JP4438037B2 - Base station and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an initial synchronization acquisition method in a base station of a CDMA cellular system.
[0002]
[Prior art]
In a CDMA cellular system, a base station and a plurality of mobile stations communicate using the same frequency band. Each mobile station is identified by a spreading code determined for each mobile station. Therefore, the base station needs to demultiplex the received signal received from each mobile station by despreading using a spreading code determined for each mobile station. In this despreading process, the correlation detection process between the received signal and the spread code replica is the most important process. In this correlation detection process, the correlation calculation result calculated by the correlator is compared with a predetermined threshold value for each phase within the synchronization acquisition phase range. Done by selecting as. The threshold value used here is usually a preset threshold value.
[0003]
[Problems to be solved by the invention]
However, since a preset threshold value has been conventionally used, problems to be solved as described below remain.
1. When the noise floor is high, the wrong position is set as a synchronization position candidate, so that the probability of losing the transmission wave from the mobile station increases. As a result, the connection rate with the mobile station decreases.
2. If the correlation threshold is set high in order to avoid the above-described adverse effects, the mobile station is requested to transmit more transmission power than necessary, making it difficult to effectively use uplink radio channel resources.
[0004]
[Means for Solving the Problems]
The present invention adopts the following configuration in order to solve the above points.
<Configuration 1>
A code replica generator for outputting a replica spreading code for multiplying the received signal; a correlation calculator for calculating a correlation power value and its synchronization position based on a despread value obtained by multiplying the received signal by the replica spreading code; and the correlation A searcher that determines a correlation power value equal to or greater than a threshold value as a synchronization position candidate based on the correlation power value and the synchronization position from a computing unit, and a spread code based on the synchronization position candidate and the synchronization position from the searcher A code generator that outputs, a correlator that multiplies the spread code from the code generator and the received signal and outputs a despread value of the received signal, and decodes the despread value from the correlator, A decoding unit that calculates and outputs a data error rate of the data obtained by decoding, and a control unit that controls a synchronization acquisition operation in the base station, and the control unit sets the total received power amount of the received signal to Zui with a correlation threshold setting means for setting the threshold, the correlation threshold value changing means for re-setting of the threshold value when the searcher monitoring the searcher can not determine the synchronization position candidates within a predetermined time, said decoding And a synchronization position candidate changing means for controlling the searcher to change the synchronization position candidate when the data error rate does not reach a predetermined value within a predetermined time.
[0005]
<Configuration 2>
In place of the synchronization position candidate changing means of the base station described in the above configuration 1, a correlation threshold value adjusting means for adding a predetermined value to the threshold value when the data error rate of the decoding unit does not reach the predetermined value within a predetermined time is provided. A base station characterized by that.
[0006]
<Configuration 3>
In the base station according to Configuration 1 or Configuration 2, the control unit has a conversion table in which the threshold value corresponding to the total received power amount of the received signal is preset. Base station.
[0007]
<Configuration 4>
In the base station according to Configuration 3, the control unit includes a conversion table rewriting unit that rewrites the threshold value set in the conversion table based on a threshold value when synchronization acquisition is successful. Base station.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described using specific examples.
<Configuration of Specific Example 1>
FIG. 1 is a block diagram of the first specific example.
As shown in FIG. 1, the initial synchronization acquisition method in the CDMA base station of the first specific example includes an antenna 1, a radio device 2, an A / D (analog / digital) converter 3, a code replica generator 4, and a multiplier 5. A correlation calculator 6, a searcher 7, a code generator 8, a correlator 9, a rake combiner 10, a decoding unit 11, and a control unit 12.
[0009]
The antenna 1 is a part that receives electromagnetic waves from a wireless line and converts them into high-frequency received signals.
The radio 2 is a part that receives a high-frequency received signal from the antenna 1 and converts it into a baseband received signal.
The A / D (analog / digital) converter 3 is a part that receives the received signal converted from the wireless device 2 into the baseband, converts it into a digital signal, and outputs the digital received signal.
[0010]
The code replica generator 4 is a part that receives spread code information from a searcher 7 described later and outputs a replica spread code. This is a part for calculating the correlation power value and its synchronization position in combination with the correlation calculator 6 described later while changing the phase of the replica spreading code.
