KR20080112071A - Methods for representing and generating control signal - Google Patents

Abstract

A control information expression and a production method for reducing signaling overhead are provided to maintain the flexibility of data transmission and minimize overhead of control information for confirming a reception side about a transmission method used for data transmission of the reception side. A whole combination is generated in consideration of each combination of more than 2 control information(S701). A plurality of candidate sets is generated by selecting a combination corresponding to the power number of the maximum 2 less than the number of whole combination among the whole combinations(S702). Control information is expressed by using a specific combination selected between a plurality of candidate sets(S703).

Description

Method for Representing and Generating Control Information

The present invention relates to a signaling method for data transmission in a mobile communication system. Specifically, a method of expressing control information for improving resource efficiency by reducing signaling overhead of data transmitted during data transmission in a mobile communication system and control information using the same It is about how to create.

The method of transmitting data in the wireless communication system may vary, and accordingly, it is preferable that the transmitting side transmitting the data transmits the control information on the transmission method of the corresponding data to the receiving side. In particular, in a MIMO system in which a transmitting side transmits a transmission signal using a plurality of antennas, there may be more various transmission schemes. Accordingly, the type and / or transfer of control information to be transmitted to a receiving side when the transmitting side transmits data. Can increase. Hereinafter, the signal transmission method of the above-described MIMO system will be described in general.

MIMO (Multi Input Multi Output) is a technique of increasing the number of antennas on the transmitting side and the receiving side to two or more, so that the transmitting side transmits data through multiple paths and the receiving side detects signals received on each path. The MIMO scheme can be classified into various methods such as spatial diversity, transmission diversity, beamforming, spatial multiplexing of a single user, and spatial multiplexing of a multiuser.

First, the above-described spatial diversity is a technique for transmitting the same data through a plurality of antennas. According to the spatial diversity scheme as described above, even when the CQI feedback from the receiving end is low in reliability due to fading, stable operation can be performed. In addition, such a spatial diversity technique is useful as a technique for coping with fading using diversity without waiting for a better channel condition when it is necessary to service a delay-sensitive type of traffic. In addition, the above-described transmission diversity is a representative technique of the MIMO communication method, and may be used when the transmitting side has a plurality of antennas and the channel state is not known.

In addition, the above-described beamforming is a technique used to increase a signal to interference plus noise ratio (SINR) of a signal by applying weights according to channel conditions in multiple antennas. In the case of the transmission beamforming, it is difficult to know the channel state, so a separate feedback is required, and how to efficiently support it is an important element of the system design.

Meanwhile, the above-described Spatial Multiplexing (SM) scheme for single users and multiple users will be briefly described with reference to the accompanying drawings.

FIG. 1 is a diagram illustrating the concept of a spatial multiplexing and spatial divisional multiple access scheme used in a MIMO communication system.

First, spatial multiplexing for a single user is referred to as SM or SU-MIMO (Single User MIMO) and transmits signals using a plurality of antennas of a single user in a manner as shown on the left side of FIG. The capacity increases in proportion to the number of antennas. On the other hand, spatial multiplexing for multiple users is called SDMA or MU-MIMO (Multi-User MIMO), as shown in the right side of FIG.

The above-described MU-MIMO and SU-MIMO may use a closed loop transmission scheme in which a channel side knows channel information. The closed loop transmission scheme is a technique in which a transmitter receives feedback of channel information estimated by a receiver and transmits data using the information. The transmitter uses information of a channel fed back from the receiver, and thus the capacity and average error rate of the system. Can improve. In addition, according to the characteristics of the channel information received from the receiving side, the transmitting side can be largely divided into a full channel feedback scheme and a limited channel feedback scheme, and various transmission techniques can be applied from the channel information.

Hereinafter, an example of downlink in which a transmitting side is a base station, a receiving side is a terminal, a user equipment (UE), or simply a user will be described.

