KR20190029352A - Apparatus and method for estimating frequency offset in ofdm/ofdma system - Google Patents

Abstract

According to an embodiment of the present invention, a method for estimating frequency offset in time domain of an orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA) OFDM/OFDMA system comprises the steps of: receiving a signal according to the OFDM / OFDMA scheme; dividing a cyclic prefix section in a k^th OFDM symbol of the received signal; calculating a correlation between the OFDM symbols by using only a part of the divided cyclic prefix sections; and estimating a frequency offset for the received signal based on the calculated correlation.

Description

[0001] APPARATUS AND METHOD FOR ESTIMATING FREQUENCY OFFSET IN OFDM / OFDMA SYSTEM [0002]

TECHNICAL FIELD The present invention relates to an apparatus and method for estimating frequency offset in an OFDM / OFDMA system, and more particularly, to an apparatus and method for estimating a frequency offset using a cyclic prefix.

An OFDM (Orthogonal Frequency Division Multiplexing) / OFDMA (Orthogonal Frequency Division Multiple Access) scheme is a modulation scheme for multiplexing a high-speed transmission signal with a plurality of orthogonal narrow-band carriers.

The communication system using the OFDM / OFDMA scheme has high frequency efficiency due to the use of an orthogonal carrier, has a strong advantage against multipath fading, and can easily change the transmission rate adaptively according to the environment. It is widely used.

The OFDM / OFDMA system is very sensitive to a frequency offset due to a Doppler shift caused by an oscillator error and a mobility of the UE.

In addition, frequency offset causes inter-carrier interference, which degrades the performance of the system.

Thus, the OFDM / OFDMA system requires estimation and compensation for frequency offset to maintain orthogonality between subcarriers.

An apparatus and method for estimating frequency offset in an OFDM / OFDMA system according to the technical idea of the present invention is to provide a method of estimating a frequency offset in a time domain.

It is another object of the present invention to provide a frequency offset estimation apparatus and method that can overcome estimation performance deterioration even when there is an OFDM symbol boundary error.

According to an aspect of the present invention, there is provided a frequency offset estimation method comprising: receiving a signal according to an OFDM / OFDMA scheme; Dividing a cyclic prefix section in a kth OFDM symbol of the received signal; Calculating a correlation between the OFDM symbols using only a part of the divided cyclic prefix intervals; And estimating a frequency offset for the received signal based on the calculated correlation.

According to an exemplary embodiment, the step of calculating the correlation between the OFDM symbols using only the partial interval may include calculating the correlation between the OFDM symbols using only the samples corresponding to some intervals of the cyclic prefix interval .

According to an exemplary embodiment, the k-th OFDM symbol may be an OFDM symbol to which only a reference signal is allocated.

According to an exemplary embodiment, the k-th OFDM symbol may be an OFDM symbol corresponding to a preamble. According to an exemplary embodiment of the present invention, the step of calculating the correlation between the OFDM symbols using only the partial interval may include using only samples corresponding to the remaining intervals except for the first interval having the first length from the start interval of the cyclic prefix interval , And calculating a correlation between the OFDM symbols.

According to an exemplary embodiment of the present invention, the step of calculating the correlation between the OFDM symbols using only the partial interval corresponds to the remaining interval excluding the second interval corresponding to the second length from one period to the finishing interval of the cyclic prefix interval And calculating a correlation between the OFDM symbols using only the samples that are obtained from the OFDM symbol.

According to an exemplary embodiment of the present invention, the step of calculating the correlation between the OFDM symbols using only the partial interval includes a first interval having a first length from a start interval of the cyclic prefix interval and a first interval having a first length, And calculating a correlation between the OFDM symbols using only samples corresponding to the remaining intervals except the second interval corresponding to the second length of the OFDM symbol.

According to an exemplary embodiment, the first length and the second length may be different lengths.

According to an exemplary embodiment, the method may further include adjusting a length of the partial section according to a communication state and environment of the terminal receiving the signal.

