KR101943985B1 - Method for channel estimation based of lte and apparatus for thereof - Google Patents

Abstract

More particularly, the present invention relates to an LTE-based channel estimation method capable of estimating a channel using a data signal as a pilot signal and reducing a maximum value due to a data determination error by applying a smoothing technique, And a device for this.
The LTE-based channel estimation method according to an embodiment of the present invention includes receiving a signal including a data symbol and pilot symbols from a transmitter, calculating an equalized symbol using the data symbol, Estimating a channel by demapping the equalized symbols, calculating a channel in a frequency domain region using the estimated channel, performing an interpolation process using the calculated channel in the frequency domain, And confirming the entire channel frequency response using the channel on which the interpolation process has been performed.

Description

TECHNICAL FIELD The present invention relates to an LTE-based channel estimation method,

More particularly, the present invention relates to an LTE-based channel estimation method capable of estimating a channel using a data signal as a pilot signal and reducing a maximum value due to a data determination error by applying a smoothing technique, And a device for this.

Communication between people vs. objects and objects vs. objects, rather than communication between humans, has been presented as a variety of applications and scenarios for several years, some of which are being promoted by commercialization and standardization to some extent. Particularly, in recent years, standardization of V2X (Vehicle-to-Everything) has been progressing actively. V2V (Vehicle-to-Vehicle), V2P (Vehicle-to- Pedestrian) Can be divided.

V2X is a technology that provides information through wired and wireless networks centering on vehicles and can support various services such as traffic efficiency and autonomous driving. For example, if inter-vehicle communication is possible, information on dangerous road conditions, bad weather, and traffic congestion can be transmitted from one vehicle to another. As such, V2X communication is closely related to safety and therefore reliability is required.

However, in V2V, which is a typical type in V2X communication technology, the transmitting and receiving ends move to each other and have a short correlation time due to the moving scattering body and the fixed scattering body. Also, since the maximum delay spread of the multipath has a large value and has a narrow correlation bandwidth, it is difficult to accurately estimate the channel.

Currently, V2V communication technology is based on DSRC (Dedicated Short Range Communication) and LTE (Long Term Evolution). The physical layer of the DSRC is called IEEE 802.11p and is based on IEEE 802.11a with a carrier frequency of 5.9 GHz and a bandwidth of 10 MHz. IEEE 802.11p performs channel estimation using an initial preamble. Due to the rapidly varying channel characteristics over time, the estimated channel is not accurate. Also, it has a disadvantage of not guaranteeing a high data rate due to limited spectrum.

Recently, research on LTE based V2V environment is actively conducted in 3GPP. LTE-based systems enable fast and reliable communication and guarantee quality of service (QoS). In addition, it is advantageous in terms of cost and has a merit that V2V can be provided more efficiently.

However, since the vehicle speed is very fast, there is a problem that the radio channel is rapidly changed with time, and accurate channel estimation is difficult.

Therefore, it is necessary to develop a technique for accurately and efficiently estimating a channel that changes very rapidly in an LTE based V2V environment.

Korean Registered Patent No. 10-1143242 Registered April 27, 2012 (Name: Channel Estimation for Wireless Communication)

The present invention has been proposed in order to solve the above-mentioned problems of the prior art. In particular, the present invention provides an LTE-based channel that can estimate a channel using a data signal as a pilot signal, And an apparatus for the same.

It is another object of the present invention to provide an LTE-based channel estimation method and an apparatus therefor that can minimize a channel estimation error by applying LMMSE in a final step.

However, the object of the present invention is not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood from the following description.

According to an aspect of the present invention, there is provided an LTE-based channel estimation method including: receiving a signal including a data symbol and pilot symbols from a transmitter; Calculating an equalized symbol using the data symbol; Demapping the calculated equalized symbols to estimate a channel; Calculating a channel in the frequency domain using the estimated channel; Performing an interpolation process using the frequency domain channel; And checking the entire channel frequency response using the channel on which the interpolation process has been performed.

The step of calculating the equalized symbols may divide the received data symbols into channels estimated from the previous symbols to calculate equalized symbols.

In this case, estimating the channel may include demapping the calculated equalized symbols and calculating a demapped symbol. And estimating a channel of the current symbol using the calculated demapping symbol for the received data symbol.

