WO2010077079A2

WO2010077079A2 - Channel estimation support method and device

Info

Publication number: WO2010077079A2
Application number: PCT/KR2009/007930
Authority: WO
Inventors: 최밝음; 김정주; 이동관
Original assignee: 주식회사 포스데이타
Priority date: 2008-12-31
Filing date: 2009-12-30
Publication date: 2010-07-08
Also published as: KR20100080157A; WO2010077079A3; KR101051888B1

Abstract

The present invention relates to a mobile Internet system, and more particularly to a channel estimation support method and device. In one example, the channel estimation support method is a channel estimation support method in a mobile Internet system, comprising the steps of: calculating a first average window size by using the difference between adjacent channels in a domain constituted by either a time domain or a frequency domain; calculating a second average window size by using the difference between adjacent channels in the remaining domain constituted by either the time domain or the frequency domain; and determining a two-dimensional average window size by using the first average window size and the second average window size.

Description

Channel estimation support method and device

The present invention relates to a channel estimation support method and apparatus for a portable Internet system.

As a high speed / high capacity wireless communication system capable of processing and transmitting a variety of information such as voice, video, and data is required, various quality of service (QoS) is referred to in the portable Internet system according to the IEEE 802.16 standard. ) Is being researched to provide users.

In wireless channel environments, errors occur due to various factors such as multipath interference, shadowing, propagation attenuation, time-varying noise, and fading, resulting in loss of information. . This loss of information due to an error is a factor that reduces the overall performance of the wireless communication system.

In the portable Internet system, an appropriate modulation and coding scheme (hereinafter referred to as "MCS") is applied according to channel quality to increase data transmission efficiency and to minimize QoS loss due to the error. I'm trying to provide.

1 is a diagram illustrating a channel estimation method using a pilot symbol and an average window.

Referring to FIG. 1, in order to decode the received data and apply an appropriate MCS according to channel quality, channel estimation must be performed first.

The channel estimation is performed using signals promised between the base station BS and the terminal MS, wherein the signal including information on channel quality is referred to as a pilot symbol 10. do.

Channel estimation performs interpolation between adjacent pilot symbols to estimate a channel of any data symbol 30 on a frame. However, since a signal received through a wireless channel includes noise, distortion of the signal due to noise may occur. In order to minimize the effect of noise, moving averaging is performed using the average window 50.

Here, the average window 50 is defined as the number of symbols in the time domain and the number of subcarriers in the frequency domain that constitute one frame. Averaging using the window 50 is performed in a two dimension region defined by a time domain and a frequency domain. As the average window 50 having the two-dimensional area moves, the channel for each data symbol 30 is estimated in the data area of the frame.

In this case, if the moving averaging is performed through a fixed sized average window, the accuracy of channel estimation may be lowered. That is, when the channel selectivity and the change in the received SNR (Signal to Noise Ratio) are high, if the moving averaging is performed through a fixed sized average window, the distorted channel may be estimated in the actual channel.

For example, as shown in "A" of FIG. 1, when the average window 50 is small in size, the influence due to noise cannot be minimized, so that proper channel estimation is not performed. On the other hand, as shown in "B" of FIG. 1, when the average window 50 has a large size, adjacent channels have different states in the time and frequency domains, and thus the correlation between the actual channel and the estimated channel is poor. There is a problem that channel estimation is not made.

As such, when the channel estimation is not accurately performed and the estimated channel is different from the actual channel, the terminal cannot correctly decode the received data, and the base station cannot determine the MCS level suitable for the channel state of the terminal. This will occur.

For example, if the MCS level higher than the channel state of the terminal is determined because the channel estimation is not accurate, there is a problem that the terminal cannot decode the data transmitted from the base station, and the MCS level lower than the channel state of the terminal is If it is determined that the data transmitted from the base station can be received and decoded by the terminal, there is a problem that the data transmission efficiency is lower than when applying the MCS level for the channel state.

Due to the above problems, a channel estimation support method is required to increase the correlation between the actual channel and the estimated channel while minimizing the influence of noise depending on the channel condition. However, the average window size can be set differently according to the channel characteristics. Channel estimation support method is not suggested.