According to an exemplary embodiment, the communication state and environment of the terminal may include at least one of a symbol boundary update period according to the communication of the OFDM scheme and a movement speed of the terminal.

According to another aspect of the present invention, there is provided a frequency offset estimation apparatus comprising: at least one processor; And a memory electrically coupled to the processor, wherein the processor is operative to receive a signal according to an OFDM / OFDMA scheme at execution time and to generate a cyclic prefix in the kth OFDM symbol of the received signal, To calculate a correlation between the OFDM symbols using only a part of the divided cyclic prefix intervals and to estimate a frequency offset for the received signal based on the calculated correlation, have.

According to an exemplary embodiment, the memory may store instructions that, when executed, cause the processor to calculate a correlation between the OFDM symbols using only samples corresponding to some of the intervals of the cyclic prefix period.

According to an exemplary embodiment, the k-th OFDM symbol may be an OFDM symbol to which only a reference signal is allocated.

According to an exemplary embodiment, the k-th OFDM symbol may be an OFDM symbol corresponding to a preamble.

According to an exemplary embodiment, the memory may be configured such that, when the processor is executed, only a sample corresponding to a remaining section excluding a first section having a first length from a start section of the cyclic prefix section is used, And store the instructions to calculate the correlation.

According to an exemplary embodiment, the memory uses only samples corresponding to the remaining sections except for the second section corresponding to the second length from one section of the cyclic prefix section to the end section at the time of execution of the processor , And may store instructions to calculate the correlation between the OFDM symbols.

According to an exemplary embodiment, the memory is configured such that when the processor is in operation, a first interval having a first length from a start interval of the cyclic prefix interval, and a second interval from one interval to the end interval of the cyclic prefix And store the instructions to calculate the correlation between the OFDM symbols using only the samples corresponding to the remaining intervals except for the corresponding second interval.

According to an exemplary embodiment, the first length and the second length may be different lengths.

According to an exemplary embodiment, the memory may store instructions that, when executed, cause the processor to adjust the length of the partial interval according to the communication state and environment of the terminal receiving the signal.

According to an exemplary embodiment, the communication state and environment of the terminal may include at least one of a symbol boundary update period according to the communication of the OFDM scheme and a movement speed of the terminal.

The frequency offset estimation method and apparatus according to embodiments of the present invention can accurately estimate the frequency offset in the time domain.

Also, even if there is an OFDM symbol boundary error, the present invention can improve the frequency offset estimation performance and reduce the calculation amount for estimation.

BRIEF DESCRIPTION OF THE DRAWINGS A brief description of each drawing is provided to more fully understand the drawings recited in the description of the invention.
1 is a conceptual diagram of a communication system according to an embodiment of the present invention.
2 is a block diagram illustrating a configuration of a communication node according to various embodiments of the present invention.
3 shows a structure of an OFDM / OFDMA symbol according to various embodiments of the present invention.
4 is a flowchart of a frequency offset estimation method according to various embodiments of the present invention.
5 is a conceptual diagram of a usage period of a cyclic prefix according to various embodiments of the present invention.
6 to 7 show simulation results on frequency offset estimation according to various embodiments of the present invention.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. However, it should be understood that the technical idea of the present invention is not limited to the specific embodiments but includes all changes, equivalents, and alternatives included in the technical idea of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0029] In the following description of the present invention, a detailed description of known technologies will be omitted when it is determined that the gist of the present invention may be unnecessarily obscured. In addition, numerals (e.g., first, second, etc.) used in the description of the present invention are merely an identifier for distinguishing one component from another.

Also, in this specification, when an element is referred to as being "connected" or "connected" with another element, the element may be directly connected or directly connected to the other element, It should be understood that, unless an opposite description is present, it may be connected or connected via another element in the middle.

