KR20080010069A - Apparatus and method for communicating uplink data in wireless communication system - Google Patents

Abstract

An apparatus and a method for communicating uplink data in a wireless communication system are provided to save the energy required for uplink transmission by partially transmitting the sample data of an OFDMA(Orthogonal Frequency Division Multiple Access) symbol during the uplink transmission. An apparatus for communicating uplink data in a wireless communication system includes an index generator(505), a pilot symbol mapper(509), a data symbol mapper(507), an IFFT(Inverse Fast Fourier Transform) calculator(511), and a transmitting unit. The index generator calculates and generates a sub carrier index for mapping a transmission packet signal into a sub carrier at a predetermined interval. The pilot symbol mapper performs mapping of a pilot symbol into the corresponding sub carrier according to the sub carrier index in the predetermined front period of a packet signal transmission period. The data symbol mapper performs mapping of a data symbol into the corresponding sub carrier according to the sub carrier index in the predetermined rear period of the packet signal transmission period. The IFFT calculator performs the IFFT of the mapped pilot symbol and data symbol, and generates sample data. The transmitting unit extracts and transmits the predetermined part of the sample data of each OFDMA symbol from the IFFT processor.

Description

Device and method for uplink data communication in wireless communication system {APPARATUS AND METHOD FOR COMMUNICATING UPLINK DATA IN WIRELESS COMMUNICATION SYSTEM}

1 is a diagram illustrating a rule for allocating pilot symbols and data symbols on a time-frequency domain in a broadband wireless communication system according to an embodiment of the present invention.

2 is a diagram illustrating a method for selecting and transmitting some of sample data corresponding to one OFDMA symbol in a broadband wireless communication system according to an exemplary embodiment of the present invention.

3 is a view showing a plurality of user signals transmitted during one OFDMA symbol period in a broadband wireless communication system according to an embodiment of the present invention.

4 is a diagram illustrating a plurality of packet signals received during one OFDMA symbol period at a receiving end in a broadband wireless communication system according to an exemplary embodiment of the present invention.

5 is a diagram illustrating a configuration of a transmitter in a broadband wireless communication system according to an embodiment of the present invention.

6 is a diagram illustrating a configuration of a receiver in a broadband wireless communication system according to an embodiment of the present invention.

FIG. 7 is a diagram showing a detailed configuration of the offset estimator 607 described in FIG.

8 is a diagram illustrating a packet signal transmission procedure of a transmitter in a broadband wireless communication system according to an embodiment of the present invention.

9 is a diagram illustrating a packet signal receiving procedure of a receiver in a broadband wireless communication system according to an embodiment of the present invention.

10 is a diagram illustrating a process of restoring an offset-corrected received signal to an FFT input signal in a receiver according to an embodiment of the present invention.

The present invention relates to an apparatus and method for uplink data communication in a wireless communication system, and more particularly, to an apparatus and method for estimating an uplink frequency offset.

Today, many wireless communication technologies have been proposed as candidates for high speed mobile communication. Among them, orthogonal frequency division multiplexing (OFDM) is recognized as the most powerful next generation wireless communication technology. In most wireless communication technologies expected around 2010, the OFDM technology is expected to be used, and the OFDM (or OFDMA) technology is adopted as a standard in the IEEE 802.16 series Wireless Metropolitan Area Network (WMAN), which is now called 3.5 generation technology. Doing.

Since the performance of the OFDM communication system is greatly affected by the frequency offset, many studies have been made to solve this problem. However, most of the studies assume a downlink situation in which a terminal receives a signal broadcast from a base station and processes the signal, and a method of estimating and correcting the frequency offset assuming an uplink situation is still insignificant.

Unlike downlink, since uplink signals are received by adding multiple user signals, it is impossible to directly apply the existing frequency offset estimation and correction techniques studied on the downlink to uplink. Therefore, there is a theoretical attempt to apply the existing downlink frequency offset estimation method to create a downlink-like situation by allowing users to use different bands and then filter by band to separate the signals for each user. However, this method has a problem that is difficult to implement in reality because it requires as many users as the number of filters for finely separating the bands.

As described above, conventionally, there is no technique for estimating an uplink frequency offset. In particular, in the OFDM-based system, since frequency synchronization is important, a technique for estimating uplink frequency offset is urgently required.

Accordingly, an object of the present invention is to provide an apparatus and method for uplink data communication in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and method for estimating and correcting an uplink time offset in a broadband wireless communication system.

