KR20050018333A - Apparatus for generating preamble sequence in communication system using orthogonal frequency division multiplexing scheme and method thereof - Google Patents

Abstract

PURPOSE: An apparatus for generating a preamble sequence in an OFDM(Orthogonal Frequency Division Multiplexing) communication system and a method thereof are provided to generate a short preamble sequence having a minimum peak to average power ratio. CONSTITUTION: According to the apparatus for generating a preamble sequence in an OFDM communication system, a preamble sequence generator(415) generates a preamble sequence having the third number of components when using the same number of partial channels as the second number in the OFDM communication system. And an IFFT(Inverse Fast Fourier Transform) unit(419) inserts null data to sub carriers corresponding to interference removing components between a DC component and the sub carriers among the first number of sub carriers, and inserts the third number of preamble sequence components to each sub carrier except the sub carrier where the null data is inserted, and then performs IFFT as to them.

Description

Preamble sequence generation apparatus and method in a communication system using orthogonal frequency division multiplexing {APPARATUS FOR GENERATING PREAMBLE Sequence

The present invention relates to an orthogonal frequency division multiple communication system, and more particularly, to an apparatus and method for generating a preamble sequence for partial channelization.

In general, a wireless communication system is a system supporting a wireless communication service, and is composed of a base station Node B and a user equipment (UE). The base station and the user terminal support a wireless communication service using a transmission frame. Accordingly, the base station and the user terminal should acquire mutual synchronization for transmission and reception of a transmission frame, and in order to obtain the synchronization, the base station may synchronize the signal so that the user terminal knows the start of a frame transmitted from the base station. Send it. Then, the user terminal receives the synchronization signal transmitted by the base station, checks the frame timing of the base station, and demodulates the received frame according to the checked frame timing. In addition, the synchronization signal generally uses a specific preamble sequence that is previously promised by the base station and the user terminal.

In addition, a preamble sequence used in the orthogonal frequency division multiplexing (OFDM) communication system is referred to as a peak to average power ratio (PAPR). The preamble transmitted from the base station to the user terminal is a long preamble, which is used by connecting a preamble necessary for coarse synchronization and a short preamble required for fine frequency synchronization. . In addition, the preamble transmitted from the user terminal to the base station to obtain fine frequency synchronization using only the short preamble. Here, the reason why a small PAPR is used as the preamble sequence of the OFDM communication system will be described. First, the orthogonality of each of the subcarriers is considered important because the OFDM communication system uses a plurality of carriers, that is, a plurality of subcarriers, as a multi-carrier communication system. Thus, a phase is set to have orthogonality between each of the subcarriers. When the phase is changed in a process of transmitting and receiving signals through the subcarriers, signals between the subcarriers may overlap. In this case, the size of the overlapped signal due to the phase change is out of the linear section of the amplifier provided in the OFDM communication system, and thus, the normal communication is not possible. Therefore, the OFDM communication system has a preamble having a minimum PAPR. Is to use sequences.

In addition, the OFDM communication system transmits data for multiple users, that is, user terminals by multiplexing one frame in time. In the OFDM communication system, a frame preamble indicating a start of a frame is transmitted for a predetermined period from the start of the frame. In addition, since data to be transmitted to each of the users may be irregularly transmitted in one frame, a burst preamble indicating the start of data exists in front of each data. Therefore, the user terminal must receive the data preamble to know the transmission start point of the data. That is, the user terminal needs to synchronize the starting point of the data in order to receive the data. To this end, the user terminal must acquire and synchronize the preamble sequence commonly used by all systems before receiving the signal.

On the other hand, the OFDM communication system is the same as the communication system that does not use the OFDM method, the source coding (source coding), the channel coding (channel coding), modulation (modulation) method and the like. Of course, in a code division multiple access (CDMA) communication system, data is spread and transmitted, whereas the OFDM communication system converts data into an inverse fast Fourier transform (CDMA). IFFT: Inverse Fast Fourier Transform (hereinafter referred to as " IFFT ") and then transmitting in the form of inserting a guard interval, the OFDM communication system uses a relatively simple hardware (for broadband signals) compared to the CDMA communication system. hardware). That is, the OFDM communication system inputs parallelized bit / symbol strings to an IFFT input corresponding to a frequency domain by combining a plurality of bit / symbol strings after performing modulation on data. In this case, a time domain signal IFFT is output. Here, the output time-domain signal is a multiplexed wideband signal into a narrowband subcarrier signal, and a plurality of modulation symbols are transmitted through the IFFT process during one OFDM symbol period.