The multiplier 5 is a part that receives the digital reception signal from the A / D converter 3 and multiplies the replica spread code received from the code replica generator 4 to output a despread value.
[0011]
The correlation calculator 6 is a part that receives the despread value from the multiplier 5 and calculates the correlation power value and the synchronization position together with the code replica generator 4.
The searcher 7 sends the spread code information and its phase information to the code replica generator 4, receives the correlation power value and the synchronization position from the correlation calculator 6, and sets the correlation power value equal to or greater than a predetermined threshold as the synchronization position candidate. It is a part to decide.
[0012]
The code generator 8 is a part that receives the synchronization position candidate and the synchronization position from the searcher 7 and outputs a spread code.
The correlator 9 is a part that multiplies the spread code received from the code generator 8 and the digital reception signal received from the A / D converter 3 to output a despread value.
A plurality of code generators 8 and correlators 9 are usually arranged.
[0013]
A rake combiner 10 is a part that receives despread values from the plurality of correlators 9 and receives a rake.
The decoding unit 11 accepts the despread value received by the rake from the rake combiner 10 and outputs the decoded received data, and calculates and outputs the data error rate of the received data for each radio frame. It is a part to do.
[0014]
The control unit 12 is a part that receives the data error rate of the received data from the decoding unit 11 and controls the initial synchronization acquisition operation in the base station. The controller 12 detects the total received power value E0 of the digital received signal from the A / D converter 3, and the initial correlation required when the searcher 7 detects the synchronization position candidate based on the detection result. An initial correlation threshold value setting means for setting the threshold value T; a correlation threshold value changing means for monitoring the searcher 7 and resetting the initial correlation threshold value T when the searcher 7 cannot detect a synchronization position candidate within a predetermined time; and the decoding unit 11 And a synchronization position candidate changing means for controlling the searcher 7 to change the synchronization position candidate when the data error rate is accepted and the predetermined value cannot be reached at a predetermined time. These means will be described in detail in the following description of the operation.
[0015]
<Operation of Specific Example 1>
First, the basic principle of the initial synchronization acquisition method in the CDMA base station of the present invention will be described with reference to the drawings.
FIG. 2 is an explanatory view of the basic principle of the present invention.
(A) represents the initial correlation threshold when the noise floor is high.
(B) represents the initial correlation threshold when the noise floor is low.
[0016]
From (a), the level of the noise floor 22 is estimated as the total received power value E0 currently received by the base station. A level obtained by adding α to the total received power value E0 is set as the initial correlation threshold T23. This plus α is set in advance from an actual measurement value or the like, and the value is stored in a conversion table possessed by the control unit 12 (FIG. 1).
The matters to be noted here are as follows.
If the initial correlation threshold value T is an inappropriate threshold value 24, it becomes difficult to distinguish between the transmission power 21 of the mobile station and noise, and it becomes difficult to select synchronization position candidates.
[0017]
From (b), if the initial correlation threshold T23 is set to the same level as in (a) when the level of the noise floor 22 is low, the excess power 25 becomes large and it is difficult to effectively use radio channel resources.
Therefore, in specific example 1, the operation is started by setting an appropriate initial correlation threshold T based on the noise floor (total power value E) at the beginning of the synchronization acquisition operation. The operation will be described in detail below.
[0018]
FIG. 3 is an operation explanatory diagram of the first specific example.
The figure shows the operation of the initial synchronization acquisition method in the CDMA base station of the first specific example using a flowchart.
Hereinafter, the operation of the initial synchronization acquisition method in the CDMA base station of the first specific example will be described according to steps S1 to S12 of the flowchart.
[0019]
Step S1
The base station starts initial synchronization acquisition.
Step S2
The controller 12 (FIG. 1) reads the total received power value E0 currently received by the base station from the A / D converter 3 (FIG. 1).
[0020]
Step S3
The control unit 12 (FIG. 1) determines an initial correlation threshold T from the read total received power value E0. In the determination, the total received power value E0 is determined based on a conversion table stored in a memory possessed by the control unit 12 (FIG. 1). The total received power value E0 is treated as a noise floor level. The initial correlation threshold value T is set to a level appropriate for the noise floor level. That is, the value is set so as not to miss the received signal from the mobile station.
Steps S2 and S3 are defined as the initial correlation threshold value determining means of the control unit 12 (FIG. 1).