The terms "to", "to", "to", "to", and "module" in the present specification mean units for processing at least one function or operation, A micro processor, a central processing unit (CPU), a graphics processing unit (GPU), an Accelerate Processor Unit (APU), a digital signal processor (DSP), an application specific integrated circuit (ASIC) (Field Programmable Gate Array), or the like, or a combination of hardware and software.

It is to be clarified that the division of constituent parts in this specification is merely a division by each main function of each constituent part. That is, two or more constituent parts to be described below may be combined into one constituent part, or one constituent part may be divided into two or more functions according to functions that are more subdivided. In addition, each of the constituent units described below may additionally perform some or all of the functions of other constituent units in addition to the main functions of the constituent units themselves, and that some of the main functions, And may be carried out in a dedicated manner.

Hereinafter, embodiments according to the technical idea of the present invention will be described in detail.

1 is a conceptual diagram of a communication system according to an embodiment of the present invention.

Referring to FIG. 1, the communication system 10 may include a first communication node 50 and a second communication node 80. Where the second communication node 80 may include a plurality of second communication nodes 80a-80n.

The first communication node 50 and the second communication node 80 can perform wireless communication with each other.

According to various embodiments, the communication system 10 may be implemented in an Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) communication system. Hereinafter, OFDM / OFDMA will be described as OFDM only.

According to the embodiment, the first communication node 50 is implemented as a base station, and each of the plurality of second communication nodes 80a to 80n may be implemented as a wireless communication terminal.

For example, a downlink communication can be performed from the first communication node 50 to each of the plurality of second communication nodes 80a to 80n, and a plurality of second communication nodes Uplink communication to transmit data from each of the first communication node 50a to the first communication node 50 may be performed.

The configuration of a communication node according to various embodiments of the present invention will be described with reference to FIG.

2 is a block diagram illustrating a configuration of a communication node according to various embodiments of the present invention.

Referring to FIG. 2, the communication node 100 may include a processor 110, a memory 130, and a communication module 180.

The processor 110 may control the overall operation of the communication node 100.

The processor 110 may perform operations performed by the configurations included in the transmitter and perform operations performed by the configurations included in the receiver.

For example, the processor 110 may execute instructions stored in the memory 130 to perform operations performed by configurations included in at least one of a transmitting end and a receiving end included in the communication system 10. [

The memory 130 may store various information.

For example, the memory 130 may store instructions for performing operations performed by the configurations included in at least one of the transmitting end and the receiving end.

The communication module 180 can transmit and receive signals through wireless communication.

At least one of the first communication node 50 and the second communication node 80 may be configured in the same manner as the communication node 100 described above. The communication node 100 may include a frequency offset estimation apparatus according to the present invention, or may be a frequency offset estimation apparatus.

The communication node 100 may include a channel encoding module, a modulation module, a mapping module, an IFFT module, a CP insertion module, an LPF, a DAC, and a transmission module when the communication node 100 operates as a transmitting terminal.

The channel encoding module may add bits for error detection and correction.

The modulation module may perform digital modulation on a bit stream that is the result of channel encoding.

The mapping module may assign the digital modulated result per burst to a subcarrier according to the control of the scheduler.

 The IFFT module can perform Inverse Fast Fourier Transform (IFFT) on subcarriers.

The CP insertion module can insert CP (Cyclic Prefix) in the guard interval.

The LPF (Low Pass Filter) can perform low pass filtering.

A digital to analog converter (DAC) can convert a digital signal to an analog signal.

The transmitting module can transmit the converted analog signal.

The transmitting end may further include various configurations other than the above-described configuration.

The communication node 100 may perform the operations performed by the modules of the above-described transmitting terminal with the instructions executed by the processor 110 and the memory 130. [

The communication node 100 may include a receiving module, an ADC, an LPF, a CP removal module, an FFT module, a demapping module, an equalizer, and a channel decoding module when operating as a receiving end.

The receiving module can receive the transmitted analog signal.

