity of the subband channel estimation error. The feedback transmission pattern period and the pattern information for cyclically transmitting the feedback of the plurality of subbands may be generated each time. In addition, as shown in FIGS. 6 and 7 of the second embodiment, the length of the cell-specific feedback transmission pattern and the feedback transmission pattern for each terminal for distributing feedback overhead transmitted from multiple terminals from a system perspective Can be generated. Thereafter, in step 702, the base station multiplexes the CSI-RS in the PDSCH region in the corresponding subframe every CSI-RS transmission period and transmits the multiplexed CSI-RS to the UE.

After transmitting the CSI-RS as described above, the base station can receive the feedback information transmitted from the terminal to analyze the channel state of the downlink. In this case, in the method for receiving the feedback information, the base station receives the first feedback information at the first time point of the first period and the second feedback information at the second time point of the second period. In this case, the first time point and the second time point are different time points from the start point of the first period and the second period.

The feedback information is information calculated by the terminal and fed back to the base station based on the channel state information reference signal (CSI-RS) transmitted by the base station at a predetermined time period. In addition, when the first feedback information is subband channel state information (SB-CSI) and the second feedback information is wideband channel state information (WB-CSI), the first time point at the start of the first period and the second period is It is located closer than the second time point. In addition, the base station transmits the feedback transmission pattern information to the terminal, the terminal generates the feedback information, based on the feedback transmission pattern to determine and transmit a sub-frame for the feedback transmission, the base station transmits the feedback information to the terminal Receive from The feedback transmission period is set based on the CSI-RS transmission period.

9 is a diagram illustrating a transmission and reception procedure of a terminal according to an embodiment of the present invention. Referring to FIG. 9, the terminal receives feedback transmission pattern period and feedback transmission pattern information transmitted from the base station through higher signaling in step 800. Thereafter, the terminal generates feedback information by receiving the CSI-RS transmitted by the base station every frame period, and provides the feedback transmission function to the base station using the generated feedback transmission pattern period and feedback transmission pattern information. Perform.

In detail, the UE acquires the CSI-RS after demultiplexing the PDSCH and the CSI-RS in the corresponding subframe every CSI-RS transmission period in step 801, and provides feedback for the CSI-RS based on the received CSI-RS in step 802. Generate channel status information. Thereafter, in step 803, the terminal determines the first subframe for feedback transmission in each frame according to the feedback transmission pattern period and the feedback transmission pattern. In step 804, the UE sequentially transmits feedback information on a plurality of subbands selected at a predetermined period from the first subframe in each frame to the BS through PUCCH, and the selected plurality of subbands are cyclically transmitted in each frame. Adjust it.

Thereafter, in step 805, the UE transmits feedback information for the selected multiple subbands in each frame, and then transmits wideband feedback information to the base station through the PUCCH after a predetermined period. Here, the constant period means a period for feeding back the channel state information of the plurality of subbands and broadband generated for one measurement time point, which is a CSI-RS transmission period or (CSI-RS transmission period + minimum calculation interval) period It is a short period in which all selected subband channel state information and broadband channel state information for one terminal can be transmitted. In this case, the terminal may transmit feedback information to the base station in the same manner as in FIG. 5, 6, or 7.

First, in the case of the first embodiment, the terminal performs the time-sensitive SB-CSI feedback before the WB-CSI feedback, and also to prevent the non-uniformity of the subband channel estimation error multiple subbands in every feedback period In step 800, the feedback transmission pattern period and the pattern information for cycling transmission of the received data are received. Thereafter, the UE acquires the CSI-RS 504 of the frame # 0 from the downlink information transmitted to the base station as shown in FIG. 5 in step 801, and generates feedback information and transmits feedback in steps 802 and 803. Determine the first subframe for. Thereafter, as shown in FIG. 5, the UE sequentially transmits feedback information sensitive to time delay (here, SB-CSI1 and SB-CSI2) in step 804, and is relatively insensitive to time delay in step 805. Feedback information (here, WB-CSI) is transmitted. In this case, the terminal adjusts the order so that the plurality of subbands selected in step 804 may be cyclically transmitted for each frame (in the case of FIG. 5, the cyclic adjustment is performed in order of SB-CSI2 and SB-CSI1 in another frame).

When the CSI-RS 505 of the next frame # 1 is received, feedback information is transmitted to the base station while repeating steps 802 to 805. In this case, the time-sensitive feedback information is transmitted first, and the feedback information is transmitted with the transmission order cyclically adjusted. That is, as shown in FIG. 5, the frame # 0 is transmitted in the order of SB-CSI1 and the SB-CSI2, but the next frame # 1 is transmitted in the order of SB-CSI21 and SB-CSI1.

