KR20060002690A - Apparatus and method for transmitting/receiving pilot signal in a communication system using orthogonal frequency division multiplexing scheme - Google Patents

Abstract

The present invention has a plurality of cells separated by a cell identifier, each of the plurality of cells in a communication system having a plurality of sectors separated by a sector identifier, when a cell identifier and a sector identifier is input, a predetermined block code generation After generating a block code corresponding to the cell identifier using a matrix, generating a Walsh code corresponding to the sector identifier, generating a first part sequence using the block code and the Walsh code, A second part sequence is selected according to the cell identifier and the sector identifier among the sequences. The second part sequence is generated using the first part sequence and the second part sequence as the reference signal in the frequency domain. In the signal transmission section, a fast Fourier transform of the reference signal in the frequency domain to a reference signal in the time domain It is characterized by transmitting after conversion.

Pilot symbol, PAPR sequence, cell ID, sector ID, block code, Walsh basis, mask sequence, IFHT

Description

APPARATUS AND METHOD FOR TRANSMITTING / RECEIVING PILOT SIGNAL IN A COMMUNICATION SYSTEM USING ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SCHEME}             

1 is a view schematically showing all slopes that can be generated in a pilot pattern in a conventional OFDM communication system

2 illustrates an internal structure of a pilot generator of an OFDM communication system according to an embodiment of the present invention.

3 is a diagram illustrating an internal structure of a transmitter of an OFDM communication system according to an embodiment of the present invention.

4 is a diagram illustrating an internal structure of a receiver of an OFDM communication system according to an embodiment of the present invention.

FIG. 5 shows the internal structure of the cell ID / sector ID detector 419 of FIG.

6 is a flowchart illustrating a transmitter operation process in an OFDM communication system according to an embodiment of the present invention.

7 is a flowchart illustrating a receiver operation process in an OFDM communication system according to an embodiment of the present invention.

8 is a diagram schematically illustrating a mapping relationship between subcarriers and pilot symbols when performing an IFFT in an OFDM communication system according to an embodiment of the present invention.

9 illustrates a pilot symbol structure in a time domain of an OFDM communication system according to an embodiment of the present invention.

10 illustrates a pilot symbol structure in a frequency domain of an OFDM communication system according to an embodiment of the present invention.

The present invention relates to a communication system using orthogonal frequency division multiplexing, and more particularly, to an apparatus and method for transmitting and receiving pilot signals for distinguishing a base station and a sector.

In the 4th Generation (hereinafter, referred to as '4G') communication system, users of services having various quality of service (hereinafter referred to as 'QoS') having a high transmission rate are used by users. Active research is underway to provide it. In particular, in 4G communication systems, broadband, such as a wireless local area network (hereinafter referred to as "LAN") system and a wireless metropolitan area network (hereinafter referred to as "MAN") system, are widely used. Researches are being actively conducted to support high-speed services in a form of guaranteeing mobility and QoS in a wireless access (BWA) communication system.

Therefore, in the 4G communication system, orthogonal frequency division multiplexing (OFDM) is actively studied as a method useful for high-speed data transmission in wired and wireless channels. The method uses a multi-carrier to transmit data. A plurality of sub-carriers each having orthogonality to each other by converting serially input symbol strings in parallel. It is a kind of multi-carrier modulation (MCM) that modulates and transmits data.

Broadband spectrum resources are required for the 4G communication system to provide high speed, high quality wireless multimedia services. However, when the broadband spectrum resource is used, fading effects on the radio transmission path due to multipath propagation become serious and frequency selective fading also occurs within the transmission band. Therefore, the OFDM scheme, which is robust against frequency selective fading, has greater gain than the code division multiple access (CDMA) scheme for high-speed wireless multimedia services. There is a trend of being actively used in communication systems.

Here, the operation of the transmitter and the receiver of the communication system using the OFDM scheme (hereinafter referred to as 'OFDM communication system') will be briefly described as follows.

In the transmitter of the OFDM communication system, input data is modulated into subcarriers through a scrambler, an encoder, and an interleaver. In this case, the transmitter provides various variable data rates, and has different coding rates, interleaving sizes, and modulation schemes according to the data rates. Typically, the encoder uses coding rates such as 1/2, 3/4, etc., and the size of the interleaver for preventing burst errors is the number of coded bits per OFDM symbol (NCBPS). Bits per Symbol). In addition, the modulation scheme may be a Quadrature Phase Shift Keying (QPSK) scheme, a Phase Shift Keying (8PSK) scheme, a Quadrature Amplitude Modulation (16QAM) scheme, a 64QAM scheme, or the like, depending on the data rate.

On the other hand, a signal modulated with a predetermined number of subcarriers by the above configurations is added to a predetermined number of pilot subcarriers, which is an Inverse Fast Fourier Transform (IFFT). IFFT is performed to generate one OFDM symbol. Thereafter, a guard band (GB), that is, a guard interval, for removing inter-symbol interference (ISI) in a multi-path channel environment is inserted into the OFDM symbol. The OFDM symbol into which the guard interval signal is inserted is finally input to a radio frequency (RF) processor through a symbol waveform generator. The radio frequency processor wirelessly processes the input signal and transmits the received signal over the air.

Here, the guard interval is inserted to remove intersymbol 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 transmitting the OFDM symbol. In addition, the guard interval is a 'cyclic prefix' scheme in which the last constant samples of the OFDM symbols in the time domain are copied and inserted into a valid OFDM symbol, or the first constant samples of the OFDM symbols in the time domain. It is inserted in a 'cyclic postfix' manner in which it is copied and inserted into a valid OFDM symbol.

The receiver of the OFDM communication system corresponding to the transmitter as described above performs an inverse process to the process performed by the transmitter, and further performs a synchronization process.

In more detail, first, a process of estimating a frequency offset and a symbol offset using a training symbol preset for a received OFDM symbol should be preceded. Subsequently, the data symbol from which the guard interval is removed is recovered to a predetermined number of subcarriers to which a predetermined number of pilot subcarriers are added through a Fast Fourier Transform (FFT). Also, in order to overcome the path delay phenomenon on the actual radio channel, the equalizer estimates the channel state of the received channel signal to remove the signal distortion on the actual radio channel from the received channel signal. The channel estimated data through the equalizer is converted into a bit stream, passed through a de-interleaver, and then through a decoder and a descrambler for error correction. The final data is output.

Meanwhile, as described above, in an OFDM communication system, a transmitter such as a base station (BS) transmits pilot subcarrier signals to a receiver such as a terminal. The base station transmits the data subcarrier signals simultaneously with the pilot subcarrier signals. The reason for transmitting the pilot subcarrier signals is for synchronization acquisition, channel estimation, and base station division. That is, the pilot subcarrier signal is a kind of reference sub-carrier signal. The pilot subcarrier signals operate as a training sequence to perform channel estimation between the transmitter and the receiver, and also allow the terminal to identify the base station to which the terminal belongs by using the pilot subcarrier signals. . The position at which the pilot subcarrier signals are transmitted is pre-defined between the transmitter and the receiver. As a result, the pilot subcarrier signals operate as a kind of reference signal.

Next, an operation of identifying a base station to which a terminal belongs by using the pilot subcarrier signals will be described.

First, a base station may reach a cell boundary with a relatively high transmit power compared to the data subcarrier signals while the pilot subcarrier signals have a specific pattern, that is, a pilot pattern. Send it to be. Here, the base station transmits the pilot subcarrier signals to reach a cell radius with a relatively high transmission power while having a specific pilot pattern as follows.

First, when the terminal enters a cell, the terminal does not have any information about the base station to which the terminal currently belongs. The terminal must use the pilot subcarrier signals to detect the base station to which the terminal belongs, so that the base station transmits the pilot subcarrier signals at a relatively high transmit power while having a specific pilot pattern. Allow the terminal to detect the base station to which the terminal belongs.

Meanwhile, the pilot pattern refers to a pattern generated by pilot subcarrier signals transmitted from a base station. That is, the pilot pattern is determined by a slope of the pilot subcarrier signals and a start point at which the pilot subcarrier signals begin to be transmitted. Thus, the OFDM communication system must be designed such that each of the base stations has a different pilot pattern to distinguish each of the base stations constituting the OFDM communication system. In addition, the pilot pattern is generated in consideration of a coherence bandwidth and a coherence time. Next, the coherence bandwidth and the coherence time will be described.

The coherence bandwidth represents the maximum bandwidth that can be assumed to be constant in the frequency domain. The coherence time represents the maximum time that can be assumed that the channel does not change in the time domain. Since it can be assumed that the channel does not change within the coherence bandwidth and the coherence time, even if only one pilot subcarrier signal is transmitted during the coherence bandwidth and the coherence time, synchronization acquisition and channel estimation and base station Division etc. becomes possible.

Thus, since only one pilot subcarrier signal is transmitted, transmission of data subcarrier signals can be maximized, thereby improving system overall performance. As a result, the maximum frequency interval for transmitting the pilot subcarrier signal is a coherence bandwidth, and the maximum time interval for transmitting the pilot subcarrier signal, that is, the maximum OFDM symbol time interval, is the coherence time.