An analog to digital converter (ADC) can convert an analog signal to a digital signal.

The LPF (Low Pass Filter) can perform low pass filtering.

The CP removal module can remove the CP (Cyclic Prefix) of the guard interval.

The FFT module can perform an FFT (Fast Fourier Transform) operation.

The demapping module may perform a reverse process of the mapping block performed by the transmitting end. For example, it can perform the inverse process of the process performed by the mapping module.

The equalizer can compensate for distortion on the wireless channel.

The receiving end may further include various configurations other than the above-described configuration.

The communication node 100 may perform the operations performed by the modules of the receiving terminal described above with the instructions executed by the processor 110 and the memory 130. [

The structure of the OFDM / OFDMA symbol will be described with reference to FIG.

3 shows a structure of an OFDM / OFDMA symbol according to various embodiments of the present invention.

Referring to FIG. 3, the OFDM symbol 200 includes a cyclic prefix 210 and an effective symbol interval 250. The valid symbol interval 250 may be referred to as a data interval.

The cyclic prefix 210 included in the OFDM symbol 200 may have a length of L samples and the effective symbol interval 250 may have a length of N samples. The total length of the OFDM symbol 200 may have a length of L + N samples.

Here, the length of the sample may mean the size.

The guard interval is inserted in the OFDM symbol 200 to remove the inter-symbol interference.

Specifically, the guard interval of the OFDM symbol 200 is copied to the last part of the OFDM symbol 200, the copy target interval 290, and the first part of the OFDM symbol 200, the cyclic prefix 210 ).

The cyclic prefix 210 and the copy target section 290 may be the same length or the same size since the cyclic prefix 210 is a section in which the copy target section 290 is copied. Here, the cyclic prefix 210 may be referred to as a guard interval.

The communication node 100 in accordance with various embodiments of the present invention may estimate the frequency offset based on the cyclic prefix 210 included in the OFDM symbol 200.

Specifically, the communication node 100 can estimate a frequency offset using the same property of the cyclic prefix 210 and the copy subject interval 290.

For example, the received signal of the k-th OFDM symbol can be defined as follows.

The communication node 100 may calculate the correlation in the kth OFDM symbol using the following equation.

I is the sample index, and y _{( k, i )} is the length of the kth OFDM symbol _{( i, j )} , where N is the Discrete Fourier Transform (FFT) / Fast Fourier Transform (FFT) size, L is the length of the cyclic prefix Denotes the i-th received sample signal in the symbol.

The communication node 100 can calculate the phase of a unit such as a frame or a sub-frame from the correlation result calculated by the above equation using the following equation.

Where K is the number of OFDM symbols in the unit such as a frame or sub-frame, k is the OFDM symbol index, _k pd is the correlation value of the k-th OFDM symbol.

The communication node 100 can calculate the frequency offset using the following equation using the result calculated in the above process. Here, the frequency offset calculation may mean frequency offset estimation.

In the above procedure, the communication node 100 calculates the frequency offset using all of the cyclic prefixes 210 in the guard interval. If the samples used in the calculation are ideal for the OFDM symbol boundary determination, the communication node 100 estimates an accurate frequency offset . However, as described above, when there is an OFDM symbol boundary error, deterioration may occur in the frequency offset estimation performance. Accordingly, an apparatus and method for estimating a frequency offset according to various embodiments of the present invention can estimate a frequency offset using only a part of a cyclic prefix 210.

