KR100768103B1 - Apparatus and Method for Sample Timing Tracking in the Wireless Pico Cell Communication Systems - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus and method for tracking sample timing in a wireless picocell communication system of direct sequence spread spectrum.

2. The technical problem to be solved by the invention

According to the present invention, a timing error is detected after extracting a cross-correlation function value by using an early signal and a late signal based on a signal sampled at a current gate. To provide a sample timing tracking device and method in a direct sequence spread spectrum wireless picocell communication system for adjusting a sample timing point once every N (natural number) cumulative times after stabilizing and normalizing an error. In this.

3. Summary of Solution to Invention

The present invention relates to a sample timing tracking apparatus in a wireless picocell communication system of a direct sequence spread spectrum method, wherein -1 / Ns (Ns is any natural number) based on a signal sampled at a current gate (On-time). Cross-correlation function extracted by using early signal with chip offset and late signal with + 1 / Ns chip offset and then through early gate Timing error detection means for detecting a difference between the magnitude squared of the value and the squared magnitude of the cross-correlation function value extracted through the late gate as a timing error; Filtering means for stabilizing the timing error detected by the timing error detecting means; Normalization means for normalizing the timing error stabilized by the filtering means; Sample timing adjustment control means for controlling to adjust a sample timing point once every N (natural numbers) cumulative times using a stabilized (average) timing error normalized by the normalization means; And interpolation means for adjusting a sample timing point according to the control of the sampling timing adjustment control means.

4. Important uses of the invention

The invention is used for sample timing tracking and the like.

Sample Timing Tracking, Early Gate, Current Gate, Late Gate, Stabilize, Normalize, Timing Error

Description

Apparatus and Method for Sample Timing Tracking in the Wireless Pico Cell Communication Systems}

1 is a configuration diagram of an embodiment of a wireless picocell communication system of a direct sequence spread spectrum method to which the present invention is applied;

FIG. 2 is a block diagram of a sample timing tracking device in a wireless picocell communication system using a direct sequence spread spectrum method according to the present invention;

3 is a diagram illustrating an embodiment of a timing error detection process according to the present invention;

4 is an exemplary explanatory diagram of a sample timing adjustment control process according to the present invention;

5 is an example of the sawtooth function SAW (x) of period 1 used in the present invention;

6 is a diagram illustrating an exemplary performance analysis of a sample timing tracking device in a wireless picocell communication system using a direct sequence spread spectrum method according to the present invention.

* Explanation of symbols for the main parts of the drawings

21: timing error detector 22: filter

23: Normalizer 24: Sample Timing Control Controller

25: interpolator

The present invention relates to an apparatus and method for tracking a sample timing in a wireless picocell communication system of a direct sequence spread spectrum method. More particularly, the present invention relates to a sampling timing error caused by sampling frequency instability, and to demodulation of a received symbol. An apparatus and method for tracking sample timing in a wireless picocell communication system of direct sequence spread spectrum for maintaining sampling timing at an accurate position.

In general, the Direct Sequence Spread Spectrum (DSSS) method refers to a method of communicating by spreading one signal symbol in a predetermined sequence.

That is, when a transmitter inputs a signal to be transmitted to a pseudo-random noise sequence, acquires a spread spectrum signal having a low power density per frequency, and transmits the same to the receiver, the receiver receives the same pseudo noise sequence. To reproduce the original signal.

This direct sequence spreading scheme has advantages of good modulation efficiency, fast signal synchronization, and low in-band interference due to low power density, which has been used in the code division multiple access (CDMA) technique. It is also used in Zigbee communication.

Although the transmitter and the receiver of the wireless picocell system to which the direct sequence spreading scheme is applied operate as an oscillator having the same frequency, inconsistency in the sampling time occurs due to the frequency instability of the oscillator during the actual transmission and reception process.

As a result, the receiver generates an error in sample timing, which leads to degradation of the symbol demodulation process. In other words, an error in sample timing causes a decrease in signal to noise ratio (SNR), thereby degrading the performance of the wireless picocell system.

Accordingly, there is a demand for a method for correcting a sampling phase error that may occur due to such sampling frequency instability and maintaining a sampling operation at an accurate position (maintaining sample timing) when demodulating a received symbol.

