KR100477597B1 - Tap delay adjustment method using bit error rate and tap delay adjustment device using it - Google Patents

Abstract

The present invention relates to a tap delay adjustment method using a bit error rate to prevent a decoding error of a received signal in a fading environment to improve the reception performance of the rake receiver, and a tap delay adjustment device using the same.

The tap delay adjustment apparatus using the bit error rate of the present invention includes a coupling means for supplying and combining signals having respective delay times, a signal strength detecting means for detecting signal strength of a signal having a delay time, and a serial connection to the coupling means. And error correction means for detecting the bit error rate in the signal from the combining means, and control means for selectively varying the delay time in accordance with the value of the bit error rate and the signal strength in common connection with the signal strength detecting means and the error correction means. .

The tap delay adjustment method using the bit error rate and the tap delay adjustment device using the same can improve the reception performance of the mobile communication terminal and the base station by adjusting the tap delay to adapt to the fading environment while reducing the decoding error probability in the fading environment. have.

Description

Tap delay adjustment method using beat error rate and tap delay adjustment device using the same

The present invention relates to a mobile communication system for providing high frequency wireless communication between a base station and a base station such as a cellular phone. Particularly, the present invention relates to a bit error rate for improving a reception performance of a rake receiver by preventing a decoding error of a received signal in a fading environment. The present invention relates to a tap delay adjustment method and a tap delay adjustment device using the same.

Typically, portable communication terminals, such as cellular phones, allow a user to perform bidirectional mobile wireless communications. The mobile base station communicates radio frequency (RF) radio communications with a portable communication terminal through a cell site using code division multiple access (CDMA) spread spectrum signals. Perform. The base station is also connected to a Public Switched Telephone Network (PSTN) for making phone calls between users of portable communication terminals and wired subscribers.

On the other hand, a receiver for receiving a high frequency radio signal in a mobile communication system is employed in not only a base station but also a terminal. The receiver employed in the base station decodes and demodulates the high frequency radio signal transmitted from the terminal. The receiver employed in the terminal decodes and demodulates the high frequency radio signal transmitted from the base station. 1 illustrates a receiver applied to a typical mobile communication system.

Referring to FIG. 1, a receiver applied to a conventional mobile communication system includes an intermediate frequency processor (hereinafter referred to as “IF”) which converts a received high frequency signal (RF) into an intermediate frequency (IF) signal. ), A low pass filter (LPF) 4 for low-pass filtering the IF signal, an analog / digital converter (ADC; 6) for converting an analog signal from the low pass filter 4 into a 4-bit digital signal, A received signal strength (RSSI) detector 8 for detecting the intensity of the output signal of the low pass filter 4 and a rake receiver 10 having a tab delay line (hereinafter referred to as "TDL") structure Equipped.

The IF processing section 2 is connected in series with the low pass filter 4, and the low pass filter 4 is connected in common with the analog / digital converter 6 and the received signal strength detector 8. The analog-to-digital converter 6 is connected in series to the rake receiver 10. The analog-to-digital converter 6 converts the signal from the low pass filter 4 into 4-bit digital data and supplies it to the rake receiver 10. The IF signal is low band filtered by the low pass filter 4 and sampled at n per chip (typically 1 chip = 1 / ww = frequency) by the analog-to-digital converter 6 (typically sampled at 8 bits). )do. This means that when the correlation value is obtained from the rake receiver 10, since the analog value cannot be integrated, it is digitalized to detect the energy with n values (normally 8 values) per chip.

FIG. 2 is a block diagram illustrating a detailed configuration of the rake receiver 10 shown in FIG. 1. Referring to FIG. 2, the rake receiver 10 converts a received signal (a 4-bit digital signal) into a fixed delay time. First through n + 1 multipliers 31 through n that multiply pseudo noise (PN) codes by the first through nth delay units 21 through 2n to delay and the output signals of the delay units 21 through 2n. N + 1 fingers consisting of 3n + 1), and a combiner 40 for coupling an output symbol to n + 1 fingers.

The first delay unit 29 is commonly connected to the adjacent second delay unit 21 and the second multiplier 31, and in turn, each delay unit is commonly connected to the adjacent delay unit and one multiplier. PN codes are commonly supplied to the first to n + 1 multipliers 31 to 3n + 1. The first finger is fed to the combiner 40 without delay by multiplying the 4-bit digital data from the analog-to-digital converter 6 by a direct wave and a PN code. The second finger is delayed for a predetermined delay time by the first delay unit 21 to the input digital data, and a pseudo noise code (PN code) is added to the combiner 40. The n + 1th finger is supplied to the combiner 40 by adding a pseudo noise code to digital data delayed by the delay time accumulated by the first delay unit 21 to the nth delay unit 2n.

