KR20130033661A - Lqi calculation apparatus for receiving of ofdm system - Google Patents

Abstract

PURPOSE: An LQI(Link Quality Indicator) calculation apparatus of an orthogonal frequency division multiplexing system is provided to calculate an LQI without using an additional hardware device. CONSTITUTION: A receiving device includes a synchronization processing unit(100), a channel estimating and compensating unit(110), and an LQI calculating unit(120). The synchronization processing unit synchronizes a signal received through a channel. The channel estimating and compensating unit converts a synchronized signal in a time domain into a signal in a frequency domain and performs compensation for a converted signal using a channel estimating result about the channel. The LQI calculating unit calculates an LQI using the phase of the signal which the compensation is performed for. [Reference numerals] (100) Synchronization processing unit; (114) Channel estimating unit; (118) Tracking unit; (120) LQI calculating unit; (130) LQI table; (140) Medium access control layer;

Description

LQI Calculation APPARATUS FOR RECEIVING OF OFDM SYSTEM

The present invention relates to a mobile communication system, and more particularly, to facilitate switching of a data rate mode in a state in which channel information is reflected in a receiver constellation point after channel compensation so that received data is changed in size to data of a transmission constellation point. The present invention relates to an LQI obtaining apparatus of an orthogonal frequency division multiplexing system capable of generating link quality indication information (LQI).

Orthogonal Frequency Division Multiplexing (OFDM) is used in wireless communication systems because it can efficiently utilize limited frequency resources and provide high data rates. In addition, wireless communication devices have tended to use direct conversion transceivers for miniaturization and high integration of systems.

In general, in OFDM systems, many piconet networks connect a large number of devices in a narrow space with limited frequency resources. In this limited environment, in order to minimize mutual interference and transmit as much data as possible, transmission power control and data rate mode conversion are required. This is necessary. Therefore, in order to construct such an efficient piconet network, it is necessary to upload meaningful information on the received signal level from a physical layer to a media access control (MAC) layer. To this end, existing wireless system technologies include various techniques for setting a received signal strength indication (hereinafter, referred to as 'RSSI').

As described above, in the related arts, the degree of modulation of the transmission data is adjusted by using the RSSI setting method and the set RSSI value, the RSSI limit value in the RSSI reception is varied, and the optimum RSSI limit value is selected and set even in a noisy environment. .

However, it is necessary to calculate an LQI (hereinafter referred to as an 'LQI') indicating an actual link quality and transmit the LQI to the medium access control layer. In order to consider LQI, hardware devices must be additionally configured in an existing wireless system.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus capable of generating LQI, which is link quality indication information, without a separate hardware apparatus.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, the LQI obtaining apparatus of an orthogonal frequency division multiplexing system according to an embodiment of the present invention is a synchronization processor for synchronizing a signal received through a channel, and the signal of the synchronized time domain signal in the frequency domain A channel estimating and compensating unit for compensating for the converted signal using a channel estimation result for the channel, and an LQI calculating unit calculating an LQI using a phase of the compensating signal. can do.

In the LQI obtaining apparatus of the orthogonal frequency division multiplexing system according to an embodiment of the present invention, the LQI calculating unit calculates the LQI by using the phase of the compensation signal and the phase of the reception constellation point.

In the LQI obtaining apparatus of the orthogonal frequency division multiplexing system according to an embodiment of the present invention, the LQI calculating unit is characterized in that the phase of the reception constellation point is π / 4.

In the LQI obtaining apparatus of an orthogonal frequency division multiplexing system according to an embodiment of the present invention, the LQI calculating unit calculates the LQI by giving the channel estimation result as a weight.

The present invention generates the link quality indication information (LQI) for facilitating the data rate mode switching in the state where the channel information is reflected in the receiver constellation point after the channel compensation and the received data has been changed in size in the data of the transmission constellation point. The advantage is that LQI can be created without a separate hardware device.

1 is a diagram illustrating a receiving device in an OFDM system according to an embodiment of the present invention;
2 is a diagram illustrating a form in which weights of reception constellation points are applied to an output of a frequency domain equalizer according to an embodiment of the present invention;
3 is a view showing a form of noise around the constellation point,
4 is a diagram showing a phase of a constellation point,
5 is a diagram illustrating an LQI calculation unit according to an embodiment of the present invention;
6 is a diagram illustrating an LQI calculation unit according to another embodiment of the present invention;
7 to 10 are graphs showing the results of calculating the LQI after applying the reception apparatus according to an embodiment of the present invention to AWGN and fading channel.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

In the following description of the present invention, 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. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

Each block of the accompanying block diagrams and combinations of steps of the flowchart may be performed by computer program instructions. These computer program instructions may be loaded into a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus so that the instructions, which may be executed by a processor of a computer or other programmable data processing apparatus, And means for performing the functions described in each step are created. These computer program instructions may be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular manner, and thus the computer usable or computer readable memory. It is also possible for the instructions stored in to produce an article of manufacture containing instruction means for performing the functions described in each block or flowchart of each step of the block diagram. Computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operating steps may be performed on the computer or other programmable data processing equipment to create a computer-implemented process to create a computer or other programmable data. Instructions that perform processing equipment may also provide steps for performing the functions described in each block of the block diagram and in each step of the flowchart.

