KR102177342B1 - Method of receiving a signal in communication system and apparatus thereof - Google Patents

Abstract

A method of receiving a signal in a communication system and an apparatus thereof are disclosed. According to an embodiment of the present invention, a method of receiving a signal may comprise the steps of: receiving a data unit including a plurality of orthogonal frequency division modulation (OFDM) symbols from a second communication node; obtaining an original cyclic prefix (CP) from a first OFDM symbol that is any one of the plurality of OFDM symbols constituting the data unit; obtaining a reference CP constituting a rear end of the first OFDM symbol; calculating an integer-multiple frequency offset estimated value of the data unit using the original CP and the reference CP; and compensating for an integer-multiple frequency offset of the data unit based on the estimated value. Accordingly, the performance of the communication system may be improved.

Description

Communication system signal reception method and apparatus {METHOD OF RECEIVING A SIGNAL IN COMMUNICATION SYSTEM AND APPARATUS THEREOF}

The present invention relates to a communication system, and more particularly, to a communication system that modulates data using an orthogonal frequency division multiplexing (OFDM) scheme.

In the current communication system, a signal can be modulated using an orthogonal frequency division multiplexing method.

When a signal is modulated using an orthogonal frequency division multiplexing scheme, the center frequencies of the transmitting module and the receiving module may not be exactly the same. Due to this, noise may occur in all modulated signals, and a frequency offset may occur in a communication system.

Orthogonality between multiple carriers included in a signal modulated by an orthogonal frequency multiplexing method may be broken due to the occurrence of a frequency offset. For this reason, ICI (Inter-Channel Interference) may occur between multi-carriers, which may lead to performance degradation of the communication system.

An object of the present invention for solving the above problems is to provide a method and apparatus for estimating and compensating a frequency offset of an OFDM symbol.

In order to achieve the above object, a method of operating a communication node according to an embodiment of the present invention includes receiving a data unit including a plurality of orthogonal frequency division modulation (OFDM) symbols from a second communication node, configuring the data unit. Obtaining an original cyclic prefix (CP) from a first OFDM symbol that is any one of a plurality of OFDM symbols, obtaining a reference CP constituting a rear end of the first OFDM symbol, the It may include calculating an integer multiple frequency offset estimate value of the data unit using the original CP and the reference CP, and compensating the integer multiple frequency offset of the data unit based on the estimated value.

Here, the step of obtaining the original CP includes: a signal related to the original CP based on a fractional frequency offset of the data unit, a Fast Fourier Transform (FFT) size of the first OFDM symbol, and an FFT size of the original CP. It may be characterized in that it is a step of obtaining.

Here, the step of obtaining the reference CP is a step of obtaining the reference CP based on the fractional frequency offset of the data unit, the FFT size of the first OFDM symbol, and the FFT size of the reference CP. I can.

Here, the calculating of the estimated value of the integer multiple frequency offset includes obtaining complex conjugates of the original CP, multiplying the complex conjugates by the reference CP corresponding to the original CP, and calculating an average value of the multiplying results. It may further include the step of calculating.

Here, the compensating for the integer multiple frequency offset may be a step of compensating the integer multiple frequency offset of the data unit by multiplying the data unit by the estimated integer multiple frequency offset value.

A communication node according to another embodiment of the present invention may include a processor and a memory in which one or more instructions executed by the processor are stored, and the one or more instructions may include a plurality of instructions from the second communication node. Receiving a data unit including orthogonal frequency division modulation (OFDM) symbols, obtaining an original CP (Cyclic Prefix) of a first OFDM symbol, which is one of a plurality of OFDM symbols constituting the data unit, A reference CP constituting a rear end of the first OFDM symbol is obtained, an integer multiple frequency offset estimation value of the data unit is calculated based on the original CP and the reference CP, and based on the estimated value, the data unit is It can be implemented to compensate for an integer multiple frequency offset.

Here, in the case of obtaining the original reference CP, the one or more commands are based on the fractional frequency offset of the data unit, a Fast Fourier Transform (FFT) size of the first OFDM symbol, and the FFT size of the original CP. It can be implemented to obtain a signal about the original CP.