In the case of MU-MIMO, since the transmitting side (base station) transmits signals to several receiving terminals (UE) at the same time, the UE receives signals of another UE besides a desired signal through interference. Since the technique for suppressing such interference is difficult in terms of complexity and cost for use in the receiver of the UE, it is desirable to alleviate the interference by intelligently designing a transmission signal at the base station transmitter. If the base station knows the channel information in advance, the simplest way to handle the inter-UE interference is a zero-forcing or block diagonalization technique that nulls all interference signals. There is a method of precoding a transmission signal with pseudo inverse of. However, there is a constraint that the number of base station transmit antennas must be larger than the total number of data streams of users in order for the pseudo inversion of the channel to always exist, and when the users are in close proximity (ill-conditioned channel), power is consumed to null these interferences. A power indfficiency problem occurs, leading to performance degradation.

Recently, the DPC (Dirty Paper Coding) method has attracted attention as a method for maximizing the channel capacity in the MU-MIMO environment. Looking at the concept of DPC, if one transmitting end knows all the user's information and also the channel information, other user data, which is a component that interferes with each user, is removed in consideration of the channel in advance. From the user's point of view, the data can be transmitted so as not to feel other user interference. Using this DPC method, since no power is consumed to remove the interference, the channel capacity is the same as in an interference-free AWGN channel. Recently, a method of using DPC together with a generalized decision feedback equalizer (GDFE) structure has been proposed, but there are difficulties in realizing it, and researches to replace it are being conducted.

Most MU-MIMO methods such as zero forcing and DPC discussed above require the assumption that the transmitter knows the channel information. However, since the transmitting end needs to feed back information on all channels in order to have all the information on the instantaneous channel, such information occupies a large part of the resources transmitted from the receiving end to the transmitting end. In addition, in a real system, performance degradation may occur due to a time delay and a transmission error that occur when a receiver feeds back a channel estimation error and estimated channel information to a transmitter. Therefore, instead of instantaneous channel information, there is a limited channel information feedback method that feeds back only necessary parameters according to statistical characteristics or transmission techniques of the channel. Examples of such limited channel information feedback methods include Per User Unitary and Rate Control (PU2RC), Precoded Per User Rate Control (P-PURC), Per User and Stream Rate Control (S-PUSRC), and MIMO-SDMA.

In the following description, the "control information" indicates as a signal the transmission method used for data transmission among the various transmission methods as described above, so that the receiving end (for example, the UE) transmits to the transmitting end (for example, It refers to information that can detect its own data transmitted from the base station) without error. Such control information may be transmitted simultaneously with the data or may be transmitted in advance.

Control information transmitted according to each of the various MIMO transmission schemes described above will also vary. For example, when using the full channel feedback scheme in the above-described MU-MIMO, only the precoding matrix assigned to the UE is known from the control information of each UE due to the characteristics of the scheme, but the limited channel feedback scheme is used. The MIMO scheme is a control that informs each UE which of the streams (that is, the coding vectors corresponding to the column vectors in the corresponding coding matrix) in the precoding matrix at the same time as the precoding matrix assigned to each UE. Information is needed.

As described above, signaling overhead may be a problem when transmitting control information in a MIMO system, particularly a system using a limited channel feedback scheme as described above. However, there is no clear description of an efficient method for transmitting control information that minimizes signaling overhead in such an environment.

One object of the present invention for solving the above problems is to overwrite the control information for informing the receiving side of the transmission method used for data transmission in a mobile communication system, particularly a mobile communication system using multiple antennas. Its purpose is to provide an efficient representation and creation method that minimizes heads while maintaining maximum flexibility in data transfer.

Specifically, in one embodiment of the present invention, not only the control information for indicating the various data transmission schemes described above is shown, but also the combination of two or more control information is used to not only reduce the amount of necessary control signals, Provided is a method of expressing control information that can additionally reduce overhead that may occur when all of the bits used to represent the same combination are used.

