KR100567543B1 - Apparatus and method for preventing call disconnection using delay time compensation in code division multiple access communication system - Google Patents

Abstract

The present invention relates to an apparatus and method for preventing call disconnection using delay time compensation of a CDMA communication system for preventing call disconnection that occurs frequently when a terminal in a service area of a repeater moves into a service area of a base station. A method for preventing call disconnection due to movement of a terminal located between a repeater connected to a base station and a base station, the method comprising: obtaining a first signal transmitted from the terminal and received at the base station through the repeater within a demodulation window length (Demod_Win_Len); A first step 601; And a second step (602, 603) for periodically delaying the second signal transmitted from the terminal and received directly to the base station so as to be obtained within the demodulation window length centered on the first signal. In addition, it is possible to prevent a call disconnection caused by the terminal moving the relay period with the base station, thereby improving the call quality, and facilitating the country without limiting the distance between the base station and the relay period.

Code Division Multiple Access, Base Station, Repeater, Demodulation Window Length, Time Delay Value

Description

Apparatus and method for preventing call drop by delaying signal received directly in CDMA system}             

1 is a diagram illustrating a general code division multiple access base station operation;

FIG. 2 is a diagram illustrating a search operation of a base station demodulator searcher when the terminal moves in FIG. 1; FIG.

3 is a block diagram of an apparatus for preventing call disconnection using delay time compensation in a code division multiple access communication system according to the present invention;

4 is a configuration diagram showing an example in which the apparatus of the present invention as shown in FIG. 3 is applied to a receiving apparatus of a CDMA base station;

5 is a view for explaining an example of a delay operation of the signal delay device of FIG. 3;

6 is a flowchart illustrating a call disconnection prevention method using delay compensation of a code division multiple access communication system according to an embodiment of the present invention;

7 is a flowchart illustrating a call disconnection prevention method using delay compensation of a code division multiple access communication system according to another embodiment of the present invention.

※ Explanation of code for main part of drawing

31: A / D Converter 32: Signal Delay

33: D / A converter 34: control unit

35: setting unit

41, 42: local frequency oscillator 43, 46, 49: amplifier

44, 47: Down-converter 45, 48, 51, 53, 56: Filter

52, 54: up converter 55: signal attenuator

The present invention relates to an apparatus and method for preventing call drop using delay compensation of a CDMA communication system. More particularly, the present invention relates to a service area of a base station. The present invention relates to an apparatus and method for preventing call disconnection using delay compensation of a CDMA communication system for preventing a call disconnection phenomenon frequently occurring when moving into a network.

In general, in the CDMA communication system, as shown in FIG. 1, by providing a repeater 13 connected to a base station 12 via a relay line 11, cell coverage is transmitted by transmitting signals of the base station 12 to a long distance. (Cell Coverage) is expanding.

In FIG. 1, the terminals in the service area A of the base station 12 are directly connected to the base station 12 via the path P1 and are talked, and the terminals in the service area B of the repeater 13 are the repeater 13. ) Is indirectly connected to the base station 12 through the path P2 via the relay line 11 and the call.

By the way, when the terminal 14, which is in a call, gradually moves in the service area B of the repeater 13 and enters the service area A of the base station 12, call disconnection frequently occurs. The reason for this is as follows.

The searcher of the base station demodulator operates to find a signal in the demodulated window length (Demod_win_length) centered on the PN offset assigned to the current finger and to assign it to a new finger. Since the strength of the received signal S2 of the base station through the path P2 is greater than the strength of the received signal S1 of the base station through the path P1 when the call is in the repeater service area B, the searcher is shown in FIG. 2 (a). As described above, a new signal is found within the demodulation window length range centering on the signal S2. At this time, although the signal S1 is within the demodulation window length range, the signal S1 is relatively weak compared to the signal S2 and thus is not allocated to the finger.

When the terminal 14 in the repeater service area B moves toward the base station 12, the lengths of the paths P1 and P2 are relatively reduced and increased, thereby as shown in FIG. 2 (b). While the strength of the signal S1 gradually increases, the strength of the signal S2 gradually decreases.

As the terminal 14 moves further into the service area A of the base station 12, as shown in Fig. 2C, the strength of the signal S2 is very weak and the strength of the signal S1 is Since the signal S1 is relatively large, the signal S1 needs to be obtained. In this case, due to the difference in the relative reception time of the signals S1 and S2 due to the mutual length difference between the paths P1 and P2, Since the demodulation window length is out of range, the signal S1 cannot be obtained even though the signal S2 is in a very weak state, and a call disconnection phenomenon occurs.

The above described call disconnection phenomenon is explained by introducing a mathematical equation as follows.