However, if the OFDM symbol is transmitted as it is in the OFDM communication system, interference between the previous OFDM symbol and the current OFDM symbol cannot be avoided. The guard interval is inserted to remove the intersymbol interference. The guard interval has been proposed in the form of inserting null data of a predetermined interval, but in the form of transmitting null data in the guard interval, when the receiver incorrectly estimates the start point of the OFDM symbol, interference between subcarriers occurs and the received OFDM There is a disadvantage in that the probability of misjudging a symbol increases. Thus, the protection period is a "Cyclic Prefix" 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 the first predetermined bits of the OFDM symbol in the time domain are copied and inserted into the valid OFDM symbol. The "Cyclic Postfix" method has been proposed and used. Here, the predetermined bits of the Cyclic Prefix method and the Cyclic Postfix method are preset configuration bits and have a predetermined size in the OFDM communication system. The guard period may be used for time / frequency synchronization of a received OFDM symbol by a receiver using a characteristic of copying and repeatedly arranging a part of an OFDM symbol in a time domain, that is, the first part or the last part of an OFDM symbol. .

Meanwhile, the transmission signal transmitted by the transmitter is distorted while passing through the wireless channel, and the receiver receives the distorted transmission signal. The receiver acquires time / frequency synchronization by using a preamble sequence preset between the transmitter and the receiver by receiving a signal in which the transmission signal is distorted, and performs channel estimation, followed by a fast Fourier transform (FFT). Demodulate the symbols in the frequency domain through Fast Fourier Transform (hereinafter referred to as "FFT"). After demodulating the symbols in the frequency domain, the receiver decodes the demodulated symbols into information data by performing channel decoding and source decoding corresponding to the channel coding applied by the transmitter. .

The OFDM communication system uses a preamble sequence for both frame timing synchronization and frequency synchronization and channel estimation. Of course, in the OFDM communication system, frame timing synchronization, frequency synchronization, and channel estimation may be performed using a guard interval and a pilot subcarrier in addition to the preamble. In the case of the preamble sequence, known symbols are transmitted at the beginning of every frame or burst of data, and the estimated time / frequency / channel information is transmitted using information such as guard interval and pilot subcarrier in the data transmission portion. Used to update.

Next, the preamble sequence structure used in the conventional OFDM communication system will be described with reference to FIGS. 1 and 2.

FIG. 1 illustrates a long preamble sequence structure of a conventional OFDM communication system.

Prior to the description of FIG. 1, the current OFDM communication system uses the same preamble sequence in both downlink (DL) and uplink (UL). Referring to FIG. 1, the long preamble sequence has a form in which a 64 length sequence is repeated 4 times and a 128 length sequence is repeated twice, and the Cyclic Prefix as described above is 64 length in length due to the characteristics of an OFDM communication system. A sequence front end of the form in which the sequence is repeated four times, and a 128 length sequence is added to the front end of the sequence in the form of two repeats. In addition, as described above, the signals before performing the IFFT are frequency domain signals, and the signals after performing the IFFT are time domain signals. The long preamble sequence shown in FIG. Long preamble sequence in the time domain is shown.

Meanwhile, the long preamble sequence in the frequency domain before performing the IFFT is as follows.

The long preamble sequences in the frequency domain, that is, the numbers specified in S (-100: 100) and P (-100: 100) represent subcarrier positions applied when performing IFFT, which will be described with reference to FIG. 3 below. The detailed description thereof will be omitted here. S (-100: 100) represents a frequency domain sequence in which a 64 length sequence is repeated 4 times, and P (-100: 100) represents a frequency domain sequence in a 128 length 2 sequence sequence. . In the expressions of S (-100: 100) and P (-100: 100), sqrt (2) means root 2, and sqrt (2) * sqrt (2) means S (-100: 100) and P It means amplification in two stages to increase the transmit power of (-100: 100).