Here, in the case of calculating the estimated value of the integer multiple frequency offset, the one or more instructions obtain complex conjugates of the original CP, multiply the complex conjugates by a reference CP corresponding to the original CP, and the average of the multiplying results It may be characterized in that it is further executed to calculate the value.

According to the present invention, orthogonality between subcarriers included in an OFDM symbol can be maintained by estimating and compensating for an integer multiple frequency offset generated in an orthogonal frequency division modulation (OFDM) data symbol, and inter-channel inter-channel (ICI) between OFDM symbols Interference) can be prevented. Accordingly, the performance of the communication system can be improved.

1 is a conceptual diagram showing a first embodiment of a communication system.
2 is a block diagram showing a first embodiment of a communication node constituting a communication system.
3 is a block diagram showing a first embodiment of a transmission module included in a communication node in a communication system.
4 is a block diagram showing a first embodiment of a bandbase processing unit included in a transmission module in a communication system.
5 is a block diagram showing a first embodiment of a receiving module included in a communication node in a communication system.
6 is a block diagram showing a first embodiment of a bandbase processing unit included in a receiving module in a communication system.
7 is a flow chart showing a first embodiment of a method of transmitting and receiving data in a communication system.

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. The term and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. Should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in the present application. Does not.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. In describing the present invention, in order to facilitate an overall understanding, the same reference numerals are used for the same elements in the drawings, and duplicate descriptions for the same elements are omitted.

A communication system to which embodiments according to the present invention are applied will be described. The communication system to which the embodiments according to the present invention are applied is not limited to the contents described below, and the embodiments according to the present invention can be applied to various communication systems. Here, the communication system may be used with the same meaning as a communication network.

1 is a conceptual diagram showing a first embodiment of a communication system.

Referring to FIG. 1, a communication system may include a plurality of communication nodes 110 and 120. The plurality of communication nodes 110 and 120 may perform communication using communication methods specified in IEEE (Institute of Electrical and Electroni reference CP Engineers) 802.15.7 (for example, IEEE 802.15.7m). For example, each of the plurality of communication nodes 110 and 120 may include an LED (Light Emitting Diode) and a camera, and may transmit a signal by blinking an LED, and based on the blinking state of the LED photographed by the camera. To obtain a signal. Each of the plurality of communication nodes 110 and 120 may be a sensor node, an Internet of Things (IoT) node, a smart phone, or the like. Each of the plurality of communication nodes 110 and 120 may have the following structure.

2 is a block diagram showing a first embodiment of a communication node constituting a communication system.

Referring to FIG. 2, the communication node 200 may include a processor 210, a memory 220, a transmission module 230, and a reception module 240. In addition, the communication node 200 may further include a storage device 250 and the like. Each of the components included in the communication node 200 may be connected by a bus 260 to perform communication with each other.

However, each of the components included in the communication node 200 may be connected through an individual interface or an individual bus based on the processor 210 instead of the common bus 260. For example, the processor 210 may be connected to at least one of the memory 220, the transmission module 230, the reception module 240, and the storage device 250 through a dedicated interface.

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 250. The processor 210 may mean a central processing unit (native CPU), a graphics processing unit (see graphi CP processing unit, GPU), or a dedicated processor in which methods according to embodiments of the present invention are performed. have. Each of the memory 220 and the storage device 250 may be configured with at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory 220 may be formed of at least one of a read only memory (ROM) and a random access memory (RAM). The transmission module 230 and the reception module 240 may communicate with each other and may operate under the control of the processor 210.

Meanwhile, the transmission module 230 may be configured as follows.

3 is a block diagram showing a first embodiment of a transmission module included in a communication node in a communication system.

Referring to FIG. 3, the transmission module 300 may include a baseband processing unit 310 and a radio frequency (RF) transmission unit 320. Here, the transmission module 300 may be configured to be the same as or similar to the transmission module 230 of FIG. 2.

The baseband processor 310 may process a baseband input signal using an orthogonal frequency division multiplexing (OFDM) scheme.

Meanwhile, the baseband processing unit 310 may be configured as follows.

