KR20080104755A - Method for transmitting control signals based on grid scheme - Google Patents

Abstract

A method for transmitting a control signal based on a grid scheme is provided to maximize the efficiency of a downlink channel by efficiently indicating the channel state of the downlink channel and minimizing the size of channel quality information. A method for transmitting a control signal based on a grid scheme comprises the steps of: transmitting first type information which indicates channel quality information every cycle(S1201); obtaining grid index information which is formed in the direction of a frequency and channel quality vale(S1202); and selectively transmitting second type control information(S1204).

Description

Method for transmitting control information based on grid method {Method For Transmitting Control Signals Based On Grid Scheme}

1 to 3 show timings of transmitting first type control information.

4 to 6 show timings of transmitting second type control information.

FIG. 7 is a diagram for explaining a method of transmitting first type control information according to a Best-M scheme; FIG.

8 and 9 illustrate an example of a method of transmitting first type control information and second type control information in a Best-M scheme.

10 and 11 are diagrams for explaining a method for transmitting second type control information on a grid basis according to one preferred embodiment of the present invention.

FIG. 12 is a diagram for explaining a method of transmitting second type control information according to another embodiment of the present invention; FIG.

13 is a flowchart illustrating a method of transmitting control information according to an embodiment of the present invention.

In the following description, a grid-based control information transmission method is disclosed.

To this end, a method of reporting general channel quality information (CQI) is described first.

In order to maximize the efficiency of data transmission in a multicarrier system, link adaptation is used. In other words, by measuring the transmittable capacity of the link, it is sending the maximum information that can be transmitted on the link. In order to adapt such a link, channel quality information (CQI) of the link is required. This channel quality information is needed in the side of scheduling data transmission through the link. Therefore, when transmitting and receiving data between a base station and a user equipment (hereinafter referred to as "UE"), if the base station controls and schedules all data transmission and reception, channel quality information corresponding to downlink should be fed back by the UE. do.

On the other hand, as the amount of information of the channel quality information in the multi-carrier system is increased, the downlink transmission efficiency is maximized, but the amount of information to be transmitted in the uplink is increased, the efficiency of the uplink is reduced. Therefore, a method of maximizing downlink transmission efficiency while reducing overhead of uplink by transmitting channel quality information as small as possible is required.

In order to solve the above problems, an object of the present invention is to provide a method for maximizing downlink channel efficiency by efficiently indicating downlink channel conditions while minimizing the amount of channel quality information.

According to an aspect of the present invention, there is provided a method of transmitting control information, the method comprising: transmitting first type control information indicating channel quality information every first period, and frequency based on the first type control information; And selectively transmitting second type control information comprising grid index information formed in the direction and channel quality value directions.

In this case, the grid index information may indicate at least one of a change in channel quality information value and a change in report target frequency band information value at the time of transmitting the first type control information and the time of transmitting the second type control information. When the second type control information transmission time is predetermined, there is no change in the channel quality information value and the report target frequency band information value at the time of transmitting the first type control information and the time of transmitting the second type control information. In this case, the second type control information may not be transmitted at the time point of transmitting the second type control information.

The number of grid indices may be set to a power of two, and preferably, the number of grid indices except for a grid corresponding to the first type control information may be set to a power of two.

Further, when the number of grid indexes is not the number of powers of two, additional control information of a number corresponding to the difference between the minimum number or more of the number of grid indices and the number of grid indexes among the number of powers of two is provided. The newly indexed index information may be transmitted by newly indexing a combination of grid index information at two or more transmission time points for transmitting the second type control information.

In addition, the size of the grid is preferably set in proportion to the change rate of the channel, wherein the first type control information is via a first layer control signal, and the second type control information is a higher layer control signal of a second layer or more. It may be desirable to transmit via.

In addition, the second type control information may be transmitted in a second period smaller than the first period, wherein the second type control information is between the first period time, at the request of the base station, or according to the determination of the user equipment. It may be set to be transmitted aperiodically.

On the other hand, the control information transmission method according to another aspect of the present invention comprises the steps of transmitting the first type control information indicating the channel quality information every first period, and between the first period time, at the request of the base station or the user Transmitting second type control information including a change value of the first type control information aperiodically in accordance with the determination of the device.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details.