The calculating of the channel in the region may include calculating a channel of a time domain region according to a smoothing technique using the estimated channel and calculating a channel of the frequency domain region using the channel of the calculated time domain region .

In addition, the step of performing the interpolation process may be performed according to an LMMSE channel interpolation method.

Further, the method may further include calculating an equalized symbol for the next symbol if the entire channel frequency response is not confirmed after the step of checking the entire channel frequency response.

Furthermore, the present invention can provide a computer-readable recording medium on which a program for executing the LTE-based channel estimation method as described above is recorded.

According to an aspect of the present invention, there is provided a receiver for receiving a signal including a data symbol and pilot symbols from a transmitter, calculating an equalized symbol using the data symbol, Demapping the received symbol to calculate a channel in the frequency domain using the estimated channel, and then performing an interpolation process using the calculated channel in the frequency domain to check the entire channel frequency response And a channel estimator for estimating channel estimates.

The channel estimator demaps the calculated equalized symbols, estimates a channel of a time domain using the demapped symbols, and estimates a channel of the frequency domain based on the estimated channel of the time domain. Can be estimated.

In addition, the channel estimator may check the entire channel frequency response, and if the entire channel frequency response is not confirmed, the channel estimator may perform the calculation again after calculating the equalized symbols.

5G and B5G systems, and vehicle communication, the proposed channel estimation scheme can achieve higher performance gain compared with the channel estimation scheme used in existing mobile communication systems. This can improve the Normalized Mean Squared Error (NMSE) and BER (Bit Error Rate) performance by improving the Signal to Noise Ratio (SNR) performance showing the improvement of QoS of users.

Successful application of the present invention to 5G and B5G systems can be a preemptive technology in a vehicle environment. Reliable data detection is possible through accurate channel estimation, and a safety effect can be obtained in vehicle communication. Thus, the key technologies of the present invention will bring about academic ripple effects and securing prior art for national research and development.

In addition, various effects other than the above-described effects can be directly or implicitly disclosed in the detailed description according to the embodiment of the present invention to be described later.

1 is a diagram illustrating a structure of a transmitter according to an embodiment of the present invention.
2 is a diagram illustrating a structure of a receiver according to an embodiment of the present invention.
3 is a flowchart illustrating a channel estimation method according to an embodiment of the present invention.
4 is a diagram for explaining a channel estimation method according to an embodiment of the present invention in more detail.
5 to 8 are diagrams for explaining performance according to a channel estimation result according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:

In the following description and the accompanying drawings, detailed description of well-known functions or constructions that may obscure the subject matter of the present invention will be omitted. It should be noted that the same constituent elements are denoted by the same reference numerals as possible throughout the drawings.

The terms and words used in the following description and drawings are not to be construed in an ordinary sense or a dictionary, and the inventor can properly define his or her invention as a concept of a term to be described in the best way It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It is to be understood that equivalents and modifications are possible.

Also, terms including ordinal numbers such as first, second, etc. are used to describe various elements, and are used only for the purpose of distinguishing one element from another, Not used. For example, without departing from the scope of the present invention, the second component may be referred to as a first component, and similarly, the first component may also be referred to as a second component.

In addition, when referring to an element as being "connected" or "connected" to another element, it means that it can be connected or connected logically or physically. In other words, it is to be understood that although an element may be directly connected or connected to another element, there may be other elements in between, or indirectly connected or connected.

Also, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. It is also to be understood that the terms such as " comprising " or " having ", as used herein, are intended to specify the presence of stated features, integers, It should be understood that the foregoing does not preclude the presence or addition of other features, numbers, steps, operations, elements, parts, or combinations thereof.

In addition, embodiments within the scope of the present invention include computer-readable media having computer-executable instructions or data structures stored on computer-readable media. Such computer-readable media can be any available media that is accessible by a general purpose or special purpose computer system. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or in the form of computer- But is not limited to, a physical storage medium such as any other medium that can be used to store or communicate certain program code means of the general purpose or special purpose computer system, .

In the following description and claims, the term " network " is defined as one or more data links that enable electronic data to be transmitted between computer systems and / or modules. When the information is transmitted or provided to a computer system via a network or other (wired, wireless, or a combination of wired or wireless) communication connection, the connection may be understood as a computer-readable medium. Computer readable instructions include, for example, instructions and data that cause a general purpose computer system or special purpose computer system to perform a particular function or group of functions. The computer executable instructions may be binary, intermediate format instructions, such as, for example, assembly language, or even source code.

