KR20090079505A - Apparatus and method for transmitting and receiving in a broadband wireless communication system - Google Patents

Abstract

An apparatus and a method for transmitting and receiving signals in a broadband wireless communication system are provided to improve reception performance by processing simply only signals of a receiver. A receiver removes a guard interval of a symbol received from a transmitter by using a guard interval remover(801). A symbol extractor divides the symbol into a front symbol and a rear symbol(803). The receiver synthesizes the front symbol and the rear symbol through a symbol synthesizer in order to synchronize starting points of the front symbol and the rear symbol(805). The receiver recovers the length of the symbol to the original length of the symbol by using a symbol stretcher(807). The receiver converts a time domain signal to a frequency domain signal by using an FFT(Fast Fourier Transform) unit(809). A channel compensation process is performed to remove distorted components from a channel(811). A post process is performed(813).

Description

Method and apparatus for transmitting and receiving signals in broadband wireless communication system {APPARATUS AND METHOD FOR TRANSMITTING AND RECEIVING IN A BROADBAND WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a broadband wireless communication system, and more particularly, to an orthogonal frequency division multiplexing (OFDM) / orthogonal frequency division multiple access (OFDMA) scheme. The present invention relates to a method and an apparatus capable of improving reception performance of a receiver in a communication system to be used.

Recently, the OFDM method, which is used as a useful method for high-speed data transmission in a wired / wireless channel, is a method of transmitting data using a multi-carrier, which is performed by converting serially inputted symbol strings in parallel. It is a type of Multi Carrier Modulation (MCM) that modulates and transmits each of a plurality of sub-carriers having orthogonality.

The OFDM scheme further reduces the negative effects of the system on the multipath and delay spread as the guard interval use and the cyclic prefix (CP) guard interval insertion scheme are known. In addition, the OFDM scheme is rapidly developing due to various digital signal processing technologies including a Fast Fourier Transform (FFT) and an Inverse Fast Fourier Transform (IFFT).

The OFDM scheme is characterized by obtaining optimal transmission efficiency in high-speed data transmission by maintaining orthogonality between a plurality of subcarriers. In addition, the frequency usage efficiency is good and the characteristics of the multi-path fading (multi-path fading) has the characteristics that can be obtained at the optimum transmission efficiency in high-speed data transmission. In addition, because the frequency spectrum is superimposed, frequency use is efficient, strong in frequency selective fading, strong in multipath fading, and protection intervals can be used to reduce the effects of inter symbol interference (ISI). In addition, it is possible to simply design the equalizer structure in terms of hardware and has the advantage of being resistant to impulsive noise, and thus it is being actively used in the communication system structure.

The multiple access scheme based on the OFDM scheme is the OFDMA scheme. In the OFDMA scheme, subcarriers within one OFDM symbol are divided and used by a plurality of users, that is, a plurality of terminals.

Meanwhile, in the broadband wireless communication system, a transmission signal transmitted by a transmitter is distorted while passing through a wireless channel, and a receiver receives the distorted transmission signal. In addition, due to a problem on a channel until the transmission signal of the transmitter is transmitted to the receiver, the transmission signal may be lost before being transmitted to the receiver, or may be distorted and received as described above. Accordingly, in the broadband wireless communication system, various alternatives have been researched and developed to improve the reception performance of the receiver.

Accordingly, an object of the present invention is to provide a method and apparatus for improving the reception performance of a receiver in a broadband wireless communication system.

Another object of the present invention is to provide a method and apparatus for improving OFDM / OFDMA symbol reception performance of a receiver in a communication system using an OFDM / OFDMA scheme.

Still another object of the present invention is to provide a method and apparatus for improving signal reception performance by simple signal processing of a receiver in a broadband wireless communication system.

It is still another object of the present invention to provide a method and apparatus for improving reception performance of a receiver without consuming additional resources when generating OFDM / OFDMA symbols in a broadband wireless communication system.

According to an embodiment of the present invention for achieving the above object, in a transmitting apparatus of a broadband wireless communication system, the transmitter is a first subcarrier corresponding to a repeating pattern to be repeated in a symbol in the time domain. Grouping the subcarrier set of the group and the subcarrier set of the second group, selecting subcarriers to be allocated to transmission symbols among the subcarrier set of the first group, and selecting the subcarriers of the first group to the modulation symbol Assigning a set, selecting subcarriers to be allocated to transmission symbols among the subcarrier sets of the second group, allocating a subcarrier set of the second group to the modulation symbol, and selecting the first group Transmitting the signal allocated with the subcarrier set of and the signal allocated with the subcarrier set of the second group after inverse fast Fourier transform It includes.

A method according to an embodiment of the present invention for achieving the above object, in the receiving device of a broadband wireless communication system, the process of removing the guard interval of the symbol received from the transmitter, and shearing the symbol after the removal of the guard interval Separating the sub-symbol and the trailing-end symbol, synthesizing the front-end symbol and the trailing-end symbol, generating a synthesized symbol, restoring the symbol length of the synthesized symbol to the original symbol length, and the one After the fast Fourier transform for the symbol of the signal to the frequency domain signal after converting to a data bit through a post-processing process.

A method according to an embodiment of the present invention for achieving the above object, in the receiving apparatus of the broadband wireless communication system, the process of removing the guard interval of the symbol received from the transmitter, and one symbol after removing the guard interval Dividing the signal into a front end symbol and a rear end symbol in the time domain, converting the front end symbol and the rear end symbol in the time domain into a signal in the frequency domain after fast Fourier transform, and the front end symbol and Synthesizing a trailing end symbol into one full symbol and outputting the data bits through a post-processing procedure for the entire symbol.