One embodiment of the present invention for solving the above problems provides a method for efficiently expressing two or more control information. In the control information expression method according to the present embodiment, generating a total combination in consideration of a combination of two or more control information, and a maximum power of 2 equal to or less than the total number N of the total combinations generated in this way ( And selecting a combination corresponding to N ′) to generate a plurality of candidate combinations, and expressing the control information by using a specific combination selected from the plurality of candidate combinations generated as described above.

In this case, the plurality of candidate combinations may be set such that the number of combinations included in each is the same, but different combinations are included in each of the plurality of candidate combinations. The specific combination of the plurality of candidate combinations may be selected through information from an entity or predetermined information other than the control information.

Further, in the above-described embodiment, the two or more control information may be control information that can be transmitted only through a control channel, or control information that can be transmitted through both a control channel and a dedicated channel. In terms of reduction, this may be more efficient in the case of control information that can only be transmitted over the control channel.

On the other hand, in the specific embodiment, it is assumed that the method described above is applied to the MIMO system. In this case, the two or more control information includes rank number information and stream indication information of the transmission signal, and the entire combination generated considering the combination of each of the two or more control information is the rank per predetermined frequency unit. The combination of stream indication information corresponding to the number may be calculated and generated as a combination of stream indication information per rank number for each rank number.

In addition, in the example of the MIMO system as described above, the predetermined frequency unit is a frequency unit to which a precoding matrix is applied (hereinafter, referred to as "granularity unit"), and the size of the granularity unit is: It may be more efficient if the number of bits for indicating a combination corresponding to a power of up to two less than the total number of combinations is increased to reduce the number of bits below a predetermined number of bits. However, the present embodiment may be applied not only to a system in which the granularity unit is variable, but also to a system in which the granularity unit is fixed.

On the other hand, another embodiment of the present invention for solving the above problems provides a method for generating control information including at least rank number information and stream indication information of the transmission signal. In the control information generation method according to the present embodiment, a combination of stream indication information corresponding to a number of ranks per predetermined frequency unit is calculated as a combination of stream indication information per rank number for each rank number, and the total rank applicable to the transmission signal. Calculating a total combination including combinations of stream indication information per rank number corresponding to a number, and corresponding to a power of up to two (N ') less than or equal to the total number (N) of the total combinations; Selecting a combination to generate a plurality of candidate combinations, and selecting a specific combination of the plurality of candidate combinations to generate the control information for indicating a combination used for signal transmission among the specific combinations; .

In this case, the predetermined frequency unit may be a frequency unit to which a precoding matrix is applied, and the size of the predetermined frequency unit may be a combination corresponding to a power of up to two less than or equal to the total number of combinations. Increasing the number of bits to represent to below the predetermined number of bits may be more efficient.

According to the present invention as described above, in the mobile communication system, the transmitting side is to maintain the flexibility of the data transmission to the maximum while minimizing the overhead of control information for informing the receiving side of the transmission method used for data transmission. It is to provide a method for efficiently representing and generating.

In addition, the combination of two or more pieces of control information is not used to indicate control information for representing various data transmission schemes, but the amount of control signals required is not only reduced, but the number of bits for all of such combinations can be used. This can further reduce the overhead incurred.

In addition, the control information presentation method and the control signal generation method according to the present invention can be applied to a fixed system as well as a system having a variable rank and / or PMI granularity.

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

As described above, the present invention maximizes the flexibility of data transmission while minimizing overhead of control information for informing a receiving side of a transmission method used for data transmission in a mobile communication system, particularly a MIMO system. It is intended to provide an efficient method of generating the data. To this end, it is necessary to look at the structure of a control signal for indicating a data transmission method in the MIMO method. However, in the following description, the MIMO system is an example for explaining a method of efficiently expressing two or more control information and thus generating a control signal. The present invention provides a combination of two or more control information in addition to the MIMO system. It may be applied to any system that can be represented using.

