KR101576141B1 - Apparatus and method for transmission mode decision in mobile communication system - Google Patents

Abstract

A method for determining a transmission scheme of a mobile station in a mobile communication system is provided. The method includes calculating an estimate of correlation between a plurality of antennas, calculating a channel variation estimation value, calculating an SINR (Signal to Interference plus Noise Ratio) estimation value, And determining a Modulation and Coding Selection (MCS) level based on the estimated correlation value, the channel variation estimated value, and the SINR estimated value.

AMC, SIR, SINR, MCS level.

Description

[0001] APPARATUS AND METHOD FOR TRANSMISSION MODE DECISION IN MOBILE COMMUNICATION SYSTEM [0002]

The present invention is not limited to the conventional received signal-to-noise ratio (SNR) for adaptive modulation and coding (AMC), which is effective in a MIMO OFDM (Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing) Ratio) and SIR (Signal-to-Interference Ratio) information, and additionally selects a transmission mode using additional terminal status information (terminal speed, current speed of the terminal, correlation of MIMO channels, etc.) And methods.

Since the state of the wireless channel continuously changes with time due to the position of the terminal, the path loss and the fading characteristic of the signal, a link adaptation technique is required for efficient data transmission through the wireless link.

Generally, a typical link adaptation scheme is a power control scheme. The power control scheme is a technique for maintaining the transmission quality by controlling the power according to the radio link, and is an efficient system for ensuring the quality of the link in a fixed transmission rate situation such as voice.

On the other hand, multimedia data requires various transmission rates and various transmission qualities according to service types, and therefore, a link adaptation technique that is different from conventional voice-based service provision is required.

The Adaptive Modulation and Coding (AMC) scheme is an adaptive adaptive scheme that is an efficient link adaptation scheme for such data transmission and changes the transmission rate, not the transmission power, according to the channel environment.

In the case of power control, the transmission power is changed according to the channel to obtain a fixed target signal-to-noise ratio (SNR). However, since the AMC determines and transmits an appropriate transmission rate according to the characteristics of the channel, the transmission power is basically fixed.

At this time, the transmission rate is determined by the Modulation and Coding Selection (MCS) level, which is a level for a predefined combination of modulation and channel coding. In the most basic manner, the MCS level is determined according to the received SNR, and a level showing the most optimal efficiency is selected according to this SNR information.

However, there is a limit to determine the MCS level using only such received SNR. For example, in a MIMO-OFDM system, multiple streams may not be transmitted even if the SNR is high due to correlation between antennas. Therefore, inter-antenna correlation is also required to select the MCS level.

Even in the same SNR situation, the MCS level selected by the moving speed of the terminal can be changed. In case of high speed, the system may select the MCS level under the diversity subchannel in order to maximize the diversity effect, and may provide additional performance enhancement functions such as CL-MIMO using the band-AMC subchannel in the case of low speed . Therefore, speed can also be an important factor in selecting the MCS level. In addition, the degree of interference generated by other users may also be a criterion for selection of the MCS level.

Therefore, for effective AMC in the MIMO OFDM system, the received SINR and SIR information are needed instead of the existing received SNR. In addition, additional terminal state information (terminal speed, current speed of the terminal, correlation of MIMO channel, etc.) There is a need for an apparatus and a method for determining the MCS level using the MCS level.

It is an object of the present invention to provide an apparatus and method for determining a transmission scheme in a mobile communication system.

It is another object of the present invention to provide a method and apparatus for measuring AMC mode (diversity / Band-AMC) of a UE and AMC mode (Band-AMC) of a UE by measuring state information (SINR, SIR, current rate of a UE, correlation of a MIMO channel, And an apparatus and method for determining an MCS level (number of transmission MIMO streams and modulation order, code rate, etc.).

According to a first aspect of the present invention, there is provided a method for determining a transmission scheme of a mobile station in a mobile communication system, the method comprising: calculating an estimated correlation value between a plurality of antennas; Calculating a channel variation estimation value, calculating a SINR (Signal to Interference plus Noise Ratio) estimation value, and calculating an estimated correlation value, a channel variation estimation value, and a SINR estimation value of the plurality of antennas And determining a Modulation and Coding Selection (MCS) level based on the MCS.