Specifically, in an actual system, an error may occur in OFDM symbol boundary determination. In order to overcome this error, in the present invention, only a part of the cyclic prefix 210 that can sufficiently guarantee the frequency offset estimation performance can be selected and used without using all the cyclic prefixes (CP) 210 in the guard interval. Here, the OFDM symbol boundary serving as a basis for selecting the interval may be a sample that is started at the end of the guard interval or the start sample of the guard interval. Since the frequency offset estimation uses the cyclic prefix 210 of the guard interval, the guard interval start sample can be regarded as the reference of the OFDM symbol boundary. Therefore, the OFDM symbol boundary error will occur around the start sample of the guard interval, and considering the signal reception through the multipath, the OFDM symbol boundary will be determined later than the start sample of the guard interval, except in special cases. Therefore, an apparatus and method for estimating a frequency offset according to various embodiments of the present invention can calculate a frequency offset considering only an OFDM symbol boundary error therebetween. In addition, the apparatus and method for estimating frequency offset according to various embodiments of the present invention may consider until the OFDM symbol boundary is determined earlier than the start sample of the guard interval.

Hereinafter, it will be described in detail.

4 is a flowchart of a frequency offset estimation method according to various embodiments of the present invention.

Referring to FIG. 4, the communication node 100 may receive a signal according to the OFDM / OFDMA scheme (S310).

The communication module 180 of the communication node 100 can receive a signal according to the OFDM / OFDMA scheme from another communication node.

The communication node 100 may identify the cyclic prefix 210 in the OFDM symbol 200 of the received signal (S320).

For example, the processor 110 of the communication node 100 may identify the cyclic prefix 210 interval in the kth OFDM symbol 200 of the received signal.

The communication node 100 may calculate the correlation between the OFDM symbols using only a part of the divided cyclic prefixes 210 (S330).

For example, the communication node 100 may use only a part of the divided cyclic prefix 210 that can sufficiently guarantee the frequency offset estimation performance.

In one embodiment, the processor 110 of the communication node 100 can calculate the correlation between OFDM symbols using only the remaining part of the cyclic prefix 210 excluding the section having a predetermined length from the start section.

In another embodiment, the processor 110 of the communication node 100 may calculate the correlation between OFDM symbols using only the remaining part of the cyclic prefix 210 excluding a section having a predetermined length from one section to the finishing section .

In another embodiment, the processor 110 of the communication node 100 includes a period having a certain length from the start interval of the cyclic prefix 210 and a certain interval from one interval to the end interval of the cyclic prefix 210, The correlation between the OFDM symbols can be calculated using only the remaining intervals.

This will be described in detail with reference to FIG.

5 is a conceptual diagram of a usage period of a cyclic prefix according to various embodiments of the present invention.

Referring to FIG. 5, the processor 110 of the communication node 100 can estimate a frequency offset using only the usage period 430, which is a partial interval of the whole interval of the cyclic prefix 210. [

Specifically, the processor 110 of the communication node 100 selects the first period 410 and the second period 410 from the start interval of the cyclic prefix 210 to the first interval 410 and the cyclic prefix 210, The OFDM symbol correlation can be calculated using the use period 430, which is the remaining period except for the second period 450 having the OFDM symbols. Here, the first length and the second length may be the same length or may be different lengths. Thus, the first section 410 and the second section 450 may have the same length or different lengths.

The first section 410 is an unused section on the left side with respect to the use section 430 and the second section 450 is an unused section on the right side based on the use section 430. [ The usage period 430 may have a length of the L _used sample, the first period 410 may have a length of L _{unused_l} samples, and the second period 450 may have a length of L _{unused_r} samples.

The length of the second interval 450 may be 0 according to an embodiment of the present invention so that the communication node 100 uses the remaining intervals 430 and 450 of the cyclic prefix 210 excluding the first interval 410 It is possible.

The received signal of the k-th OFDM symbol may be defined as follows.

The processor 110 of the communication node 100 can calculate the correlation in the kth OFDM symbol using the following equation.

Here, pd _k is a correlation result in the k-th OFDM symbol, i is a sample index, and y _{( k, i )} denotes an i-th received sample signal in the k-th OFDM symbol.

Meanwhile, the communication node 100 may adjust the length of the usage period 430 and calculate the correlation between OFDM symbols using the usage period 430 having the adjusted length. This will be described later.

Referring again to FIG.

The communication node 100 may calculate a frequency offset based on the calculated correlation (S340).