On the other hand, the number of base stations constituting the OFDM communication system varies depending on the size of the OFDM communication system, but typically increases as the size of the OFDM communication system increases. Therefore, in order to distinguish each of the base stations, pilot patterns having different slopes and starting points must exist as many as the base stations. However, in order to transmit a pilot subcarrier signal in a time-frequency domain in the OFDM communication system, a coherence bandwidth and a coherence time must be considered as described above, and the coherence bandwidth and In consideration of the coherence time, pilot patterns having different slopes and starting points are generated in a limited manner. When generating a pilot pattern without considering the coherence bandwidth and the coherence time, pilot subcarrier signals in pilot patterns representing different base stations are mixed, and in this case, it is necessary to distinguish the base stations using the pilot pattern. impossible.

Next, with reference to FIG. 1, when a pilot subchannel is used in a typical OFDM communication system, a position in which pilot subcarriers are transmitted according to a pilot pattern will be described.

FIG. 1 is a diagram schematically showing locations where pilot subcarriers are transmitted according to a pilot pattern when using one pilot subchannel in a conventional OFDM communication system.

Referring to FIG. 1, the slopes and the number of slopes that can be generated in the pilot pattern, that is, the slopes and the number according to the pilot subcarrier signal transmission are determined according to the coherence bandwidth 100 and the coherence time 110. Limited. In FIG. 1, when the coherence bandwidth 110 is 6 and the coherence time 110 is 1, assuming that the slope of the pilot pattern is an integer, the slope of the pilot pattern that may occur under the above condition is s = There are six numbers from 0 (101) to s = 5 (106). That is, the slope of the pilot pattern that can be generated under the above condition is any integer value from 0 to 5.

In this way, the six possible slopes of the pilot pattern means that the number of base stations that can be distinguished using the pilot pattern in the OFDM communication system satisfying the condition is six. In addition, the diagonally processed circles 107 illustrated in FIG. 1 represent pilot subcarrier signals spaced apart by the coherence bandwidth 100. As a result, the slope of the pilot pattern is limited to the coherence versus bandwidth 100.

As described above, the pilot pattern used to distinguish the base stations constituting the OFDM communication system in the OFDM communication system is generated by being limited to the coherence bandwidth and the coherence time. Occurs. Thus, when the number of base stations constituting the OFDM communication system increases, there is a problem in that a limit occurs in the number of distinguishable base stations due to a limitation in the number of patterns that can be generated.

Accordingly, an object of the present invention is to provide an apparatus and method for transmitting and receiving pilot signals for base station and sector classification in an OFDM communication system.

Another object of the present invention is to provide an apparatus and method for transmitting and receiving pilot signals to minimize mutual interference in an OFDM communication system.

Another object of the present invention is to provide an apparatus and method for transmitting and receiving pilot signals having a variable length in an OFDM communication system.

Another object of the present invention is to provide an apparatus and method for transmitting and receiving pilot signals using a block code generated by using a Walsh basis and a mask sequence in an OFDM communication system.

The method of the present invention for achieving the above objects; In a communication system having a plurality of cells separated by a cell identifier, wherein each of the plurality of cells is divided by a sector identifier, a reference signal for distinguishing each of the cells and sectors is one or more transmission antennas In the method of transmitting through a cell identifier and a sector identifier, a block code corresponding to the cell identifier is generated using a preset block code generation matrix, and a Walsh code is generated corresponding to the sector identifier. After that, generating a first part sequence using the block code and Walsh code, selecting a second part sequence corresponding to the cell identifier and the sector identifier among preset sequences; Generating the reference signal in the frequency domain by using the one-part sequence and the second part sequence; In the reference signal transmission period is set, the reference signal in the frequency domain, an inverse fast Fourier transform is characterized in that it comprises the step of transmitting the reference signal after conversion to the time domain.

Another method of the present invention for achieving the above objects is; In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells having a plurality of sectors separated by a sector identifier, wherein the entire frequency band is divided into a subcarrier bands, the cells and sectors In the method of transmitting a reference signal for distinguishing each of the above, when a cell identifier is input, generating a block code corresponding to the cell identifier using a preset block code generation matrix, and when a sector identifier is input, Selecting a Walsh code corresponding to the sector identifier among the pre-set Walsh codes, repeating the pre-set number of times, interleaving the block code in a pre-set interleaving scheme, and interleaving the interleaved block code. And an exclusive OR of the repeated Walsh codes to generate a first part sequence. And selecting a second part sequence corresponding to the cell identifier and the sector identifier among preset sequences, and generating the reference signal in the frequency domain using the first part sequence and the second part sequence. And converting the reference signal in the frequency domain into an inverse fast Fourier transform into a reference signal in the time domain in a preset reference signal transmission interval and transmitting the same.

Another method of the present invention for achieving the above objects is; In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells having a plurality of sectors separated by a sector identifier, wherein the entire frequency band is divided into a subcarrier bands, the cells and sectors A method of receiving a reference signal for distinguishing each of the plurality of signals, the method comprising: extracting the reference signal from a fast Fourier transformed received signal, and pre-setting a Walsh code corresponding to an arbitrary sector identifier among preset Walsh codes; Repeating a predetermined number of times, dividing the reference signal by a predetermined set interval unit, and performing an exclusive OR with the repeated Walsh code; and a corresponding deinterleaving method with the exclusive AND The deinterleaving signal and the deinterleaved signal Dividing the sub-block signals according to the block code generation matrix, performing inverse fast Hadamard transformation using each of the mask sequences generated under a predetermined control, and performing the sub-block signals. Combining the high-speed Hadamard transformed signals with respect to each of the block signals to generate combined signals; a cell identifier corresponding to a block code having a maximum correlation value among the combined signals as a final cell identifier, and the maximum correlation And detecting the sector identifier corresponding to the Walsh code having the value as the final sector identifier.

The apparatus of the present invention for achieving the above objects; An apparatus for transmitting a reference signal for distinguishing each of the cells and sectors in a communication system having a plurality of cells separated by a cell identifier, each cell having a plurality of sectors separated by a sector identifier, When a cell identifier and a sector identifier are input, a block code is generated corresponding to the cell identifier using a preset block code generation matrix, a Walsh code is generated corresponding to the sector identifier, and then the block code and the Walsh code are generated. Generates a first part sequence using the first part sequence and the reference signal in the frequency domain using the second part sequence selected corresponding to the cell identifier and the sector identifier among preset sequences The reference signal generator and the frequency domain in a preset reference signal transmission interval. And a transmitter for converting the reference signal of the inverse fast Fourier transform into a reference signal in the time domain and then transmitting.

Another apparatus of the present invention for achieving the above objects; In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells having a plurality of sectors separated by a sector identifier, wherein the entire frequency band is divided into a subcarrier bands, the cells and sectors In the apparatus for transmitting a reference signal for distinguishing each of the above, when a cell identifier is input, a block code encoder for generating a block code corresponding to the cell identifier using a preset block code generation matrix, and a sector identifier A Walsh code repeater that selects a Walsh code corresponding to the sector identifier among the pre-set Walsh codes and repeats the preset number of times; an interleaver for interleaving the block code in a pre-set interleaving scheme; Exclusive of the interleaved block code and the repeated Walsh code Using an adder for generating a first part sequence by OR and a second part sequence selected corresponding to the cell identifier and the sector identifier among preset sequences, the reference part in the frequency domain And a transmitter for generating a combiner and a transmitter for transmitting a reference signal in the frequency domain by inverse fast Fourier transformation in a predetermined reference signal transmission period, converting the reference signal into a reference signal in the time domain.

Another apparatus of the present invention for achieving the above objects is; In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells having a plurality of sectors separated by a sector identifier, wherein the entire frequency band is divided into a subcarrier bands, the cells and sectors An apparatus for receiving a reference signal for distinguishing each of the following apparatuses, comprising: a fast Fourier transformer for fast Fourier transforming a received signal, a reference signal extractor for extracting the reference signal from the fast Fourier transformed signal, and a pre-set Walsh code A Walsh code repeater for repeating a predetermined number of times the Walsh code corresponding to a predetermined sector identifier, an adder for performing an exclusive OR on the repeated Walsh code by dividing the reference signal by a predetermined set interval unit; Deinterleaving the exclusive OR signal in advance. A deinterleaver for deinterleaving according to an equation, a subblock divider for dividing the deinterleaved signal into subblock signals corresponding to a predetermined block code generation matrix, and each of the subblock signals to a predetermined control A block code decoder for performing inverse fast Hadamard transform using each of the mask sequences generated according to the result, a combiner for combining the inverse fast Hadamard transformed signals with respect to each of the subblock signals to generate combined signals, and And a comparison selector for detecting a cell identifier corresponding to the block code having the maximum correlation value among the combined signals as the final cell identifier and a sector identifier corresponding to the Walsh code having the maximum correlation value as the final sector identifier. do.

