KR100972876B1 - Method and Apparatus for Determining Transmission Scheme of MIMO System - Google Patents

Abstract

A method of determining a transmission method of a MIMO system according to an embodiment of the present invention, in which a transmission method is determined by a MIMO mode and an MCS level selected according to a given channel state in a receiver of a MIMO system, may include: A method for determining a transmission method of an input / output) system, the method comprising: (a) determining an effective CINR of a received signal for each MIMO mode and modulation method applied to the MIMO system; (b) selecting a first MIMO mode and an MCS level pair according to the effective CINR among the MIMO mode and a modulation and coding scheme (MCS) level of the modulation scheme; And (c) determining a transmission scheme of the MIMO system based on a second MIMO mode and MCS level pair selected according to a data rate of the first MIMO mode and MCS level pair among the first MIMO mode and MCS level pair. Characterized in that it comprises a step.

MIMO mode, MCS level, effective CINR

Description

Method and apparatus for determining transmission method of MIO system {Method and Apparatus for Determining Transmission Scheme of MIMO System}

The present invention relates to a method and apparatus for determining a transmission scheme of a MIMO system, and more particularly, to a method and apparatus for determining a transmission scheme by a MIMO mode and an MCS level selected according to a given channel state in a receiver of a MIMO system.

In general, wireless channel environments inevitably introduce errors due to many factors such as multi-path interference, shadowing, propagation attenuation, time-varying noise, interference and fading, etc. This leads to loss of information. This loss of information causes severe distortion in the actual transmission signal, which causes a decrease in the overall performance of the wireless communication system.

Meanwhile, a diversity method is used to remove instability of communication due to fading. It is possible to increase the reliability of the communication link through diversity gain without increasing the bandwidth by equipping the transceiver with multiple antennas to secure additional space for resource utilization, and to increase the transmission capacity through parallel transmission through spatial multiplexing. You can also increase it.

1 is a diagram illustrating an outline of a single input single output (SISO) system and a multiple input multiple output (MIMO) system.

As shown in FIG. 1A, the SISO system is a technology for performing a single input / output transmission through one channel (H) formed between one transmit antenna (TxAnt) and one receive antenna (RxAnt). When each side and the receiving side communicate with one antenna, multipath phenomenon occurs due to obstacles in the propagation path such as hills and steel towers, causing problems due to fading.In digital communication such as wireless Internet, data rate decreases and error increases Cause.

In contrast, the MIMO system transmits data through multiple paths by increasing the number of antennas of a base station and a terminal, reduces interference by detecting signals received on each path at the receiving end, and transmits efficiency through space-time diversity and spatial multiplexing at the transmitting end. Can increase. FIG. 1B illustrates a 2x2 MIMO system using two transmit antennas and two receive antennas of which, as shown, the first and second transmit antennas TxAnt1 and TxAnt2 and the first and second Four channels, that is, a first channel H11, a second channel H12, a third channel H21, and a fourth channel H22 are formed between the reception antennas RxAnt1 and RxAnt2.

In the case of the MIMO mode, a space time transmit diversity (STTD) and a spatial multiplexing (SM) mode may be classified according to a method of allocating a plurality of antennas and symbols to be transmitted. In the 802.16d / e-based portable Internet system, STTD and SM can be selectively transmitted. Therefore, a method of selecting such a MIMO mode according to channel conditions is under development.

In particular, when the MIMO mode is selected by considering only the very fundamental channel characteristics (for example, the variation of the MIMO channel strength and the strength of the MIMO channel) regarding the channel state, the influence of the error due to the channel estimation is ignored and performance degradation occurs. Since the decoding schemes vary depending on the MIMO mode and the characteristics thereof are different from each other, there is a problem in that the implemented results do not show ideal characteristics.

In addition, in addition to the problem of the selection of the MIMO mode, the MCS level (Modulation and Coding Scheme level) must be determined to find the optimal data rate (throughput) in each mode, the method and procedure is not clear. There was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. In the method and apparatus for determining a transmission scheme of a MIMO system, a method and apparatus for determining a transmission scheme capable of optimizing a transmission rate in consideration of transmission rates in a corresponding channel as well as fundamental channel characteristics To provide a technical problem.

Another object of the present invention is to provide a method and apparatus for determining a transmission method based on an MCS level suitable for the MIMO mode as well as a MIMO mode in determining a transmission method of a MIMO system.

Another object of the present invention is to provide a method and procedure for determining an MIMO mode and an MCS level that can optimize an error rate and a transmission rate of a signal in a communication channel.

A method of determining a transmission method of a MIMO system according to an aspect of the present invention for achieving the above object is a method of determining a transmission method of a MIMO (multi-input and output) system to which at least one MIMO mode is applied, (a) the MIMO system Determining an effective CINR (Effective CINR) of a received signal for each MIMO mode and modulation scheme applied to the method; (b) selecting a first MIMO mode and an MCS level pair according to the effective CINR among the MIMO mode and a modulation and coding scheme (MCS) level of the modulation scheme; And (c) determining a transmission scheme of the MIMO system based on a second MIMO mode and MCS level pair selected according to a data rate of the first MIMO mode and MCS level pair among the first MIMO mode and MCS level pair. Characterized in that it comprises a step.

In accordance with another aspect of the present invention, a method of determining a transmission method of a MIMO system is performed by the receiver for feedback to the transmitter in a MIMO system in which a transmitter and a receiver each use at least one antenna. A method of determining a transmission method of a MIMO system, the method comprising: determining an effective CINR of a received signal for each MIMO mode and modulation method applied to the MIMO system; And determining a transmission scheme of the MIMO system by a first MIMO mode and an MCS level pair selected using the effective CINR among the MIMO mode and the MCS level of the modulation scheme.