4 is a block diagram showing a first embodiment of a transmission processing unit included in a transmission module in a communication system.

Referring to FIG. 4, the baseband processing unit 400 includes a serial to parallel converter unit 410, a Forward Error Correction encoder 420, a Quadrature Amplitude Modulation unit 430, and Mapping unit 440, IFFT (Inverse Fast Fourier Transform) unit 450, CP addition unit (cyclic prefix add unit, 460) and parallel / serial conversion unit (parallel series converter unit, 470), DU (Data unit) generation It may include a unit 480 and a digital to analog conversion unit 490. In embodiments, a unit may mean a means, an entity, an apparatus, etc. for performing a specific function.

The baseband processing unit 400 of FIG. 4 may be configured to be the same as or similar to the baseband processing unit 310 of FIG. 3.

Serial bit streams may be input to the serial/parallel conversion unit 410. The serial/parallel conversion unit 410 may convert a plurality of input serial bit streams into a parallel form. The serial/parallel conversion unit 410 may transmit parallel bit streams to the FEC encoder 420.

The FEC encoder 420 may receive parallel bit streams from the serial/parallel conversion unit 410. The FEC encoder 420 may add additional information for FEC to each of the bit streams. Here, "bit stream + additional information" may be a data symbol.

The FEC encoder 420 may transmit data symbols to the QAM unit 430.

The QAM unit 430 may receive data symbols from the FEC unit 420. The QAM unit 430 may modulate data symbols in a QAM scheme. For example, the QAM unit 430 may modulate data symbols in a 16-QAM or 64-QAM scheme. When data symbols are modulated by the 16-QAM method, data symbols can be quantized into 16 levels and mapped to 16 coordinates of the I/Q plot. When data symbols are modulated by the 64-QAM method, data symbols are converted to 64 data symbols. It can be quantized into two levels and mapped to 64 coordinates of the I/Q plot.

The data symbols modulated by the QAM method may include a real part and an imaginary part according to the coordinates of the I/Q plot. The QAM unit 430 may transmit the data symbols modulated by the QAM method to the mapping unit 440.

The mapping unit 440 may receive data symbols modulated by the QAM method from the QAM unit 430. The mapping unit 440 may map the modulated data symbols according to a preset mapping method. The mapping unit 440 may transmit the mapped data symbols to the IFFT unit 450.

The IFFT unit 450 may receive mapped data symbols from the mapping unit 440. The IFFT unit 450 may convert data symbols in the frequency domain into data symbols in the time domain using an Inverse Fast Fourier Transform (IFFT) scheme.

In addition, the IFFT unit 450 may convert data symbols in the frequency domain into data symbols in the time domain using an Inverse Discrete Fourier Transform (IDFT) method. The IFFT unit 450 may transmit the data symbols in the time domain to the CP adding unit 460.

The CP adding unit 460 may receive data symbols in the time domain from the IFFT unit 450. The CP adding unit 460 may insert an original CP (Cyclic Prefix) into each of the data symbols in the time domain.

The CP adding unit 460 may add the original CP to each data symbol by copying a reference CP constituting a predetermined section after each of the data symbols and inserting it in the front of the data symbol. Here, "data symbol + raw CP" may be an OFDM symbol.

일 수 있다. 또한, 각각의 OFDM 심볼들에 포함된 데이터 심볼들 각각의 FFT 크기는 N일 수 있다.The size of the FFT (Fast Fourier Transform) of the original CP and the reference CP constituting each OFDM symbol is

Can be Also, the FFT size of each of the data symbols included in each of the OFDM symbols may be N.

The CP adding unit 460 may transmit OFDM symbols to the parallel/serial conversion unit 470. The parallel/serial conversion unit 470 may receive OFDM symbols from the CP adding unit 460. The parallel/serial conversion unit 470 may convert parallel OFDM symbols into serial OFDM symbols. The parallel/serial conversion unit 470 may transmit serial OFDM symbols to the DU generation unit 480.