In addition, the invention may be practiced with other computer systems, including personal computers, laptop computers, handheld devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, a pager, and the like. < RTI ID = 0.0 > [0040] < / RTI > The invention may also be practiced in distributed systems environments where both local and remote computer systems linked by a combination of wired data links, wireless data links, or wired and wireless data links over a network perform tasks. In a distributed system environment, program modules may be located in local and remote memory storage devices.

Now, an LTE-based channel estimation method and an apparatus therefor according to an embodiment of the present invention will be described in detail with reference to the drawings. Here, the same reference numerals are used for similar functions and functions throughout the drawings, and a duplicate description thereof will be omitted.

Before describing the channel estimation method according to the embodiment of the present invention, the channel estimation method according to the prior art will be described first.

The conventional channel estimation methods include LS (Least Square), DDCE (Decision Directed Channel Estimation), CDP (Constructed Data Pilot), STA (Spectral Temporal Averaging), and Smoothing.

In the LS (Least Square) channel estimation scheme, pilot is a signal that is known to both the transmitting and receiving ends. Therefore, a pilot symbol transmitted from the received pilot symbol is transmitted to each slot, Is defined.

는 추정된 채널이며,

는 수신한 파일럿 심볼,

는 송신한 파일럿 심볼이다. n과 k는 심볼 인덱스, 부반송파 인덱스를 나타낸다. here,

Is an estimated channel,

Received pilot symbols,

Is the transmitted pilot symbol. n and k represent a symbol index and a subcarrier index.

Hereinafter, DDCE will be described.

DDCE is a decision-directed channel estimation method, and is a channel estimation method that is mainly used in a channel that changes slowly in time. The DDCE estimates the channel using the estimated transmission signal by using the highly correlated intersymbol data to show a high gain in a frequency non-selective environment.

The DDCE may be performed in the equalization and LS channel estimation steps. In the equalization step, the first data symbol received is equalized using a channel estimated as an initial LS (Least Square). The equalization process of the DDCE can be defined according to Equation (2) below.

는 등화한 심볼이며,

는 수신한 데이터 심볼,

는 n-1 번째 심볼에서 추정한 채널,

는 n=1일 때, LS로부터 얻어진 채널을 의미한다. here,

Is an equalized symbol,

The received data symbol,

Is a channel estimated from the (n-1) th symbol,

Means a channel obtained from LS when n = 1.

Thereafter, the DDCE scheme performs an LS channel estimation process. In this case, in order to estimate the channel of the n-th symbol in the DDCE scheme, the equalized symbols are demapped and the LS channel estimation is performed using the symbols. The LS channel estimation process can be expressed as follows.

는 디매핑한 심볼을 의미한다. here,

Denotes a de-mapped symbol.

The DDCE scheme among the channel estimation methods according to the related art has been described above.

Now, the CDP scheme among the channel estimation methods according to the related art will be described.

 The CDP (Constructed Data Pilot) method is one of the decision-directed channel estimation methods, which means a method of performing channel estimation using characteristics having a large correlation between two adjacent data symbols.

Such a CDP scheme can be achieved by a process of equalization, data pilot configuration, and LS channel estimation.

First, the received first data symbol is equalized using a channel estimated as an initial LS (Least Square) in the equalization process.

는 등화한 심볼을 의미하며,

는 수신한 데이터 심볼,

는 n-1번째 심볼에서 추정한 채널,

는 n=1일 때 LS로부터 얻어진 채널을 의미한다. 여기까지의 과정은 DDCE의 등화 과정과 동일하다. here,

Quot; means an equalized symbol,

The received data symbol,

Is a channel estimated from the (n-1) th symbol,

Means a channel obtained from LS when n = 1. The process up to this point is the same as the DDCE equalization process.

를 디매핑하여

를 구하게 되며, 이 심볼을 데이터 파일럿이라 한다. Thereafter, a data pilot is constructed. First, an equalized symbol

By demapping

And this symbol is called a data pilot.