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

The present invention relates to a base station (BS) in a communication system (hereinafter referred to as an 'OFDM communication system') using an orthogonal frequency division multiplexing (OFDM) scheme. And a method of transmitting and receiving a pilot signal for sector division. In particular, the present invention proposes a method for transmitting and receiving a pilot signal that can minimize the interference while performing the base station and sector classification.

2 is a diagram illustrating the internal structure of a pilot generator of an OFDM communication system according to an embodiment of the present invention.

Referring to FIG. 2, the pilot generator includes a block code encoder 201, an interleaver 203, a Walsh code repeater 205, The adder 207 and the combiner 209 are comprised.

First, a cell identifier (ID) (hereinafter, referred to as 'ID') is an ID for identifying a cell, that is, a base station (BS), and the cell ID is the block code encoder 201. Is entered. As the cell ID is input, the block code encoder 201 generates a codeword corresponding to the cell ID, that is, a block code, from the generator matrix G, which is already stored, and then the interleaver 203. ) The generation matrix G is generated such that each of the block codes generated corresponding to the cell ID can be clearly distinguished from each other. The generation matrix G will be described with reference to Table 1 below.                     

개의 셀들을 구별할 수 있다. 상기 생성 행렬 G의 N_c개의 열들을 a개의 서브 블록(sub-block)들로 구분되고, 따라서 상기 a개의 서브 블록들 각각은

의 길이를 갖으며, 상기 길이

가 채널의 코히어런스 대역폭(coherence bandwidth) 미만이 되도록 설계된다. 상기 a개의 서브 블록들 각각은

개의 왈쉬 기저(Walsh basis)들과 n개의 마스크 시퀀스(mask sequence)들 로 구성된다. 여기서, 상기 a개의 서브 블록들 각각을 구성하는 왈쉬 기저들은 모두 동일한 왈쉬 기저들이며, 상기 마스크 시퀀스들의 개수 n은

와 같다. 상기 표 1에서 마스크_(p)는 제p마스크 시퀀스를 나타내며, 상기 생성 행렬 G에서 제2서브 블록은 제1서브 블록의 행들이 n-1번 순환 쉬프트(cyclic shift)되어 생성되며, 상기와 같은 방식으로 제m서브 블록은 제1서브 블록의 행들이 n-j번 순환 쉬프트되어 생성된다. 상기 순환 쉬프트 동작은 상기 생성 행렬 G를 사용하여 생성되는 블록 코드의 최소 거리(minimum distance)를 최대화시키는 형태로 수행되는 것이다. First, assuming that the number of rows of the generation matrix G is N _r and the number of columns is N _c , the length N _G of the block code that can be generated using the generation matrix _G is the generation. Equivalent to N _c , the number of columns in the matrix G. In addition, the pilot symbol generated by the block code is the maximum

Cells can be distinguished. N _c columns of the generation matrix G are divided into a sub-blocks, and thus each of the a sub-blocks

Has a length of and the length

Is designed to be less than the coherence bandwidth of the channel. Each of the a sub blocks

It consists of Walsh basis and n mask sequences. Here, the Walsh bases constituting each of the a sub-blocks are all the same Walsh bases, and the number n of the mask sequences is

Same as In Table 1, mask _(p) represents a pth mask sequence, and the second sub block in the generation matrix G is generated by cyclically shifting the rows of the first sub block n-1 times. In this manner, the m-th sub block is generated by shifting the rows of the first sub block nj times. The cyclic shift operation is performed in a form of maximizing a minimum distance of a block code generated using the generation matrix G.

The interleaver 203 inputs a signal output from the block code encoder 201, interleaves the interleaving method in a predetermined interleaving manner, and outputs the signal to the adder 207. Here, the reason why the interleaver 203 interleaves the signal output from the block code encoder 201 is that the block code generated by the block code encoder 201, that is, corresponding to the specific cell ID, is generated in a specific pattern. This is because the peak-to-average power ratio (PAPR) will be high when the numeric string has a feature that is frequently repeated. That is, the interleaver 203 controls to improve the pilot PAPR characteristic of the OFDM communication system by interleaving all block codes generated by the block code encoder 201.

Next, the internal structure of the interleaver 203 will be described below.                     

First, the interleaver 203 has a internal interleaver (not shown) therein and interleaves a signal generated through each of the a subblocks of the generation matrix G. That is, the block code output from the block code encoder 201 is divided into a sub-codes, and each of the a sub-codes is interleaved differently in each of the a internal interleavers. Since the interleaver 203 performs interleaving on each of the a subcodes of the block code, the receiver will use the Walsh basis to call an Inverse Fast Hadamard Transform (IFHT). ), It is possible to decode the information data corresponding to the block code transmitted from the transmitter side.

On the other hand, a sector ID is an ID for identifying a sector, and the sector ID is input to the Walsh code repeater 205. When the sector ID is input, the Walsh code repeater 205 repeats the Walsh code corresponding to the sector ID a predetermined number of times and outputs the Walsh code iterator to the adder 207.

번 반복하여 출력한다. 여기서, 상기 왈쉬 코드 반복기(205)에서 출력하는 신호의 길이는 상기 인터리버(203)에서 출력하는 신호의 길이 N_G와 동일하다. In an embodiment of the present invention, a pilot signal of the OFDM communication system, for example, a pilot symbol length is N _P , a block code length generated by the block code encoder 201 is N _G , and the Walsh code is used. It is assumed that the length of is N _W. In this case, the Walsh code iterator 205 generates a Walsh code corresponding to the sector ID.

Repeat the output once. Here, the length of the signal output from the Walsh code repeater 205 is equal to the length N _G of the signal output from the interleaver 203.

The adder 207 calculates an exclusive OR (XOR) operation of the signal output from the interleaver 203 and the signal output from the Walsh code repeater 205 and outputs the result to the combiner 209.

이 된다.Meanwhile, the PAPR reduction sequence is a sequence for reducing PAPR of pilot symbols in the OFDM communication system, and the length of the PAPR reduction sequence is N _R. Here, it is assumed that the PAPR reduction sequence is predetermined according to the cell ID and the sector ID. The PAPR reduction sequence will be described in detail below, and thus a detailed description thereof will be omitted. The PAPR reduction sequence having the length N _R is input to the combiner 209, and the combiner 209 generates a pilot symbol by allocating a signal output from the adder 207 and the PAPR sequence to a corresponding subcarrier. Output Here, the length of the pilot symbol output from the combiner 209 is

Becomes

2 illustrates the internal structure of a pilot generator of an OFDM communication system according to an embodiment of the present invention. Next, an internal structure of a transmitter of the OFDM communication system according to an embodiment of the present invention will be described with reference to FIG. do.

3 is a diagram illustrating an internal structure of a transmitter of an OFDM communication system according to an embodiment of the present invention.

Referring to FIG. 3, the transmitter includes a modulator 301, a pilot generator 303, a modulator 305, a selector 307, and a serial to parallel converter ( 309, an Inverse Fast Fourier Transform (IFFT), 311, a parallel to serial converter 313, and a guard interval inserter. a guard interval inserter 315, a digital to analog converter 317, and a radio frequency (RF) processor (319). It is composed.

First, when data to be transmitted, that is, information data bits, the information data bits are input to the modulator 301. The modulator 301 modulates the input information data bits in a predetermined modulation scheme to generate a modulation symbol and outputs the modulated symbols to the selector 307. Here, the modulation scheme may be a quadrature phase shift keying (QPSK) scheme or a quadrature amplitude modulation (16QAM) scheme.

In addition, when a pilot symbol is to be transmitted, a cell ID of a cell sector, a sector ID, and a PAPR reduction sequence preset in correspondence with the cell ID and sector ID are transmitted to the pilot generator 303. Is entered. The pilot generator 303 generates the input cell ID, the sector ID and the PAPR reduction sequence as pilot symbols, and outputs the pilot symbols to the modulator 305. Here, the internal structure of the pilot generator 303 is as described in FIG. The modulator 305 inputs a signal output from the pilot generator 303, modulates the signal by a preset modulation scheme, generates a modulation symbol, and outputs the modulated symbol to the selector 307. Here, a binary phase shift keying (BPSK) scheme may be used as the modulation scheme.

The selector 307 controls the transmitter to output the signal output from the modulator 301 to the serial / parallel converter 309 when the transmitter is in a data symbol transmission interval in which a current data symbol should be transmitted. In the pilot symbol transmission period in which the transmitter should transmit the current pilot symbol, the transmitter outputs the signal output from the modulator 305 to the serial / parallel converter 309. The serial / parallel converter 309 receives the serial modulation symbols output from the selector 307, converts them in parallel, and then outputs them to the IFFT unit 311. The IFFT unit 311 inputs a signal output from the serial / parallel converter 309 to perform an N-point IFFT and then outputs it to the parallel / serial converter 313.