On the other hand, in some cases, well-known structures and devices are omitted in order to avoid obscuring the concepts of the present invention, or shown in block diagram form centering on the core functions of each structure and device. In addition, the same components will be described with the same reference numerals throughout the present specification.

The present invention relates to a method for transmitting control information efficiently indicating a downlink channel condition while minimizing the amount of channel quality information as described above. To this end, the following description will be based on a method of feeding back the downlink channel quality information as described above in the uplink, but on the contrary, the method for feeding back the channel quality information for the uplink in the downlink may also be applied.

In one embodiment of the present invention, in order to reduce the amount of channel quality information to be fed back, it is proposed to transmit feedback information divided into first type control information and second type control information.

Specifically, the first type control information may include general channel quality information as information for estimating a channel quality state of the UE even when the base station receives only the information. On the other hand, the second type control information is information that supplements the above-described first type control information, but the channel quality information of the UE cannot be estimated by the base station by itself, but the channel type information of the UE is used together with the first type control information. Information may be estimated. For example, the first type control information represents general channel quality information, and the second type control information may be differential value information from the channel quality information included in the first type control information at the time of transmitting the same. have.

In general, the second type control information may be represented with a smaller number of bits than the first type control information, which enables a more accurate representation of the downlink channel situation with less feedback information.

The above-described first type control information may be fed back to the base station through physical layer signaling and may be fed back through higher layer signaling, for example, L1 / L2 signaling, depending on the configuration. In this case, the period in which the first type control information is fed back may be determined by the base station and informed to the UE, or may be determined in advance by the operator and set to a specific value.

1 to 3 are diagrams showing timings of transmitting first type control information.

Specifically, FIG. 1 illustrates a manner in which the above-described first type control information is fed back with a specific period. However, unlike the first type, the first type control information may be fed back with a plurality of periods, and FIG. 2 illustrates a manner in which the first type control information is fed back with a plurality of periods. In addition, the first type control information may additionally be fed back aperiodic channel quality information according to a request of the UE or a situation that the base station thinks that it is necessary, and FIG. 3 is a non-periodic first type including such channel quality information. A method of additionally transmitting control information is shown.

On the other hand, as described above, the second type control information includes supplementary information about the channel quality information after the aforementioned first type control information is fed back. The timing of transmitting such second type control information will be described below.

4 to 6 are diagrams showing timings of transmitting second type control information.

As shown in FIG. 4, the second type control information may also be fed back to the base station with a constant period like the first type control information. In this case, the period for transmitting the second type control information is preferably shorter than the period for transmitting the first type control information, and as illustrated in FIG. 4, a plurality of second periods between transmission periods of the first type control information. Type control information may be set to be transmitted. In addition, as shown in FIG. 5, the second type control information may be transmitted between cycles in which the first type control information is transmitted with a plurality of cycles.

In addition, in one embodiment of the present invention, as shown in FIG. 6, the second type control information may be transmitted aperiodically as required by the UE or at the request of the base station between transmission periods of the first type control information. . Accordingly, when the UE experiences a sudden channel change or a certain situation occurs, the UE may feedback the second type control information having a smaller amount of information regardless of the period at the corresponding time point to more accurately inform the channel status.

Hereinafter, a method of indicating channel quality through the above-described first type control information and second type control information will be described in more detail.

The most basic method of transmitting the channel quality information is a method of measuring channel quality information for downlink for each channel quality unit frequency over the entire frequency band. However, this method increases the amount of resources required to report channel quality information. Therefore, one embodiment of the present invention proposes to use the "Best-M method" as one method of reducing channel quality information transmitted in the uplink.

The general Best-M method is a method of feeding back M channel quality information values of all channel quality information measured by a UE and a position value of a band in which the M channel quality information values of an entire bandwidth are located.

In one embodiment of the present invention, it is proposed to transmit channel quality information according to the first type control information among the above-described first type control information and second type control information in Best-M format. Accordingly, the first type control information includes (1) channel quality information in the best M bands, (2) location information (of frequency bands) corresponding to (1), and (3) bands other than the best M bands. The average value of the channel quality information for may be included. In addition, the first type control information may include other modified forms of information in addition to the above three pieces of information ((1), (2), and (3)), whereas only the information of a part of the three types is included. You may.