가 성상도의 잘못된 영역에 놓이게 되면 디매핑한 심볼인

도 성상도의 잘못된 각 지점에 찍힐 수 있다. 그러나, 디매핑으로 인해 잡음이나 간섭이 부분적으로 완화될 수 있다. 남은 오류는 다음 과정인 두 개의 인접한 심볼 사이의 상관 특성을 이용하여 완화될 수 있다. Due to noise or interference

Is located in the wrong area of the constellation, the demapped symbol

Can also be shot at each wrong point of the constellation. However, demapping can partially mitigate noise or interference. The remaining error can be mitigated using the correlation property between two adjacent symbols, which is the next step.

Thereafter, the LS channel estimation is performed. At this time, the channel of the n-th symbol is estimated as LS by using the data pilot of the previous step, and this can be expressed by Equation (5).

는

를 등화하는 데 사용하게 된다. Then, the equalization process is performed. The equalization process can be defined by Equation (6) and Equation (7) below. First,

The

Is used to equalize.

는 n-1 번째 심볼에서 추정한 채널

에 의해 등화된다. And

Is the channel estimated from the (n-1) th symbol

Lt; / RTI >

와,

를 비교하게 되는데, 성상도 지점으로 디매핑하여

와

를 구하게 된다. Thereafter, the demapping process is performed. In the demapping process

Wow,

, Which is demapped to the constellation point

Wow

.

Thereafter, the comparison process can be performed using a high correlation characteristic between two adjacent data symbols.

는 하기의 <수학식 8>에 따라 정의될 수 있다. Indicating the result of the comparison

Can be defined according to Equation (8) below.

이라면, n 번째 심볼의 추정한 값

이 잘못된 값이며,

로 한다. 그렇지 않고, 만약

이라면

로 하게 된다. As a result of comparison,

, The estimated value of the n-th symbol

Is an invalid value,

. Otherwise, if

If

.

As described above, the CDP method of the conventional channel estimation method has been described.

Now, the STA scheme among the channel estimation methods according to the related art will be described.

The STA (Spectral Temporal Averaging) scheme estimates the channel using a data pilot and averages the frequency domain and the time domain.

First, the equalization process is defined as Equation (9) as follows: Equation (9) is a process of equalizing a first data symbol received using a channel estimated as an initial LS (Least Square).

는 등화한 심볼을 의미하며,

는 수신한 데이터 심볼,

는 n-1번째 심볼에서 추정한 채널,

는 n=1일 때 LS로부터 얻어진 채널을 의미한다. here,

Quot; means an equalized symbol,

The received data symbol,

Is a channel estimated from the (n-1) th symbol,

Means a channel obtained from LS when n = 1.

Thereafter, an LS channel estimation process is performed.

The STA scheme demaps the equalized symbols to estimate the channel of the nth symbol, and then uses the symbols to estimate the LS channel.

The LS channel estimation process can be defined as Equation (10) below.

는 디매핑한 심볼을 의미한다. 여기까지의 과정은 DDCE의 과정과 동일하다. At this time,

Denotes a de-mapped symbol. The process up to this point is the same as the DDCE process.

Then, an average in the frequency domain is taken using the estimated channel value.

는 주파수 영역에서 얼마나 많은 부반송파를 평균할 것인지에 대한 정수값이며,

는 가중치 계수로

로 정의된다. here

Is an integer value for how many subcarriers are to be averaged in the frequency domain,

Lt; RTI ID = 0.0 &gt;

.

Then, the average in the time domain is calculated. At this time, the average value of the channel is calculated in the frequency domain, and then the average is calculated in the time domain.

는 업데이트 변수로

의 값을 가지게 된다. here

Is an update variable.

. &Lt; / RTI &gt;

In this case, the parameters used in the STA and the corresponding channels are shown in Table 1 below.

STA parameter Adequate channel

large value of

slow fading channel small value of

Fast fading channel large value of

평일 쇠 채널 small value of

주파수 선택선

값은 slow fading 채널에 적합하며, 큰

값은 flat fading 채널에 적합하다. 반면에 작은

값은 fast fading 채널, 작은

값은 frequency selective fading 채널에 적합하다. large

Values are suitable for slow fading channels, and large

The value is suitable for flat fading channels. On the other hand,

Values are fast fading channels, small

The value is suitable for frequency selective fading channels.

As described above, the STA scheme among the channel estimation methods according to the related art has been described.

Now, a smoothing method among channel estimation methods according to the related art will be described.