An apparatus for determining a transmission method of a MIMO system according to an aspect of the present invention for achieving the above object is a MIMO (multi-input and output) system to which at least one MIMO mode is applied, for each MIMO mode and modulation applied to the MIMO system. An effective CINR determination unit for determining an effective CINR of the received signal for each method; A MIMO mode and MCS level pair selector configured to select a first MIMO mode and an MCS level pair according to the effective CINR among the MIMO mode and the MCS level of the modulation scheme; And a MIMO mode and an MCS level determiner configured to determine a transmission method of a MIMO system based on a second MIMO mode and an MCS level pair selected from the first MIMO mode and an MCS level pair according to a transmission rate of the first MIMO mode and an MCS level pair. It is characterized by including.

As described above, according to the present invention, a transmission scheme capable of optimizing the transmission rate may be determined in consideration of the transmission rate in the corresponding channel as well as the fundamental channel characteristics in the MIMO system.

In addition, the present invention is determined by subdividing the feedback information for the transmission scheme fed back to the transmitter from the receiver of the MIMO system for each MIMO mode and MCS level, so that not only the MIMO mode suitable for the channel but also the MCS level for the optimal transmission rate in the MIMO mode By reflecting this in the transmission scheme, it is possible to increase the transmission speed to the terminal and to expand the coverage of the MIMO system.

In addition, in the process of determining the transmission method by the MIMO mode and the MCS level in the receiver of the MIMO system, another effect of clearly presenting the procedure and method for applying the channel capacity, the error rate and the transmission rate to the determination process have.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating a transmitter of an N × M MIMO system according to an embodiment of the present invention, and FIG. 3 is a diagram illustrating a receiver of an N × M MIMO system according to an embodiment of the present invention. As a base station (BS), a receiver may be referred to as a mobile station (MS), but this is merely an example, and it can be easily understood that the roles of the base station and the terminal for the transmitter or the receiver can be switched with each other. .

Referring to FIG. 2, the transmitter 200 includes an encoder 210, an interleaver 220, a modulator 230, a multiplexing and spatial encoder 240, a plurality of antennas, and a feedback message decoder. 250, a scheduler 260, and a transmission scheme selector 270. Referring to FIG. 3, the receiver 300 includes a plurality of antennas, a demultiplexer and a spatial decoder 310, A grandfather 320, a deinterleaver 330, a decoder 340, a MIMO channel parameter estimator 350, and a transmission method determination unit 360 are included.

Hereinafter, for the convenience of explanation, the operation of the transmitter will be described first, followed by a brief description of the space-time coding (STC) related to the present invention, followed by the operation of the receiver.

In the transmitter 200, the encoder 210 outputs the encoded bit Ci by channel encoding the n-th bit Un containing information to be transmitted in the same manner as in the Forward Error Correction (FEC). For example, convolutional encoding, Convolutional Turbo Codes (CTC), or the like is used as an encoding method.

For this coded bit Ci, the interleaver 220 rearranges according to a predetermined rule such that each of the successive Cis having a high correlation is transmitted through channels having low cross correlation. For example, the above-described rule may be defined to map consecutive Cis to non-contiguous subcarriers, or alternately map the consecutive Cis to lower or upper bits in constellation.

For the interleaved b _i , the modulator 230 maps one or more bits to one symbol using a modulation scheme such as QPSK or QAM. Here, the modulator 230 determines the modulation scheme according to the MCS level (Modulation and Coding Scheme) selected by the transmission scheme selector 270 with reference to the feedback message of the receiver 300.

In addition, the multiplexing and spatial encoder 240 multiplexes the modulated symbols in a manner such as orthogonal frequency division multiplexing (OFDM) or code division multiplexing (CDM), and then according to the MIMO mode selected by the transmission method selection unit 270. Some or all of the entire symbols may be transmitted to the receiver 300 using a plurality of antennas.

At this time, the mapping between the symbol and the antenna is called a MIMO mode or Space-Time Coding (STC), and the MIMO mode is a Space-Time Transmit (STTD) according to a Single Input Multiple Output (SIMO) and an encoding method. Diversity and Spatial Multiplexing (SM).

STTD is a method of repeatedly transmitting two different symbols by repeatedly changing the phase of each symbol and an antenna to transmit each symbol, and an Alamouti method is typical. It guarantees stable and improved data rate. On the other hand, SM is a method of simultaneously transmitting and receiving a plurality of different symbols through a plurality of antennas, typically the BLAST method, and increases the data rate.

In particular, in IEEE 802.16d / e-based portable Internet system, since STTD and SM are specified to be selectively transmitted, a technology for transmitting them after proper performance comparison is required.

Since the relative performance of the SIMO, STTD and SM is different depending on the channel state, as described above, these should be selected and used appropriately. To this end, the receiver 300 analyzes channel characteristics from the signal transmitted from the transmitter 200 and then determines any one of SIMO, STTD and SM according to a predetermined determination criterion, and encodes information about the transmitter 200 to encode the transmitter 200. To send, ie feedback.

In this case, the encoded information includes a MIMO mode and an MCS level determined by the receiver 300, and is transmitted to the transmitter 200 at a predetermined time point. Hereinafter, information encoded and transmitted as described above will be referred to as a feedback message.