First, the time at which the signal transmitted from the terminal 14 is directly transmitted to the base station 12 (that is, the transmission time of the signal S1 through the path P1) is Td1, and the signal transmitted from the same terminal 14 is the repeater 13. And when the time indirectly transmitted to the base station 12 via the relay line 11 (that is, the transmission time of the signal S2 through the path P2) is Td2, the signal S1 and S2 of the base station 12 The difference Tdif of the relative reception time is shown in Equation 1 below.

 Tdif = Td2-Td1

In addition, in the following Equation 2, a call disconnection phenomenon occurs.

Tdif> (receivable time band) / 2

In Equation 2, the receivable time band refers to a demodulation window length (Demod_win_length). In general, in order to track and demodulate a multipath signal of a terminal caused by a traffic channel of a base station in a traffic state, traffic The demodulation window length (Demod_win_length) should be specified among the parameters related to the channel. In IS-95, the range is set to 0 to 65535 (ie 1/8 chip). This means that if another demodulated multipath signal is present within the demodulation window length in addition to the signal that is currently demodulated within the demodulation window length, even if the current demodulation signal is lost, the call is not demodulated. On the contrary, if the demodulated multipath signal is outside the demodulated window length range and loses the signal currently being demodulated, the traffic channel can no longer find a signal to demodulate and cannot maintain traffic. Disconnection will occur.

Therefore, as described above, when the terminal, which is in a call in the service area B of the repeater, gradually moves into the service area A of the base station and becomes a condition as shown in [Equation 2], the signal S1 having a demodulation strength. Since the demodulation window length is outside the range and the strength of the signal S2 that is currently demodulated is very weak and lost, there is a problem that a call disconnection phenomenon occurs.

The present invention was created to solve the above problems, the object of which is a signal directly received by the base station (hereinafter referred to as a "direct reception signal") and a signal received by the base station through a relay (hereinafter referred to as "indirect reception signal") Code division multiple access communication that compensates for the difference in the reception time relative to the < RTI ID = 0.0 >< / RTI > It is an object of the present invention to provide an apparatus and method for preventing call disconnection using delay compensation of a system.

In order to achieve the above object, a call disconnection prevention apparatus using delay time compensation of a code division multiple access (CDMA) communication system according to the present invention includes a base station and a repeater connected to the base station. An analog / digital (A / D) converting means installed on one path of the base station receiving end and converting an analog received signal into a digital signal; Signal delay means for variable delaying the converted signal; Digital / analog (D / A) converting means for converting the delayed digital signal into an analog signal; Control means for controlling the signal delay means; And setting means for setting a command value for the signal delay.

Thus, the call disconnection prevention device using the delay time compensation of the CDMA communication system according to the present invention is installed on the reception path of the signal (that is, the direct reception signal) transmitted from the terminal and directly received by the base station, and the base station When a terminal located between the repeater and the repeater moves from the repeater side to the base station side, the direct signal is fixed and / or variably delayed and then demodulated, thereby transmitting a signal transmitted from the terminal to the base station through the repeater (that is, In addition, the direct reception signal can be captured within a demodulated window length range centering on the indirect reception signal), thereby preventing call disconnection.

In order to achieve the above object, a call disconnection prevention method using delay time compensation of a CDMA communication system according to the present invention includes a call disconnection caused by movement of a terminal located between a base station and a repeater connected to the base station. A method for preventing a delay, the method comprising: a first step of acquiring a first signal (corresponding to the indirect reception signal) transmitted from the terminal and received to the base station through the repeater within a demodulation window length (Demod_Win_Len); And a second step of periodically delaying a second signal (corresponding to the direct received signal) transmitted from the terminal to the base station so as to be obtained within the demodulation window length centered on the first signal. It consists of steps.

As described above, in the call disconnection prevention method using the delay time compensation of the CDMA communication system according to the present invention, if the first signal is captured within the demodulation window length range, the second signal is periodically delayed to center the first signal. By allowing the demodulation window length to be obtained within the range of the demodulation window length, when the terminal moves from the repeater side to the base station side, the difference between the reception time of the first signal and the second signal is out of the range of the demodulation window length. It can prevent the call disconnection caused.