Another object of the present invention is to provide a method for estimating and correcting an uplink frequency offset in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and method for saving power (energy) required for uplink transmission in a broadband wireless communication system.

According to an aspect of the present invention for achieving the above object, in the transmitter device in a broadband wireless communication system, an index generator for generating a subcarrier index for mapping a transmission packet signal to a subcarrier at a predetermined interval, and the packet signal A pilot symbol mapper for mapping a pilot symbol to a corresponding subcarrier according to the subcarrier index and outputting the pilot symbol in a predetermined interval, and mapping a data symbol to a corresponding subcarrier according to the subcarrier index in a predetermined backward section of the packet signal transmission interval A data symbol mapper for output, an inverse fast fourier transform (IFFT) operator for generating sample data by performing inverse fast Fourier transform on the subcarrier-mapped pilot symbols and data symbols, and among sample data of each OFDMA symbol from the IFFT operator Extract some of the predetermined And a transmitting unit for transmitting.

According to another aspect of the present invention, the q-th packet signal in a broadband wireless communication system in which a transmitter maps a q-th packet signal to a subcarrier at predetermined intervals and performs IFFT operation and extracts and transmits a predetermined portion of sample data after the IFFT operation. A receiver device for receiving a signal, the receiver comprising: a buffer for buffering received sample data in units of a transmission interval of the packet signal, extracting samples corresponding to a q th packet signal from sample data of each OFDMA symbol from the buffer, An offset estimator for estimating a time offset and a frequency offset using the extracted samples, and correcting the sample data of each OFDAM symbol from the buffer with the time offset and the frequency offset, and sample data of each corrected OFDMA symbol. An offset corrector for extracting and outputting samples corresponding to the q th packet signal at And that is characterized.

According to still another aspect of the present invention, a method of transmitting a transmitter in a broadband wireless communication system, the method comprising: calculating a subcarrier index for mapping a transmission packet signal to a subcarrier at predetermined intervals; Mapping a pilot symbol to a corresponding subcarrier according to the subcarrier index, mapping a data symbol to the corresponding subcarrier according to the subcarrier index in a predetermined back section of the packet signal transmission interval, the subcarrier mapped pilot symbol and And a step of generating sample data by inverse fast Fourier transform of the data symbol, and extracting and transmitting a predetermined portion of sample data of each OFDMA symbol generated.

According to still another aspect of the present invention, the transmitter performs IFFT operation by mapping a q th packet signal to a subcarrier at predetermined intervals, and extracts and transmits a predetermined portion of sample data after the IFFT operation. In the first packet signal receiving method, buffering received sample data in units of a transmission interval of the packet signal, extracting samples corresponding to the q th packet signal from the sample data of each buffered OFDMA symbol, and extracting the extracted packet data. Estimating a time offset and a frequency offset using the samples, and correcting the sample data of each buffered OFDAM symbol with the time offset and the frequency offset, and applying the q in the sample data of each corrected OFDMA symbol. And extracting samples corresponding to the first packet signal.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, an uplink transmission apparatus and method for estimating (and correcting) an uplink frequency offset in a broadband wireless communication system will be described.

An OFDMA communication system according to an embodiment of the present invention uses IFFT and FFT having a size of N at a transmitting end and a receiving end, respectively. In addition, the number of packet signals that can coexist at the same instant is Q. Therefore, when transmitting different packet signals for each user, one user can simultaneously support up to Q different users. The minimum transmission unit of the transmitted packet signal is N ₀ OFDMA symbols, and subcarriers constituting each OFDMA symbol are determined as shown in Table 1 below.

Subcarrier index k Qp + q, -N _c / 2≤p <N _c / 2, p is an integer

Here, q is a packet signal index whose value is q = 0, 1, ..., Q-1, and N _c is the number of subcarriers occupied by the q th packet signal for each OFDMA symbol. Of all N subcarriers, (NN _c × Q) is reserved as a guard band. Pilot symbols are mapped to the first two of the OFDMA symbols constituting each packet signal, and data symbols are mapped to the remaining OFDMA symbols.

1 is a diagram illustrating a rule for allocating pilot symbols and data symbols on a time-frequency domain in a broadband wireless communication system according to an embodiment of the present invention.

