KR100478932B1 - Code allocation/search apparatus on multicarrier communication, and code management system and method thereof - Google Patents

Abstract

The present invention relates to a code assignment / retrieval device, a code management system and a method thereof in multi-carrier communication. To this end, the present invention, the step of initializing a counter for counting the number of users and orthogonal codes according to the user input data, setting a reference PAR indicator value, by checking whether or not the user assigned to the orthogonal code corresponding to the current orthogonal code counter orthogonal Determining the next counting of the sign counter; comparing the orthogonal counter with the orthogonal order; calculating and comparing PARs for all orthogonal codes; comparing the order of orthogonal codes for all users by comparing the order of the orthogonal code with the user counter. And checking the assignment, and performing orthogonal code retrieval for the additional users while maintaining orthogonal codes of users who are already assigned orthogonal codes, to complete orthogonal code setting for all users. Therefore, the present invention reduces the complexity by optimizing the sign only for the user's sign and reduced symbol combination added as the number of users increases, as well as calculating the PAR close to the minimum PAR of the entire symbol combination, The amount of computation is significantly reduced, and also provides the effect of searching the code combination for all users in a short time.

Description

Code Allocation / Retrieval Apparatus, Code Management System, and Method Thereof in Multi-Carrier Communication {CODE ALLOCATION / SEARCH APPARATUS ON MULTICARRIER COMMUNICATION, AND CODE MANAGEMENT SYSTEM AND METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to multi-carrier code division multiple access, and more particularly, to a code assignment / retrieval apparatus, a code management system, and a method thereof in multi-carrier communication for obtaining an orthogonal code assignment order for minimizing peak to average power ratios. .

A multi-carrier code division multiple access (CDMA) system uses orthogonal codes between users or data channels, and modulates orthogonal code chip symbols constituting each data symbol on different carriers and transmits them simultaneously.

In such a multi-carrier CDMA system, since chip symbols forming an arbitrary symbol are simultaneously transmitted on each carrier, the orthogonal code combination assigned to the user has a high correlation with the PAR.

In general, a multi-carrier communication system has a high peak-to-average ratio (PAR) characteristic. Therefore, a multi-carrier CDMA system is researching various methods for reducing peak power of a transmission signal.

Existing multi-carrier CDMA system adopts the method generally used in orthogonal frequency division multiplexing (OFDM) system to reduce PAR.

However, unlike conventional orthogonal frequency division multiplexing systems, multi-carrier CDMA systems have a degree of freedom in orthogonal code combination space, so that the PAR value is highly dependent on the code combination, so that a more efficient PAR reduction can be obtained by appropriately using this code combination.

In a conventional multicarrier CDMA system, a PAR reduction scheme using code combinations allocates two orthogonal orthogonal codes to each user and selects a code that minimizes the overall PAR.

As described above, the number of possible user code combinations is greatly limited, and there is a problem of calculating and selecting a new user's code every time according to an orthogonal code selected by existing users.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and an object thereof is a code allocation / retrieval apparatus and a code management system thereof in a multi-carrier communication for reducing peak-to-average power ratio in a multi-carrier communication system. And to provide a method.

Code management method in the multi-carrier communication according to the present invention for solving the above problems, a) initializing a counter for counting the number of users and orthogonal codes according to the user's input data, and the reference peak power ratio to average power ratio (PAR Setting an indicator value; b) determining whether or not a user is assigned an orthogonal code corresponding to a current orthogonal code counter and determining a next counting of the orthogonal code counter; c) comparing the orthogonal code counter with an orthogonal code order Calculating and comparing PARs for all orthogonal codes; d) comparing the order of orthogonal codes with the user counter and checking whether or not orthogonal codes are assigned to all users; And e) performing an orthogonal code search for the added user while completing orthogonal code setting for all users while maintaining orthogonal codes of users who have already been assigned orthogonal codes according to the orthogonal code assignment check result. It is characterized by including.

delete

Here, the user counter is initialized to 1, and after the reference PAR index value is initialized to a maximum value, the orthogonal code counter is initialized to 1.