The parallel / serial converter 313 inputs the signal output from the IFFT device 311 and serially converts the signal, and outputs the serial signal to the guard interval inserter 315. The guard interval inserter 315 inputs a signal output from the parallel / serial converter 313 to insert a guard interval, that is, a guard band (GB) signal, and then to the digital / analog converter 317. Output Here, the guard interval is inserted to remove interference between the OFDM symbol transmitted at the previous OFDM symbol time and the current OFDM symbol transmitted at the current OFDM symbol time when the OFDM symbol is transmitted in the OFDM communication system. . In addition, the guard interval is valid by copying the last predetermined samples of the OFDM symbols in the time domain and inserting them into the valid OFDM symbols or by copying the first predetermined samples of the OFDM symbols in the time domain. It is inserted using any one of the 'Cyclic Postfix' method of inserting the OFDM symbol. The signal output from the guard interval inserter 315 results in one OFDM symbol.

The digital-to-analog converter 317 inputs the signal output from the guard period inserter 315 and converts the signal to the radio frequency processor 319. Here, the RF processor 319 may include components such as a filter and a front end unit, and may transmit a signal output from the digital-to-analog converter 317 on actual air. After RF processing, the antenna transmits the air through an antenna.

3 illustrates the internal structure of a transmitter of an OFDM communication system according to an embodiment of the present invention. Next, the internal structure of a receiver of an OFDM communication system according to an embodiment of the present invention will be described with reference to FIG. .

4 is a diagram illustrating an internal structure of a receiver of an OFDM communication system according to an embodiment of the present invention.

Referring to FIG. 4, the receiver includes an RF processor 401, an analog / digital converter 403, a guard interval remover 405, and a serial / parallel converter. 407, Fast Fourier Transform (FFT), 409, parallel / serial converter 411, selector 413, and demodulator (de-modulator). And a cell ID / sector ID detector 419.                     

First, a signal transmitted from a transmitter of the OFDM communication system is received through an antenna of the receiver in the form of a multipath channel and a noise component added thereto. The signal received through the antenna is input to the RF processor 401, and the RF processor 401 down converts the signal received through the antenna to an intermediate frequency (IF) band. After the output to the analog-to-digital converter 403. The analog / digital converter 403 digitally converts the analog signal output from the RF processor 301 and outputs the digital signal to the guard interval remover 405.

The guard interval remover 405 removes the guard interval signal by inputting the signal output from the analog / digital converter 403 and outputs the signal to the serial / parallel converter 407. The serial / parallel converter 407 inputs a serial signal output from the guard interval eliminator 405 to perform parallel conversion and outputs the serial signal to the FFT unit 409. The FFT unit 409 outputs the signal output from the serial / parallel converter 407 to the parallel / serial converter 411 after performing an N-point FFT.

The parallel / serial converter 411 inputs a parallel signal output from the FFT unit 409, serially converts the same, and outputs the serial signal to the selector 413. The selector 413 controls to output the signal output from the FFT unit 409 to the demodulator 415 when the receiver is in a data symbol reception interval in which the receiver should receive the current data symbol, and the receiver outputs the current pilot symbol. In the pilot symbol reception period to receive the signal, the signal output from the FFT unit 409 is controlled to be output to the demodulator 417. The demodulator 415 demodulates the signal output from the FFT unit 409 corresponding to the modulation scheme applied by the transmitter and restores the data, that is, the information data bits.

On the other hand, the demodulator 417 demodulates the signal output from the FFT unit 409 corresponding to the modulation scheme applied by the transmitter to restore the pilot and outputs the signal to the cell ID / sector ID detector 419. The cell ID / sector ID detector 419 inputs a pilot signal output from the demodulator 417 to detect a cell ID and a sector ID corresponding to the pilot signal. Here, the pilot signal is a signal generated corresponding to the cell ID and the sector ID, and is mutually regulated between the transmitter and the receiver.

In FIG. 4, the internal structure of the receiver of the OFDM communication system according to the embodiment of the present invention has been described. Next, the internal structure of the cell ID / sector ID detector 419 of FIG. 4 will be described with reference to FIG. .

5 is a diagram illustrating an internal structure of the cell ID / sector ID detector 419 of FIG. 4.

Referring to FIG. 5, the cell ID / sector ID detector 419 includes a pilot extractor 501, a Walsh code iterator 503, an adder 505, a de-interleaver 507, And a sub-block segment unit 509, a block code decoder 511, a combiner 523, and a comparison selector 525. The block code decoder 511 includes a multiplier 513, a mask sequence generator 515, an IFHT generator 517, a memory 519, and a controller 521.                     

First, the signal output from the demodulator 417 of FIG. 4 is input to the pilot extractor 501, and the pilot extractor 501 inputs the signal output from the demodulator 417 to remove the PAPR reduction sequence. N _G symbols are extracted and output to the adder 505. In addition, the Walsh code repeater 503 repeatedly outputs Walsh codes corresponding to all distinguishable sector IDs, and the receiver sequentially selects one Walsh code among the Walsh codes corresponding to all sector IDs. After repeating the output to the adder 505.

The adder 505 performs an exclusive OR operation on the signal output from the pilot extractor 501 and the signal output from the Walsh code repeater 503 and then outputs the deinterleaver 507. The deinterleaver 507 deinterleaves the signal output from the adder 505 using a deinterleaving method corresponding to the interleaving method applied to the interleaver inside the pilot generator of the transmitter, that is, the interleaver 203 of FIG. 2. After that, the data is output to the subblock divider 509.

The sub block divider 509 inputs the signal output from the deinterleaver 507 and divides the signal into sub blocks such as the block code generation matrix G on the transmitter side as described in Table 1 above. That is, the signal is divided into a subblocks and sequentially output to the block code decoder 511. Here, the sub block divider 509 divides the signal output from the deinterleaver 507 into a sub blocks, stores each of the a sub blocks in an internal memory (not shown). The sub blocks are sequentially delayed from the first sub block among the a sub blocks until the a sub block, which is the last sub block, is output to the block code decoder 511.

The signal output from the sub-block divider 509 is input to the multiplier 513 of the block code decoder 511, and the multiplier 513 outputs the mask sequence and the sub-block output from the mask sequence generator 515. The signal output from the divider 509 is multiplied and then output to the IFHT divider 517. Here, the mask sequence generator 515 sequentially generates each of the mask sequences used in the block code generation matrix G on the transmitter side and outputs them to the multiplier 513 under the control of the controller 521.

The IFHT 517 inputs the signal output from the multiplier 513 to perform an IFHT operation and outputs the signal to the memory 519. The memory 519 stores the signal output from the IFHT device 517 and outputs the signal to the controller 521 again. The controller 521 controls the mask sequence generation operation of the mask sequence generator 515. In addition, the controller 521 stores the deinterleaver 507 stored in the memory 519 after the mask sequence generator 515 generates all mask sequences used in the block code generation matrix G on the transmitter side. The output value of the IFHT group 517 corresponding to the mask sequences of the corresponding sub block of the output signal is controlled to be output to the combiner 523.

The combiner 523 stores the signal output from the controller 521, that is, the controller 521 stores the signals output for each of the sub-blocks of the deinterleaver 507 output signal. The output values output from the IFHT group 517 are combined and output to the comparison selector 525 corresponding to the block code generation matrix G of the transmitter.

The comparison selector 525 selects a correlation value having a maximum value among the output correlation values of the combiner 523 for the block codes corresponding to all the cell IDs and the Walsh codes corresponding to all the sector IDs. The cell ID and sector ID corresponding to the selected maximum correlation value are detected and output as the last cell ID and the last sector ID.

In FIG. 5, the internal structure of the cell ID / sector ID detector 419 of FIG. 4 has been described. Next, a transmitter operation process in an OFDM communication system according to an embodiment of the present invention will be described with reference to FIG. 6. .

6 is a flowchart illustrating a transmitter operation process in an OFDM communication system according to an embodiment of the present invention.

In FIG. 6, only the pilot signal transmission operation of the transmitter will be described. Referring to FIG. 6, in step 611, the transmitter generates a pilot symbol using a cell ID, a sector ID, and a PAPR reduction sequence of the transmitter, and then proceeds to step 613. Since the operation of generating the pilot symbol is the same as described with reference to FIG. 2, the detailed description thereof will be omitted. In step 613, the transmitter modulates the generated pilot symbol into a modulation scheme, such as a BPSK scheme, which is generated in advance.

In step 615, the transmitter terminates after transmitting the modulated symbol-converted pilot symbol in a pilot symbol period. Of course, although not separately illustrated in FIG. 6, a frequency offset may be considered in transmitting the pilot symbol. That is, the position at which the pilot symbol starts may be different for each cell and sector.

In FIG. 6, a transmitter operation process in an OFDM communication system according to an embodiment of the present invention has been described. Next, a receiver operation process in an OFDM communication system according to an embodiment of the present invention will be described with reference to FIG. 7. .

7 is a flowchart illustrating a receiver operation process in an OFDM communication system according to an embodiment of the present invention.