FIG. 7 is a diagram for describing a method of transmitting first type control information according to a Best-M scheme.

Specifically, FIG. 7 illustrates a case where M is 3 in the above-described Best-M scheme. Accordingly, the three highest channel quality information and position information of the frequency bands (i.e., position information of bands 1, 3 and 6, referred to as 1, 2 and 3, and channel quality information in each band), and the remaining frequency bands The form of feeding back the average value of the channel quality information of (ie, the channel quality information of the bands referred to as 4) is shown.

Meanwhile, the second type control information is part of the first type control information or information complementing the first type control information.

8 and 9 illustrate an example of a method of transmitting first type control information and second type control information in a Best-M scheme.

Specifically, FIG. 8 illustrates first type control of location information and channel quality information of three bands (ie, bands 1, 3, and 6) having the highest channel quality values among all frequency bands at time point 0 (t = 0). An example of transmitting as information is shown. In addition, FIG. 9 calculates a change in channel quality information generated between a time point when the first type control information is transmitted (that is, t = 0) and a time point when the second type control information is transmitted (that is, t = 1). An example of transmission by expressing the second type control information in an appropriate form is shown. Specifically, FIG. 9 illustrates an example of feeding back channel quality change amounts in bands 1, 3, and 6 reported in FIG. 8.

However, the change amount included in the second type control information may include not only the change amount of the channel quality value but also the change amount of position information of the best channel band as described above. As such, the most general method of representing the change of the channel quality information value and the band position information value may be a method of individually displaying the change value information.

For example, the quality of the selected channel during the transmission of the first type control information may be increased, decreased, or maintained as time passes. In one embodiment of the present invention, this may be represented by a predetermined bit. In other words, if the change amount is expressed in 1 bit, the increase / decrease width can be designated in advance to indicate the increase / decrease.If there is no increase or decrease, the channel quality information is maintained by transmitting nothing at the timing of transmitting the change amount. Can convey meaning.

At this time, the step size can be optimally designed and operated according to the channel characteristics. The change amount can be defined as 1 bit or more, and in this case, the entire range and the increase / decrease range can be set and operated according to the system.

In general, the elements included in the amount of change are based on the principle of minimizing the amount of information and maximizing accuracy. Accordingly, in one preferred embodiment of the present invention, unlike the above-described embodiment, the channel quality information value and the band position information value can be efficiently represented with a small amount of information. A method of setting a grid and feeding back this grid index information as second type control information is proposed.

10 and 11 are diagrams for describing a method of transmitting second type control information on a grid basis according to an exemplary embodiment of the present invention.

Specifically, FIG. 10 illustrates a case in which only a value of channel quality information is changed without changing a position of a band representing the best channel quality in the Best-M scheme, and FIG. 11 illustrates a band representing the best channel quality. And a case where all of the changes in the channel quality information values are shown.

That is, in FIG. 10, first type control information is transmitted at t = 0, and the reported frequency band and channel quality information values correspond to region 3. FIG. Thereafter, the position of the band showing the best channel quality did not change at the time of transmitting the second type control information (t = 1), but the channel quality value changed and the corresponding area corresponds to the area 2 on the grid. , The index information for the area 2 can be transmitted as the second type control information.

Meanwhile, in FIG. 11, first type control information is also transmitted at t = 0, and the reported frequency band and channel quality information values correspond to region 5. FIG. Subsequently, when the band position and the channel quality information value indicating the best channel quality are changed at the time of transmitting the second type control information (t = 1) to correspond to the area 3 on the grid, the index information for the area 3 is converted to the second. It can be transmitted as type control information.

FIG. 11 illustrates an example in which a grid is formed so that a total of nine kinds of changes (including a reference) can be expressed around a reference position (area 5). However, in one embodiment of the present invention, FIG. The size of the grid may vary. For example, when the movement speed of the UE is fast, the channel quality can be largely changed accordingly, so that the grid can be set large. In addition, the number of indexes of the grid shown in FIGS. 10 and 11 (preferably, the number of grid indexes excluding the reference region) may correspond to a power of two, which may be preferable to express it in bit units.

