KR20100092583A - Apparatus and method for transmission mode decision in mobile communication system - Google Patents

Abstract

PURPOSE: An apparatus and a method for deciding a transmission mode in a mobile communication system are provided to implement efficient AMC(Adaptive Modulation and Coding) by determining a predetermined MCS(Modulation and Coding Scheme) level of a terminal through the state information of the terminal. CONSTITUTION: An accumulation and metric calculation unit for high speed(510) outputs a channel estimation value at a high speed mode of a terminal, and an accumulation and metric calculation for low speed(520) outputs a channel estimation value at a low speed mode of the terminal. If the channel estimation value is larger than a critical value at the high speed mode, a metric decision unit(525) estimation the channel estimation value as the channel estimation value at the high speed mode.

Description

Apparatus and method for determining transmission method in mobile communication system {APPARATUS AND METHOD FOR TRANSMISSION MODE DECISION IN MOBILE COMMUNICATION SYSTEM}

The present invention is for receiving adaptive signal-to-noise ratio (SINR) rather than conventional received signal-to-noise ratio (AMNR) for effective AMC (Adaptive Modulation and Coding) in MIMO OFDM (Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing) systems. A device that selects a transmission method using ratio ratio and signal-to-interference ratio information, and additionally, additional terminal status information (terminal speed, terminal current speed, correlation of MIMO channel, etc.) And to a method.

Since the state of the radio channel is constantly changing with time due to the position of the terminal, the path loss of the signal and the fading characteristics, a link adaptation technique is required for efficient data transmission over the radio link.

In general, a typical link adaptation technique is a power control technique. The power control scheme maintains transmission quality by controlling power according to a wireless link. The power control scheme is an efficient method for ensuring a link quality in a fixed rate situation such as voice.

On the other hand, since multimedia data requires various transmission rates and various transmission quality depending on the type of service, a link adaptation technique having a different concept from that of a conventional voice-oriented service is required.

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

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

In this case, the transmission rate is determined by a modulation and coding selection (MCS) level, which is a level for a predefined modulation and channel coding combination. In the most basic manner, the MCS level is determined according to the received SNR, and the level having the most efficient efficiency is selected according to this SNR information.

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

In addition, even in the same SNR situation, the MCS level selected by the movement speed of the terminal may vary. At high speeds, the system can select the MCS level under the diversity subchannels to maximize the diversity effect. At low speeds, the Band-AMC subchannels can be used to provide additional performance enhancements such as CL-MIMO. . Thus, speed can also be an important factor in selecting the MCS level. In addition, the degree of interference from other users may also be a criterion for the selection of the MCS level.

Therefore, effective AMC in MIMO OFDM system requires received SINR and SIR information rather than conventional received SNR. In addition, additional UE status information (terminal speed, terminal current speed, correlation of MIMO channel, etc.) is used. There is a need for an apparatus and method for determining MCS levels using them.

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

Another object of the present invention is to measure the state information (SINR, SIR, the current speed of the terminal, the correlation of the MIMO channel, etc.) of the terminal and by using the AMC mode (diversity / Band-AMC) of the terminal and the predetermined terminal An apparatus and method for determining an MCS level (transmission MIMO stream number, Modulation Order, Code Rate, etc.) are provided.

According to a first aspect of the present invention for achieving the object of the present invention, the method for determining the transmission method of the terminal in the mobile communication system to calculate the estimated value of the antenna channel correlation and the channel variation estimation value Calculating a Signal to Interference plus Noise Ratio (SINR) estimate, and determining a Modulation and Coding Selection (MCS) level based on the estimated value of the antenna channel correlation, the estimated channel variation, and the estimated SINR. It characterized in that it comprises a process.

According to a second aspect of the present invention for achieving the object of the present invention, an antenna channel correlation estimator and channel variation estimation for calculating an estimated value of antenna channel correlation in a device for determining a transmission scheme of a terminal in a mobile communication system A channel variation estimator for calculating a value, an SNIR estimator for calculating an SINR estimation value, and an MCS level selector for determining an MCS level based on the estimated value of the antenna channel correlation, the channel variation estimation value, and the SINR estimation value; It features.

The present invention measures the state information (SINR, SIR, the current speed of the terminal, the correlation of the MIMO channel) of the terminal and by using the mode (diversity / Band-AMC) and the predetermined MCS level of the terminal (transmission MIMO) The number of streams, Modulation Order, Code Rate, etc.) can be used to provide effective AMC.

In particular, the speed 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 at the receiver, and there is an advantage that the modulation, coding, or interleaving technique can be adjusted according to the channel state at the transmitter.

In addition, the present invention has the advantage that it is possible to accurately perform the handoff decision process, and to efficiently manage the resource allocation of the system when used in the algorithm on the network side.

In addition, the present invention has the advantage of selecting the optimal MIMO transmission mode (beamforming, SDMA, transmit diversity, spatial multiplexing) according to the degree of correlation in the case of the mutual correlation measurement method between antennas.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

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 terminal according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a mode of a terminal is operated in two modes, Band AMC and diversity subchannel, and the detailed MCS level is changed according to the correlation of SINR, SIR, current speed of the terminal, and MIMO channel for each mode. Is determined.