In FIG. 2, the feedback message decoder 250 decodes the information transmitted from the receiver 300 and provides it to the transmission method selector 270, and the scheduler 260 selects a transmission method such as a resource state and a scheduling strategy. To the unit 270. Accordingly, the transmission method selection unit 270 may finally determine the MIMO mode and the MCS level to be transmitted to the receiver 300 in consideration of a resource state and a scheduling strategy.

Meanwhile, in FIG. 3, the receiver 300 demultiplexes received signals from a plurality of antennas in symbol units and demultiplexes the spatial decoder 310 and performs ST decoding.

The demodulator 320 demodulates the demultiplexed and decoded symbols to calculate a bit matrix. The deinterleaver 330 deinterleaves the inverse of the interleaving scheme applied by the transmitter 200, and the decoder 340 decodes the demultiplexed symbols. The information bit estimate originally transmitted by the transmitter 200 is output based on the deinterleaved bit string.

In addition, the receiver 300 uses the MIMO channel parameter estimator 350 that analyzes MIMO channel characteristics, such as MIMO channel estimation and noise power, from the signal transmitted from the transmitter 200, and uses the estimated MIMO channel and noise power. The method may further include a transmission method determination unit 360 that determines the MIMO mode and the MCS level, and the MIMO channel parameter estimator 350 may be included in the configuration of the transmission method determination unit 360.

The transmission method determiner 360 determines a physical carrier-to-interference and noise ratio (PCINR) and an effective CINR of a received signal to determine a MIMO mode according to a channel environment and perform adaptive modulation and coding (AMC). Effective Carrier-to-Interference and Noise Ratio (ECINR) is calculated and the MIMO mode and MCS level are determined in consideration of an error rate and a data rate and throughput. Then, by transmitting a feedback message including the determined MIMO mode and MCS level to the transmitter 200, the transmission scheme of the MIMO system is determined.

4 is a block diagram illustrating a transmission method determination unit 360 according to an embodiment of the present invention. The transmission method determination unit 360 includes an effective CINR determination unit 402, a MIMO mode, and an MCS level pair selection unit 404. ), The MIMO mode and the MCS level determiner 406 and the feedback unit 408.

The effective CINR determiner 402 determines the ECINR of the received signal for each MIMO mode and modulation scheme used by the MIMO system. The effective CINR determining unit 402 calculates a plurality of PCINRs according to the MIMO mode used by the MIMO system from the received signal, and receives the received signals using a mapping table of channel capacities according to the modulation schemes of the plurality of physical CINRs and the received signal. Determine the ECINR of the signal.

In addition, the effective CINR determination unit 402 determines the ECINR for every MIMO mode and modulation scheme used by the MIMO system for the MIMO mode and modulation scheme that the receiver 300 can use as a reception method. Hereinafter, specific operations of the effective CINR determination unit 402 will be described with reference to FIGS. 5 to 7.

5 is a block diagram illustrating an effective CINR determining unit 402 according to an embodiment of the present invention, wherein the effective CINR determining unit 402 includes a physical CINR calculating unit 502 and an effective CINR mapping unit 504. .

The physical CINR calculator 502 calculates a plurality of PCINRs according to the MIMO mode used by the MIMO system from the received signal of the receiver 300.

First, a method of acquiring a sample of a received signal in order to calculate the PCINR by the physical CINR calculation unit 502 will be described as an example. The physical CINR calculation unit 502 may use a downlink subframe DL sub- which is a reception signal. In the frame, a segment having similar channel characteristics is defined, and the PCINR of the segment is calculated from one or more tones (sub-carriers) constituting the segment.

This segment becomes a sample for the calculation of the PCINR, and the channel characteristics are estimated by the pilot tone of the received signal. The physical CINR calculation unit 502 can obtain PCINRs for all MIMO modes used by the MIMO system after the estimation process based on the filer tone of the received signal.

Furthermore, the ECINR described later is a value representing a block composed of one or more segments, and therefore, the ECINR is calculated from one or more PCINR values.

Next, we will look at the signal model and notation for the MIMO system before explaining how to calculate the PCINR.

The signal model of the MIMO system may be represented by Equation 1 below.

Where N _T is Number of transmit antennas, N _R is the number of receive antennas, N _R is greater than N _T Greater than or equal to And, Es is the total energy of the transmitted symbols, y is a received signal vector with N _R dimensions, s is an input signal vector with N _T dimensions, and H is a channel matrix with N _R × N _T dimensions. The (i, j) th element of H corresponds to h _ij , which is a channel response between the jth transmit antenna and the ith receive antenna. N is a noise and interference vector in the N _R dimension and has a dispersion matrix K.

Hereinafter, the PCINR calculation method for each MIMO mode of the physical CINR calculation unit 502 will be described.

First, when the MIMO mode is STTD, the physical CINR calculation unit 502 calculates M PCINRs for M segments (M is a positive integer), and m of the M m through an operation corresponding to Equation 2 below. The PCINR of the first segment is calculated.

은 m번째 세그먼트의 PCINR을 의미하고, k(m)_i는 m번째 세그먼트의 i번째 수신 안테나에 대한 노이즈 및 간섭 파워의 합이고,

는 통상적인 SISO(Single Input Single Output) CINR 에 의해 구할 수 있으므로 자세한 설명은 생략한다.here,

Is the PCINR of the mth segment, and k (m) _{i is the} mth segment sum of noise and interference power for the i < th > receive antenna,

Since can be obtained by the conventional SISO (Single Input Single Output) CINR, a detailed description thereof will be omitted.

On the other hand, when the MIMO mode is SM, and when using ML (Maximum Likelihood) as a signal detection method, the physical CINR calculation unit 502 calculates the PCINR of the m-th segment of the M through the operation corresponding to Equation 3 below. do.

