KR100662506B1 - Apparatus and its method for deciding user code according to number of connecting user and, apparatus and its method for generating user code using the same in quasi-synchronous cdma system - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus and method for determining a user code according to the number of access users in a quasi-synchronous code division multiple access system, and a scrambling based user code generation / spreading apparatus and a method thereof.

2. The technical problem to be solved by the invention

The present invention divides a user code into a plurality of (2) code groups on the base station side of the quasi-synchronous code division multiple access system, and then determines a specific code group according to the number of currently connected users and transmits the specific code group to the terminal. By using a scrambling code pattern that generates a user code according to the determined code group and minimizes the correlation characteristics between user codes, the number of connected users in the quasi-synchronous code division multiple access system to minimize the interference component between user codes within the synchronization error range An object of the present invention is to provide an apparatus and method for determining a user code, and an apparatus and method for generating and spreading a user code based on scrambling using the same.

3. Summary of the Solution of the Invention

According to an aspect of the present invention, there is provided an apparatus for determining a user code according to the number of connected users in a quasi-synchronous code division multiple access system, comprising: connection number counting means for counting the number of current users according to a user connection / release request signal received from a terminal; A corresponding user code group is determined by checking a value of the number of access user counts according to the user access request signal received from the terminal, and the number of access user counts according to the user access cancellation request signal received from the terminal. Code group selection / switching determining means for determining a value group of the user and a code group of the termination request user to switch the code group among the currently connected users; And code group selection / switching signal transmitting means for transferring the code group selection / switching signal to the corresponding terminal under the control of the code group selection / switching determining means.

4. Important uses of the invention

The present invention is used for quasi-synchronous code division multiple access system.

Quasi-synchronous code division multiple access system, user code generation, code group selection, orthogonality, scrambling

Description

Apparatus and method for determining user code according to the number of access users in quasi-synchronous code division multiple access system and apparatus for generating / spreading user code based on scrambling using the same and method thereof AND, APPARATUS AND ITS METHOD FOR GENERATING USER CODE USING THE SAME IN QUASI-SYNCHRONOUS CDMA SYSTEM}             

1 is a configuration diagram of an apparatus for determining a user code according to the number of access users and a scrambling-based user code generation / spreading apparatus using the same in the quasi-synchronous code division multiple access system according to the present invention;

2 is a flowchart illustrating a method for determining a user code according to the number of access users and a scrambling based user code generation / spreading method using the same in the quasi-synchronous code division multiple access system according to the present invention;

3 is a detailed flowchart illustrating a code group selection process according to a user access request signal among scrambling-based user code determination methods in a quasi-synchronous code division multiple access system according to the present invention;

4 is a detailed flowchart illustrating a code group switching process according to a user access cancellation request signal among user code determination methods according to the number of access users in a quasi-synchronous code division multiple access system according to the present invention;

5 shows all possible code pairs when using a scrambling code capable of keeping the code correlation at 0 for the number of users having N / 2 or less when the length of the user code is 32 and the synchronization between the user codes is one chip. Three-dimensional graph of correlation values,

6 shows the number of users for the PPGC code, the WH code, the PPGC code additionally using the optimized scrambling code, and the WH code additionally using the optimized scrambling code according to the present invention when the length of the user code is 32. This is a graph of the maximum correlation value between signs.

* Explanation of symbols on the main parts of the drawing

11: user code determination device 111: number of connected users counter

112: code group selection / switching decision maker

113: Code Group Selection / Switch Signal Transmitter

12: sign generator 13: first multiplier

14: second multiplier

The present invention relates to a user code determination apparatus and method thereof according to the number of access users in a quasi-synchronous code division multiple access system, and a scrambling-based user code generation / spreading apparatus and a method thereof. On the base station side of the code division multiple access system, the user code is divided into a plurality of (2) code groups, and then a specific code group is determined and transmitted to the terminal according to the current number of connected users, and the user side according to the determined code group A device for determining user code according to the number of connected users in a quasi-synchronous code division multiple access system for minimizing interference components between user codes within a synchronization error range by generating a code and using a scrambling code pattern that minimizes correlation characteristics between user codes. And using the method and scrambling based using the same The present invention relates to a character code generation / spreading device and a method thereof.

Since the satellite communication channel is more likely to have a line of sight than the terrestrial communication channel and there are fewer multipath interference components due to the characteristics of the channel structure, inter-symbol interference (ISI) is higher than that of the terrestrial communication system. ) Has the advantage of low component.