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

Referring to FIG. 2, the terminal has a period of Tm1 and a result value (V_Metric, V_ type) of the channel variation estimator (Speed estimator) and the result value of the SINR estimator (full-band SINR, SINR for each band of the upper five bands, SIR) as an input.

If V_Metric <V_Th1, SINR> full-band SINR of the top five bands, V_type = 0, and SIR> IC_Th (step 210), the current UE determines to request a Band AMC subchannel (step 210). Otherwise, it is determined to request a diversity subchannel (step 230). That is, if the communication channel environment is good, the band AMC subchannel is requested and used, and if the communication channel environment is relatively poor, the diversity subchannel is requested and used.

3 is a diagram illustrating an MCS level generation period of a terminal according to an exemplary embodiment of the present invention.

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

The generation period of several inputs for MCS selection may be different from Tv1, Tv2, Ts1, and Tc1, respectively, but the period Tm1 for MCS level determination is determined by their least common multiple as shown in the following equation.

That is, the MCS level is the estimated value of the channel variation estimator (Speed estimator), the SINR estimator (full-band SINR, band-specific SINR, SIR) and the correlation estimator (Tx and Rx MIMO correlation). Value) to determine the MCS level. The detailed decision process will be explained below.

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

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

If the current frame type is an NM frame (step 415), the UE receives the Corr _tx ² and corr _rx ² values of the MIMO channel correlation estimator (step 455), and compares the threshold values (Th_tx1_B, Th_tx2_B, Th_rx_B) with the MCS. Select the table (step 460). The criteria for selecting 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)

Subsequently, the SINR estimation value of each of the upper five bands is received as an input from the SINR estimator (step 465), and an MCS level is selected for each band using the selected MCS table (step 470).

The diversity subchannel MCS level selection process for 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 an NM frame (step 415), the UE estimates the full-band SINR (step 420), and if the full-band SINR value is SINR> T_SINR3 (step 425), the Corr _tx ² of the MIMO channel correlation estimator And receiving a corr _rx ² value (step 440), and selecting an MCS table by comparing the threshold values (Th_tx1_D, Th_tx2_D, Th_rx_D) (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, the full-band SINR estimate is received from the SINR estimator, and the MCS level for Div. Is selected through the selected MCS table (step 450).

if. If the full-band SINR value is not a condition that 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 SIR> IC_Th (step 480), the IC MCS table [9] is selected, and the IC MCS level is selected in comparison with SINR_IC (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 the V_metric> V_Th2 (step 490) in the result value of the speed change estimator (step 490), MCS level 7 is selected (step 492).

If V_metric> V_Th2 (step 490), SINR_corr is calculated (step 494), and an MCS level is selected from the selected MCS table 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 estimator of the present invention will be described as follows.

The terminal obtains a power value of the difference between the preamble received signal power value of the current frame and the N _gap interval and then differs from the preamble received signal, and accumulates it by a total of N _frm −1 frames to estimate a change amount of the channel.

In order to estimate the amount of change in the channel, the terminal uses a frequency domain method. When estimating the change amount of the channel, even if the change amount of the same channel value according to the amount of interference and noise added to the received signal is different from the estimated change amount of the channel.

In order to remove this effect, interference and noise power are estimated and the channel variation estimate is corrected regardless of the interference and noise. If power control is not performed, the size of the received signal varies according to the position of the terminal, and therefore, Senggi performs a channel normalization process to correct the amount of change in the channel value. The method for obtaining the channel estimation variation is as follows.

If the k-th subcarrier reception signal extracted from the k-th preamble reception signal of the n-th frame of the serving cell is r _k (n), this can be expressed as the following equation.

Where h _k (n) is the k-th subcarrier channel extracted from the preamble received signal of the nth frame, p _k is the value assigned to the k-th subcarrier extracted from the preamble received signal of the serving cell, i _k (n ), n _k (n) represents interference and noise corresponding to the k-th subcarrier extracted from the preamble received signal of the n-th frame, respectively.

At this time, the channel variation estimation value is expressed as in the following equation.

이다.here

to be.

According to the preamble sequence of the serving cell, the UE obtains the power value of the preamble received signal of the current frame and the difference from the next preamble received signal by an interval of N _gaps , and accumulates the total N _frm -1 frames, and changes the channel amount. 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 estimation (velocity estimation) convex according to an embodiment of the present invention.

Referring to FIG. 5, the channel variation estimating block is largely an accumulation and metric calculation unit 510 for high speed, an accumulation and metric calculation unit for low speed, and an accumulation and metric calculation unit for low speed. Low Speed) 520, a Controller 515, and a Metric Decision 525.

The accumulation and metric calculation unit 510 for the high speed outputs the channel estimation value in the high speed mode in which the terminal moves at high speed. The channel estimation process is shown in Equation 3 above.

