KR20080044122A - Method for demodulating code acquisition using code and order of observation - Google Patents

Abstract

A method for demodulating code acquisition using a code and an order of observation is provided to reduce hardware complexity in comparison with a double correlation estimator. A differential output acquisition process is performed to acquire a differential output according to a pseudo noise code in a generating period. A delayed pseudo noise code acquisition process is performed to acquire a delayed pseudo noise code by delaying a differential output of a non-inverted pseudo noise code as much as the non-inverted pseudo noise code. An equalizing process is performed to delay a phase by using a phase shift network and to equalize an output phase and the non-inverted pseudo noise code to each other.

Description

Method for Demodulating Code Acquisition Using Code And Order of Observation

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram illustrating a configuration of an estimator according to a double correlation sequential estimation method.

2 is a block diagram illustrating a structure of an estimator according to a phase shift network based differential sequential estimation method according to the present invention.

3 is a flow chart of an occurrence function of a sequential estimation related code estimator.

을 사용했을 때의 칩당 신호대 잡음비에 따른 평균 부호획득 시간을 나타낸 그래프.4 is a pseudo noise code source polynomial

The graph shows the average code acquisition time according to the signal-to-noise ratio per chip.

을 사용했을 때의 칩당 신호대 잡음비에 따른 평균 부호획득 시간을 나타낸 그래프.5 is a pseudo noise code source polynomial

The graph shows the average code acquisition time according to the signal-to-noise ratio per chip.

[1] B. Sklar, Digital Communications: Fundamentals and Applications, Upper Saddle River, NJ: Prentice-Hall, 2001.

[2] AW Lam and S. Tantaratana, Theory and Applications of Spread-Spectrum Systems: A Self-Study Course, Piscataway, NJ: IEEE, 1994.

[3] A. Polydoros and CL Weber, "A unified approach to serial search spread-spectrum code acquisition-part I: general theory"' IEEE Trans. Comm., Vol. 32, pp. 542-549, May 1984.

[4] LB Mistein, J. Gevargiz, and PK Das, "Rapid acquisition for direct sequence spread-spectrum communications using parallel SAW convolvers", IEEE Trans., Vol. 33, pp. 593-600, July 1985.

[5] MK Simon, JK Omura, RA Scholtz, and BK Levitt, Spread Spectrum Communications HandBook , New York, NY: McGraw-Hill, 1994.

[6] RB Ward, "Acquisition of pseudonoise signals by sequential estimation", IEEE Trans. Comm. , vol. 13, pp. 474-483, Dec. 1965.

[7] J.H. Chiu and LS Lee, "An improved sequential estimation scheme for PN acquisition", IEEE Trans. Comm. , vol. 36, pp. 1182-1184. Oct. 1988.

[8] GG Koller and MA Belkerdid, "A dual correlating sequential estimator for spread spectrum PN code acquisition", in Proc. IEEE MILCOM , Boston, MA, Oct. 1993, pp. 522-526.

[9] JS Lee and LE Miller, CDMA Systems Engineering HandBook , Boston, MA: Artech House, 1998.

[10] Yoon, Seok-ho, Kim, Sun-yong, "Pseudo-noise Code Acquisition in Low Signal-to-Noise Ratio Environment Using Seed Cumulative Sequential Estimation", Journal of Korean Institute of Communication Sciences , Vol.28, No.9 , pp. 678-682, September 2003.

The present invention relates to a differential sequence estimation method based on a phase shift network, and more particularly, to a differential sequence estimation method based on a phase shift network for obtaining a pseudo noise code in a data modulation environment.

The conventional sequential estimator proposed in the prior art document information [7] (hereinafter, [N] represents N times the prior art document information) can obtain a pseudo noise code, but it is difficult to demodulate the original data. there was.

In order to solve this problem, the conventional technique proposed in [8] proposes a dual correlation sequential estimator capable of demodulating data as well as obtaining a pseudo noise code.

