KR101192436B1 - Method and apparatus for selecting modulation and coding scheme, and method for transmitting feedback signal of terminal - Google Patents

Abstract

The apparatus for determining a modulation and coding scheme (MCS) allocates a plurality of feedback channels to a multicast group to which a plurality of terminals belong. In addition, a feedback signal is received from one terminal belonging to the multicast group through one feedback channel selected according to channel state information of each terminal among the plurality of feedback channels, and MCS is applied to the multicast data from the feedback signals received from the plurality of feedback channels. Determine.

Feedback Channel, Modulation and Coding Selection (MCS), Channel Status

Description

METHOD AND APPARATUS FOR SELECTING MODULATION AND CODING SCHEME, AND METHOD FOR TRANSMITTING FEEDBACK SIGNAL OF TERMINAL}

The present invention relates to a method and apparatus for determining a modulation and coding scheme, and a method for transmitting a feedback signal of a terminal.

The present invention is derived from a study conducted as part of the Ministry of Knowledge Economy's development of information and communication standards [Task Management Number: 2008-P1-01-06K51, Task Name: WiBro Evol, Research on Standardization Technology].

In order to increase transmission efficiency in a communication system, an adaptive modulation and coding (AMC) technique is applied.

AMC technology is a link adaptation technique that determines the most suitable transmission scheme among predefined Modulation and Coding Schemes (MCS) levels according to channel environment changes.

The terminal transmits channel quality indicator (CQI) to the base station using a feedback channel to deliver the quality of the channel to the base station, the base station selects a suitable MCS level according to the channel state information, according to the MSC level The data is modulated, coded and transmitted to the terminal.

In the multicast transmission scheme for transmitting data to a plurality of terminals in a cell, the MCS level should be determined according to channel state information of a terminal having a worst channel state among a plurality of terminals in a cell. In this case, when a feedback channel for transmitting channel state information is allocated to a plurality of terminals in a cell, the feedback channel is required in proportion to the number of terminals in the cell, thereby limiting uplink transmission capacity.

The present invention has been made in an effort to provide a method and apparatus for determining a modulation and coding scheme capable of determining a modulation and coding scheme while minimizing the use of a feedback channel, and a method for transmitting a feedback signal of a terminal.

According to an embodiment of the present invention, a method for determining a modulation and coding scheme (MCS) of a base station is provided. According to this method, allocating a plurality of feedback channels to a multicast group to which a plurality of terminals belong, one selected from each terminal belonging to the multicast group according to channel state information of each terminal among the plurality of feedback channels Receiving a feedback signal through a feedback channel, and determining an MCS to be applied to multicast data from the feedback signals received in the plurality of feedback channels.

According to another embodiment of the present invention, an apparatus for determining a modulation and coding scheme (MCS) is provided. The apparatus includes a signal detector and a modulation and coding decision unit. The signal detector detects a feedback signal transmitted through one feedback channel selected according to channel state information of each terminal among a plurality of feedback channels allocated to the multicast group from each terminal belonging to the multicast group. The modulation and coding determination unit determines an MCS to be applied to multicast data using the feedback signals detected in the plurality of feedback channels.

According to another embodiment of the present invention, a method for transmitting a feedback signal to a base station by a terminal is provided. The method includes receiving allocation information of a feedback channel from the base station, determining a decodable modulation and coding scheme (MCS), and selecting a feedback channel from among a plurality of feedback channels corresponding to the allocation information of the feedback channel. Selecting one feedback channel according to the MCS, and transmitting a feedback signal through the selected one feedback channel.

According to an embodiment of the present invention, resources used for a feedback channel for transmitting channel state information in uplink resources can be minimized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification and claims, when a section is referred to as "including " an element, it is understood that it does not exclude other elements, but may include other elements, unless specifically stated otherwise.

In this specification, a terminal includes a mobile station (MS), a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), a user equipment , An access terminal (UE), an access terminal (AT), and the like, and may include all or some functions of a terminal, a mobile terminal, a subscriber station, a mobile subscriber station, a user equipment,

In this specification, a base station (BS) includes an access point (AP), a radio access station (RAS), a node B, an evolved NodeB (eNodeB) A base station (BTS), a mobile multihop relay (MMR) -BS, or the like, and may perform all or a part of functions of an access point, a radio access station, a Node B, an eNodeB, a base transceiver station, .

