KR19990075502A - Gold Code Generator Using Mask and Code Searching Method Using Same - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a gold code generator using a mask and a code search method using the same.

2. The technical problem to be solved by the invention

An object of the present invention is to provide a gold code generator capable of converting a code immediately by changing a mask value at an arbitrary phase without any additional information, and a code search method using the same.

3. Summary of Solution to Invention

The present invention relates to a linear feedback shifting means for the first and second r orders, where r is a natural number; A plurality of AND operations means for performing an AND operation on the data output from the second r-th order linear feedback shifting means and the r-bit mask data; First exclusive AND operation means for exclusively ORing the data from the AND product; And second exclusive OR operation means for performing an exclusive OR operation on the data output from the first r-th order linear feedback shift register and the output of the first exclusive OR operation means.

4. Important uses of the invention

Communication field

Description

Gold Code Generator Using Mask and Code Searching Method Using Same

The present invention relates to a gold code generator using a mask and a code search method using the same. In particular, a gold code generator and a code search using the same can be immediately converted to another gold code by converting a mask value at an arbitrary phase without any additional information. It is about a method.

In a code division multiple access (CDMA) communication system, the role of a spreading code generator for generating a code used for spreading a band is very important and is an essential component for each transceiver.

As a code used for spread spectrum in a CDMA communication system, a maximum length code (hereinafter, referred to as an ML code) and a gold code are mainly used. In particular, the ML code has excellent autocorrelation property, but since the number is limited, when a large number of codes are required, a gold code having excellent cross-correlation property is mainly used. This gold code can be generated using two ML code generators, which are preferred pairs.

The ML code generator is described below with reference to FIG.

1 shows a block diagram of an ML code generator. The ML code can be generated by using a linear feedback shift register of order r (where r is a natural number of two or more). The rth order linear feedback shift register consists of r stages and a linear feedback function. the contents of r columns Is defined as a state.

The linear feedback function g (D) is a generation polynomial representing the feedback position, given by

Also, the initial value polynomial a (D) is a polynomial for the initial value of the register.

Given the initial value of polynomial a (D) of the generated polynomial g (D), the generated ML code b (D) is expressed as follows.

Using two ML codes of length N and the first pair, b ₁ (D) and b ₂ (D), a gold code set consisting of N + 2 gold codes is given as follows.

Figure 2 shows a circuit diagram of a gold code generator, which shows a gold code generator obtained using the generation polynomials g (D) and f (D) of two ML codes.

Gold codes is achieved by a combination of g (D) and a the ML code b ₁ generated by the (D) (D) and f (D) and the ML code b ₂ (D) produced by a '(D) . At this time, b ₂ (D) the numeral ⁿ D b ₂ (D) by a phase shift of n it may be made by changing a '(D).

In other words, the generated polynomial representing the feedback link position and the initial value of one shift register can be fixed, and only the initial value of the other shift register can be changed to generate another gold code. In other words, the initial value of the other shift register determines the type of gold sign.

In the case of a CDMA system that communicates using different codes, the receiver must find out the phase of the code in the initial search phase and identify what kind of code is actually used for transmission. The sign search process will be described with reference to FIG.

3 is a flowchart of a code search process according to the prior art.

After searching for the initial phase, in order to find the type of code used in the transmitter, while changing the code of the local generator of the receiver, the correlation value with the received signal is determined to determine whether the codes match.

When using the gold sign, the correlation value is obtained by changing the initial value of one of the two shift registers. At this time, the initial value is a value that is repeated once after passing the length of the sign.

Each time the code of the local generator is changed, it waits until the start of the code (31), sets the code initial value (32), and then obtains the code correlation value (33). After that, it is determined whether all the symbols have been searched (34), and if all the symbols have been searched, the procedure ends. All sign correlation values are obtained, and the sign having the most correlation value among them is determined to be a matching sign.

In this case, since the time taken to search for one code is determined by the length of the code, when the length of the code is long, it takes much time to search the entire code.

On the other hand, after changing the code, the phase of the local generator may be shifted from the initial phase to the present phase of the received signal without waiting until the start point of the code, and then it may be determined whether the code coincides. However, this case also has a problem that there is a delay time for phase shift.

To completely eliminate this delay, it is necessary to know information about the state inside the code generator in any phase. That is, since the code generator must have information on the internal state of the code generator in all phases of all codes, a separate memory is required for storing information.

Accordingly, an object of the present invention is to provide a gold code generator capable of immediately converting a code by changing a mask value at an arbitrary phase without additional information, and a method of searching for a code using the same. There is this.

1 is a circuit diagram of a longest code (ML code) generator.

2 is a circuit diagram of a gold code generator according to the prior art.

3 is a flowchart of a code search process according to the prior art.

4 is an exemplary diagram of the longest code phase shift using a mask.