The present invention has been proposed to meet the above requirements, and based on the signal sampled at the current gate (On-time), the timing after extracting the cross-correlation function value using an early signal and a late signal Sample timing tracking in a direct sequence spread spectrum wireless picocell communication system for detecting an error, adjusting and normalizing the detected timing error, and then adjusting a sample timing point every N (natural numbers) cumulative number of times. It is an object of the present invention to provide an apparatus and a method thereof.

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.

An apparatus of the present invention for achieving the above object is a sample timing tracking device in a wireless picocell communication system of the direct sequence spread spectrum method, based on a signal sampled at the current gate (On-time), -1 / Ns (Ns is an arbitrary natural number) After extracting the cross-correlation function value by using an early signal having a chip offset and a late signal having a + 1 / Ns chip offset, the initial gate (Early) is extracted. timing error detecting means for detecting a difference between the magnitude squared of the cross-correlation function value extracted through the gate and the magnitude squared value of the cross-correlation function value extracted through the late gate as a timing error; Filtering means for stabilizing the timing error detected by the timing error detecting means; Normalization means for normalizing the timing error stabilized by the filtering means; Sample timing adjustment control means for controlling to adjust a sample timing point once every N (natural numbers) cumulative times using a stabilized (average) timing error normalized by the normalization means; And interpolation means for adjusting a sample timing point according to the control of the sampling timing adjustment control means.

On the other hand, the method of the present invention, in the sampling timing tracking method in the sample timing tracking device, -1 / Ns (Ns is a natural number) chip offset based on the signal sampled at the current gate (On-time) After extracting the cross-correlation function value by using the early signal with) and the late signal with + 1 / Ns chip offset, the square of the magnitude of the cross-correlation function value extracted through the early gate Detecting a difference in magnitude squared values of the cross-correlation function values extracted through a late gate as a timing error; Stabilizing the detected timing error; Normalizing the stabilized timing error; And a sample timing adjustment step of adjusting a sample timing point once every N (natural number) accumulation times using the normalized stabilized (average) timing error.

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 configuration diagram of an embodiment of a wireless picocell communication system of a direct sequence spread spectrum method to which the present invention is applied.

First, the phase tracking device 11 removes an error that may occur due to a surplus frequency error, and performs a function of maintaining the minimized frequency error no longer increasing through a channel coefficient estimation algorithm.

That is, the phase estimator 11 detects a phase error of the received signal by applying a phase shift value to a symbol extracted by using the despreading code value and the cross-correlation function value of the received signal, and detects the phase error of the received signal. The output is adjusted to a loop gain to obtain a loop output for the next symbol and then adjusted to a range of phase levels, to compensate for the phase error by reducing the excess frequency offset of the adjusted loop output.

In addition, an equalizer (DFE: Decision Feedback Equalizer) 12 despreads the received signal and extracts a symbol.

In addition, the Channel Matched Filter (CMF) 13 minimizes the influence of signal interference by the channel.

In addition, Sample Time Tracking 14 corrects sampling phase errors caused by sampling frequency instability, and maintains sampling operation at the correct position during demodulation of received symbols (sample timing).

2 is a block diagram illustrating an example of a sample timing tracking apparatus in a wireless picocell communication system using a direct sequence spread spectrum method according to the present invention.

First, the timing error detector 21 extracts a cross-correlation function value through three gates (Early, On-time, and Late). That is, an early signal having a -1 / Ns (Ns is any natural number) chip offset based on a signal sampled at the current gate (On-time), and a + 1 / Ns chip offset. By using a late signal having a) () the cross-correlation function value shown in Equation 1 below.

은 최적 샘플 지점을 기준으로 -1/Ns 칩옵셋에서의 수신신호(Early gate)를 의미하며,

은 +1/Ns 칩옵셋에서의 수신신호(Late gate)를 의미하고, C(i)는 11-칩 바커 코드(11-chip Barker code) 중 하나의 비트 또는 코드값을 의미한다.
또한,

은 코드워드 길이(L) 단위의 심벌 타이밍을 의미하고,

는 수신단 칩(chip) 단위의 샘플링 타임 k에 수신된 수신신호를 의미한다.Here, L means the length of the codeword (codeword),

Means an early gate at -1 / Ns chip offset based on the optimal sample point,

Denotes a receive gate at a + 1 / Ns chip offset, and C (i) denotes a bit or code value of one of the 11-chip Barker codes.
Also,

Denotes symbol timing in units of codeword length (L),

Denotes a received signal received at a sampling time k in a receiver chip unit.

