KR100705925B1 - Lars code division multiple access spreading method - Google Patents

Abstract

The present invention relates to an orthogonal spreading method used in LAS-CDMA (Code Division Multiple Access), in particular, to improve the performance by improving the spreading method, by generating a new LS orthogonal spreading code and applying to the improved spreading method The present invention relates to a LAS-CDMA spreading method for reducing peak-to-average power ratio (PAPR).

L개의 0을 삽입하는 단계를 포함하여 실행된다.In the present invention, selecting the desired code length N other than the spreading codes LS _I and LS _Q ; Generating an LS code having a length k = 4 as an initial value; Generating a new LS code by comparing the length k of the generated LS code with N / 2; 2 for generating an interference cancellation window at the front, middle or back of the new code having the generated length N

And inserting L zeros.

Therefore, according to the present invention, by applying a new spreading code to complex spreading, it is possible to stably reduce the peak power-to-average power ratio distribution within a range satisfactory.

Spread Code, Power Unbalance, CDMA

Description

Lars code division multiple access spreading method {LAS-CDMA Spreading Method}

1 is a diffusion block diagram used in a conventional LAS-CDMA.

2 is a diagram illustrating a binary phase shift keying (BPSK) spreading scheme using an LS code

3 is a QPSK spreading scheme using LS code

4 is a complex diffusion scheme of complex diffusion using an LS code

5 is a QPSK spreading scheme for generating a newly proposed LS code.

6 is a phase shift diagram for explaining in more detail the contents of the new LS code proposed by the method of FIG.

FIG. 7 is another spreading scheme in which the new LS code generated by FIG. 5 is applied to the complex spreading scheme of FIG.

8 is a flowchart of an embodiment using FIG. 7 to spread the band while reducing the peak-to-average power ratio.

The present invention relates to an orthogonal spreading method used in LAS-CDMA (Code Division Multiple Access), in particular, to improve the performance by improving the spreading method, by generating a new LS orthogonal spreading code and applying to the improved spreading method. The present invention relates to a LAS-CDMA spreading method for reducing the peak-to-average power ratio (PAPR).

More specifically, the present invention provides a performance using a quadrature phase shift keying (QPSK) spreading scheme in which different spreading codes are allocated to I (Inphase) components, which are in-phase components, and Q (Quadrature) components, which are quadrature components, respectively. LAS-CDMA spreading method to reduce the peak power-to-average power ratio by improving the power efficiency, solving the power imbalance between I and Q components using the complex spreading method, and applying the newly generated spreading code to the complex spreading method. It is about.

In general, the basic concept of the spread spectrum technology used by the CDMA method is to spread a signal transmitted through a coding process over a wideband, and then to despread it to a narrow band through a reverse coding process to detect a desired signal. At this time, through spreading and despreading, the desired signal is restored to the original narrowband signal having a high power, but other user's signals act like a low power broadband noise signal.

The characteristics of autocorrelation and crosscorrelation required for the spreading code used in the spreading and despreading process are as follows. In order to detect the desired signal, autocorrelation should have a maximum value when there is no time offset and a small value at other time differences. In addition, a small cross-correlation value is obtained at every time difference to distinguish it from spreading codes used by other users.                         

In order to satisfy the above autocorrelation and cross-correlation characteristics, the conventional CDMA method uses a PN (Pseudo Noise) code and a Walsh code as a spreading code. The above PN code satisfies the requirements of autocorrelation, and the Walsh code satisfies the requirements of cross-correlation.

In the cross-correlation requirement, there is no interference between spreading codes assigned to multiple users in the case of one channel path, but interference between spreading codes exists in the case of multiple channel paths. More specifically as follows.

In the case of one channel path, the amount of mutual interference between spreading codes is determined only by the correlation value when there is no time difference. On the other hand, in the case of multiple channel paths, the amount of mutual interference between spreading codes is influenced not only by the cross-correlation value when there is no time difference, but also by the cross-correlation value having path delay times between the channel paths. Will receive.