A mapping rule is shown when N = 1024, Q = 8, N _c = 112, N0 = 6, and q = 0. The shaded parts represent pilot symbols and the white parts represent data symbols. As shown, the minimum transmission unit is six OFDMA symbols, subcarriers constituting one OFDMA symbol according to Table 1 are {-448, -440, -432, -424, ... 432, 440} do.

Hereinafter, a process of generating a baseband signal according to the present invention will be described.

라 하면, 이를 IFFT한 결과는 다음 <수학식 1>과 같다.First, when mapping a symbol (pilot symbol or data symbol) as shown in Table 1, the pilot or data symbol mapped to the k th subcarrier in the I th OFDMA symbol of the q th packet signal is first mapped.

In this case, the result of IFFT is shown in Equation 1 below.

는

를 IFFT한 결과 값으로, N을 주리고 하는 주기함수이다.here,

Is

IFFT is the result of the period function.

중 일부 구간을 선택하여 전송한다.Communication system according to the present invention

Select and send some of the sections.

2 is a diagram illustrating a method for selecting and transmitting some of sample data corresponding to one OFDMA symbol in a broadband wireless communication system according to an exemplary embodiment of the present invention.

As shown, among the IFFT result (see Equation 1) signal components corresponding to the i th OFDMA symbol of the q th packet signal, n is qP-N _p ≤ n <(q + 1) P + N _p . Only signal components are extracted and transmitted at the specified moment. That is, the actual number of samples of each packet signal transmitted for each OFDMA symbol is (2N _P + P). Here, N _P should be set to be greater than the absolute value of the maximum time offset that may occur between the reception start point of the receiver and the time point at which the actual signal is received.

3 is a view showing a plurality of user signals transmitted during one OFDMA symbol period in a broadband wireless communication system according to an embodiment of the present invention.

시간 구간에서 처음

시간 경과후

시간동안에 전송된다. 따라서, i번째 OFDMA심볼 구간동안 전송되는 q번째 패킷신호

은 하기 수학식 2와 같이 나타낼 수 있다.As shown, the transmission period of the OFDMA symbol is Q × N _s . Where N _s = 3 N _P + P. That is, when m is a time index (or sample index), one OFDMA symbol period may be expressed by 0 ≦ m ≦ QN _s . The q th packet signal occupies only a section of qN _s ≤ m <(q + 1) N _s during one OFDMA symbol period. In the above interval, nothing is transmitted during the first N _P time. Therefore, the signal component to be transmitted during each OFDMA symbol period of the q th packet signal is

First in time interval

After time

Transmitted during the time. Therefore, the q th packet signal transmitted during the i th OFDMA symbol period

Can be expressed as in Equation 2 below.

4 is a diagram illustrating a plurality of packet signals received during one OFDMA symbol period at a receiving end in a broadband wireless communication system according to an exemplary embodiment of the present invention.

인 모습을, q=Q-1인 패킷신호는 시간옵셋이

인 모습을 보여준다. 여기서, 시간옵셋이 음수인 경우는 예정된 시간보다 신호가 먼저 도착했다는 것을 의미하고, 시간옵셋이 양수인 경우 예정된 시간보다 신호가 늦게 도착했다는 것을 의미하다.As shown, the packet signals transmitted from the terminals arrive at the base station at different times for various reasons such as the movement of the terminal. When q = 0, the time offset of the packet signal is

Packet signal with q = Q-1 has a time offset.

I show a figure. If the time offset is negative, it means that the signal arrived earlier than the scheduled time. If the time offset is positive, it means that the signal arrived later than the scheduled time.

이라 가정한다. 설명의 편의상 송신단과 수신단 사이에 채널 왜곡이 없고, 채널 이득이 1이며 덧셈꼴 잡음도 없는 것으로 가정하면, 상기

는 하기 수학식 3과 같이 나타낼 수 있다.the received signal in the i-th OFDMA symbol period

Assume that For convenience of explanation, assuming that there is no channel distortion between the transmitter and the receiver, the channel gain is 1, and there is no addition noise.

Can be expressed as Equation 3 below.

는 q번째 패킷신호의 시간 옵셋이고,

는 q번째 패킷신호를 전송한 송신단과 수신단 반송파주파수 사이의 주파수 옵셋이다. 상기 수학식 3의 두 번째 항은 (i-1)번째 OFDMA심볼의 (Q-1)번째 신호의 시간옵셋이 1 이상인 경우, (i-1)번째 OFDMA심볼 구간에서 전송된 신호 성분이 지연되어 i번째 OFDMA심볼 구간에 수신되는 경우를 표현한 것이다.here,

Is the time offset of the q th packet signal,

Is the frequency offset between the transmitter and receiver carrier frequencies that transmitted the q th packet signal. In the second term of Equation 3, when the time offset of the (Q-1) th signal of the (i-1) th OFDMA symbol is 1 or more, the signal component transmitted in the (i-1) th OFDMA symbol period is delayed. The case where it is received in the i-th OFDMA symbol period is expressed.