In one embodiment of the present invention as described above, a predetermined time is determined based on the channel quality information value calculated at the time of transmitting the first type control information and the position of the region (region 5 in FIG. 11) according to the position. When there is a change in the channel quality information and the position information at the last time point, that is, at the time of transmitting the second type control information, as shown in FIG. It can be transmitted as the second type control information indicating the change. Further, in a preferred embodiment of the present invention, the bit value (for example, 000 to 111) as the second type control information transmitted at each time point of transmitting the second type control information is based on the information most recently fed back. (I.e., area 5) to show relative changes.

When nine grids are formed around the area 5 as shown in the example of FIG. 11, the change amount information indicated by the grid index information transmitted at the time of transmitting the second type control information may be represented as follows. Index information representing each grid area may be represented through bit information in parentheses.

Area 1 (000): decreases the channel quality information measurement band position value by 1 step, and increases the channel quality information value by 1 step.

Area 2 (001): Maintain channel quality measurement band position value, increase channel quality information value by 1 step.

Region 3 (010): Increases the channel quality information measurement band position value by 1 step and increases the channel quality information value by 1 step.

Area 4 (011): decreases the channel quality information measurement band position value by 1 step, and maintains the channel quality information value.

Area 5 (Not Transmitted): Maintains channel quality measurement band position value and maintains channel quality information value.

Region 6 (100): Increases the channel quality information measurement band position value by 1 step and maintains the channel quality information value.

Region 7 (101): decreases the channel quality information measurement band position value by 1 step, and reduces the channel quality information value by 1 step.

Region 8 (110): Maintain channel quality measurement band position value, decrease channel quality information value 1 step.

Region 9 (111): Increases the channel quality information measurement band position value by 1 step and decreases the channel quality information value by 1 step.

In such an embodiment, eight pieces of state information can be represented as three bits of second type control information (i.e., eight types except area 5), and area 5 is state information for maintaining a current position and channel quality information. The state can be expressed by not transmitting the second type control information at a timing (predetermined predetermined timing) at which the second type control information should be transmitted. However, in another embodiment of the present invention, index information of a predetermined bit may be configured to include the case where the channel quality information measurement band position value and the channel quality information value do not change.

Further, in another embodiment of the present invention, the number of grid indices for representing the second type control information does not correspond to a power of two, and the grid for representing the number corresponding to a power of two and the channel quality information. We propose a method of transmitting control information (eg, ACK / NACK) other than channel quality information by using an index corresponding to a difference in the number of s.

12 is a diagram for explaining a method of transmitting second type control information according to another embodiment of the present invention.

As shown in FIG. 12, in an embodiment of the present invention, a specific grid area may be set not to be used in advance between the base station and the UE as necessary, and the grid area indicated by X in FIG. 12 is not used between the base station and the UE. Indicates an area set not to. As such, three bits of control information are required to represent the remaining five grid areas except for the specific grid area. At this time, one embodiment of the present invention represents any other control information, such as ACK / NACK, three of the eight cases that can be represented using three bits of control information except for five cases for indicating the channel quality information. Suggest to use. Such a method may be used, for example, in a manner in which one of the grid regions indicated by X in FIG. 12 represents an ACK, and the other region represents a NACK.

Further, in another embodiment of the present invention, the second type of control information is not represented by using a grid index set separately at every transmission time, but a combination of grid index information to be transmitted at two or more transmission time points. We propose a method for reducing the number of bits.

For example, when five grid indices of 1 to 5 are set to represent channel quality information, as shown in FIG. 12, three bits of control information are transmitted at each timing for transmitting the second type control information. In the case of two transmissions, a total of 6 bits of information are transmitted. However, according to an exemplary embodiment of the present invention, a scheme of newly indexing a combination of grid indices that may occur at two timings according to the five cases described above and suggesting a method of expressing them using a total of five bits is provided. That is, for the indices 1 to 5 at each timing, 1-1, 1-2, 1-3, 1-4, 1-5, 2-1, 2-2, ..., 5-5 A total of 25 combinations can be newly indexed using 5 bits, thereby further reducing the amount of information to be transmitted. In addition, in the present embodiment, 25 cases for indicating channel quality information among the 32 cases that can also be represented through 5 bits can be used for transmission of any other control information other than channel quality information.

The base station receiving the second type control information may reconstruct the entire channel quality information based on the received channel quality information and the variation information.