According to a second aspect of the present invention, there is provided an apparatus comprising an antenna channel correlation estimator for calculating an estimate of correlation between a plurality of antennas, a channel variation estimator for calculating a channel variation estimation value, An SNIR estimator for calculating an SINR estimation value and an MCS level selector for determining an MCS level based on correlation estimates, channel variation estimation values and SINR estimation values between the plurality of antennas, do.

The present invention measures a mode (diversity / band-AMC) of a UE and a predetermined MCS level (a transmission MIMO level) of a UE by measuring state information of the UE (SINR, SIR, current rate of the UE, correlation between MIMO channels) Stream number, modulation order, and code rate), which is an effective AMC.

Particularly, the velocity measurement method used in the present invention has an advantage of improving the performance of the system through various practical applications.

When the present invention is applied to the adaptive transmission / reception technique, the speed information of the terminal enables more efficient channel estimation in the receiver, and the modulation, coding, or interleaving technique in the transmitter can be adjusted according to the channel state.

In addition, when the present invention is used in an algorithm on the network side, the handoff decision process can be accurately performed and resource allocation of the system can be efficiently managed.

In addition, the present invention has an advantage in that an optimal MIMO transmission mode (beamforming, SDMA, transmit diversity, and spatial multiplexing) can be selected according to the degree of correlation in the case of the inter-antenna correlation measurement method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, an apparatus and method for determining a transmission scheme in a mobile communication system will be described.

1 is a diagram illustrating a mode and an MCS level selection criterion of a UE according to an embodiment of the present invention.

Referring to FIG. 1, a mode of a terminal is operated in two modes of a band AMC and a diversity subchannel. The SINR, the SIR, the current rate of the terminal, and the detailed MCS level .

2 is a diagram illustrating a mode selection process of a UE according to an embodiment of the present invention.

Referring to FIG. 2, a UE receives a result of a channel variation estimator (V_Metric, V_type) and a SINR estimator (a full-band SINR, a band-specific SINR, SIR) as input.

If V_Metric <V_Th1, the SINR for each band of the upper 5 bands> the full band SINR, the V_type = 0, and the SIR> IC_Th (step 210), it is determined that the current terminal requests a band AMC subchannel Step 220), otherwise, it is determined to request the diversity subchannel (step 230). That is, if a communication channel environment is good, a band AMC subchannel is requested and used, and when a communication channel environment is relatively poor, a diversity subchannel is requested and used.

3 is a diagram illustrating an MCS level occurrence period of a UE according to an embodiment of the present invention.

Referring to FIG. 3, after the AMC mode is determined, the UE further receives a result value (Tx and Rx MIMO correlation value) of the MIMO channel correlation estimator and determines the MCS level of the UE every Tm1 period.

The generation periods of the various inputs for selecting the MCS may be different from each other as Tv1, Tv2, Ts1, and Tc1, respectively, but the period Tm1 for determining the MCS level is set to their least common multiple as shown in the following equation.

That is, the MCS level is calculated by multiplying the estimated value of the channel variation estimator (Speed estimator), the result value of the SINR estimator (full-range SINR, SINR, SIR of each band of the upper 5 bands), and the result value of the correlation estimator (Tx and Rx MIMO correlation Value) to determine the MCS level. The detailed determination process will be described below.

4 is a diagram illustrating an MCS level selection process of a UE according to an embodiment of the present invention. Here, the MCS level selection period is Tm1.

Referring to FIG. 4, an overall flow of an MCS level selection process for a UE is illustrated. First, an MCS level selection process in the band AMC mode for data is as follows. That is, if the AMC mode of the terminal is determined to be the band AMC mode (step 410), if the current frame type is the IC frame (step 415), the MCS level 3 is selected (step 475).

If the current frame type is an NM frame (step 415), the UE receives Corr _tx ² and corr _rx ² values of the MIMO channel correlation estimator in step 455 and compares it with the threshold values Th_tx1_B, Th_tx2_B and Th_rx_B, The table is selected (step 460). The criteria for selection are shown in Table 1 below.