The rake receiver 10 serves to synchronize the delay of the digital data generated due to the fading environment by using diversity. That is, in the CDMA scheme, the rake receiver 10 is typically adopted because a signal delayed by a building, a terrain, etc. as well as a main signal is included when transmitting and receiving between a base station and a terminal. Therefore, the receiving end (terminal or base station) receiving these signals has a delay process as much as the time delay by fading using the rake receiver 10 before decoding (Viterbi decoding), and then the main signal sample and the delay signal. The correlation process is performed on a sample (at least 2 time shifts). The correlation result is combined in the symbol combiner 40 to determine the content of the signal. Since the rake receiver 10 performs a correlation process by the plurality of delay units 21 to 2n, it is called a structure of a tab delayed line (TDL), and the delay amount of the delay units 21 to 2n is fixed. have. However, as the delay units 21 to 2n fix tap delays, decoding errors may occur due to failure of properly synchronizing the received signals through various paths.

In order to solve this problem, a method for adjusting a tap delay of a rake receiver using a received signal strength identity (hereinafter referred to as "RSSI") of a received signal is proposed in Korean Patent Application No. P96-69502. There is a bar. In the proposed technique, a method of adjusting the tap delay is to adjust the tap delay according to the size of the RSSI every predetermined time (for example, 10 ms). Accordingly, the tap delay method of the rake receiver according to the related art needs to adjust the delay time when the fading goal is severely generated due to the fast moving speed of the terminal. In addition, the tap delay of the rake receiver must have the same amount of delay as the fading channel for correlation through diversity. However, the chip delay caused by the fading channel depends on the channel environment and the number of paths. Therefore, control of the tap delay is required so that the rake receiver can be optimally correlated.

Accordingly, an object of the present invention is to reduce the decoding error probability in a fading environment, and to adjust the tap delay using a bit error rate to improve the reception performance of the mobile communication terminal and the base station by using a tap delay adjustment adapted to the fading environment and It is to provide a tap delay control device using the same.

In order to achieve the above object, the tap delay adjustment apparatus using the bit error rate of the present invention is combined means that is supplied and combined with a signal having a respective delay time, and signal strength detection means for detecting the signal strength of the signal having a delay time And error correction means for detecting a bit error rate in the signal from the coupling means in series with the coupling means, and commonly connected to the signal strength detection means and the error correction means to selectively select a delay time according to the values of the bit error rate and the signal strength. And variable control means.

The tap delay adjustment method using the bit error rate according to the present invention comprises the steps of inputting a signal having a delay time, detecting a bit error rate and a signal strength from the delay time, and setting the bit error rate to a predetermined first reference value and the signal. And comparing the intensity with a second predetermined reference value and selectively varying the delay time according to the comparison result.

Other objects and features of the present invention other than the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 3 to 5.

3 is a block diagram illustrating a tap delay adjustment apparatus using a bit error rate according to the present invention.

Referring to FIG. 3, the tap delay adjustment apparatus using the bit error rate according to the present invention includes first to third fingers 41 to 43 and second and third fingers 41 to 43 delayed by respective amounts of time delay. The first and second RSSI detectors 44 and 45 connected to the second and third fingers 42 and 43 to detect the intensity of the signal input on average from the second and third fingers 42 and 43; 43 and a combiner 46 connected in common with the first and second RSSI detectors 44 and 45 to add a bit of pseudo noise (PN) to the signal from the first to third fingers 41 to 43. And a Viterbi decoder 47 that is connected in series with the combiner 46 and decodes the bit value from the signal of the bootie to the combiner 46, corrects the error, and generates a bit error rate (BER) accordingly. ) And the RSSI detector (3) are commonly connected to the delay units 42a and 43b of the second and third fingers 42 and 43, the first and second RSSI detectors 44 and 45, and the Viterbi decoder 47. And a delay control unit 48 for adjusting tap delays of the second and third fingers 41 to 43 at the RSSI level from 44 and 45 and the error rate from the Viterbi decoder 47.

The sampled signal from the analog / digital converter 6 is commonly supplied to the first to third fingers 41 to 43 via the first to third nodes 51 to 53. The first finger 41 detects a direct wave and digital data is supplied to the combiner 46 without delay. The second finger 42 and the third finger 43 have a delay time by the delay parts 42a and 43a, respectively. The output signal from the second finger 42 is commonly supplied to the first RSSI detector 44 and the combiner 46 via the fourth node 54. The output signal from the third finger 43 is commonly supplied to the second RSSI detector 45 and the combiner 46 via the fifth node 55.

The first and second RSSI detectors 44 and 45 detect the strengths of the output signals of the second and third fingers input via the fourth and fifth nodes, and supply the RSSI level to the delay controller 48. . The Viterbi decoder 47 performs error correction on the signal from the combiner 46 and supplies the bit error rate to the delay controller 48. The delay control unit 48 controls the delay unit 42a of the second and third fingers 42 and 43 at the RSSI level from the first and second RSSI detection units 44 and 45 and the error rate from the Viterbi decoder 47. The delay time of 43a) is selectively adjusted. At this time, the delay control unit 48 checks the RSSI level when the error rate of the Viterbi decoder 47 is equal to or greater than a specific level, and the delay units 42a of the second and third fingers 42 and 43 when the RSSI is less than or equal to the specific level. Adjust the delay time of 43a). In addition, the delay control unit 48 allows the error rate (Bit Error Rate) to selectively adjust the tap delay and the reference error rate, which is a reference for comparison, to vary according to the type of data. Therefore, the delay control unit 48 increases the reference error rate of the voice data having a relatively large allowable error rate, and adjusts the reference error rate of the important data to be small.