Disclosure of Invention The present invention has been made in view of the above-described problems, and it is a technical object of the present invention to provide a channel estimation support method and apparatus capable of increasing the correlation between an actual channel and an estimated channel while minimizing the influence of noise.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a channel estimation support method and apparatus capable of improving data transmission efficiency by increasing channel estimation accuracy.

A channel estimation support method according to an embodiment of the present invention for achieving the above object is a method for supporting channel estimation in a portable Internet system, by using a difference between adjacent channels in any one of a time domain and a frequency domain. Calculating average window size; Calculating a second average window size using a difference between adjacent channels in the other one of the time domain and the frequency domain; Determining a two-dimensional average window size by using the first average window size and the second average window size.

In accordance with another aspect of the present invention, a channel estimation support apparatus includes: a phase difference detector configured to detect a phase difference between pilot symbols detected from a received signal; A frame counter counting a frame in which phase difference detection between adjacent pilot symbols has been performed; A storage unit in which phase differences between adjacent pilot symbols are accumulated and stored; And calculating a first average window size using a difference between adjacent channels in any one of a time domain and a frequency domain, and using a difference between adjacent channels in the other one of the time and frequency domains. And a setting unit for calculating a size and determining a two-dimensional average window size using the first average window size and the second average window size.

The present invention according to the embodiment can provide a channel estimation support and apparatus that can improve the accuracy of the channel estimation by setting the size of the average window for channel estimation in consideration of the SNR and the channel selectivity of the received signal.

The present invention according to the embodiment minimizes the effects of noise in the time domain and the frequency domain, and also supports channel estimation that can improve data transmission efficiency by increasing the accuracy of channel estimation through an average window that can increase channel correlation. It provides a method and apparatus.

1 is a diagram illustrating a channel estimation method using an average window.

2 is a diagram illustrating a method of calculating an average window size through a phase difference between adjacent channels.

3 is a flowchart illustrating in detail a channel estimation support method according to an exemplary embodiment of the present invention.

4 is a flowchart illustrating a channel estimation support method according to another embodiment of the present invention in detail.

5 and 6 are diagrams showing the performance of the channel estimation support method according to the prior art using a fixed average window size in accordance with an embodiment of the present invention in terms of PER.

7 and 8 are diagrams showing the performance of the channel estimation support method according to the prior art using a fixed average window size in accordance with an embodiment of the present invention in terms of BER.

9 is a view showing a channel estimation support apparatus according to an embodiment of the present invention.

10 is a view showing a channel estimation support apparatus according to another embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention. The present invention relates to a mobile Internet system, and more particularly, to a channel estimation support method and apparatus.

As shown in FIG. 1, channel estimation of data symbols included in a frame includes moving averages of channel values calculated through interpolation between adjacent pilot symbols 10 on the average window 50. moving average). However, distortion may occur in the estimated channel value due to interference and noise between channels having different characteristics. As a result, the accuracy of channel estimation varies depending on how the size of the average window for averaging is set.

According to an embodiment of the present invention, in order to minimize the influence of channel selectivity and noise, a channel estimation support method and apparatus for optimizing the average window size, which is the basis of moving average, according to channel conditions, is proposed. I would like to.

Since the channel characteristic does not change rapidly in a certain frame period (for example, 100 frames) except for a special case, determination of the average window size may be performed in a preset frame period (for example, 100 frames). Further, determination of average window size is made based on the phase difference between the SRN of the received signal and the pilot symbols included in the frame.

Here, the predetermined frame period may be set to at least one frame period, and may be set differently in consideration of channel characteristics according to the moving speed of the terminal. For example, when the terminal has a channel characteristic of moving to 60 km / h, the predetermined frame period may be set to 100 frames. Meanwhile, when the terminal has a channel characteristic of moving to 10 km / h, the predetermined frame period may be set to 600 frames.

First, the size of the average window according to the channel state has the following characteristics. In the case where the change in the channel characteristics is small, the larger the average window is advantageous for channel estimation. In the case in which the change in the channel characteristics is large, the smaller the average window size is advantageous in the channel estimation.