The DU generation unit 480 may receive serial-type OFDM symbols from the parallel/serial conversion unit 470. The DU generation unit 480 may generate a data unit based on a preset number of OFDM symbols. The DU generation unit 480 may transmit a data unit to the digital-to-analog conversion unit 490.

The digital to analog conversion unit 490 may receive a data unit from the DU generating unit 480. The digital to analog conversion unit 490 may convert the received digital data unit into an analog data unit. The digital-to-analog conversion unit 490 may transmit the analog data unit to an RF transmitter (eg, the RF transmitter 320 of FIG. 3 ).

Referring back to FIG. 3, the RF transmitter 320 may receive a data unit from the baseband processor 310. The RF transmitter 320 may transmit a data unit to a receiving module (eg, the receiving module 240 of FIG. 2 ).

5 is a block diagram showing a first embodiment of a receiving module included in a communication node in a communication system.

Referring to FIG. 5, the receiving module 500 may include a radio frequency (RF) receiving unit 510 and a baseband processing unit 520. The receiving module 500 of FIG. 5 may be configured in the same or similar to the receiving module 240 of FIG. 2.

The RF receiver 510 may communicate with the transmission module 300 (refer to FIG. 3 ). The RF receiver 510 may receive an analog data unit from an RF transmitter (eg, the RF transmitter 320 of FIG. 3) of a transmission module. The RF receiver 510 may transmit an analog data unit to the baseband processor 520.

The baseband processing unit 520 may receive an analog data unit from the RF receiver 510. The baseband processor 520 may process the data unit to obtain data. Meanwhile, the baseband processing unit 520 may be configured as follows.

6 is a block diagram showing a first embodiment of a baseband processing unit included in a receiving module in a communication system.

The baseband processing unit 600 includes an analog-to-digital conversion unit 605, a demodulation unit 610, an equalizer 615, a frequency offset estimation unit 620, a frequency offset compensation unit 625, and a serial/parallel conversion unit 630. , A CP removal unit 635, a Fast Fourier Transform (FFT) unit 640, a demapping unit 645, a bottle/serial transform unit 650, and a decoding unit 655. The baseband processing unit 600 of FIG. 6 may be configured to be the same as or similar to the baseband processing unit 520 of FIG. 5.

The analog-to-digital conversion unit 605 may receive an analog data unit from an RF receiver (eg, the RF receiver 510 of FIG. 5 ). The analog-to-digital conversion unit 605 may convert an analog data unit into a digital data unit. The analog-to-digital conversion unit 605 may transmit a digital data unit to the demodulation unit 610.

The demodulation unit 610 may receive a digital data unit from the analog-to-digital conversion unit 605. The demodulation unit 610 may demodulate a digital data unit. The demodulation unit 610 may transmit the demodulated data unit to the equalizer 615.

The equalizer 615 may receive the demodulated data unit from the demodulation unit 610. The equalizer 615 may synchronize the demodulated data units. The equalizer 615 may estimate a channel characteristic between the transmission module (eg, the transmission module 300 of FIG. 3) and the reception module (eg, the reception module 500 of FIG. 5) from the data unit. . The equalizer 615 may synchronize data units based on the estimated channel characteristics. The equalizer 615 may transmit the synchronized data unit to the frequency offset estimation unit 620 and the frequency offset compensation unit 625.

The frequency offset estimation unit 620 may receive a data unit in which synchronization has been performed from the equalizer 615. The frequency offset estimation unit 620 may estimate an integer multiple frequency offset (Carrier Frequency Offset, CFO) generated in the data unit.

The frequency offset estimation unit 620 may obtain an original CP based on a first OFDM symbol, which is one of OFDM symbols included in the data unit. The original CP can be expressed as in Equation 1 below.