The accumulation and metric calculation unit 520 for the low speed outputs a channel estimation value in a low speed mode in which the terminal moves at a low speed. The channel estimation process is shown in Equation 3 above.

According to the preamble sequence of the serving cell, the UE obtains the power value of the preamble received signal of the current frame and the difference from the next preamble received signal by an interval of N _gaps , and accumulates the total N _frm -1 frames, and changes the channel amount. Estimate the value.

Here, P _r is the preamble received signal power value of the current frame, P _d is the power value of the difference with the next preamble received signal dropped by N _gap interval, IN ' _avg is the power value of the preamble received signal accumulated and averaged to be.

The controller 515 receives the P _r , P _d , and IN ′ _avg , and outputs the received value every predetermined period to the accumulation and metric calculation unit 520 for the low speed.

The metric determiner 525 receives the channel estimate value in the high speed mode and the channel estimate value in the low speed mode, and when the channel estimate value in the high speed mode is larger than a threshold, the metric determiner 525 receives the channel estimate value in the high speed mode. It is determined by the channel estimation value of the terminal.

6A is a flowchart illustrating an operation process of a controller in a channel variation estimation block (speed estimation) block according to an embodiment of the present invention.

Referring to FIG. 6A, the controller initializes an index (idx) value to 0 (step 610), receives an input value of P _r , P _d , and IN ′ _avg (615), and then resets the value every specific period (620). (Step 630) and output (step 625).

In steps 620 and 630, as a step of checking a predetermined period, m may be a predetermined constant, and when the value of idx increases (step 630), the remainder obtained by dividing the value of m and idx becomes 0 (step 620). ), And outputs the received P _r , P _d , and IN ' _avg values (step 625).

6B is a flowchart illustrating an operation process of a metric determination unit of a channel variation estimation block (velocity estimation) block according to an embodiment of the present invention.

Referring to FIG. 6B, the metric decision unit receives the channel estimation values from the accumulation and metric calculation unit for the high speed and the accumulation and metric calculation unit for the low speed (step 635).

If the channel estimate value in the fast mode is greater than the threshold (step 640), the channel estimate value in the fast mode is determined as the channel estimate value of the terminal. Then, the type (high speed type) of the terminal is determined. Here, the case where V_Type = 1 (step 645).

If the channel estimate value in the fast mode is smaller than the threshold, the channel estimate value in the slow mode is determined as the channel estimate value of the terminal. Then, the type (low speed type) of the terminal is determined. In this case, V_Type = 0 (step 650).

7 illustrates a MIMO channel correlation estimator according to an embodiment of the present invention.

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

The correlation estimation block 730 estimates the Tx and Rx antenna correlation from the H (n, k) matrix , which is a 4x4 channel in the k-th 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 scheme, H (n, k), which is a 4x4 channel matrix in the k-th subcarrier of the nth frame , may be expressed by the following equation.

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

In the Rx antenna correlation measurement scheme, H ⁽ⁿ⁾ (k), which is a 4x4 channel matrix in the k-th obtained subcarrier of the n-th frame, may be expressed by the following equation.

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

In the above-described block configuration, although not shown, the controller may perform the functions of the functional modules 510, 520, and 530 of FIG. 6 and the functional modules 720 and 730 of FIG. 7. In the present invention, it is shown to configure them separately to explain each function separately.

Therefore, in the case of actually implementing a product, all of the functions of the function modules may be configured to be processed by the controller, and only some of the functions may be configured to be processed by the controller.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

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

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

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

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

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

6A is a flowchart illustrating an operation process of a controller in a channel variation estimation block according to an embodiment of the present invention;

6B is a flowchart illustrating an operation process of a metric determination unit of a channel variation estimation block according to an embodiment of the present invention;

7 illustrates a MIMO channel correlation estimator according to an embodiment of the present invention;

8A is a diagram illustrating a # 1 of an MCS table according to an embodiment of the present invention.

8B is a view illustrating a # 1 of an MCS table according to an embodiment of the present invention;

8C is a view illustrating the number 1 of the MCS table according to the embodiment of the present invention;

FIG. 8D is a view illustrating the # 1 of the MCS table according to the embodiment of the present invention, and

FIG. 8E illustrates an # 1 of the MCS table according to an embodiment of the present invention. FIG.

Claims (2)

In the method for determining the transmission method of the terminal in a mobile communication system, Calculating an estimated value of the antenna channel correlation; Calculating a channel variation estimate value; Calculating a signal to interference plus noise ratio (SINR) estimate; And determining a Modulation and Coding Selection (MCS) level based on the estimated value of the antenna channel correlation, the estimated channel change amount, and the estimated SINR value. An apparatus for determining a transmission method of a terminal in a mobile communication system, An antenna channel correlation estimator for calculating an estimated value of the antenna channel correlation; A channel variation estimator for calculating channel variation estimation values; A SNIR estimator that calculates an SINR estimate, And an MCS level selector for determining an MCS level based on the estimated value of the antenna channel correlation, the estimated channel variation, and the estimated SINR.

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