5 is a circuit diagram of a gold code generator using a mask according to an embodiment of the present invention.

Figure 6 is a flow diagram of one embodiment of a code search process performed using a gold code generator using a mask in accordance with the present invention.

* Explanation of symbols on the main parts of the drawings

1, 2: rth order linear feedback shift register

3, 4: exclusive OR gate

11 to 1r: logical sum gate

In order to achieve the above object, the present invention provides a code generator for generating a gold code, comprising: first and second r-order linear linear shifting means for linearly shifting predetermined data; A plurality of AND operations means for performing AND AND operation on the data output from each stage of the second r-th order linear feedback shifting means and the r-bit mask data; First exclusive AND operation means for performing exclusive OR on the r-bit data output from the AND product; And second exclusive OR operation means for performing an exclusive OR operation on the data output from the first r-th order linear feedback shift register and the output of the first exclusive OR operation means.

In addition, in order to achieve the above object, a code search method using a gold code generator, comprising: a first step of waiting for a start point of a code and setting an initial value; Obtaining a correlation value of a sign; And a third step of determining whether all the symbols have been searched and ending if the search of all the symbols has been completed, and converting the mask to another Gold code if the search has not been completed, and repeating from the second step. do.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 4 to 6.

In the present invention, a sign shifted by n of the ML code b (D) Can be created using a mask.

4 is an exemplary diagram of the longest code phase shift using a mask according to the present invention, and shows such a relationship using an ML code generator of degree 3 and a '101' mask pattern as an example. That is, the relation between the output of the ML code generator and the ML code obtained by using a mask pattern in the ML code generator is shown. As shown in the figure, it can be seen that the ML code obtained by the mask is '1110010' and the code is phase shifted by two compared to the original ML code '1011100'.

5 is a circuit diagram of one embodiment of a gold code generator according to the present invention.

The gold code generator according to the present invention has two rth order linear feedback shift registers, two exclusive AND gates and r AND gates.

The output data and mask value of each stage of the second linear feedback shift register 2 are ANDed and output using AND gates 11 to 1r. Each bit value output from the AND gates 11 to 1r is output by performing an exclusive OR operation using the exclusive OR gate 3, and outputting the output of the exclusive OR gate 3 and the output of the first linear feedback shift register. An exclusive OR operation is performed using the exclusive OR gate 4 to generate a gold sign.

The gold code generator according to the present invention generates a different gold code while changing only the mask value while generating the initial value of the generated polynomial and the two feedback registers indicating the feedback connection position. Therefore, in a gold code generator having such a structure, when a conversion from an arbitrary phase to another gold code is required, unlike the prior art described with reference to FIG. 2, instead of setting an initial value of the shift register differently, the value of the same internal shift register is By allowing it to proceed as it is and changing only the mask value, it can be converted immediately to another gold sign while maintaining the phase in any phase. That is, the value of the internal shift register And Can be immediately converted to another gold code at any phase by setting it once and then proceeding and changing the mask only when the sign needs to be converted.

6 is a flowchart illustrating a code search process using a gold code generator using a mask according to the present invention.

When changing the sign of the local generator, it waits until the start point of the sign (61), sets the sign initial value (62), and then obtains the sign correlation value (63). It is then determined if all signs have been searched (64), and if all signs have been searched, the process ends, otherwise the mask is transformed (65), i. After that, the process is repeated again from step 63, that is, from the step of obtaining a sign correlation value. The correlation value of all codes is compared and the code having the largest correlation value among them is determined as the code that matches the code used for transmission.

Since a gold code generator using a mask can be immediately converted to another code without any state information, the code can be converted without waiting to the start point of the code in the code search process.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

As described above, the present invention can immediately convert to another code without any additional state information in the code search process, thereby significantly reducing the overall code search time.

Claims (3)

In the code generator for generating a gold code, First and second r-order (where r is a natural number) linear feedback shifting means for linear feedback shifting of predetermined data; A plurality of AND operations means for performing an AND operation on the data output from each stage of the second r-th order linear feedback shifting means and the r-bit mask data input from the outside; First exclusive OR calculation means for performing an exclusive OR on the r-bit data output from the AND product; And Second exclusive OR operation means for performing an exclusive OR operation on the data output from the first r-th order linear feedback shift register and the output of the first exclusive OR operation means; Gold code generator using a mask comprising a. The method of claim 1, Gold code generator using a mask, characterized in that by changing only the mask value can be converted to another gold code. In the code search method using a gold code generator, A first step of setting an initial value by waiting until a start point of the sign; Obtaining a correlation value of a sign; And Determining whether all the symbols have been searched, and if the search of all the symbols has been completed, the process is terminated, and if the search is not completed, converting the mask to another Gold symbol and repeating from the second step Code search method comprising a.