As shown in FIG. 1, the downlink frame is composed of tones consisting of symbols on the horizontal (time) axis and subcarriers on the vertical (frequency) axis. The information capable of estimating a channel includes pilot symbols ( 10), channel information of a data symbol can be obtained through interpolation between adjacent pilot symbols.

In order to set an average window size according to channel characteristics, first, a definition of a received signal model is required. Here, the received signal includes a noise signal and an interference signal, and the noise signal is similar to white noise, so that the estimated channel (

) Can be expressed as Equation 1 below. In addition, although the actual average window is a two-dimensional structure consisting of a time domain and a frequency domain, a channel estimated in one-dimensional (1D) domain may be considered by dividing the time domain and the frequency domain, respectively. Can be.

Equation 1

here,

silver

Estimated channel of the first subcarrier,

Means the number of channels included in the averaging, that is, the size of the average window,

silver

Channel information of the first subcarrier,

Is The actual channel of the first subcarrier,

Is

The white noise of the first subcarrier. Therefore, the white channel information is included in the information of the channel estimated using the average window.

In Equation 1, if a channel is fixed for a certain frame period, the channel to be estimated (

) Can be expressed as Equation 2 below.

Equation 2

Here, since noise is generated randomly randomly like white noise, it can be considered that there is no correlation between the noises. Therefore, the estimated channel (

Noise (N ₀ ) of the noise (variance) of the equation (1)

As can be seen, as the size N of the average window increases, it becomes smaller. Therefore, as the size N of the average window increases, the influence of noise decreases, thereby making accurate channel estimation.

Herein, since the actual channel h (k) is inevitably different between adjacent channels in the time domain and the frequency domain, Equation 2 may be expressed as Equation 3 below.

Equation 3

In Equation 3, ∇ (i) is the difference between the actual channel to be estimated and the channel added due to the moving average through the average window (

).

It can be expressed as Equation 4 below by taking a square with respect to Equation 3 above.

Equation 4

Referring to Equation 4, when the change of the channel is considered, as the average window size "N" becomes larger, the deviation of the noise, that is, the distortion of the channel due to the noise becomes smaller,

In contrast to noise, as the average window N increases in size, the accuracy of channel estimation due to the difference between adjacent channels decreases.

In order to reduce the effect of lowering the accuracy of channel estimation due to the difference between the channels, the ratio of the noise (N ₀ ) and the average window (N) and the difference between adjacent channels (

) And the ratio of average window size (N) should be considered. Accordingly, the value of the average window size N should be set such that the result value of Equation 5 below is minimized.

Equation 5

Since the channel environment is affected by the speed of the terminal and the surrounding topography, the optimal N value varies according to the channel characteristics of each terminal. Therefore, rather than setting the N value to any fixed value, it should be adapted to the changing channel environment. Here, since the value of "N ₀ " is information on noise provided to the base station and the terminal in advance, information necessary for determining the size of the average window is 된다 (i). Next, the following matters are assumed to quantitatively determine the difference ∇ (i) between the adjacent channels.

First, the change between adjacent channels is not large. Second, the change between channels can be expressed by the phase difference. Third, the phase change of the channel changes only in one direction as it moves away from the channel to be estimated to the adjacent channel.

In accordance with Equations 1 to 5 and the above assumptions, each channel

Is

It can be expressed as shown in Equation 6 below.

Equation 6

In conclusion, as shown in FIG. 2, if only the information of the phase difference θ (j) between adjacent channels is provided, an optimal averaging sample (averaging sample) capable of reducing the difference between adjacent channels in the one-dimensional region, that is, the influence of channel selectivity, is obtained. ) Can be obtained. This means that the size of the average window can be determined in one dimension (1D). Here, the size of the average window in one dimension (1D) can be obtained through cross correlation between adjacent pilot symbols, as shown in Equation 7 below.

Equation 7

As described above, the average window size N that can be calculated through the information on the phase difference θ (j) between adjacent channels is obtained by obtaining N having a minimum value as a result of Equation 8 below. This can be modeled as a complex number where the actual channel is of constant size and differs only in the magnitude of the phase between adjacent channels. Accordingly, an average window size N that can minimize channel estimation error due to noise and channel selectivity can be obtained. Here, the fact that the result value of Equation 8 is minimized means that the difference between the actual channel and the estimated channel is minimal.