Hereinafter, a process of estimating the time offset and the frequency offset from the received signal and detecting the signal will be described as shown in FIG. 4.

The time offset may be estimated using the repetitive characteristics of the packet signal.

First, it can be seen from Equation 1 that the relationship of Equation 4 below is established.

That is, two samples spaced apart by P among the samples constituting the packet signal have the same value.

Therefore, it can be seen from Equation 2 that the relationship of Equation 5 is established.

에 대한 추정치

을 구할 수 있다.In addition, since the first and second OFDMA symbols in each packet signal have the same value, the time offset of each packet signal using Equation 6 below.

Estimates for

Can be obtained.

,

이고, l은

의 범위를 갖는다.here,

,

And l is

Has a range of.

의 추정치

는 상기 <수학식 3>으로 표현되 는 수신신호에서 다음 수학식 7과 같은 상관값

을 이용해 구할수 있다.Meanwhile, the frequency offset

Estimate of

Is a correlation value as shown in Equation 7 below in the received signal represented by Equation 3

Can be obtained using

는 다음 <수학식 8>과 같이 구할 수 있다.Thus, the above

Can be obtained as shown in Equation 8.

The estimated time offset and frequency offset are corrected as in Equation 9 below.

는 수신신호

을 q번째 패킷신호의 시간 옵셋과 주파수 옵셋으로 보정한 값을 의미한다. 시간 옵셋과 주파수 옵셋이 완벽히 추정되었다면,

와

사이에는 다음 수학식 10과 같이 관계가 성립한다.here,

Is the received signal

Denotes a value corrected by the time offset and the frequency offset of the q th packet signal. If the time offset and frequency offset are perfectly estimated,

Wow

The relationship is established between them as shown in Equation 10 below.

는 P를 주기로 하는 주기함수가 되므로, 수학식 10의 관계를 이용해

의 추정치

을 다음 <수학식 11>과 같이 구할 수 있다.Meanwhile,

Since is a periodic function with a period P,

Estimate of

Can be obtained as shown in Equation 11.

Where% represents a modulus operation.

을 FFT연산기에 입력하면, 송신단에서 전송한 파일럿 및 데이터 심볼을 복원할 수 있다. 즉, FFT의 크기는 N이므로,

에 대한 관찰값

는 하기 수학식 12와 같이 구할 수 있다.Signal obtained as in Equation 11

Is input to the FFT operator, it is possible to recover the pilot and data symbols transmitted from the transmitter. In other words, the size of the FFT is N,

Observations for

Can be obtained as in Equation 12 below.

으로부터 실제 심볼을 검파하는 기술은, 본 발명과 직접적인 관련이 없으므로 자세한 설명을 생략하기로 한다.Obtained as above

The technique of detecting the actual symbol from the description is omitted since it is not directly related to the present invention.

Looking at the specific operation of the present invention in detail based on the above description as follows.

5 shows a configuration of a transmitter in a broadband wireless communication system according to an embodiment of the present invention.

As shown, the transmitter according to the present invention includes an encoder 501, a modulator 503, a subcarrier index generator 505, a data symbol mapper 507, a pilot symbol mapper 509, and an inverse fast fourier transform (IFFT). It includes a calculator 511, a transmission section selector 513, a digital-to-analog converter 515, and an RF processor 517.

Referring to FIG. 5, the encoder 501 encodes an input information bit string at a corresponding code rate and outputs coded bits. For example, the encoder 501 may include a convolutional encoder, a turbo encoder, a low density parity check (LDPC) encoder, and the like.

The modulator 503 maps the symbols from the encoder 501 to signal points by a given modulation scheme (number of variables) and outputs complex symbols. For example, the modulation scheme includes binary phase shift keying (BPSK), which maps one bit (s = 1) to one signal point (complex symbol), and two bits (s = 2) to one complex symbol. Quadrature Quadrature Phase Shift Keying (QPSK), 8-ary Phase Shift Keying (8PSK) to map three bits (s = 3) to one complex symbol, and four bits (s = 4) to one complex symbol There are 16QAM for mapping and 64QAM for mapping 6 bits (s = 6) to one complex symbol.