Meanwhile, in the above-described embodiments, the channel quality information included in the first type control information may be transmitted through physical layer (L1) control signaling or transmitted through higher layer (for example, L1 / L2) control signaling. May be When the first type control information is transmitted through the L1 control signaling in the foregoing case, two types of control signaling formats are required for transmission of control information in the physical layer. Accordingly, in a preferred embodiment of the present invention, it is proposed to transmit first type control information having a relatively large amount of information through L1 / L2 control signaling and to transmit second type control information having a relatively small amount of information through L1 control signaling. . When transmitting in this manner, there may be an advantage that a format for transmitting two types of control information of the first type and the second type is not required in the physical layer.

The control information transmission method according to the embodiments of the present invention as described above are collectively described as follows.

13 is a flowchart illustrating a method of transmitting control information according to an embodiment of the present invention.

According to one embodiment of the present invention as shown in FIG. 13, in step S1201, first type control information capable of independently indicating channel quality information is transmitted. In this case, the transmitted control information may preferably include channel quality information according to the Best-M method. Accordingly, M band position information representing the best channel quality and channel quality information values in the corresponding band may be transmitted. have.

Thereafter, in step S1202, after a predetermined time has elapsed, grid index information for indicating a change in the channel quality information value and the band in which the channel quality information is measured is obtained. The size of the grid may be set in proportion to the mobility of the UE, and information about the grid may be predetermined between the base station and the UE or determined by the base station and delivered to each UE through higher layer signaling. According to the grid information thus obtained, in step S1203 it is determined whether there is a change in the channel quality information value and the position value of the band for measuring it. If there is a change, the grid index information indicating the change information can be transmitted as the second type control information through step S1204. On the other hand, if there is no change in the channel quality information value and the band position information measured as a result of the determination in step S1203, the second type control information is not transmitted at a predetermined time point to proceed to step S1205 to transmit the second type control information. You may not. Thereafter, the flow advances to step S1202 to acquire new grid index information for transmitting subsequent second type control information.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable any person skilled in the art to make and practice the invention. Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can.

For example, the description of the above embodiments can be applied to any system in which the UE feeds back channel quality information, such as the 3GPP LTE system as well as the IEEE 802 series system.

Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

According to the above-described embodiments of the present invention as described above, it is possible to maximize the downlink channel efficiency by efficiently indicating the downlink channel status while minimizing the amount of channel quality information, and not only the channel quality information value but also the corresponding channel. The system efficiency can be improved by accurately transmitting the position information of the frequency band corresponding to the quality information value.

Claims (12)

Transmitting first type control information indicating channel quality information every first period; And And selectively transmitting second type control information including grid index information formed in a frequency direction and a channel quality value direction centering on the first type control information. The method of claim 1, The grid index information indicates any one or more of a change in channel quality information value and a change in report target frequency band information value at the time of transmitting the first type control information and the time of transmitting the second type control information. . The method of claim 2, A time point for transmitting the second type control information is predetermined. When there is no change in the channel quality information value and the report target frequency band information value at the time of transmitting the first type control information and the time of transmitting the second type control information, the second at the time of transmitting the second type control information. A method for transmitting control information that does not transmit type control information. The method of claim 1, And the number of grid indices is set to a power of two. The method of claim 3, wherein And the number of grid indices except the grid corresponding to the first type control information is set to a power of two. The method of claim 1, If the number of grid indices is not a power of two, And transmitting additional control information corresponding to a difference between the minimum number of the grid index and the number of grid indexes among the number of powers of two and the number of grid indexes. The method of claim 1, And newly indexing a combination of grid index information at two or more transmission time points for transmitting the second type control information, and transmitting the newly indexed index information. The method of claim 1, And the size of the grid is set in proportion to the rate of change of the channel. The method of claim 1, The first type control information is transmitted through a first layer control signal. And transmitting the second type control information through a higher layer control signal of a second layer or more. The method of claim 1, And transmitting the second type control information in a second period less than the first period. The method of claim 1, And the second type control information is transmitted aperiodically between the first cycle time, at the request of the base station, or at the discretion of the user equipment. Transmitting first type control information indicating channel quality information every first period; And Transmitting, between the first cycle time, a second type control information including a change value of the first type control information aperiodically at the request of a base station or according to a determination of a user equipment. How to send information.

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