An apparatus according to an embodiment of the present invention for achieving the above object, in the receiving device in a wideband wireless communication system, a guard interval eliminator for inputting a signal received from the transmitter to remove the guard interval and outputs; A symbol extractor for separating the symbols after the guard interval is separated into a front end symbol and a rear end symbol, a symbol synthesizer for synthesizing the front end symbol and the rear end symbol, and outputting a synthesized symbol; And a symbol stretcher for restoring and outputting a symbol length, and post-processing devices for outputting data bits through post-processing of signals output from the symbol stretcher.

An apparatus according to an embodiment of the present invention for achieving the above object, in the reception device of a broadband wireless communication system, a guard interval eliminator for removing and outputting the guard interval received from the transmitter, and the guard interval; A symbol extractor for dividing the removed symbol into a front-end symbol and a rear-end symbol, respectively, and outputting the first and second FFTs after inputting a signal in which the front-end symbol is converted in parallel and converting the N / 2-point fast Fourier transform; A second FFT unit for inputting a signal in which the rear end symbol is converted in parallel, and outputting the N / 2-point fast Fourier transform; and a front end symbol and a rear end symbol respectively inputted from the first and second FFT units. And a post-processing device for synthesizing and outputting the data bits through post-processing on the signal output from the synthesizer. The.

As described above, according to the method and apparatus for improving reception performance in the broadband wireless communication system proposed by the present invention, the receiver of the broadband wireless communication system can improve the reception performance of a transmission signal only by simple signal processing. According to the transmission and reception by the pattern repetition of the present invention, the reception performance of the receiver can be improved without additional consumption of resources such as bandwidth and power. In addition, by using the pattern repetition method of the present invention, the receiver may improve the reception carrier to interference noise ratio (CINR) (approximately 3 dB), thereby improving the reception performance of the receiver and reducing the packet error rate (PER). And there is an advantage that can improve the throughput (Throughput). In addition, the present invention has an advantage that can be applied to both downlink and uplink.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, only the parts necessary for understanding the operation according to the embodiment of the present invention will be described, it should be noted that the description of other parts will be omitted so as not to distract from the gist of the present invention.

The terms or words used in the specification and claims described below should not be construed as being limited to ordinary or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical spirit of the present invention. And the embodiments described in the specification and the configuration shown in the drawings are only one of the most preferred embodiment of the present invention, not representing all of the technical idea of the present invention. Therefore, it should be understood that there may be various equivalents and modifications that can substitute for them at the time of the present application.

The present invention relates to a method and apparatus that can improve the reception performance of a receiver in a broadband wireless communication system. Particularly, in an embodiment of the present invention, OFDM / OFDMA symbol reception performance of a receiver in a communication system using Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) It proposes a method and apparatus to improve the.

Hereinafter, for convenience of description, a case in which the communication system of the present invention uses the OFDMA scheme will be described as a representative example. However, the present invention is not limited to an OFDMA communication system, and of course, it can be used for all broadband wireless communication systems using a multicarrier modulation method. In the following description, it is assumed that a transmitter is a base station (BS) and a receiver is a mobile station (MS). However, in the present invention, the base station and the receiver may be a transmitter and a receiver, respectively. That is, the present invention can be applied to both downlink (DL) and uplink (UL).

1 is a diagram schematically illustrating a transmitter structure for performing a function in an embodiment of the present invention.

Referring to FIG. 1, first, the transmitter of the present invention includes an encoder 111, an interleaver 113, a modulator 115, and a symbol mapper 117. A serial to parallel converter 119, an Inverse Fast Fourier Transform (IFFT) 121, a parallel to serial converter 123, A guard interval inserter 125, a digital to analog converter (D / A converter) 127, and a radio frequency (RF) processor 129 may be connected. It is configured to include.

First, when user data bits and control data bits to be transmitted are generated, the user data bits and the control data bits are input to the encoder 111. Hereinafter, both the user data bits and the control data bits will be referred to as "data bits" for convenience of description. The encoder 111 inputs the data bits, encodes the data bits in a preset encoding scheme, and outputs the encoded bits to the interleaver 113. Here, the encoding scheme may be a turbo coding scheme or a convolutional coding scheme having a predetermined coding rate.

The interleaver 113 interleaves the encoded bits output from the encoder 111 in a preset interleaving manner and outputs the encoded bits to the modulator 115.

The modulator 115 modulates the encoded encoded bits output from the interleaver 113 by using a preset modulation scheme, generates modulated symbols, and outputs the modulated symbols to the symbol mapper 117. Here, the modulation scheme may be a Quadrature Phase Shift Keying (QPSK) scheme, a Phase Shift Keying (8PSK) scheme, a Quadrature Amplitude Modulation (16QAM) scheme, or a 64QAM scheme.

The symbol mapper 117 inputs a modulation symbol output from the modulator 115 to allocate a subcarrier and outputs the subcarrier to the serial / parallel converter 119. Here, the subcarrier mapping operation of the symbol mapper 117 is performed according to the subcarrier mapping scheme proposed in the present invention.

In this case, in the present invention, the subcarrier mapping operation is performed using the symbol mapper 117. However, the subcarrier mapping operation may be performed by the serial / parallel converter 119. When performing the subcarrier mapping operation on the serial / parallel converter 119, the configuration of the symbol mapper 117 may be omitted.

The symbol mapper 117 groups a subcarrier set to be allocated to the modulation symbol into at least two groups corresponding to a preset repetition pattern P, and modulates the subcarrier set of each grouping group. After mapping to the symbol is output to the serial / parallel converter 119. For example, assuming that the repetition pattern P is 2, the symbol mapper 117 is a subcarrier number belonging to an integer multiple (an integer multiple of 2) of the repetition pattern P. a subcarrier set of a first group, which is a subcarrier group having a number), and a subcarrier set of a second group having a number of subcarriers other than the subcarriers of the first group, and may be mapped to the modulation symbol. . At this time, the DC subcarrier is excluded.