The subcarrier index generator 505 determines the number of packet signals that can coexist at the same time (Q), the assigned packet signal index (q), the number of subcarriers (N _c ) occupied by the q th packet signal for each OFDMA symbol, and the transmission period of the packet signals The subcarrier index to which a packet signal to be transmitted is mapped is received by receiving the number of OFDMA symbols (N ₀ ), which are represented, and provided to the data symbol mapper 507 and the pilot symbol mapper 509. Here, the parameters Q, N _c , N _o , q may be known values or information allocated from the base station. In addition, the subcarrier index generator 505 calculates a subcarrier index using Table 1, and provides the calculated subcarrier index to the pilot symbol mapper 509 in the pilot symbol transmission interval, and in the data symbol transmission interval. The data symbol mapper 507 is provided.

The data symbol mapper 505 maps the data symbols from the modulator 403 to the corresponding subcarriers based on the subcarrier indexes from the subcarrier index generator 505. Here, mapping to a subcarrier means providing each data symbol to a corresponding input (subcarrier position) of the IFFT operator 511.

The pilot symbol mapper 509 maps and outputs pilot symbols having a predetermined value to the corresponding subcarrier based on the subcarrier index from the subcarrier index generator 505.

The IFFT operator 511 outputs sample data in the time domain by performing inverse fast Fourier transform on the data symbols from the data symbol mapper 507 and the symbols from the pilot symbol mapper 509.

개의 샘플들)를 추출하고, 상기 추출된 샘플데이터를 지정된 순간에 출력한다.The transmission section selector 513 stores the sample data of the predetermined section according to the packet signal index q among the sample data from the IFFT operator 511.

Samples) and output the extracted sample data at a specified instant.

The digital-to-analog converter 515 converts the sample data from the transmission section selector 513 into an analog signal and outputs the analog signal. The RF processor 517 includes components such as a filter and a front end unit. The RF processor 517 performs RF processing to actually transmit a signal output from the digital-to-analog converter 515 and then transmits a transmission antenna (Tx). transmits to a wireless channel through an antenna).

6 shows the configuration of a receiver in a broadband wireless communication system according to an embodiment of the present invention.

As shown, the receiver according to the present invention includes an RF processor 601, an A / D converter 603, a buffer 605, an offset estimator 9407, an offset corrector 609, a first phase corrector 611, A repeater 613, a second phase corrector 615, an FFT operator 619, a data symbol extractor 619, a modulator 621, and an encoder 623 are configured. Hereinafter, an operation of estimating a time offset and a frequency offset from one packet signal and restoring data by correcting the estimated offset will be described.

Referring to FIG. 6, first, the RF processor 601 includes components such as a front end unit and a filter, and converts and outputs a signal of a high frequency band passing through a wireless channel into a baseband signal. . The analog / digital converter 603 converts an analog baseband signal from the RF processor 601 into a digital signal and outputs the digital signal.

The buffer 605 receives the baseband sample data from the analog-to-digital converter 603 and buffers it for N _o OFDMA symbol periods, and converts the buffered data to an offset estimator 607 and an offset corrector 609. to provide.

An offset estimator 607 estimates a time offset (TO) and a frequency offset (FO) using the sample data from the buffer 605, and calculates the estimated time offset and frequency offset. To the compensator 609. The offset estimator 607 estimates the time offset and the frequency offset using Equation 6 to Equation 8, which will be described in detail later with reference to FIG.

을 읽어 출력한다. 즉, 상기 옵셋 보정기(609)는 상술한 수학식 9와 같이 각 OFDMA심볼 구간에서 수신된 q번째 패킷신호를 옵셋 보정하여 출력한다. 이렇게 출력된 샘플데이터를 나타내면 도 10의 (a)와 같다. 도 10의 (a)에서 점선으로 표시된 사각형은 아직 그 값을 모르는 부분을 의미한다.The offset corrector 609 offset-compensates sample data from the buffer 605 by using a time offset and a frequency offset from the offset estimator 607, and P samples in the offset corrected signal.

Read and print That is, the offset corrector 609 performs offset correction on the q th packet signal received in each OFDMA symbol period as shown in Equation 9 and outputs the offset. The sample data output as described above is shown in FIG. The rectangle indicated by the dotted line in (a) of FIG. 10 means a part of which the value is not yet known.