Now, a method and apparatus for determining a modulation and coding scheme and a method for transmitting a feedback signal of a terminal according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram schematically showing a communication system to which the present invention is applied.

Referring to FIG. 1, the communication system includes a base station 10 and a plurality of terminals 20.

The base station 10 communicates with the plurality of terminals 20 belonging to the cell 10 and manages the plurality of terminals 20 belonging to the cell 1. In this case, the base station 10 may divide the plurality of terminals 20 into a multicast group and manage each terminal 20 for each multicast group.

The base station 10 includes a modulation and coding scheme determination device (not shown). An apparatus for determining a modulation and coding scheme (not shown) is a modulation and coding scheme (Modulation and Coding Schemes) according to channel state information of a terminal having a worst channel state among a plurality of terminals 20 belonging to the cell 1. MCS ", and modulates and codes multicast data according to the determined MCS to be transmitted to the plurality of terminals 20. At this time, the modulation and coding scheme determination device (not shown) receives a feedback signal from the terminal 20 to determine the MCS, two or three in the multicast group to receive the feedback signal from the terminal 20 Assign a feedback panel.

The terminal 20 receives multicast data from the base station 10. In addition, the terminal 20 selects one feedback channel from two or three feedback panels according to the channel state information, and transmits a feedback signal to the base station 10 through the selected feedback channel.

2 is a diagram illustrating an apparatus for determining modulation and coding schemes according to an embodiment of the present invention, and FIGS. 3 and 4 are diagrams illustrating feedback channels according to first and second embodiments of the present invention.

Referring to FIG. 2, the apparatus for determining modulation and coding scheme 100 includes a feedback channel allocator 110, a signal detector 120, a modulation and coding determiner 130, and a data transmitter 140.

Referring to FIG. 3, the feedback channel allocator 110 allocates three feedback channels FCH1-FCH3 to a multicast group. The feedback channel allocator 110 feeds back a feedback channel used by the base station 10 to transmit a feedback signal, which is determined to be decodeable even when the base station 10 transmits multicast data at a higher MCS level than the current MCS level. Channel FCH11 is set. In addition, the feedback channel allocator 110 selects a feedback channel that is used to transmit a feedback signal by a terminal determined to be impossible to decode when the current MCS level is appropriate and transmits multicast data at a higher MCS level. FCH12). In addition, the feedback channel allocator 110 cannot decode when multicast data is transmitted at the current MCS level, and the terminal determined to be decoded only by transmitting the multicast data at a lower MCS level provides a feedback signal. Set the feedback channel used for transmission to the feedback channel (FCH13).

Meanwhile, referring to FIG. 4, the feedback channel allocator 110 may allocate only two feedback channels FCH11 and FCH21 to the multicast group. In this case, the feedback channel allocator 110 uses the feedback channel FCH11 as a feedback channel used by the terminal determined to be decodeable even if the multicast data is transmitted at a higher MCS level than the current MCS level. Set to). In addition, the feedback channel allocator 110 transmits the feedback channel used for transmitting the feedback signal to the feedback channel (FCH12) by the terminal determined to be capable of decoding only by transmitting the multicast data at an MSC level lower than the current MCS level. Set it. As such, when only two feedback channels FCH11 and FCH21 are allocated, if it is determined that decoding is impossible when the current MCS level is appropriate and the multicast data is transmitted at a higher MCS level, the terminal 20 Do not send a feedback signal.

In addition, the feedback channel allocator 110 transmits information of two or three feedback channels FCH11 and FCH21 / FCH1-FCH3 allocated to the multicast group to the terminal 20 belonging to the multicast group.

Referring back to FIG. 2, the signal detector 120 detects signals in two or three feedback channels FCH11 and FCH21 / FCH1-FCH3 allocated to terminals belonging to a multicast group.

The modulation and coding selection unit 130 applies the MCS to the multicast data according to a signal detected by two or three feedback channels FCH11, FCH21 / FCH1-FCH3 allocated to the terminal 20 belonging to the multicast group. Determine.

The data transmitter 140 modulates and codes multicast data according to the determined MCS and transmits the multicast data to the terminal 20 belonging to the multicast group.

5 is a diagram illustrating a multicast data transmission method according to an embodiment of the present invention.