In addition, hereinafter, a group to which a receiver for receiving a signal according to the transmission method of the present invention belongs is named a first group, and a group to which a receiver for receiving a signal according to the general transmission method belongs is named a second group.

과 같을 때, 상기 IFFT기(121)에서 2의 배수에 해당하는 계수(coefficient)에만 값을 할당하면, 상기

가 2배가 되며, 결국 심벌 주기가 1/2로 변경되어 패턴이 2번 반복되게 된다. 여기서, 상기

는 서브캐리어 간의 간격을 나타낸다. 이때, 상기 송신기가 본 발명의 방식에 따른 수신기로만 신호를 송신하는 경우를 가정하면, 상기 반복패턴의 정수배에 속하는 서브캐리어에만 전송 데이터 비트가 할당되며, 0 번째 서브캐리어(DC 성분)와 상기 반복패턴의 정수배에 속하는 서브캐리어 번호를 가지는 서브캐리어들을 제외한 나머지 서브캐리어에는 널 데이터(0)가 할당될 수 있다.So symbol time

When the value is assigned to only a coefficient corresponding to a multiple of 2 in the IFFT unit 121,

Is doubled, and the symbol period is changed to 1/2 so that the pattern is repeated twice. Where

Denotes the spacing between subcarriers. In this case, assuming that the transmitter transmits a signal only to a receiver according to the present invention, a transmission data bit is allocated only to a subcarrier belonging to an integer multiple of the repetition pattern, and a 0 th subcarrier (DC component) and the repetition. Null data (0) may be allocated to the remaining subcarriers except subcarriers having a subcarrier number belonging to an integer multiple of the pattern.

The serial / parallel converter 119 inputs serial modulation symbols of the serial form output from the symbol mapper 117 and converts them in parallel and outputs them to the IFFT unit 121. The IFFT unit 121 inputs the signal output from the serial / parallel converter 119 to perform an N-point IFFT and then outputs it to the parallel / serial converter 123. As described above, if the IFFT device 121 assigns a value only to a coefficient corresponding to a multiple of the repetition pattern 2, the interval between subcarriers is doubled, and the symbol period is changed to 1/2 so that the OFDMA The symbol pattern is repeated twice. An example of such a symbol pattern is shown in FIG. As shown in FIG. 2, it can be seen that the same symbol is repeated twice. Since the symbol structure of FIG. 2 will be described later, a detailed description thereof will be omitted.

The parallel / serial converter 123 inputs the signal output from the IFFT unit 121 and performs serial conversion to output the signal to the guard section inserter 125. The guard section inserter 125 inputs a signal output from the parallel / serial converter 123 to insert a guard section signal and outputs the signal to the digital / analog converter 127. Here, the guard period is inserted to remove interference between the OFDM symbol transmitted at the previous OFDM symbol time and the current OFDM symbol to be transmitted at the current OFDM symbol time when the OFDM symbol is transmitted in the OFDMA communication system. The guard interval is a cyclic prefix (CP) scheme in which the last predetermined bits of the OFDM symbol in the time domain are copied and inserted into the effective OFDM symbol, or after the first predetermined bits of the OFDM symbol in the time domain are copied and followed by the valid OFDM symbol. It is used as a "CP (Cyclic Postfix)" method to insert.

The digital-to-analog converter 127 inputs the signal output from the protection section inserter 125 to perform analog conversion and outputs the signal to the RF processor 129. Here, the RF processor 129 includes components such as a filter and a front end unit, so that the signal output from the digital-to-analog converter 127 can be transmitted on actual air. After the RF process, the transmission is performed on the air through a Tx antenna.

Next, the modulation symbol mapping method proposed by the present invention will be described. Hereinafter, unless otherwise stated, a subcarrier is a subcarrier set (subcarrier set of the first group) used to send data bits to a receiver according to an embodiment of the present invention, and is an integer multiple of the repetition pattern P (where , Refers to a subcarrier set having a sub-carrier number belonging to the subcarrier.

2 is a diagram schematically illustrating a symbol structure according to an exemplary embodiment of the present invention.

Before describing FIG. 2, in the embodiment of the present invention, the same symbol structure may be used in both downlink (DL) and uplink (UL). 2 illustrates an example of an OFDMA symbol structure that is repeated twice in one modulation symbol when the repetition pattern P is 2 (P = 2). As shown in FIG. 2, the symbol structure of the present invention has a symbol structure having a pattern repeated twice in one data symbol.

Referring to FIG. 2, the symbol has a form in which a symbol having a specific length (for example, 128 bits) is repeated twice in correspondence to the repetition pattern (P = 2). CP is added to the front of the symbol in the form of the symbol repeated twice.

In addition, the signals before performing the above-described IFFT are frequency domain signals, and the signals after performing the IFFT are time-domain signals. The repeated symbol illustrated in FIG. 2 is a time-domain after performing the IFFT. Shows the symbol at.

Meanwhile, modulation symbols in the frequency domain before performing the IFFT, that is, a number B specified as S (-B: B) in FIG. 3 to be described below indicate a subcarrier position applied when performing the IFFT. Since this will be described with reference to FIG. 3 below, detailed description thereof will be omitted. S (-B: B) may represent a frequency domain symbol in which the symbol of the specific length is repeated twice.