In this case, when the preamble, header section, and data transmission rate of the received signal are 2M, the PSDU section is 11 since the 11-chip Barker code is generally applied to the PSDU (Presentation Service Data Unit) section. For M and 11M, the PSDU interval is eight.

Thereafter, the timing error detector 21 detects a timing error by using Equation 2 below, which is a cross-correlation function value extracted from each of the gates.

That is, the difference between the magnitude squared of the cross-correlation function value extracted through the early gate and the cross-correlation function value extracted through the late gate is detected as a timing error.

와

값은 최적의 샘플 지점에 대칭되는 동일 값으로 나타나게 되므로, 잡음 등의 영향이 없다면 상기 [수학식 2]의

값은 0이 된다. At this time, if the sample timing at the current gate is an optimal sample point (correct sample timing point),

Wow

The value is represented by the same value symmetrical to the optimal sample point, so if there is no influence of noise or the like, Equation 2

The value is zero.

값은 + 혹은 - 에 해당하는 어떤 값으로 나타나게 된다. However, if there is a timing error,

The value is represented by any value corresponding to + or-.

This timing error can be changed sensitively by the influence of noise, thereby stabilizing the timing error through the filter 22. This is the same as the following [Equation 3] to [Equation 5].

는 초기 샘플 지점(게이트)에서 추출한 상호상관 함수값을 의미하고,

는 현재 샘플 지점(게이트)에서 추출한 상호상관 함수값, 즉 심볼의 에너지를 의미하며,

는

의 평균값, 즉 현재 샘플 지점에서 추출한 상호상관 함수값의 평균값을 의미한다. Here, N means cumulative number of times for filtering,

Means the cross-correlation function value extracted from the initial sample point (gate),

Denotes the cross-correlation function value extracted from the current sample point (gate), that is, the energy of the symbol.

Is

Means the mean value of the cross-correlation function values extracted from the current sample point.

Thereafter, the normalizer 23 calculates a normalized average timing error as shown in [Equation 6] by using Equations 3 and 5 above.

Finally, the sample timing adjustment controller 24 adjusts the sample timing point once every N cumulative times using Equation 6 above.

)와 비교하여, (

< 샘플 타이밍 지점 <

)를 만족시키도록 샘플 타이밍 지점을 ±1/Ns(Ns는 임의의 자연수) 샘플씩 전진-지연 조절(Advance-retard control)을 수행한다. That is, the thresholds of + and-(

In comparison to

<Sample timing point <

Advance-retard control is performed for each sample timing point by ± 1 / Ns (where Ns is any natural number) samples.

값보다 크면, 현재 샘플 타이밍 지점이 최적 샘플 지점보다 빠르게 샘플링되고 있음을 의미하므로, 한 샘플을 지연시킨다(retard). 반면,

값보다 작은 "Ratio" 출력이 나타난다면, 현재 샘플 타이밍 지점이 최적 샘플 지점보다 느리게 샘플링되고 있음을 의미하므로, 한 샘플을 전진시킨다(advance).Therefore, the "Ratio" value of Equation 6 is

Larger than this value means that the current sample timing point is being sampled faster than the optimal sample point, thus retarding one sample. On the other hand,

If a "Ratio" output appears smaller than the value, it means that the current sample timing point is being sampled slower than the optimal sample point, thus advancing one sample.

)와 누적 회수 N에 의해 추적 성능이 좌우되는데, 높은 임계치 영역을 설정하게 되면 타이밍 에러에 둔감한 반응을 나타나게 되어 복조 성능을 저하시킨다.At this time, the sample timing tracking process is a threshold (

) And cumulative number N depend on tracking performance. Setting a high threshold region results in an insensitive response to timing error, which degrades demodulation performance.

On the other hand, as the cumulative number N is decreased, the timing response is faster, which degrades performance in an environment in which interference effects such as noise are high.

Hereinafter, the timing error detection principle of the timing error detector 21 will be described in more detail with reference to FIG. 3.

)은 하기의 [수학식 7]과 같다.In general, timing recovery should be made from the symbol rate of the severely distorted signal. That is, an algorithm for timing recovery is derived from the output of the matched filter. At this time, the output of the filter (

) Is as shown in Equation 7 below.

)는 하기의 [수학식 8]과 같이 표현할 수 있다.Here, the received signal whose phase is recovered (

) Can be expressed as Equation 8 below.