Equation 8

In Equation 8,

Denotes the ratio of the sum of the differences between adjacent channels and the average window size (N). And,

Denotes the ratio of noise (N ₀ ) to average window size (N). Here, the difference between adjacent channels may be obtained through a phase difference between adjacent pilot symbols among pilot symbols detected in the received signal.

The average window size N at which the result of Equation 8 is minimum is reduced according to Equation 2, while reducing noise variance, and according to Equation 5, the influence of channel selectivity due to the difference between channels. The average window size (N) in the one-dimensional region can be reduced. This means that an optimal average window size (N) can be obtained that can minimize channel estimation errors due to noise and channel deviations in one 1-dimensional (1D) domain, either in the time domain or in the frequency domain. do.

As described above, by selecting one of the two-dimensional (2D) time domain and the frequency domain, the optimal average window size (N) in one dimension (1D) through the result value according to Equations 1 to 8 Get In addition, if the optimum average window size N is obtained for the other regions, the average window size can be determined in the two-dimensional (2D) region.

As described above, in the determination of the average window size, when detection means for detecting phase differences between adjacent channels are provided for each of the time domain and the frequency domain, the size of the average window is simultaneously determined in the time domain and the frequency domain. You can decide. On the other hand, when the detection means for detecting the phase difference between adjacent channels is not provided separately for the time domain and the frequency domain, the magnitude of the average window is first determined for one of the time domain and the frequency domain, and then The size of the average window can be determined for one area.

When channel estimation is performed by moving averaging through an average window having an N value obtained in each of the time domain and the frequency domain, it is possible to reduce the influence of noise variance in the two-dimensional (2D) domain, The influence of channel selectivity due to the difference can be reduced, thereby improving the accuracy of channel estimation.

In the description of Equation 8, the "N" value has been described in consideration of "CrossTerm", but the phase change between adjacent channels may be reversed without moving in only one direction. As shown in Equation 9, a value of "N" can be obtained without considering the "CrossTerm".

Equation 9

3 is a flowchart illustrating a method for supporting channel estimation according to an embodiment of the present invention in detail. The channel estimation support method of FIG. 3 may be applied to a case in which detection means for detecting phase differences between adjacent channels are provided separately for each of the time domain and the frequency domain. Referring to FIG. 3, a channel estimation support method according to an embodiment of the present invention will be described.

A pilot symbol is detected from the signal received through the receiving antenna (S100).

Thereafter, a phase difference between adjacent pilot symbols among the received pilot symbols in each of the time domain and the frequency domain is detected (S120). Here, detection of a phase difference between adjacent pilot symbols may be performed every frame.

Thereafter, phase difference values between adjacent pilot symbols detected in each of the time domain and the frequency domain are accumulated and stored (S130). Here, phase difference values between adjacent pilot symbols in each of the time domain and the frequency domain are accumulated and stored for a predetermined frame period (for example, 100 frames). The phase difference value between adjacent pilot symbols accumulated and stored for a certain frame period may be averaged when the predetermined frame period elapses and used to determine the average window size.

Subsequently, the frame in which the phase difference value is calculated between the adjacent pilot symbols is counted to determine whether a predetermined frame period has elapsed (S140).

Here, the counting of frames is for resetting the size of the average window at every frame period. Since the channel characteristics may change over time, the channel estimation support method according to an embodiment of the present invention may determine the size of the average window used to perform moving averaging in consideration of the channel characteristics that change with time. Change it every cycle.

Here, the predetermined frame period for changing the size of the average window may be set to at least one frame, and may be set in consideration of the moving speed of the terminal. For example, when the terminal is moving at a speed of 60 km / h, the predetermined frame period may be set to 100 frames. When the terminal is moving at a speed of 10 km / h, the predetermined frame period may be set to 600 frames. have.

As a result of checking in S140, if the preset frame period has not elapsed, the previously set average window size is maintained during the preset frame period (S150), and the channel is estimated using the average window having the previously set size (S180). ).