은 상기 제1 OFDM 심볼을 구성하는 원시 CP를 나타낼 수 있고,

는 제1 OFDM 심볼의 기저 대역 신호일 수 있다. 원시 CP의 FFT 크기가

인 경우, n은 1부터

가운데 어느 하나일 수 있다. 또한, N은 데이터 심볼(예를 들어, 제1 OFDM 심볼에서 원시 CP를 제외한 부분)의 FFT 크기일 수 있고,

는 데이터 유닛의 소수배 주파수 오프셋(Fractional Frequency Offset, FFO)일 수 있다. 한편,

는 다음 수학식 2에 의해 획득할 수 있다.In Equation 1,

May represent the original CP constituting the first OFDM symbol,

May be a baseband signal of the first OFDM symbol. The FFT size of the raw CP is

In the case of, n is from 1

It can be any one of them. In addition, N may be the FFT size of the data symbol (eg, the portion excluding the original CP in the first OFDM symbol),

May be a fractional frequency offset (FFO) of the data unit. Meanwhile,

Can be obtained by the following equation (2).

는 오프셋 주파수일 수 있고,

는 데이터 유닛의 중심 주파수 변화량일 수 있다.

은 수신 모듈(예를 들어, 도 5의 수신 모듈(500))의 이동에 의해 발생하는 도플러 효과를 나타내는 주파수일 수 있다.In Equation 2,

May be the offset frequency,

May be the amount of change in the center frequency of the data unit.

May be a frequency representing the Doppler effect generated by the movement of the receiving module (eg, the receiving module 500 of FIG. 5 ).

The frequency offset estimation unit 620 may obtain a reference CP based on the first OFDM symbol constituting the data unit. The reference CP can be expressed as Equation 3 below.

는 제1 OFDM 심볼을 구성하는 참조 CP를 나타낼 수 있고,

는 제1 OFDM 심볼의 기저대역 신호일 수 있다. 참조 CP의 FFT 크기가

인 경우, n은 1부터

가운데 어느 하나일 수 있다.In Equation 3,

May represent a reference CP constituting the first OFDM symbol,

May be a baseband signal of the first OFDM symbol. The FFT size of the reference CP is

In the case of, n is from 1

It can be any one of them.

The frequency offset estimation unit 620 may estimate an integer multiple frequency offset of the data unit based on the original CP and the reference CP. The frequency offset estimation unit 620 may estimate an integer multiple frequency offset of the data unit based on Equation 4 below.

는 데이터 유닛의 정수배 주파수 오프셋 추정 값일 수 있다. 즉, 주파수 오프셋 추정부는 원시 CP의 켤레 복소수를 획득할 수 있다. 주파수 오프셋 추정부는 원시 CP의 켤레 복소수와 원시 CP에 대응하는 참조 CP를 곱하고, 곱한 결과의 평균 값을 연산하여 정수배 주파수 오프셋 추정 값인

을 획득할 수 있다. 주파수 오프셋 추정 유닛(620)은 데이터 유닛의 정수배 주파수 오프셋 추정 값인

을 주파수 오프셋 보상 유닛(625)에 전송할 수 있다.In Equation 4,

May be an integer multiple frequency offset estimation value of the data unit. That is, the frequency offset estimator may obtain a complex conjugate of the original CP. The frequency offset estimator multiplies the complex conjugate of the original CP and the reference CP corresponding to the original CP, and calculates the average value of the multiplication result,

Can be obtained. The frequency offset estimation unit 620 is an integer multiple frequency offset estimation value of the data unit.

May be transmitted to the frequency offset compensation unit 625.

을 수신할 수 있다. 주파수 오프셋 보상 유닛(625)은 데이터 유닛의 정수배 주파수 오프셋을 보상할 수 있다. 주파수 오프셋 보상 유닛(625)은 아래 수학식 5를 기초로 데이터 유닛의 정수배 주파수 오프셋을 보상할 수 있다.The frequency offset compensation unit 625 may receive a data unit in which synchronization has been performed from the equalizer 615. In addition, the frequency offset compensation unit 625 is an integer multiple frequency offset estimation value of the data unit from the frequency offset estimation unit 620

Can be received. The frequency offset compensation unit 625 may compensate for an integer multiple frequency offset of the data unit. The frequency offset compensation unit 625 may compensate for an integer multiple frequency offset of the data unit based on Equation 5 below.