,

은 참값(알려지지 않은 값)이고

,

은 시도(측정) 값을 나타낸다. 그리고, 정확한 위상 값(

)을 알 수 있다고 가정한다. 즉,

를 가정한다.At this time, in [Equation 7] and [Equation 8]

,

Is the true value (unknown value)

,

Represents the trial (measure) value. And the exact phase value (

Assume that In other words,

Assume

)은 하기의 [수학식 9]와 같이 나타낼 수 있다.Then, the output of the filter (

) May be expressed as in Equation 9 below.

과 잡음 프로세스(

)는 하기의 [수학식 10]과 같이 정의한다.here,

And noise processes (

) Is defined as in Equation 10 below.

)에 가까운

값들만을 고려한다. At this time, the object of interest is an error feedback process (algorithm), so the true value (

Close to)

Only values are considered.

Therefore, in the "Data-aided timing" estimation, the "log-likehood" function for the samples of the "L-sample segment" may be defined as shown in Equation 11 below.

Subsequently, when all unnecessary items (objects of interest exclusion) are removed from Equation 11 for optimization, an objective function such as Equation 12 can be obtained.

에 대하여 미분하고,

를 대치시키면 에러(error) 신호를 얻을 수 있다. 이는 하기의 [수학식 13]과 같다.After that, Equation 12

Differentiate against,

Replace with to get an error signal. This is shown in Equation 13 below.

는 필터(Matched filter)의 출력으로

에서의

값은 무시될 수 있으므로, 상기 [수학식 13]의 첫 번째, 두 번째 항목은 무시할 수 있다. here,

Is the output of the matched filter

In

Since the value can be ignored, the first and second items of Equation 13 can be ignored.

)에 가까운

값들만을 고려하게 되어

로 근사화한다.And, since the object of interest is an error feedback algorithm, the true value (

Close to)

Only the values

To approximate

라고 할 때 L개의 샘플들에 대한 시간

에서의 에러 신호

는 하기의 [수학식 14]와 같이 정의할 수 있다.Meanwhile,

Is the time for L samples

Error signal at

May be defined as in Equation 14 below.

Here, Equation 14 is expressed in the following Equation 15 in the form of a matrix.

는 "skew symmetry" 성질을 가진다. 그리고, L=2에 대한 에러 신호(

)는 하기의 [수학식 16]과 같다.At this time, the matrix

Has a "skew symmetry" property. And, the error signal for L = 2 (

) Is as shown in Equation 16 below.

가 실수이고 "skew symmetry" 성질(

)을 가지므로, 상기 [수학식 16]을 하기의 [수학식 17]과 같이 단순화시킬 수 있다.On the other hand, when g (t) is a real function, the matrix

Is a real number and the "skew symmetry" property (

), The Equation 16 can be simplified as shown in Equation 17 below.

The derivation process of Equation 17 was first proposed by "Mueller" and "Muller".

라 하면 다항식 FIR 보간기는 하기의 [수학식 18]과 같이 n번째 탭 계수가

의 다항식 형태로 표시된다.On the other hand, the timing adjustment interpolator 25, for example, it is preferable to use a polynomial (Polynomial) FIR (Finite Impulse Response) form. At this time, the timing delay

The polynomial FIR interpolator has the n th tap coefficient as shown in [Equation 18].

In polynomial form.

At this time, since the interpolation should be performed at the center of the interval to maximize the accuracy, it is preferable to make the coefficient (number) of the interpolator 25 an even number.

)를 찾는다. Thereafter, an interpolator coefficient representing a second order error (Quadratic error) for a 2N order FIR filter, that is, minimizing [Equation 19] below (

Find).

는 이상적인 보간기의 주파수 특성을 나타낸다. Where |. | In

Denotes the frequency characteristics of an ideal interpolator.

을 최소화하는

은 하기의 [표 1] 내지 [표 8]과 같고, 몇 가지 M, N에 대하여

은 하기의 [표 9]와 같다. At this time, for various M, N

To minimize

Is the same as Table 1 to Table 8 below, and for some M, N

Is shown in Table 9 below.

As can be seen through this, in consideration of the performance and complexity of the interpolator 25, it is preferable to select N = 3, M = 2.

Meanwhile, the timing adjustment control process of the sample timing adjustment controller 24 will be described in more detail with reference to FIG. 4.