Smoothing means a method by which a part of the estimated noise can be removed by using the radio propagation characteristics.

The smoothing process first performs a matrix transformation process, and the received signal can be defined according to Equation (13) below.

은 줄어든 FFT 행렬이며, F 행렬로부터 L의 열과

의 행을 선택한 것이다.

도 줄어든 시간영역 채널로 h로부터 L의 열과

의 행을 선택한 것이다. Where F is a fast Fourier transform (FFT) matrix, h is a time domain channel, and n is noise.

Is a reduced FFT matrix, and from F matrix to L column

Of course.

A reduced time-domain channel with columns from h to L

Of course.

Then, the time domain ML channel is estimated, which is estimated according to the following Equation (14).

에 대한 상기의 정의에서,

기호는 의사역행렬을 의미한다. Estimated time-domain channel

In the above definitions for &lt; RTI ID = 0.0 &

Symbol means pseudoinverse.

Thereafter, the ML channel estimation process for the frequency domain can be performed.

는 시간 영역 채널

로부터 다음의 <수학식 15>에 따라 산출될 수 있다. The estimated frequency domain channel

Time channel

Can be calculated from the following equation (15).

The smoothing technique according to the prior art has been described above.

Hereinafter, the channel estimation technique proposed in the present invention will be described in more detail.

First, the transmitting and receiving end according to the embodiment of the present invention will be described.

The present invention can perform operations on an LTE-based side link system based on 3GPP standardization. Therefore, the transmission / reception unit structure of the side link system can operate based on 3GPP LTE, but is not limited thereto.

The transmission / reception terminal structure of the present invention will be described with reference to Figs. 1 and 2. Fig.

FIG. 1 illustrates a structure of a transmitter according to an embodiment of the present invention. FIG. 2 illustrates a structure of a receiver according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 1, a transmitter 100 according to an embodiment of the present invention includes a scrambling unit 110, a modulation mapper 120, a layer mapper 130, a transform precoder 140, a precoding unit 150, a resource element mapper 160, and a signal generator 170.

In this transmitter 100, the baseband signal of the side link physical channel may be scrambled bit by bit by the scrambling unit 110. [ And the modulated mapper 120 modulates the scrambled bits to generate complex-valued symbols, and maps the complex-valued modulation symbols to one or several transmission layers.

The transform pre-coder 140 may perform a transform pre-coding process on the complex-valued symbol. The precoder unit 150 may precode symbols of each layer to transmit through the antenna port and the resource mapper 160 may transmit the symbol to the RE () of each antenna port using a reference signal, Resource Element).

Then, the signal generator 170 generates and transmits a complex-valued time domain SC-FDMA signal to each antenna port.

The following receiver 200 will be described with reference to FIG.

2, a receiver 200 of the present invention includes a demodulator 210, an advanced receiver 220, a channel estimator 230, a resource element demapper 240, A demodulator 270, a modulation demapper 280, and a descrambling unit 290. The demodulator 270 demodulates the demodulated signal, And the like.

In the receiver 200, when a signal is received through the antenna, the demodulator 210 can demodulate the signal using, for example, an SC-FDMA scheme. At this time, since the received data is distorted in size and phase by the channel, the channel estimator 230 can perform channel compensation through the channel estimator and the equalizer using the reference signal. The SC-FDMA technique performs M-point FFT processing for each layer before IFFT input in the transmitter modulation process and minimizes PAPR that can occur in the transmitter by performing N-point IFFT processing on the FFT output signal in the receiver demodulation process, SC-FDMA is used as a side-link radio access technology because it reduces consumption. Here, the subcarrier interval of the N-point IFFT is 15 kHz.

The channel estimation method in such a system will be described in more detail.

The channel estimation method in the present invention is referred to as HRCE technique. The HRCE technique proposed by the present invention means a technique in which a linear minimum mean square error (LMMSE) is applied to a smoothing technique and minimizes noise and exhibits better performance.

This will be described with reference to FIG.

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

Referring to FIG. 3, a receiver 200 of the present invention receives a signal from a transmitter 100 (S101). In this case, the received signal may include a pilot signal and a data signal. In the present invention, a channel is estimated using a data signal in place of a reference signal that is insufficient for a very rapidly changing channel.