In addition, in the second embodiment, the terminal receives feedback transmission pattern period and feedback transmission pattern information from the base station. Thereafter, the UE acquires the CSI-RS for each CSI-RS transmission period as shown in FIG. 6 and generates feedback information based on the received CSI-RS. Thereafter, the terminal determines the first subframe for feedback transmission according to the received feedback transmission pattern period and feedback transmission pattern information. In this case, as shown in FIG. 6, UE # 1 has a transmission pattern of "024", UE # 2 has a transmission pattern of "402", and UE # 3 has a transmission pattern of "240". In this case, when the minimum calculation interval elapses after receiving the CSI-RS in FIG. 6, pattern 0 becomes subframe # 5, pattern 2 becomes subframe # 7, and pattern 4 becomes subframe # 9. Accordingly, as shown in FIG. 6, in frame # 0, the UE # 1 transmits feedback information in subframe # 5, UE # 2 in subframe # 9, and UE # 3 in subframe # 7. In frame # 1, the UE # 1 transmits feedback information in subframe # 7, UE # 2 in subframe # 5, and UE # 3 in subframe # 9. In frame # 2, the UE # 1 transmits feedback information in subframe # 9, UE # 2 in subframe # 7, and UE # 3 in subframe # 5.

Accordingly, when the UE # 1 to the UE # 3 transmit feedback information in each frame, the feedback information is distributed and transmitted as shown in FIG. 6. This is achieved by setting the length of a cell-specific feedback transmission pattern and the feedback transmission pattern for each terminal to distribute feedback overhead transmitted from multiple terminals from a system perspective to the terminals.

In the third embodiment, the terminal receives feedback transmission pattern information set in a feedback transmission pattern period and a feedback window. Thereafter, the UE acquires the CSI-RS for each CSI-RS transmission period as shown in FIG. 7 and generates feedback information based on the received CSI-RS. Thereafter, the terminal determines the first subframe for feedback transmission according to the received feedback transmission pattern period and feedback transmission pattern information. In this case, as shown in FIG. 6, the UE # 1 has a transmission pattern of "023", the UE # 2 has a transmission pattern of "302", and the UE # 3 has a transmission pattern of "230". It is present in the feedback window as shown in FIG. In this case, after receiving the CSI-RS in FIG. 7, a transmission time point (where transmission time may be a time for channel estimation by receiving the CSI-RS, ie, may be a minimum calculation interval in the second embodiment) Then, pattern 0 becomes subframe # 5, pattern 2 becomes subframe # 7, and pattern 3 becomes subframe # 8. Accordingly, as shown in FIG. 6, in frame # 0, the UE # 1 transmits feedback information in subframe # 5, UE # 2 in subframe # 8, and UE # 3 in subframe # 7. In frame # 1, the UE # 1 transmits feedback information in subframe # 7, UE # 2 in subframe # 5, and UE # 3 in subframe # 9. In frame # 2, the UE # 1 transmits feedback information in subframe # 8, UE # 2 in subframe # 7, and UE # 3 in subframe # 5.

Accordingly, when the UE # 1 to the UE # 3 transmit feedback information in each frame, the feedback information is distributed and transmitted as shown in FIG. 6. This is achieved by setting the length of a cell-specific feedback transmission pattern and the feedback transmission pattern for each terminal to distribute feedback overhead transmitted from multiple terminals from a system perspective to the terminals.

As described above, the method for transmitting feedback information in the communication system according to the embodiment of the present invention generates first feedback information and transmits the first feedback information generated at the first time point of the first period. The second feedback information is generated, and the second feedback information generated at the second time point of the second period is transmitted. Here, the first time point and the second time point may be different from the start point of the first period and the second period.

The feedback information is calculated based on the channel state information reference signal (CSI-RS) transmitted at a predetermined time period. In addition, when the first feedback information is subband channel state information (SB-CSI) and the second feedback information is wideband channel state information (WB-CSI), a first time point at a start time point of the first period and the second period Is located closer than the second time point. The terminal may further include receiving the feedback transmission pattern information from a base station, generating feedback information, determining a subframe for feedback transmission based on the feedback transmission pattern, and then transmitting the feedback information to the base station. do. The feedback transmission period is set based on the CSI-RS transmission period.

10 is a diagram illustrating a structure of a transmitting apparatus of a base station according to an embodiment of the present invention.