First, the signal type transmitted in the MIMO scheme will be described. The following description focuses on the case of a downlink in which a transmitting end is a base station and a receiving end is a UE or a user terminal. However, the following description can be applied to uplinks in which the transmitting end and the receiving end are opposite without changing the basic features of the present invention.

In the MIMO technique, a single codeword (SCW) mode in which one codeword, which is an error detection unit, is transmitted to multiple antennas and transmitted simultaneously, and multiple codewords are simultaneously transmitted There is a Multi CodeWord (hereinafter referred to as "MCW") mode.

2 is a diagram illustrating a structure of a transmitting end of a single codeword (SCW) MIMO system.

At the transmitting end of the SCW system, one data packet is generated as a plurality of codeword blocks through encoding and modulation. This is again mapped to the MIMO stage, and combined with the number of physical antennas together with efficient antenna signaling to transmit to the receiver. Thereafter, the receiving end feeds back channel quality information of each antenna, so that a coding rate and a modulation scheme may be adjusted accordingly.

2 specifically illustrates generating M codeword blocks by demultiplexer 203 after the data packet is encoded by turbo encoder 201 and then by QAM modulator 202. Thereafter, the M codeword blocks are combined by the efficient antenna signaling module 204 into M _T signals, which are the number of physical antennas, and then transmitted to the receiving end through the OFDM module 205. In addition, the AP receiver 206 transmits channel quality information (CQI) of the feedback information received from the receiver to the rate predictor 207 to control the operation of the turbo encoder 201 and the QAM modulator 202 to control the coding rate and modulation. The control method is controlled, and the acknowledgment information of the M transmission codewords of the feedback information is transmitted to the demultiplexer 203.

3 is a diagram illustrating a structure of a transmitting end of a multiple codeword (MCW) MIMO system.

At the transmitting end of the SCW system, M data packets are encoded and modulated, respectively, to generate a plurality of codeword blocks. This is again mapped in the MIMO stage, and combined with the number of physical antennas together with efficient antenna signaling to transmit to the receiver. Thereafter, the receiving end feeds back channel quality information of each antenna, so that a coding rate and a modulation scheme may be adjusted accordingly.

3 specifically illustrates that M data packets are each encoded by turbo encoder 301 and then modulated by QAM modulator 302 to produce M codeword blocks. Thereafter, the M codeword blocks are combined by the efficient antenna signaling module 304 into M _T signals, the number of physical antennas, and then transmitted to the receiving end through the OFDM module 305. In addition, the AP receiver 306 transmits channel quality information (CQI) of the feedback information received from the receiver to the rate predictor 307 to control the operation of the turbo encoder 301 and the QAM modulator 302 to control the coding rate and modulation. It shows how to control the manner.

Meanwhile, the control information in the case of using the aforementioned limited channel feedback scheme in the SCW MU-MIMO scheme may basically include the following control signal field.

Control signal field Rule Resource allocation information It informs the resource portion to which the data of the scheduled UE in the transmission unit is allocated. Rank indication The rank number of the transmitted signal is indicated. PMI indication According to the rank number of the transmitted signal, the UE (receive end) is informed of which precoding matrix is allocated. Stream indication In the assigned precoding matrix, the UE (receiver) is informed of a column vector of the precoding allocated.

As shown in Table 1, the resource allocation information informs the resource part of which a transmitting end is allocated data of a scheduled UE in a transmission unit. In addition, the rank indication information is an index indicating the number of ranks of the signal transmitted by the transmitting end, that is, the number of independent signal transmission paths, and the PMI indication information is used in each resource portion allocated by the UE in the resource allocation field. Index which precoding matrix you are going to use. In addition, the stream indication information (Stream index) is a column that the UE uses within the precoding matrix defined in each resource portion allocated in the resource allocation field, specifically, a column in which it is assigned in the precoding matrix allocated to the corresponding resource region. Indicates whether to use a vector.