Therefore, in a multipath channel environment having a plurality of channel paths, which are generally referred to as actual channel environments, not only does the cross-correlation property between spreading codes have no time difference, but also the cross-correlation values at different time differences are important. .

After all, ideally, the cross-correlation value of the spreading code should have a value of zero for every time difference. However, a code that satisfies both the above-mentioned cross-correlation characteristics and the required characteristics of the above-described autocorrelation at a time is not known at present.

That is, looking at the PN code and Walsh code used in the conventional CDMA method, the PN code satisfies the requirements of autocorrelation but does not satisfy the requirements of cross-correlation. Also, Walsh code does not satisfy the requirements of autocorrelation and only partially meets the requirements of cross-correlation.

In other words, the cross-correlation property of Walsh code has a zero correlation value when there is no time difference, but a non-zero correlation value when the time difference is not zero.

On the other hand, the LS code completely satisfies the autocorrelation and cross-correlation requirement characteristics in a certain time difference section.

A time difference section in which the autocorrelation and cross-correlation characteristics are perfect is defined as an interference free window (IFW).

Looking at the autocorrelation characteristics in the interference cancellation window, when there is no time difference, the autocorrelation value is the maximum value, and the autocorrelation value is 0 even when the time difference is any time difference in the non-interference removal window.

That is, when the time difference is limited to only the interval of the interference cancellation window, the autocorrelation value when the time difference is zero has a maximum value, and when the time difference is not zero, the autocorrelation value becomes zero.

In addition, the cross-correlation property of the LS code has a cross-correlation value of zero even when the time difference is any time difference in the interference cancellation window.

As a result, in a multi-channel path environment, if the path delay time between each channel path exists in the interference cancellation window, interference between spreading codes assigned to each user can be eliminated. Therefore, the interval of time difference that satisfies the above autocorrelation and cross-correlation characteristics is called an interference cancellation window (IFW).

Conventionally, the PN code and Walsh code are used together to partially satisfy the autocorrelation and cross-correlation requirements, while the LS code uses only the LS code to completely satisfy the auto-correlation and cross-correlation requirements at time differences in the interference cancellation window. You will be satisfied.

Since the CDMA method using the LS code uses only the LS code as the spreading code, the spreading method is also different from the spreading method using the Walsh code and the PN code simultaneously. Therefore, the present invention proposes an improvement of the spreading method when the LS code is used as the spreading code.

Hereinafter, a diffusion scheme used in the conventional LAS-CDMA will be described with reference to the drawings.

1 is a diffusion block diagram used in a conventional LAS-CDMA.

After the control signal and the information signal 11 are divided into I and Q components, they are spread 12 using the LS code. The signal spread through the LS code passes through a time division multiplexer (TDM) 13 which is time division multiplexed through an LA code used to distinguish each base station. A filter 14 for filtering the signal output from the TDM, a multiplier 15 for multiplying the signal filtered by the filter with a predetermined signal, and an adder 16 for adding the multiplied signal and transmitting an output signal. The signal is transmitted via.

Referring to the operation of the block diagram of Figure 1 as follows. The control signal and the information signal including the information are divided into I / Q components. The I / Q component is spread by the LS code to spread the band. The I / Q component signal spread by the LS code passes through the TDM 13 to the output. A LA code (code) is applied to the TDM to distinguish a base station.

The I / Q component signal output from the TDM is passed through a filter and specified only by a signal, and is input to a multiplier. The input signal multiplies the SIN value and the COS value, which are carrier signals.

The signal output from the multiplier is input to the adder to become a transmission signal and transmitted through the actual channel.

2 is a BPSK (Binary Phase Shift Keying) spreading method using an LS code, and the same LS code is allocated to the I component and the Q component to spread.

The operation of FIG. 2 will be described.

First, the code used in LAS-CDMA uses LS code, not Walsh code or PN code, which is used in general CDMA. Currently, only LS codes having lengths of 16, 32, 64, and 128 are known.