Referring to FIG. 10, the base station scheduler 900 determines which UE to allocate a downlink resource by transmitting a PDCCH to determine the priority for each terminal. The base station scheduler 900 performs this task based on the channel state reported by each terminal. The controller 901 controls the operation of each other device based on the scheduler 900 decision. The controller 901 performs an operation for controlling the feedback procedure of the terminals as shown in FIG. 8.

 The CRS generator 902 generates a CRS which is a downlink common reference signal. The PDCCH generator 903 includes an encoder and a modulator. The PDCCH generator 903 encodes and modulates control information to be transmitted on the PDCCH to generate subcarrier symbols of the PDCCH channel. The CSI-RS generator 904 generates a channel state information reference signal CSI-RS for downlink channel state estimation. The DM-RS generator 905 generates a signal demodulation-reference signal (DM-RS) for demodulation. The PDSCH generator 906 encodes and modulates information to be transmitted in the PDSCH to generate subcarrier symbols of the PDSCH channel. That is, the generators 902-906 generate subcarrier symbols of CRS, PDCCH, CSI-RS, DeModulation-Reference Signal (DM-RS), and PDSCH channels, respectively, under the control of the controller 901. The multiplexer 907 multiplexes the subcarrier symbols generated by the generators 902-906 under the control of the controller 901, and the transmitter 908 converts the output of the multiplexer 907 into an RF signal. Output

At this time, the controller 901 controls the multiplexer 907 to multiplex each subcarrier so that the CRS is multiplexed in the PDCCH region and the CSI-RS and DM-RS are multiplexed in the PDSCH region. This is because CRS is used for channel estimation for demodulation of PDCCH, DM-RS is used for channel estimation for demodulation of PDSCH, and CSI-RS is used for downlink channel state estimation. The controller 901 controls the CSI-RS to be multiplexed on the PDSCH based on a predetermined CSI-RS transmission subframe number and a transmission period.

The controller 901 controls to transmit feedback transmission related control information including a feedback transmission pattern according to an embodiment of the present invention through higher signaling (eg, RRC). The feedback transmission control information may be patterns of the first embodiment as described above. The signaling information may be transmitted through a broadcasting channel (BCH). In addition, the controller 901 controls the multiplexer 907 to multiplex and transmit the CSI-RS signal for downlink channel state estimation to the PDSCH.

The above configuration illustrates a structure in which the base station generates a CSI-RS for downlink channel state estimation and then demultiplexes the PDSI to transmit the PDSCH. Although not shown, the base station receives the feedback information transmitted from the terminal and then demultiplexes the channel state of the downlink. In this case, the apparatus for receiving feedback information at the base station includes a receiver for receiving first feedback information at a first time point of a first period and receiving second feedback information at a second time point of a second period, And a controller for analyzing a state of a downlink channel from first and second feedback information, wherein the first time point and the second time point are different time points from the start point of the first period and the second period.

The feedback information is calculated based on the channel state information reference signal (CSI-RS) transmitted at a predetermined time period. The first feedback information is subband channel state information (SB-CSI) and the second feedback information is wideband channel state information (WB-CSI), and a first time point at a start point of the first period and the second period is It is located closer than the second time point. The base station for receiving the feedback information may include a transmitter for transmitting the feedback transmission pattern information, a receiver for receiving feedback information transmitted by the terminal in a subframe determined based on the feedback transmission pattern, and analyzing the feedback information. The controller may be configured to analyze the channel state of the downlink. The feedback transmission period is set based on the CSI-RS transmission period.

11 is a diagram illustrating a structure of a transmitting and receiving device of a terminal according to an embodiment of the present invention.

Referring to FIG. 11, the controller 1005 controls overall operations of transmission and reception of a terminal device. The controller 1005 controls the operation of the terminal device to transmit the feedback information to the base station according to the feedback transmission pattern period and feedback transmission pattern information transmitted from the base station in the same procedure as in FIG. 9.

The receiver 1000 converts an RF signal transmitted to a base station into a baseband signal. The demultiplexer 1001 demultiplexes the output of the receiver 1000 under the control of the controller 1005 and outputs CSI-RS, DM-RS, CRS, PDCCH, and PDSCH signals. That is, the controller 1005 controls the demultiplexer 1001 to distinguish CSI-RSs based on a predetermined CSI-RS transmission subframe number and a transmission period. The channel estimator 1002 receives the CRI-RS, the DM-RS, and the CRS output from the demultiplexer 1001. The channel estimator 1002 generates an estimated value after performing PDCCH channel estimation using the CRS, generates an estimated value after performing PDSCH channel estimation using the DM-RS, and uses a CSI-RS. Downlink channel state information is generated. The PDCCH decoder 1003 receives the PDCCH signal from the demultiplexer 1001 and demodulates, descrambles, and decodes the PDCCH signal using the PDCCH channel estimation signal output from the channel estimator 1002. Decode The PDSCH decoder 1001 receives the PDSCH signal from the demultiplexer 1001 and demodulates, descrambles, and decodes the PDSCH signal using the PDSCH channel estimation signal output from the channel estimator 1002.