로 송신한다고 가정하면, 송신기에서 샘플들간 간격(

)이 정수일 때,

를 만족해야 한다. As shown in Fig. 4, the transmitter generates a signal having a symbol rate of 1 / T.

Suppose that the transmitter transmits the

) Is an integer,

Must be satisfied.

)이 송신기의 심볼률(1/T)의 정수 배가 아니므로, 송신기 샘플들의 시간간격(

)은 수신기의 시간간격(

)에 사상 되어야 한다. 이를 수학적으로 표현하면 하기의 [수학식 20]과 같다.At this time, the sampling rate of the receiver (

) Is not an integer multiple of the transmitter's symbol rate (1 / T),

) Is the time interval (

Should be mapped. This is expressed mathematically as shown in Equation 20 below.

와

의 관계와 기저 점(

)과 부분적인 지연(

)은 도 4에 도시된 바와 같다. 그리고,

는 내림을 나타낸다. here,

Wow

Relationship and base point

) And partial delay (

) Is as shown in FIG. 4. And,

Indicates down.

)과 부분 지연(

)을 구하기 위해, 하기의 [수학식 21]를 이용한다. The base point for the next sampling point (

) And partial delay (

), The following [Equation 21] is used.

가 된다. 여기서, mod1은 1로 나눈 나머지를 가리킨다. finally,

Becomes Where mod1 is the remainder divided by one.

)을 추정한다.The sample timing adjustment controller 24 determines the relative time delay (Equation 22) with respect to the symbol rate 1 / T.

Estimate).

)을 T시간 전에 추정한 값(

)으로 대치하면 하기의 [수학식 23]과 같다.Where the relative time delay value (

) Is estimated T hours ago (

) Is replaced by Equation 23 below.

)과 부분 지연(

)을 하기의 [수학식 24]를 통해 구한다.The base point for the next sampling point (

) And partial delay (

) Is obtained from Equation 24 below.

)은 제한된 값(

)을 가져야 하므로, 0과 1의 경계에서 신중하게 다루어야 한다. 즉,

이 1에 가까지면 샘플 타이밍 조절 제어기(24)의 다음 값(

)은 매우 작은 값을 가질 것이다. 이때, 시간 지연 추정 값의 차이(

)는 1에 가깝다. Where relative time delay (

) Is a restricted value (

), So be careful to handle it at the boundary between 0 and 1. In other words,

If this value is 1, the next value of the sample timing controller 24 (

) Will have a very small value. At this time, the difference between the estimated values of the time delay (

) Is close to one.

은 매우 천천히 변하므로

가 될 것이다. 이때,

가 1의 경계를 가로지를 때 생기는 계산 착오를 보완하기 위하여, 도 5와 같은 주기 1의 톱니형 함수 SAW(x)를 사용한다. But,

Changes very slowly, so

Will be. At this time,

In order to compensate for the miscalculation caused by crossing the boundary of 1, the sawtooth function SAW (x) of period 1 as shown in FIG. 5 is used.

FIG. 6 is an exemplary performance analysis diagram of a sample timing tracking device in a direct sequence spread spectrum wireless picocell communication system according to an embodiment of the present invention. After adding a timing error of +0.5 chip, an AWGN (Additive White Gaussian Noise) channel is shown. An example of measuring " RMS jitter " in a steady state with respect to the output of the sample timing adjustment controller 24 according to a change in the signal-to-noise ratio (SNR) below.

)는 ±0.9로 설정하였고, 누적 회수 N은 5로 설정하였다.Where threshold (

) Was set to ± 0.9 and the cumulative number N was set to 5.

)는 잡음의 영향에 덜 민감하도록 가능한 높은 값을 부여하였다. In addition, since the sampling rate of 4 times is applied, the timing error of +0.5 chip means that the sampling time is as fast as 2 sample intervals.

) Gave the highest possible value to make it less sensitive to the effects of noise.

As shown in FIG. 6, it can be seen that the "RMS jitter" of the algorithm output value decreases according to the SNR change, and the "RMS jitter" within 0.25 chips, that is, within 1 sample, appears at SNR 8dB. .

In addition, it can be expected that if the value of the cumulative number N is increased, a smaller "RMS jitter" is obtained.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical 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 extracts a cross-correlation function value using an early signal and a late signal based on a signal sampled at a current gate and detects a timing error. After stabilizing and normalizing the detected timing error, by adjusting the sample timing point once every N (natural number) accumulations, the performance of the wireless picocell system can be improved.