[0021]
Step S4
The controller 12 (FIG. 1) instructs the searcher 7 on the determined initial correlation threshold T.
Step S5
The control unit 12 (FIG. 1) instructs the searcher 7 to start synchronization acquisition.
[0022]
Step S6
The control unit 12 (FIG. 1) waits for a synchronization acquisition completion report from the searcher 7 (FIG. 1). If there is no report, the control unit 12 proceeds to step S7. Repeat S7. If there is a report, the process jumps to step S8.
Step S7
The control unit 12 (FIG. 1) starts the report timer, and when there is no report within a predetermined time (n seconds) (timer timeout), the control unit 12 (step S11) exits to step S11 and starts again from step S1.
Steps S6, S7, and S11 are defined as the correlation threshold value changing means of the control unit 12 (FIG. 1).
[0023]
Step S8
The control unit 12 (FIG. 1) monitors the data error rate (CRC) reported from the decoding unit 11 (FIG. 1).
Step S9
If the control unit 12 (FIG. 1) monitors the data error rate (CRC) and confirms that synchronization can be ensured at the correct synchronization position, the control unit 12 proceeds to step S12 to complete synchronization acquisition. If it cannot be confirmed from the rate (CRC) that synchronization has been secured at the synchronization position, that is, if the data error rate (CRC) cannot achieve a predetermined value, the process proceeds to step S10.
[0024]
Step S10
When the controller 12 (FIG. 1) cannot confirm that the synchronization has been secured at the correct synchronization position from the data error rate (CRC) within a predetermined time (m seconds) after starting the timer, the control unit 12 sets a timer timeout. Step S8 is repeated until Step S8 is reached and the timer times out.
If the timer has timed out, the process returns to step S5 and instructs the searcher 7 (FIG. 1) to acquire synchronization again. However, the initial correlation threshold T is not changed in the synchronization acquisition here.
[0025]
In the middle of step S7, the report timer is started in the same manner as described above, and if there is no report within a predetermined time (n seconds) (timer timeout), the process returns to step S11.
Steps S8, S9, and S10 are defined as the synchronization position candidate changing means of the control unit 12 (FIG. 1).
[0026]
Step S11
The control unit 12 (FIG. 1) determines that the synchronization acquisition has failed because the data error rate (CRC) cannot achieve a predetermined value within a predetermined time (n seconds), and returns to step S1 to acquire synchronization again. Try again. That is, the initial correlation threshold T is also reset here.
While repeating the above operation, in step S9, the control unit 12 reports a predetermined data error rate (CRC) from the decoding unit 11 (FIG. 1) and confirms that synchronization has been secured at the correct synchronization position. Proceeding to step S12, the synchronization acquisition is completed.
Step S12
Complete synchronization acquisition.
[0027]
<Effect of specific example 1>
With the configuration and operation described above, the initial synchronization acquisition method in the CDMA base station of Example 1 obtains the following effects.
1. Even when the noise floor is high, since the correlation threshold is set based on the noise floor, the probability that an incorrect position is set as a synchronization position candidate decreases, and the probability that a signal from a mobile station can be captured increases.
2. Further, when the noise floor is low, the correlation threshold is set based on the noise floor, so that the mobile station is requested to have the minimum necessary transmission power, and the uplink radio channel resources can be effectively used.
[0028]
<Specific example 2>
Since the configuration of the initial synchronization acquisition method in the CDMA base station of the second specific example is the same as that of the first specific example, a description thereof will be omitted and only the operation will be described.
FIG. 4 is an operation explanatory diagram of the second specific example.
The figure shows the operation of the initial synchronization acquisition method in the CDMA base station of the specific example 2 using a flowchart.
[0029]
In the initial synchronization acquisition method in the CDMA base station of Example 2, when the control unit (FIG. 1) monitors the data error rate (CRC) and determines that synchronization is secured at an incorrect synchronization position, the initial correlation threshold T is set in advance. A value obtained by adding a predetermined value β (T = T + β) is instructed to the searcher 7 (FIG. 1) as a new correlation threshold, and then a resynchronization acquisition instruction is instructed to the searcher 7 (FIG. 1). Details of the operation will be described below.
[0030]
Step S1
The base station starts initial synchronization acquisition.