 The PUCCH generator 1007 generates uplink control information under the control of the controller 1005. Here, the uplink control information may include a feedback signal according to an embodiment of the present invention. An uplink RS generator 1006 generates an uplink reference signal RS. The multiplexer 1008 multiplexes the reference signal RS and PUCCH control information under the control of the controller 1005. The transmitter 1009 converts the output of the multiplexer 1008 into an RF signal and outputs the RF signal.

Referring to the reception operation in the terminal device having the configuration as shown in FIG. 11, the demultiplexer 1001 demultiplexes the output of the receiver 1000 under the control of the controller 1005 to CSI-RS, DM-RS, CRS, PDCCH and PDSCH signals are output. The CSI-RS, DM-RS, and CRS are delivered to the channel estimator 1002. The channel estimator 1002 then performs channel estimation using the CRS and inputs the channel estimate to the decoder 1003 of the PDCCH. The PDCCH decoder 1003 decodes the PDCCH signal input from the demultiplexer 1001 using the CRS based estimation value received from the channel estimator 1002. The controller 1005 receives PDSCH allocation information and information for PDSCH demodulation and decoding from the PDCCH decoder 1003.

In addition, the channel estimator 1002 performs channel estimation using a DM-RS and inputs an estimated value to the decoder 1004 of the PDSCH. The PDSCH decoder 1004 decodes the PDSCH signal output from the demultiplexer 1001 using the DM-RS based estimation value received from the channel estimator 1002 and the PDSCH demodulation and decoding information received from the controller 1005. In this case, the controller 1005 controls to distinguish the PDSCH from the demultiplexer 1001 based on the PDSCH allocation information received from the PDCCH decoder 1003. The controller 1005 controls the demultiplexer 1001 to distinguish the CSI-RS based on a predetermined CSI-RS transmission subframe number and a transmission period, and applies the same to the channel estimator 1002 to downlink channel state information. Enable to create

The downlink channel state information generated by the channel estimator 1002 is transferred to the controller 1005, and the controller 1005 applies this information to the PUCCH generator 1007. The PUCCH generator 1007 then generates a feedback signal based on this information and applies it to the multiplexer 1008. The controller 1005 controls the multiplexer 1008 to multiplex the reference signal generated from the uplink reference signal generator 1006 and the feedback signal generated from the PUCCH generator 1007. This multiplexed signal is then transmitted via transmitter 1009.

Here, the controller 1005 receives feedback related control information received through higher signaling, and controls a feedback related operation for reporting channel estimated downlink channel state information to the base station using the feedback related control information. At this time, the controller 1005 controls the multiplexer 1008 as in the first embodiment of the present invention, multiplexes downlink channel state information on the PUCCH, and transmits feedback. Thus, the first subframe within each frame is determined. SB-CSI feedback information for a plurality of subbands is sequentially transmitted from the WB-CSI feedback information. In addition, the controller 1005 controls the multiplexer 1008 as in the second or second embodiment of the present invention, multiplexes downlink channel state information on the PUCCH, and transmits feedback to the PUCCH. It has a different pattern in length, and the feedback transmission pattern for each terminal transmits the channel state information of the downlink according to the feedback transmission pattern generated by cyclically moving a predetermined pattern in an arbitrary terminal.

Accordingly, as described above, the apparatus for transmitting feedback information of the terminal generates first feedback information and is transmitted at the first time point of the first period, and generates second feedback information and is transmitted at the second time point of the second period. A controller for controlling and a transmitter for transmitting the first and second feedback information by the controller, wherein the first time point and the second time point are different from each other at the start of the first and second periods. do.

The feedback information is calculated based on the channel state information reference signal (CSI-RS) transmitted at a predetermined time period. In addition, when the first feedback information is subband channel state information (SB-CSI) and the second feedback information is wideband channel state information (WB-CSI), a first time point at a start time point of the first period and the second period Is located closer than the second time point. The terminal may further include a channel estimator generating channel state information using a channel state information reference signal (CSI-RS) transmitted at a predetermined time period, and generating feedback information from the channel state information, based on a feedback transmission pattern. The controller is configured to determine a subframe in which to transmit the signal, and a transmitter for transmitting the feedback information to the base station. The feedback transmission period is set based on the CSI-RS transmission period.