For example, the communication node 100 can calculate the phase of a unit such as a frame or a sub-frame from the calculated correlation result, and calculate the frequency offset using the calculated phase Can be calculated.

Specifically, the processor 110 of the communication node 100 calculates a phase of a unit such as a frame or a sub-frame from the correlation result calculated in step S330 using the following equation .

Where K is the number of OFDM symbols in the unit such as a frame or sub-frame, k is the OFDM symbol index, _k pd is the correlation value of the k-th OFDM symbol.

The processor 110 of the communication node 100 may calculate the frequency offset using the following equation using the result calculated in the above process. Here, the frequency offset calculation may mean frequency offset estimation.

As such, the communication node 100 according to various embodiments of the present invention may calculate frequency offsets in the time domain using only a fraction of the cyclic prefix 210. Thus, through the above-described process, the frequency estimation apparatus and method according to various embodiments of the present invention can estimate a frequency offset.

Meanwhile, the communication node 100 may calculate the frequency offset using the OFDM symbol to which only the reference signal is allocated. For example, the kth OFDM symbol described above may be a symbol allocated only to a reference signal.

Specifically, the communication node 100 can calculate the frequency offset using only the k-th OFDM symbol to which only the reference signal is allocated. The communication node 100 may calculate the frequency offset using only a part of the cyclic prefix 210 of the kth OFDM symbol to which only the reference signal is allocated. Here, some sections may refer to the usage section 430 described above. Therefore, the communication node 100 can perform the above-described S320 to S340 using only the kth OFDM symbol to which only the reference signal is allocated.

In one embodiment, the communication node 100 may calculate a frequency offset using only OFDM symbols to which only a reference signal such as a pilot signal, a sounding reference signal, or the like is allocated.

In another example, the communication node 100 may calculate a frequency offset using only OFDM symbols corresponding to a preamble.

As described above, the frequency offset estimation apparatus according to various embodiments of the present invention can calculate the frequency offset using only the use period 430 among the cyclic prefixes 210 of the OFDM symbol to which the reference signal is allocated. Therefore, the apparatus and method for estimating frequency offset according to various embodiments of the present invention can improve the frequency offset estimation performance and reduce the amount of calculation for frequency offset estimation.

The communication node 100 may calculate the frequency offset in the frequency domain (S350).

The communication node 100 may calculate frequency offsets in the frequency domain using a variety of known methods. The frequency offset calculation in the frequency domain requires more computation amount and computation time than the frequency offset calculation in the time domain, but a more accurate frequency offset can be obtained.

The processor 110 of the communication node 100 may calculate frequency offsets in the frequency domain for a predetermined period and under certain conditions.

The communication node 100 may compare the frequency offset calculated in the time domain with the frequency offset calculated in the frequency domain (S360).

The processor 110 of the communication node 100 may compare the frequency offset calculated in the time domain and the frequency offset calculated in the frequency domain using only a partial interval of the cyclic prefix 210 described above.

For example, the communication node 100 may compare frequency offsets calculated in the time domain and frequency offsets calculated in the frequency domain for a predetermined period and a predetermined condition.

The communication node 100 may adjust the length of a part of the cyclic prefix used in calculating the frequency offset in the time domain based on the comparison result (S370).

The processor 110 of the communication node 100 may adjust the length of the usage period 430 used in calculating the frequency offset in the time domain based on the comparison result in step S360. Accordingly, the communication node 100 can calculate a more accurate frequency offset using only a part of the cyclic prefix 210 in the time domain.

The frequency offset estimation apparatus according to various embodiments can adjust the length of the usage period 430 used in frequency offset calculation in the time domain according to communication environment, terminal conditions, and the like.