On the other hand, as a result of checking in S140, when a predetermined frame period has elapsed, Equation 8 is obtained by using a phase difference value between adjacent pilot symbols detected for each of the time domain and the frequency domain accumulated during a predetermined frame period. Calculate the value of N (average window size) at which the result of N is minimized.

That is, as shown in Equation 8, the sum of the difference between adjacent channels and the first result value according to the ratio of the average window size (N) and the ratio of the noise (N ₀ ) and the average window size (N) The second resultant value is calculated, and an N value at which the sum of the first resultant value and the second resultant value is minimum is calculated to obtain an average window size in the one-dimensional region.

In this case, an N value representing the size of the average window is calculated for each of the time domain and the frequency domain. Here, the SNR of each of the symbols detected from the received signal is taken into account in calculating the average window size. Through this, in each of the time domain and the frequency domain, the size of the optimized average window in consideration of the channel selectivity between the SNR of the received signal and adjacent channels is determined (S160).

In this case, the value of N where the result of Equation 8 is minimum is reduced according to Equation 2 according to Equation 2, and according to Equation 5, This will be the size of the optimized average window that will reduce the impact.

At this time, the phase difference between adjacent pilot symbols is averaged in each of the time and frequency domains accumulated and stored for a predetermined frame period in S130, and the time and frequency domains in which the average value of the phase difference between adjacent pilot symbols is performed in S160. In order to determine the size of the optimized average window considering the SNR and channel selectivity of the received signal.

That is, when a preset frame period has elapsed and the user wants to change the size of the previously set average window, the phase difference value of the pilot symbols received at the present time point and the time domain and the frequency domain that are accumulated and accumulated for a predetermined frame period are adjacent to each other. The accuracy of the channel estimation can be improved by using the average value of the phase difference values between the pilot symbols together.

Subsequently, the optimized average window size in consideration of SNR and channel selectivity in the 2D region (2D) is set using the optimized average window size in the time domain and the optimized average window size in the frequency domain. (S170). Here, the set average window size is applied to the moving averaging calculation.

Thereafter, the channel is estimated using the average window having the size set in S170 (S180).

Thereafter, the channel is compensated using the estimated channel value, and the received data is decoded according to the compensated channel (S190).

4 is a flowchart illustrating in detail a channel estimation support method according to another exemplary embodiment of the present invention.

The channel estimation support method of FIG. 4 may be applied to a case of detecting a phase difference between adjacent pilot symbols in a time domain and a frequency domain as one detection unit for detecting a phase difference between adjacent channels. Referring to FIG. 4, a channel estimation support method according to another embodiment of the present invention will be described.

The pilot symbol is detected from the signal received through the receiving antenna (S200).

Thereafter, one domain is first selected from a time domain and a frequency domain (S210). In the following description, it is assumed that the time domain is first selected from the time domain and the frequency domain in S210.

Thereafter, a phase difference between adjacent pilot symbols among the pilot symbols received in the time domain is detected (S220). Here, detection of a phase difference between adjacent pilot symbols may be performed at least every one frame.

Thereafter, the phase difference values between adjacent pilot symbols detected in the time domain are accumulated and stored (S230). Here, phase difference values between adjacent pilot symbols in the time domain are accumulated and stored for a predetermined frame period (for example, 100 frames). The phase difference value between adjacent pilot symbols accumulated and stored for a certain frame period may be averaged when the predetermined frame period elapses and used to determine the average window size.

Thereafter, one region other than the region selected in S210 is selected (S215). Since the time domain is selected in S210, a frequency domain is selected in S215.

Thereafter, a phase difference between adjacent pilot symbols among the pilot symbols received in the frequency domain is detected (S225). Here, detection of a phase difference between adjacent pilot symbols may be performed at least every one frame.

Thereafter, the phase difference values between adjacent pilot symbols detected in the frequency domain are accumulated and stored (S235). Here, the phase difference between adjacent pilot symbols in the frequency domain is accumulated and stored for a predetermined frame period (for example, 100 frames) according to the moving speed of the terminal. The phase difference value between adjacent pilot symbols accumulated and stored for a certain frame period may be averaged when the predetermined frame period elapses and used to determine the average window size.