For this, the receiver 200 of the present invention performs an equalization process on the data signal among the received signals (S103), and demodulates the equalized symbols to estimate a channel (S105). If the entire channel frequency response is not confirmed in step S111, the process of step S103 and subsequent steps is continuously repeated (step S113) .

The channel estimation method according to the embodiment of the present invention will be described in more detail.

4 is a diagram for explaining a channel estimation method according to an embodiment of the present invention in more detail.

라 하며, ①의 방향으로 전달된다. In FIG. 4, a receiver 200 receives a signal including a pilot symbol and a data symbol from a transmitter 100. At this time, the data symbols received by the receiver 200

And is transmitted in the direction of ①.

The receiver 200 of the present invention performs an equalization process. In particular, the equalization procedure of the present invention is performed using data symbols and can be defined according to Equation (16) below.

는 등화한 심볼이며,

는 수신한 데이터 심볼,

는 n-1 번째 심볼에서 추정한 채널,

는 LS로부터 얻어진 채널을 의미한다. here,

Is an equalized symbol,

The received data symbol,

Is a channel estimated from the (n-1) th symbol,

Means a channel obtained from the LS.

The receiver 200 of the present invention demodulates the equalized symbols to estimate the channel of the n-th symbol, and performs LS channel estimation using the symbols. The LS channel estimation process can be defined according to Equation (17) below.

는 디매핑한 심볼을 의미하며, 수신된 데이터 심볼에 디매핑한 심볼을 이용하여 n 번째 심볼의 채널을 추정하고 이를 ③의 방향으로 전달된다. here,

Denotes a de-mapped symbol, estimates the channel of the n-th symbol using the symbol demapping the received data symbol, and transmits it in the direction of (3).

Then, the receiver 200 of the present invention estimates the ML channel of the time domain region

The ML channel estimation process in the time domain region is defined as < EMI ID = 18.0 >

은 추정된 시간 영역 채널을 의미하며,

기호는 의사역행렬을 의미한다.

Denotes an estimated time-domain channel,

Symbol means pseudoinverse.

는 시간 영역 채널

로부터 산출될 수 있으며, 하기의 <수학식 19>의 정의에 따라 산출될 수 있다. The receiver 200 of the present invention estimates the ML channel in the frequency domain region. The estimated frequency domain channel

Time channel

And can be calculated according to the definition of Equation (19) below.

The calculated frequency domain channel is transmitted in the direction of (5).

Thereafter, the receiver 200 performs a channel interpolation process.

In the embodiment of the present invention, LMMSE channel interpolation is performed, and a channel to which LMMSE channel interpolation is applied can be defined according to Equation (20) below.

는 LMMSE 채널 보간 기법이 적용된 채널을 의미하며, W는 LMMSE 계수를 의미한다.

는 평활화(smoothing) 수행으로부터 얻어진 추정된 채널 값으로, 다시 말해 평활화 기법을 통해 추정된 주파수 도메인 영역의 채널을 의미하게 된다. 아울러, W는 하기의 <수학식 21>과 같이 MSE(Mean Square Error)를 최소화함으로써 산출될 수 있다. here,

Denotes a channel to which an LMMSE channel interpolation scheme is applied, and W denotes an LMMSE coefficient.

Is an estimated channel value obtained from performing smoothing, that is, a channel of a frequency domain region estimated through a smoothing technique. In addition, W can be calculated by minimizing the Mean Square Error (MSE) as shown in Equation (21) below.

Thereafter, the channel to which the LMMSE channel interpolation scheme is applied can be transmitted in the direction of (6), and the above process can be repeated until the entire channel frequency response is obtained.

The results of performing channel estimation according to the embodiment of the present invention will be described.

5 to 8 are diagrams for explaining performance according to a channel estimation result according to an embodiment of the present invention.

Prior to the description, the present invention can operate on the basis of an LTE side link system, and the relationship between the speed and the Doppler frequency is shown in Table 2 below.

Urban Highway Vehicle velocity 15km 140km Relative velocity 30 km 280 km Doppler frequency 166 Hz 1555Hz

The system parameters are shown in Table 3 below.