And, step b),

A) checking whether an orthogonal code corresponding to a current orthogonal counter is already assigned to a previous user; B) if the orthogonal code in step a) is assigned to the user, incrementing the orthogonal code counter by one and checking whether or not the next orthogonal code is assigned to the user; C) calculating a temporary PAR index value of the final multi-carrier output signal y (t) for the orthogonal code when the orthogonal code in step a) is not assigned to the user; And d) comparing the temporary PAR index value calculated in the step c) with the reference PAR index value and setting a temporary allocation code of the user.

Computing the temporary PAR index value in the step c),

PAR is calculated for orthogonal codes that are not assigned to previous users, so that the orthogonal code having the minimum PAR is selected.

Computing the temporary PAR index value in the step c),

It is characterized by using any one of a method of calculating using the value of the PAR itself, the stochastic PAR threshold, the frequency exceeding the PAR threshold.

At this time, the PAR itself value is defined by the following equation as the maximum value of the output signal divided by the average value of the output signal for a certain time;

(Where y (t) is an output signal, P _tmp is a temporary PAR index value, and A and Ts are arbitrary times).

The probabilistic PAR threshold is defined by the following equation as the probability that the PAR value for one symbol period Ts is greater than the temporary PAR index value satisfies a;

The frequency of exceeding the PAR threshold is the probability value that the maximum value during one symbol period is greater than the threshold value (THR), which is defined by the following equation:

It is characterized by.

In step d), the step of setting a temporary assignment code of a user includes:

Comparing the reference PAR index value with a temporary PAR index value; When the reference PAR indicator value is larger than the temporary PAR indicator value, the temporary PAR indicator value is reset to the reference PAR indicator value and the orthogonal code corresponding to the current orthogonal counter is replaced with the temporary assignment code of the user corresponding to the current user counter. Incrementing the orthogonal code counter by one after setting; And if the reference PAR index value is smaller than the temporary PAR index value, incrementing only the orthogonal code counter by 1 and maintaining the previous user's temporary assignment code.

Step e),

If the check result of step d) indicates that the user counter is less than or equal to the degree of the orthogonal code, the reference PAR index value is initialized to the maximum representable value, and orthogonal to the user added while maintaining orthogonal codes of the previously assigned users. Repeating the code retrieval process; And if the check result of step d) exceeds the degree of the orthogonal code for the user counter, determines that the check for all orthogonal codes for the user counter has been completed, and assigns the code set to the user's temporary assignment code to the current user counter. Setting to an assignment code for

Searching for the sign in step e),

The PAR index value of the final multi-carrier output signal y (t) is characterized in that the code is retrieved by setting the number of parallel transmission data for the user input data to a minimum.

Searching for the sign in step e),

The PAR index value of the final multicarrier output signal y (t) is characterized in that the code is searched by setting the order of the orthogonal modulation method to the minimum.

On the other hand, the feature of the code allocation device in the multi-carrier communication according to the present invention, the serial / parallel conversion unit for converting the data string according to the user input data into the form of parallel transmission data for each user; A code spreader for spreading a signal by assigning orthogonal codes to the data converted by the serial / parallel converter; A code allocator for searching for an orthogonal code for a user to be added while maintaining orthogonal codes of previous users to which the orthogonal code is already assigned to the code spreader and assigning different orthogonal codes to each user; An operation unit for generating a signal in a frequency domain to be allocated to each multi-carrier by calculating a signal of each user spread by the code spreader; And an Inverse Discrete Fourier Transform (IDFT) unit for generating and outputting a signal in the frequency domain generated by the operation unit as a final multi-carrier output signal y (t) through interleaving and serial / parallel transformation.