Since only the LS code is used for direct diffusion, all interferences other than the magnetic signal entering the interference cancellation window are removed.

Conventionally, the same LS code is applied to the I component and the Q component of the spread signal of FIG.

Therefore, the spread signals d _I and d _Q are multiplied by the same LS _I code to output the spread X _I and X _Q signals.

However, the BPSK spreading scheme is weaker in channel prediction error than the QPSK spreading scheme in which different codes are used for I and Q components, which are codes required for orthogonal spreading, and thus performance is degraded.

Therefore, in order to solve the above problems, the present invention provides a QPSK spreading method using a method of assigning different LS codes to I and Q components required for orthogonal spreading, and also power imbalance between I and Q components. In order to reduce the complexity, we propose a complex spreading method, and also propose a new LS code generation method and a complex spreading method using the method.

L개의 0을 삽입하는 단계를 포함하는 것을 특징으로 한다.A method for spreading multiple code division multiple access according to the present invention comprises the steps of selecting a desired code length N other than the zero of the spreading codes LS _I and LS _Q ; Generating an LS code having a length k = 4 as an initial value; Generating a new LS code by comparing the length k of the generated LS code with N / 2; 2 for generating an interference cancellation window at the front, middle or back of the new code having the generated length N

And inserting L zeros.

L_GUARD의 LS코드의 간섭제거창=[-L_IFW, L_IFW]의 구간동안 서로 직교인 LS코드의 개수는, 2^g-1

L_IFW

2^g일때 2^m-g로 생성되는것을 특징으로 한다.In addition, in the lath code division multiple access spreading method of the present invention, the code length N (= 2 ^m ) + 2

Interference cancellation window of LS code of L _GUARD = [-L _IFW , L _IFW ] The number of orthogonal LS codes is 2 ^g-1

L _IFW

It is characterized in that produced 2 ^mg when 2 ^g .

In the Lath Code Division Multiple Access spreading method of the present invention, when an LS code of a length N of a nonzero portion is used as a spreading code, an LS component having a length N / 2 of a nonzero portion is selected and then an I component LS is used. _I LS code is multiplied by the code extension E _I, characterized in that, which is multiplied by the extension code, the E _Q Q component _Q LS LS code.

In the Lars code division multiple access spreading method of the present invention, the generated codes are selected by orthogonal codes in ascending order of code numbers, and then applied to a spreading method in ascending order to code numbers of an orthogonal code set.

2인 자연수이며, L_GUARD와 L_IFW는 L_GUARD

L_IFW

0인 정수이며, 직교 코드인 I성분 확산코드와 Q성분 확산코드들간에 180⁰ 위상천이가 최소로 일어나도록 하기 위해, (I성분 확산코드, Q성분 확산코드) or (Q성분 확산코드,I성분 확산코드)으로 조합하는 것을 특징으로 한다.In the lath code division multiple access spreading method of the present invention, g is a natural number and m is

Natural number of two, L _GUARD and L _IFW are L _GUARD

L _IFW

(I component spreading code, Q component spreading code) or (Q component spreading code, I) in order to minimize the 180 ⁰ phase shift between the I component spreading code and the Q component spreading code, which is an integer of 0, and the orthogonal code Component diffusion code).

LS_I)-(d_Q

LS_Q))+ j((d_Q

LS_I)+(d_I

LS_Q))인 출력신호를 생성하여 전력의 불균형을 개선하는 것을 특징으로 한다.Also, in the lath code division multiple access spreading method of the present invention, each of the I / Q component input signals d _I and d _Q is multiplied by applying LS _I and LS _Q , which are I / Q component spreading codes, and the output spread signal. Intersect and enter into the adder X _I + jX _Q = ((d _I

LS _I )-(d _Q

LS _Q )) + j ((d _Q

LS _I ) + (d _I

LS _Q )) to generate an output signal to improve the power imbalance.