3 is a conceptual diagram illustrating a process of assigning an IFFT coefficient to each subchannel in an IFFT device according to an embodiment of the present invention. In particular, FIG. 3 schematically illustrates a mapping relationship between subcarriers and a symbol when performing IFFT.

Prior to the description of FIG. 3, a subject for allocating a subcarrier to which data corresponding to each receiver will be loaded is a base station, and a rule relating to subcarrier allocation is shared with each receiver (mobile terminal). Since each subcarrier is one-to-one mapping with the IFFT input coefficients located in the transmitter, the N-point IFFT unit 121 may generate a time domain signal having N subcarriers (including DC). 3 shows a mapping relationship between subcarriers and IFFT input coefficients.

In this case, when the receiver of the present invention belongs to the first group to receive, when the transmitter modulates each subcarrier in the frequency domain, the transmitter has a subcarrier number having a subcarrier number corresponding to a multiple of the repetition pattern (P). Modulate (the DC subcarrier always assigns '0'), and the remaining subcarriers assign 0 (ie, the amplitude of the subcarrier is zero), thereby repeating the repeating pattern in one symbol ( A symbol having a pattern repeated by P) may be generated. In this embodiment, when the repeating pattern P is 2, an example of a symbol repeated twice in the symbol is shown in FIG. 2.

Referring to FIG. 3, the numbers of the IFFT input terminals in FIG. 3 represent frequency components of the OFDMA communication system, that is, numbers of subcarriers. Here, only M subcarriers of the N subcarriers are used. In particular, subcarriers 0 to 0 of the N subcarriers, subcarriers from subcarriers (-N / 2) to subcarriers (-B-1), and subcarriers (B + 1) to Only M subcarriers are used except for (N / 2-1) subcarriers.

Subcarriers 0 to 0, subcarriers from subcarriers (-N / 2) to subcarriers (-B-1), and subcarriers (B + 1) to (N / 2-1) Null data, that is, zero data, is inserted into each of the subcarriers up to the subcarrier, and the reason is described below.

First, null data is inserted into subcarrier 0 because subcarrier 0 represents a reference point of a symbol in the time domain, that is, a DC component in the time domain after IFFT. Insert data. Also, subcarriers of subcarriers (-N / 2) to (-B-1) and subcarriers of (B + 1) to (N / 2-1) subcarriers The reason for inserting null data into carriers is that the subcarriers from subcarriers (-N / 2) to subcarriers (-B-1) and subcarriers (B + 1) to (N / 2) This is because the subcarriers up to subcarrier -1) correspond to the guard interval.

Thus, when the symbol S (-B: B) in the frequency domain is input to the IFFT unit 121, the IFFT unit 121 maps the symbol S (-B: B) in the frequency domain to the corresponding subcarriers. IFFT is performed to output symbols in the time domain.

On the other hand, assuming that the transmitter transmits a signal only to a receiver according to the present invention, the total number of subcarriers of the OFDMA communication system is N and the signal output from the symbol mapper 117 is the IFFT device. It is input as an IFFT coefficient of 121. Accordingly, among the N subcarriers, subcarriers [-B, -B + 2, ...] having subcarrier numbers corresponding to multiples of the repetition pattern P are subcarriers actually used in the receiver of the present invention. , -4, -2, 2, 4, ..., B] may be allocated the data bits.

In this case, null data 0 may be allocated to the remaining subcarriers except for the subcarriers having a zeroth subcarrier (DC component) and a subcarrier number belonging to an integer multiple of the repetition pattern. However, when the subcarrier sets of the first group and the second group are used in the present invention, other subcarriers except for subcarriers having a subcarrier number belonging to an integer multiple of the repetition pattern may also be mapped to values received by a general receiver. have.

4 is a diagram illustrating a symbol generation procedure in a transmitter according to an embodiment of the present invention. In particular, in FIG. 4, it is assumed that each receiver knows whether or not each receiver has an ability to receive an OFDMA signal by the reception method proposed by the present invention for all receivers to receive data bits to be transmitted. .

Referring to FIG. 4, the transmitter may first determine a repeating pattern P to be repeated in a symbol in the time domain (step 401). The repeating pattern P represents an integer of 2 or more. The repeating pattern may be a value that is set in advance when designing a system. In addition, the repetition pattern may be set to an optimal value corresponding to the system environment every time data bits are transmitted according to the system environment. The optimal value may be set to a repeating pattern value mapped according to a given system environment.

Then, as described above, the transmitter groups the subcarriers according to the determined repetition pattern as follows (step 403). In FIG. 4, it is assumed that two groups are classified into subcarrier sets of the first group and subcarrier sets of the second group. The subcarrier set of the first group is a subcarrier set used for transmitting data bits to a receiver to use the reception method proposed by the present invention, and has a subcarrier number belonging to an integer multiple of the determined repetition pattern (P). Subcarriers. In this case, the DC subcarriers of the subcarriers corresponding to the integer multiple of the repeating pattern P may be excluded. The subcarrier set of the second group is the remaining subcarrier set except for the subcarrier set belonging to the first group among all available subcarriers.

Next, the transmitter determines a receiver to receive the data bits through the subcarrier set of the first group and the receiver to receive the data bits through the subcarrier set of the second group, the next subcarrier and The symbol mapping operation may be performed.

In the case of data bits of a receiver using the first group of subcarrier sets, the transmitter selects some or all subcarriers to be allocated to a transmission symbol among the first group of subcarrier sets (step 407). Subsequently, the transmitter modulates a symbol to be transmitted by using a preset modulation scheme to generate a modulated symbol (step 409). The transmitter allocates the selected first group of subcarriers to the modulation symbol (step 411).