The long preamble sequence structure has been described above with reference to FIG. 1, and the short preamble sequence structure will now be described with reference to FIG. 2.

2 is a diagram illustrating a short preamble sequence structure of a conventional OFDM communication system.

Referring to FIG. 2, the short preamble sequence has a form in which a 128 length sequence is repeated twice, and as described above, the Cyclic Prefix has a form in which the 128 length sequence is repeated twice. Added to the front of the sequence. In addition, the short preamble sequence shown in FIG. 2 shows a short preamble sequence in the time domain after performing the IFFT, and the short preamble sequence in the frequency domain is P (-100: 100) described above.

On the other hand, the long preamble sequence as described above should be generated in consideration of the following matters.

(1) must have a low PAPR.

In order to maximize transmission efficiency of a power amplifier (PA) of a transmitter transmitting end of an OFDM communication system, the PAPR of an OFDM symbol must be low. As described above, the IFFT-signaled signal is input to the power amplifier, and low PAPR is required because of the non-linear characteristic of the power amplifier. The PAPR of the OFDM symbol should have a small ratio of the maximum power and the average power of the time-domain symbol of the OFDM corresponding to the IFFT output terminal of the transmitting end, and have a uniform distribution in order that the ratio of the maximum power and the average power is small. In other words, when a combination of symbols having low cross-correlation in the IFFT input terminal, that is, the frequency domain of the transmitting end, the PAPR of the output becomes small.

(2) It must be suitable for parameter estimation necessary for communication initialization.

The parameter estimation includes channel estimation, frequency offset estimation, and time offset estimation.

(3) It must have low complexity and low overhead.

(4) The approximate frequency offset estimation should be possible.

The function of the long preamble sequences generated in consideration of the above matters is as follows.

(1) A sequence having a length of 64 repeated four times is used for time offset estimation and coarse frequency offset estimation.

(2) A sequence of 128 repeats of length twice is used for fine frequency offset and channel estimation.

As a result, the long preamble sequence is used for the following purposes in the OFDM communication system.

(1) Used as the first preamble sequence of a downlink protocol data unit (hereinafter referred to as a "PDU").

(2) Used for Initial Ranging.

(3) Used for Bandwidth Request Ranging.

The short preamble sequence is used for the following purposes in the OFDM communication system.

(1) Used as an uplink data preamble sequence.

(2) Used for Periodic Ranging.

On the other hand, since the correct synchronization can be obtained by performing the initial ranging and the periodic ranging in the OFDM communication system, the uplink data preamble sequence is mainly used for the purpose of channel estimation. Considerations in the channel estimation are PAPR, performance, and complexity. For the short preamble sequence used, the PAPR is 3.5805 [dB]. The channel estimation algorithm may use various types of channel estimation algorithms such as MMSE (Minimum Mean Square Error, hereinafter referred to as "MMSE") and LS (Least Square, hereinafter referred to as "LS").

In addition, the OFDM communication system uses a sub-channelization method to increase frequency efficiency. Here, the partial channelization is a method in which the entire subcarriers are divided into several partial channels for efficient use of frequency, and each partial channel includes a specific number of subcarriers smaller than the total number of subcarriers. For example, if the total number of subcarriers of the OFDM communication system is 256 (-128, ...., 127), the number of subcarriers actually used is 200 (-100, ...., 100) and four It is divided into partial channels. In this case, a method of allocating a partial channel is as follows.

(1) Total subcarriers used (200): -100, -99, ....,-1,1, ....., 99,100

(2) Protection Zone: Left (28): -128, ..,-101, Right (27): 101, .., 127

(3) partial channel assignment

① Subchannel 1: {-100, ..,-89}, {-50, ...,-39}, {1, ... 13}, {51, ..., 63}

② partial channel 2: {-88,... , -76}, {-38, ...,-26}, {14, ..., 25}, {64, ..., 75}

③ subchannel 3: {-75,... , -64}, {-25, ...,-14}, {26, ..., 38}, {76, ..., 88}

④ partial channel 4: {-63,... , -51}, {-13, ...,-1}, {39, ..., 50}, {89, ..., 100}

Next, a mapping relationship between subcarriers and a preamble sequence during IFFT in a conventional OFDM communication system will be described with reference to FIG. 3.