A feature of a code retrieval apparatus in multi-carrier communication according to the present invention includes: a user data unit for generating and outputting data for each user into a complex signal according to a modulation scheme; A code spreader for spreading a signal by multiplying orthogonal codes respectively assigned to complex signals generated for each user in the user data unit; An output signal generator for generating and outputting a final multi-carrier output signal using the signal spread for each user by the code spreader; A PAR measuring unit for measuring a temporary peak-to-average power ratio (PAR) index value of the final multi-carrier output signal output from the output signal generator; And a code allocation unit for allocating different orthogonal codes per user in order to the code spreading unit and searching for user-specific allocation codes according to the temporary PAR index values measured by the PAR measuring unit.

A feature of the code management system in multi-carrier communication according to the present invention is to maintain a minimum peak to average power ratio (PAR) by changing orthogonal codes for additional users and performing reduced symbol combinations as the number of users increases. A code assignment module; And a code retrieval module for retrieving a code combination for all users by retrieving orthogonal codes for each user sequentially based on the signal by the code assignment module.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating the configuration of a code assignment apparatus in a code management system in multi-carrier communication according to an embodiment of the present invention, which is an example of a code assignment apparatus in multi-carrier communication. The configuration is shown.

As shown in FIG. 1, a code assignment apparatus according to an exemplary embodiment of the present invention includes a serial / parallel conversion unit 110, a code spreader 120, a code assignment unit 130, an adder 140, and an interleaver. And a serial / parallel conversion unit 150 and an inverse discrete fourier transform (IDFT) unit 160.

The serial / parallel conversion unit 110 converts the user input data strings in parallel with a 1: M ratio, where M is the number of parallel transmission data for each user.

The code spreader 120 multiplies the orthogonal codes by the data converted in parallel by the serial / parallel converter 110 to spread the signal in a 1: L ratio. Where L is the order of the diffusion code.

The code assignment unit 130 searches for an orthogonal code for a user to be added while maintaining orthogonal codes of previous users who have already been assigned an orthogonal code, and assigns different orthogonal codes to the code spreader 120 for each user. Perform.

The adder 140 adds a signal of each user spread by the code spreader 120 to generate a signal in a frequency domain to be allocated to each carrier, and the interleaver and the serial / parallel converter 150 add the signal 140. Interleaved signals in the frequency domain generated by using the M: L block interleaver and perform serial / parallel conversion.

The IDFT unit 160 receives the interleaved and serial / parallel conversion signals from the interleaver and the serial / parallel conversion unit 150 to convert the signals of each subcarrier into signals in the time domain to create a multicarrier signal.

In the above, when the number of orthogonal codes, that is, the order of orthogonal codes is L and the number of users is K, the number of combination branches of orthogonal code assignments possible in the code assignment unit 130 is expressed by Equation 1 below.

In Equation 1, as the order L of the orthogonal load increases, the number of possible code combinations increases rapidly.

The output signal y (t) output from the IDFT unit 160 may be represented by Equation 2 below.

Here, M is the number of parallel transmission data, L is the degree of orthogonal code, and K is the current number of users. y (t) is the output signal of the multi-carrier CDMA system, Is the mth parallel data of the kth user, Denotes the first chip of the orthogonal code assigned to the k-th user, and Ts denotes the period of one symbol of the multi-carrier CDMA system.

In Equation 2, since a PAR characteristic is greatly changed according to a combination of orthogonal codes assigned to each user, a code combination that minimizes PAR, It is about how to find.

2 is a diagram illustrating a configuration of a code retrieval apparatus in a code management system of a multi-carrier communication system according to an embodiment of the present invention, wherein the code retrieval apparatus is based on a transmission signal of a multi-carrier CDMA system.

As shown in FIG. 2, the code retrieval apparatus according to the embodiment of the present invention includes a user data generator 310, a code spreader 320, an output signal generator 330, a PAR measurer 340, and a code assigner. And 350.