Specifically, the set of subcarriers to be allocated to the modulation symbols output from the modulator through the above-described symbol mapper is grouped into the subcarrier set of the first group and the subcarrier set of the second group, respectively, in response to the repetition pattern. Subsequently, a first set of subcarriers of the first group is mapped to the first modulation symbol in a first modulation symbol transmitted to the receiver of the present invention among the modulation symbols. For example, assuming that the repetition pattern P is 2, the symbol mapper 117 is a subcarrier number belonging to an integer multiple (an integer multiple of 2) of the repetition pattern P. A subcarrier set having number) may be mapped to the first modulation symbol. For example, the subcarrier set of the first group may be grouped into a subcarrier set having an even index, that is, an even subcarrier number, among all subcarriers, and mapped to the first modulation symbol.

In addition, in the case of data bits of the receiver using the subcarrier set of the second group, the transmitter selects some or all subcarriers to be allocated to the transmission symbol among the subcarrier sets of the second group (step 413). Subsequently, the transmitter modulates a symbol to be transmitted by using a preset modulation scheme and generates a modulated symbol (step 415). The transmitter allocates the selected second group of subcarriers to the modulation symbol (step 417).

Specifically, the set of subcarriers to be allocated to the modulation symbols output from the modulator through the above-described symbol mapper is grouped into the subcarrier set of the first group and the subcarrier set of the second group, respectively, in response to the repetition pattern. Subsequently, a second set of subcarriers of the second group is mapped to the second modulation symbol in a second modulation symbol transmitted to a general receiver among the modulation symbols. For example, assuming that the repeating pattern P is 2, the symbol mapper 117 has a subcarrier having a number of subcarriers belonging to an integer multiple (an integer multiple of 2) of the repeating pattern P. A subcarrier set having a number of subcarriers other than the set may be mapped to the second modulation symbol.

Next, the transmitter performs an N-point IFFT by inputting the signals output in steps 411 and 417 (step 419), and then uses at least one receiver using the reception method proposed by the present invention through a wireless channel. And transmit to at least one other receiver using a general reception method (step 421).

The operation of the transmitter and the transmitter of the OFDMA communication system has been described above. Hereinafter, the operation of the receiver and the receiver of the OFDMA communication system according to an embodiment of the present invention will be described. First, a receiver structure of an OFDMA communication system will be described with reference to FIG. 5.

5 is a view schematically showing a receiver structure for performing a function in an embodiment of the present invention, Figure 6 shows an example of a symbol structure after the removal of the guard interval output from the symbol extractor of the present invention, Figure 7a FIG. 7B illustrates an example of a symbol output from the symbol stretcher of the present invention.

Referring to FIG. 5, the receiver of the present invention includes an RF processor 511, an analog / digital converter (513), and a guard interval remover (515). ), Symbol extractor 517, symbol combiner 519, symbol stretcher 521, serial / parallel converter 523, and fast Fourier transform Fast Fourier Transform (FFT) 525, parallel / serial converter 527, channel estimator 529, channel compensator 531, demodulator 533 And a de-interleaver 535 and a decoder 537.

First, a signal transmitted from the transmitter is received through a Rx antenna of the receiver in the form of a multipath channel and a noise component added thereto. The signal received through the receive antenna is input to the RF processor 511, and the RF processor 511 down converts the signal received through the receive antenna to an intermediate frequency (IF) band. And then output to the analog-to-digital converter 513. The analog-to-digital converter 513 digitally converts the analog signal output from the RF processor 851 and outputs the digital signal to the guard interval remover 515. The guard interval remover 515 removes the guard interval by inputting the signal output from the analog-to-digital converter 513 and outputs it to the symbol extractor 517.

The symbol extractor 517 inputs a signal from which the guard interval output from the guard interval remover 515 is removed, extracts a symbol corresponding to the symbol extraction method of the present invention, and outputs the symbol to the symbol synthesizer 519. That is, the symbol extractor 517 separates the symbol after removing the protective section into a front end symbol 610 and a rear end symbol 630 as shown in FIG. 6. In this case, the number of samplings, that is, the length of time, of the front end symbol 610 and the rear end symbol 630 is the same. In addition, it is assumed that the trailing end symbol 630 does not overlap with the region of the next symbol that is not the current symbol.

6 illustrates an example of a symbol structure after the guard interval is removed by the symbol extractor 517 of the receiver of the present invention. In particular, in FIG. 6, it is assumed that the repeating pattern P is 2, and although the repeating pattern P is 2 as shown in FIG. 6, the reason why the same pattern is not repeated twice in the symbol is described above. This is because the symbol generated by the transmitter may include data to be transmitted to a receiver belonging to the subcarrier set of the second group. Therefore, in the whole symbol, if the receiver belonging to the subcarrier set of the first group only looks at the subcarriers to receive even though there is no repeating pattern in the symbol for the above reason, that is, the subcarrier set of the second group in the entire symbol Symbols except for signals allocated to all receivers belonging to have a repeating pattern.

The symbol synthesizer 519 synthesizes the front end symbol 610 and the rear end symbol 630 output from the symbol extractor 517 and outputs the result to the symbol stretcher 521. As shown in FIG. 7A, the symbol synthesizer 519 synthesizes a synthesized symbol 700 which is generated by synthesizing one for the start point synchronization between the front end symbol 610 and the rear end symbol 630. 521). As such, the effect of increasing the desired signal strength by combining subcarrier sets of the same pattern is generated, and accordingly, the present invention can improve the reception performance of symbols.

The symbol stretcher 521 adjusts the length of the synthesized symbol 700 output from the symbol synthesizer 519 to the original symbol length and outputs the converted symbol to the serial / parallel converter 523. As shown in FIG. 7B, the symbol stretcher 521 inputs the synthesized symbol 700 outputted from the symbol synthesizer 519 to match the symbol length of the synthesized symbol 700 to the original symbol length. do. Here, the symbol stretcher 521 may match the symbol length by copying the composite symbol 700.