와 같이 위상을 보정하여 출력한다. 이렇게 출력된 샘플데이터를 도시하면 도 10의 (b)와 같고, 그 값은

와 같다.The first phase compensator 611 is configured for P samples from the offset compensator 609.

The phase is corrected and output as follows. The output sample data is shown in FIG. 10 (b), and the value is

Same as

와 같이 길이 N인 샘플데이터를 출력한다. 이렇게 출력되는 샘플데이터를 도시하면 도 10의 (c)와 같고, 그 값은

와 같다.The repeater 613 repeats the sample data from the first phase corrector 611 (P-1) times.

Output sample data of length N as shown below. The sample data output in this way is the same as in FIG.

Same as

와 같이 다시 위상 보정을 수행하여 출력한다. 이렇게 출력된 샘플데이터를 도시하면 도 10의 (d)와 같고, 그 값은

와 같다. 이와 같이, 송신단에서의 IFFT 결과값을 복원한다.The second phase compensator 615 is provided with respect to the sample data from the repeater 613.

Phase correction is performed again as shown below. The output sample data is shown in FIG. 10 (d), and the value is

Same as In this way, the IFFT result value at the transmitting end is restored.

The FFT operator 617 performs fast Fourier transform on the sample data from the second phase compensator 615 and outputs data in the frequency domain. The data symbol extractor 619 extracts and outputs data symbols of known subcarrier positions from the data from the FFT operator 617. The modulator 621 demodulates the data symbols from the data symbol extractor 619 according to a modulation scheme of the transmitter and outputs encoded data. The decoder 623 decodes the coded data from the demodulator 621 according to the coding method of the transmitter and restores the original information data.

FIG. 7 illustrates a detailed configuration of the offset estimator 607 illustrated in FIG. 6.

As shown, the offset estimator 607 comprises a data separator 701, a pilot correlator 703, a CP correlator 705, a time offset detector 707, and a frequency offset detector 709.

Referring to FIG. 7, first, the data separator 701 provides the samples from the buffer 605 to the CP correlator 7015, and also provides the pilot correlator 703 the samples corresponding to the pilot interval among the sample data. do.

와 같다.The pilot correlator 703 correlates and outputs samples of the pilot interval from the data separator 701 as described in Equation 6 above. Mathematically represented

Same as

와 같다.The CP correlator 705 correlates and outputs samples of the N _o OFDMA symbol periods from the data separator 9701 as described in Equation 6 above. Mathematically represented

Same as

)을 출력한다. 이렇게 구해진 시간 옵셋은 옵셋 보정기(609)로 제공된다. 한편, 상기 파일럿 상관기(703)는 상기 최대값이 해당하는 파일럿 상관값을 주파수 옵셋 검출기(709)로 제공한다.The time offset detector 707 adds the correlation values from the pilot correlator 703 and the correlation values from the CP correlator 705 for each index l, and detects the maximum value (peak) of the added values. Time offset (

) The time offset thus obtained is provided to an offset corrector 609. Meanwhile, the pilot correlator 703 provides a pilot correlation value corresponding to the maximum value to the frequency offset detector 709.

으로 나누어 주파수 옵셋(

)을 출력한다. 이렇게 구해진 주파수 옵셋은 옵셋 보정기(609)로 제공된 다.Then, the frequency offset detector 709 extracts a phase value from the pilot correlation value from the pilot correlator 703 and decodes the phase value.

Divide by frequency offset (

) The frequency offset thus obtained is provided to an offset corrector 609.

8 illustrates a packet signal transmission procedure of a transmitter in a broadband wireless communication system according to an embodiment of the present invention.

Referring to FIG. 8, first, in step 801, the transmitter determines parameter values required for packet signal transmission. As described above, the parameters indicate the number of packet signals that can coexist at the same time (Q), the allocated packet signal index (q), the number of subcarriers (Nc) occupied by the qth packet signal for each OFDMA symbol, and the transmission period of the packet signals. The number of OFDMA symbols (N ₀ ) and the like, and these parameters (Q, N _c , N _o , q) may be a known value or information allocated from the base station.

In step 803, the transmitter calculates a subcarrier index to which a packet signal to be transmitted is mapped using the parameters. In operation 805, the transmitter maps pilot symbols and data symbols constituting the packet signal to the corresponding subcarriers according to the calculated subcarrier index. As shown in FIG. 1, pilot symbols and data symbols constituting the q-th packet signal are mapped to subcarriers at regular intervals.