Subsequently, the frame in which the phase difference value between adjacent pilot symbols is calculated in the time domain and the frequency domain is counted, and it is checked whether a preset frame period has elapsed (S240).

Here, the predetermined frame period for changing the size of the average window may be set to at least one frame, and may be set to 100 to 600 frames in consideration of the moving speed of the terminal. For example, when the terminal is moving at a speed of 60 km / h, the predetermined frame period may be set to 100 frames. When the terminal is moving at a speed of 10 km / h, the predetermined frame period may be set to 600 frames. have.

As a result of checking in S240, if the preset frame period has not elapsed, the previously set average window size is maintained during the preset frame period (S250), and the channel is estimated using the average window having the previously set size (S280). ).

On the other hand, as a result of checking in S240, when a predetermined frame period has elapsed, the result of Equation 8 using a phase difference value between adjacent pilot symbols detected for each of the time domain and the frequency domain during a predetermined frame period. Calculates the minimum value of N (average window). That is, as shown in Equation 8, the sum of the difference between adjacent channels and the first result value according to the ratio of the average window size (N) and the ratio of the noise (N ₀ ) and the average window size (N) The second resultant value is calculated, and an N value at which the sum of the first resultant value and the second resultant value is minimum is calculated to obtain an average window size in the one-dimensional region.

In this case, an N value representing the size of the average window is calculated for each of the time domain and the frequency domain. Here, the SNR of each of the symbols detected from the received signal is taken into account in calculating the average window size. In this way, for each of the time domain and the frequency domain, the optimized average window size is determined in consideration of the SNR of the received signal and channel selectivity between adjacent channels.

Hereinafter, as an example, the window size is first determined for the time domain from the time domain and the frequency domain, and then the window size is determined for the frequency domain.

First, using the phase difference value between adjacent pilot symbols detected in the time domain, an N (average window size) value at which the result of Equation 8 is minimized is calculated. Through this, the size of the optimized average window in consideration of the SNR and the channel selectivity of the signal received in the time domain is determined (S260). In this case, the value of N where the result of Equation 8 is minimum is reduced according to Equation 2 according to Equation 2, and according to Equation 5, This will be the size of the optimized average window that will reduce the impact.

Subsequently, using the phase difference value between adjacent pilot symbols detected in the frequency domain, an N (average window size) value at which the result of Equation 8 is minimized is calculated. Through this, the size of the optimized average window considering the SNR and the channel selectivity of the signal received in the frequency domain is determined (S265).

At this time, the phase difference value between adjacent pilot symbols in the time domain and the frequency domain accumulated and stored for a predetermined frame period in S230 and S235 is averaged, and the time domain in which the average value of the phase difference between adjacent pilot symbols is performed in S260 and S265 And the size of the optimized average window considering the SNR and channel selectivity of the signal received in the frequency domain.

Afterwards, the optimized average window size is calculated by considering the SNR and channel selectivity in the 2D region (2D) using the optimized average window size in the time domain calculated in S260 and the optimized average window size in the frequency domain calculated in S265. The size of the window is set (S270). Here, the set average window size is applied to the moving averaging calculation.

Thereafter, the channel is estimated using the average window of the set size (S280).

Thereafter, the channel is compensated using the estimated channel value, and the received data is decoded according to the compensated channel (S290).

5 and 6 are diagrams illustrating performance of a channel estimation support method according to an embodiment of the present invention and a conventional technology using a fixed average window size in terms of PER, and FIGS. 7 and 8 are fixed average windows. A diagram showing the performance of the channel estimation support method according to the prior art using the size and the embodiment of the present invention in terms of BER.

5 to 8 show the comparison of the performance of the present invention according to the prior art and the embodiment under the conditions shown in Table 1 below.

Table 1

Along with the conditions of Table 1, one transmission antenna and one reception antenna were performed in the downlink (DL), and the moving speeds of the terminals were QPSK 3/4, 16QAM in an environment of 10 Km / h and 60 Km / h. 1/2, 16QAM 3/4 and 64QAM 3/4 MCS were applied, respectively.