For example, if the communication node 100 has a preset reference or a predetermined environment, the size of the usage period used for frequency offset calculation in the cyclic prefix 210 can be adjusted. In one embodiment, the communication node 100 may use the cyclic prefix 210 used in frequency domain estimation in the time domain, in accordance with conditions for at least one of the symbol boundary update period, And the length of the second electrode 430 can be adjusted. Accordingly, the frequency offset estimation apparatus according to various embodiments of the present invention can provide more accurate results in frequency domain estimation in the time domain.

6 to 7, the mean error and mean square error (MSE) of the simulation result on the frequency offset estimation value according to the apparatus and method for estimating frequency offset according to various embodiments of the present invention will be described.

6 to 7 show simulation results on frequency offset estimation according to various embodiments of the present invention.

The simulation results of FIGS. 6 to 7 are the results obtained under the following experimental conditions.

Channel bandwidth: 10 MHz (DFT / FFT size: 1024)

CP length: 128

Lused: 64, Lunused_l and Lunused_r: 32

Resonant frequency: 2.3GHz

OFDM symbols: 27 (preamble allocation for first OFDM symbol)

Resource allocation: allocate resources only to 1/3 of all bandwidth

Wireless channel environment: AWGN, pedestrian movement (3km / h), vehicle movement (60km / h)

Frequency offset setting: + 2kHz

FIG. 6 shows the results of a frequency offset estimation method according to various embodiments of the present invention using only a partial period of a cyclic prefix under an AWGN (Additive White Gaussian Noise) environment.

More specifically, when the resource allocation is allocated only to the 1/3 band, the frequency offset estimation performance is improved in the case of using a partial interval of the cyclic prefix in all OFDM symbols and the partial interval of the cyclic prefix of the OFDM symbol allocated only the preamble. The results are compared and analyzed. In this case, it can be seen that the average error is similar in the case of using a partial interval of the cyclic prefix in all the OFDM symbols and the case of using a partial interval of the cyclic prefix of the OFDM symbol allocated only the preamble. It can be seen that the mean squared error (MSE) is better than using a fraction of the cyclic prefix of the OFDM symbol to which only the preamble is allocated, compared to using a fraction of the cyclic prefix of all the OFDM symbols. Thus, it can be seen that a stable frequency offset estimation performance can be secured even when various embodiments of the present invention are applied to an OFDM symbol to which a reference signal including a preamble occupying the same band is always allocated.

FIG. 7 shows an analysis in which the contents described in FIG. 6 are applied to an environment in which a receiving end moves. It can be confirmed that the same analysis result can be obtained even in a moving environment.

As described above, the frequency offset estimation according to the apparatus and method for estimating frequency offset according to various embodiments of the present invention can reduce the amount of calculation compared with the case using the entire cyclic prefix, and it can be confirmed that the frequency offset estimation accuracy is high. In addition, the frequency offset estimation according to the apparatus and method for estimating frequency offset according to various embodiments of the present invention can reduce the amount of computation and reduce frequency offset estimation in a mobile environment in which a terminal receiving a signal moves, It can be confirmed that the accuracy is high.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Various modifications and variations are possible.

10: Communication system
50: first communication node
80a to 80n: a second communication node
100: communication node
110: Processor
130: memory
180: Communication module
200: OFDM symbol
210: cyclic prefix
250: Effective symbol interval
290: copy destination section
410: First Section
430: Usage section
450: the second section

Claims (20)