However, although the dual correlation sequential estimator has improved performance compared to the sequential estimator of [7], there is a problem in that the system becomes complicated.

An object of the present invention is to provide a method for differential sequential estimation based on a phase shift network with about half the hardware complexity of the conventional dual correlation sequential estimating method capable of demodulating data as well as obtaining a pseudo noise code. .

Another object of the present invention is to provide a differential sequence estimation method based on a phase shift network capable of obtaining a pseudo noise code, an inverted pseudo noise code, and demodulating data in a data modulation environment.

의 입력되는 의사 잡음 부호가

이면 차동 출력

는

이고, 의사 잡음 부호가

이면 차동 출력

는

를 얻는 단계; 반전되지 않은 의사 잡음 부호

를 차동 출력한 차동 출력

를 반전되지 않은 의사 잡음 부호 대비

만큼 지연된 의사 잡음 부호

를 얻는 단계; 및 상기 위상변이 네트워크를 이용하여

만큼 위상을 지연시켜서 출력의 위상을 상기 반전되지 않은 의사 잡음 부호와 동일하게 만드는 단계를 포함하는 것을 특징으로 하는 위상 변이 네트워크 기반의 차동 순차 추정 방법을 제공한다.In order to achieve the above object, the present invention provides a phase shift network-based differential sequential estimation method, wherein

The input pseudo noise code of

Differential output

Is

And the pseudo noise code

Differential output

Is

Obtaining; Uninverted pseudo noise code

Output with differential output

Unconverted pseudo noise code contrast

Delayed pseudo noise code

Obtaining; And using the phase shift network

A phase shift network based differential sequential estimation method comprising the step of delaying the phase by an amount equalizing the uninverted pseudo noise code.

만큼 지연된 의사 잡음 부 호를 생성시키기 위해서 마스크 다항식

을 사용하는 것을 특징으로 한다.And, for the input pseudo noise code

Mask polynomials to generate pseudo noise codes delayed by

It characterized in that to use.

(Example)

A differential sequential estimation method based on a phase shift network according to the present invention will be described in detail with reference to the accompanying drawings showing a preferred embodiment of the present invention.

을 사용했을 때의 칩당 신호대 잡음비에 따른 평균 부호획득 시간을 나타낸 그래프, 도 5는 의사 잡음 부호 근원 다항식

을 사용했을 때의 칩당 신호대 잡음비에 따른 평균 부호획득 시간을 나타낸 그래프이다.2 is a block diagram illustrating a structure of an estimator according to a phase shift network based differential sequential estimation method according to the present invention, FIG. 3 is a flow chart of a generation function of a sequential estimation related code estimator, and FIG. 4 is a pseudo noise code source. Polynomial

Is a graph showing the average code acquisition time according to the signal-to-noise ratio per chip when Fig. 5 is used.

Shows the average code acquisition time according to the signal-to-noise ratio per chip.

1. System operation description

2 is a block diagram illustrating a structure of a differential sequence estimator based on a phase shift network. The differential sequence estimator based on a phase shift network includes a hard limiter, a level shifter 1 and 2, a differential operator, a load control switch, a pseudo It consists of noise code generator, phase shift network, correlator, absolute value processor, threshold comparator, and load / track logic.

When the phase shift network based differential sequential estimator operates according to the present invention, the position of the load control switch is switched to S by the load / tracking logic, and the differential starts to operate.

칩 동안 의사 잡음 부호 발생기로 적재된다(의사 잡음 부호 발생기의 시프트 레지스터의 저장 소자는

개이지만 차동기 출력은 동작 시작 후 1 칩이 지난 후부터 정상적인 값이 나오기 때문에 적재 시간은

칩이 된다).The output of the differential is

During the chip is loaded into the pseudo noise code generator (the storage element of the shift register of the pseudo noise code generator

The differential output has a normal value since one chip after starting operation, so the loading time is

Chip).