In order to achieve the above object, a call disconnection prevention method using delay time compensation of a code division multiple access (CDMA) communication system according to another embodiment of the present invention. A method for preventing call disconnection due to movement of a terminal located between a base station and a repeater connected to the base station, the method comprising: a first signal transmitted from the terminal, received by the base station through the repeater, and directly received by the base station; A first step of measuring a difference in the reception time when a call disconnection occurs due to a difference in a relative reception time between signals; A second step of extending a demodulation window length Demod_Win_Len; A third step of analyzing whether the measured difference value of the reception time is within the extended demodulation window length range; And a fourth step of delaying the second signal according to the analysis result so as to be obtained within the demodulation window length centered on the first signal, in particular, the message in the fourth step. The annual value is set so that the difference in the reception time is less than or equal to the value obtained by dividing the demodulation window length by '2'.

As described above, according to a call disconnection prevention method using delay time compensation of a CDMA communication system according to another embodiment of the present invention, the second signal is demodulated after a predetermined time immediately before demodulation, and the first signal is delayed. By immediately demodulating without compensating for the signal, the difference in reception time generated between the first signal and the second signal is compensated for, thereby preventing a call disconnection occurring when the terminal moves from the repeater to the base station.

Hereinafter, an apparatus and method for preventing call disconnection using delay time compensation in a code division multiple access (CDMA) communication system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram of an apparatus for preventing call disconnection using delay time compensation of a CDMA communication system according to the present invention, comprising: an analog-to-digital (A / D) converter 31 for converting an input analog signal into a digital signal; A signal delay unit (32) for variably delaying the digital signal converted by the A / D converter (31); A digital / analog (D / A) converter 33 for converting the digital signal delayed by the signal delay unit 32 into an analog signal; A control unit 34 for controlling a signal delay operation of the signal delay unit 32; And a setting unit 35 for setting command values for the signal delay such as the time delay values t _{min and} t _max and the time delay period T. The control unit 34 controls the delay operation of the signal delay unit 32 according to the setting of the command value through the setting unit 35, and controls the digital signal converted by the A / D converter 31. Control to delay step periodically.

FIG. 4 is a diagram illustrating an example in which the apparatus of the present invention as shown in FIG. 3 is applied to a receiving apparatus of a CDMA base station. In the repeater connected to the base station and the base station via a relay line, the base station and the repeater are busy. As an example, the apparatus of the present invention as shown in FIG. 3 is installed on a reception path for directly receiving a transmission signal of a terminal to the base station.

The receiving device of FIG. 4 comprises: first and second local frequency oscillators 41 and 42 for oscillating frequency; A first amplifier 43 for amplifying the received signal; A first down converter (44) for receiving the oscillation frequency of the first local frequency oscillator (41) and down converting the signal amplified by the first amplifier (43); A first filter (45) for filtering the signal transmitted from the first down converter (44); A second amplifier 46 for amplifying the output signal of the first filter 45; A second down converter (47) for receiving the oscillated frequency from the second local frequency oscillator (42) and down converting the signal amplified by the second amplifier (46); A second filter (48) for filtering the signal down-converted by the second down converter (47); A third amplifier (49) for amplifying the signal transmitted from the second filter (48); An A / D converter 31 for converting the analog signal output from the third amplifier 49 into a digital signal, and a signal delayer for variably delaying the digital signal converted by the A / D converter 31 ( 32, a D / A converter 33 for converting the digital signal delayed by the signal delay unit 32 into an analog signal, a control unit 34 for controlling the signal delay operation of the signal delay unit 32, and A call disconnection prevention device 30 of FIG. 3, comprising a setting unit 35 for setting a command value for the signal delay such as a time delay value t _max and a time delay period T; A third filter (51) for filtering the analog signal output from the D / A converter (33); A first up-converter (52) for receiving an oscillation frequency from the second local frequency oscillator (42) and up-converting the signal filtered by the third filter (51); A fourth filter 53 for filtering the output signal of the first up-converter 52; A second up-converter (54) for receiving the frequency oscillated from the first local oscillator (41) and up-converting the signal transmitted from the fourth filter (53); A signal attenuator (55) for attenuating the signal upconverted by the second upconverter (54); And a fifth filter 56 for filtering the output signal of the signal attenuator 55.

Referring to the operation of the receiving apparatus to which the present invention having the structure as described above is applied as follows.