In FIG. 7, only the pilot signal reception operation of the receiver will be described. Referring to FIG. 7, first, in step 711, the receiver receives a pilot symbol in a pilot symbol period and then proceeds to step 713. Although not separately illustrated in FIG. 7, when the transmitter transmits the pilot symbol in consideration of the frequency offset as described in FIG. 6, the receiver determines the position according to the frequency offset and then receives the pilot symbol. Of course it can. In step 713, the receiver demodulates the pilot symbols according to the modulation scheme applied by the transmitter, and then proceeds to step 715. In step 715, the receiver correlates the demodulated pilot symbols with block codes corresponding to all cell IDs distinguishable from the receiver and Walsh codes corresponding to all sector IDs, and thereafter, a maximum correlation value among them. The cell ID and the sector ID having are detected as the cell ID and the sector ID of the transmitter and then terminate.

In FIG. 7, a receiver operation process in an OFDM communication system according to an embodiment of the present invention has been described. Next, subcarriers and pilot symbols are performed when performing IFFT in an OFDM communication system according to an embodiment of the present invention. The mapping relationship with will be described.

8 is a diagram illustrating a mapping relationship between subcarriers and pilot symbols when performing an IFFT in an OFDM communication system according to an embodiment of the present invention.

In FIG. 8, when the total number of subcarriers used in the OFDM communication system is 128 and the number of subcarriers actually used among the 128 subcarriers is 108, that is, subcarriers -54 to -1 Assume that 54 subcarriers up to a carrier and 54 subcarriers from subcarriers 1 to 54 are used, that is, 108 subcarriers in total. In FIG. 8, the number k on the top of the input terminal of the IFFT unit represents an index of subcarriers of the OFDM communication system. In addition, since subcarrier # 0 represents a reference point of the pilot symbol in the time domain, that is, a DC component in the time domain after performing the IFFT, null data is inserted into the subcarrier # 0.

Further, the 108 subcarriers actually used, subcarriers except the subcarrier 0, that is, subcarriers from sub-55 subcarrier to sub-64 subcarrier, subcarriers 55 through 63 Null data is also inserted in the subcarriers up to the subcarrier.                     

Here, the reason why null data is inserted into subcarriers from subcarriers -55 to -64 and subcarriers from subcarriers 55 to 63 is described. The subcarriers up to subcarrier 64 and the subcarriers up to subcarrier 55 through 63 are adjacent to the frequency band of another system, so the interference with other systems is minimized. Thus, when a pilot symbol in the frequency domain is input to the IFFT device, the IFFT device maps the pilot symbols in the frequency domain to the corresponding subcarriers to perform IFFT and outputs the pilot symbols in the time domain.

8 illustrates a mapping relationship between subcarriers and pilot symbols when performing an IFFT in an OFDM communication system according to an embodiment of the present invention. Next, an OFDM communication system according to an embodiment of the present invention will be described with reference to FIG. The pilot symbol structure in the time domain will be described.

9 illustrates a pilot symbol structure in a time domain of an OFDM communication system according to an embodiment of the present invention.

길이의 심벌이 2번 반복된 형태를 가지며, OFDM 통신 시스템의 특성상 상기에서 설명한 바와 같은 Cyclic Prefix(CP) 방식으로 삽입된 보호 구간 신호가 상기

길이의 심벌이 2번 반복된 형태의 전단에 첨가되어 있다. 여기서, 상기 N_FFT는 상기 OFDM 통 신 시스템에서 사용하는 IFFT기/FFT기의 포인트 수를 나타낸다. 즉, 상기 도 8에서도 설명한 바와 같이 상기 OFDM 통신 시스템에서 사용하는 IFFT기/FFT기의 포인트 수가 128이므로 상기 p_c의 길이는 64가 되는 것이다. 9, the pilot symbol is of length p _c , that is,

The symbol of length has a form repeated twice, and the guard interval signal inserted in the Cyclic Prefix (CP) method as described above is a characteristic of the OFDM communication system.

A symbol of length is added to the front end of the form repeated twice. Here, the N _FFT represents the number of points of the IFFT / FFT group used in the OFDM communication system. That is, as described in FIG. 8, the length of p _c is 64 since the number of points of the IFFT / FFT group used in the OFDM communication system is 128.

9 illustrates a pilot symbol structure in a time domain of an OFDM communication system according to an embodiment of the present invention. Next, with reference to FIG. 10, a pilot symbol in a frequency domain of an OFDM communication system according to an embodiment of the present invention. The structure will be described.

10 illustrates a pilot symbol structure in a frequency domain of an OFDM communication system according to an embodiment of the present invention.

Referring to FIG. 10, first, guard bands (GB) 1001 and 1007, that is, subcarrier intervals excluding guard intervals, are largely classified into a correlation interval 1003 and a PAPR interval 1005. . The correlation section 1003 includes a sequence having a large correlation value, that is, a sequence generated by combining a block code and Walsh codes, and the PAPR section 1005 corresponds to each of the sequences constituting the correlation section 1003. It consists of a PAPR reduction sequence.

As shown in FIG. 10, the pilot symbol includes a first part sequence, that is, a sequence corresponding to the correlation interval 1003, and a second part sequence, that is, a sequence corresponding to the PAPR interval 1005. Here, a sequence inserted into the correlation section 1003, that is, a sequence output from the adder 207 of FIG. 2 will be referred to as a "correlation sequence". The correlation value calculation using the IFHT described with reference to FIG. 5 is performed only for the correlation section 1003.

은 길이 48의 인터리빙 방식을 나타내며, 상기

에 상응하게 상기 길이 48인 블록 코드가 인터리빙된다. 또한, 상기 도 10에서

은 왈쉬 코드 마스킹(masking)을 나타낸다. In FIG. 10, C represents a block code having a length of 48.

Denotes an interleaving scheme of length 48, and

Correspondingly, the block code of length 48 is interleaved. In addition, in FIG.

Denotes Walsh code masking.

Meanwhile, the pilot symbol is generated by a frequency domain sequence as shown in Equation 1 below.

는 짝수 인덱스를 가지는 서브 캐리 어들에만 상기 수학식 1과 같은 형태로 값이 부여되고 홀수 인덱스를 가지는 서브 캐리어들에는 무조건 0의 값이 부여되므로, IFFT 연산을 수행할 경우 시간 영역에서 동일한 시퀀스가 2회 반복되는 형태를 가지게 된다.In Equation 1, ID _cell represents a cell ID, s represents a sector ID, k represents a subcarrier index, and N _used represents the number of subcarriers actually _used in the OFDM communication system, that is, a DC component and protection. The number of subcarriers excluding the interval component is shown. In the embodiment of the present invention, it is assumed that pilot symbols of all base stations and sectors use the same frequency offset. Sequence of frequency domain as shown in Equation 1 above

Since a value is given only to subcarriers having an even index in the form of Equation 1 above, and a value of 0 is unconditionally given to subcarriers having an odd index, the same sequence in the time domain is 2 when the IFFT operation is performed. It will have a repeated form.

는 파일럿 심벌의 송신 전력 레벨이 상기 파일럿 심벌 구간 이외의 구간, 즉 데이터 심벌 구간에서 송신되는 데이터 심벌의 송신 전력 레벨과 동일한 송신 전력 레벨을 가지도록 하기 위해 설정되는 가중치이며,

은 하기 수학식 2와 같이 정의된다.In addition, in Equation 1

Is a weight set to have a transmit power level of a pilot symbol equal to a transmit power level of a period other than the pilot symbol period, that is, a data symbol transmitted in a data symbol period,

Is defined as in Equation 2 below.

은

보다 크지 않은 최대 정수를 나타낸다. 상기 수학식 2에서

은 하기 수학식 3과 같이 나타낼 수 있다. In Equation 2

silver

Represents the largest integer not greater than. In Equation 2

Can be expressed as Equation 3 below.

은 섹터 ID가 s에 해당하는 길이 8인 왈쉬 코드의 반복을 나타낸다. 또한 임의의 십진수 숫자 k(

)가

의 2 진수로 표현되고, b₆가 MSB(most significant bit)이고, b₀가 LSB(least significant bit)일 경우,

는 행 벡터(row vector)를 나타내며,

이다. 또한, 상기 수학식 3에서

은 블록 코드 생성 행렬

의 제u 열 벡터(column vector)를 나타낸다. 여기서, 상기 블록 코드 생성 행렬 G는 하기 수학식 4에 나타낸 바와 같다.In Equation 3 above

Denotes a repetition of a Walsh code of length 8 whose sector ID corresponds to s. Also, the random decimal number k (

)end

If b ₆ is the most significant bit (MSB) and b ₀ is the least significant bit (LSB),

Represents a row vector,

to be. In addition, in Equation 3

Is a block code generation matrix

Denotes the u-th column vector of. Here, the block code generation matrix G is as shown in Equation 4 below.

As shown in Equation 4, the block code generation matrix G is divided into three subblocks having a length of 16, and the positions of Walsh bases in each of the three subblocks are indicated by dotted lines. Walsh basis and mask sequences used in Equation 4 are shown in Table 2 below.                     