Recently, in satellite systems using Code Division Multiple Access (CDMA) schemes, such a scheme has been proposed to maintain user symbol synchronization in the reverse direction and to reduce interference by using orthogonal codes. .

In general, in a code division multiple access (CDMA) system, the synchronization between users is controlled by a feedback control loop of a base station, so that the synchronization error between users can be perfectly corrected by the change of delay time and the synchronization control finite resolution. It cannot be maintained. In particular, the Walsh-Hadamard (WH) code, which is widely used as a user orthogonal code, has orthogonality when synchronization is satisfied, but when synchronization is misaligned, the maximum possible correlation value is very large. If is present, it is not suitable as a user code code.

That is, in the quasi-synchronous code division multiple access system, even if the orthogonal code is used as the user code, the user-to-user synchronization is not perfect and thus an interference component between users occurs. Therefore, the use of an existing orthogonal code in a quasi-synchronous code division multiple access system, which maintains orthogonality only under the assumption that synchronization is perfect, causes severe performance degradation.

A paper published in the Institute of Electrical and Electronics Engineers (IEEE) Journal (IEEE Journal on Selected Areas in Communications, Volume: 10 Issue: 2, Feb. 1992. Page (s): 328-343). ("Bandlimited quasi-synchronous CDMA: a novel satellite access technique for mobile and personal communication systems" by De Gaudenzi, R.; Elia C.; Viola, R.) maintains synchronization error within one code symbol (chip). We analyzed the performance when PPGC (Perferably Phased Gold Code) was used as a user code in a so-called quasi-synchronous code division multiple access system (hereinafter referred to as quasi-synchronous CDMA system).

Perferably Phased Gold Code (PPGC) is a Gold Code in which the correlation values of all code pairs satisfy -1 when synchronization is maintained, and the maximum correlation value is larger than the WH code even if the synchronization between users is not correct. It has a very small characteristic. Therefore, PPGC is considered as a coding scheme that is very suitable for quasi-synchronous CDMA systems.

However, the PPGC considers only the case where no additional scrambling is performed on the spread code. Therefore, even if the inter-user synchronization is perfectly maintained, the correlation property between user codes does not change after spreading even if scrambling is additionally performed. However, if the synchronization between users does not match, the inter-user correlation property is completely changed by scrambling.

Therefore, in the design of the quasi-synchronous CDMA system, the variation of correlation characteristics due to scrambling must be considered together, and a method for improving the correlation characteristics of codes between users by optimizing scrambling is urgently required.

The present invention has been proposed to solve the above problems and to meet the above requirements, and after dividing a user code into a plurality of code groups (for example, two) at the base station side of the quasi-synchronous code division multiple access system, The specific code group is determined and transmitted to the terminal according to the number of access users, and the user side generates a user code according to the determined code group and uses a scrambling code pattern that minimizes correlation characteristics between user codes. The purpose of the present invention is to provide an apparatus and method for determining a user code according to the number of access users, a scrambling-based user code generation / spreading apparatus, and a method for minimizing the interference component between the multiple synchronization systems. .

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

In the apparatus of the present invention for achieving the above object, in the user code determination apparatus according to the number of access users in the quasi-synchronous code division multiple access system, the current number of users according to the user access / termination request signal received from the terminal counter Connecting user number counting means for performing; Determine a corresponding user code group by checking the value of the number of access user counting means according to the user access request signal received from the terminal, and determine the number of user access counting means according to the user access release request signal received from the terminal. Code group selection / switching determining means for checking a value and a code group of the termination request user to determine a user to switch the code group among the currently connected users; And code group selection / switching signal transmitting means for transferring the code group selection / switching signal to the corresponding terminal under the control of the code group selection / switching determining means.

In addition, another apparatus of the present invention is a scrambling-based user code generation / spreading apparatus in a quasi-synchronous code division multiple access system, comprising: a user code included in a first code group according to a code group selection / switch signal from a base station; Code generation means for selectively outputting a user code included in the second code group; First multiplication means for multiplying and spreading a data symbol by a user code output from the code generating means; And second multiplication means for multiplying and outputting the optimized scrambling pattern to the signal from the first multiplication means.

On the other hand, in the method of the present invention, in the user code determination method according to the number of access users in the quasi-synchronous code division multiple access system, after the current number of access users is increased by 1 according to the user access request signal, the number of current access users is all users Confirming whether the number of access users is less than 1/2 of the number of codes; A first determining step of determining a first code group as a user code group when the number of access users is less than half of the total number of user codes as a result of checking the number of access users; A second determination step of determining a second code group as a user code group when the number of access users is determined as the result of the number of access users; And a code group switch determination step of determining a code group switch user by checking a current number of access users, a code group of the cancel user, and a code group of the remaining access users according to the user access cancellation request signal.