3 is a diagram schematically illustrating a mapping relationship between subcarriers and a preamble sequence when performing IFFT in a conventional OFDM communication system.

3 is 256 when the total number of subcarriers of the OFDM communication system, that is, there are 256 subcarriers from -128 subcarriers to 127, and the actual number of subcarriers used is 200, that is, -100 times, It is assumed that 200 subcarriers of ..., -1, 1 ..., 100 are used. In FIG. 3, the input numbers in front of the IFFT indicate frequency components, that is, subcarrier numbers. Here, only 200 subcarriers of the 256 subcarriers, that is, only 200 subcarriers except for subcarriers 0 to 128, -128 subcarriers to -101 subcarriers, and 101 subcarriers to 127 subcarriers, among the 256 subcarriers use. Null data, that is, zero data (0 data) is inserted and transmitted in each of the subcarriers 0, -128 subcarriers to -101 subcarriers, and 101 subcarriers to 127 subcarriers. Is as follows. First, the null data is inserted into subcarrier 0 because the subcarrier 0 represents a reference point of a preamble sequence in the time domain, that is, a DC component in the time domain after performing the IFFT. The reason why null data is inserted into the 28 subcarriers from the -128 subcarrier to the -101 subcarrier and 27 subcarriers from the 101 subcarrier to the 127 subcarrier is because of the -128 subcarrier to the -101 subcarrier Since 28 subcarriers up to and 27 subcarriers from subcarriers 101 to 127 subcarriers correspond to a high frequency band in the frequency domain, a guard interval is provided in the frequency domain.

As a result, when the preamble sequence S (-100: 100) or P (-100: 100) or P1subch (-100: 100) or P2subch (-100: 100) in the frequency domain is input to the IFFT, the IFFT is inputted. The preamble sequence S (-100: 100) or P (-100: 100) or P1subch (-100: 100) or P2subch (-100: 100) in the frequency domain is mapped to the corresponding subcarriers and thus inverse fast Fourier transform Output in the preamble sequence of the area. Here, the P1subch (-100: 100) is a preamble sequence of a frequency domain when one partial channel is used in the partial channelization process, and the P2subch (-100: 100) is a partial channel in the partial channelization process. This is a preamble sequence in the frequency domain when these two are used.

Next, a transmitter structure of the OFDM communication system will be described with reference to FIG. 4.

4 is a diagram schematically illustrating a transmitter structure of an OFDM communication system.

Referring to FIG. 4, first, when information bits to be transmitted are generated, the information bits are input to a symbol mapper 411. The symbol mapper 411 modulates the input information bits using a predetermined modulation scheme, converts the symbols, and outputs the converted symbols to a serial to parallel converter 413. Here, the modulation scheme may be a quadrature phase shift keying (QPSK) scheme or a quadrature amplitude modulation (16QAM) scheme. The serial / parallel converter 413 inputs a symbol output from the symbol mapper 411 to be an input number of an inverse fast fourier transformer (hereinafter, referred to as an “IFFT unit”) 419. After the parallel conversion to match the A-point (A-point) and output to the selector (417). The preamble sequence generator 415 generates a corresponding preamble sequence under the control of a controller (not shown) and outputs the corresponding preamble sequence to the selector 417. The selector 417 selects one of the signal output from the serial / parallel converter 413 or the signal output from the preamble sequence generator 415 according to scheduling of the corresponding time point to the IFFT unit 419. Output

The IFFT unit 419 inputs the signal output from the selector 417, performs an A-point IFFT, and outputs the result to a parallel to serial converter 421. In addition, the parallel / serial converter 421 receives a Cyclic Prefix as well as a signal output from the IFFT unit 419. Then, the parallel / serial converter 421 serially converts the signal output from the IFFT device 419 and the Cyclic Prefix and outputs the digital-to-analog converter 423. The digital-to-analog converter 423 inputs a signal output from the parallel / serial converter 421 to perform analog conversion, and then a radio frequency (RF) processor. 425). In this case, the RF processor 425 includes a filter, a front end unit, and the like, and RF-processes the signal output from the digital-to-analog converter 423 to be transmitted on actual air. After transmission through the antenna (antenna).

