KR101644471B1 - Method and Apparatus for designing structure of periodic feedback for reporting channel state information of multiple users in wireless communication systems - Google Patents

Abstract

In a downlink of a wireless communication system, a base station requires downlink channel state information for each UE in order to perform link adaptive transmission to the UEs. The channel state information is generated by receiving a reference signal transmitted by the UEs on the downlink, and the generated channel state information is fed back to the base station through an uplink control channel. Therefore, the feedback timing and period of the transmission period and channel state information of the reference signal can affect the error of the channel state at the time when the base station receives the feedback from the terminal and the channel state at the time when data is actually transmitted to the terminal. Therefore, if the feedback structure of the appropriate channel state information according to the transmission period of the reference signal is not designed, it leads to inefficient link adaptive transmission and degrades the system performance. The present invention aims to equalize channel state errors to be generated in a plurality of UEs in a link adaptive transmission when a reference signal for downlink channel state estimation is transmitted over a long period and to overhead generated by channel state information feedback The present invention also provides a method and apparatus for designing an uplink periodic feedback structure that disperses the uplink periodic feedback structure. Also, a method of setting a feedback period for each UE considering the channel characteristics of multiple UEs in the periodic feedback structure of the present invention is provided.

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method and an apparatus for designing a periodic feedback structure for reporting channel state information of multiple users in a wireless communication system,

In a cellular wireless communication system, when a reference signal for downlink channel state estimation is transmitted over a long period, a downlink channel state at a time when a base station receives feedback from the terminal and a channel To an apparatus and method for designing an uplink periodic feedback structure for reducing an error of state and distributing overhead generated by channel state information feedback of multiple terminals from a system point of view.

The mobile communication system has evolved into a high-speed and high-quality wireless packet data communication system for providing data service and multimedia service apart from providing initial voice-oriented service. A variety of mobile communication standards such as HSDPA (High Speed Downlink Packet Access), HSUPA (High Speed Uplink Packet Access), 3GPP2 HRPD (High Rate Packet Data) Was developed to support.

Existing third generation wireless packet data communication systems such as HSDPA, HSUPA, and HRPD use technologies such as Adaptive Modulation and Coding (AMC) and Channel Adaptive Scheduling to improve transmission efficiency. With 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 state is not good, the amount of data to be transmitted is reduced so that the probability of receiving error is adjusted to a desired level. If the channel state is good, the amount of data to be transmitted is increased so that the probability of receiving error can be effectively transmitted. Using the above-described channel-responsive scheduling resource management method, the transmitter selectively services a user having a good channel state among a plurality of users, thereby increasing the system capacity as compared to providing a channel to a user and providing a service. This increase in capacity is called a so-called multi-user diversity gain. In other words, the AMC method and the channel-responsive scheduling method are based on feedback of partial channel state information from a receiver and apply a proper modulation and coding scheme to a time point determined to be the most efficient.

Recently, studies have been actively conducted to convert Code Division Multiple Access (CDMA), which is a multiple access scheme used in second and third generation mobile communication systems, into OFDMA (Orthogonal Frequency Division Multiple Access) in the next generation system. 3GPP and 3GPP2 have begun to standardize on evolutionary systems using OFDMA. It is known that the capacity increase can be expected in the OFDMA system as compared with the CDMA system. One of the various causes of capacity increase in the OFDMA scheme is that frequency domain scheduling can be performed on the frequency axis. As the channel gains the capacity gain by the channel adaptive scheduling method according to the time varying characteristics, the channel gain the capacity gain by using different characteristics according to the frequency.

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

1, one subframe 115 is composed of 14 OFDM symbols 100 to 113, and an area allocated for a control channel (PDCCH) is divided into three front OFMA symbols 100 to 102) and the area allocated for the data channel (Physical Downlink Data CHannel, hereinafter PDSCH) is the remaining OFDM symbols 103 to 113. PDCCH is transmitted over the entire system band in the PDCCH regions 100 to 102, but the PDSCH is transmitted based on a resource block (RB) 114, which is a basic unit of scheduling. Here, each RB is composed of 12 subcarriers, and the total number of RBs varies depending on the system bandwidth. The reason for locating the area for the PDCCH at the forefront of the subframe is that if the UE first confirms the PDCCH and there is no data corresponding to the PDCCH, the micro sleep mode is taken to reduce the power consumption of the UE in the data channel region It is for this reason.