Further, another method of the present invention is a scrambling-based user code generation / spreading method in a quasi-synchronous code division multiple access system, wherein a user of one of the user codes of the corresponding code group according to the code group selection / switching signal from the base station A user code generation step of generating a code; And multiplying the generated user code by a data symbol and then multiplying the optimized scrambling code pattern.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a user code determination device according to the number of access users and a scrambling-based user code generation / spreading device using the same in the quasi-synchronous code division multiple access system according to the present invention.

As shown in FIG. 1, a user code determination apparatus according to the number of access users and a scrambling-based user code generation / spreading apparatus using the same are provided in a base station and a terminal, respectively.

First, the user code determination apparatus 11 according to the number of access users included in the base station receives a user access request signal and a user number to determine a code group of the current access request user according to the current accessor number, and a user termination request signal. By receiving the user number, one of the currently connected users is selected according to the number of the currently connected users and the code group of the terminated user to switch the code group.

That is, the user code determination device 11 is connected to the number of access user counter 111 for counting the current number of users according to the user access / termination request signal received from the quasi-synchronous terminal, the user access request signal received from the terminal The user number group of the current access request user is determined by checking the value of the access user counter 111, and according to the user access request signal received from the terminal, the value and termination of the access user counter 111 are determined. The code group selection / switching determiner 112 and the code group selection / switching determiner 112 determine the user to switch the code group among the current access users by checking the code group of the requesting user. And a code group selection / switch signal transmitter 113 for transferring the switch signal to the corresponding terminal.

Meanwhile, the scrambling-based user code generation / spreading device included in the terminal includes Walsh-Hadamard (WH: Walsh-) included in the A code group according to the code group selection / switching signal received from the user code determination device 11. A code generator 12 for selectively outputting a Walsh-Hadamard (WH) code included in a Hadamard) code or a B code group, and outputted from the code generator 12 to a data symbol from a user terminal A first multiplier 13 for multiplying and spreading a Walsh-Hadamard (WH) code and a second multiplier 14 for outputting a spreading signal by multiplying a signal from the first multiplier with an optimized scrambling pattern ).

Walsh-Hadamard (WH) codes used as user codes in the present invention are divided into two groups (for example, A and B). At this time, when the order (length of user code) of Walsh-Hadamard (WH) code is N, 1 to N in N-th order Walsh-Hadamard (WH) code matrix. Let the code corresponding to the / 2th line be the A code group, and the code corresponding to the 1st + N / 2th to the Nth line is called the B code group. Every user is assigned one code in the A code group or the B code group, and selectively uses the code group according to the command of the base station.

That is, the base station instructs all users to use the same group of codes when the number of currently connected users is less than half the total number of codes. For example, if the number of users is less than half, all users are assigned only the sign of the A code group (the code corresponding to the 1st to N / 2th row in the Nth Walsh-Hadamard code matrix), or the B code group (N In the difference Walsh-Hadamard code matrix, only the code of 1 + N / 2 to Nth row) is assigned.

Each user signal spread by the assigned user code is multiplied by the same scrambling pattern and transmitted. At this time, the scrambling code used in the present invention has the characteristics as shown in FIG. 5 and satisfies the following properties.

1. The period of the scrambling code is equal to the Walsh-Hadamard (WH) code length.

2. The scrambling code is multiplied with the user signal in synchronization with the user spread code.

3. When the scrambling code is S (i), i = 1,2,3, ... N, when the number of users is half of the total number of user codes, that is, N / 2 or less, the scrambling code is represented by the following equation. 1] or [2] satisfies the pattern.

S ((N / 2) + i) = (-1) ⁱ S (i), i = 1,2,3, ..., N / 2

S ((N / 2) + i) =-(-1) ⁱ S (i), i = 1,2,3, ..., N / 2

For example, when N = 32 [S (17), S (18), ..., S (32)] = [S (1), -S (2), S (3), -S ( 4), ..., S (15), -S (16)], or [S (17), S (18), ..., S (32)] = [-S (1) ), S (2), -S (3), S (4), ..., -S (15), S (16)].

4. If the number of users is greater than half of the total number of user codes, ie N / 2, then the optimal value to minimize the correlation in the case of one chip deviation for all possible pairs of Walsh-Hadamard (WH) codes Obtain and use a pattern. This can be obtained through computational experiments.