Since the received signal level of the received 800MHz band is very low, such as -80 to -50dB, the first amplifier 43 amplifies the received signal to sufficiently increase the power to a level of about 30dB. The first down converter 44 mixes a radio frequency signal of the 800 MHz band amplified by the first amplifier 43 with a frequency of about 70 MHz oscillated from the first local frequency oscillator 41, and thus an intermediate frequency of about 70 MHz. Downconvert to band. The first filter 45 filters the signals of the intermediate frequency band of about 70 MHz transmitted from the first down converter 44, where only signals of about ± 2.5 MHz are passed at the center frequency of 70 MHz and other band components are transmitted. Remove The second amplifier 46 amplifies the ± 2.5MHz signal passed through the first filter 45 to a level of 20dB and outputs it to the second down converter 47. The second down converter 47 mixes a ± 2.5 MHz signal transmitted from the second amplifier 216 with a frequency of about 2.3 MHz oscillated from the second local frequency oscillator 42, and thus, intermediate about 2.345 MHz. The frequency signal is output to the second filter 48. The second filter 48 is a low noise filter, and passes only the intermediate frequency band of the signals transmitted from the second down converter 47 and removes the other frequency bands. The third amplifier 49 amplifies and outputs the signal of the intermediate frequency band passing through the second filter 48 at a level of about 3 dB. In this case, the third amplifier 49 is a variable gain amplifier capable of varying the gain and performs a function of compensating for gain loss generated during the mixing process by the first and second down converters 44 and 47. . The A / D converter 31 converts the analog signal transmitted from the third amplifier 49 into a digital signal and outputs it to the signal delay unit 32, and the D / A converter 33 transmits the signal delay unit 32. The digital signal, which is delayed and transmitted through), is converted back into an analog signal and output to the third filter 51. Here, the signal delay unit 32 outputs the digital signal input from the A / D converter 31 periodically or after a fixed delay according to a control signal of the control unit 34. The signal 34 generates the control signal according to a command such as a fixed delay or a variable delay set through the setting unit 35 and a setting value such as a time delay value t _max and a delay period T. The delay operation of the device 32 is controlled. The third filter 51 is delayed as described above and filters the signal converted into the analog signal by the D / A converter 33 to remove signals other than the intermediate frequency band and pass only the intermediate frequency signal. The first up-converter 52 mixes a 2.345 MHz signal transmitted from the third filter 51 with a frequency of about 2.3 MHz oscillated from the second local frequency oscillator 42, thereby mixing a signal of about 70 MHz in a fourth manner. Output to the filter 53. The fourth filter 53 passes only the 70 MHz signal of the output signal of the first up-converter 52 and removes the other frequency band. The second up-converter 54 mixes a signal in the 70 MHz band passing through the fourth filter 53 with a frequency of about 70 MHz oscillated from the first local frequency oscillator 41, and outputs a frequency signal of about 800 MHz. do. The signal attenuator 55 attenuates the signal transmitted from the fourth down converter 54 in order to maintain a signal level of about 3 dB passing through the D / A converter 33 at the same level as the signal level at the time of reception. The fifth filter 56 passes only signals of a desired 800 MHz band among the signals attenuated by the signal attenuator 55 and removes other frequency bands.

As a result, the apparatus of the present invention configured as shown in FIG. 3 is installed on the receiving path of the base station receiving apparatus as shown in FIG. 4, that is, the receiving path of the direct receiving signal, and sets various commands for the signal delay of the setting unit 35. According to a control signal of the control unit 34 according to the control signal by the step variable delay or fixed delay control the direct reception signal input to the base station receiving apparatus periodically, the direct reception within the range of the demodulation window length centered on the indirect reception signal The signal can be captured at any time.

That is, conventionally, as shown in FIG. 2C, when a terminal in communication with the base station is located in the relay period and moves closer to the base station from the repeater, the strength of the direct reception signal S1 is sufficiently large and the indirect reception signal S2 is relatively small. In this case, as the path P1 in FIG. 1 becomes shorter and the path P2 becomes longer, the difference Tdif between the reception time Td2 of the indirect reception signal S2 and the reception time Td1 of the direct reception signal S1 is as shown in [Equation 2]. Since " Tdif > (receivable time band) / 2 ", call disconnection occurs.

In contrast, according to the device of the present invention, the direct reception signal S1 is delayed before the signal of the demodulator is acquired so as to be as shown in Figs. 2 (c) to 2 (d), that is, centered on the indirect reception signal S2. By allowing the direct received signal S1 to fall within a demodulation window length range, the direct disconnected signal S1 having a greater signal strength can be allocated to a new finger to prevent a call disconnection.

On the other hand, under the control of the control unit 34 through the setting unit 35 is changed without fixing the delay value of the signal delay unit 32, as shown in Figure 5 minimum time delay within a certain period (T) By setting the value t _min and the maximum time delay value t _max as the limit value and periodically repeating the increase and decrease delays, the terminal can maintain more accuracy in acquiring the signal of the demodulator and the terminal can provide the base station service area. The advantage of spatial diversity can also be utilized when in an area other than (area A in FIG. 1). The period T, the minimum time delay value t _min , and the maximum time delay value t _max are set through the setting unit 35, and the direct reception signal and the indirect reception according to the distance between the base station and the repeater. It is preferable to set the direct received signal at any time within the demodulated window length range centering on the indirect received signal when the terminal is moved by setting the maximum value and the minimum value of the mutual reception time difference value of the signal. .