The PMI indication information and the stream indication information in the control information field may change in size of the corresponding control information according to the size of the frequency band unit to which the precoding matrix is applied in the entire frequency band. That is, when the size of the frequency band unit to which the precoding matrix is applied in the entire frequency band is large, PMI indication information indicating the index of the precoding matrix allocated in each frequency band and the stream in the precoding matrix allocated to each frequency band The size of the indication information is reduced, and when the size of the frequency band unit to which the precoding matrix is applied in the entire frequency band is small, PMI indication information indicating the index of the precoding matrix allocated to each frequency band and each frequency band The size of the stream indication information in the allocated precoding matrix is increased. In the following description, for convenience, a predetermined frequency unit to which the precoding matrix is applied as described above will be referred to as a "PMI granularity unit". In other words, if the PMI granularity unit is set large, this means that the precoding matrix is applied by dividing the entire frequency band into large frequency units. If the PMI granularity unit is set small, the entire frequency band is set to small frequency units. This means that dividing by applies a precoding matrix. Likewise, hereinafter, a predetermined frequency unit in which the number of ranks applied is fixed will be referred to as a "rank granularity unit".

Meanwhile, the size of the control information may vary according to the number of ranks of the transmission signal and the degree of flexibility of the rank change. That is, when the number of ranks available in the corresponding frequency band is specified, only the stream information corresponding to the number of ranks may be indicated, but when the number of ranks available in the corresponding frequency band is flexibly set, the number of each rank Since the stream combinations corresponding to all of the stream combinations must be represented using the control information, the size of the control information may increase.

Based on the above, the control information of the data transmission method will be described in detail as follows.

For example, suppose 4 Tx SCW MU-MIMO is applied in an OFDM system. In addition, it is assumed that the scheduler allocates data in units of resource blocks (RBs) when allocating a resource region for transmitting data. In addition, it is assumed that the total system bandwidth is 5 MHz, and 25 RB is included in the total system bandwidth.

At this time, if it is assumed that the precoding matrix for MIMO can be changed in units of 5 RB, and the precoding matrix can have 16 for each rank, the rank indication for notifying each receiver, among the control signal fields of Table 1, in particular The number of bits that the information, the PMI indication information, and the stream indication information should have may be represented as shown in Table 2 below.

Control signal field Amount [bits] Rank indication 10 bits (2 x 5) PMI indication 20 bits (4 x 5) Stream indication 10 bits (2 x 5)

The control signals of Table 2 may be transmitted in a control channel, or may be transmitted in a dedicated channel as needed. That is, when the amount of the control signal to be transmitted exceeds the range that the control channel can include, the dedicated channel may be used to transmit the control signal.

However, in the case of a control signal specified for each UE, such as stream indication information, it is one of control information that cannot be transmitted to a dedicated channel because the size of the control channel is small. Therefore, when the amount of necessary control information is increased and exceeds the range that the control channel can include, an overhead problem of the control signal may occur, thereby causing a problem in that resources cannot be efficiently used.

Accordingly, an embodiment of the present invention is to propose a method for efficiently reducing the number of bits for indicating control information when it includes such a plurality of control information, especially control information that can be transmitted only through a control channel. .

There may be various ways to reduce the number of bits for indicating control information. Particularly, in the present embodiment, although each control information may be separately expressed, it is possible to reduce the number of bits required to represent the control signal by combining control information associated with each other among the control information. It is intended to provide a method of information presentation.

For example, the rank indication information and the stream indication information have a relationship in which the number of stream indication information corresponding to each rank number decreases as the number of ranks indicated by the rank indication information decreases. Therefore, the present embodiment proposes a method of representing control information by combining the rank indication information and the stream indication information. When the rank indication information and the stream indication information are collectively represented in the system under the same condition as shown in Table 2 above, The number of bits for representing each control information is reduced from 20 bits to 17 bits as shown in Table 2 to obtain a 3-bit gain.