Referring to FIG. 5, the feedback channel allocator 110 of the apparatus for determining modulation and coding scheme 100 allocates two or three feedback channels FCH11, FCH21 / FCH1-FCH3 to a multicast group (S510). Then, the allocation information of the allocated two or three feedback channels (FCH11, FCH21 / FCH1-FCH3) is transmitted to the terminal 20 belonging to the multicast group through the downlink control channel (S520). At this time, the downlink control channel also includes the location and transmission format information of the radio resource to which the multicast data of the multicast group is to be transmitted.

The terminal 20 belonging to the multicast group receives the downlink control channel, and acquires the location and transmission format information of the radio resource to which the multicast data is to be transmitted and the allocation information of the feedback channel from the downlink control channel (S530).

Each terminal 20 in the multicast group estimates a channel state (S540), and determines a decodable MCS level from the estimated channel state (S550). In this case, the terminal 20 may estimate the channel state by transmitting and receiving a pilot signal or a preamble known to the base station 10 in advance. Alternatively, the terminal 20 may estimate the channel state. In this case, as a method of estimating a channel state, a method of measuring a carrier to interface ratio (CINR) may be used.

Meanwhile, when the terminal 20 belonging to the multicast group receives the multicast data, the terminal 20 belonging to the multicast group estimates the reception quality of the received multicast data, and from the estimated reception quality information, respectively. It is also possible to determine the decodable MCS level. In this case, as a method of estimating reception quality, a method of measuring signal to interference and noise ratio (SINR) may be used.

Thereafter, the terminal 20 belonging to the multicast group modulates a predetermined feedback signal through a feedback channel corresponding to the determined MSC level among the two or three feedback channels FCH11 and FCH21 / FCH1-FCH3 assigned, respectively. The transmission is transmitted to the coding method determination apparatus 100 (S560).

In detail, when the feedback channel allocator 110 allocates three feedback channels FCH1-FCH3 to the multicast group, the terminal 20 belonging to the multicast group transmits the MCS to a level higher than the current MCS level. If it is determined that decoding of the multicast data is possible, the feedback signal is transmitted using the feedback channel FCH1 among the three feedback channels FCH1-FCH3. In addition, when the terminal 20 belonging to the multicast group determines that the current MCS level is appropriate and decoding of multicast data transmitted to the MCS of a level higher than the current MSC level is impossible, three feedback channels FCH1 may be used. A feedback signal is transmitted using the feedback channel FCH2 among the -FCH3. However, if it is determined that the terminal 20 belonging to the multicast group is capable of decoding the multicast data transmitted to the MCS of a level lower than the current MCS level, the feedback channel FCH3 among the three feedback channels FCH1-FCH3 may be used. ) To transmit the feedback signal.

Meanwhile, when the feedback channel allocator 110 allocates two feedback channels FCH11 and FCH12 to the multicast group, the terminal 20 belonging to the multicast group is transmitted to an MCS of a higher level than the current MCS level. If it is determined that decoding of the multicast data is possible, the feedback signal is transmitted using the feedback channel FCH11 among the two feedback channels FCH11 and FCH12. When the terminal 20 belonging to the multicast group determines that decoding of multicast data transmitted to an MCS of a level lower than the current MCS level is possible, the feedback channel FCH21 among the two feedback channels FCH11 and FCH12 may be used. ) To transmit a predetermined signal. However, if it is determined that the current MCS level is appropriate and decoding of multicast data transmitted to the MCS of a level higher than the current MSC level is impossible, the terminal 20 belonging to the multicast group does not transmit a feedback signal. Do not.

The modulation and coding determination unit 130 of the modulation and coding scheme determination apparatus 100 may apply to the multicast data using the feedback signals detected in the feedback channels FCH11 and FCH21 / FCH1-FCH3 assigned to the multicast group. After determining the MSC (S570), the data transmission unit 140 of the modulation and coding scheme determination apparatus 100 modulates and codes the multicast data according to the determined MSC and transmits it to the terminal 20 belonging to the multicast group ( S580).

Then, the terminal 20 belonging to the multicast group receives the multicast data according to the corresponding transmission format from the corresponding resource (S590).

6 illustrates a method of determining a modulation and coding scheme according to an embodiment of the present invention.

Referring to FIG. 6, the signal detector 120 detects a feedback signal in feedback channels FCH11 and FCH21 / FCH1-FCH3 allocated to a multicast group (S610). In this case, the signal detection method may be an energy detection method or a method using a correlator.