FIG. 6 is a flowchart illustrating a call disconnection prevention method using delay time compensation in a code division multiple access communication system according to an embodiment of the present invention. The apparatus shown in FIG. 3 is installed in a receiving apparatus of a base station as shown in FIG. .

In FIG. 6, if the first signal transmitted from the terminal and received through the repeater to the base station is acquired within the demodulated window length Demod_Win_Len (601), the second signal transmitted from the terminal and received directly to the base station periodically In step 602, the second signal is acquired within the demodulation window length range centering on the first signal (603).

7 is a flowchart illustrating a call disconnection prevention method using delay time compensation in a code division multiple access communication system according to another embodiment of the present invention. It is installed and implemented.

In FIG. 7, due to the time delay between the second signal S1 directly received at the base station (or mother station) and the first signal S2 indirectly received at the base station via the repeater (or self station), 2, the signal S1 is confirmed to be disconnected from the reception demodulation range of the base station channel card (701). At this time, the condition that the call disconnection phenomenon is the same as [Equation 1].

When the call disconnection is confirmed, the delay time (difference in reception time) between the second signal S1 serving as the direct reception signal and the first signal S2 serving as the indirect reception signal is measured (702). The length Demod_win_length is extended to the maximum (703), and it is analyzed whether the measured delay time is captured within the maximum extended demodulation window length range (704).

At this time, if the second signal (S1) in the analysis result is not captured within the demodulated window length range, through the setting unit 35 of the signal delay device installed in the second signal receiving end as shown in Figure 4, A time delay value calculated as shown in [] is set (705).

Based on the set time delay value, the control unit 34 controls the signal delay unit 32 so that the second signal is delayed by the time delay value, and thus the first signal S2 and the first signal. The difference in the reception time between the two signals S1 is compensated so that the second signal S1 is captured within the extended demodulation window length centered on the first signal S2, so that the terminal is connected with the base station. When you move, you can maintain a smooth call state.

(Receivable time band) / 2> Tdif

Here, the reception time error Tdif is obtained as shown in Equation 2 above.

The receivable time band is a demodulation window length.

On the other hand, if the delay time between the base station and the repeater in the analysis process 704 is captured within the demodulation window length range, the reception time error can be compensated only by changing the demodulation window length, so that the signal setting unit 35 The delay time is set to '0' so that the first signal is not delayed.

As described in detail above, according to the apparatus and method for preventing call disconnection using delay time compensation in a code division multiple access communication system according to the present invention, between a base station and a repeater connected to the base station via a relay line. It is possible to prevent the call disconnection caused by the terminal moving the relay period with the base station, thereby improving call quality, and facilitating the country without limiting the distance between the base station and the relay period.

Claims (10)

delete delete delete delete In the call disconnection prevention method using the delay time compensation of the terminal located between the base station and the repeater connected to the base station, A first step of acquiring a first signal transmitted from the terminal and received through the repeater to the base station within a demodulation window length range; And And a second step of delaying the second signal transmitted from the terminal and directly received by the base station, so that the second signal is obtained within the demodulation window length centered on the first signal. Call disconnection prevention method using delay time compensation in code division multiple access communication system. The method of claim 5, wherein In the second step, the second signal is delayed by a time corresponding to a signal arrival time difference according to a difference in length of a reception path between the first signal and the second signal. Method for preventing call disconnection using time compensation. The method of claim 5, wherein In the second step, the second signal is delayed according to the delay value while varying the delay value of the second signal within a predetermined range. Call disconnection using delay time compensation of a code division multiple access communication system Prevention method. The method of claim 7, wherein And the predetermined range is set based on a maximum value and a minimum value of a difference value of a reception time difference between the first signal and the second signal. In a call disconnection method of a terminal located between a base station and a repeater connected to the base station, Measuring a difference in the reception time when a call disconnection occurs due to a difference in a relative reception time between the first signal received from the terminal and the second signal directly received by the base station through the repeater; Stage 1; A second step of extending a demodulation window length for detecting a received signal; A third step of analyzing whether the measured difference value of the reception time is within the extended demodulation window length range; And And a fourth step of delaying the second signal according to the analysis result so that the second signal is obtained within the demodulation window length centered on the first signal. Method for preventing call disconnection using time compensation. The method of claim 9, The time delay value in the fourth step is set so that the difference in the reception time is equal to or less than a value obtained by dividing the demodulation window length by '2'. How to prevent disconnection.

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