In addition, the lath code division multiple access spreading method of the present invention multiplies an LS code having a length N / 2 of a non-zero portion by an extension code having a length of 2, and generates a new LS code having a length N of a nonzero portion (LS ^* _{I, N} and LS ^* _{Q, N} ).

k 와 2

k+1이 되며 시간차가 +1,-1일 때만 직교성이 성립하지 않는 것을 특징으로 한다.In addition, in the Lath code division multiple access spreading method of the present invention, in the orthogonal code set A of the LS code of length N / 2 of the non-zero portion, the code number k is multiplied by the extension code of E _I and E _Q and then code number 2

k and 2

k + 1 and the orthogonality does not hold only when the time difference is + 1, -1.

LS^* _I,N)-(d_Q

LS^* _Q,N))+ j((d_Q

LS^* _I,N)+(d_I

LS^* _Q,N))인 출력신호가 되는것을 특징으로 한다.In addition, the lath code division multiple access spreading method of the present invention multiplies each of the I / Q component input signals d _I and d _Q by applying LS ^* _{I, N} and LS ^* _{Q, N} which are I / Q component spreading codes. When crossing the output spread signal and inputting to the adder, X _I + jX _Q = ((d _I

LS ^* _{I, N} )-(d _Q

LS ^* _{Q, N} )) + j ((d _Q

LS ^* _{I, N} ) + (d _I

LS ^* _{Q, N} )) to be an output signal.

Hereinafter, a method for spreading LAS-code division multiple access according to the present invention will be described with reference to the accompanying drawings.

3 is a QPSK spreading method using an LS code, and a separate code LS _I code and LS _Q code are allocated to I component and Q component in each channel to output spread signals X _I and X _Q.

The LS _I code and LS _Q code may be generated and allocated in various ways, but the present invention uses the following method.

L_GUARD의 LS코드의 간섭제거창=[-L_IFW, L_IFW]의 구간동안 서로 직교인 LS코드의 개수는, 2^g-1

L_IFW

2^g일때 2^m-g이다. (단 g는 자연수이고, m은

2인 자연수이며, L_GUARD와 L_IFW는 L_GUARD

L_IFW

0인 정수임).Cord length N (= 2 ^m ) +2

Interference cancellation window of LS code of L _GUARD = [-L _IFW , L _IFW ] The number of orthogonal LS codes is 2 ^g-1

L _IFW

2 when ^g is 2 ^mg. Where g is a natural number and m is

Natural number of two, L _GUARD and L _IFW are L _GUARD

L _IFW

Is an integer of zero).

The codes generated by the above are selected by orthogonal codes in ascending order of code numbers, and corresponded in ascending order to code numbers of orthogonal code sets.

When the orthogonal code set is L = (LS ₀ , LS ₁ , ..., LS ₂ (mg-2), LS ₂ (mg-1)), the I component spreading code and the Q component spreading code are 180 ^We propose a combination of ^zero phase shifts as follows.

(I component spreading code, Q component spreading code) or (Q component spreading code, I component spreading code)

= (LS ₀ , LS ₂ (mg-1)), (LS ₁ , LS ₂ (mg-1) ₊₁ ), ..., (LS ₂ (mg-1) _-1, LS ₂ (mg-1) ))to be.

4 is a complex diffusion method of complex diffusion using an LS code.

As shown in the figure, each channel allocates different LS codes to the I component and the Q component to spread, and the multiplying method spreads by a complex product rather than a simple real product.

By using the complex diffusion method, the power imbalance problem is solved when the power ratio of the input signal of the I component and the Q component is not constant while maintaining the advantages of using the QPSK diffusion method of FIG. 3. The powers of the I and Q components are distributed to be equal to each other.

That is, each of the I / Q component input signals d _I and d _Q is multiplied by applying the I / Q component spread codes LS _I and LS _Q , and the output spread signal is crossed and input to the adder, where X is a spread signal. Outputs _I and X _Q signals.