Step S2
The controller 12 (FIG. 1) reads the total received power value E0 currently received by the base station from the A / D converter 3 (FIG. 1).
[0031]
Step S3
The control unit 12 (FIG. 1) determines an initial correlation threshold T from the read total received power value E0. In the determination, the total received power value E0 read from the A / D converter 3 (FIG. 1) is determined based on a conversion table stored in a memory held by the control unit 12 (FIG. 1). The total received power value E0 is treated as a noise floor level. The initial correlation threshold value T is set to a level appropriate for the noise floor level. That is, the value is set so as not to miss the transmission wave from the mobile station.
Steps S2 and S3 are defined as the initial correlation threshold value determining means of the control unit 12 (FIG. 1).
[0032]
Step S4
The control unit 12 (FIG. 1) notifies the searcher 7 of the determined initial correlation threshold T.
Step S5
The control unit 12 (FIG. 1) instructs the searcher 7 to start synchronization acquisition.
[0033]
Step S6
The control unit 12 (FIG. 1) waits for a synchronization acquisition completion report from the searcher 7 (FIG. 1). If there is no report, the control unit 12 proceeds to step S7. Repeat S7. If there is a report, the process jumps to step S8.
Step S7
The control unit 12 (FIG. 1) starts the report timer, and when there is no report within a predetermined time (n seconds) (timer timeout), the control unit 12 exits to step S11 and starts again from step S1.
Steps S6, S7, and S11 are defined as the correlation threshold value changing means of the control unit 12 (FIG. 1).
[0034]
Step S8
The control unit 12 (FIG. 1) monitors the data error rate (CRC) reported from the decoding unit 11 (FIG. 1).
Step S9
When the predetermined data error rate (CRC) is reported from the decoding unit 11 (FIG. 1) and the control unit 12 (FIG. 1) confirms that synchronization has been secured at the correct synchronization position, the control unit 12 (FIG. 1) proceeds to step S12 and performs synchronization. If the acquisition is completed but it cannot be confirmed from the data error rate (CRC) that synchronization has been secured at the synchronization position, that is, if the data error rate (CRC) cannot achieve a predetermined value, the process proceeds to step S10.
[0035]
Step S10
When the controller 12 (FIG. 1) cannot confirm that the synchronization has been secured at the correct synchronization position from the data error rate (CRC) within a predetermined time (m seconds) after starting the timer, the control unit 12 sets a timer timeout. Until it becomes, it returns to step S8 and repeats step S8-step S10.
If the timer times out here, the process proceeds to step S13.
Steps S8, S9, and S10 are defined as synchronization position candidate changing means.
[0036]
Step S13
The control unit 12 (FIG. 1) determines a value T = T + β, which is obtained by increasing the initial correlation threshold T by a predetermined value β when it is determined that synchronization has been secured at an incorrect synchronization position in step S8 as a new correlation threshold. To the searcher 7 (FIG. 1), and the process returns to step S4. The initial correlation threshold T here is T + β.
In the middle of step S7, the report timer is started in the same manner as described above, and if there is no report within a predetermined time (n seconds) (timer timeout), the process returns to step S11.
[0037]
Step S11
The control unit 12 (FIG. 1) determines that synchronization acquisition has failed because there is no report within a predetermined time (n seconds), returns to step S1, and performs synchronization acquisition again. That is, the initial correlation threshold T is also reset here.
While repeating the above operation, in step S9, the control unit 12 reports the data error rate (CRC) from the decoding unit 11 (FIG. 1) and confirms that synchronization has been secured at the correct synchronization position, and then proceeds to step S12. Go ahead and complete synchronization acquisition.
[0038]
Step S12
The control unit 12 (FIG. 1) completes the synchronization acquisition.
[0039]
<Effect of specific example 2>
With the configuration and operation described above, the initial synchronization acquisition method in the CDMA base station of the specific example 2 obtains the following effects.
1. Even if the noise floor changes during acquisition, the correlation threshold is set based on the changed noise floor, so the probability that an incorrect position is a synchronization position candidate is reduced, and the probability that a signal from a mobile station can be acquired is high. Become.
2. In addition, when the noise floor is low, the correlation threshold is set based on the noise floor after the fluctuation, so that the mobile station is required to have the minimum transmission power required, so it is possible to effectively use uplink radio channel resources. .