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

2, one resource element (hereinafter referred to as RE) refers to one subcarrier 203 in one OFDM symbol 201, and one RB 202 in one subframe 200 includes 12X14 REs. The receiver receives the CRSs 210 to 213 corresponding to the antennas 204 to 207 and estimates the channel state for each transmission antenna. For this purpose, each antenna 204-207 transmits a null signal 208 to the RE region of the CRS transmitted from another antenna as shown in FIG. That is, the antenna 0 204 transmits the null signal 208 to the RE positions of the CRSs 211 to 213 transmitted from the other antennas 205 to 207. CRS 210 and 211 for antenna 0 204 and antenna 1 205 in one RB 202 are transmitted in 8 REs respectively and CRS 210 and 211 for antenna 2 206 and antenna 3 207 are transmitted in 8 REs, 212, and 213 are transmitted in four REs, respectively. Therefore, in the case of four Tx antennas, the CRS is transmitted using a total of 24 REs per RB 202. The receiver receives the CRS, estimates the channel, and uses the PDSCH 209 for demodulation or to generate downlink channel status 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 in the demodulation is smaller than the error required in generating the downlink channel state information.

The UE receives a CRS shown in FIG. 2 for all RBs in every subframe, estimates a channel, and outputs a Rank Indicator (RI), a Channel Quality Indicator (CQI) ), And a precoding matrix indicator (PMI).

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

The RI, CQI, and PMI information representative of channel conditions experienced by one UE are transmitted to the Node B according to the uplink feedback structure shown in FIG. In FIG. 3, parameters P (= Np), K, M and O for determining the feedback structure are transmitted to the UE through upper signaling, and the definition and range of each parameter are as follows.

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

- O: offset of RI reporting and broadband CQI / PMI reporting, O I {0, -1, ... , - (P - 1), - P},

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

- Np, NOFFSET, CQI: Period for subband CQI feedback and offsets, determined by cqi-pmi-ConfigurationIndex,

- MRI, NOFFSET, RI: RI reporting period and offset, determined by ri-ConfigurationIndex.

Here, the subband means a group of one or more consecutive RBs. The time-sensitive subband CQI feedback period 302 is relatively shorter than the RI 303 and the broadband CQI / PMI feedback 305 period. Then, since the subband CQI feedback must be performed for all K representative subbands in the J frequency band portions, CQI feedback is performed for all JXK subbands once the wideband CQI / PMI feedback occurs (304 ), And the broadband CQI / PMI feedback period is (JXK + 1) XP (300,301). Because RI is very insensitive to time, it is fed back to the longest period and sets offset O (306) to prevent transmission collisions with other feedback information.

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

In FIG. 4, channel state information reference signals (CSI-RSs) 402 and 403 for downlink channel state estimation are transmitted in one frame period 404. That is, the CSI-RS is transmitted in only one specific subframe within one frame 400 or 401 composed of 10 subframes. The reason why the CSI-RS is rarely transmitted is that the CSI-RS in the LTE-A system is used only for the downlink channel state estimation, as mentioned above. The UEs 407 to 409 receiving the CSI-RS 402 and 403 transmit the corresponding channel state information in the uplink after the minimum calculation time 410 and 411 required to generate the downlink channel state information has elapsed (412-414). At this time, due to the long CSI-RS transmission period 404, several sub-band channel state information and wide-band channel state information are fed back within that transmission period, and when information is fed back, Of the total.

Therefore, it is necessary to design an uplink feedback structure considering feedback channel state information characteristics. In addition, when a plurality of UEs perform immediate feedback after channel estimation from the CSI-RS to reduce the error of the channel state, the uplink overhead can be concentrated in one subframe. Therefore, it is necessary to design a feedback structure that distributes the uplink feedback overhead while maintaining the error of the channel state information fed back by the plurality of UEs uniformly among the UEs.

FIG. 5 is a diagram illustrating a conventional uplink feedback structure considering downlink reference signal transmission in the LTE-A system. Referring to FIG. 5, a cell-specific feedback transmission pattern length 506 and terminal-specific feedback transmission patterns 502 to 504 are used to distribute feedback overhead transmitted from multiple terminals from a system point of view. And defines a feedback window 520. [ The feedback window 520 prevents duplication of feedback transmitted during the subframe period from the CSI-RS measurement to the completion of the feedback information generation, and enables effective management of feedback resources of a plurality of terminals from a system point of view. The feedback transmission patterns 502 to 504 of the UEs set the UEs to use the feedback resources as uniformly as possible within the pattern length 506 thereof. This is to maintain the fairness of feedback transmission between UEs. At this time, the feedback transmission patterns 502 to 504 are set in the feedback window 520. The size of the feedback window 520 can not be greater than the transmission period of the CSI-RS 500 and this size can be set to be the same or different for each frame 507 to 509 in the transmission pattern length 506 have. The start frame of the feedback window 520 may also be set to be the same or different for each frame 507 to 509 in the length 506 of the transmission pattern. 5 shows an example in which a CSI-RS transmission period is set as one frame, and the CSI-RS transmission period may be shorter or longer than the above, and accordingly, one frame (10 frames Frame) may be short or long. Additionally, the size of the feedback window 520 and the feedback starting subframe may be set equal or different for each terminal

FIG. 5 is a conventional feedback structure, in which all terminals perform periodic feedback using the same feedback window. This can reduce the utilization of the entire control channel of the uplink available as feedback, and can also inhibit setting different feedback periods for the terminals with different mobility. Therefore, it is necessary to design an uplink feedback structure that improves the utilization of uplink control channel resources for feedback of downlink channel information and enables setting of different feedback periods for terminals having different mobility.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for estimating a downlink channel state in a wireless communication system when a period of a reference signal transmitted for a downlink channel state estimation is long, And a method and an apparatus for designing an uplink periodic feedback structure for efficiently distributing overhead generated by feedback of multiple terminals from a system point of view. Also, an uplink periodic feedback structure designing method and apparatus are provided that enable a UE having different mobility to set a suitable feedback period.