은 등가의 퍼스트림(equivalent per-stream) PCINR이고, 잘 알려진 샤논의 채널 용량 공식(Shannon's capacity formula)에 의해 유도될 수 있다. 그리고, C_stream(m)은 퍼스트림 채널 용량이다. 비록, 복수의 안테나에 따른 복수의 스트림이 존재 하지만, 본 발명의 일 실시예에서는 각 스트림의 평균적인 PCINR을 목적하는 PCINR로서 선택한다.here,

Is an equivalent per-stream PCINR and can be derived by the well-known Shannon's capacity formula. And C _stream (m) is the perstream channel capacity. Although there are a plurality of streams according to a plurality of antennas, in one embodiment of the present invention, the average PCINR of each stream is selected as the desired PCINR.

On the other hand, when the MIMO mode is SM, and when a minimum mean square error (MMSE) is used as the signal detection method, the physical CINR calculating unit 502 calculates the PCINR through an operation corresponding to Equation 4 below.

를 만족한다.here,

.

는 j번째 스트림의 m번째 세그먼트의 PCINR을 의 미하고, W(m)^H는 W(m)의 복소공액 전치(Hermitian transpose)를 의미한다. 그리고, U는 세그먼트를 이루는 톤의 개수를 의미한다. In Equation 4,

Denotes the PCINR of the m-th segment of the j-th stream, and W (m) ^H denotes the complex conjugate transpose of W (m). U denotes the number of tones forming a segment.

According to Equation 4, the PCINR value representing the segment is obtained from the SNR of each tone constituting the segment. That is, the PCINR of the segment is conceptually expressed as {(U signal power average) / (U noise power average average)}.

On the other hand, if the MIMO mode is SIMO (Sigle Input Multiple Output), the physical CINR calculation unit 502 calculates the PCINR using the Maximum Ratio Combining (MRC) technique. Here, since the PCINR related to the MRC can be calculated by a general method, a detailed description thereof will be omitted.

The effective CINR mapping unit 504 includes a cumulative average calculating unit 506 and a cumulative average mapping unit 508, and according to a modulation scheme used by the plurality of PCINRs and the MIMO system calculated by the physical CINR calculating unit 502. The channel capacity mapping table is used to determine the ECINR of the received signal.

The cumulative average calculating unit 506 obtains a plurality of channel capacities mapped to the plurality of PCINRs by the mapping table, and calculates a cumulative average of the plurality of channel capacities.

The cumulative average mapping unit 508 determines the PCINR mapped to the cumulative average calculated by the cumulative average calculating unit 506 as the ECINR of the received signal. Hereinafter, the operation of the effective CINR mapping unit 504 will be described in detail with reference to FIGS. 6 and 7.

6 is a block diagram illustrating an operation of an effective CINR mapping unit 504 according to an embodiment of the present invention, and FIG. 7 is a channel capacity function according to a modulation scheme in a MIMO system according to an embodiment of the present invention. Is a graph of.

When the effective CINR mapping unit 504 receives the M PCINRs calculated by the physical CINR calculation unit 502, the first selection unit 602 selects a path to be processed by the first selection unit 602 according to a predetermined modulation scheme. . Here, the predetermined modulation scheme is any one of the modulation schemes used by the MIMO system according to the embodiment of the present invention.

The cumulative average calculating unit 506 obtains channel capacities mapped to M PCINRs using a mapping table of channel capacities. Here, the channel capacity is a channel capacity function f (·) value based on the AWGN channel model according to a modulation scheme.

 That is, the mapping table stores PCINR values and channel capacity function values mapped thereto. The stored function value is a value obtained through the graph of FIG. 7.

The channel capacity has a relationship as shown in the graph of FIG. 7 according to the signal to noise ratio (SNR) measured at the receiver 300. In theory, the channel capacity is in accordance with Shannon's channel capacity curve 702, but the channel is actually according to a modulation technique. Capacity is limited. That is, the value is determined according to the QPSK channel capacity curve 704, the 16QAM channel capacity curve 706, or the 64QAM channel capacity curve 708 of FIG. 7.

As an example, when the modulation scheme is QPSK, the PCINR of 15 dB (SNR in FIG. 7) is 2 according to the QPSK channel capacity curve 704. Such mapping information is stored in the mapping table.

)를 곱한 값에 맵핑되는 채널 용량을 획득할 수 있다.In addition, the cumulative average calculator 506 may perform mapping by using a weight for correcting the mapping result as a penalty factor. As an example, the weighting of the PCINR value (

Channel capacity mapped to a value multiplied by

The cumulative average calculator 506 calculates a cumulative average of the acquired M channel capacities. As an example, when the modulation scheme is QPSK, the cumulative average obtained through the above-described process of the cumulative average calculating unit 506 may be represented by Equation 5 below.

The cumulative average mapping unit 508 uses the mapping table once more to determine the PCINR (SNR of FIG. 7) mapped to the channel capacity corresponding to the cumulative average as ECINR.

)를 곱한 값을 ECINR으로 결정할 수 있다.In addition, the cumulative average mapping unit 508 may perform mapping by using weights for correcting the penalty factor mapping result. Where the weight to the PCINR mapped to the cumulative average (1 /

) Can be determined as ECINR.

으로서 표현할 수 있다.As an example, when the modulation scheme is QPSK, the above-described operation of the cumulative average mapping unit 508 may be

Can be expressed as

The second selector 604 transmits the ECINR determined by the cumulative average mapping unit 508 through a path selected according to a modulation scheme.