As such, the scrambling code pattern used in the present invention is optimized to minimize the correlation between user codes. From these characteristics, the present invention can generate a user code with improved correlation performance compared to the existing PPGC.

Referring to Figure 2 will be described in more detail with respect to the overall operating process of the present invention.

2 is a flowchart illustrating a method for determining a user code according to the number of access users and a scrambling-based user code generation / spreading method using the same in the quasi-synchronous code division multiple access system according to the present invention.

First, when the base station (user code determination device 11) receives the user access request signal (201), it determines the code group according to the current number of access users and transmits to the terminal (202).

Then, the terminal (user code generation / spreading device) generates a user code (Walsh-Hadamard (WH) code) of the determined code group (203).

Then, the generated user code is multiplied by the data symbol to be spread (204), and then the optimized scrambling code pattern is multiplied (205).

On the other hand, although not shown in Fig. 2, the base station (user code determination device 11) terminates the connection of the user when receiving the user access cancellation request signal, and if the canceled user code is the A group code, A code group switching process of a user using a B group code is performed. In other words, whether there is a user who is currently using the B group code but has the same code as the A group code used by the revocation user as the A group code, the user's code is converted to the A group code. The detailed processing will be described later in detail with reference to FIG.

3 is a detailed flowchart illustrating a code group selection process according to a user access request signal in a scrambling-based user code determination method in a quasi-synchronous code division multiple access system according to the present invention.

First, after increasing the number of current access users by 1 (301), it is checked whether the number of current access users is less than 1/2 of the total number of user codes (302).

As a result of the check 302, if the number of currently connected users is less than 1/2 of the total number of user codes, the A code group is selected (303).

On the other hand, if the result of the check 302, the number of currently connected users is 1/2 or more of the total number of user code, select the B code group (304).

4 is a detailed flowchart illustrating a code group switching process according to a user access release request signal among user code determination methods according to the number of access users in the quasi-synchronous code division multiple access system according to the present invention.

First, upon receiving the user access termination request signal (401), the number of current access users is decreased by 1 and then the access is terminated (402), and the number of current access users, the sign of the cancel user and the sign of the remaining access users are checked. Switch groups (403). In other words, whether there is a user who is currently using the B group code but has the same code as the A group code used by the revocation user as the A group code, the user's code is converted to the A group code.

On the other hand, as shown in Figure 6, it can be seen that the interference component between the user code can be minimized within the synchronization error range, and Walsh-Hadam (WH: Walsh-) than the PPGC code Hadamard) code will be more suitable.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

As described above, the present invention divides a user code into a plurality of (2) code groups at the base station side of the quasi-synchronous code division multiple access system, and then determines a specific code group according to the number of currently connected users, and transmits them to the terminal. In the terminal side, by using a scrambling code pattern for generating a user code according to the determined code group and minimizing a correlation characteristic between user codes, an interference component between user codes can be minimized within a synchronization error range.

Claims (16)