Parameter Value Carrier frequency 6GHz Bandwidth 10Mhz Sample frequency 15.36 MHz Subframe duration 1ms Subcarrier spacing 15kHz FFT size 1024 Occupied subcarriers 600 No. of subcarriers / PRB 12 Cyclic Prefix (CP) Normal CP No. of OFDM symblos / subframe 14 (Normal CP) Modulation scheme QPSK Noise AWGN

1,1 L 150 Velocity Urban 15 km, f_D = 166 Hz
Highway: 140k, f_D = 1555Hz Channel Model Urban: UMi_LoS
Highway: UMa_NLoS MIMO Configuration 1x1 Channel Estimation LS, DDCE, CDP, STA, Smoothing, HRCE Advanced Receiver ZF

The performance evaluation results of LS, DDCE, CDP, STA, Smoothing, which is a conventional channel estimation technique, and HRCE, which is a proposed method of the present invention, will be described. Performance evaluation was performed for Normalized Mean Square Error (NMSE) and Bit Error Rate (BER).

Figure 5 shows the NMSE in the urban area. Performance is improved in the order of DDCE, CDP, STA, Smoothing, LS, and the proposed technique, HRCE. In particular, in case of low SNR, error propagation phenomenon may occur due to determination error in DDCE. Also, it can be seen that the STA performs better than CDP. In case of LS, performance is good at low SNR, but at high SNR, error floor occurs. However, the HRCE of the present invention shows good performance at both low SNR and high SNR.

Figure 6 shows the NMSE on the highway. In the case of LS, it can be seen that errofloor occurs in all SNRs, and likewise HRCE of the present invention shows the best performance.

Figure 7 shows the uncoded BER in the urban area, and Figure 8 shows the uncoded BER in the highway. Likewise, the HRCE of the present invention shows the best performance.

The LTE-based channel estimation method according to the embodiment of the present invention and an apparatus therefor have been described above.

The LTE-based channel estimation method according to an embodiment of the present invention as described above may be provided in the form of a computer-readable medium suitable for storing computer program instructions and data.

At this time, the program recorded on the recording medium can be read and installed in the computer and executed, thereby executing the above-described functions.

In order to allow a computer to read a program recorded on a recording medium and to execute functions implemented by the program, the above-mentioned program may be stored in a computer-readable medium such as C, C ++, JAVA, machine language, and the like.

The code may include a function code related to a function or the like that defines the functions described above and may include an execution procedure related control code necessary for the processor of the computer to execute the functions described above according to a predetermined procedure. In addition, such code may further include memory reference related code as to what additional information or media needed to cause the processor of the computer to execute the aforementioned functions should be referenced at any location (address) of the internal or external memory of the computer . In addition, when a processor of a computer needs to communicate with any other computer or server that is remote to execute the above-described functions, the code may be stored in a memory of the computer using a communication module of the computer, It may further include a communication-related code such as how to communicate with another computer or a server, and what information or media should be transmitted or received during communication.

Such computer-readable media suitable for storing computer program instructions and data include, for example, magnetic media such as hard disks, floppy disks and magnetic tape, compact disk read only memory (CD-ROM) Optical media such as a DVD (Digital Video Disk), a magneto-optical medium such as a floppy disk, and a ROM (Read Only Memory), a RAM , Random Access Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (Electrically Erasable Programmable ROM). The processor and memory may be supplemented by, or incorporated in, special purpose logic circuits.

The computer readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. The functional program for implementing the present invention and the related code and code segment may be implemented by programmers in the technical field of the present invention in consideration of the system environment of the computer that reads the recording medium and executes the program, Or may be easily modified or modified by the user.

Each step according to the embodiments of the present invention can be implemented by a computer system and implemented by computer-executable instructions. As used herein, a " computing system " is defined as one or more software modules, one or more hardware modules, or a combination thereof that operate in conjunction with performing an operation on electronic data. For example, the definition of a computer system includes a software module such as a personal computer's operating system and a hardware component of a personal computer. The physical layout of the module is not important. The computer system may include one or more computers connected through a network.

Likewise, a computing system may be implemented in a single physical device in which an internal module, such as a memory and a processor, operates in conjunction with performing an operation on the electronic data.

Also, as described above, the present specification includes details of a number of specific implementations, but they should not be construed as being limitations on the scope of any invention or claim, but rather on the particular embodiment of a particular invention But should be understood as an explanation of certain features. Certain features described herein in the context of separate embodiments may be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments, either individually or in any suitable subcombination. Further, although the features may operate in a particular combination and may be initially described as so claimed, one or more features from the claimed combination may in some cases be excluded from the combination, Or a variant of a subcombination.