LS_I)-(d_Q

LS_Q))+ j((d_Q

LS_I)+(d_I

LS_Q))와 같이 된다. 결국 I/Q성분 입력신호인 d_I와 d_Q가 I/Q성분 양쪽의 출력신호에 영향을 끼치게 되므로 입력신호의 전력이 출력신호의 I/Q성분 양쪽으로 분배되게 된다. 즉, 입력신호의 전력 불균형을 해결하여, I/Q성분 양쪽의 출력신호의 전력이 같아지도록 한다.Therefore, I / Q component output signal through complex multiplier and adder is X _I + jX _Q = ((d _I

LS _I )-(d _Q

LS _Q )) + j ((d _Q

LS _I ) + (d _I

LS _Q )). As a result, the I / Q component input signals d _I and d _Q affect the output signals of both the I / Q components, so that the power of the input signal is distributed to both the I / Q components of the output signal. In other words, the power imbalance of the input signal is solved so that the power of the output signal of both the I / Q components becomes equal.

5 is a method for generating a newly proposed LS code. When spreading by assigning different LS codes to the I and Q components as in the QPSK spreading scheme of FIG. 3 or the complex spreading scheme of FIG. 4, the spreading code of the I component and the spreading code of the Q component are simultaneously changed. As such, the phase shift of the spread signal may be 180 ⁰ .

This 180 degree phase shift adversely affects the envelope deviation of the signal after the spread signal passes through the filter. That is, the peak-to-average power ratio value is increased.

In order to reduce the peak-to-average power ratio, it is necessary to minimize the number of times that the spreading code of the I component and the spreading code of the Q component are simultaneously changed.

In order to artificially prevent the I component and the Q component from changing at the same time, Offset QPSK which has a half chip delayed Q component is proposed, but Offset QPSK is a multi-code or multi-channel. rather, the value of peak-to-average power ratio is increased.

In order to solve the above problems, a new LS code as shown in FIG. 5 is proposed and spread.

If a non-zero LS code of length N is used as the spreading code, first select an LS code of length N / 2 of the non-zero portion, and then specify an extension code E _I for each I component LS code LS _I. multiplying, in the extension multiplied by the code E _Q Q component _Q LS LS code.

An extension code is a code of length 2 that has the values E _I = (1,1) or (-1, -1) and E _Q = (1, -1) or (-1,1).

Since the LS code having the length N / 2 of the non-zero portion is multiplied by the extension code having the length 2, the code of the non-zero portion of the total length is N code.

The new LS codes of length N (LS ^* _{I, N} and LS ^* _{Q, N} ) created in this way will not necessarily have 180 degrees of phase shift at least half of the total code length.

Therefore, there is an effect of reducing the value of the peak power to the average power ratio.

For example, if the interference cancellation window = [-3,3] non-zero length N = 128 of the existing LS code to look at the characteristics first, can be used as the orthogonal code code code {0,1, 2, ... 31}. At this time, the autocorrelation property of each code of the orthogonal code set has a maximum value N = 128 when the time difference is 0, and becomes 0 at another time difference in the interference cancellation window. In addition, the cross-correlation property between the codes has a property of becoming zero in the time difference in the interference cancellation window.

To examine the characteristics of the new LS code, create a new LS code of length 128 as follows: First, choose an orthogonal code set from among N / 2 = 64 LS codes, which is half the code length of the desired non-zero part, and the code number A = {0,1,2, ... 15} and the extension code for each code. Multiplying E _I = (1,1) and E _Q = (1, -1) multiplies the number of elements in the orthogonal code set by two, so that the orthogonal code set is code number A ^* = (0,1,2, ... 31}. Among the generated codes, the autocorrelation property of the even code number is 1/2 of the maximum value when the time difference = + 1, -1, unlike the existing LS code. Also, the autocorrelation property of the odd code number has a value of -1/2 of the maximum value when time difference = + 1, -1.

k

15인 정수)에 E_I와 E_Q의 확장 코드를 곱하면 코드 번호 2

k 와 2

k+1이 되고 이 둘은 원래 같은 코드에서 확장된 코드이므로, 시간차가 +1,-1일 때만 직교성이 성립하지 않게 된다. On the other hand, code number k in the orthogonal code set A of the existing LS code of length N / 2 of the non-zero portion, where k is 0

k

Multiplying _{I I} and E _{Q by} the extension code

k and 2

Since k + 1 and these two are originally extended from the same code, orthogonality does not hold only when the time difference is + 1, -1.