As a result of the performance comparison according to the above conditions, the channel estimation support method according to the embodiment of the present invention is improved performance compared to the prior art at the MCS level of QPSK 3/4, 16QAM 1/2, 16QAM 3/4, 64QAM 3/4 It can be confirmed.

The channel estimation support method according to the embodiments of the present invention, as shown in Figures 4 and 5, it was confirmed that the gain of 0.5 ~ 2dB compared to the prior art in terms of PER, it is shown in Figures 6 and 7 As can be seen, it can be confirmed that a gain of 0.5 to 1.dB can be obtained in comparison with the prior art from the BER perspective.

When channel estimation is performed through the channel estimation support method according to the embodiments of the present invention, it is possible to provide improved channel estimation performance compared to the fixed average window method of the prior art. In addition, the channel estimation support method according to the embodiments of the present invention can improve the data transmission efficiency by applying the MCS suitable for the channel state through accurate channel estimation.

9, the channel estimation support apparatus 100 according to an exemplary embodiment of the present invention may include a first phase difference detector 110a, a second phase difference detector 110b, a setting unit 120, and a frame counter 140. And a storage unit 145.

The first phase difference detector 110a and the second phase difference detector 110b detect a phase difference between adjacent pilot symbols among the received pilot symbols, and adjacent pilot symbols in each of the time domain and the frequency domain at the same time. Two

phase difference detectors

110a and 110b are separately configured to detect the phase difference between them. For example, the first phase difference detector 110a detects a phase difference between adjacent pilot symbols in the time domain, and the second phase difference detector 110b detects a phase difference between adjacent pilot symbols in the frequency domain. The phase difference detection between adjacent pilot symbols performed by the first phase difference detector 110a and the second phase difference detector 110b may be performed at least every one frame.

The frame counter 130 counts frames in which the phase difference detection between adjacent pilot symbols is counted by the first phase difference detector 110a and the second phase difference detector 110b, and checks whether a predetermined frame period has elapsed.

In this case, the counting of frames is for resetting the set average window for each frame period, and the average window size used for performing moving averaging is determined for each frame period in consideration of channel characteristics that change with time. Count frames so you can change them.

Counting information of the frame counter 130 is provided to the setting unit 120 to maintain or reset the size of the set average window. When the average window is reset after the preset frame period elapses, the average value of the phase differences accumulated during a predetermined frame period (for example, 100 frames) as well as the phase difference between the pilot symbols received in the current frame are determined. Will reflect.

Since the change in channel characteristics is highly correlated between adjacent channels and adjacent frames, it is not only the phase difference value between pilot symbols received in the current frame but also the phase difference value between pilot symbols accumulated over a certain frame period. Reflecting this in, can improve the accuracy of channel estimation.

To this end, the frame counter 130 may include a storage unit 135 in which phase difference values between adjacent pilot symbols detected in the time domain and the frequency domain are accumulated and stored. In addition, in the case of resetting the size of the average window, the frame counter 130 calculates an average value of phase differences between pilot symbols for a predetermined frame period stored in the storage unit 135 and sets the setting unit 120. Can be provided to

In the above-described description and FIG. 9, the storage unit 135 is illustrated and described as being included in the frame counter 130, but this shows one embodiment. In another exemplary embodiment, the storage 135 may be included in the first phase difference detector 110a and the second phase difference detector 110b or the setter 120.

The setting unit 120 uses a phase difference value between adjacent pilot symbols detected in the time domain and the frequency domain provided by the first phase difference detector 110a and the second phase difference detector 110b to simplify the adjacent channels. Detect the difference.

As shown in Equation 8, the setting unit 120 includes a first result value according to the ratio of the difference between adjacent channels and the average window size N, the noise N ₀ , and the average window size N. A second result value according to the ratio of) is calculated, and an N value at which the sum of the first result value and the second result value is minimum is calculated to set the average window size in the one-dimensional region.

Through this, the average window reflects the characteristics according to SNR, noise, and channel selectivity (difference between adjacent channels) in the 2D region (2D) through the size "N" value of the average window calculated for the time domain and the frequency domain, respectively. Sets the size of.