는

행벡터와

열벡터(column vector)의 행렬곱(matrix product)을 나타내며, 상기 행렬곱은 스칼라(scalar) 값으로 나타나는데, 이때 사용되는 연산은 modulo 2 덧셈과 곱셈이다. 상기 수학식 4에서

은 상기 도 2에서 설명한 인터리버(203)의 인터리빙 방식을 나타낸다. 상기 인터리빙 방식은 하기 표 3에 나타낸 바와 같다.Meanwhile, in Equation 4

Is

With row vector

It represents the matrix product of a column vector, which is represented by a scalar value, where the operation used is modulo 2 addition and multiplication. In Equation 4

Denotes an interleaving method of the interleaver 203 described with reference to FIG. 2. The interleaving scheme is as shown in Table 3 below.

은 상기 길이 48인 블록 코드를 구성하는 48개의 엘리먼트(element)들 각각을 상기 표 3에 나타낸 바와 같은 순서대로 그 위치를 변경(permutation)하는 것이다. 상기 표 3에서 각 숫자들은 상기 블록 코드의 엘리먼트들 각각이 일대일 매핑되는 서브 캐리어들의 인덱스들을 나타낸다.That is, the interleaving method

Is a permutation of each of the 48 elements constituting the block code of length 48 in the order shown in Table 3 above. Each number in Table 3 represents indices of subcarriers to which each of the elements of the block code is mapped one-to-one.

Looking at the interleaving scheme shown in Table 3, it can be seen that the interleaving scheme of length 16 is concatenated three times as shown in Table 4 below.                     

Each number in Table 4 represents indices of subcarriers to which elements of each of the three sub codes are mapped one to one.

의 값은 상기 파일럿 심벌의 PAPR을 최소로하는 PAPR 저감 시퀀스로 결정되는 것이다. 상기 셀 ID와 섹터 ID에 대응하는 PAPR 저감 시퀀스와, 상기 셀 ID와 섹터 ID 및 PAPR 저감 시퀀스에 상응하는 파일럿 심벌의 PAPR은 하기 표 5에 나타낸 바와 같다.In addition, the sequence in Equation 2

Is determined by a PAPR reduction sequence that minimizes the PAPR of the pilot symbol. PAPR reduction sequences corresponding to the cell ID and sector ID, and PAPR of the pilot symbols corresponding to the cell ID, sector ID and PAPR reduction sequence are shown in Table 5 below.

On the other hand, the present invention as described above can be used in the generation of a pilot symbol of an OFDM communication system using a plurality of antennas, and does not require sector division. That is, the pilot symbols transmitted through each respective antenna, for example, N _t transmit antennas in an OFDM communication system for example, a transmitter, one of the OFDM communication system using N _t transmit antennas can be expressed by Equation (5) have.

은 하기 수학식 6과 같이 정의된다. In Equation 5, n represents the number of transmit antennas, k represents a subcarrier index,

Is defined as in Equation 6 below.

역시 상기 송신안테나의 개수 N_t와 상기 OFDM 통신 시스템에서 사용하는 FFT의 크기 N_FFT에 따라 다르게 정의된다. In Equation 6, two sequences R (r) and T (k) are defined differently according to the number N _t of transmission antennas and the size N _FFT of the FFT operation used in the OFDM communication system.

It is also defined differently according to the number N _t of transmission antennas and the size N _FFT of the _FFT used in the OFDM communication system.

에 대해서 살펴보면 다음과 같다. Here, a sequence R (r) and T (k) according to the number N _t of transmit antennas and the size N _FFT of an _FFT used in the OFDM communication system and

Looking at the following.

First, when the number of transmit antennas is two (N _t = 2) and the size of the FFT used in the OFDM communication system is 128 (N _FFT = 128), the R (r) is expressed by Equation 7 below. As shown.

In Equation 7, the block code generation matrix G is equal to Equation 4, and the interleaving scheme is shown in Table 6 below.

은 하기 표 8에 16진수로 나타낸 바와 같다.Meanwhile, T (k) of Equation 6 is as shown in Table 7 below.

Is as shown in Table 8 in hexadecimal.

Next, when the number of transmit antennas is three (N _t = 3) and the size of the FFT used in the OFDM communication system is 128 (N _FFT = 128), the R (r) is expressed by Equation 8 below. As shown in.

In Equation 8, the block code generation matrix G is shown in Equation 9 below, and the interleaving scheme is shown in Table 9 below.

은 하기 표 11에 16진수로 나타낸 바와 같다. Meanwhile, T (k) of Equation 6 is as shown in Table 10 below.

Is as shown in Table 11 in hexadecimal.

Next, when the number of transmit antennas is 4 (N _t = 4) and the size of the FFT used in the OFDM communication system is 512 (N _FFT = 512), the R (r) is represented by Equation 10 below. As shown in.

In Equation 10, the block code generation matrix G is shown in Equation 11 below, and the interleaving scheme is shown in Table 12 below.

은 하기 표 14a 내지 표 14b에 16진수로 나타낸 바와 같다. Meanwhile, T (k) of Equation 6 is as shown in Table 13 below.

Is as shown in hexadecimal in Table 14a to Table 14b.

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 defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention provides a pilot symbol for distinguishing a cell ID and a sector ID by using a block code and a Walsh code using a Walsh basis and a mask in an OFDM communication system, thereby distinguishing a cell ID in the OFDM communication system. And the number of sector IDs can be increased. In addition, it is possible to detect the pilot symbol by using the IFHT on the receiver side has the advantage of minimizing the complexity of the receiver. In addition, by generating a pilot symbol using the block code and the Walsh code as well as the PAPR reduction sequence, the PAPR characteristic of the pilot symbol is improved.

Claims (82)

In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells is divided by a sector identifier, a method for transmitting a reference signal for distinguishing each of the cells and sectors, When a cell identifier and a sector identifier are input, a block code is generated corresponding to the cell identifier using a preset block code generation matrix, a Walsh code is generated corresponding to the sector identifier, and then the block code and the Walsh are generated. Generating a first part sequence using code, Selecting a second part sequence according to the cell identifier and the sector identifier among preset sequences; Generating the reference signal in the frequency domain using the first part sequence and the second part sequence; And in the preset reference signal transmission interval, converting the reference signal in the frequency domain into an inverse fast Fourier transform, converting the reference signal into a reference signal in the time domain, and transmitting the same. The method of claim 1, Generating the first part sequence may include; Generating a block code corresponding to the cell identifier using the block code generation matrix; Selecting a Walsh code corresponding to the sector identifier among the preset Walsh codes and repeating the predetermined number of times; And interleaving the block code using a predetermined interleaving scheme, and generating the first part sequence by performing exclusive OR of the interleaved block code and the repeated Walsh code. An apparatus for transmitting a reference signal for distinguishing each of the cells and sectors in a communication system having a plurality of cells separated by a cell identifier, each cell having a plurality of sectors separated by a sector identifier, When a cell identifier and a sector identifier are input, a block code is generated corresponding to the cell identifier using a preset block code generation matrix, a Walsh code is generated corresponding to the sector identifier, and then the block code and the Walsh code are generated. Generates a first part sequence using the first part sequence and the reference signal in the frequency domain using the second part sequence selected corresponding to the cell identifier and the sector identifier among preset sequences With a reference signal generator, And a transmitter configured to transmit a reference signal in the frequency domain by performing inverse fast Fourier transform on the reference signal in a preset reference signal transmission period and converting the reference signal into a reference signal in the time domain. The method of claim 3, The reference signal generator; A block code encoder for generating a block code corresponding to the cell identifier using the block code generation matrix; A Walsh code repeater that selects a Walsh code corresponding to the sector identifier among the preset Walsh codes and repeats the preset number of times; An interleaver for interleaving the block code in a predetermined interleaving manner; An adder for generating the first part sequence by performing an exclusive OR on the interleaved block code and the repeated Walsh code; And a combiner for generating a reference signal in the frequency domain using the first part sequence and the second part sequence. In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells having a plurality of sectors separated by a sector identifier, wherein the entire frequency band is divided into a subcarrier bands, the cells and sectors In the method of transmitting a reference signal for distinguishing each, When a cell identifier is input, generating a block code corresponding to the cell identifier using a preset block code generation matrix; When a sector identifier is input, selecting a Walsh code corresponding to the sector identifier among preset Walsh codes and repeating the predetermined number of times; Interleaving the block code in a predetermined interleaving manner, and generating a first part sequence by performing exclusive OR on the interleaved block code and the repeated Walsh code; Selecting a second part sequence corresponding to the cell identifier and the sector identifier among preset sequences; Generating the reference signal in a frequency domain using the first part sequence and the second part sequence; And in the preset reference signal transmission interval, converting the reference signal in the frequency domain into an inverse fast Fourier transform, converting the reference signal into a reference signal in the time domain, and transmitting the same. The method of claim 5, The block code generation matrix is composed of b preset subblocks, and each of the b subblocks includes c preset Walsh basis and d preset mask sequences. The method of claim 6, Each of the b subblocks of the first subblock to the bth subblock has a cyclic shift relationship to each other to maximize a minimum distance of the block code generated using the block code generation matrix. Way. The method of claim 6, Interleaving the block code in the interleaving scheme; Dividing the block code into b subcodes; And interleaving by applying each of the b interleaving schemes differently set to each of the b subcodes. The method of claim 8, Inverse fast Fourier transform the reference signal in the frequency domain; Null data is inserted into subcarriers corresponding to a DC component of the N subcarriers and an interference cancellation component between the subcarriers, and M pieces of N subcarriers other than the subcarriers into which the null data is inserted are inserted. And inserting each of the elements constituting the reference signal into each of the subcarriers and then performing inverse fast Fourier transform. The method of claim 8, Inverse fast Fourier transform the reference signal in the frequency domain; Insert null data into subcarriers corresponding to a DC component among the N subcarriers and an interference cancellation component between the subcarriers, and insert null data among the N subcarriers in consideration of a preset offset. And inserting each of the elements constituting the reference signal into each of the M subcarriers other than the subcarriers, and then performing inverse fast Fourier transform. The method of claim 10, The offset is set to a different value in each of the cells and sectors. The method of claim 9, The reference signal is characterized by having the form as shown in Equation 12 in the frequency domain.