[0040]
<Specific example 3>
Since the configuration of the initial synchronization acquisition method in the CDMA base station of the third specific example is the same as that of the first specific example, a description thereof will be omitted and only the operation will be described.
FIG. 5 is an operation explanatory diagram (part 1) of the third specific example.
FIG. 6 is an operation explanatory diagram (part 2) of the third specific example.
The figure shows the operation of the initial synchronization acquisition method in the CDMA base station of the specific example 3 using a flowchart.
6A shows the correlation threshold value adjustment operation connected to FIG. 5, and FIG. 6B shows the conversion table.
[0041]
In Specific Example 1 and Specific Example 2, the conversion table used when determining the initial correlation threshold T from the total received power value E0 is fixed. Therefore, it may be assumed that the content of the conversion table is not optimal in a wireless line that is long in time. In such a case, the specific example 3 employs a method of reflecting the correlation threshold when the initial synchronization acquisition is successful in the conversion table. Details of the operation will be described below.
[0042]
Step S1
The base station starts initial synchronization acquisition.
Step S2
The controller 12 (FIG. 1) reads the total received power value E0 currently received by the base station from the A / D converter 3 (FIG. 1).
Step S3
The control unit 12 (FIG. 1) determines an initial correlation threshold T from the read total received power value E0. In the determination, the total received power value E0 is determined based on a conversion table stored in a memory possessed by the control unit 12 (FIG. 1). The total received power value E0 is treated as a noise floor level. The initial correlation threshold value T is set to a level appropriate for the noise floor level. That is, the value is set so as not to miss the transmission wave from the mobile station.
Steps S2 and S3 are defined as the initial correlation threshold value determining means of the control unit 12 (FIG. 1).
[0043]
Step S4
The controller 12 (FIG. 1) instructs the searcher 7 on the determined initial correlation threshold T.
Step S5
The control unit 12 (FIG. 1) instructs the searcher 7 to start synchronization acquisition.
[0044]
Step S6
The control unit 12 (FIG. 1) waits for a synchronization acquisition completion report from the searcher 7 (FIG. 1). If there is no report, the control unit 12 proceeds to step S7. Repeat S7. If there is a report, the process jumps to step S8.
Step S7
The control unit 12 (FIG. 1) starts the report timer, and when there is no report within a predetermined time (n seconds) (timer time-out), the control unit 12 (step S12) exits.
Steps S6, S7, and S12 are defined as the correlation threshold value changing means of the control unit 12 (FIG. 1).
[0045]
Step S8
The control unit 12 (FIG. 1) monitors the data error rate (CRC) reported from the decoding unit 11 (FIG. 1).
Step S9
When the predetermined data error rate (CRC) is reported from the decoding unit 11 (FIG. 1) and the control unit 12 (FIG. 1) confirms that synchronization has been secured at the correct synchronization position, the control unit 12 (FIG. 1) proceeds to step S13 to perform conversion. If the table is rewritten, but it cannot be confirmed from the data error rate (CRC) that synchronization at the synchronization position has been secured, that is, if the predetermined data error rate (CRC) is not reported, the process proceeds to step S10.
Steps S8, S9, and S10 are defined as synchronization position candidate changing means.
[0046]
Step S10
When the controller 12 (FIG. 1) cannot confirm that the synchronization has been secured at the correct synchronization position from the data error rate (CRC) within a predetermined time (m seconds) after starting the timer, the control unit 12 sets a timer timeout. Until it becomes, it returns to step S8 and repeats step S8-step S10.
If the timer has timed out, the process proceeds to step S12.
[0047]
Step S12
When the control unit 12 (FIG. 1) determines that synchronization has been secured at the wrong synchronization position in step S8, the value T = T + β, which is increased by β to the initial correlation threshold T, is determined as a new correlation threshold and the searcher 7 (FIG. 1). 1) and return to step S4. The initial correlation threshold T here is T + β.
In the middle of step S7, the report timer is started in the same manner as described above, and if there is no report within a predetermined time (n seconds) (timer timeout), the process returns to step S11.
[0048]
Step S11
The control unit 12 (FIG. 1) determines that the synchronization acquisition has failed because the data error rate (CRC) cannot achieve a predetermined value within a predetermined time (n seconds), and returns to step S1 to acquire synchronization again. Try again. That is, the initial correlation threshold T is also reset here.