In the embodiment in which the rank indication information and the stream indication information are combined as described above, the number of control signal bits required under various PMI granularity and rank granularity conditions can be expressed as follows.

PMI granularity 5RB granularity Whole BW granularity Rank granularity 5RB granularity 17 bits (a) N / A Whole BW granularity 11 bits (b) 4 bits (c)

Each case represented by (a), (b) and (c) of Table 3 will be described below in detail with reference to the accompanying drawings.

4 to 6 are conceptual diagrams for explaining the number of bits of the control signal required under various PMI granularity and rank granularity conditions.

First, FIG. 4 illustrates a case where both the rank granularity and the PMI granularity are set to 5 RB when the total system bandwidth corresponds to 25 RB in the case of Table 3 (a). . Specifically, in FIG. 4, the entire system band of 25 RBs is divided into granularity sections of 5 RBs, and is indicated as A, B, ..., E. FIG.

As shown in this example, with a rank granularity of 5 RB and a PMI granularity, 4, 3, 2, 1 for each of the granularity unit areas of A, B, ..., E, respectively, The number of combination per gragularity unit of 3, 2, 1 total 10 rank-stream indication information is possible, so that 100000 (= 10 ⁵ ) rank-stream indication information combinations in the entire 25 RB region can be obtained. It can be seen that. Therefore, in order to represent such a combination of 100,000 control information, a 17-bit control signal field is required as indicated in Table 3 (a).

Next, Figure 5 corresponds to the case of Table 3 (b), when the total system bandwidth corresponds to 25 RB, having a rank granularity corresponding to the total system bandwidth and a PMI granularity of 5 RB Is shown. Specifically, in FIG. 5, the entire system band of 25 RBs is divided into granularity sections of 5 RBs and is denoted as A, B, ..., E. FIG.

If you have a rank granularity of the total system bandwidth and a PMI granularity of 5 RBs as in this example, four for each PMI granularity unit (for each region A, B, ..., E) for rank 4 It can be seen that the combination of stream indication information is possible, resulting in a total of 4 ⁵ combinations for rank 4 within the entire system band. In addition, it can be seen that one of the combinations of 3 ⁵ , 2 ⁵ , and 1 may be generated in the same manner for the ranks 3, 2, and 1. In addition, it can be seen that 1300 (= 4 ⁵ + 3 ⁵ + 2 ⁵ + 1) combinations can be obtained by adding the total number of combinations per rank. Therefore, in order to represent such a combination of 1300 control information, an 11-bit control signal field is required as shown in (b) of Table 3 above.

Lastly, FIG. 6 illustrates a case where a rank granularity and a PMI granularity corresponding to the total system bandwidth are used when the total system bandwidth corresponds to 25 RB in the case of Table 3 (c). have.

With the rank granularity and PMI granularity of the total system bandwidth as in this example, four combinations for rank 4, three combinations for rank 3, 2 for rank 2, as shown in FIG. It can be seen that one combination is possible for branch combination, rank 1, so that a total of 10 combinations can occur. Therefore, in order to indicate such a combination of the 10 control information, as shown in (c) of Table 3, a 4-bit control signal field is required.

Tables 3 (a), (b), (c) and FIGS. 4 to 6 show that the rank granularity and / or PMI granularity can be adjusted to reduce the number of control bits required. However, in some cases or in accordance with the system, the granularity unit may be used in a fixed form, and the present invention is a system capable of adjusting the granularity unit as well as a system in which the granularity unit is fixed as described above. In addition, to provide a method for efficiently reducing the amount of control information for indicating a signal transmission method while minimizing performance degradation of the system.

7 is a flowchart illustrating a method of expressing control information such that overhead is minimized according to an embodiment of the present invention.