In Equation 12,

Denotes the reference signal, ID _cell denotes the cell ID, s denotes the sector ID, k denotes the subcarrier index, N _used is the same value as the M,

Indicates the setting sequence. The method of claim 9, The setting sequence has the form as in Equation (13).

In Equation 13,

silver

Represents the largest integer not greater than,

Is the same as Equation 14.

In Equation 14,

Denotes a repetition of a Walsh code having a length of 8, wherein the sector ID corresponds to s,

(only,

) Represents a row vector of the generation matrix of the block code,

(

) Represents the u th column vector of the block code generation matrix. The method of claim 13, The block code generation matrix is represented by Equation 15 below.

The method of claim 14, When the N _used is 108

The method of claim 15, characterized in that determined in the same manner as in Table 15.

Each number in Table 15 represents indices of subcarriers to which each of the elements of the block code is mapped one-to-one. The method of claim 15, When b is 3, the

The method according to claim 16, wherein the interleaving schemes of the first to third interleaving schemes of Table 16 are determined.

Each number in Table 16 represents indices of subcarriers to which each of the elements of each of the three sub codes is mapped one-to-one. The method of claim 15, The setting sequences are sequences determined to have a minimum peak-to-average power ratio of the peak-to-average power ratio of the reference signal. The method of claim 16, If the N _used is 108, the setting sequences are sequences as shown in Table 17 below.

In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells having a plurality of sectors separated by a sector identifier, wherein the entire frequency band is divided into a subcarrier bands, the cells and sectors In the apparatus for transmitting a reference signal for distinguishing each, A block code encoder for generating a block code corresponding to the cell identifier by using a preset block code generation matrix when a cell identifier is input; A Walsh code repeater configured to select a Walsh code corresponding to the sector identifier among the pre-set Walsh codes and to repeat a preset number of times; An interleaver for interleaving the block code in a predetermined interleaving manner; An adder for exclusively ORing the interleaved block code and the repeated Walsh code to generate a first part sequence; A combiner for generating the reference signal in the frequency domain by using the first part sequence and a second part sequence selected corresponding to the cell identifier and the sector identifier among preset sequences; And a transmitter configured to transmit a reference signal in the frequency domain by performing inverse fast Fourier transformation on the reference signal in a preset reference signal transmission period and converting the reference signal into a reference signal in the time domain. The method of claim 19, Wherein the block code generation matrix is composed of b preset subblocks, each of the b subblocks consisting of c preset Walsh basis and d preset mask sequences. The method of claim 20, Each of the b subblocks of the first subblock to the bth subblock has a cyclic shift relationship to each other to maximize a minimum distance of the block code generated using the block code generation matrix. Device. The method of claim 20, The interleaver divides the block code into b subcodes, and interleaves by applying each of the b interleaving schemes that are differently set for each of the b subcodes. The method of claim 19, The transmitter; Null data is inserted into subcarriers corresponding to a DC component of the N subcarriers and an interference cancellation component between the subcarriers, and M pieces of N subcarriers other than the subcarriers into which the null data is inserted are inserted. An inverse fast Fourier transformer inserting each of the elements constituting the reference signal into each of the subcarriers and then performing an inverse fast Fourier transform; And a radio frequency processor for radio frequency processing and transmitting the inverse fast Fourier transformed signal. The method of claim 19, The transmitter; Insert null data into subcarriers corresponding to a DC component among the N subcarriers and an interference cancellation component between the subcarriers, and insert null data among the N subcarriers in consideration of a preset offset. An inverse fast Fourier transformer inserting each of the elements constituting the reference signal into each of the M subcarriers other than the subcarriers, and inverse fast Fourier transform; And a radio frequency processor for radio frequency processing and transmitting the inverse fast Fourier transformed signal. The method of claim 24, And the offset is set to a different value for each of the cells and sectors. The method of claim 23, The reference signal is characterized in that the device having the form as shown in Equation 16 in the frequency domain.

In Equation 16,

Denotes the reference signal, ID _cell denotes the cell ID, s denotes the sector ID, k denotes the subcarrier index, N _used is the same value as the M,

Indicates the setting sequence. The method of claim 23, The setting sequence has the form as in Equation 17.

In Equation 17,

silver

Represents the largest integer not greater than,

Is the same as Equation 18 below.

In Equation 18,

Denotes a repetition of a Walsh code having a length of 8, wherein the sector ID corresponds to s,

(only,

) Represents a row vector of the generation matrix of the block code,

(

) Represents the u th column vector of the block code generation matrix. The method of claim 27, The block code generation matrix is represented by Equation 19 below.

The method of claim 28, When the N _used is 108

The device according to claim 18, characterized in that determined in the same manner as in Table 18.

Each number in Table 18 represents indices of subcarriers to which each of the elements of the block code is mapped one-to-one. The method of claim 29, When b is 3, the

The apparatus according to claim 19, wherein the first to third interleaving schemes are determined as three interleaving schemes.

Each number in Table 19 represents indices of subcarriers to which each of the elements of each of the three sub codes is mapped one-to-one. The method of claim 29, The setting sequences are sequences determined to have a minimum peak-to-average power ratio of the peak-to-average power ratio of the reference signal. The method of claim 30, If the N _used is 108, the setting sequence is characterized in that the sequence shown in Table 20 below.

In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells having a plurality of sectors separated by a sector identifier, wherein the entire frequency band is divided into a subcarrier bands, the cells and sectors In the method for receiving a reference signal for distinguishing each, Extracting the reference signal from a fast Fourier transformed received signal; Repeating a predetermined number of times a Walsh code corresponding to an arbitrary sector identifier among preset Walsh codes; Dividing the reference signal by a preset interval and performing exclusive OR on the repeated Walsh code; Deinterleaving the exclusive OR signal corresponding to a predetermined deinterleaving scheme; Dividing the deinterleaved signal into sub-block signals corresponding to a predetermined block code generation matrix; Performing inverse fast Hadamard transform using each of the mask sequences generated according to a predetermined control on each of the sub-block signals; Combining the inverse fast Hadamard transformed signals with respect to each of the sub-block signals to generate combined signals; Detecting a cell identifier corresponding to a block code having a maximum correlation value among the combined signals as a final cell identifier and a sector identifier corresponding to the Walsh code having the maximum correlation value as a final sector identifier. Said method. The method of claim 33, wherein Wherein the block code generation matrix is composed of b preset subblocks, and each of the b subblocks consists of c preset Walsh basis and d preset mask sequences. The method of claim 34, wherein Each of the b subblocks of the first subblock to the bth subblock has a cyclic shift relationship to each other to maximize a minimum distance of the block code generated using the block code generation matrix. Way. The method of claim 33, wherein Extracting the reference signal; Extracting a signal from a signal received through M subcarriers other than the subcarriers corresponding to the DC component among the N subcarriers and the interference cancellation component between the subcarriers, as the reference signal; Said method. The method of claim 33, wherein Extracting the reference signal; The reference is determined by removing a predetermined sequence after considering a preset offset in a signal received through the DC component among the N subcarriers and the M subcarriers corresponding to the interference cancellation component between the subcarriers. The method as characterized in that the extraction as a signal. The method of claim 37, The offset is set to a different value in each of the cells and sectors. The method of claim 33, wherein The setting sequences are sequences determined to have a minimum peak-to-average power ratio of the peak-to-average power ratio of the reference signal. The method of claim 37, The reference signal is characterized by having the form as shown in Equation 20 in the frequency domain.

In Equation 20,

Represents the reference signal, ID _cell represents the cell ID, s represents the sector ID, k represents the offset, N _used is the same value as the M,

Indicates the setting sequence. The method of claim 39, The setting sequence has a form as in Equation 21 below.

In Equation 21,

silver

Represents the largest integer not greater than,

Is the same as Equation 22.

In Equation 22,

Denotes a repetition of a Walsh code having a length of 8, wherein the sector ID corresponds to s,

(only,

) Represents a row vector of the generation matrix of the block code,

(

) Represents the u th column vector of the block code generation matrix. The method of claim 39, The block code generation matrix is represented by Equation 23.