According to an aspect of the present invention, there is provided a method for transmitting a feedback control information for a periodic channel status report of a mobile station in a mobile communication system, the method comprising: receiving feedback information including at least one feedback window periodically generated for a cell- Setting a feedback transmission pattern for channel status reporting according to each terminal within the feedback window, and transmitting the set feedback control information to the terminal.

Also, in the mobile communication system according to the present invention for achieving the above-described method, a base station apparatus for generating and transmitting feedback control information for cyclic channel state reporting of a terminal includes at least one feedback periodically generated for a cell- A controller for setting windows, setting a feedback transmission pattern for channel status reporting in the feedback window according to each terminal, and a transmitter for transmitting the set feedback control information to the terminal.

The method of reporting periodic channel state information of a terminal in a mobile communication system of the present invention includes receiving feedback control information transmitted from a base station, generating channel state information using a reference signal transmitted from the base station, And transmitting the generated channel state information to the base station according to a feedback transmission pattern set in at least one feedback window periodically generated for the cell characterized feedback transmission pattern length determined according to the information .

In addition, in a mobile communication system for achieving the above-described method, a terminal periodically reporting channel state information to a base station includes a receiver for receiving feedback control information transmitted from the base station, a channel estimating unit for estimating a channel using the reference signal transmitted from the base station, A channel estimator for generating channel state information, and a feedback transmission pattern set in at least one feedback window periodically occurring for a cell-characterized feedback transmission pattern length determined according to the feedback control information, And to transmit status information to the base station.

As described above, according to the present invention, when a reference signal for downlink channel estimation is transmitted in a long period, a method of grouping uplink feedback resources for periodic feedback transmission of multiple terminals, . Also, a signaling scheme for cyclic feedback proposed by the present invention is also proposed. Thus, it is possible to efficiently operate the system by dispersing the feedback overhead generated from a plurality of terminals from the viewpoint of the system, and to maintain the equality in terms of the performance of the channel state errors for each terminal. In addition, the present invention enables setting of different feedback periods for each mobile station considering channel characteristics such as mobility of each mobile station.

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 is a diagram illustrating a cyclic feedback structure that is transmitted on an uplink control channel in an LTE system;
4 is a diagram illustrating a downlink reference signal transmission structure and an uplink feedback structure in an LTE-Advanced system,
5 is a diagram illustrating a conventional uplink feedback structure considering downlink reference signal transmission in an LTE-Advanced system,
6 is a diagram illustrating an uplink feedback structure and method for a plurality of UEs grouped by grouping feedback resources according to a first embodiment of the present invention;
7 is a diagram illustrating an uplink feedback structure and method for feedback cycle adjustment of multiple terminals in a feedback structure composed of feedback resource groups according to a second embodiment of the present invention.
8 is a diagram illustrating a transmission procedure of a base station according to the first and second embodiments of the present invention.
9 is a diagram illustrating a transmission / reception procedure of a terminal according to the first and second embodiments of the present invention.
10 is a diagram showing the structure of a base station transmitting apparatus according to the present invention,
11 is a diagram illustrating a structure of a transceiver of a terminal according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and these may be changed according to the intention of the user, the operator, or the like. Therefore, the definition should be based on the contents throughout this specification.

While the embodiments of the present invention will be described in detail, the OFDM-based wireless communication system, particularly the 3GPP EUTRA standard, will be the main object of the present invention, but the main point of the present invention is to provide a communication system It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

In the present invention, the transmission of the reference signal over a long period means that the reference signal is not continuously transmitted in all subframes. That is, when the reference signal is transmitted in all the subframes, it can be defined that the reference signal is transmitted in a short period. If the reference signal is not transmitted in all the subframes but in a subframe corresponding to a multiple of 5 It can be defined that the reference signal to be transmitted is transmitted in a long cycle.

The present invention proposes a method and apparatus for an uplink feedback structure for cyclic feedback of terminals, and defines a plurality of feedback windows for this purpose. The following basic elements are needed to define multiple feedback windows.

Basic element -> number of the feedback window, the size of each feedback window, feedback transmission pattern of each terminal of each feedback window

Considering the following concurrent elements in combination with the basic elements, utilization of the uplink feedback resources can be improved.