Corr _tx ² <Th_tx1_B Th_tx1 <Corr _tx ² <Th_tx2_B Corr _tx ² > Th_tx2_B Corr _tx ² <Th_rx_B MCS table (B_1) MCS table (B_2) MCS table (B_3) Corr _tx ² > Th_rx_B MCS table (B_4) MCS table (B_5) MCS table (B_6)

Thereafter, the SINR estimator receives the band-specific SINR estimation values of the upper 5 bands from the SINR estimator in step 465, and selects the MCS level for each band using the selected MCS table in step 470.

The diversity subchannel MCS level selection process for the MAP information is as follows.

If the current frame type is an IC frame (step 415), MCS level 3 is selected (step 475).

If the current frame type is the NM frame in step 415, the terminal estimates the full-band SINR in step 420 and if the SINR value of the full-band is SINR> T_SINR3 (step 425), Corr _tx ² of the MIMO channel correlation estimator And corr _rx ² are input in step 440 and compared with the threshold values Th_tx1_D, Th_tx2_D and Th_rx_D to select an MCS table in step 445.

Corr _tx ² < Th_tx1_D Th_tx1 <Corr _tx ² <Th_tx2_D Corr _tx ² > Th_tx2_D Corr _tx ² <Th_rx_D MCS table (D_1) MCS table (D_2) MCS table (D_3) Corr _tx ² > Th_rx_D MCS table (D_4) MCS table (D_5) MCS table (D_6)

Thereafter, a full-band SINR estimation value is input from the SINR estimator and an MCS level for Div. Is selected through a selected MCS table in operation 450.

if. If the SINR value of the entire area is not SINR> T_SINR3 (step 425), the SINR_corr is calculated (step 430), and the MCS level is selected according to the MCS table [7] based on the calculated SINR_corr (step 435).

Now, the MCS level selection process in the diversity subchannel mode (step 410) is as follows.

If not SIR> IC_Th (step 480), the IC MCS table [9] is selected and compared with the SINR_IC to select the IC MCS level (step 498).

If SIR> IC_Th (step 480), it is determined whether the current frame type is an IC frame, and if it is an IC frame (step 485), MCS level 3 is selected (step 475).

If the current frame type is the NM frame (step 485) and V_metric> V_Th2 (step 490), the MCS level 7 is selected (step 492).

If V_metric> V_Th2 is not satisfied (step 490), SINR_corr is calculated (step 494) and the MCS level is selected from the MCS table selected based on the calculated SINR_corr (step 496). An example of the MCS table used in FIG. 4 is shown in FIG.

Now, the channel variation estimator (Speed Estimator) of the present invention will be described as follows.

The UE obtains the power value of the difference between the preamble reception signal power value of the current frame and the next preamble reception signal which is separated by N _gap interval and accumulates the power value by a total of N _frm -1 frames to estimate the channel variation value.

To estimate the amount of change in the channel, the terminal uses a frequency domain approach. In estimating the amount of change in the channel, the estimated amount of change in the channel is different even though the amount of change in the same channel value according to the degree of interference and noise added to the received signal.

In order to eliminate this influence, the interference and noise power are estimated, and the correction is performed so that the channel variation estimation value is independent of the degree of interference and noise. In the case where the power control is not performed, the magnitude of the received signal differs according to the position of the terminal, and thus the scaler performs the channel normalization process to correct the channel value variation. The method for obtaining the channel estimation variation is as follows.

Assuming that the _k &lt; _th &gt; extracted subcarrier reception signal in the preamble reception signal of the n &lt; th &gt; frame of the serving cell is rk (n)

Where h _k (n) is n sub-carriers extracted by a k-th in the preamble reception signal of the second frame channels, p _k is assigned to sub-carriers extracted by a k-th in the preamble reception signal of the serving cell value, i _k (n ) and n _k (n) represent the interference and noise corresponding to the subcarrier extracted at the k-th time in the preamble received signal of the n-th frame, respectively.

At this time, the channel change amount estimation value is expressed by the following equation.

이다.here

to be.

The UE calculates the power value of the difference between the preamble reception signal power value of the current frame and the next preamble reception signal that is separated by the N _gap interval in accordance with the preamble sequence of the serving cell and accumulates the power value as a total of N _frm -1 frames, Estimate the value.