The user data generator 310 generates and outputs data for each user as a complex signal according to a modulation scheme. The code spreader 320 spreads the signal by multiplying orthogonal codes assigned to the complex signals generated for each user by the user data generator 310.

On the other hand, the output signal generator 330 generates a final multi-carrier CDMA output signal using the signal spread for each user. The PAR measuring unit 340 measures a temporary PAPR index value of the output signal output from the output signal generator 330.

In this case, the code assignment unit 350 allocates the orthogonal codes optimized differently for each user to the code spreader 320 in order, and accordingly, are allocated for each user according to the temporary PAR index values measured by the PAR measurement unit 340. Search for orthogonal codes.

The operation of the code management system in the multi-carrier communication according to the embodiment of the present invention configured as described above will be described in detail with reference to the accompanying drawings.

3 is a flowchart illustrating a code management method in multi-carrier communication according to an embodiment of the present invention.

As shown in FIG. 3, the method according to the embodiment of the present invention illustrates a code assignment and retrieval process performed by the code assignment units 130 and 350 shown in FIGS. 1 and 2. Set to one user (S1).

The reference PAR index value is initialized to the maximum representable value (S2), and the orthogonal code counter is initialized to L = 1 (S3). Here, the orthogonal code counter is a Walsh counter, which designates an orthogonal code corresponding to the orthogonal code counter among the Lth orthogonal codes.

Next, it is checked whether the orthogonal code corresponding to the current orthogonal code counter has already been assigned to the previous user (S4). At this time, when the orthogonal code is not assigned to the previous user, the orthogonal code corresponding to the current orthogonal code counter is assigned to the user, and the temporary PAR index of the output signal y (t) given by Equation 2 above. The value is calculated (S5).

For example, the K-1 user is assigned an orthogonal code from C ₀ to C _K-1 that is already assigned and the orthogonal code corresponding to the orthogonal counter is temporarily assigned to the K th user, and then the orthogonal code is applied. Set the PAR value of the output signal to a temporary PAR index value.

In the above, the temporary PAR index value P _tmp is calculated by Equations 3 to 5 below. That is, the temporary PAR indicator value may use a value of the PAR itself as shown in Equation 3, or may use a PAR threshold that satisfies a given probability as shown in Equation 4, and a frequency exceeding the PAR threshold as shown in Equation 5. Can also be used.

The temporary PAR index value using Equation 3 is a value obtained by dividing the maximum value of the output signal y (t) by the average value of the output signal for an arbitrary time A · Ts.

Here, A is a variable for indicating the signal observation interval and is used to replace the PAR value for a limited time when the PAR calculation amount for the symbol combination is enormous. The larger A is, the temporary PAR index value is closer to the actual maximum PAR.

The temporary PAR index value using Equation 4 represents a value obtained by dividing the maximum value during one symbol period Ts by an average value, that is, a probability that a PAR value of one symbol is larger than the temporary PAR index value satisfies a.

The temporary PAR index value shown in Equation 5 represents a probability value in which the maximum value during one symbol period Ts is larger than the threshold value THR.

As described above, regardless of the number of parallel transmission data (M) and the modulation scheme (QPSK, 16-QAM, 64-QAM, etc.), the superiority of the PAR performance according to the code combination is constant during the calculation of the temporary PAR index value. Faster retrieval is possible by setting the parallel transmission data as small as possible and by lowering the order of the orthogonal modulation scheme.

The temporary PAR index values thus calculated are compared with the reference PAR index values (S6). In this case, when the reference PAR index value is larger than the temporary PAR index value, the temporary PAR index values are reset to the reference PAR index values (S7). Set the orthogonal code corresponding to the current orthogonal code counter as the temporary assignment code of the user corresponding to the current user counter (S8).

In the above, when the user's temporary assignment code is set, the orthogonal code counter is increased by one (S9).