Concurrent element -> cell characterized feedback pattern length, timing offset of each feedback window

Also, considering the following additional elements based on the basic elements, the feedback periods of the respective terminals can be set differently.

Detail element -> of the respective nodes by feedback window enable and disable indicator, the period for the multiple feedback transmission within the active window feedback, the same CSI-different forms when the feedback information generated by the RS-based channel status information (sub-band or broadband) Generate or generate channel state information for different subbands

A method and an apparatus for designing a cyclic uplink feedback structure of downlink channel state information according to the present invention will be described in detail with reference to the first and second embodiments through the following embodiments.

In this case, the first embodiment describes an example in which a plurality of feedback windows are defined based on the basic elements and concurrent elements, and the utilization of uplink feedback resources is improved.

Further, the second embodiment describes an example of setting a feedback period of each terminal differently while defining a plurality of feedback windows based on the basic elements and additional sub-elements.

<< First Example >>

6 illustrates an uplink feedback structure and a method for a plurality of UEs grouped by grouping feedback resources according to the first embodiment of the present invention. FIGS. 6A and 6B show the uplink feedback structure and method, respectively, when the feedback resources are grouped into a case of allowing overlap between groups and a case of not allowing overlap between groups.

6A, when the length 606 of the cell-specific feedback transmission pattern and the setting of the feedback transmission patterns 602 to 604 for each terminal for efficiently distributing the feedback overhead transmitted from the multiple terminals from the system point of view, It is proposed to introduce a plurality of feedback windows 620, 621.

In this case, each feedback window may consist of consecutive uplink subframe resources and may consist of discontinuous uplink subframe resources. And, you can allow some overlap between feedback windows. If the feedback window consists of consecutive subframe resources, these multiple feedback windows can be specified by the timing offset information (618, 619) and window size of each feedback window. In order to set the multiple feedback windows, the base station may transmit the timing offset information 618 and 619 of each feedback window and the window size unicast or multicast to the UEs through upper signaling, or each feedback window may be fixedly determined in advance.

On the other hand, if the feedback window is composed of discontinuous subframe resources, these multiple feedback windows may be specified according to the frame number and subframe number within the cell-characterized feedback transmission pattern length 606. In this case, the base station sets the feedback window by indicating the frame number and the subframe number within the cell-specific feedback transmission pattern length 606. The feedback window setting may be unicast or multicast transmission to the base station through the higher signaling, or fixedly determined in advance.

As in FIG. 6A, the feedback windows 620 and 621 are periodically generated based on the cell-specific feedback transmission pattern length 606. The feedback windows 620 and 621 enable efficient distribution and management of feedback resources of multiple terminals in the CSI-RS 600 transmission system. The feedback transmission patterns 602 to 604 of the UEs can be set such that the UEs can use the feedback resources as uniformly as possible within the cell-characterized feedback transmission pattern length 606 to maintain the fairness of the feedback transmission between the UEs to be. At this time, the feedback transmission patterns 602 to 604 of the terminals are set in the feedback windows 620 and 621. The size of the feedback windows 620 and 621 can not be greater than the cell-characterized feedback transmission pattern length 606. [ The feedback transmission pattern for each terminal in the transmission pattern length can be transmitted to each terminal through upper signaling.

6A shows an example in which the CSI-RS transmission period is set to one frame, and the CSI-RS transmission period may be shorter or longer than the above, and accordingly, one frame (10 frames Frame) may be short or long. In addition, the sizes of the feedback windows 620 and 621 and the feedback start subframe may be set to the same or different for each terminal.

6A shows the feedback transmission patterns 602 to 604 of each UE when the cell-specific feedback transmission pattern length 606 is three frames and the CSI-RS 600 transmission occurs in every second subframe . Each terminal performs channel estimation after receiving the CSI-RS 600, and then transmits feedback in predetermined feedback windows 620 and 621 during a feedback pattern length 606 according to a predetermined pattern. Here, the feedback windows 620 and 621 may be set based on the size and timing offset 618 and 619 of the feedback window received through the upper signaling, and the feedback transmission patterns of the terminals may be set in the feedback windows 620 and 621, All. In the case of the terminal # 1, the pattern is 03 (the change pattern of the subframe transmitting the feedback information), and the first 0 is the subframe # 4 in the frame # 0 (607) Frame # 0 607 indicates subframe # 4 (pattern 0) 610, and the second 3 indicates that subframe # 2 in frame # 1 608 is the start point of feedback window # 2 And the feedback is performed in the subframe # 5 (pattern 3) 611, which means a subframe number assuming a predetermined case. The pattern for each terminal can be generated by cyclic shifting an arbitrary pattern or randomly generated based on the unique ID of each terminal. The pattern of each terminal can be updated with a feedback pattern length period or a longer period.

6B shows an uplink feedback structure and method in a case where the overlap between feedback windows is not allowed unlike the case of FIG. 6A.