The method of claim 42, wherein When the N _used is 108

The method according to claim 21, characterized in that determined in the manner as shown in Table 21.

Each number in Table 21 represents indices of subcarriers to which each of the elements of the block code is mapped one-to-one. The method of claim 43, When b is 3, the

The method according to claim 22, wherein the interleaving schemes of the first to third interleaving schemes of Table 22 are determined.

Each number in Table 22 represents indices of subcarriers to which each of the elements of each of the three subcodes is mapped one-to-one. The method of claim 41, wherein If the N _used is 108, the setting sequences are sequences as shown in Table 23 below.

In a communication system having a plurality of cells separated by a cell identifier, each of the plurality of cells having a plurality of sectors separated by a sector identifier, wherein the entire frequency band is divided into a subcarrier bands, the cells and sectors In the apparatus for receiving a reference signal for distinguishing each, A fast Fourier transformer for converting a received signal to a fast Fourier transform, A reference signal extractor for extracting the reference signal from the fast Fourier transformed signal; A Walsh code repeater that repeats a Walsh code corresponding to an arbitrary sector identifier among preset Walsh codes, a preset number of times; An adder for dividing the reference signal by a predetermined set interval unit and performing an exclusive OR on the repeated Walsh code; A deinterleaver for deinterleaving the exclusive OR signal corresponding to a preset deinterleaving scheme; A sub-block divider for dividing the deinterleaved signal into sub-block signals corresponding to a predetermined block code generation matrix; A block code decoder for performing inverse fast Hadamard transform using each of the mask sequences generated according to a predetermined control for each of the sub-block signals; A combiner for combining the inverse fast Hadamard transformed signals with respect to each of the sub-block signals to generate combined signals; And a comparison selector for detecting a cell identifier corresponding to a block code having a maximum correlation value among the combined signals as a final cell identifier and a sector identifier corresponding to the Walsh code having the maximum correlation value as a final sector identifier. The apparatus described above. 47. The method of claim 46 wherein Wherein the block code generation matrix is composed of b preset subblocks, each of the b subblocks consisting of c preset Walsh basis and d preset mask sequences. The method of claim 47, Each of the b subblocks of the first subblock to the bth subblock has a cyclic shift relationship to each other to maximize a minimum distance of the block code generated using the block code generation matrix. Device. 47. The method of claim 46 wherein The reference signal extractor extracts a signal from which a preset sequence is removed from a signal received through M subcarriers other than subcarriers corresponding to a DC component among the N subcarriers and an interference cancellation component between the subcarriers. The apparatus, characterized in that for extracting. 47. The method of claim 46 wherein The reference signal extractor considers a preset offset in a signal received through a subcarrier corresponding to a DC component among the N subcarriers and an interference cancellation component between the subcarriers, and then sets a preset sequence. And extracting the reference signal to remove the reference signal. 51. The method of claim 50, And the offset is set to a different value for each of the cells and sectors. 47. The method of claim 46 wherein The setting sequences are sequences determined to have a minimum peak-to-average power ratio of the peak-to-average power ratio of the reference signal. 51. The method of claim 50, The reference signal is characterized in that the device having the form as shown in Equation 24 in the frequency domain.

In Equation 24,

Represents the reference signal, ID _cell represents the cell ID, s represents the sector ID, k represents the offset, N _used is the same value as the M,

Indicates the setting sequence. The method of claim 52, wherein The setting sequence has the form as in Equation (25).

In Equation 25,

silver

Represents the largest integer not greater than,

Is the same as Equation 26.

In Equation 26,

Denotes a repetition of a Walsh code having a length of 8, wherein the sector ID corresponds to s,

(only,

) Represents a row vector of the generation matrix of the block code,

(

) Represents the u-th column vector of the block code generation matrix. The method of claim 52, wherein The block code generation matrix is represented by Equation 27 below.

The method of claim 55, When the N _used is 108

The device according to claim 24, wherein it is determined in the same manner as in Table 24 below.

Each number in Table 24 represents indices of subcarriers to which each of the elements of the block code is mapped one-to-one. The method of claim 56, wherein When b is 3, the

The apparatus as claimed in claim 25 is determined by three interleaving schemes of the first to third interleaving schemes.

Each number in Table 25 represents indices of subcarriers to which each of the elements of each of the three subcodes is mapped one-to-one. The method of claim 54, And when the N _used is 108, the configuration sequences are sequences as shown in Table 26 below.

In a communication system having a plurality of cells separated by a cell identifier, the entire frequency band is divided into a sub-carrier band, a method for transmitting a reference signal for distinguishing each of the cells through one or more transmission antennas , When a cell identifier is input, a block code is generated corresponding to the cell identifier using a preset block code generation matrix, and a preset Walsh code corresponding to the cell identifier is selected among preset Walsh codes. Repeat as many times as possible, Interleaving the block code in a predetermined interleaving manner, and generating a first part sequence by performing exclusive OR on the interleaved block code and the repeated Walsh code; Selecting a second part sequence corresponding to the cell identifier among preset sequences; Generating the reference signal in a frequency domain using the first part sequence and the second part sequence; And in the preset reference signal transmission interval, converting the reference signal in the frequency domain into an inverse fast Fourier transform, converting the reference signal into a reference signal in the time domain, and transmitting the same. The method of claim 59, Wherein the block code generation matrix is composed of b preset subblocks, and each of the b subblocks consists of c preset Walsh basis and d preset mask sequences. The method of claim 60, Each of the b subblocks of the first subblock to the bth subblock has a cyclic shift relationship to each other to maximize a minimum distance of the block code generated using the block code generation matrix. Way. The method of claim 60, Interleaving the block code in the interleaving scheme; Dividing the block code into b subcodes; And interleaving by applying each of the b interleaving schemes differently set to each of the b subcodes. The method of claim 62, Inverse fast Fourier transform the reference signal in the frequency domain; Null data is inserted into subcarriers corresponding to a DC component of the N subcarriers and an interference cancellation component between the subcarriers, and M pieces of N subcarriers other than the subcarriers into which the null data is inserted are inserted. And inserting each of the elements constituting the reference signal into each of the subcarriers and then performing inverse fast Fourier transform. The method of claim 62, Inverse fast Fourier transform the reference signal in the frequency domain; Insert null data into subcarriers corresponding to a DC component among the N subcarriers and an interference cancellation component between the subcarriers, and insert null data among the N subcarriers in consideration of a preset offset. And inserting each of the elements constituting the reference signal into each of the M subcarriers other than the subcarriers, and then performing inverse fast Fourier transform. 65. The method of claim 64, The offset is set to a different value in each of the cells and sectors. The method of claim 63, wherein The reference signal is characterized by having the form as shown in Equation 28 in the frequency domain.

In Equation 28

Denotes the reference signal, ID _cell denotes the cell identifier, n denotes the number of transmit antennas, k denotes the subcarrier index, and

Indicates the setting sequence. The method of claim 63, wherein The setting sequence has a form as in Equation 29 below.

In Equation 30,

silver

Represents the largest integer not greater than. The method of claim 67, remind

Is characterized by having the form as in Equation 30 below.

In Equation 30, the number of transmit antennas is two, and the size of the fast Fourier transform operation is 128,

(

) Represents the u th column vector of the block code generation matrix. The method of claim 67, The block code generation matrix is represented by Equation 31 below.

The method of claim 67, remind

The method according to claim 27, characterized in that determined in the same manner as in Table 27.

Each number in Table 27 represents indices of subcarriers to which each of the elements of the block code is mapped one-to-one. The method of claim 67, The T (k) is characterized in that the method is determined in the same manner as Table 28.

The method of claim 67, remind

The method according to claim 29, characterized in that determined in the same manner as in Table 29.

The method of claim 67, remind

Is characterized by having the form as shown in Equation 32 below.

In Equation 32, the number of transmit antennas is three, and the size of the fast Fourier transform operation is 128,

(

) Represents the u th column vector of the block code generation matrix. The method of claim 67, The block code generation matrix is represented by Equation 33 below.

The method of claim 67, remind

The method of claim 30, characterized in that determined in the same manner as in Table 30.

Each number in Table 30 represents indices of subcarriers to which each of the elements of the block code is mapped one-to-one. The method of claim 67, The T (k) is characterized in that the method is determined in the same manner as Table 31.

The method of claim 67, remind

The method according to claim 32, characterized in that determined in the manner as shown in Table 32.

The method of claim 67, remind

The method according to claim 34, having the form as shown in Equation (34).

In Equation 34, the number of transmit antennas is four, and the size of the fast Fourier transform operation is 512,

(

) Represents the u th column vector of the block code generation matrix. The method of claim 67, The block code generation matrix is represented by Equation 35 below.

The method of claim 67, remind

The method according to claim 33, characterized in that determined in the same manner as in Table 33.

Each number in Table 33 represents indices of subcarriers to which each of the elements of the block code is mapped one-to-one. The method of claim 67, The T (k) is characterized in that the method is determined in the same manner as Table 34 below.

The method of claim 67, remind

The method according to claim 35, characterized in that determined in the same manner as in Table 35.

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