In addition, each block or step may represent a portion of a module, segment or code that includes one or more executable instructions for executing a specified logical function (s). It should also be noted that in some alternative embodiments, the functions mentioned in the blocks or steps may occur out of order. For example, the two blocks or steps shown in succession may in fact be executed substantially concurrently or the blocks or steps may sometimes be performed in the reverse order, depending on the functionality involved.

Hereinafter, a reception apparatus and a method of an OFDM system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a receiving apparatus in an OFDM system according to an embodiment of the present invention.

As shown in FIG. 1, a receiving apparatus according to an embodiment of the present invention includes a synchronization processor 100, a channel estimator and compensator 110, an LQI calculator 120, an LQI table 130, and a medium access control layer. 140, and the like.

When the signal received through the wireless communication network is input through an A / D converter (not shown), the synchronization processing unit 100 performs synchronization through a synchronization algorithm (Sync.), And then the channel estimation and compensation unit 110. Output to

The channel estimating and compensating unit 110 includes an FFT 112 for converting a signal that has been synchronized, that is, a signal in a time domain to a signal in a frequency domain, and a channel estimator for generating a channel estimation result for a channel on which a signal is received ( 114, a tracking unit which performs phase and time tracking on the outputs of the frequency domain equalizer 116 and the frequency domain equalizer 116 and outputs them to an input terminal of the frequency domain equalizer 116. 118, and the like.

The output data of the FFT 112 may be represented by FFT_OUT [m, n], where m is an OFDM symbol index and n is a subcarrier index.

If the channel estimation result of the channel estimator 114 is CE [n], the channel compensation result of the frequency domain equalizer 116 performs channel compensation as shown in Equation 1 or 2 below.

Performing channel compensation through Equation 1 performs channel compensation using multiplication, and performing channel compensation through Equation 2 means that a receiver can be implemented by performing channel compensation using division. .

Meanwhile, Equations 1 and 2 may be expressed as Equation 3 below if the synchronization algorithm is perfect.

만큼의 가중치가 적용된 상태이다. 이 경우 도 2에 도시된 바와 같이 수신 성상점의 가중치(weight)가 가해진 형태를 가질 수 있는데, 즉 아래의 수학식 4를 통해 LQI를 계산할 수 있다. In Equation 3, TX [m, n] is data located at a transmission constellation point of a QPSK signal, and FDE_OUT [m, n] is at a transmission constellation point.

As much weight is applied. In this case, as shown in FIG. 2, a weight of a reception constellation point may be added, that is, the LQI may be calculated through Equation 4 below.

가 1이 아니면 정상적인 값을 추출할 수 없으며, 도 3에 도시된 바와 같이 성상점 주위에 잡음(noise)이 있는 형태에서 사용될 수 있는 것이다.In Equation 4, LQI is

If it is not 1, the normal value cannot be extracted, and as shown in FIG. 3, it can be used in the form of noise around the constellation point.

For this reason, the LQI calculation unit 120 according to the embodiment of the present invention may calculate the LQI with only the phase except the magnitude in Equation 4.

The LQI calculator 120 may estimate the LQI with only the phase except for the magnitude in Equation 4, that is, the LQI may be estimated using Equation 5 below.

는 도 4의 1사분면 성상점이 위상

에 존재하기 때문이다.In Equation 5 above

Is the first quadrant constellation point in FIG.

Because it exists in.

Meanwhile, the LQI calculator 120 may match the SNR by applying a preset weight and bias to the result value of Equation 5.

The LQI calculator 120 may estimate the LQI by adding the weight of the influence of the channel up to the magnitude, that is, the channel estimation result, to the Equation 5, that is, the Equation 6 below to estimate the LQI. Can be.

As described above, by applying the channel estimation result to the LQI estimation, more accurate LQI can be estimated at high SNR.

The LQI calculation unit 120 generates the LQI table 130 according to the result of analyzing the statistical characteristic according to the SNR through Equation 5 or 6 (result of Equation 5 or 6), and then generates the LQI table 130. The medium may be transferred to the access control layer 140.