Embodiments of the present invention disclosed in the specification and drawings are only specific examples to easily explain the technical contents of the present invention and aid the understanding of the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

Claims (20)

1. In the method for transmitting feedback information in a communication system,

   Generating first feedback information;

   Transmitting the first feedback information at a first time point of a first period;

   Generating second feedback information;

   And transmitting the second feedback information at a second time point of a second period.

   Wherein the first time point and the second time point are different time points from the start point of the first period and the second period.
2. The method of claim 1, wherein the feedback information is calculated based on a channel state information reference signal (CSI-RS) transmitted at a predetermined time period.
3. The start of the first period and the second period when the first feedback information is subband channel state information (SB-CSI) and the second feedback information is wideband channel state information (WB-CSI). And a first time point is located closer to the second time point than the second time point.
4. The method of claim 1, wherein the feedback information is transmitted by a terminal, and the terminal,

   Receiving the feedback transmission pattern information from a base station;

   Generating feedback information,

   Determining a subframe to be subjected to feedback transmission based on the feedback transmission pattern;

   And transmitting the feedback information to a base station.
5. The method of claim 1, wherein the feedback transmission period is set based on a CSI-RS transmission period.
6. In the method for receiving feedback information in a communication system,

   Receiving first feedback information at a first time point in the first period;

   And receiving second feedback information at a second time point of the second period.

   Wherein the first time point and the second time point are different time points from the start point of the first period and the second period.
7. The method of claim 6, wherein the feedback information is calculated based on a channel state information reference signal (CSI-RS) transmitted at a predetermined time period.
8. 7. The method of claim 6, wherein the first feedback information is subband channel state information (SB-CSI) and the second feedback information is wideband channel state information (WB-CSI), and a start time point of the first period and the second period is provided. Wherein the first time point is located closer than the second time point.
9. The method of claim 6, wherein the feedback information is transmitted from a terminal, the terminal,

   Receiving the feedback transmission pattern information from a base station;

   Generating feedback information,

   Determining a subframe to be subjected to feedback transmission based on the feedback transmission pattern;

   And transmitting the feedback information to a base station.
10. The method of claim 6, wherein the feedback transmission period is set based on a CSI-RS transmission period.
11. An apparatus for transmitting feedback information in a communication system,

    A controller which generates first feedback information and is transmitted at a first time point of the first period, and generates second feedback information and controls to be transmitted at a second time point of the second period;

    A transmitter for transmitting the first and second feedback information by the controller,

    Wherein the first time point and the second time point are different time points from the start point of the first period and the second period.
12. The apparatus of claim 11, wherein the feedback information is calculated based on a channel state information reference signal (CSI-RS) transmitted at a predetermined time period.
13. The start of the first period and the second period when the first feedback information is subband channel state information (SB-CSI) and the second feedback information is broadband channel state information (WB-CSI). And a first view point is located closer than the second view point.
14. The method of claim 11, wherein the feedback information is transmitted by a terminal, and the terminal,

    A channel estimator for generating channel state information using a channel state information reference signal (CSI-RS) transmitted at a predetermined time period;

    A controller for generating feedback information from the channel state information and determining a subframe to which the feedback information is to be transmitted based on a feedback transmission pattern;

    And a transmitter configured to transmit the feedback information to a base station.
15. 12. The apparatus of claim 11, wherein the feedback transmission period is set based on a CSI-RS transmission period.
16. An apparatus for receiving feedback information in a communication system,

    A receiver for receiving first feedback information at a first time point in the first period and receiving second feedback information at a second time point in the second period;

    A controller for analyzing a state of a downlink channel from the first and second feedback information,

    Wherein the first time point and the second time point are different time points from the start point of the first period and the second period.
17. The apparatus of claim 16, wherein the feedback information is calculated based on a channel state information reference signal (CSI-RS) transmitted at a predetermined time period.
18. 17. The method of claim 16, wherein the first feedback information is subband channel state information (SB-CSI) and the second feedback information is wideband channel state information (WB-CSI), and a start time point of the first period and the second period is provided. And the first time point is closer to the second time point than the second time point.
19. The method of claim 16, wherein the base station for receiving the feedback information, a transmitter for transmitting the feedback transmission pattern information, a receiver for receiving feedback information transmitted in a subframe determined by the terminal based on the feedback transmission pattern, and Feedback information receiving device, characterized in that configured to analyze the feedback information to analyze the channel state of the downlink.
20. The apparatus of claim 16, wherein the feedback transmission period is set based on a CSI-RS transmission period.

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