The two-dimensional average window size set by the setting unit 120 may be an optimized average window size that may reduce the influence of noise variance and reduce the influence of channel selectivity due to the difference between channels. The set average window size is provided to the channel estimator to be used for moving average calculation.

As described above, in the two-dimensional region 2D provided by the channel estimation support apparatus 100, the channel is estimated using an average window having an optimized size considering SNR and channel selectivity, thereby improving the accuracy of the channel estimation. Can be. In addition, through the accurate channel estimation, it is possible to improve the data transmission efficiency by applying the MCS suitable for the channel state.

10 is a view showing a channel estimation support apparatus according to another embodiment of the present invention. The channel estimation support apparatus 100 according to another exemplary embodiment of the present invention shown in FIG. 10 is illustrated in FIG. 9 except that the phase difference detection unit 110 for detecting the phase difference between adjacent channels is integrated into one configuration. It includes the same configuration as the channel estimation support apparatus 100 shown.

When the phase difference detection unit 110 is provided in common for the time domain and the frequency domain, one phase, for example, a time domain is first selected from the time domain and the frequency domain, and the phase difference between adjacent pilot symbols in the time domain is determined. Detect. Then, the phase difference between adjacent pilot symbols for the remaining frequency domain is detected. A configuration of setting an average window size using phase difference values between pilot symbols in the time domain and the frequency domain detected by the phase difference detector 110 is the same as that of FIG. 9.

It will be apparent to those skilled in the art that the present invention described above may be embodied in other specific forms without changing the technical spirit or essential features of the present invention.

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.

Claims

In the channel estimation support method in the portable Internet system,

Calculating a first average window size using a difference between adjacent channels in one of a time domain and a frequency domain;

Calculating a second average window size using a difference between adjacent channels in the other one of the time domain and the frequency domain;

And determining a two-dimensional average window size by using the first average window size and the second average window size.
The method of claim 1,

The calculating of the first average window size or the second average window size may include calculating an average window size N at which a result of the following equation is minimized,

Wherein N 0 is noise and N is average window size.
The method of claim 1,

And a difference between the adjacent channels is calculated using a phase difference between pilot symbols detected from a received frame.
The method of claim 3, wherein

The phase difference between the pilot symbols

The channel estimation support method, characterized in that for using the average value of the accumulated value for a predetermined frame period.
The method of claim 3, wherein the phase difference between the pilot symbols

Channel estimation support method, characterized in that for using the average value of the value accumulated during the frame period set according to the movement speed of the terminal.
The method of claim 1,

And recalculating the average window size according to the preset frame period.
A phase difference detector for detecting a phase difference between pilot symbols detected from the received signal;

A frame counter counting a frame in which phase difference detection between adjacent pilot symbols has been performed;

A storage unit in which phase differences between adjacent pilot symbols are accumulated and stored; And

Calculating a first average window size using a difference between adjacent channels in any one of a time domain and a frequency domain,

A second average window size is calculated using the difference between adjacent channels in the other one of the time domain and the frequency domain,

A setting unit for determining a two-dimensional average window size using the first average window size and the second average window size;

Channel estimation support apparatus comprising a.
The method of claim 7, wherein the setting unit

Calculate an average window size N at which the result of the following equation becomes the minimum,

Wherein N 0 is noise and N is average window size.
The method of claim 7, wherein the setting unit

And estimating a difference between adjacent channels by using a phase difference between pilot symbols detected from a received frame.
The method of claim 9, wherein the setting unit

And calculating a phase difference between the pilot symbols by using an average value of values accumulated during a preset frame period.
The method of claim 9, wherein the setting unit

And a phase difference between the pilot symbols using an average value of values accumulated during a frame period set according to a moving speed of a terminal.
The method of claim 7, wherein the setting unit

And estimating the average window size according to a preset frame period.
The method of claim 7, wherein the setting unit

And changing the average window size within the number of symbols or the number of subcarriers constituting one frame to calculate the first and second average window sizes.
The method of claim 7, wherein the frame counter

And an average value of a phase difference between adjacent pilot symbols accumulated and stored for a predetermined frame period.