On the other hand, when the reference PAR indicator value is smaller than the temporary PAR indicator value, only the orthogonal code counter is incremented by 1 without resetting the reference PAR indicator value and setting the user's temporary assignment code as described above (S9). That is, in this case, the reference PAR index value and the temporary assignment code of the user are kept as previously.

On the other hand, if the orthogonal code is already assigned to the previous user in step S4 above, the orthogonal code counter is incremented by one (S9), and the orthogonal code is repeated to the user by repeating the process of checking whether the orthogonal code is assigned to the user. If not, proceed to the next step.

Next, the orthogonal code counter and the orthogonal code order are compared to determine whether the process of calculating and comparing the reference PAR index value and the temporary PAR index value for all orthogonal codes is completed.

If the orthogonal counter is less than or equal to the order of the orthogonal code, it means that the process of calculating and comparing PAR index values for some orthogonal codes has not been performed. Therefore, the above process is performed for orthogonal codes corresponding to the orthogonal code counter. Repeat it.

However, if the orthogonal code counter is larger than the order of the orthogonal code, the process of calculating and comparing the PAR index values is performed for all orthogonal codes, and then proceeds to the next process.

In this way, since all orthogonal codes of the current user counter have been checked, the code set as the temporary assignment code of the user is set as the assignment code for the current user counter, and the user counter is incremented by one (S11, S12).

Then, it is checked whether the assigned codes for all users are set by comparing the order of the user counter and the orthogonal code (S13). That is, the maximum possible number of concurrent users matches the degree of the orthogonal code, so the order of the orthogonal code and the user counter are compared.

Here, when the user counter is less than the order of the orthogonal code, the reference PAR index value is initialized again to the maximum representable value, and the orthogonal code search process for the added user is repeated while maintaining orthogonal codes of the previously assigned users. .

By the way, when the user counter is larger than the order of the orthogonal codes, the orthogonal codes for all the users have been set, and thus the orthogonal code assignment according to the number of users is finally finished (S14).

The code management method in the multi-carrier communication mentioned above may be implemented as a program and stored in a computer-readable recording medium, that is, a CD-ROM, a RAM, a ROM, a floppy disk, a hard disk, a magneto-optical disk, or the like.

In general, in order to find an optimal orthogonal code combination in a multi-carrier communication system, it is necessary to find a code combination that obtains a PAR from all possible data symbol combinations for all possible code combinations and minimizes them.

Therefore, the computational amount of the system increases exponentially with respect to the data modulation order and the orthogonal order.

However, the present invention can maintain the minimum PAR by optimizing the user's code as long as the number of users becomes K + 1 while maintaining the optimal code combination for K users, and reduced arbitrary symbol combinations. Only PAR close to the minimum PAR of the entire symbol combination can be obtained.

In addition, in the existing system, it is practically impossible to search the total possible combinations when the order of orthogonal codes and the number of users are large. However, the present invention searches the orthogonal codes for each user and searches the code combinations for all users within a short time. You can search.

The drawings and detailed description of the invention are merely exemplary of the invention, which are used for the purpose of illustrating the invention only and are not intended to limit the scope of the invention as defined in the appended claims or claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The apparatus for allocating / retrieving a code in the multi-carrier communication according to the present invention, the code management system thereof, and the method thereof, which are configured as described above, optimize the code only for a combination of a user's code and a reduced symbol added as the number of users increases. In addition to maintaining the PAR of, the complexity is reduced by calculating the PAR close to the minimum PAR of the entire symbol combination, and the amount of computation is significantly reduced.

In addition, the present invention can search the code combinations for all users in a short time by sequentially searching the orthogonal codes for each user, and can search for the best code combination based on the output signal of the transmitting circuit in the actual multi-carrier communication system It is effective.

In addition, the present invention eliminates power and frequency loss due to additional signal generation, thereby reducing signal power dispersion and requiring only code assignment order, thus eliminating real-time transmission signal processing and optimizing the entire set of possible code combinations. Sign combinations maximize performance.