While repeating the above operation, in step S9, the control unit 12 reports a predetermined data error rate (CRC) from the decoding unit 11 (FIG. 1) and confirms that synchronization can be secured at the correct synchronization position. Proceed to S13.
[0049]
Step S13
The controller 12 (FIG. 1) measures the total received power value E1 from the A / D converter 3.
Step S14
The control unit 12 (FIG. 1) determines that the total received power value E0 measured at the beginning of the operation (step S2) and the total received power value E1 measured when the synchronization ensuring is completed (the correlation threshold at this time is TI) are converted into the conversion table. If it is determined that they are treated as the same condition, the process proceeds to step S15. If it is determined that they are not treated as the same condition, the process proceeds to step S16 to complete the synchronization acquisition. An outline of this determination method will be described with reference to FIG.
[0050]
From (b), the total received power value Et is ranked at a predetermined stage (i rank in the figure), and the initial correlation threshold is also ranked T0 to Ti corresponding to this ranking. The determination in step S14 is a determination of whether or not the total received power value E0 and the total received power value E1 may be included in the same rank. That is, when the total received power value E0 measured at the beginning of the operation (step S2) is Et + Δi ≦ E0 ≦ Et + Δi + 1, the initial correlation threshold is Ti from the conversion table. At this time, if the total received power value E1 satisfies Et + Δi ≦ E1 ≦ Et + Δi + 1, it is determined that the total received power value E0 and the total received power value E1 are treated as the same condition in the conversion table. Similarly, when Et + Δi ≦ E0 ≦ Et + Δi + 1, if Et + Δi ≦ E1 ≦ Et + Δi + 1 is not satisfied, it is determined that the total received power value E0 and the total received power value E1 are not treated as the same condition in the conversion table. The description of the operation is continued according to the flowchart again.
[0051]
Step S15
The total received power value E0 measured at the beginning of the operation (step S2) and the total received power value E1 measured when the synchronization securing is completed are values treated as the same condition in the conversion table. Therefore, the control unit 12 (FIG. 1) replaces Ti in the conversion table with TI, and then proceeds to step S16 to end synchronization acquisition.
Steps S13, S14, and S15 are defined as conversion table rewriting means of the control unit 12 (FIG. 1).
Step S16
The control unit 12 (FIG. 1) ends the synchronization acquisition.
[0052]
<Effect of specific example 3>
With the configuration and operation described above, the initial synchronization acquisition method in the CDMA base station of the specific example 2 obtains the following effects.
1. Even if a change in radio channel conditions (not instantaneous change) occurs on a relatively long time axis, the conversion table is automatically updated and the optimum parameters can be used at all times, so the initial synchronization acquisition rate is high. To stabilize.
2. Since the parameters in the conversion table can be automatically adjusted to optimum values, even if a change in radio channel conditions occurs on a relatively long time axis, the mobile station is requested to have the minimum required transmission power at that time. Therefore, it is possible to effectively use uplink radio channel resources.
[Brief description of the drawings]
FIG. 1 is a block diagram of a configuration of a specific example 1;
FIG. 2 is a diagram illustrating the basic principle of the present invention.