라 둘 수 있다.The output of the differential is

Can be

이고 송신 데이터에 따라

혹은

(여기서,

)가 1 또는 -1로 천이되어 송신될 때, 수신단에서는 잡음이 섞인 1 또는 -1 신호가 수신되고, 하드 리미터 및 레벨 시프터 1을 거쳐서 0 또는 1로 판단된다.The pseudo noise code generated at the transmitting end

And according to the sending data

or

(here,

) Is shifted to 1 or -1 and transmitted, the receiving end receives a noisy 1 or -1 signal and determines 0 or 1 via the hard limiter and level shifter 1.

, 반전된 의사 잡음 부호 송신 시에는 레벨 시프터 1의 출력을

라 둘 수 있다.If this decision is made correctly, the output of level shifter 1 will be disabled when transmitting an uninverted pseudo noise code.

When transmitting an inverted pseudo noise code, the output of level shifter 1 is

Can be

일 때는

로 둘 수 있고 레벨 시프터 1의 출력이

일 때는

로 주어진다.Level shifter 1 output

When

And the output of level shifter 1

When

Is given by

는 항상

로 주어지 며, 이는 위상변이-덧셈 특성(shift-and-add property, [2] 참조)에 의해 의사 잡음 부호

가

만큼 위상 변이된 형태가 된다.That is, the differential output of the receiver at both the inverted pseudo noise code and the uninverted pseudo noise code are transmitted.

Is always

Which is given by the shift-and-add property (see [2]).

end

The phase shifted form.

로 쓸 수 있다. 즉, 입력 의사 잡음 신호에 대한 추정이 정확하게 이루어진다면 의사 잡음 부호 발생기에서 발생되는 의사 잡음 부호는 송신단에서 발생되는 의사 잡음 부호 대비

만큼 위상 차이가 생기게 된다.Therefore, the differential output is always

Can be written as That is, if the estimation of the input pseudo noise signal is made correctly, the pseudo noise code generated by the pseudo noise code generator is compared with the pseudo noise code generated by the transmitter.

As long as the phase difference occurs.

와 위상이 같아지게 된다.This phase difference can be compensated through the phase shift network. This ensures that the output of the phase shift network is an inverted pseudo noise code

Will be in phase with.

칩 동안(여기서

은 의사 잡음 부호의 주기이며, 크기는

이다.) 상관시킨다.At the end of the loading process, the load / switch logic switches the load control switch to P, which then outputs the output of the phase shift network and the input pseudo noise signal.

While the chip (where

Is the period of the pseudo noise code, and the magnitude is

Correlate.

When sign acquisition is made, the correlation value is positive when a non-inverted pseudo noise code is received, and the correlation value is negative when a reversed pseudo noise code is received.

는 절대 값이 취해져서 문턱 값

와 비교된다. 만약

가

보다 크면 부호 획득이 이루어진 것으로 판단하고 추적을 시작하고

보다 작으면 부호 획득에 실패한 것으로 판단하고, 적재 과정부터 다시 시작한다.Thus the correlation value

Is the absolute value of the threshold

Is compared with. if

end

Greater than it determines that sign acquisition has taken place and starts tracing.

If smaller, it is determined that the code acquisition has failed, and starts again from the loading process.

After the code acquisition, the correlation value is used to determine the received data, and the data at the moment of code acquisition can also be demodulated normally.

Thus, as shown in Table 1, it can be seen that when compared with the conventional dual correlation sequential estimator, the estimator according to the invention has the same sign acquisition performance and the hardware is simpler.

Estimator Depot Count Correlator Count Absolute handler count Threshold Comparator Count Number of differentials Invert Controller Count Combination Log Count Dual Correlation Sequential Estimator 2n + 1 2 2 2 0 One One Estimator of the Invention n + 1 One One One One 0 0

개 더 적게 사용된다.In other words, the conventional dual correlation sequential estimator uses two pseudo noise code generators, but the estimator according to the present invention uses only one pseudo noise code generator, and instead, the storage element is added because a differential circuit and a phase shift network are added.