The modulation and coding determination unit 130 determines the MSC to be applied to the multicast data according to the detected feedback signal (S620).

In detail, when the feedback channel allocator 110 allocates three feedback channels FCH1-FCH3 to the multicast group, the modulation and coding determination unit 130 detects the three feedback channels FCH1-FCH3. The MSC level to be applied to the multicast data is determined according to the feedback signal. MSC levels to be applied to the multicast data according to the feedback signals detected in the three feedback channels FCH1 to FCH3 may be determined as shown in Table 1 below. In Table 1, "0" means that there is no hidden feedback signal, and "1" means that there is a detected feedback signal.

As shown in Table 1, the modulation and coding determination unit 130 maintains the MCS level if there are no feedback signals detected in the three feedback channels FCH1-FCH3, and the feedback channel FCH3 among the three feedback channels FCH1-FCH3. If only a feedback signal is detected, the MSC level is lowered by at least one step. In addition, if a feedback signal is detected only in the feedback channel FCH2 among the three feedback channels FCH1-FCH3, the MCS level is maintained, and two feedback channels FCH2, FCH3 / FCH1, and FCH3 among the three feedback channels FCH1-FCH3 are maintained. If a feedback signal is detected, the MSC level is lowered by at least one step since the feedback signal should be adjusted to the channel state information of the worst terminal. Similarly, even if a feedback signal is detected in all three feedback channels FCH1-FCH3, the MSC level is lowered by at least one step because it should be adjusted to the channel state information of the worst terminal. If feedback signals are detected in two feedback channels FCH1 and FCH2 among the three feedback channels FCH1-FCH3, the MCS level is maintained.

On the other hand, when the feedback channel allocator 110 allocates two feedback channels FCH11-FCH12 to the multicast group, the modulation and coding determiner 130 receives feedback detected by the two feedback channels FCH11-FCH12. The MSC level to be applied to the multicast data is determined according to the signal. MSC levels to be applied to the multicast data according to the feedback signals detected in the two feedback channels FCH11 to FCH12 may be determined as shown in Table 2. In Table 2, "0" means that no feedback signal is detected, and "1" means that there is a feedback signal detected.

As shown in Table 2, the base station 10 maintains the MCS level if there are no feedback signals detected in the two feedback channels FCH11-FCH12, and the feedback signal only in the feedback channel FCH12 of the two feedback channels FCH11-FCH12. Is detected, the MSC level is lowered by at least one step. If the feedback signal is detected only in the feedback channel FCH11 of the two feedback channels FCH11-FCH12, the MCS level is maintained or the MCS level is increased by at least one step, and the feedback signal is detected in both feedback channels FCH11-FCH12. If necessary, the MSC level is lowered by at least one step because it must be adjusted to the channel state information of the worst terminal.

After determining the MSC level to be applied to the multicast data, the data transmitter 140 modulates and codes the multicast data according to the determined MSC level and transmits the multicast data to the terminal 20 belonging to the multicast group (S630-S640). .

In this case, since only two or three feedback channels may be allocated to the UE belonging to the multicast group, resources used for the feedback channel in the uplink resource can be minimized.

An embodiment of the present invention is not implemented only through the above-described apparatus and / or method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Such an implementation can be easily implemented by those skilled in the art to which the present invention pertains based on the description of the above-described embodiments.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

1 is a view schematically showing a communication system to which the present invention is applied;

2 is a diagram illustrating an apparatus for determining a modulation and coding scheme according to an embodiment of the present invention;

3 and 4 illustrate feedback channels according to first and second embodiments of the present invention.

5 is a view showing a multicast data transmission method according to an embodiment of the present invention,

6 illustrates a method of determining a modulation and coding scheme according to an embodiment of the present invention.

Claims (20)