The serial / parallel converter 523 inputs a serial signal output from the symbol stretcher 521 to perform parallel conversion and outputs the serial signal to the FFT unit 525. The FFT unit 525 performs an N-point FFT on the signal output from the serial / parallel converter 523 and then outputs the signal to the parallel / serial converter 527. The parallel / serial converter 527 inputs a parallel signal output from the FFT 525 and serially converts it, and outputs the serial signal to the channel estimator 529 and the channel compensator 531.

The channel estimator 529 inputs the signal output from the parallel / serial converter 527 to perform channel estimation, and then outputs the channel estimation result to the channel compensator 531. The channel compensator 531 performs channel compensation on the signal output from the parallel / serial converter 527 with the channel estimation result output from the channel estimator 529 and outputs the result to the demodulator 533. The demodulator 533 demodulates the demodulation scheme corresponding to the modulation scheme applied by the transmitter for inputting the signal output from the channel compensator 531 and outputs the demodulation scheme to the deinterleaver 535.

The deinterleaver 535 deinterleaves the signal output from the demodulator 533 in a deinterleaving scheme corresponding to the interleaving scheme applied by the transmitter and then outputs the deinterleaving scheme to the decoder 537. The decoder 537 receives a signal output from the deinterleaver 535, decodes the decoding signal corresponding to an encoding scheme applied by the transmitter, and outputs the received data bit.

5 illustrates a receiver structure of an OFDMA communication system. Next, a method of improving reception performance of an OFDMA symbol according to an embodiment of the present invention will be described.

8 is a diagram illustrating a reception signal processing operation of a receiver according to an embodiment of the present invention.

In particular, FIG. 8 illustrates a symbol reception operation that combines in the time domain. In this case, it is assumed that the repetition pattern P determined by the transmitter is 2. FIG. 8, only processes necessary for describing the reception method of the present invention will be described.

Referring to FIG. 8, the receiver removes the guard interval of the symbol received from the transmitter through the guard interval remover 515 (step 801). Thereafter, the symbol after removing the guard period is separated into a front end symbol and a rear end symbol through the symbol extractor 517 (step 803).

In this case, when the symbol after removing the protection interval is named as the entire symbol, the entire symbol may be divided into 1/2 corresponding to the repetitive pattern P and divided into the front and rear ends of the symbol. . In this case, as described above, the number of samplings, that is, the time lengths, of the front and rear symbols are the same.

In addition, as shown in FIG. 6, although the repeating pattern is 2, the reason why the same pattern is not repeated twice in the symbol may include data to be transmitted to a general receiver belonging to the second group. Because it can. Therefore, in the whole symbol, although the repeating pattern does not exist in the symbol due to the above-mentioned reasons, only the subcarriers to be received by the receiver of the present invention belonging to the first group, that is, belonging to the second group in the whole symbol Symbols except for signals assigned to all receivers have a repeating pattern.

Subsequently, the receiver synthesizes the front end symbol and the rear end symbol for starting point synchronization of the front end symbol and the rear end symbol through the symbol synthesizer 519 (step 817). In other words, the front and rear symbols are combined to have the same starting point. This results in the effect of increasing the desired signal strength by combining subcarriers of the same pattern, which in turn can improve the reception performance of the symbol.

Next, the receiver restores the length of the synthesized symbol to the original symbol length through the symbol stretcher 521 (step 807). In an embodiment of the present invention, a method of copying the summed signal is used.

Then, the receiver performs an FFT on a signal in the time domain through the FFT unit 525 to convert the signal into a signal in the frequency domain (step 809), and removes the distorted component from the channel, that is, the channel compensation step. Perform step 811. Thereafter, the receiver outputs data bits through general post-processing processes such as a demodulation step, a deinterleaving step, and a decoding step as described with reference to FIG. 5.

9 is a view schematically showing another configuration of a receiver according to an embodiment of the present invention.

Referring to FIG. 9, the receiver of the present invention includes an RF processor 911, an analog / digital converter 913, a guard interval remover 915, a symbol extractor 917, and serial / parallel converters 921. ) 931, 1/2 FFTs 923 and 933, parallel / serial converters 925 and 935, channel compensators 927 and 937, channel estimator 929, A synthesizer 941, a demodulator 943, a deinterleaver 945, and a decoder 947 are configured.

First, a signal transmitted from the transmitter is received through a Rx antenna of the receiver in the form of a multipath channel and a noise component added thereto. The signal received through the receive antenna is input to the RF processor 911, and the RF processor 911 down converts the signal received through the receive antenna to an intermediate frequency (IF) band. And then output to the analog-to-digital converter 913. The analog-to-digital converter 913 digitally converts the analog signal output from the RF processor 911 and outputs the digital signal to the guard section remover 915. The guard interval eliminator 915 removes the guard interval by inputting the signal output from the analog-to-digital converter 913 and outputs the guard interval to the symbol extractor 917.

The symbol extractor 917 inputs a signal from which the guard interval is output from the guard interval remover 915 to extract a symbol corresponding to the symbol extraction method of the present invention, and then the serial / parallel converter 921 and the The symbol extractor 917 outputs the symbols after removing the guard period from the front-end symbol 610 and the post-symbol converter 917 as described in the description with reference to FIG. The front end symbol 610 is output to the serial / parallel converter 921 and the rear end symbol 630 is output to the serial / parallel converter 931. Take the example of printing.