Dogs are used less.

The longer the period of the pseudo noise code used, the greater the gain in terms of hardware complexity.

2. Phase Shift Network

The source polynomial of the pseudo noise code generator can be written as Equation 1.

는 도 2의 의사 잡음 부호 발생기에서 시프트 레지스터의 각 저장 소자 값들을 이진 덧셈기로 연결할지 하지 않을지를 결정해주는 스위치 역할을 한다(0이면 연결하지 않고, 1이면 연결한다).In Equation 1, the coefficient

In the pseudo-noise code generator of Figure 2 serves as a switch that determines whether or not each storage element value of the shift register is connected to a binary adder (0 if not, 1 if).

인 의사 잡음 부호는 수학식 2와 같이 계수들이 의사 잡음 부호를 나타내는 다항식 형태로 쓸 수 있다([9] 참조).The period that occurs through the source polynomial, such as

The pseudo noise code may be written in a polynomial form in which the coefficients represent the pseudo noise code as shown in Equation 2 (see [9]).

차 보다 낮은 분자 다항식을 근원 다항식으로 나눔으로써 수학식 3을 얻을 수 있다.A polynomial pseudo noise code such as Equation 2 is as follows.

Equation 3 can be obtained by dividing the molecular polynomial lower than the difference by the source polynomial.

을 제외하면

개의 분자 다항식이 존재할 수 있다. 이로부터 위상이 서로 다른 의사 잡음 부호가

개 존재함을 알 수 있다. 의사 잡음 부호

를 수학식 4와 같이 정의하면,

칩 지연된 의사 잡음 부호는 다음과 같이 둘 수 있다.In equation (3)

Except

There may be two molecular polynomials. This results in pseudo-noise codes with different phases

It can be seen that there are dogs. Pseudo noise code

If defined as Equation 4,

The chip delayed pseudo noise code can be written as follows.

If the inverted pseudo noise code input to the differential in Figure 2 is written as Equation 5, the differential output can be written as Equation 6 in the polynomial form.

만큼 지연된 의사 잡음 부호로 생각할 수 있으므로 수학식 7과 같이 쓸 수 있다.Also, compare the uninverted pseudo-noise code to the differential output as a differential.

Since it can be thought of as a delayed pseudo noise code, it can be written as Equation 7.

을 구할 수 있으며, 위상 변이 네트워크를 이용하여

만큼 위상을 지연시키면 그 출력의 위상은 반전되지 않은 의사 잡음 부호와 동일하게 된다.From equations (6) and (7), the delay value

Can be obtained by using a phase shift network

Delaying the phase by will cause the output phase to equal the uninverted pseudo noise code.

으로)로 입력되는 의사 잡음 부호에 대해

만큼 지연된 의사 잡음 부호를 생성시키기 위해서는 수학식 8과 같은 마스크 다항식을 사용하면 된다([9] 참조).Pseudo-noise code generator of FIG. 2 (first storage element of shift register)

For pseudo noise codes

To generate a delayed pseudo noise code, a mask polynomial such as Equation 8 can be used (see [9]).

는 그림 1의 위상 변이 네트워크에서 시프트 레지스터의 각 저장 소자 값들을 이진 덧셈기로 연결할지 하지 않을지를 결정해 주는 스위치 역할을 한다.In Equation 8, the coefficient

In Figure 1, the phase shift network serves as a switch to determine whether or not each storage element value in the shift register is connected to a binary adder.

3. Average code acquisition time

The average time for sign acquisition can be obtained using a generation function flow graph (see [3] and [10]).

3 is a flowchart of an occurrence function of a sequential estimation related technique. 3, an average code acquisition time of the sequential estimator, the dual correlation sequential estimator, and the inventive estimator can be obtained.