Claims (10)

A sample timing tracking device in a wireless picocell communication system of a direct sequence spread spectrum method, Based on the signal sampled at the current gate (On-time), an early signal with a -1 / Ns (Ns is any natural number) chip offset and a late (with + 1 / Ns chip offset) After extracting the cross-correlation function value using the Late signal, the difference between the magnitude squared of the cross-correlation function value extracted through the early gate and the cross-correlation function value extracted through the late gate Timing error detecting means for detecting a as a timing error; Filtering means for stabilizing the timing error detected by the timing error detecting means; Normalization means for normalizing the timing error stabilized by the filtering means; Sample timing adjustment control means for controlling to adjust a sample timing point once every N (natural numbers) cumulative times using a stabilized (average) timing error normalized by the normalization means; And Interpolation means for adjusting a sample timing point according to the control of the sampling timing adjustment control means Sample timing tracking device in a wireless picocell communication system of the direct sequence spread spectrum method comprising a. The method of claim 1, The timing error detection means, A sample timing tracking device in a wireless picocell communication system of a direct sequence spread spectrum method, characterized by extracting a cross-correlation function value as shown in Equation A below. Equation A

Here, L means the length of the codeword (codeword),

Means an early gate at -1 / Ns chip offset based on the optimal sample point,

Denotes a receive gate at a + 1 / Ns chip offset, and C (i) denotes a bit or code value of one of the 11-chip Barker codes. Also,

Denotes symbol timing in units of codeword length (L),

Denotes a received signal received at a sampling time k in a receiver chip unit. The method of claim 2, The timing error detection means, Detects the timing error through Equation B below. If the sample timing at the current gate is the optimal sample point,

A sample timing tracking device in a wireless picocell communication system of a direct sequence spread spectrum method, characterized by detecting a zero as a value. Equation B

The method according to claim 1 or 2, The filtering means, A sample timing tracking device in a direct sequence spread spectrum wireless picocell communication system characterized by stabilizing timing error through Equation (C) below. Equation C

Here, N means cumulative number of times for filtering,

Means the cross-correlation function value extracted from the initial sample point (gate),

Denotes the cross-correlation function value extracted from the current sample point (gate), that is, the energy of the symbol.

Is

Means the mean value of the cross-correlation function values extracted from the current sample point. The method of claim 4, wherein The normalization means, A sample timing tracking device in a wireless picocell communication system of a direct sequence spread spectrum method, characterized by normalizing a stabilized timing error as shown in Equation D below. [Equation D]

here,

Means the cross-correlation function value extracted from the initial sample point (gate),

Is

Means the mean value of the cross-correlation function values extracted from the current sample point. The method of claim 5, The sample timing adjusting means, Thresholds for + and-(

),

<Sample timing point <

Sample timing tracking apparatus in a direct sequence spread spectrum wireless picocell communication system characterized by advancing-retard control of the sample timing point by ± 1 / Ns samples to satisfy the following. The method of claim 6, The interpolation means, A sample timing tracking device in a direct sequence spread spectrum wireless picocell communication system, characterized in that it is an interpolator of a polynomial (Finite Impulse Response) type. The method of claim 7, wherein The interpolation means, A sample timing tracking device in a direct sequence spread spectrum wireless picocell communication system, characterized in that the coefficient (number) is set to an even number to maximize accuracy. In the sampling timing tracking method in the sample timing tracking device, Based on the signal sampled at the current gate (On-time), an early signal with a -1 / Ns (Ns is any natural number) chip offset and a late (with + 1 / Ns chip offset) After extracting the cross-correlation function value using the Late signal, the difference between the magnitude squared of the cross-correlation function value extracted through the early gate and the cross-correlation function value extracted through the late gate Detecting as a timing error; Stabilizing the detected timing error; Normalizing the stabilized timing error; And A sample timing adjusting step of adjusting a sample timing point once every N cumulative number of times by using the normalized stabilized (average) timing error Sampling timing tracking method in a sample timing tracking device comprising a. The method of claim 9, The sample timing adjustment step, Thresholds for + and-(

),

<Sample timing point <

Advancing-retard control of the sample timing point by ± 1 / Ns samples to satisfy the following.

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