FIG. 3 is an operation explanatory diagram of specific example 1;
FIG. 4 is an operation explanatory diagram of a specific example 2;
FIG. 5 is an operation explanatory diagram (part 1) of a specific example 3;
FIG. 6 is an operation explanatory diagram (part 2) of the specific example 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Antenna 2 Radio | wireless machine 3 A / D converter 4 Code replica generator 5 Multiplier 6 Correlation computing unit 7 Searcher 8 Code generator 9 Correlator 10 Lake combiner 11 Decoding part

Claims (6)

A code replica generator for outputting a replica spreading code for multiplying the received signal;
A correlation calculator that calculates a correlation power value and its synchronization position based on a despread value obtained by multiplying a received signal by a replica spreading code;
A searcher that determines a correlation power value equal to or greater than a threshold value as a synchronization position candidate based on the correlation power value from the correlation calculator and the synchronization position;
A code generator for outputting a spreading code based on the synchronization position candidate and the synchronization position from the searcher;
A correlator that multiplies the spread code from the code generator by the received signal and outputs a despread value of the received signal;
A decoding unit that decodes the despread value from the correlator, calculates and outputs a data error rate of the data obtained by decoding, and
A control unit for controlling the synchronization acquisition operation in the base station,
The controller is
Correlation threshold setting means for setting the threshold based on the total received power amount of the received signal;
A correlation threshold value changing means for re-setting of the threshold value when the searcher monitoring the searcher can not determine the synchronization position candidates within a predetermined time,
Synchronization position candidate changing means for controlling the searcher to change the synchronization position candidate when a data error rate does not reach a predetermined value within a predetermined time from the decoding unit;
A base station comprising: A code replica generator for outputting a replica spreading code for multiplying the received signal;
A correlation calculator that calculates a correlation power value and its synchronization position based on a despread value obtained by multiplying a received signal by a replica spreading code;
A searcher that determines a correlation power value equal to or greater than a threshold value as a synchronization position candidate based on the correlation power value from the correlation calculator and the synchronization position;
A code generator for outputting a spreading code based on the synchronization position candidate and the synchronization position from the searcher;
A correlator that multiplies the spread code from the code generator by the received signal and outputs a despread value of the received signal;
A decoding unit that decodes the despread value from the correlator, calculates and outputs a data error rate of the data obtained by decoding, and
A control unit for controlling the synchronization acquisition operation in the base station,
The controller is
Correlation threshold setting means for setting the threshold based on the total received power amount of the received signal;
A correlation threshold value changing means for re-setting of the threshold value when the searcher monitoring the searcher can not determine the synchronization position candidates within a predetermined time,
Correlation threshold value adjusting means for adding a predetermined value to the threshold value when a data error rate from the decoding unit does not reach a predetermined value within a predetermined time;
A base station comprising: In the base station according to claim 1 or 2,
The controller is
A base station characterized by holding a conversion table in which the threshold value corresponding to the total received power amount of the received signal is set in advance. In the base station according to claim 3,
The controller is
A base station comprising conversion table rewriting means for rewriting the threshold value set in the conversion table based on a threshold value when synchronization acquisition is successful. A code replica generator for outputting a replica spreading code for multiplying the received signal; a correlation calculator for calculating a correlation power value and its synchronization position based on a despread value obtained by multiplying the received signal and the replica spreading code; Based on the correlation power value from the correlation calculator and the synchronization position, a searcher that determines a correlation power value equal to or greater than a threshold as a synchronization position candidate, and based on the synchronization position candidate and the synchronization position from the searcher A code generator that outputs a spreading code; a correlator that multiplies the spreading code from the code generator by the received signal and outputs a despread value of the received signal; and decodes the despread value from the correlator A base station control method comprising: a decoding unit that calculates and outputs a data error rate of data obtained by decoding; and a control unit that controls a synchronization acquisition operation in the base station,
The controller is
A correlation threshold setting step for setting the threshold based on the total received power amount of the received signal;
A correlation threshold value changing step of re-setting of the threshold value when the searcher monitoring the searcher can not determine the synchronization position candidates within a predetermined time,
When the data error rate from the decoding unit does not reach a predetermined value within a predetermined time, a synchronous position candidate changing step of controlling the searcher to change the synchronous position candidate;
A base station control method comprising: A code replica generator for outputting a replica spreading code for multiplying the received signal; a correlation calculator for calculating a correlation power value and its synchronization position based on a despread value obtained by multiplying the received signal and the replica spreading code; Based on the correlation power value from the correlation calculator and the synchronization position, a searcher that determines a correlation power value equal to or greater than a threshold as a synchronization position candidate, and based on the synchronization position candidate and the synchronization position from the searcher A code generator that outputs a spreading code; a correlator that multiplies the spreading code from the code generator by the received signal and outputs a despread value of the received signal; and decodes the despread value from the correlator A base station control method comprising: a decoding unit that calculates and outputs a data error rate of data obtained by decoding; and a control unit that controls a synchronization acquisition operation in the base station,
The controller is
A correlation threshold setting step for setting the threshold based on the total received power amount of the received signal;
A correlation threshold value changing step of re-setting of the threshold value when the searcher monitoring the searcher can not determine the synchronization position candidates within a predetermined time,
A correlation threshold adjustment step of adding a predetermined value to the threshold when a data error rate from the decoding unit does not reach a predetermined value within a predetermined time;
A base station control method comprising:

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