Likewise, although the operations are depicted in the drawings in a particular order, it should be understood that such operations must be performed in that particular order or sequential order shown to achieve the desired result, or that all illustrated operations should be performed. In certain cases, multitasking and parallel processing may be advantageous. Also, the separation of the various system components of the above-described embodiments should not be understood as requiring such separation in all embodiments, and the described program components and systems will generally be integrated together into a single software product or packaged into multiple software products It should be understood.

Certain embodiments of the subject matter described herein have been described. Other embodiments are within the scope of the following claims. For example, the operations recited in the claims may be performed in a different order and still achieve desirable results. By way of example, the process illustrated in the accompanying drawings does not necessarily require that particular illustrated or sequential order to obtain the desired results. In certain implementations, multitasking and parallel processing may be advantageous.

The description sets forth the best mode of the invention, and is provided to illustrate the invention and to enable those skilled in the art to make and use the invention. The written description is not intended to limit the invention to the specific terminology presented. Thus, while the present invention has been described in detail with reference to the above examples, those skilled in the art will be able to make adaptations, modifications, and variations on these examples without departing from the scope of the present invention.

Therefore, the scope of the present invention should not be limited by the described embodiments but should be defined by the claims.

The next generation mobile communication core technology obtained through the present invention is expected to contribute not only to enhancement of mobile communication performance but also to export of terminal parts and network construction. In addition, reliable data detection can have a significant impact on the vehicle communications market. Specifically, it will contribute to securing superiority in standardization competition and leading the next generation mobile communication market. It will also improve technology self-reliance and price competitiveness of domestic mobile communication industry through transfer of intellectual property rights such as patents related to next generation mobile communication, In addition to reducing the cost of mobile communication industry due to cross-licensing, it is anticipated to reduce royalty payment and import substitution effect by securing core technology of next generation mobile communication.

In addition, since the present invention is not only possible to be marketed or operated, but also can be practically and practically carried out, it is industrially applicable.

100: Transmitter
200: receiver

Claims (10)

The receiver receiving a signal comprising a data symbol and pilot symbols from a transmitter;
Calculating an equalized symbol using the data symbol;
Demapping the calculated equalized symbols to estimate a channel;
Calculating a channel in the frequency domain using the estimated channel;
Performing an interpolation process using the frequency domain channel; And
And checking an overall channel frequency response using the channel on which the interpolation process has been performed,
The step of computing the equalized symbols
Dividing the received data symbol by a channel estimated from a previous symbol to calculate an equalized symbol,
The step of estimating the channel
Demapping the calculated equalized symbols and calculating demapped symbols; And
Estimating a channel of the current symbol using the calculated demapping symbol;
And estimating a channel estimate based on the estimated channel estimate. delete delete The method according to claim 1,
The step of calculating the channel in the region
Calculating a channel of a time domain region according to a smoothing scheme using the estimated channel, and calculating a channel of a frequency domain region using the channel of the calculated time domain region. The method according to claim 1,
The step of performing the interpolation process
LMMSE channel interpolation scheme based on the LMMSE channel interpolation scheme. The method according to claim 1,
After confirming the overall channel frequency response,
If the full channel frequency response is not ascertained, calculating an equalized symbol for the next symbol;
Wherein the channel estimation method further comprises: A computer-readable recording medium recording a program for executing the LTE-based channel estimation method according to any one of claims 1 to 6. Receiving a signal including a data symbol and pilot symbols from a transmitter, calculating an equalized symbol using the data symbol, demapping the calculated equalized symbol to estimate a channel, And a channel estimator for calculating a channel in a frequency domain region and performing an interpolation process using the calculated channel in the frequency domain to confirm the entire channel frequency response,
The channel estimator
Dividing the data symbol by a channel estimated from a previous symbol to calculate an equalized symbol,
Demapping the calculated equalized symbols, estimating a channel of the time domain using the demapped symbols, and estimating a channel of the frequency domain based on the estimated channel of the time domain. Receiver. delete 9. The method of claim 8,
The channel estimator
And verifies the entire channel frequency response, and if the entire channel frequency response is not confirmed, performs the process again after calculating the equalized symbols.

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