Meanwhile, the case where the partial channel is used may be classified into three cases. The three cases are as follows.

(1) Case 1: Only one partial channel out of four partial channels is used. In this case, null data is transmitted through the remaining three partial channels except the one partial channel.

(2) Case 2: Only two partial channels of four partial channels are used (partial channel 1 + part channel 3 or part channel 2 + part channel 4). In this case, null data is transmitted through the remaining partial channels except for the two partial channels.

(3) Case 3: All four partial channels are used (general OFDM communication system).

In the case of the existing short preamble sequence used in the partial channelization process, the PAPR of each of the partial channels is shown in Table 1 below. In this case, Cyclic Prefix is not considered in the process of calculating the PAPR of the partial channels.

As shown in Table 1, the PAPRs of the partial channels show 7.4339 [dB] in the worst case, and the PAPR of the short preamble sequence is 3.5 [dB] even when all four partial channels are used. ] Has a problem with more than. As described above, the preamble sequence improves the OFDM communication system performance as the PAPR is smaller. In general, for data transmission, a value of 3.5805 [dB] may be regarded as a relatively low value that does not affect the performance of an OFDM communication system. However, in consideration of the preamble sequence used for estimating the initial parameter in the OFDM communication system, a value of 3.5805 [dB] may be a value that may cause performance degradation of the OFDM communication system. That is, the preamble sequence should be designed to have a PAPR of at least 3 [dB] or less for initial parameter estimation of the OFDM communication system. However, in the case of the short preamble sequence used in the conventional OFDM communication system, the PAPR is 3.5805 [dB] and has a value of 3 [dB] or more, which may result in degradation of the OFDM communication system performance. Therefore, the need for a new type of short preamble sequence is emerging because it does not satisfy the low PAPR, which should be considered as the highest priority as a preamble sequence.

Accordingly, an object of the present invention is to provide an apparatus and method for generating a preamble sequence during partial channelization of an orthogonal frequency division multiplexing system.

Another object of the present invention is to provide an apparatus and method for generating a short preamble sequence having a minimum peak-to-average power ratio in an orthogonal frequency division multiple communication system.

The apparatus of the present invention for achieving the above objects; An apparatus for generating a preamble sequence in an orthogonal frequency division multiplexing system having a first number of subcarriers and a second number of subchannels generated by classifying the first number of subcarriers into a predetermined number, the orthogonal frequency A preamble sequence generator for generating a preamble sequence having a third number of components when using the same number of subchannels as the second number in a divided multiple communication system; and removing interference between DC components and subcarriers among the first number of subcarriers Inserting null data into subcarriers corresponding to a component, and each of the third number of preamble sequence components into each of the third subcarriers other than the subcarriers into which the null data is inserted among the first subcarriers. Contains an inverse fast Fourier transform that inserts a and inverse fast Fourier transform It is characterized by.

The method of the present invention for achieving the above objects; A method for generating a preamble sequence in an orthogonal frequency division multiple communication system having a first number of subcarriers and a second number of subchannels generated by classifying the first number of subcarriers into a predetermined number, the orthogonal frequency When using the same number of partial channels as the second number in a divided multiple communication system, generating a preamble sequence having a third number of components, and a DC component among the first number of subcarriers and an interference cancellation component between subcarriers. Insert null data into corresponding subcarriers, and insert each of the third number of preamble sequence components into each of the third number of subcarriers other than the subcarriers into which the null data is inserted among the first number of subcarriers. And then inverse fast Fourier transform.

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.

In the present invention, the total number of sub-carriers (A sub-carriers) is A, and the actual number of sub-carriers used are -B, -B + 1, ..., -1, 1, ..., B- Orthogonal Frequency Division Multiplexing (OFDM), which is referred to as Nos. 1 and B, is referred to as Minimum Peak to Average Power Ratio (PAPR) in a communication system. An apparatus and method for generating a preamble sequence having a preamble sequence are provided. In the OFDM communication system, although the actual number of subcarriers is A, as described in the related art, subcarrier No. 0 representing a DC component in the time domain and a high frequency band in the frequency domain, that is, the time domain Null data on the subcarriers (the subcarriers of the -A subcarrier to the -B-1 subcarrier and the subcarriers of the B + 1 subcarrier to the A-1 subcarrier) indicating a guard interval in That is, since 0 data is inserted, the number of subcarriers into which the actual preamble sequence is inserted is 2B.