Although the above-described ECINR determination process has been described only for a predetermined modulation method, since the ECINR is repeatedly performed for all modulation methods used by the MIMO system, the ECINR is determined for each modulation method.

Referring back to FIG. 4, the MIMO mode and the MCS level pair selector 404 may use the first MIMO mode according to the ECINR determined by the effective CINR determiner 402 among the MIMO mode and the modulation scheme MCS level used by the MIMO system. And MCS level pairs. Hereinafter, detailed operations of the MIMO mode and the MCS level pair selector 404 will be described with reference to FIGS. 8 to 10.

8 is a block diagram illustrating a MIMO mode and MCS level pair selector 404 according to an embodiment of the present invention. The MIMO mode and MCS level pair selector 404 includes a comparator 802 and a selector 804. ).

The comparator 802 sets an SNR for satisfying a condition in which an error rate is equal to or less than a first threshold for each MIMO mode and MCS level used by the MIMO system, and compares the second threshold with the ECINR. In one embodiment, the error rate may be any one of a block error rate (BLER), a packet error rate (PER), and a frame error rate (FER).

The selector 804 selects the MIMO mode and MCS level pair having an effective CINR greater than or equal to the second threshold as a result of the comparison of the comparator 802 as the first MIMO mode and MCS level pair. Here, the first MIMO mode and MCS level pairs belong to a candidate group of MIMO mode and MCS level pairs for determining a transmission scheme of a MIMO system.

The comparator 802 and the selector 804 perform an operation for selecting a first MIMO mode and MCS level pair for all MIMO modes and MCS levels used by the MIMO system.

9 is a view for explaining an operation of comparing the ECINR and the second threshold value according to the error rate according to an embodiment of the present invention.

The graph of FIG. 9 shows a block error rate (BLER) of a Forward Error Correction (FEC) block with respect to the SNR of the received signal of the receiver 300.

For example, FIG. 9 illustrates an SNR that a received signal should have at a specific MCS level when a BLER condition for determining a transmission scheme of a MIMO system is BLER 1% or less (target BLER).

When QPSK 1/2 is used as the MCS level, the relationship between BLER and SNR is shown in the first curve 902 of FIG. 9, and the received signal is shown in FIG. 9 to satisfy the " BLER 1% or less " For reference, it should have an SNR 906 of about 1.8 dB or more.

When the MIMO mode is STTD and the MCS level is QPSK 1/2, the comparator 802 obtains an SNR (second threshold) for satisfying “BLER 1% (first threshold) or less”. Here, the SNR (second threshold) is about 1.8 dB 906. The comparison unit 802 then compares the SNR (second threshold) with the ECINR 908 determined by the effective CINR determination unit 402. However, it can be seen that the ECINR 908 is larger than the second threshold because the ECINR 908 is located on the right side of the graph than the second threshold of 1.8 dB 906.

When the selector 804 receives a comparison result from the comparator 802 that the ECINR 908 is larger than a second threshold, the selection unit 804 determines a MIMO mode and MCS level pair based on the ECINR 908. pair) STTD and QPSK 1/2 are selected as entries of candidate groups for the transmission scheme determination of the MIMO system.

As another example, when the MIMO mode is STTD and the MCS level is QPSK 3/4, the ECINR 910 determined by the effective CINR determining unit 402 is greater than a second threshold corresponding to QPSK 3/4. Therefore, the STTD and QPSK 3/4 pairs are also selected by the MIMO mode and MCS level pair selector 404 as entries of the candidate group. The same applies to the ECINR 912 when the MIMO mode is STTD and the MCS level is 16QAM 3/4.

However, when the MIMO mode of the received signal is STTD and the MCS level is 64QAM 2/3, 64QAM 3/4, 64QAM 5/6, the EINCRs 914, 916 and 918 are located to the left of the second threshold on the graph of FIG. Is less than the second threshold. Thus, the MIMO mode and MCS level pairs are not selected as first MIMO mode and MCS level pairs as candidate groups.

In one embodiment, the selector 404 pre-stores the numerical information of the second threshold for each MCS level when the target BLER of the first threshold is to be satisfied, and compares with the previously stored numerical information when receiving the ECINR You can output the result.

FIG. 10 is a diagram illustrating ECINR, MCS rate, STC rate, and second threshold determined for each MIMO mode and MCS level used by a 2x2 MIMO system according to an embodiment of the present invention.

Referring to FIG. 10, as described in FIG. 9, the MIMO mode is STTD, and the MCS level is QPSK 1/2, QPSK 3/4, 16QAM 1/2, 16QAM 3/4, 64 QAM 1/2, and 64QAM 2. If / 3, ECINR is greater than the second threshold, and the pair becomes the first MIMO mode and MCS level pair.

Then, when the MIMO mode is SM and the MCS level is QPSK 1/2 and QPSK 3/4, the corresponding pair becomes the first MIMO mode and MCS level pair. In addition, when the MIMO mode is SIMO and the MCS level is QPSK 1/2, QPSK 3/4, and 16QAM 1/2, the corresponding pair becomes the first MIMO mode and MCS level pair.

Meanwhile, MCS rate (Modulation and Coding Scheme Rate) shown in FIG. 10 means a ratio of actual data bits of a channel coded symbol according to MCS level. For example, for the MCS level of 64QAM 3/4, 9 bits of actual data are channel coded so that a signal of 12 bits in total is transmitted as two symbols. At this time, since the actual data bits per symbol are 9/2 bits, the MCS rate is 4.5.