According to the present embodiment, first, the entire combination is generated in consideration of the combination of two or more pieces of control information (S701). That is, as described above, in the entire system band having 25 RBs, the entire combination of rank indication information and stream indication information is generated under given rank granularity unit and PMI granularity unit conditions as in the case of FIGS. 4 to 6. .

However, as can be seen from the description of FIG. 4 to FIG. 6, since the number of combinations that can be represented by the number of bits required to represent the entire combination is generally larger than the actual total combination, waste of resources may occur. Can be. For example, as shown in FIG. 6, when the total number of combinations is 10, a 4-bit control signal is required to indicate this, and 10 combinations can be represented using the 4-bit control signal as follows. have.

Rank & stream index The number of transmission rank Stream index Rank & stream index The number of transmission rank Stream index 0 One 0 8 4 2 One 2 0 9 4 3 2 2 One 10 - - 3 3 0 11 - - 4 3 One 12 - - 5 3 2 13 - - 6 4 0 14 - - 7 5 One 15 - -

However, as shown in Table 4, when using a 4-bit control signal to represent the total 10 combinations, 16 combinations that can be represented by a 4-bit control signal represents the actual total of 10 combinations There is a surplus. In other words, resources cannot be used efficiently.

Therefore, in the present embodiment, assuming that the total number of combinations generated in step S701 is N, a plurality of candidate combinations including as many combinations of N or less as a power of two (hereinafter referred to as N ') are generated. (S702) The method of expressing the control information using the specific combination selected from the plurality of candidate combinations (S703) is limited. For example, as described above, in the example of FIG. 6, a plurality of candidate combinations including eight combinations of ten total combinations may be generated. For example, candidate combinations such as Tables 5 and 6 below may be generated. Can be.

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 One 5 3 2 6 4 0 7 4 One

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 One 5 3 2 6 4 2 7 4 3

Tables 5 and 6 are stream indexes 0, 1, 2, and 3 of the four combinations corresponding to stream index 0, 1, 2, and 3, which are possible in the case of rank 4 in Table 4, and Table 6 is stream index 2, An example of generating two candidate combinations having a total of eight combinations by selecting two combinations each representing three is shown. That is, Table 5 and Table 6 above are examples of having two candidate combinations as a combination that can be used to express control information, and each UE has 0, 1 or 2, which streams it can have when the rank is 4; It has a constraint divided by three.

That is, in the present embodiment, the plurality of candidate combinations generated in step S702 have the same number of combinations included in each, but can be maintained to have flexibility in expressing a signal transmission method by setting them to include different combinations. .

Meanwhile, Tables 7 and 8 below show examples of selecting two candidate combinations in a manner different from those of Tables 5 and 6.

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 One 5 3 2 6 4 0 7 4 2

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 One 5 3 2 6 4 One 7 4 3

That is, Tables 7 and 8 show stream indexes for rank 4 unlike the schemes in which the candidate combinations in the examples of Tables 5 and 6 restrict stream indexes to rank 4 by 0, 1, or 2 and 3. The example which puts restrictions by dividing by 0, 2 or 1, 3 is shown.

Finally, Tables 9 to 14 below show examples of selecting two candidate combinations in a manner different from those of Tables 5 and 6.

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 One 5 4 0 6 4 One 7 4 2

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 One 5 4 0 6 4 One 7 4 3

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 One 5 4 One 6 4 2 7 4 3

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 2 5 4 0 6 4 One 7 4 2

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 2 5 4 0 6 4 One 7 4 3

Rank & stream index The number of transmission rank Stream index 0 One 0 One 2 0 2 2 One 3 3 0 4 3 2 5 4 One 6 4 2 7 4 3

Unlike Tables 5 to 6, or Tables 7 and 8, Tables 9 to 14 provide a more flexible signal transmission scheme by placing constraints on a specific stream index not only for rank 4 but also for rank 3. An example of generating branch candidate combinations is shown. However, the present embodiment need not be limited to the above-described example, and candidate combinations may be generated to include various combinations to maximize system performance.