4 is a flowchart illustrating a tap delay adjustment method using a bit error rate according to the present invention, which is performed by the delay controller 48. The flowchart of FIG. 4 will be described with reference to the block diagram of FIG.

The delay control unit 48 receives the RSSI levels from the first and second RSSI detection units 44 and 45 and the bit error rate (BER) from the Viterbi decoder 47. The delay control unit 48 compares an error rate (hereinafter referred to as "BER") from the Viterbi decoder 47 with a predetermined reference error rate. (60 step) At this time, the BER is smaller than the reference error rate. In this case, step 60 is repeated to compare the BER supplied with the reference error rate. On the other hand, when the BER is larger than the reference error rate, the RSSI level from the RSSI detectors 44 and 45 is compared with the predetermined reference level. (Step 61) If the RSSI level is smaller than the reference level, the step 60 is repeated. do. If the RSSI level is greater than the reference level, the 61st step is performed by adjusting the tap delays of the delay parts 42a and 43a of the second and third fingers 42 and 43 (step 62).

The reference error rate is a reference value that is adaptively changed according to the type of data to be serviced. As a result of comparing this error rate with BER, when the BER is less than the reference error rate, the reception of the serviced data is good, so it is necessary to adjust the tap delay. none. In contrast, when the BER is larger than the reference error rate, the detected RSSI is compared with a predetermined reference value, and as a result, the tap delay in which the RSSI is larger than the reference value is adjusted.

At this time, the adjusted tap delay is adjusted within the range of one chip, and there are K delay control points for the signal sampled K times. The tap delay control point is independent of each finger, and the first finger detects a direct wave and does not adjust the delay.

FIG. 5 is a diagram for explaining the case where the delay of each finger is fixed (FIG. 5 (A)) and when the digital data is input to the rake receiver (FIG. 5 (B)).

5 (A) and 5 (B), the rake receiver 10 does not integrate an analog value when obtaining a correlation value of a signal received from a multipath, so that the rake receiver 10 is digitalized to K values sampled per chip. The energy is detected. In this case, it is shown that the delay of the rake receiver 10 is synchronized by the time that the chip is delayed according to the fading environment when the delay is variable compared to the case where the delay is fixed.

As a result, the tap delay adjustment method using the bit error rate and the tap delay adjustment device using the same adjust the tap delay by detecting the BER and the RSSI and comparing them with a predetermined reference value.

As described above, the tap delay adjustment method using the bit error rate and the tap delay adjustment device using the same reduce the error probability of decoding in the fading environment and adjust the tap delay to adapt to the fading environment of the mobile communication terminal and the base station. Receive performance can be improved.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a block diagram of a receiver applied to a conventional mobile communication system.

FIG. 2 is a detailed block diagram of a rake receiver during a first trip; FIG.

3 is a detailed block diagram of a tap delay adjustment apparatus using a bit error rate according to an embodiment of the present invention.

FIG. 4 is a flowchart illustrating operation of tap delay adjustment of the delay controller of FIG. 3. FIG.

5 is a view showing a comparison between the conventional tap delay fixed method and the tap delay adjustment method of the present invention.

Explanation of symbols on the main parts of the drawings

2: intermediate frequency processing unit 4: low pass filter

6: Analog-to-digital converter 8,44,45: Receiving signal detector

10: Rake receiver 21 to 2n: delay unit

31 to 3n + 1: Multiplier 40,46: Combiner

41,42,43: finger 47: Viterbi decoder

48: delay control unit

Claims (4)

For a rake receiver, Combining means for supplying and combining signals having respective delay times; Signal strength detecting means for detecting signal strength of the signal having the delay time; Error correcting means connected in series with said combining means for detecting a bit error rate in a signal from said combining means; And a control means connected to the signal strength detecting means and the error correcting means and selectively varying the delay time according to the bit error rate and the value of the signal strength. . The method of claim 1, The control means compares the signal strength with a predetermined second reference value under a condition that the bit error rate is greater than the predetermined first reference value by comparing the bit error rate with a predetermined first reference value. And wherein the delay time is selectively varied when the signal strength is greater than the second reference value. For a rake receiver, Inputting a signal having a delay time; Detecting a bit error rate and a signal strength from the delay time; And adjusting the delay time selectively by comparing the bit error rate with a predetermined first reference value and the signal strength with a predetermined second reference value. How to adjust the delay. The method of claim 3, wherein The bit error rate is greater than the first reference value, And adjusting the delay time when the signal strength is less than the second reference value.

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