However, orthogonality is completely established at time differences other than + 1, -1 in the interference cancellation window.

For example, the codes of orthogonal code numbers 0 and 1 of the new LS code are completely orthogonal as they are generated by multiplying the extension codes E _I and E _Q by the code of the existing LS code number 0 of the non-zero length 64. It does not have a property.

In addition, the new LS code has the advantage of increasing the interference cancellation window. The existing LS code has the interference cancellation window = [-3, 3], while the new LS code has the interference cancellation window = [-4, 4].

FIG. 6 illustrates the contents of the new LS code proposed by the method of FIG. 5 in more detail. When the LS ^* _{I, N} and LS ^* _{Q, N} signals spread by the multiplier are changed by 180 degrees, the peak power band is shown. The average power ratio value becomes large.

That is, when the I and Q values of the first quadrant transition to the third quadrant in the coordinates composed of the I component and the Q component, the phase change is changed by 180 degrees, thereby increasing the peak-to-average power ratio.

In addition, there is a 180 degree phase shift when transitioning from the second quadrant to the fourth quadrant.

Therefore, since the peak power-to-average power ratio can be reduced only by reducing the case where the phase shift is 180 degrees, the number of times of the 180 degree phase shift can be reduced by applying the new LS code method of FIG. 5.

For example, the LS _{I, N / 2} value is (1,1,1, -1), the LS _{Q, N / 2} value is (1,1, -1,1), and the E _I value is (1,1 ) And the E _Q value is (1, -1), the LS ^* _{I, N} value output by the multiplier becomes (1,1, 1,1, 1,1, -1, -1) and LS ^{* The} _{Q and N} values are (1, -1, 1, -1, -1,1, 1, -1).

The LS ^* _{I, N} and LS ^* _{Q, N} values simultaneously change, that is, there is no 180 degree phase change.

FIG. 7 is another spreading scheme in which the new LS code generated by FIG. 5 is applied to the complex spreading scheme of FIG. 4.

As shown in the figure, the LS code generated by the method of FIG. 5 is allocated to the I component and the Q component in each channel, and the spreading is performed by multiplying the complex number instead of the simple real product.

By using the complex diffusion method, the power imbalance problem is solved when the power ratio of the input signal of the I component and the Q component is not constant while maintaining the advantages of using the QPSK diffusion method of FIG. 3. The powers of the output signals of the I component and the Q component are distributed to be equal to each other.

That is, each of the I / Q component input signals d _I and d _Q is multiplied by applying the I / Q component spread codes LS ^* _{I, N} and LS ^* _{Q, N} , and the output signals are crossed to the adder. Inputs X _I and X _Q signals, which are spread signals.

LS^* _I,N)-(d_Q

LS^* _Q,N))+ j((d_Q

LS^* _I,N)+(d_I

LS^* _Q,N))와 같이 된다. 결국 I/Q성분 입력신호인 d_I와 d_q가 I/Q성분 양쪽의 출력신호에 영향을 끼치게 되므로 입력신호의 전력이 출력신호의 I/Q성분 양쪽으로 분배되게 된다. 즉, 입력신호의 전력 불균형을 해결하여, I/Q성분 양쪽의 출력신호의 전력이 같아지도록 한다.Therefore, I / Q component output signal through complex multiplier and adder is X _I + jX _Q = ((d _I

LS ^* _{I, N} )-(d _Q

LS ^* _{Q, N} )) + j ((d _Q

LS ^* _{I, N} ) + (d _I

LS ^* _{Q, N} )). As a result, the I / Q component input signals d _I and d _q affect the output signals of both I / Q components, so that the power of the input signal is distributed to both I / Q components of the output signal. In other words, the power imbalance of the input signal is solved so that the power of the output signal of both I / Q components is equal.