As described in the prior art, the preamble sequence has two types, a long preamble sequence and a short preamble sequence, and the long preamble sequence has a length A / 4 sequence of 4. Times, the length A / 2 sequence is repeated twice, and due to the characteristics of an OFDM communication system, the Cyclic Prefix is a sequence preceding the form in which the length A / 4 sequence is repeated four times, and the length A / 2 sequence Is added to the front of the sequence in the form of two repetitions. Here, A denotes a point of the inverse fast Fourier transform (IFFT), ie, the input number A, to be described below. For example, when the IFFT is 256-point, the long preamble sequence has a form in which a sequence of length 256/4, that is, length 64, is repeated four times, and a length of 256/2, that is, length 128, is repeated twice. In addition, the short preamble sequence has a form in which a length A / 2 sequence is repeated twice, and in the characteristics of an OFDM communication system, the Cyclic Prefix as described above is repeated in a sequence in which the sequence of length A / 2 is repeated twice. Is added.

In addition, the OFDM communication system uses a sub-channelization method to increase frequency efficiency. For example, if the total number of sub-carriers (sub-carriers) of the OFDM communication system is 256 (-128, ..., 127), the number of subcarriers actually used is 200 (-100, .... , 100) and is divided into four subchannels. In this case, a method of allocating a partial channel is as follows.

(1) Total subcarriers used (200): -100, -99, ....,-1,1, ....., 99,100

(2) Guard interval: left (28): -128, ..,-101, right (27): 101, .., 127

(3) partial channel assignment

① Subchannel 1: -100, ..,-89, -50, ...,-39,1, ... 13,51, ..., 63

② subchannel 2: -88,... , -76, -38, ...,-26,14, ..., 25,64, ..., 75

③ partial channel 3: -75,... , -64, -25, ...,-14,26, ..., 38,76, ..., 88

④ partial channel 4: -63,... , -51, -13, ...,-1,39, ..., 50,89, ..., 100

In the following description, the preamble sequence mapping rule when the partial channelization method is used in the OFDM communication system according to the present invention will be described.

The present invention proposes the following preamble sequence mapping rule when all four partial channels are used in the partial channelization process of the OFDM communication system. In this case, the use of all four partial channels is the same as the case of not applying the partial channel, and thus, the preamble sequence mapping rule proposed in the present invention can be applied to an OFDM communication system that does not use the partial channel. Of course.

<Preamble Sequence Mapping Rule>

The preamble sequence shown in the <first preamble sequence mapping rule>, that is, a short preamble sequence PD (-100: 100) is a sequence allocated when all four partial channels of the partial channel allocation scheme are used. . Here, the PD (-100: 100) is a frequency domain sequence in which a 128-length sequence is repeated twice. In the expression of the PD (-100: 100), sqrt (2) means root 2, and sqrt (2) * sqrt (2) means amplifying in two steps to increase the transmit power of the PD (-100: 100). In the OFDM communication system, signals before performing an Inverse Fast Fourier Transform (IFFT) are called frequency domain signals, and signals after performing an IFFT are time domain. (time domain) signals.

Next, a mapping relationship between subcarriers and a preamble sequence when performing an IFFT in an OFDM communication system according to an embodiment of the present invention will be described with reference to FIG. 5.