는 칩을 올바르게 추정할 확률이며(correct chip probability),

은

개의 칩을 올바르게 추정할 확률이고(칩 정추정 확률),

은

로 주어진다.

는 검파 확률(

개의 칩 모두가 올바르게 추정되었을 때, 실제로 부호 획득이 이루어질 확률)이며,

는 오경보 확률(

개의 칩 가운데 적어도 하나가 올바르게 추정되지 않았음에도, 부호 획득이 이루어졌다고 판단될 확률)이고,

는 오경보에 대한 손실 비용 (penalty factor)이다.In Figure 3

Is the probability of correctly estimating the chip (correct chip probability),

silver

Probability of correctly estimating chips (chip estimation probability),

silver

Is given by

Is the probability of detection (

Probability of sign acquisition in practice when all four chips are correctly estimated,

Is the false alarm probability (

Probability that it will be determined that sign acquisition has been made, even though at least one of the

Is the penalty factor for false alarms.

는 수학식 9와 같이 유도될 수 있다.Occurrence function from FIG. 3

Can be derived as in Equation (9).

는 수학식 10과 같이 얻을 수 있다.Average Sign Acquisition Time from Equation 9

Can be obtained as shown in Equation 10.

는 검사 시간으로서,

와 같으며 적재와 상관에 소요되는 시간을 의미한다.In Equation 10,

Is the test time,

Same as the time required for loading and correlation.

As shown in Equation 10, the code acquisition time is determined by chip estimation probability, detection probability, false alarm probability, false alarm loss cost, loading time, and pseudo noise code length of the system.

번째 입력되는 신호는 수학식 11과 같이 주어진다.In case of sign acquisition and data demodulation using sequential estimation related system, after loading

The first input signal is given by Equation 11.

는 의사 잡음 부호의 칩 신호 전력이고,

는 같은 확률로 +1과 -1의 값을 가진다.

는

의 단면 전력 밀도 스펙트럼을 (one-sided power spectral density) 갖는 덧셈꼴 백색 정규 잡음이다. 즉,

는 평균 0, 분산

인 서로 독립이고 같은 분포(independent and identically distributed)를 갖는 정규 확률 변수이다.In Equation 11,

Is the chip signal power of the pseudo noise code,

Has the same probability of having values of +1 and -1.

Is

It is an additive white normal noise with a one-sided power spectral density. In other words,

Is an average of 0, variance

Are normal random variables that are independent and identically distributed.

4. Chip estimation probability, detection probability, false alarm probability of the estimator according to the present invention

는 수학식 12와 같이 표현할 수 있다.Chip Estimation Probability of the Estimator According to the Invention

Can be expressed as in Equation 12.

개의 칩이 모두 올바르게 추정되어 적재되었다면 이후 발생되는 의사 잡음 부호와 송신단의 의사 잡음 부호는 위상이 일치하게 되거나(반전되지 않은 의사 잡음 부호가 수신되는 경우) 정반대가 된다(반전된 의사 잡음 부호가 수신되는 경우).Successive

If all three chips are correctly estimated and loaded, the pseudo noise code generated afterwards and the pseudo noise code of the transmitting end are in phase (if an inverted pseudo noise code is received) or vice versa (inverted pseudo noise code is received. If you do).

의 확률밀도함수는 반전되 지 않은 의사 잡음 부호가 수신되는 경우와 반전된 의사 잡음 부호가 수신되는 경우 두 가지로 나눌 수 있다.Therefore, the correlation value when the correct loading

The probability density function can be divided into two cases when an inverted pseudo noise code is received and an inverted pseudo noise code.

의 확률밀도함수는 수학식 13과 같다.First, the correlation value when an uninverted pseudo noise code is received

The probability density function of is given by Equation 13.

의 확률밀도함수는 수학식 14와 같다.On the other hand, the correlation value when the inverted pseudo noise code is received

The probability density function of is given by Equation 14.

Equation 14 has the opposite sign and has the same variance as compared with Equation 13.