6B, if the feedback windows 690, 691 are defined in succession, the start point of each feedback window 690, 691 can be set with one timing offset 678. [ However, if the feedback windows 690 and 691 are discontinuous, a timing offset for each feedback window must be defined to set the starting point of each feedback window. Therefore, the size of the feedback window and the timing offset information are required for setting the feedback windows 690 and 691, and these information can be transmitted unicast or multicast to each terminal or a plurality of terminals through upper signaling. Here, the feedback window size and the timing offset information can be simplified by limiting the degree of freedom in setting the feedback window. In addition, this feedback window setting can be fixedly predetermined.

As in FIG. 6B, feedback windows 690 and 691 are generated with a period of the cell-specific feedback transmission pattern length 656. This feedback window 690, 691 enables efficient distribution and management of feedback resources of multiple terminals in the CSI-RS 650 transmission system. The feedback transmission patterns 652 to 654 of the UEs can be set such that the UEs can uniformly utilize the feedback resources available in the cell-characterized feedback transmission pattern length 656 to maintain the fairness of the feedback transmission between the UEs to be. At this time, the feedback transmission patterns 652 to 654 are set in the feedback windows 690 and 691. The size of the feedback windows 690, 691 can not be greater than the cell-characterized feedback transmission pattern length 656. The feedback transmission pattern for each terminal in the transmission pattern length can be transmitted to each terminal through upper signaling. 6B shows an example in which the CSI-RS transmission period is set to one frame, and the CSI-RS transmission period may be shorter or longer than that, and accordingly, one frame (10 frames Frame) may be short or long. In addition, the sizes of the feedback windows 690 and 691 and the feedback start sub-frame may be set to the same or different for each terminal.

6B shows feedback transmission patterns 652 to 654 of each UE when the CSI-RS 650 transmission is generated in every second subframe, where the cell-characterized feedback pattern length is three frames. Each terminal performs channel estimation after receiving the CSI-RS 650, and then transmits feedback in predetermined feedback windows 690 and 691 during a feedback pattern length 656 according to a predetermined pattern. Here, the feedback windows 690 and 691 can be set based on the size and the timing offset 678 of the feedback window received via the upper signaling, and the feedback transmission pattern is determined within the set feedback windows 690 and 691. In the case of the terminal # 1, the pattern is 03 (the change pattern of the subframe transmitting the feedback information), and the first 0 is the subframe # 4 in the frame # 0 (657) (Pattern 0) 660 in the frame # 0 657 and the subframe # 2 in the frame # 1 658 as the start point of the feedback window # 2 And the feedback is performed in the subframe # 5 (pattern 3) 661, which means a subframe number assuming a predetermined case. The pattern for each terminal can be generated by cyclic shifting an arbitrary pattern or randomly generated based on the unique ID of each terminal. The pattern of each terminal can be updated with a feedback pattern length period or a longer period.

<< Second Example >>

7 illustrates an uplink feedback structure and a feedback method for feedback period adjustment of multiple terminals in a feedback structure composed of feedback resource groups according to a second exemplary embodiment of the present invention.

In the case of the first embodiment, the average feedback period of the UEs is the same, while in the second embodiment, a feedback window based uplink feedback structure and method are proposed in which feedback periods of the multiple UEs can be set differently. The different mobility of the terminals determines the degree of temporal variation of the channel experienced by the terminal, and thus the feedback period of the terminal must be set in consideration of such channel characteristics. FIG. 7 shows a method of setting the periods of the plurality of terminals differently when the overlapping of the feedback windows is not allowed. However, when the present invention permits overlapping between windows by the same principle, Of course, can be applied.

To this end, the terminals may receive a timing offset 718 indicating the start point of the feedback window from the base station and the size of each window via upper signaling to set the multiple feedback windows 720 and 721. This information may be fixed and predetermined. These feedback windows 720 and 721 are defined within the cell-characterized feedback transmission pattern length 706 and are present at intervals of the feedback pattern length 706. In order to allow different feedback periods to be set for each terminal in the feedback window-based feedback structure, it is possible to feedback (multiple periodic feedback) the channel status report multiple times in a specific feedback window in the feedback windows 720 and 721, The feedback window introduces a method that does not feed back the channel status report. Considering the multiple periodic feedback transmission, as shown in FIG. 7, feedback of the terminal # 2 is allowed to be 5 ms (one subframe is 1 ms) by allowing a plurality of periodic feedbacks in the feedback window # 2 721 to the terminal # 2 713 of the frame # 1 708 and the subframe # 2 715 of the frame # 2 709 in the period of the frame # To this end, the indicator of the feedback window that allows multiple feedbacks and the feedback period in the feedback window should be informed to the terminal through higher signaling. When a plurality of feedbacks are transmitted within the CSI-RS 700 transmission period (that is, when a plurality of feedbacks are transmitted by measuring the CSI-RS at the same time), the information of each feedback may be transmitted to other subbands Lt; / RTI &gt; channel information.