In the user code determination apparatus according to the number of access users in a quasi-synchronous code division multiple access system, Connection number counting means for counting the current number of connections according to the user connection / release request signal received from the terminal; Determine a corresponding user code group by checking the value of the number of access user counting means according to the user access request signal received from the terminal, and determine the number of user access counting means according to the user access release request signal received from the terminal. Code group selection / switching determining means for checking a value and a code group of the termination request user to determine a user to switch the code group among the currently connected users; And Code group selection / switching signal transmitting means for transmitting the code group selection / switching signal to the corresponding terminal under the control of the code group selection / switching determining means. Device for determining the user code according to the number of access users in a quasi-synchronous code division multiple access system comprising a. The method of claim 1, The step of determining the user code group by the code group selection / switching determination means, Check whether the number of current connected users is less than 1/2 of the total number of user codes. If the number of current connected users is less than 1/2 of the total number of user codes, the first code group is determined as the user code group, and the number of current connected users is all users. And a second code group is determined as a user code group if the number of codes is 1/2 or more, and the user code determination apparatus according to the number of connected users in the quasi-synchronous code division multiple access system. The method of claim 2, Determining the user to switch the code group by the code group selection / switching determination means, If the code used by the cancellation request user is the first code group according to the user access cancellation request signal received from the terminal, the code of the second code group is currently used, but the code of the first code group used by the cancellation request user is used. A user code determination device according to the number of connected users in a quasi-synchronous code division multiple access system, characterized in that a user having the same code as the code as the first code group is determined as a code group switching user. The method according to any one of claims 1 to 3, The first code group is, N (N is a natural number) and includes a user code corresponding to the first to N / 2th rows in a Walsh-Hadamard (WH) sign matrix, The second code group, Connection in a quasi-synchronous code division multiple access system comprising a user code corresponding to 1 + N / 2 th to N th rows in an N th Walsh-Hadamard (WH) code matrix Device for determining user code according to the number of users. An apparatus for generating / spreading a user code based on scrambling in a quasi-synchronous code division multiple access system, Code generation means for selectively outputting a user code included in a first code group or a user code included in a second code group according to a code group selection / switching signal from a base station; First multiplication means for multiplying and spreading a data symbol by a user code output from the code generating means; And Second multiplication means for multiplying and outputting the optimized scrambling pattern to the signal from the first multiplication means A scrambling-based user code generation / spreading apparatus in a quasi-synchronous code division multiple access system comprising a. The method of claim 5, The first code group is, In the Nth Walsh-Hadamard (WH) sign matrix, a user code corresponding to the first to N / 2th rows is included. The second code group, Scrambling in a quasi-synchronous code division multiple access system comprising a user code corresponding to 1 + N / 2 th to N th rows in an N th Walsh-Hadamard (WH) code matrix Based user code generation / spreading device. The method of claim 6, The optimized scrambling pattern, The period is the same as the user code length, Multiplied in synchronization with the user spread code, S ((N / 2) + i) = (-1) ⁱ S (i), i = 1,2,3, ..., if the number of currently connected users is less than half (N / 2) Satisfies the condition of N / 2 or S ((N / 2) + i) =-(-1) ⁱ S (i), i = 1,2,3, ..., N / 2 , Quasi-synchronous code division, characterized in that the optimal scrambling pattern is minimized when the number of currently connected users exceeds half of the total number of user codes (N / 2). A scrambling based user code generation / spreading device in a multiple access system. delete delete The method of claim 5, The user code is, A scrambling based user code generation / spreading apparatus in a quasi-synchronous code division multiple access system, characterized in that it is a Walsh-Hadamard (WH) code. A user code determination method according to the number of access users in a quasi-synchronous code division multiple access system, An increase in the number of current access users by 1 according to the user access request signal, and then confirming whether the number of current access users is less than 1/2 of the total number of user codes; A first determining step of determining a first code group as a user code group when the number of access users is less than half of the total number of user codes as a result of checking the number of access users; A second determination step of determining a second code group as a user code group when the number of access users is determined as the result of the number of access users; And A code group switching decision step of determining a code group switching user by checking the number of current access users, the code group of the canceling user, and the code group of the remaining access users according to a user termination request signal. User code determination method according to the number of access users in a quasi-synchronous code division multiple access system comprising a. The method of claim 11, The code group switching determination step, After the number of current access users is decreased by 1 according to the user access cancellation request signal, the code of the second code group is currently used because the code used by the cancellation request user is the first code group. A user code determination method according to the number of access users in a quasi-synchronous code division multiple access system, wherein the user having the same code as the code of the first code group as the first code group is determined as a code group switching user. A method for generating / spreading a user code based on scrambling in a quasi-synchronous code division multiple access system, A user code generation step of generating one user code among user codes of the corresponding code group according to the code group selection / switching signal from the base station; And Multiplying the generated user code by a data symbol and then multiplying the optimized scrambling code pattern Scrambling-based user code generation / spreading method in a quasi-synchronous code division multiple access system comprising a. The method of claim 13, The first code group is, In the Nth Walsh-Hadamard (WH) sign matrix, a user code corresponding to the first to N / 2th rows is included. The second code group, Scrambling in a quasi-synchronous code division multiple access system comprising a user code corresponding to 1 + N / 2 th to N th rows in an N th Walsh-Hadamard (WH) code matrix Based user code generation / spreading method. The method of claim 13, The optimized scrambling pattern, The period is the same as the user code length, Multiplied in synchronization with the user spread code, S ((N / 2) + i) = (-1) ⁱ S (i), i = 1,2,3, ..., if the number of currently connected users is less than half (N / 2) Satisfies the condition of N / 2 or S ((N / 2) + i) =-(-1) ⁱ S (i), i = 1,2,3, ..., N / 2 , Quasi-synchronous code division, characterized in that the optimal scrambling pattern is minimized when the number of currently connected users exceeds half of the total number of user codes (N / 2). A scrambling based user code generation / spreading method in a multiple access system. delete

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