는 정수배 주파수 오프셋이 보상된 데이터 유닛일 수 있다. 제1 OFDM 심볼의 원시 CP의 FFT 크기가

이고, 데이터 심볼의 FFT크기가

인 경우, 수학식 5의 n은 0 내지

가운데 어느 하나일 수 있다.In Equation 5,

May be a data unit in which an integer multiple frequency offset is compensated. The FFT size of the original CP of the first OFDM symbol is

And the FFT size of the data symbol is

In the case of, n in Equation 5 is 0 to

It can be any one of them.

The frequency offset compensation unit 625 may transmit the data unit for which the integer multiple frequency offset is compensated to the serial/parallel conversion unit 630. The serial/parallel conversion unit 630 may receive a data unit in which an integer multiple frequency offset is compensated from the frequency offset compensation unit 625. The serial/parallel conversion unit 630 may convert a serial type data unit into a parallel type data unit. The serial/parallel conversion unit 630 may transmit a parallel data unit to the CP removal unit 635.

The CP removal unit 635 may receive a parallel data unit from the serial/parallel conversion unit 630. The CP removal unit 635 may remove the original CP inserted into each of the OFDM symbols of the data unit. The CP removal unit 635 may transmit a data unit including OFDM symbols from which the original CP has been removed to the FFT unit 640.

The FFT unit 640 may receive a data unit including OFDM symbols from which the original CP has been removed from the CP removal unit 635. The FFT unit 640 may convert OFDM symbols in the time domain into OFDM symbols in the frequency domain using a Fast Fourier Transform (FFT) scheme. The FFT unit 640 may transmit OFDM symbols converted to the frequency domain to the demapping unit 645.

The demapping unit 645 may receive a data unit including OFDM symbols converted to the frequency domain from the FFT unit 640. The demapping unit 645 may perform a demapping operation on OPDM data symbols. The demapping unit 645 may transmit the data unit including the demapped OFDM symbols to the parallel/serial conversion unit 650.

The parallel/serial conversion unit 650 may receive a data unit including the demapped OFDM symbols from the demapping unit 645. The parallel/serial conversion unit 650 may convert parallel OFDM symbols into a serial format. The parallel/serial conversion unit 650 may transmit a data unit including serial OFDM symbols to the decoding unit 655.

The decoding unit 655 may receive a data unit including serial OFDM symbols from the parallel/serial conversion unit 650. The decoding unit 655 may obtain data by decoding the data unit.

7 is a flow chart showing a first embodiment of a method of transmitting and receiving data in a communication system.

Referring to FIG. 7, the communication system may include a first communication node and a second communication node. The first communication node may be the first communication node 110 illustrated in FIG. 1, and the second communication node may be the second communication node 120 illustrated in FIG. 1. Each of the first communication node and the second communication node may be configured in the same or similar to the communication node 200 illustrated in FIG. 2. The transmission module included in each of the first communication node and the second communication node may be configured in the same or similar to the embodiments shown in FIGS. 3 and 4. The receiving module included in each of the first communication node and the second communication node may be configured in the same or similar to the embodiments shown in FIGS. 5 and 6.

The first communication node may generate a data unit (S710). The baseband processing unit (eg, the baseband processing unit 310 of FIG. 3) of the first communication node may modulate the baseband signals using the OFDM method. The baseband processor may generate a data unit based on signals modulated by the OFDM scheme.

The first communication node may transmit the data unit to the second communication node (S720). The first communication node may transmit the data unit to the second communication node through the RF transmitter (eg, the RF transmitter 320 of FIG. 3 ).

The second communication node may receive a data unit from the first communication node (S720). The second communication node may receive the data unit through an RF receiver (eg, the RF receiver 510 of FIG. 5 ).

The second communication node may estimate an integer multiple frequency offset of the received data unit (S730). The baseband processing unit (eg, the baseband processing unit 520 of FIG. 5) of the second communication node may estimate an integer multiple offset of the data unit based on the original CP and the reference CP of the OFDM symbol included in the data unit. .

The baseband processor may obtain the original CP of the first OFDM symbol, which is one of a plurality of OFDM symbols included in the data unit, through Equation 1 of FIG. 6. A reference CP of a rear end of the first OFDM symbol may be obtained through Equation 3 of FIG. 6. The baseband processor may calculate an estimated value of an integer multiple frequency offset of the data unit through Equation 4 of FIG. 6.