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

5 is 256 when the total number of subcarriers in an OFDM communication system is 256, that is, there are 256 subcarriers up to -128, ..., 127, and the number of subcarriers actually used is 200, that is, -100 It is assumed that 200 subcarriers up to ... -1.1, .... 100 are used. In FIG. 5, the input numbers in front of the IFFT indicate frequency components, that is, subcarrier numbers, and the reason why the null subcarrier is inserted into the zero subcarrier is 0 data. After the IFFT, the reference point of the preamble sequence in the time domain, that is, it represents the DC component in the time domain. In addition, among the 200 subcarriers actually used, subcarriers except the subcarrier O, that is, 28 subcarriers from -128, ..., -101, and 27 subcarriers from 101 to 127 are also used. Null data is inserted. Here, the reason why the null data is inserted into the 28 subcarriers from -128, ...., -101 and the 27 subcarriers from 101 to 127 is -128, ...., -101 This is to give a guard interval in the frequency domain because the 28 subcarriers of P and 27 subcarriers 101 through 127 correspond to high frequencies in the frequency domain. As a result, when a preamble sequence PD (-100: 100) or P1subch (-100: 100) or P2subch (-100: 100) in the frequency domain is input to the IFFT, the IFFT is a preamble sequence PD ( -100: 100) or P1subch (-100: 100) or P2subch (-100: 100) is mapped to the corresponding subcarriers and inverse fast Fourier transform to output as a preamble sequence in the time domain. Here, the P1subch (-100: 100) is a preamble sequence of a frequency domain when one partial channel is used in the partial channelization process, and the P2subch (-100: 100) is a partial channel in the partial channelization process. This is a preamble sequence in the frequency domain when these two are used. Since the present invention considers only the case where all four partial channels are used, that is, only the partial channels are not used, the preamble sequences when the partial channels are partially used, that is, P1subch (-100: 100) and P2subch ( -100: 100) will not be described in detail.

Next, the mapping relationship with subcarriers of the preamble sequence according to an embodiment of the present invention will be described in detail.

(1) Using all partial channels, i.e. all four partial channels

When all four partial channels are used, the preamble sequence PD (-100: 100) is mapped to subcarriers. In the process of mapping the preamble sequence PD (-100: 100) to subcarriers, 28 subcarriers of -128, ..., -101, which are guard interval components, and 27 subcarriers of 101 to 127 The process of inserting null data is the same as in a conventional OFDM communication system. However, unlike the conventional OFDM system, when all four partial channels are used, the preamble sequence PD (-100: 100) is applied to the remaining 200 subcarriers other than the guard interval components to correspond to the <preamble sequence mapping rule>. To map. However, null data (0 data) is inserted into subcarrier 0 of the PD (-100: 100) so that a DC component of a time domain is taken into consideration.

(2) When using one partial channel

When using the one partial channel, a preamble sequence P1subch (-100: 100) is mapped to subcarriers. The process of mapping the preamble sequence P1subch (-100: 100) to subcarriers includes 28 subcarriers of -128, ..., -101, which are guard interval components, and 27 subcarriers of 101 to 127. Inserting null data is the same as a conventional OFDM communication system. The preamble sequence P1subch (-100: 100) is mapped to the remaining 200 subcarriers corresponding to the partial channel used when mapping the preamble sequence P1subch (-100: 100). However, null data (0 data) is inserted into subcarrier 0 of the P1subch (-100: 100) so that DC component in the time domain is taken into consideration. As described above, when partial channels are partially used, that is, when one partial channel is used as described above, the detailed description thereof will be omitted here.

(3) When using two partial channels

When using the two partial channels, P2subch (-100: 100) is mapped to subcarriers. The process of mapping the preamble sequence P2subch (-100: 100) to subcarriers includes nulls for 28 subcarriers of -128, ..., -101, which are guard interval components, and 27 subcarriers of 101 to 127. The process of inserting data is the same as in a conventional OFDM communication system. The preamble sequence P2subch (-100: 100) is mapped to the remaining 200 subcarriers corresponding to the partial channel used when mapping the preamble sequence P2subch (-100: 100). However, null data (0 data) is inserted into subcarrier 0 of the P2subch (-100: 100) so that DC component in the time domain is considered. As described above, when partial channels are partially used, that is, when two partial channels are used as described above, the detailed description thereof will be omitted here.

Next, a process of generating a preamble sequence according to the present invention will be described with reference to FIG. 6.

6 is a diagram illustrating a preamble sequence mapping process according to an embodiment of the present invention.