In this case, the number of samplings, that is, the length of time, of the front end symbol 610 and the rear end symbol 630 is the same. In particular, in FIGS. 6 and 9, it is assumed that the repeating pattern P is 2, and although the repeating pattern P is 2 as shown in FIG. 6, the same pattern is not repeated twice in the symbol. This is because the symbol generated by the aforementioned transmitter may include data to be transmitted to a receiver belonging to the subcarrier set of the second group. Therefore, in the whole symbol, if the receiver belonging to the subcarrier set of the first group only looks at the subcarriers to receive even though there is no repeating pattern in the symbol for the above reason, that is, the subcarrier set of the second group in the entire symbol Symbols except for signals allocated to all receivers belonging to have a repeating pattern.

The serial / parallel converters 921 and 931 input and convert a serial signal (front-end symbol and rear-end symbol) output from the symbol extractor 917 in parallel and then convert the 1/2 FFT units 923. Output each to (933). The 1/2 FFTs 923 and 933 perform the N / 2-point FFT on the signal output from the serial / parallel converters 921 and 931 and then perform the parallel / serial converters 925 ( 935) respectively. The parallel / serial converters 925 and 935 input a parallel signal output from the 1/2 FFTs 923 and 933 to serially convert the channel estimator 929 and the respective channel compensators 927. Are outputted as (937).

The channel estimator 929 performs channel estimation from at least one signal output from the parallel / serial converter 925 and / or the parallel / serial converter 935 and then outputs the channel estimator to the channel compensators. (927) (937). The channel compensators 927 and 937 perform channel compensation on the signal output from the parallel / serial converters 925 and 935 with the channel estimation result output from the channel estimator 929, respectively. Output to (941).

The synthesizer 941 inputs and synthesizes the signals output from the channel compensator 927 and the channel compensator 937 and outputs the synthesized signal to the demodulator 943. The synthesizer 941 synthesizes a front-end symbol output from the channel compensator 927 and a rear-end symbol 630 output from the channel compensator 937 into one full symbol and then transfers the demodulator 943 to the demodulator 943. Output

The demodulator 943 inputs a signal output from the synthesizer 941, demodulates the demodulation method corresponding to the modulation scheme applied by the transmitter, and outputs the demodulation method to the deinterleaver 945.

The deinterleaver 945 deinterleaves the signal output from the demodulator 943 in a deinterleaving scheme corresponding to the interleaving scheme applied by the transmitter, and then outputs the deinterleaver to the decoder 947. The decoder 947 receives a signal output from the deinterleaver 945, decodes the decoding signal corresponding to an encoding scheme applied by the transmitter, and outputs the received data bit.

9 illustrates a receiver structure of an OFDMA communication system according to another exemplary embodiment of the present invention. Next, a method of improving reception performance of an OFDMA symbol in a receiver according to FIG. 9 will be described.

10 is a diagram illustrating a reception signal processing operation of a receiver according to an embodiment of the present invention.

In particular, FIG. 10 illustrates a symbol reception operation that combines in the time domain. In this case, it is assumed that the repetition pattern P determined by the transmitter is 2. FIG. 10, only processes necessary for describing the reception method of the present invention will be described.

Referring to FIG. 10, first, the receiver removes a guard interval of a symbol through the guard interval remover 915 (step 1001). Thereafter, the symbol after removing the guard period is separated into a front end symbol and a rear end symbol through the symbol extractor 917 (step 1003). In this case, when the symbol after removing the protection interval is named as the entire symbol, the entire symbol may be divided into 1/2 corresponding to the repetitive pattern P and divided into the front and rear ends of the symbol. . In this case, as described above, the number of samplings, that is, the time lengths, of the front and rear symbols are the same.

Subsequently, the receiver performs an FFT on each of the front end symbol and the rear end symbol, and converts each of the front end symbol and the rear end symbol in the time domain into a signal in the frequency domain, respectively (step 1005).

Then, the receiver performs channel estimation from the signal in the frequency domain and channel compensation using the value (step 1007). Subsequently, the receiver synthesizes the channel-compensated front-end and rear-end symbols into one full symbol (step 1009), and then performs data bit through general post-processing processes such as a demodulation step, a deinterleaving step, and a decoding step. Outputs

As described above, the present invention can improve signal reception performance only by simple signal processing of a receiver. The effect can result in a reception performance of about 3dB when p = 2. In this case, when the transmitter generates an OFDMA symbol, the transmitter allocates a subcarrier to each receiver in accordance with the rule proposed by the present invention. Through this, reception performance is improved without additional resource consumption, that is, bandwidth or power consumption when generating an OFDMA symbol.

In addition, the above-described transmitter and receiver may be a base station and a mobile terminal, but the mobile terminal and the base station may be transmitters and receivers, respectively. That is, the present invention is applicable to both downlink and uplink.

As described above, in the detailed description of the present invention has been described with respect to specific embodiments, various modifications are possible without departing from the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below, but also by the equivalents of the claims.

1 is a diagram schematically illustrating a transmitter structure for performing a function in an embodiment of the present invention;

2 is a view schematically showing a symbol structure according to an embodiment of the present invention;

3 is a conceptual diagram illustrating a process of assigning an IFFT coefficient to each subchannel in an IFFT device according to an embodiment of the present invention;

4 is a diagram illustrating a symbol generation procedure in a transmitter according to an embodiment of the present invention;

5 is a diagram schematically illustrating a receiver structure for performing a function in an embodiment of the present invention;

6 is a view showing an example of a symbol structure after the removal of the guard interval output from the symbol extractor according to an embodiment of the present invention;

7A is a view illustrating a concept of synthesizing two divided symbols in a symbol synthesizer according to an embodiment of the present invention;

7B is a view showing an example of a symbol output from a symbol stretcher according to an embodiment of the present invention;

8 is a diagram illustrating a reception signal processing operation of a receiver according to an embodiment of the present invention;

9 is a view schematically showing another configuration of a receiver according to an embodiment of the present invention;

10 is a diagram illustrating a received signal processing operation of a receiver according to an embodiment of the present invention.