In addition, STC rate (Space Time Coding Rate) shown in Figure 10 refers to the transmission gain according to the space-time transmission of the MIMO system, and in the case of the SM to transmit different data using two transmit antennas, STC rate is shown Becomes 2 as In the case of SIMO, a single transmit antenna is used, and in the case of STTD, two transmit antennas are used, but the STC rate is 1 because the same data is transmitted with a time difference.

Referring again to FIG. 4, the MIMO mode and MCS level determiner 406 obtains a first MIMO mode and MCS level pair, which is a candidate group, from the MIMO mode and MCS level pair selector 404, wherein each pair is obtained. The transmission scheme of the MIMO system is determined by the selected second MIMO mode and MCS level pair according to the transmission rate of. Hereinafter, operations of the MIMO mode and the MCS level determiner 406 will be described in detail with reference to FIGS. 10 and 11.

11 is a block diagram schematically illustrating a MIMO mode and an MCS level determiner 406 according to an embodiment of the present invention. The MIMO mode and MCS level determiner 406 includes a rate calculator 1102 and a rate comparison determiner. 1104.

The rate calculator 1102 calculates a rate of the first MIMO mode and MCS level pair received from the MIMO mode and MCS level pair selector 404.

The rate calculator 1102 calculates a data rate (throughput) by an operation corresponding to Equation 5 below.

Transmission rate = MCS rate × STC rate

In a modified embodiment, the rate calculator 1102 may calculate the rate by an operation corresponding to Equation 6 below.

Transmission rate = MCS rate × STC rate × (1-PER)

Referring to FIG. 10, the calculated transmission rate according to an embodiment of the present invention, in the case of the SM and QPSK 1/2 pairs among the candidate groups selected by the MIMO mode and the MCS level pair selector 404, the MCS rate is 1. Since the STC rate is 2, the transmission rate is 2. In the STTD and 16QAM 3/4 pairs, the MCS rate is 3 and the STC rate is 1, so the transmission rate is 3.

The rate comparison determining unit 1104 selects the second MIMO mode and MCS level pair having the largest transmission rate among the first MIMO mode and the MCS level pair as a result of the calculation of the rate calculating unit 1102, and selects the selected second MIMO. The transmission scheme of the MIMO system is determined by the mode and the MCS level pair.

Referring to FIG. 10, among the first MIMO mode and MCS level pairs, the STTD and 16QAM 3/4 pairs, the STTD and 64QAM 1/2 pairs, and the SM and QPSK 3/4 pairs have the largest transmission rates as 3 in the above-described method. Has a data rate. Accordingly, the rate comparison determining unit 1104 selects the three pairs as the second MIMO mode and MCS level pair.

However, when the second MIMO mode and MCS level pairs having the largest data rates are plural as described above, the rate comparison determining unit 1104 reduces the error rate among the plurality of second MIMO mode and MCS level pairs. A second MIMO mode and MCS level pair with ECINR is selected to determine the transmission scheme of the MIMO system.

In one embodiment, a method of selecting a second MIMO mode and MCS level pair having an ECINR that reduces an error rate among a plurality of second MIMO mode and MCS level pairs is a reference value for a target error rate (1% BLER or less). The difference between the second threshold and the ECINR of the second MIMO mode and MCS level pair is compared to select the second MIMO mode and MCS level pair with the largest difference.

For example, referring to FIG. 10, the difference between the second threshold and the ECINR is 0.2 dB (= 11.3 dB-11.1 dB) for the STTD and 16QAM 3/4 pairs, and the difference is 0.1 dB for the STTD and 64QAM 1/2 pairs. = 11.9dB-11.8dB), and for the SM and QPSK 3/4 pairs the difference is 0.6dB (= 5.5dB-4.9dB). Accordingly, the rate comparison determining unit 1104 finally selects a SM and QPSK 3/4 pair having the largest difference between the second threshold and the ECINR, and determines the transmission scheme of the MIMO system.

Referring back to FIG. 4, the feedback unit 408 transmits a feedback message including information on the second MIMO mode and MCS level pair determined by the MIMO mode and the MCS level determination unit 406 as a transmission method of the MIMO system. Send to 200. For example, according to the result shown in FIG. 10, the transmitter 200 feeds back the use of SM as the MIMO mode and QPSK 3/4 as the MCS level as the transmission scheme.

12 is a flowchart illustrating a method of determining a transmission method of a MIMO system according to an embodiment of the present invention.

First, upon receiving a signal from a transmitter of a MIMO system, a plurality of PCINRs are calculated according to a predetermined MIMO mode among the MIMO modes used by the MIMO system (S1202).

Next, a plurality of channel capacities mapped to the plurality of PCINRs are obtained by a mapping table of channel capacities according to modulation schemes used by a plurality of PCINRs and a MIMO system (S1204).

Next, a plurality of channel capacities mapped to the plurality of PCINRs is obtained by using a mapping table of a plurality of PCINRs and channel capacities according to the modulation scheme (S1204).

In one embodiment, the channel capacity may be a channel capacity function value based on the AWGN channel model according to the modulation scheme.

Next, a cumulative average of the plurality of channel capacities is calculated (S1206).

Next, the PCINR mapped to the cumulative average is determined by the mapping table as the ECINR for the predetermined MIMO mode (S1208).

In one embodiment, the mapping of the plurality of PCINRs or the cumulative average may be performed using weights for correction of the plurality of PCINRs.

Next, if ECINR is not determined for all MIMO modes and modulation schemes used by the MIMO system (S1210), steps S1202, S1204, and S1206 until ECINR is determined for all MIMO modes and modulation schemes used by the MIMO system. Step and step S1208 are repeatedly performed.