)를 추출하여 송신한다.In operation 807, the transmitter generates inverse fast Fourier transform of the data mapped to the subcarrier to generate sample data. In step 809, the transmitter transmits sample data corresponding to a corresponding transmission section for each OFDMA symbol section.

) And send it.

9 illustrates a packet signal receiving procedure of a receiver in a broadband wireless communication system according to an embodiment of the present invention.

Referring to FIG. 9, first, in step 901, a receiver uses a characteristic in which the first and second OFDMA symbols of a packet signal have the same value, and a characteristic in which samples of the packet signal received in each OFDMA interval are repeated at a P interval. Estimate the offset. In this case, the time offset may be estimated using only one of the two characteristics. The operation of estimating the time offset is as shown in Equation 6.

으로 나누어 주파수 옵셋을 추정한다. 상기 주파수 옵셋을 추정하는 동작은 상기 수학식 7 및 상기 수학식 8과 같다.In step 903, the receiver extracts a phase value from a pilot interval correlation value at the time when the time offset is detected, and extracts the phase value.

Divide by to estimate the frequency offset. The operation of estimating the frequency offset is as shown in Equation 7 and Equation 8.

As described above, after estimating the time offset and the frequency offset, the receiver corrects the time offset and the frequency offset with respect to the received packet signal as shown in Equation 9 in step 905. In step 909, the receiver restores the signal whose time offset and frequency offset are corrected to the IFFT result data at the transmitter, that is, the input signal of the FFT operator.

In operation 909, the receiver performs fast Fourier transform on the restored data to generate data in a frequency domain. Thereafter, in step 911, the receiver extracts data of known subcarriers from the data of the frequency domain, demodulates and decodes the extracted data to restore original data.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, the present invention has an advantage of easily estimating and correcting an uplink frequency offset in an OFDMA-based broadband wireless communication system. In addition, the present invention has the advantage of saving the energy required for uplink transmission by transmitting a portion of the uplink transmission without transmitting all the sample data of the OFDMA symbol.

Claims (20)

A transmitter apparatus in a broadband wireless communication system, An index generator generated by calculating a subcarrier index for mapping a transmission packet signal to a subcarrier at predetermined intervals; A pilot symbol mapper configured to map a pilot symbol to a corresponding subcarrier according to the subcarrier index in a predetermined period of the packet signal transmission section, and to output the pilot symbol mapper; A data symbol mapper for mapping a data symbol to a corresponding subcarrier according to the subcarrier index and outputting the data symbol in a predetermined back section of the packet signal transmission section; An inverse fast fourier transform (IFFT) operator for generating sample data by performing inverse fast Fourier transform on the subcarrier mapped pilot symbols and data symbols; And a transmitter for extracting and transmitting a predetermined portion of sample data of each OFDMA symbol from the IFFT operator. The method of claim 1, And the index generator calculates a subcarrier index k as in the following equation.

here,

Represents the number of packet signals that can coexist at the same time,

Indicates the assigned packet signal index,

Is

The number of subcarriers occupied by the first packet signal for each OFDMA symbol. The method of claim 1, And the pilot symbol mapper maps pilot symbols to first two OFDMA symbols in the packet signal transmission interval. The method of claim 1, wherein the transmitting unit, A transmission section selector for extracting and outputting sample data of a predetermined transmission section among sample data of each OFDMA symbol from the IFFT operator; A digital / analog converter for converting sample data from the transmission section selector into an analog signal; And an RF processor for converting the baseband signal from the digital / analog converter into a radio frequency (RF) signal and transmitting the RF signal. In a receiver apparatus for receiving the q th packet signal in a broadband wireless communication system in which a transmitter maps a q th packet signal to a subcarrier at predetermined intervals, and extracts and transmits a predetermined portion of the sample data after the IFFT operation. , A buffer for buffering the received sample data in units of transmission intervals of the packet signal; An offset estimator extracting samples corresponding to the q th packet signal from the sample data of each OFDMA symbol from the buffer, and estimating a time offset and a frequency offset using the extracted samples; An offset corrector for correcting sample data of each OFDAM symbol from the buffer with the time offset and the frequency offset, extracting samples corresponding to the q th packet signal from the corrected sample data of each OFDMA symbol Device characterized in that. The method of claim 5, A first phase compensator for phase correcting sample data from the offset compensator to remove phase components; A repeater for repeating sample data from the first phase corrector to generate sample data having an FFT size for each OFDMA symbol; A second phase corrector for phase correcting the sample data of the FFT size from the repeater to restore data after the IFFT operation in the transmitter; And a fast fourier transform (FFT) operator for fast Fourier transforming sample data from the repeater to generate data in a frequency domain. The method of claim 5, The offset estimator, wherein the pilot symbol is mapped to the first two OFDMA symbols of the transmission interval of the packet signal, and characterized in that for estimating the time offset by using the repetitive characteristics of the two OFDMA symbols. The method of claim 7, wherein The offset estimator extracts a phase value from a pilot interval correlation value at the time when the time offset is detected, and extracts the phase value.