Information about a specific combination to be used to indicate a combination of control information for indicating a signal transmission method among the plurality of candidate combinations may be informed through an upper layer or any other signal for each UE. In addition, a method of implicitly informing the transmission of specific information is also possible.

For example, when generating candidate combinations as shown in Tables 7 and 8, the scheduler can designate which candidate combinations of Tables 7 and 8 each UE should refer to. In addition, when generating candidate combinations as shown in Tables 9 to 14, the scheduler can designate which candidate combination of each of the six candidate combinations of Tables 9 to 14 should be referred to.

As described above, the control information expression method and the control information generation method according to an embodiment of the present invention can be used not only when the rank and / or PMI granularity is variable but also when it is fixed. In addition, the present embodiment may preferably be applied to a system with variable rank and / or PMI granularity to further reduce the amount of control signals required as described above with respect to FIGS. 6 and 7.

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. 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.

As described above, the present invention can maintain the flexibility of data transmission as much as possible while minimizing the overhead of control information for informing the receiving side of the transmission method used for data transmission in the mobile communication system. It can be applied to various mobile communication systems as well as MIMO communication system.

FIG. 1 is a diagram illustrating the concept of a spatial multiplexing and spatial divisional multiple access scheme used in a MIMO communication system.

2 is a diagram illustrating a structure of a transmitting end of a single codeword (SCW) MIMO system.

3 is a diagram illustrating a structure of a transmitting end of a multiple codeword (MCW) MIMO system.

4 to 6 are conceptual diagrams for explaining the number of bits of the control signal required under various PMI granularity and rank granularity conditions.

7 is a flowchart illustrating a method of expressing control information such that overhead is minimized according to an embodiment of the present invention.

Claims (8)

In the method of expressing two or more control information, Generating a total combination in consideration of the combination of each of the two or more control informations; Generating a plurality of candidate combinations by selecting a combination corresponding to a maximum power of two less than or equal to the total number of the combinations; And And expressing the control information using a specific combination selected from the plurality of candidate combinations. The method of claim 1, The plurality of candidate combinations include the same number of combinations included in each, but different combinations from each other. The method of claim 1, In the control information presentation step, And selecting the specific combination from among the plurality of candidate combinations through information from an upper layer entity or predetermined information other than the control information for the layer on which the control information presentation method is performed. The method of claim 1, And the at least two control information includes control information that can only be transmitted via a control channel. The method of claim 1, The at least two control information includes rank number information and stream indication information of a transmission signal, The total combination generated in consideration of the combination of each of the two or more control information is calculated by calculating the combination of the stream indication information corresponding to the number of ranks per predetermined frequency unit as a combination of stream indication information per rank number for each rank number. Control information presentation method to generate. The method of claim 5, wherein The predetermined frequency unit is a frequency unit to which a precoding matrix is applied. The size of the predetermined frequency unit, And increasing the number of bits for representing a combination corresponding to a maximum power of two less than or equal to the total number of combinations to reduce the number of bits below a predetermined number of bits. A method of generating control information including at least rank number information of a transmission signal and stream indication information, the method comprising: Calculating the combination of the stream indication information corresponding to the rank number per predetermined frequency unit as the combination of the stream indication information per rank number for each of the rank numbers; Calculating a total combination including combinations of stream indication information per rank number corresponding to a total rank number applicable to the transmission signal; Generating a plurality of candidate combinations by selecting a combination corresponding to a maximum power of two less than or equal to the total number of the combinations; And Selecting a specific combination of the plurality of candidate combinations, and generating the control information for indicating a combination used for signal transmission among the specific combinations. The method of claim 7, wherein The predetermined frequency unit is a frequency unit to which a precoding matrix is applied. The size of the predetermined frequency unit, And increasing the number of bits for indicating a combination corresponding to a maximum power of two less than or equal to the total number of combinations to reduce the number of bits below a predetermined number of bits.

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