1 is a diagram illustrating a configuration of a code assignment apparatus in a code management system in multi-carrier communication according to an embodiment of the present invention.

2 is a diagram illustrating a configuration of a code retrieval apparatus in a code management system of a multi-carrier communication system according to an embodiment of the present invention.

3 is a flowchart illustrating a code management method in multi-carrier communication according to an embodiment of the present invention.

Claims (19)

a) initializing a counter for counting a user number and an orthogonal code according to input data of a user, and setting a reference peak power ratio to an average power ratio (PAR) index value; b) determining whether or not a user is assigned an orthogonal code corresponding to a current orthogonal code counter to determine a next counting of the orthogonal code counter; c) calculating and comparing PARs for all orthogonal codes by comparing the orthogonal code counters and orthogonal code orders; d) comparing the order of orthogonal codes with the user counter and checking whether or not an orthogonal code is assigned to all users; And e) completing orthogonal code setting for all users by performing orthogonal code search for additional users while maintaining orthogonal codes of users who have already been assigned orthogonal codes according to the result of checking whether the orthogonal codes are assigned; Code management method in a multi-carrier communication comprising a. The method of claim 1, In the step a), the user counter is initialized to 1, and the coded management method in the multi-carrier communication, characterized in that to initialize the orthogonal code counter to 1 after initializing the reference PAR index value to the maximum value. The method of claim 1, wherein b), b-1) checking whether an orthogonal code corresponding to a current orthogonal counter is already assigned to a previous user; b-2) if the orthogonal code is assigned to a user, incrementing an orthogonal code counter by 1 and checking whether a user is assigned a next orthogonal code; b-3) if the orthogonal code is not assigned to a user, calculating a temporary PAR index value of the final multicarrier output signal y (t) for the orthogonal code; And b-4) comparing the calculated temporary PAR index value with the reference PAR index value and setting a temporary allocation code for the user Code management method in a multi-carrier communication comprising a. The method of claim 3, The step b-3) is to calculate the PAR for the orthogonal codes not assigned to the previous users to select the orthogonal code having the minimum PAR, characterized in that for multi-carrier communication. The method of claim 3, In step b-3), any one of a method of calculating using a value of a PAR itself, a stochastic PAR threshold, and a frequency exceeding a PAR threshold is used. The method of claim 5, The PAR itself value is defined by the following equation as the maximum value of the output signal divided by the average value of the output signal for a certain time; (Where y (t) is an output signal, P _tmp is a temporary PAR index value, and A and Ts are arbitrary times). The probabilistic PAR threshold is defined by the following equation as the probability that the PAR value for one symbol period Ts is larger than the temporary PAR index value satisfies a; The frequency of exceeding the PAR threshold is a probability value in which the maximum value during one symbol period is larger than the threshold value (THR), which is defined by the following equation. Code management method in multi-carrier communication characterized in that. The method of claim 3, wherein b-4) comprises: Comparing the reference PAR index value with a temporary PAR index value; If the reference PAR indicator value is larger than the temporary PAR indicator value, the temporary PAR indicator value is reset to the reference PAR indicator value, and the orthogonal code corresponding to the current orthogonal code counter is assigned to the temporary assignment code of the user corresponding to the current user counter. Incrementing the orthogonal code counter by one after setting; And If the reference PAR indicator value is smaller than the temporary PAR indicator value, only the orthogonal code counter is incremented by 1 and maintaining the temporary assignment code of the previous user.  