The LQI calculator 120 may be implemented as shown in FIGS. 5 and 6.

First, as illustrated in FIG. 5, the LQI calculator 120 performs phase (π /) of a constellation point in a phase except for magnitude in a signal output from the frequency domain equalizer 116 of the channel estimation and compensation unit 110. The multiplier may be configured to receive a subtracted part 4), an arithmetic operator that calculates the output of the multiplier by M * N, and a delay unit (D). In other words, the multiplier in the LQI calculation unit 120 performs a multiplication operation by inputting the phase (π / 4) of the constellation point in the portion (FDE_OUT_angle [m, n]) excluding the size portion in FDE_OUT [m, n]. The result of the execution is output, and the result of the multiplication operation and the signal temp1 (D) output from the delay unit D are sampled and output as M * N, as shown in Equation 5 above.

)를 입력받아 곱셈 연산을 수행한 결과를 출력하고, 곱셈 연산한 결과와 지연기(D)로부터 출력되는 신호(temp1(D))를 M*N으로 샘플링하여 출력한다는 것으로, 상기의 수학식 6과 같다.In addition, as shown in FIG. 6, the LQI calculation unit 120 has a constellation point in phase except for the magnitude in the channel estimation result and the signal output from the frequency domain equalizer 116 of the channel estimation and compensation unit 110. It may be composed of a multiplier that receives a portion minus the phase (π / 4), and calculates the output of the multiplier by M * N, and a delay (D). In other words, the multiplier in the LQI calculator 120 calculates the phase (π / 4) of the constellation point at the portion (FDE_OUT_angle [m, n]) excluding the size portion of FDE_OUT [m, n] and the channel estimation result (

) And outputs the result of performing the multiplication operation, and outputs the result of the multiplication operation and the signal temp1 (D) output from the delay unit D by sampling M * N. Same as

An example of applying the reception device according to an embodiment of the present invention to an AWGN and a fading channel will be described below with reference to FIGS. 7 to 10.

7 and 8 illustrate the LQI using the result of estimating the LQI using the channel compensation result as shown in Equation 1 in the AWGN channel environment and the result of performing the channel compensation as shown in Equation 2 above. In FIG. 7 and FIG. 8, the x-axis is SNR, the y-axis of FIG. 7 is a standard deviation with respect to the SNR estimation error, the y-axis of FIG. 8 is an average of the SNR estimation errors, and CE_MUL is the above. It is a result of estimating LQI by the method proposed in the embodiment of the present invention using the result of performing channel compensation as shown in Equation 1, and CE_DIV is the above equation using the result of performing channel compensation as shown in Equation 2 above. It is the result of estimating LQI as shown in Equation 4.

9 and 10 illustrate results of estimating LQI using the result of performing channel compensation as shown in Equation 1 in a fading channel environment and using the result of performing channel compensation as shown in Equation 2 above. 9 and 10, the x-axis is SNR, the y-axis of FIG. 9 is a standard deviation with respect to the SNR estimation error, and the y-axis of FIG. 10 is the average of the SNR estimation errors, CE_MUL. Is a result of estimating the LQI by the method proposed by the embodiment of the present invention using the result of performing channel compensation as shown in Equation 1 above, and CE_DIV using the result of performing channel compensation as shown in Equation 2 above. The result of estimating the LQI as shown in Equation 4 above.

As shown in FIG. 7 to FIG. 10, even if the LQI estimation according to the embodiment of the present invention is performed by performing channel compensation using multiplication without using division (Equation 2), it can be confirmed that there is almost no difference in performance. Therefore, a simpler algorithm can be used as the channel compensation method.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand. For example, those skilled in the art can change the material, size, etc. of each component according to the application field, or combine or replace the disclosed embodiments in a form that is not clearly disclosed in the embodiments of the present invention, but this also It does not depart from the scope of the invention. Therefore, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive, and that these modified embodiments are included in the technical idea described in the claims of the present invention.

100: synchronization processing unit 110: channel estimation and compensation unit
112: FFT 114: channel estimator
116: frequency domain equalizer 118: tracking unit
120: LQI calculation unit 130: LQI table
140: media access control layer

Claims (1)

A synchronization processor for synchronizing a signal received through a channel;
A channel estimating and compensating unit converting the synchronized signal in the time domain into a signal in the frequency domain, and performing compensation for the converted signal using a channel estimation result for the channel;
And an LQI calculator configured to calculate an LQI using the phase of the compensated signal.
LQI Acquisition System for Orthogonal Frequency Division Multiplexing System.

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