If ECINR is determined for all MIMO modes and modulation schemes (S1210), the ECNRR is compared with an SNR threshold that satisfies the target error rate condition for each MIMO mode and MCS level (S1212).

In one embodiment, the MIMO mode used by the MIMO system may include at least one of SIMO, STTD, and SM.

In one embodiment, the error rate may be any one of BLER, PER, and FER.

Next, as a result of the comparison, a MIMO mode and MCS level pair having an ECINR that is equal to or higher than an SNR threshold is selected as the first MIMO mode and MCS level pair (S1214).

Next, among the first MIMO mode and the MCS level pair, the MIMO mode and the MCS level pair having the largest transmission rate are selected as the second MIMO mode and the MCS level pair (S1216).

In one embodiment, the transmission rate may be determined by multiplying the MCS rate according to the MCS level and the STC rate according to the MIMO mode.

Next, if there are a plurality of second MIMO mode and MCS level pairs (S1218), the transmission scheme of the MIMO system is determined by the MIMO mode and MCS level pair having the ECINR having the lowest error rate (S1220). In operation S1222, feedback is performed by transmitting a feedback message including a MIMO mode and an MCS level determined as a transmission method to a transmitter of the MIMO system.

If the second MIMO mode and the MCS level pair are not plural (S1218), the transmission method of the MIMO system is determined by the second MIMO mode and the MCS level pair (S1224), and includes the MIMO mode and the MCS level determined as the transmission method. The feedback is performed by transmitting the feedback message to the transmitter of the MIMO system (S1222).

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features.

Therefore, it is to be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining the outline | summary of a SISO system and a MIMO system.

2 is a block diagram illustrating a transmitter of an N × M MIMO system according to an embodiment of the present invention.

3 is a block diagram illustrating a receiver of an N × M MIMO system according to an embodiment of the present invention.

4 is a block diagram showing a transmission method determination unit according to an embodiment of the present invention.

5 is a block diagram illustrating an effective CINR determination unit according to an embodiment of the present invention.

6 is a block diagram illustrating a concept of an operation of an effective CINR mapping unit according to an embodiment of the present invention;

7 is a graph of channel capacity function according to modulation scheme in a MIMO system according to an embodiment of the present invention.

8 is a block diagram illustrating a MIMO mode and MCS level pair selector according to an embodiment of the present invention.

9 is a view for explaining an operation of comparing the ECINR and the second threshold value according to the error rate according to an embodiment of the present invention.

FIG. 10 is a view illustrating ECINR, MCS rate, STC rate, and second threshold determined for each MIMO mode and MCS level used by a 2 × 2 MIMO system according to an embodiment of the present invention. FIG.

11 is a block diagram schematically illustrating a MIMO mode and an MCS level determiner according to an embodiment of the present invention.

12 is a flowchart illustrating a method of determining a transmission method of a MIMO system according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

360: transmission method determination unit 402: effective CINR determination unit

404: MIMO mode and MCS level pair selector

406: MIMO mode and MCS level determiner

408: feedback unit

Claims (25)