(Q is the number of packet signals that can coexist at the same time, N _s is the interval occupied by the packet signal in one OFDMA symbol interval, N is the FFT size) to estimate the frequency offset. The method of claim 5, And the offset estimator estimates the time offset using a characteristic in which samples of a packet signal received in each OFDMA section are repeated at predetermined intervals. The method of claim 6, An extractor for extracting data symbols of known subcarrier positions from data in a frequency domain from the FFT operator; A demodulator for demodulating data symbols from the extractor; And a decoder for decoding the demodulated data from the demodulator. In the transmission method of a transmitter in a broadband wireless communication system, Calculating a subcarrier index for mapping a transmission packet signal to a subcarrier at predetermined intervals; Mapping a pilot symbol to a corresponding subcarrier according to the subcarrier index in a predetermined ahead section of the packet signal transmission section; Mapping a data symbol to a corresponding subcarrier according to the subcarrier index in a predetermined back section of the packet signal transmission section; Generating inverse fast Fourier transform of the subcarrier mapped pilot symbols and data symbols to generate sample data; And extracting and transmitting a predetermined portion of sample data of each generated OFDMA symbol. The method of claim 11, The subcarrier index (k) is calculated as in the following equation.

here,

Represents the number of packet signals that can coexist at the same time,

Indicates an allocated packet signal index,

Is

The number of subcarriers occupied by the first packet signal for each OFDMA symbol. The method of claim 11, The pilot symbol is mapped to the first two OFDMA symbols of the packet signal transmission interval. The method of claim 11, wherein the transmitting process, Extracting sample data of a predetermined transmission interval from among sample data of each OFDMA symbol generated; A digital / analog converter for converting the extracted sample data into an analog signal; And converting the baseband signal from the digital / analog converter into a radio frequency (RF) signal and transmitting the RF signal. In the method of receiving a qth packet signal of a receiver in a broadband wireless communication system, a transmitter maps a qth packet signal to a subcarrier at predetermined intervals, performs IFFT operation, and extracts and transmits a predetermined portion of the sample data after the IFFT operation. Buffering the received sample data in units of transmission intervals of the packet signal; Extracting samples corresponding to the q th packet signal from the sample data of each buffered OFDMA symbol, estimating a time offset and a frequency offset using the extracted samples; Correcting the sample data of each buffered OFDAM symbol by the time offset and the frequency offset, and extracting samples corresponding to the q th packet signal from the sample data of each of the corrected OFDMA symbols. How to. The method of claim 15, Phase correcting the extracted sample data to remove phase components; Generating sample data having an FFT size for each OFDMA symbol by repeating the sample data from which the phase component is removed; Reconstructing the data after the IFFT operation in the transmitter by phase correcting the sample data of the generated FFT size; And performing fast Fourier transform on the restored sample data to generate data in a frequency domain. The method of claim 15, wherein the offset estimation process, And a pilot symbol is mapped to the first two OFDMA symbols in the packet signal transmission interval, and estimates the time offset using the repetition characteristics of the two OFDMA symbols. The method of claim 17, wherein the offset estimation process, The phase value is extracted from the pilot interval correlation value at the time when the time offset is detected, and the phase value is extracted.

And estimating the frequency offset by dividing (Q is the number of packet signals that can coexist at the same time, N _s is the interval occupied by the packet signal in one OFDMA symbol interval, and N is the FFT size). The method of claim 15, wherein the offset estimation process, And estimating the time offset using a characteristic in which samples of a packet signal received in each OFDMA section are repeated at predetermined intervals. The method of claim 16, Extracting data symbols of known subcarrier positions from the data of the frequency domain; And demodulating (demodulating) and decoding the extracted data symbols.

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