On the other hand, considering that the feedback is not transmitted in the specific feedback window, feedback transmission is not allowed in the feedback window # 2 721 to the terminal # 3 as shown in FIG. Accordingly, the terminal # 3 transmits the feedback based on the pattern 704 determined in the feedback window # 1. For the operation of such a terminal, the base station can transmit an indicator indicating the inactivation or activation of each feedback window to the terminal through upper signaling. FIG. 7 is an example of a case where overlap between feedback windows is not allowed; the present invention can be equally applied to other feedback window-based feedback structures.

The second embodiment may include various detailed structures other than the structure shown in FIG. That is, the periodic feedback 722 set to the terminal # 2 in the feedback window # 2 721 can be transmitted in the feedback window # 2 721 in a predetermined pattern or a randomly generated pattern rather than a specific period.

The upper signaling information for the feedback window-based uplink feedback proposed in the first and second embodiments includes a cell-specific feedback pattern length, timing offsets and sizes of multiple feedback windows, activation and deactivation of each feedback window An indicator, a cycle for multiple feedbacks in the active feedback window, and a feedback transmission pattern in each feedback window. Here, each information may be set to be the same or different for each terminal.

FIG. 8 shows a transmission procedure of a base station according to the first and second embodiments of the present invention. In step 800, the BS calculates the feedback transmission information, i.e., the period of the feedback transmission pattern for each UE, the timing offsets and sizes of the feedback windows, the activation of each feedback window, and the feedback window size in consideration of the number of UEs connected thereto, the number of feedback subbands, A deactivation indicator, a cycle for transmitting a plurality of feedbacks in the active feedback window, and a feedback transmission pattern in each feedback window.

More specifically, the base station according to the first exemplary embodiment sets at least one feedback window periodically generated for a cell-specific feedback transmission pattern length. In this case, the at least one feedback window may consist of consecutive uplink subframe resources or discontinuous uplink subframe resources. A feedback window composed of consecutive UL subframe resources may be specified according to the timing offset information and the window size. Also, a feedback window composed of discontinuous uplink subframe resources may be specified according to a frame number and a subframe number within a feedback pattern length.

In the feedback window, the base station sets a feedback transmission pattern for channel state reporting according to each terminal.

On the other hand, the base station according to the second embodiment may set an average feedback period for the feedback transmission pattern different for each mobile station. To this end, the base station allows the channel status report to be fed back multiple times in a specific feedback window for any terminal, and not in another specific feedback window.

In step 801, the base station transmits a feedback signal including a period of a feedback transmission pattern generated to each terminal through upper signaling, timing offsets and sizes of feedback windows, an activation and deactivation indicator of each feedback window, , And transmits the feedback transmission pattern information in each feedback window.

In step 802, the base station transmits the CSI-RS to the PDSCH region in the corresponding subframe for each CSI-RS transmission period and multiplexes the CSI-RS to the UE.

FIG. 9 illustrates a transmission / reception procedure of a terminal according to the first and second embodiments of the present invention.

In step 900, the MS receives feedback control information, i.e., a feedback transmission pattern period, timing offsets and sizes of feedback windows, an activation and deactivation indicator of each feedback window, And feedback transmission pattern information in each feedback window.

The UE acquires CSI-RS after demultiplexing PDSCH and CSI-RS in the corresponding subframe every CSI-RS transmission period in step 901. FIG.

In step 902, the UE generates a plurality of sub-band channel state information and wide-band channel state information for feedback based on the received CSI-RS. In step 903, the UE generates a sub-frame for feedback transmission in each frame according to a feedback transmission pattern period, a timing offset and size of active feedback windows, a period for transmitting a plurality of feedbacks in an active feedback window, Frame.

In step 904, the UE sequentially transmits feedback information on multiple subbands and wide bandwidths to the base station through the PUCCH in the determined subframes in each frame. More specifically, the UE according to the first exemplary embodiment is configured to determine, based on a feedback transmission pattern set in at least one feedback window periodically generated for a cell-characterized feedback transmission pattern length determined according to the feedback control information, Information to the base station.

In addition, the UE according to the second embodiment may feedback the channel status report a plurality of times in a specific feedback window and not feedback the channel status report in another specific feedback window. To this end, the terminal may receive a feedback window indicator allowing feedback from the base station a plurality of times, and an indicator indicating whether to enable or disable the feedback period and the feedback window.

At this time, the multiple subbands can adjust the transmission order cyclically for each frame. The base station sets each terminal to perform feedback of channel state information for a plurality of subbands for a short time delay considering a time delay from a CSI-RS measurement time point to a feedback time point of each terminal, Lt; RTI ID = 0.0 &gt; channel state information &lt; / RTI &gt;

10 shows a structure of a base station transmitting apparatus according to the present invention.