Since the probability of receiving an inverted pseudo-noise code and an inverted pseudo-noise code can be equally 1/2, the detection probability of the estimator according to the present invention can be obtained as shown in Equation 15.

와

는 서로 대칭이므로 수학식 15는 수학식 16과 같이 쓸 수 있다.Probability density function

Wow

Are symmetrical to each other, so Equation 15 can be written as Equation 16.

개의 칩 추정 가운데 어느 하나에서라도 오류가 발생한다면(wrong loading) 적재 후 발생되는 의사 잡음 부호는 송신단의 의사 잡음 부호와 위상이 어긋나게 된다.Meanwhile, continuous

If any of the two chip estimates fails, the pseudo noise code generated after loading is out of phase with the pseudo noise code of the transmitter.

로 주어진다.The correlation value for one period between pseudo-noise codes that are out of phase is determined by the correlation property (correlation property [2]).

Is given by

동안의 상관 결과는

로 근사화 할 수 있으며, 이는 다시 0으로 근사화 할 수 있다.Assuming that the pseudo-noise codes used in the transmission and reception system are large enough, when the pseudo-noise codes of the transmitter and the receiver are shifted

Correlation results

It can be approximated by, which in turn can be approximated by zero.

개의 칩 추정 가운데 어느 하나에서라도 오류가 발생한 경우 상관 값

의 확률밀도함수는 반전되지 않은 의사 잡음 부호가 수신되는 경우와 반전된 의사 잡음 부호가 수신되는 경우 모두 수학식 17과 같이 잡음 성분만으로 표현할 수 있다.Thus

Correlation if any of the two chip estimates fails

The probability density function of may be expressed only by the noise component, as shown in Equation 17, when both an inverted pseudo noise code and an inverted pseudo noise code are received.

From Equation 17, the false alarm probability of the estimator according to the present invention can be obtained as shown in Equation 18.

When the code acquisition time of the estimator according to the present invention is compared with the code acquisition time of the sequential estimator and the dual correlation sequential estimator using Equation 10, as shown in FIGS. Since the time and the check time are the same, it can be seen that the sign acquisition time is the same.

Signal-to-Noise Ratio per Chip (dB) Average Sign Acquisition Time of a Dual Correlation Sequential Estimator (chip) Average Sign Acquisition Time (chip) of the Estimator of the Invention 0 1335 1300 -One 1830 1815 -2 2607 2543 -3 3218 3237 -4 4583 4479 -5 5917 5881 -6 8161 7887 -7 10060 9723 -8 12241 12889 -9 15487 15111 -10 18825 19650

Signal-to-Noise Ratio per Chip (dB) Average Sign Acquisition Time of a Dual Correlation Sequential Estimator (chip) Average Sign Acquisition Time (chip) of Estimator 0 7166 7576 -One 10840 10568 -2 15289 15354 -3 22162 24362 -4 31024 34663 -5 47753 46126 -6 61956 64155 -7 89282 84383 -8 124323 110152 -9 153252 145940 -10 201861 196751

The present invention as described above provides the same code acquisition performance while having lower hardware complexity than the conventional dual correlation sequential estimator.

And, in the present invention, the gain in terms of hardware complexity provides a larger gain as the period of the pseudo noise code is longer.

Claims (2)

In a differential sequence estimation method based on a phase shift network, The frequency at which

The input pseudo noise code of

Differential output

Is

And the pseudo noise code

Differential output

Is

Obtaining; Uninverted pseudo noise code

Output with differential output

Unconverted pseudo noise code contrast

Delayed pseudo noise code

Obtaining; And Using the phase shift network

Delaying the phase by an amount such that the phase of the output is equal to the uninverted pseudo noise code; Phase shift network based differential sequential estimation method comprising a. The method of claim 1, wherein the input pseudo noise code

Mask polynomial to generate pseudo noise code delayed by

Differential sequential estimation method based on the phase shift network, characterized in that using.

Images