The channel variation estimator is divided into a high speed / low speed estimator according to the set values of N _gap and N _frm .

5 is a diagram illustrating a configuration of a channel variation amount estimation (velocity estimation) convex according to an embodiment of the present invention.

5, the channel variation estimation block includes an accumulation and metric calculator (High Speed) 510 for high speed, an accumulation and metric calculator for low speed, Low Speed) 520, a controller 515, and a metric decision unit 525. [

The accumulation and metric arithmetic unit 510 for high speed outputs a channel estimation value in a fast mode in which the terminal moves at high speed. The channel estimation procedure is shown in Equation (3).

The accumulation and metric arithmetic unit 520 for low speed outputs a channel estimation value in a low speed mode in which the terminal moves at a low speed. The channel estimation procedure is shown in Equation (3).

The UE calculates the power value of the difference between the preamble reception signal power value of the current frame and the next preamble reception signal that is separated by the N _gap interval in accordance with the preamble sequence of the serving cell and accumulates the power value as a total of N _frm -1 frames, Estimate the value.

Here, P _r is the power value of the preamble received signal power of the current frame, P _d is the power value of the difference from the next preamble received signal after being separated by the N _gap interval, IN ' _avg is the accumulated power value of the preamble received signal to be.

The control unit 515 receives the values P _r , P _d , and IN ' _avg , and outputs the values received at predetermined intervals to the accumulation and metric calculator 520 for the low speed.

The metric determination unit 525 receives the channel estimation value in the high speed mode and the channel estimation value in the low speed mode, and when the channel estimation value in the high speed mode is greater than the threshold value, And determines it as the channel estimation value of the terminal.

6A is a flowchart illustrating an operation of a controller among a channel variation amount estimation (rate estimation) block according to an embodiment of the present invention.

Referring to FIG. 6A, the controller initializes the index (idx) value to 0 (step 610), receives the values of P _r , P _d and IN ' _avg (step 615) , Step 630).

In step 620 and step 630, m is a predetermined constant. When the idx value increases (step 630) and the remainder obtained by dividing the m value and the idx value becomes 0 (step 620 ), And outputs the input P _r , P _d , and IN ' _avg values (Step 625)

FIG. 6B is a flowchart illustrating an operation of a matrix determination unit among channel variation amount estimation (velocity estimation) blocks according to an embodiment of the present invention.

Referring to FIG. 6B, the matrix determination unit receives the channel estimation values from the accumulation and metric operation unit for high speed and the accumulation and metric operation unit for low speed, respectively (operation 635).

Thereafter, if the channel estimation value in the fast mode is greater than the threshold value (step 640), the channel estimation value in the fast mode is determined as the channel estimation value of the terminal. Then, the type of the terminal (high speed type) is determined. Here, it is a case that V_Type = 1 (step 645).

If the channel estimation value in the high-speed mode is smaller than the threshold value, the channel estimation value in the low-speed mode is determined as the channel estimation value of the terminal. Then, the type of the terminal (low speed type) is determined. Here, it is a case that V_Type = 0 (step 650).

7 is a diagram illustrating a MIMO channel correlation estimator according to an embodiment of the present invention.

Referring to FIG. 7, the UE receives a frequency-domain preamble channel estimation value for each antenna of a serving cell,

The Correlation Estimation Block 730 estimates Tx and Rx antenna correlation from a 4x4 channel H (n, k) matrix at the k th extracted subcarrier of the nth frame. The estimation interval may be as much as N _subcr and N _frm accumulated in the accumulation block 720.

In the Tx antenna correlation measurement method, a 4x4 channel matrix H (n, k) at the k-th subcarrier of the n-th frame can be expressed by the following equation.

Here, h _{i, j} ^tx (n, k) denotes a channel gain from the j th tx antenna to the i th rx antenna in the k th acquired subcarrier of the n th frame. In this case, the Tx antenna correlation can be obtained by the following equations.

In the Rx antenna correlation measurement scheme, a 4x4 channel matrix H ⁽ⁿ⁾ (k) at the k-th acquired subcarrier of the n-th frame can be expressed by the following equation.

In this case, the Rx antenna correlation is expressed by the following equations.