A method for estimating a frequency offset on a time domain of an OFDM / OFDMA system,
Receiving a signal according to the OFDM / OFDMA scheme;
Dividing a cyclic prefix section in a kth OFDM symbol of the received signal;
Calculating a correlation between the OFDM symbols using only a part of the divided cyclic prefix intervals; And
And estimating a frequency offset for the received signal based on the calculated correlation
Frequency offset estimation method.
The method according to claim 1,
The step of calculating the correlation between the OFDM symbols using only the partial interval
And calculating a correlation between the OFDM symbols using only samples corresponding to some intervals of the cyclic prefix interval
Frequency offset estimation method.
The method according to claim 1,
The k < th > OFDM symbol is an OFDM symbol allocated only a reference signal
Frequency offset estimation method.
The method according to claim 1,
The k-th OFDM symbol is an OFDM symbol corresponding to a preamble
Frequency offset estimation method.
The method according to claim 1,
The step of calculating the correlation between the OFDM symbols using only the partial interval
Calculating a correlation between the OFDM symbols using only the samples corresponding to the remaining sections excluding the first section having the first length from the start section of the cyclic prefix section
Frequency offset estimation method.
The method according to claim 1,
The step of calculating the correlation between the OFDM symbols using only the partial interval
Calculating a correlation between the OFDM symbols using only the samples corresponding to the remaining sections excluding the second section corresponding to the second length from one section to the end section of the cyclic prefix section
Frequency offset estimation method.
The method according to claim 1,
The step of calculating the correlation between the OFDM symbols using only the partial interval
Using only samples corresponding to a first section having a first length from a start section of the cyclic prefix section and a second section excluding a second section corresponding to a second length from one section to the end section of the cyclic prefix, Calculating a correlation between OFDM symbols;
Frequency offset estimation method.
8. The method according to any one of claims 5 to 7,
Wherein the first length and the second length are different lengths
Frequency offset estimation method.
The method according to claim 1,
And adjusting the length of the partial section according to the communication state and environment of the terminal receiving the signal
Frequency offset estimation method.
10. The method of claim 9,
The communication state and environment of the terminal
A symbol boundary update period according to the communication of the OFDM scheme, and a movement speed of the mobile station
Frequency offset estimation method.
An apparatus for estimating a frequency offset in a time domain of an OFDM / OFDMA system,
At least one processor; And
A memory electrically coupled to the processor,
The memory may be configured such that,
Receiving a signal according to the OFDM / OFDMA scheme,
A Cyclic Prefix (Cyclic Prefix) interval is discriminated in a kth OFDM symbol of the received signal,
Calculating a correlation between the OFDM symbols using only a part of the divided cyclic prefix intervals,
And based on the calculated correlation, storing instructions for estimating a frequency offset for the received signal
Frequency offset estimator.
12. The method of claim 11,
The memory may be configured such that,
And storing instructions for calculating a correlation between the OFDM symbols using only samples corresponding to some intervals of the cyclic prefix interval
Frequency offset estimator.
12. The method of claim 11,
The k < th > OFDM symbol is an OFDM symbol allocated only a reference signal
Frequency offset estimator.
12. The method of claim 11,
The k-th OFDM symbol is an OFDM symbol corresponding to a preamble
Frequency offset estimator.
12. The method of claim 11,
The memory may be configured such that,
Storing instructions for calculating a correlation between the OFDM symbols using only samples corresponding to the remaining sections except for a first section having a first length from a start section of the cyclic prefix section
Frequency offset estimator.
12. The method of claim 11,
The memory may be configured such that,
And storing the instructions for calculating the correlation between the OFDM symbols using only samples corresponding to the remaining sections excluding the second section corresponding to the second length from one section to the end section of the cyclic prefix section
Frequency offset estimator.
12. The method of claim 11,
The memory may be configured such that,
Using only samples corresponding to a first section having a first length from a start section of the cyclic prefix section and a second section excluding a second section corresponding to a second length from one section to the end section of the cyclic prefix, ≪ RTI ID = 0.0 > OFDM < / RTI &
Frequency offset estimator.
18. The method according to any one of claims 15 to 17,
Wherein the first length and the second length are different lengths
Frequency offset estimator.
12. The method of claim 11,
The memory may be configured such that,
And storing instructions for adjusting the length of the partial section according to the communication state and environment of the terminal receiving the signal
Frequency offset estimator.
20. The method of claim 19,
The communication state and environment of the terminal
A symbol boundary update period according to the communication of the OFDM scheme, and a movement speed of the mobile station
Frequency offset estimator.

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