In the Modulation and Coding Schemes (MCS) determination method of the base station, Allocating a plurality of feedback channels to a multicast group to which a plurality of terminals belong; Receiving a feedback signal from one terminal belonging to the multicast group through one feedback channel selected according to channel state information of each terminal among the plurality of feedback channels; and Determining an MCS to be applied to multicast data from feedback signals received in the plurality of feedback channels; Modulation and coding scheme determination method comprising a. The method of claim 1, Modulating and coding the multicast data according to the determined MCS and transmitting the multicast data to the plurality of terminals; Modulation and coding scheme determination method further comprising. The method of claim 1, Wherein the number of the plurality of feedback channels is two or three. The method of claim 1, The plurality of feedback channels including first and second feedback channels, The first feedback channel is a feedback channel used for transmitting the feedback signal by a terminal capable of decoding multicast data transmitted at an MCS level higher than a set MCS level among the plurality of terminals. The second feedback channel is a feedback channel used for transmitting the feedback signal by a terminal capable of decoding multicast data transmitted to an MCS of a lower level than the set MCS level among the plurality of terminals. Way. 5. The method of claim 4, The determining step, Lowering an MCS level when the feedback signal is detected in the feedback channel; Maintaining or raising an MCS level if the feedback signal is detected only in the first feedback channel; and  If the feedback signal is not detected in the first and second feedback channels, maintaining an MCS level. 5. The method of claim 4, The plurality of feedback channels further includes a third feedback channel, The third feedback channel is a modulation and coding scheme determination method, which is a feedback channel used for transmitting the feedback signal by a terminal which cannot decode multicast data transmitted to an MCS level higher than a set MCS level among the plurality of terminals. . The method of claim 1, Transmitting allocation information of the plurality of feedback channels to the plurality of terminals. Modulation and coding scheme determination method further comprising. The method of claim 7, wherein The transmitting step, And a method for determining a modulation and coding scheme including allocation information of the plurality of feedback channels in a downlink control channel to the plurality of terminals. In the Modulation and Coding Schemes (MCS) determination device, A signal detector for detecting a feedback signal transmitted through one feedback channel selected according to channel state information of each terminal among a plurality of feedback channels allocated to the multicast group from each terminal belonging to a multicast group, and Modulation and coding determination unit for determining the MCS to be applied to the multicast data using the feedback signal detected in the plurality of feedback channels Modulation and coding scheme determination apparatus comprising a. 10. The method of claim 9, A data transmitter for modulating and coding the multicast data according to the determined MCS to transmit to the plurality of terminals Modulation and coding scheme determination device further comprising. 10. The method of claim 9, A feedback channel allocator configured to allocate the plurality of feedback channels to a multicast group to which the plurality of terminals belong, and to transmit allocation information of the plurality of feedback channels to the plurality of terminals. Modulation and coding scheme determination device further comprising. 10. The method of claim 9, And a number of the plurality of feedback channels is two or three. 10. The method of claim 9, The plurality of feedback channels includes first and second feedback channels, The first feedback channel is a feedback channel used for transmitting the feedback signal by a terminal capable of decoding multicast data transmitted at an MCS level higher than a set MCS level among the plurality of terminals. The second feedback channel is a feedback channel used for transmitting the feedback signal by a terminal capable of decoding multicast data transmitted to an MCS of a lower level than the set MCS level among the plurality of terminals. Device. 14. The method of claim 13, The modulation and coding determination unit, When the feedback signal is detected in the feedback channel, lower the MCS level, If the feedback signal is detected only in the first feedback channel, maintain or increase an MCS level,  And the MCS level is maintained when the feedback signal is not detected in the first and second feedback channels. 14. The method of claim 13, The plurality of feedback channels further includes a third feedback channel, The third feedback channel is a feedback channel used for transmitting the feedback signal by a terminal that cannot decode multicast data transmitted to an MCS level higher than a set MCS level among the plurality of terminals. Device. In the method for the terminal to transmit a feedback signal to the base station, Receiving allocation information of a feedback channel from the base station, Determining a decodable modulation and coding scheme (MCS), Selecting one feedback channel according to the MCS from among a plurality of feedback channels corresponding to the allocation information of the feedback channel, and Transmitting a feedback signal through the selected one feedback channel Feedback signal transmission method comprising a. 17. The method of claim 16, And the number of the plurality of feedback channels is two or three. 17. The method of claim 16, The plurality of feedback channels includes first and second feedback channels, If the terminal is capable of decoding the multicast data transmitted to the MCS level higher than the set MCS level, selects the first feedback channel, And selecting the second feedback channel when decoding of multicast data transmitted to an MCS of a level lower than the set MCS level is possible. 19. The method of claim 18, The plurality of feedback channels further includes a third feedback channel, And the terminal selects the third feedback channel when decoding of multicast data transmitted at an MCS level higher than the set MCS level is impossible. 19. The method of claim 18, And when the decoding of the multicast data transmitted to the MCS level higher than the set MCS level is impossible, the terminal does not transmit the feedback signal.

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