In the transmission method of the MIMO (multi-input and output) system to which at least one MIMO mode is applied, (a) determining an effective CINR (Effective CINR) of a received signal for each MIMO mode and modulation scheme applied to the MIMO system; (b) selecting a first MIMO mode and MCS level pair consisting of a MIMO mode and an MCS level according to the effective CINR among the MIMO mode and the modulation and coding scheme (MCS) level of the modulation scheme; And (c) determining a transmission scheme of the MIMO system based on a second MIMO mode and an MCS level pair selected according to a data rate of the first MIMO mode and an MCS level pair among the first MIMO mode and an MCS level pair; step; Method of determining the transmission method of the MIMO system, characterized in that it comprises a. The method of claim 1, wherein step (a) comprises: (a-1) calculating a physical CINR from the received signal according to a predetermined MIMO mode of the MIMO mode; (a-2) determining an effective CINR for the predetermined MIMO mode for each modulation scheme by using the mapping table of the channel capacity according to the physical CINR and the modulation scheme; And (a-3) determining the effective CINR for each MIMO mode and modulation method by repeatedly performing steps (a-1) and (a-2) for a MIMO mode other than the predetermined MIMO mode; Method of determining the transmission method of the MIMO system, characterized in that it comprises a. The method of claim 2, wherein (a-2) comprises: Obtaining at least one channel capacity mapped to at least one physical CINR by the mapping table; Calculating a cumulative average for the channel capacity; And Determining a physical CINR mapped to the cumulative average by the mapping table as an effective CINR for the predetermined MIMO mode; Method of determining the transmission method of the MIMO system, characterized in that it comprises a. The method of claim 3, wherein the mapping to the plurality of physical CINRs or cumulative averages, Method of determining the transmission method of the MIMO system, characterized in that performed using the weight for the correction of the mapping result. The method of claim 2, wherein the channel capacity, And a channel capacity function based on an additive white gaussian noise (AWGN) channel model according to the modulation scheme. According to claim 1, wherein step (b), Comparing the effective CINR with a second threshold for a Signal to Noise Ratio (SNR) that satisfies a condition that an error rate is less than a first threshold for each MIMO mode and MCS level; And Selecting, as the first MIMO mode and MCS level pair, the MIMO mode and MCS level pair having an effective CINR greater than or equal to the second threshold as a result of the comparison; Method of determining the transmission method of the MIMO system, characterized in that it comprises a. The method of claim 1, wherein step (c) comprises: Calculating a transmission rate of the first MIMO mode and MCS level pair; And Determining a transmission scheme of the MIMO system by the second MIMO mode and MCS level pair having an effective CINR that has the smallest transmission rate and the lowest error rate among the first MIMO mode and MCS level pair; Method of determining the transmission method of the MIMO system, characterized in that it comprises a. In the method of determining the transmission method of the MIMO system to be performed in the receiver for feedback to the transmitter in a MIMO system each of the transmitter and the receiver using at least one antenna, Determining an effective CINR of a received signal for each MIMO mode and modulation scheme applied to the MIMO system; And A first MIMO mode and an MCS level pair consisting of a MIMO mode and an MCS level are selected from the MIMO mode and the MCS level of the modulation scheme using the effective CINR, and the MIMO is selected by the selected first MIMO mode and MCS level pair. Determining a transmission scheme of the system; Method of determining the transmission method of the MIMO system, characterized in that it comprises a. The method of claim 8, wherein the determination of the effective CINR, And determining the effective CINR using a mapping table of physical CINR and channel capacity of a received signal for each MIMO mode and modulation method. The method of claim 8, wherein determining the effective CINR comprises: Obtaining a channel capacity mapped to the physical CINR by a mapping table of physical CINRs and channel capacity of the received signal; Calculating a cumulative average for the channel capacity; And Determining a physical CINR mapped to the cumulative mean by the mapping table as the effective CINR; Method of determining the transmission method of the MIMO system, characterized in that it comprises a. The method of claim 9, wherein the channel capacity is: And a channel capacity function based on the AWGN channel model according to the modulation scheme. The method of claim 8, wherein the first MIMO mode and MCS level pair, A second MIMO mode and an MCS level pair having an effective CINR for causing an error rate of the received signal to be less than or equal to a first threshold, selected according to a transmission rate corresponding to the second MIMO mode and an MCS level pair and an error rate of an effective CINR; A transmission method determination method of a MIMO system. The method of claim 12, wherein the transmission rate, The transmission method of the MIMO system, characterized in that determined by the product of the MCS rate (MCS Rate) according to the MCS level and the STC rate (Space Time Coding Rate) according to the MIMO mode. The method of claim 8, The MIMO mode includes at least one of a Single Input Multi Output (SIMO), Space Time Transmit Diversity (STTD), and Spatial Multiplexing (SM). The method of claim 12, The error rate is any one of a block error rate (BLER), a packet error rate (PER) and a frame error rate (FER). In a MIMO (multiple input / output) system to which at least one MIMO mode is applied, An effective CINR determination unit for determining an effective CINR of a received signal for each MIMO mode and modulation scheme applied to the MIMO system; A MIMO mode and MCS level pair selector for selecting a first MIMO mode and an MCS level pair consisting of a MIMO mode and an MCS level according to the effective CINR among the MIMO mode and the MCS level of the modulation scheme; And A MIMO mode and MCS level determiner configured to determine a transmission method of a MIMO system based on a second MIMO mode and an MCS level pair selected according to a transmission rate of the first MIMO mode and an MCS level pair among the first MIMO mode and an MCS level pair; Apparatus for determining a transmission method of a MIMO system, characterized in that it comprises a. The method of claim 16, wherein the effective CINR determination unit, A physical CINR calculator configured to calculate at least one physical CINR according to the MIMO mode from the received signal; And  An effective CINR mapping unit for determining an effective CINR of the received signal by using a mapping table of channel capacities according to the physical CINR and the modulation scheme; Apparatus for determining a transmission method of a MIMO system, characterized in that it comprises a. The method of claim 17, wherein the effective CINR mapping unit, A cumulative average calculator configured to obtain at least one channel capacity mapped to the physical CINR by the mapping table, and calculate a cumulative average of the channel capacity; And A cumulative average mapping unit configured to determine a physical CINR mapped to the cumulative average as an effective CINR of the received signal; Apparatus for determining a transmission method of a MIMO system, characterized in that it comprises a. The method of claim 18, wherein the effective CINR mapping unit, The apparatus for determining a transmission method of a MIMO system, characterized in that the mapping is performed on the physical CINR or the cumulative average using weights for correction of a mapping result. The method of claim 17, wherein the channel capacity, And a channel capacity function based on the AWGN channel model according to the modulation scheme. The method of claim 16, wherein the MIMO mode and MCS level pair selector, A comparison unit comparing the effective CINR with a second threshold for an SNR satisfying a condition in which an error rate is equal to or less than a first threshold for each MIMO mode and MCS level; And A selection unit that selects the MIMO mode and MCS level pair having an effective CINR that is greater than or equal to the second threshold as a first MIMO mode and MCS level pair as a result of the comparison; Apparatus for determining a transmission method of a MIMO system, characterized in that it comprises a. The method of claim 21, And the error rate is any one of a BLER, a PER, and a FER. The method of claim 16, wherein the MIMO mode and MCS level determiner, A rate calculator for calculating a rate of the first MIMO mode and MCS level pair; And As a result of the calculation of the rate calculator, the transmission scheme of the MIMO system is determined by the second MIMO mode and MCS level pair having the effective CINR having the largest transmission rate and the lowest error rate among the first MIMO mode and MCS level pairs. A rate comparison determining unit; Apparatus for determining a transmission method of a MIMO system, characterized in that it comprises a. The method of claim 23, wherein the MIMO mode and MCS level determiner, And determining the transmission rate by a product of an MCS rate according to the MCS level and an STC rate according to the MIMO mode. The method of claim 16, And the MIMO mode includes at least one of SIMO, STTD, and SM.

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