In FIG. 10, the Node B scheduler 1000 determines which UE is to be allocated a downlink resource by transmitting a PDCCH, and assigns priority to each UE. The base station scheduler 1000 performs this operation based on the channel state information reported by each terminal.

The controller 1001 controls the operation of each of the other devices based on the scheduler 1000 determination. In other words, the controller 1001 transmits CRS, PDCCH, CSI, and PDSCH through the CRS generator 1002, the PDCCH generator 1003, the CSI-RS generator 1004, the DM-RS generator 1005, and the PDSCH generator 1006, -RS, a demodulation-reference signal (DM-RS), and subcarrier symbols of PDSCH channels. The generated subcarrier symbols are multiplexed by the multiplexer 1007 and transmitted to the mobile station through the transmission process of the transmitter 1008. Here, the controller 1001 calculates feedback transmission information, that is, a period of a feedback transmission pattern for each terminal, timing offsets and sizes of feedback windows, and a feedback window size for each feedback window in consideration of the number of terminals belonging to the base station, An activation and deactivation indicator, a cycle for transmitting multiple feedbacks in the active feedback window, and a feedback transmission pattern within each feedback window.

More specifically, the controller 1001 according to the first exemplary embodiment sets at least one feedback window that occurs periodically with respect to the cell-specific feedback transmission pattern length. In this case, the at least one feedback window may consist of consecutive uplink subframe resources or discontinuous uplink subframe resources. A feedback window composed of consecutive UL subframe resources may be specified according to the timing offset information and the window size. Also, a feedback window composed of discontinuous uplink subframe resources may be specified according to a frame number and a subframe number within a feedback pattern length. In the feedback window, the controller 1001 sets a feedback transmission pattern for channel status reporting according to each terminal.

Meanwhile, the controller 1001 according to the second embodiment may set an average feedback period for the feedback transmission pattern to be different for each terminal. To this end, the controller 1001 feeds back the channel status report multiple times in a specific feedback window for any terminal, and does not feed back the channel status report in another specific feedback window.

The controller 1001 applies the generated feedback transmission information to the PDSCH channel generator 1006 and receives the resource information and modulation information allocated to the UEs from the scheduler 1000 and generates the PDSCH channel generator 1006 based on the scheduling information. . The multiplexer 1007 multiplexes the PDSCH symbols received from the PDSCH channel generator 1006 according to the resource allocation information received from the controller 1001. CRS is multiplexed in the PDCCH region, and CSI-RS and DM-RS are multiplexed in the PDSCH region. The reason is that 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 1001 controls the CSI-RS to multiplex on the PDSCH based on a predetermined CSI-RS transmission subframe number and transmission period.

11 shows a structure of a transceiver of a terminal according to the present invention. 11, the reception signal including the feedback control information is converted into a baseband signal through a reception process of the receiver 1100 and is converted into CSI-RS, DM-RS, CRS, PDCCH, and PDSCH signals through a demultiplexer 1101 Respectively.

At this time, the controller 1105 controls the demultiplexer 1101 based on the predetermined CSI-RS transmission subframe number and transmission period so that the CSI-RS can be distinguished. The channel estimator 1102 performs channel estimation using the CRS, and then inputs the estimated value to the decoder device 1103 of the PDCCH.

The PDCCH decoder decodes the PDCCH inputted from the demultiplexer by using the CRS-based estimation value received from the channel estimation unit 1102. [

The controller 1105 receives PDSCH allocation information and information for PDSCH demodulation and decoding from the PDCCH decoder apparatus 1103. Then, the controller 1105 performs channel estimation using the DM-RS in the channel estimation device 1102, and inputs the estimated value to the decoder device 1104 of the PDSCH.

 The PDSCH decoder decodes the PDSCH input from the demultiplexer using the DM-RS based estimation value received from the channel estimation unit 1102 and the PDSCH demodulation and decoding information received from the controller 1105. At this time, the controller 1105 controls the demultiplexer 1101 to identify the corresponding PDSCH based on the PDSCH allocation information received from the PDCCH decoder apparatus 1103. [ In this way, the UE can receive feedback control information (i.e., a period of a feedback transmission pattern, timing offsets and sizes of feedback windows, an activation and deactivation indicator of each feedback window, A cycle for multiple feedback transmission, and a feedback transmission pattern in each feedback window).

The controller 1105 controls the demultiplexer 1101 to distinguish the CSI-RS based on a predetermined CSI-RS transmission subframe number and transmission period, and applies the control information to the channel estimation apparatus 1102 to transmit the downlink channel state information . &Lt; / RTI &gt;

The downlink channel state information generated in the channel estimation apparatus 1102 is input to the controller 1105 and the controller 1105 transmits the channel state information to the PUCCH generator 1107 based on the feedback control information received from the base station. do. Then, the PUCCH generator 1107 generates a feedback signal based on this information and applies it to the multiplexer 1108. The controller 1105 controls the multiplexer 1108 to multiplex the reference signal generated from the uplink reference signal generator 1106 and the feedback signal generated from the PUCCH generator 1107. Then, the multiplexed signal is transmitted through a transmission process 1109.