Referring to FIG. 6, in step 611, the transmitter checks whether a signal to be transmitted is an uplink signal. If the signal to be transmitted is not an uplink signal, that is, a downlink signal, the transmitter proceeds to step 613. In step 613, the transmitter inputs a preamble sequence corresponding to the downlink signal, that is, S (-100: 100) or P (-100: 100) as an IFFT, so that the corresponding preamble sequence is performed when performing the IFFT. Control to be mapped to the corresponding subcarriers and ends. In step 611, if the signal to be transmitted is an uplink signal, the transmitter proceeds to step 615. In step 615, the transmitter checks whether all partial channels are used for uplink signal transmission. The transmitter proceeds to step 617 when the partial channel is completely used when transmitting the uplink signal. In step 617, as described above with reference to FIG. 5, the transmitter controls and maps the preamble sequence PD (-100: 100) proposed by the present invention to subcarriers. That is, the transmitter inserts null data into subcarrier 0, which is a DC component of the time domain, and 28 subcarriers of -128, ..., -101, which are guard interval components, and 27 subcarriers from 101 to 127. Null data is inserted into subcarriers and the preamble sequence PD (-100: 100) is mapped to the remaining 200 subcarriers.

On the other hand, if the partial channel is not used when transmitting the uplink signal in step 615, the transmitter proceeds to step 619. In step 619, the transmitter determines whether one partial channel is used when transmitting the uplink signal. In case of using one partial channel when transmitting the uplink signal, the process proceeds to step 621. In step 621, the transmitter inserts null data into subcarrier 0, which is a DC component of the time domain, and 28 subcarriers of -128, ..., -101, which are guard period components, and 101 through 127. Null data is inserted into the 27 subcarriers of the control, and the control is performed to map the preamble sequence P1subch (-100: 100) to the remaining 200 subcarriers.

On the other hand, in step 619, when the uplink signal transmission does not allocate one partial channel, that is, when two allocations, the transmitter proceeds to step 623. In step 623, the transmitter inserts null data into subcarrier 0, which is a DC component of the time domain, and 28 subcarriers of -128, ..., -101, which are guard interval components, and 101 to 127. Null data is inserted into the 27 subcarriers of the subcarrier and control is performed to map the preamble sequence P2subch (-100: 100) to the remaining 200 subcarriers.

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 proposes a preamble sequence characteristic when the partial channels are used in the uplink partial channelization process in an OFDM communication system, that is, a preamble sequence having a minimum PAPR that does not apply the partial channel scheme as a result. It has the advantage of improving. This preamble sequence generation with the minimum PAPR has the advantage of improving the overall performance of the OFDM communication system.

1 illustrates a long preamble sequence structure of a conventional OFDM communication system.

2 illustrates a short preamble sequence structure of a conventional OFDM communication system.

3 is a diagram schematically illustrating a mapping relationship between subcarriers and a preamble sequence when performing IFFT in a conventional OFDM communication system.

4 schematically illustrates a transmitter structure of a conventional OFDM communication system.

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

6 illustrates a preamble sequence mapping process according to an embodiment of the present invention.

Claims (4)

An apparatus for generating a preamble sequence in an orthogonal frequency division multiplexing communication system having a first number of subcarriers and a second number of subchannels generated by classifying the first number of subcarriers into a predetermined number. A preamble sequence generator for generating a preamble sequence having a third number of components when using the same number of partial channels as the second number in the orthogonal frequency division multiplexing communication system; Inserting null data into subcarriers corresponding to a DC component among the first number of subcarriers and an interference cancellation component between subcarriers, and the third number other than subcarriers in which the null data is inserted among the first number of subcarriers And an inverse fast Fourier transformer inserting each of the third number of preamble sequence components into each of the subcarriers of the inverse fast Fourier transform. The method of claim 1, The preamble sequence generator generates a preamble sequence such as PD (-100: 100) when the first number is 256. A method for generating a preamble sequence in an orthogonal frequency division multiple communication system having a first number of subcarriers and a second number of subchannels generated by classifying the first number of subcarriers into a preset number, the method comprising: Generating a preamble sequence having a third number of components when using the same number of partial channels as the second number in the orthogonal frequency division multiplexing communication system; Inserting null data into subcarriers corresponding to a DC component among the first number of subcarriers and an interference cancellation component between subcarriers, and the third number other than subcarriers in which the null data is inserted among the first number of subcarriers And inserting each of the third number of preamble sequence components into each of subcarriers of the inverse fast Fourier transform. The method of claim 3, If the first number is 256, the preamble sequence is generated as in the following PD (-100: 100).