In the above-described block configuration, although not shown, the control unit may perform the functions of the functional modules 510, 520, and 530 of FIG. 6 and the functional modules 720 and 730 of FIG. In the present invention, these are separately constructed and described in order to describe each function separately.

Accordingly, when the product is actually implemented, the control unit may process all the functions of the functional modules, and the control unit may process only a part of the functions.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

1 is a diagram illustrating a mode and an MCS level selection criterion of a UE according to an embodiment of the present invention;

2 is a diagram illustrating a mode selection process of a UE according to an embodiment of the present invention;

3 is a diagram illustrating an MCS level occurrence period of a UE according to an embodiment of the present invention;

4 is a diagram illustrating a process of selecting an MCS level of a UE according to an embodiment of the present invention;

5 is a diagram showing a configuration of a channel variation amount estimation (velocity estimation) convex according to an embodiment of the present invention,

FIG. 6A is a flowchart illustrating an operation of a controller among a channel change amount estimation (rate estimation) block according to an embodiment of the present invention; FIG.

FIG. 6B is a flowchart illustrating an operation of a matrix determination unit in a channel variation amount estimation (velocity estimation) block according to an embodiment of the present invention;

7 is a diagram illustrating a MIMO channel correlation estimator according to an embodiment of the present invention.

FIG. 8A is a block diagram of an MCS table according to an embodiment of the present invention.

FIG. 8B is a block diagram of the MCS table according to the embodiment of the present invention,

FIG. 8C is a block diagram of an MCS table according to an embodiment of the present invention,

FIG. 8D is a view showing the MCS table according to an embodiment of the present invention, and FIG.

FIG. 8E is a block diagram of an MCS table according to an embodiment of the present invention; FIG.

Claims (10)

A method for determining a transmission scheme of a mobile station in a mobile communication system, Calculating an estimated correlation value between the plurality of antennas; Calculating a channel change amount estimation value, Obtaining an SINR estimate using a SINR (Signal to Interference plus Noise Ratio) estimator; And determining an MCS (Modulation and Coding Selection) level based on the estimated correlation value, the channel variation estimated value, and the SINR estimated value. The method according to claim 1, The process of determining the MCS level comprises: And using the band AMC channel and the diversity subchannel according to whether the predetermined condition is satisfied based on the channel change amount estimation value and the SINR estimation value. 3. The method of claim 2, The process of determining the MCS level comprises: And determining an MCS level by comparing an estimated value of correlation between the plurality of antennas with at least one threshold when determining to use the band AMC channel. The method of claim 3, The process of determining the MCS level comprises: And determining an MCS level every predetermined period. The method according to claim 1, Wherein the step of calculating the channel change amount estimation value comprises: Determining a channel change amount estimation value in the fast mode as the channel change amount estimation value when the estimated channel change amount in the fast mode is larger than the threshold value of the channel change amount; And determining the channel variation estimation value in the low-speed mode as the channel variation estimation value when the channel variation estimation value in the high-speed mode is smaller than the threshold value. An apparatus for determining a transmission scheme of a mobile station in a mobile communication system, An antenna channel correlation estimator for calculating an estimate value of correlation between the plurality of antennas, A channel change amount estimator for calculating a channel change amount estimation value, A SINR estimator for calculating an SINR (Signal to Interference plus Noise Ratio) estimation value; And an MCS level selector for determining an MCS (Modulation and Coding Selection) level based on the estimated correlation value, the channel variation estimated value, and the SINR estimated value. The method according to claim 6, Wherein the MCS level selector determines use of a band AMC channel and a diversity subchannel according to whether a predetermined condition is satisfied based on the channel variation estimation value and the SINR estimation value. 8. The method of claim 7, Wherein the MCS level selector determines an MCS level by comparing an estimated value of correlation between a plurality of antennas with at least one threshold when determining to use the band AMC channel. 9. The method of claim 8, Wherein the MCS level selector determines an MCS level every predetermined period. The method according to claim 6, Wherein the channel change amount estimator comprises: When the channel change amount estimated value in the fast mode is larger than the threshold value of the channel change amount, the channel change amount estimated value in the fast mode is determined as the channel change amount estimated value, , The channel change amount estimation value in the low speed mode is determined as the channel change amount estimation value.

Images