More specifically, the controller 1105 according to the first embodiment may set the feedback control information in at least one feedback window periodically generated for the cell-characterized feedback transmission pattern length determined according to the feedback control information. And transmits the generated channel state information to the base station according to the feedback transmission pattern.

In addition, the controller 1105 according to the second embodiment may feed back the channel status report multiple times in a specific feedback window and not feed back the channel status report in another specific feedback window. To this end, the controller 1105 may receive a feedback window indicator that allows feedback from the base station multiple times and an indicator that instructs whether to activate or deactivate the feedback period and feedback window.

<Base Station>
1000: Scheduler 1001: Controller
1002: CRS generator 1003: PDCCH generator
1004: CSI-RS generator 1005: DM-RS generator
1006: PDSCH generator 1007: Multiplexer
1008: Transmitter
<Terminal>
1100: Receiver 1101: Demultiplexer
1102: channel estimation device 1103: PDCCH decoder
1104: PDSCH decoder 1105:
1106: Uplink RS generator
1107: PUCCH generator
1108: Multiplexer 1109: Transmitter

Claims (40)

A method for a mobile station to transmit channel state information in a mobile communication system,
Generating first channel state information based on a channel state information reference signal (CSI-RS) in a first subframe;
Transmitting the first channel state information in a second subframe by applying a first offset;
Generating second channel state information based on a CSI-RS in a third subframe; And
And transmitting the second channel state information in a fourth sub-frame by applying a second offset,
Wherein the interval between the first sub-frame and the second sub-frame is equal to or greater than a predetermined value, and the interval between the third sub-frame and the fourth sub-frame is equal to or greater than the predetermined value. Information transmission method. The method of claim 1, wherein the predetermined value is 4. The method of claim 1, wherein the CSI-RS in the first subframe and the CSI-RS in the third subframe are received from a base station according to a predetermined period. 2. The method of claim 1, wherein the transmission time point of the first channel state information and the second channel state information is set by upper signaling. A method for receiving channel state information in a mobile communication system,
Receiving first channel state information generated based on a channel state information reference signal (CSI-RS) in a first subframe in a second subframe determined based on a first offset, and
Receiving second channel state information generated based on a CSI-RS in a third subframe in a fourth subframe determined based on a second offset,
Wherein the interval between the first sub-frame and the second sub-frame is equal to or greater than a predetermined value, and the interval between the third sub-frame and the fourth sub-frame is equal to or greater than the predetermined value. Information receiving method. 6. The method of claim 5, wherein the predetermined value is four. 6. The method of claim 5, wherein the CSI-RS in the first subframe and the CSI-RS in the third subframe are transmitted from the base station to the terminal according to a predetermined period. The method of claim 5, wherein the transmission time point of the first channel state information and the second channel state information is set by upper signaling. A terminal for transmitting channel state information in a mobile communication system,
A transmission / reception unit for transmitting / receiving signals to / from a base station; And
The first channel state information is generated based on a channel state information reference signal (CSI-RS) in a first subframe, and the first channel state information is applied to a second subframe And generates the second channel state information based on the CSI-RS in the third subframe, applies the second offset to the second channel state information, and transmits the second channel state information through the transceiver in the fourth subframe And a control unit for controlling the transmission unit to transmit,
Wherein an interval between the first subframe and the second subframe is equal to or greater than a predetermined value and an interval between the third subframe and the fourth subframe is equal to or greater than the predetermined value. 10. The terminal of claim 9, wherein the predetermined value is four. 10. The terminal of claim 9, wherein the CSI-RS in the first subframe and the CSI-RS in the third subframe are received from the base station according to a predetermined period. 10. The terminal of claim 9, wherein the transmission time point of the first channel state information and the second channel state information is set by upper signaling. A base station for receiving channel state information in a mobile communication system,
A transmitting and receiving unit for transmitting and receiving signals to and from the terminal; And
The first channel state information generated based on a channel state information reference signal (CSI-RS) in the first subframe is received through the transceiver in the second subframe determined based on the first offset And a controller for controlling reception of the second channel state information based on the CSI-RS in the third subframe through the transceiver in the fourth subframe determined based on the second offset,
Wherein an interval between the first sub frame and the second sub frame is equal to or greater than a predetermined value and an interval between the third sub frame and the fourth sub frame is equal to or greater than the predetermined value. 14. The base station of claim 13, wherein the predetermined value is four. 14. The base station as claimed in claim 13, wherein the CSI-RS in the first subframe and the CSI-RS in the third subframe are transmitted from the base station to the terminal according to a predetermined period. 14. The base station of claim 13, wherein a transmission time point of the first channel state information and the second channel state information is set by upper signaling. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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