Claims (23)

A transmitting device of a broadband wireless communication system, The transmitter grouping a subcarrier into a subcarrier set of a first group and a subcarrier set of a second group in response to a repetition pattern to be repeated in a symbol in a time domain; Selecting subcarriers to be allocated to transmission symbols among the subcarrier sets of the first group, and allocating the selected subcarrier sets of the first group to modulation symbols; Selecting subcarriers to be allocated to transmission symbols among the subcarrier sets of the second group and allocating the selected subcarrier sets of the second group to modulation symbols; And transmitting, after inverse fast Fourier transform, the signal to which the subcarrier set of the first group is assigned and the signal to which the subcarrier set of the second group is assigned, after the inverse fast Fourier transform. The method of claim 1, The subcarrier set of the first group is a subcarrier set used for transmitting data bits to a receiver of the first group, and is a subcarrier set having a subcarrier number belonging to an integer multiple of the repeating pattern. Transmission method in the communication system. The method of claim 2, The subcarrier set of the second group is a subcarrier set used to transmit data bits to a receiver of the second group, and the remaining subcarriers other than the subcarrier set belonging to the first group among all available subcarriers are used. A transmission method in a broadband wireless communication system, characterized in that the set. The method of claim 2, And the repeating pattern is an integer of 2 or more. The method of claim 2, After grouping the subcarrier set of the first group and the subcarrier set of the second group, And dividing a receiver group to receive data bits through the subcarrier set of the first group from a receiver group to receive data bits through the subcarrier set of the second group. Transmission method. A receiving device of a broadband wireless communication system, Removing the guard interval of the symbol received from the transmitter; Dividing the symbol after removing the guard section into a front end symbol and a rear end symbol; Generating a composite symbol by synthesizing the front and rear symbols; Restoring the symbol length of the synthesized symbol to the original symbol length; And converting the signal into a signal in a frequency domain after the fast Fourier transform on the one symbol and outputting the data bit through a post-processing procedure. The method of claim 6, The reception method of the broadband wireless communication system, characterized in that for separating the symbols after the guard interval is divided into a front end symbol and a rear end symbol corresponding to the repeating pattern. The method of claim 7, wherein And a time length of the front end symbol and the rear end symbol is the same. The method of claim 8, The front end symbol and the back end symbol has a reception method in a wideband wireless communication system, characterized in that it has at least two patterns of the same type repeated. The method of claim 7, wherein The process of generating the synthesized symbol, Receiving method in the broadband wireless communication system, characterized in that the front end symbol and the rear end symbol having a same starting point to synthesize a single symbol. The method of claim 7, wherein The restoring method may include restoring the synthesized symbol to an original symbol length. A receiving device of a broadband wireless communication system, Removing the guard interval of the symbol received from the transmitter; Dividing one symbol after removing the guard period into a front end symbol and a rear end symbol in a time domain; Converting each of the front end symbol and the rear end symbol of the time domain into a signal of a frequency domain after fast Fourier transform; Synthesizing the front and rear symbols into one whole symbol; And outputting the data bits through the post-processing procedure for the entire symbols. The method of claim 12, The reception method of the broadband wireless communication system, characterized in that for separating the symbols after the guard interval is divided into a front end symbol and a rear end symbol corresponding to the repeating pattern. The method of claim 13, And a time length of the front end symbol and the rear end symbol is the same. The method of claim 13, The front end symbol and the back end symbol has a reception method in a wideband wireless communication system, characterized in that it has at least two patterns of the same type repeated. A receiving device in a broadband wireless communication system, A guard section eliminator which inputs the signal received from the transmitter to remove the guard section and then outputs it; A symbol extractor for separating the symbol after removing the protection section into a front end symbol and a rear end symbol; A symbol synthesizer for synthesizing the front and rear symbols and outputting a synthesized symbol; A symbol stretcher for restoring and outputting the length of the synthesized symbol to an original symbol length; And post-processing devices outputting data bits through post-processing of the signal output from the symbol stretcher. The method of claim 16, And a time length of the front end symbol and the rear end symbol is the same. The method of claim 17, And the front end symbol and the rear end symbol have at least two patterns having the same symbol repeated. 2. The method of claim 16, The symbol synthesizer is a receiving device in a wideband wireless communication system, characterized in that the front end symbol and the rear end symbol having the same starting point to synthesize a single symbol. The method of claim 16, The symbol stretcher recovers a symbol length by copying the synthesized symbol. A receiving device of a broadband wireless communication system, A guard interval eliminator for removing and outputting the guard interval received from the transmitter; A symbol extractor for separating and outputting the symbols after removing the protection section into a front end symbol and a rear end symbol, respectively; A first FFT unit for inputting a signal in which the front-end symbol is converted in parallel, and outputting the N / 2-point fast Fourier transform; A second FFT unit for inputting a signal in which the rear end symbol is converted in parallel and outputting the N / 2-point fast Fourier transform; A synthesizer for synthesizing and outputting the front and rear end symbols respectively inputted from the first and second FFT units into one whole symbol; And a post-processing device for outputting data bits through post-processing of the signal output from the synthesizer. The method of claim 21, And a time length of the front end symbol and the rear end symbol is the same. The method of claim 22, The front end symbol and the rear end symbol has a reception device in a wideband wireless communication system, characterized in that it has at least two patterns of the same type of repeated pattern.

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