FIG. 8 is a flowchart of an embodiment using FIG. 7 to spread the band while reducing the peak-to-average power ratio.

First, the user selects a desired code length other than 0 of LS _I and LS _Q of FIG. 7. However, the code length N has a value of 2 ^m and m is a natural number of 3 or more. (Step 81).

The reason why m is 3 or more is that the length of the original LS code starts at 4, where the new LS code is generated by multiplying the existing LS code by the extension code of length 2.

Therefore, the minimum length of the new LS code is eight.

As an initial value, an LS code having a length of k = 4 is generated. (Step 82).

If the length k of the generated LS code is smaller than N / 2, an LS code having a length of 2k, which is twice the length, is generated again. That is, since the initial value is an LS code having a length k = 4, the length k of the next generated LS code is 8, 16, 32, 64, ... (step 87).

In this manner, generation of the LS code is repeated until the length k of the LS code becomes N / 2 (steps 83 and 87).

When the LS code of length N / 2 is generated, the length L of the zero component and the value selected from the extension codes E _I and E _Q values are selected, and the length N length is multiplied by the LS code of length N / 2 and the extension code of length 2. Generate a new LS code (steps 83, 84, 85, 86).

The number of 180-degree phase shifts can be reduced to at least half only by multiplying an extension cord having a length of 2.

L개의 0을 삽입한다.(단계 88).2 for generating an interference cancellation window at the front, middle or back of the new code having the length N generated in step 84.

L zeros are inserted (step 88).

As described above, in the present invention, a new spreading code is generated and applied to the complex spreading scheme in order to improve the spreading scheme to improve performance and to reduce the peak-to-average power ratio. In order to be insensitive to channel prediction error, each channel is spread by assigning different LS codes to I and Q components, and solve the power imbalance caused when the power of I and Q components is not constant. To do this, spread by the product of complex numbers.

In addition, the 180-degree phase shift between codes increases the peak-to-average power ratio, so that a new code is generated and applied to the complex diffusion method to reduce the frequency of the 180-degree phase difference. Try to minimize the number of times.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. That is, the LS code spreading method, the new LS code generation and the new LS code spreading method can be generated and applied to the present invention in various ways.

Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

In the present invention, in general, in the current LAS-CDMA, only the LS code which is an orthogonal code is used, and the same LS code is used for the I component and the Q component. This results in performance degradation, power imbalance caused when the power of I and Q components are not constant, and peak power-to-average power ratio caused by 180-degree phase shift between codes. By applying to complex diffusion, it is possible to stably reduce the distribution of maximum power to peak power to average power ratio within a satisfactory range.

Claims (13)

In the QPSK spreading method in which LS _I codes and LS _Q codes, which are separate codes, are allocated to the I and Q components of each channel, in order to spread the band by reducing the peak-to-average power ratio, Selecting a non-zero desired code length N of spreading codes LS _I and LS _Q ; Generating an LS code having a length k = 4 as an initial value; Generating a new LS code by comparing the length k of the generated LS code with N / 2; 2 for generating an interference cancellation window at the front, middle or back of the new code having the generated length N

And inserting zeros into the L code division multiple access spreading method. The method according to claim 1, wherein when the length k and N / 2 are compared and the k is small, the LS code having a length of 2k, which is twice the length, is generated again. 2. The LS code of claim 1, wherein when the LS code having the length N / 2 is generated, the value L selected from the extension codes E _I and E _Q values and the length L of the zero component are selected, and the LS code having the length N / 2 and the length 2 are selected. And a new LS code having a length N by multiplying the codes. delete delete delete delete delete delete delete delete delete delete

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