Code management method in a multi-carrier communication comprising a. The method of claim 1, wherein step e) e-1) If the check result of step d) is the user counter is less than or equal to the degree of the orthogonal code, the user is added while initializing the reference PAR indicator value to the maximum representable value, while maintaining the orthogonal codes of the previously assigned users Repeating the orthogonal code search process for; And e-2) If the check result of step d) is that the user counter exceeds the degree of the orthogonal code, it is determined that all the orthogonal codes for the user counter have been checked, and the code set as the user's temporary assignment code is Setting as an Assignment Code for a User Counter Code management method in a multi-carrier communication comprising a. The method of claim 1, In the step e), the PAR index value of the final multi-carrier output signal (y (t)) in the multi-carrier communication characterized in that to search for a code by setting the number of parallel transmission data for the user's input data to a minimum Code management method. The method of claim 1, In the step e), the PAR index value of the final multicarrier output signal y (t) is a code management method for retrieving a code by setting the order of the orthogonal modulation scheme to a minimum. A serial / parallel converter for converting a data string according to user input data into a form of parallel transmission data for each user; A code spreader for spreading a signal by assigning orthogonal codes to the data converted by the serial / parallel converter; A code allocator for searching for an orthogonal code for a user to be added while maintaining orthogonal codes of previous users to which the orthogonal code is already assigned to the code spreader and assigning different orthogonal codes to each user; An operation unit for generating a signal in a frequency domain to be allocated to each multi-carrier by calculating a signal of each user spread by the code spreader; And An Inverse Discrete Fourier Transform (IDFT) unit which generates and outputs a signal in a frequency domain generated by the operation unit as a final multicarrier output signal y (t) through interleaving and serial / parallel conversion. Code assignment apparatus in multi-carrier communication comprising a. The method of claim 11, wherein the code assignment unit, A user counter for counting the number of users according to user input data; And Orthogonal code counter for counting whether or not to assign orthogonal codes for each user according to the user counter Code assignment apparatus in multi-carrier communication comprising a. The method according to claim 11 or 12, wherein And the code assignment unit selects an orthogonal code having a minimum PAR by calculating a PAR for orthogonal codes that have not been assigned to previous users. The method of claim 13, The PAR calculation of the code assignment unit uses any one of a method of calculating using a value of a PAR itself, a stochastic PAR threshold, and a frequency exceeding a PAR threshold. The method of claim 14, The PAR itself value is defined by the following equation as the maximum value of the output signal divided by the average value of the output signal for a certain time; (Where y (t) is an output signal, P _tmp is a temporary PAR index value, and A and Ts are arbitrary times). The probabilistic PAR threshold is defined by the following equation as the probability that the PAR value for one symbol period Ts is larger than the temporary PAR index value satisfies a; The frequency of exceeding the PAR threshold is a probability value in which the maximum value during one symbol period is larger than the threshold value (THR), which is defined by the following equation. Code assignment apparatus in multi-carrier communication characterized in that. A user data unit which generates and outputs data for each user as a complex signal according to a modulation scheme; A code spreader for spreading a signal by multiplying orthogonal codes respectively assigned to complex signals generated for each user in the user data unit; An output signal generator for generating and outputting a final multi-carrier output signal using a signal spread for each user understood by the code spreader; A PAR measuring unit for measuring a temporary peak-to-average power ratio (PAR) index value of the final multi-carrier output signal output from the output signal generator; And A code assigning unit for allocating different orthogonal codes per user in order to the code spreading unit in order and searching for a user-specific assigned code according to a temporary PAR index value measured by the PAR measuring unit. Code retrieval apparatus for multi-carrier communication comprising a. The method of claim 16, The code assignment unit, the PAR index value of the final multi-carrier output signal is a code retrieval device for multi-carrier communication, characterized in that for searching the code by setting the minimum number of parallel transmission data for the user input data. The method of claim 16, The code assignment unit, the PAR index value of the final multi-carrier output signal is a code retrieval device for multi-carrier communication, characterized in that to search for a code by setting the order of the orthogonal modulation method to a minimum. A code allocation module for changing orthogonal codes for additional users as the number of users increases and performing reduced symbol combinations to maintain a minimum peak power ratio to average power ratio PAR; And A code retrieval module for retrieving code combinations for all users by retrieving orthogonal codes for each user sequentially based on the signal by the code assignment module Code management system in a multi-carrier communication comprising a.