The baseband processor may obtain complex conjugates of the original CP, and multiply the complex conjugates with a reference CP corresponding to each original CP. The baseband processor may calculate an average value of the multiplication result to obtain an estimated value of an integer multiple frequency offset of the data unit.

The second communication node may compensate for the integer multiple frequency offset of the data unit based on the estimated value of the integer multiple frequency offset (S740). The baseband processor may compensate for an integer multiple frequency offset of the data unit based on Equation 5 of FIG. 6. The baseband processor may compensate for the integer multiple frequency offset of the data unit by multiplying the data unit by the integer multiple frequency offset estimate value.

The second communication node may acquire data based on the data unit for which the integer multiple frequency offset is compensated (S750). The baseband acquisition unit of the second communication node may acquire data by decoding the data unit for which the frequency offset is compensated.

example The methods according to the invention may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like alone or in combination. The program instructions recorded on the computer-readable medium may be specially designed and configured for the present invention, or may be known and usable to those skilled in computer software.

Examples of computer-readable media include hardware devices specially configured to store and execute program instructions, such as rom, ram, flash memory, and the like. Examples of program instructions include not only machine language codes such as those produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The above-described hardware device may be configured to operate as at least one software module to perform the operation of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention described in the following claims. I will be able to.

Claims (8)

As a method of operating a first communication node in a communication system,
Receiving a data unit including a plurality of orthogonal frequency division modulation (OFDM) symbols from a second communication node;
Obtaining an original cyclic prefix (CP) from a first OFDM symbol that is any one of a plurality of OFDM symbols constituting the data unit;
Obtaining a reference CP constituting a rear end of the first OFDM symbol;
Calculating an integer multiple frequency offset estimation value of the data unit using the original CP and the reference CP; And
Compensating for an integer multiple frequency offset of the data unit based on the estimated value,
The integer multiple frequency offset estimation value of the data unit is calculated by the following equation,

remind

Is an integer multiple frequency offset estimate value of the data unit, wherein

Is the FFT (Fast Fourier Transform) size of the original CP, and

Is the raw CP, and

Is the reference CP, the operating method of the first communication node. The method according to claim 1,
The step of obtaining the original CP,
The first communication, characterized in that the step of obtaining a signal for the original CP based on the fractional frequency offset of the data unit, the FFT (Fast Fourier Transform) size of the first OFDM symbol, and the FFT size of the original CP How the node works. The method according to claim 1,
The step of obtaining the reference CP,
And obtaining the reference CP based on the fractional frequency offset of the data unit, the FFT size of the first OFDM symbol, and the FFT size of the reference CP. delete The method according to claim 1,
Compensating for the integer multiple frequency offset,
And compensating for an integer multiple frequency offset of the data unit by multiplying the data unit by the integer multiple frequency offset estimation value. As the first communication node of the communication system,
Processor; And
Includes a memory (memory) in which one or more instructions executed by the processor are stored,
The one or more commands,
Receive a data unit including a plurality of orthogonal frequency division modulation (OFDM) symbols from a second communication node;
Acquiring an original CP (Cyclic Prefix) of a first OFDM symbol, which is any one of a plurality of OFDM symbols constituting the data unit;
Acquiring a reference CP constituting a rear end of the first OFDM symbol;
Calculate an integer multiple frequency offset estimation value of the data unit based on the original CP and the reference CP; And,
Compensating for an integer multiple frequency offset of the data unit based on the estimated value,
The integer multiple frequency offset estimation value of the data unit is calculated by the following equation,

remind

Is an integer multiple frequency offset estimate value of the data unit, wherein

Is the FFT (Fast Fourier Transform) size of the original CP, and

Is the raw CP, and

Is the reference CP, the first communication node. The method of claim 6,
When obtaining the raw CP,
The one or more commands,
A first communication node executed to obtain a signal for the original CP based on a fractional frequency offset of the data unit, a Fast Fourier Transform (FFT) size of the first OFDM symbol, and an FFT size of the original CP. delete

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