JP2000224076A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the computing amount of a CDMA receiver by improving the noise suppressing effect at the detection of the peak of a delay profile. SOLUTION: A correlation value calculating section 104 multiplies regularly received signals, while shifting the phase by an already known diffusion code which is the output of a diffusion code generating section 103, and an absolute value calculating section 105 calculates the absolute values of the calculated correlation values at every phase. Then an extracting section 106 extracts the absolute values of the correlative values which exceed a prescribed value, and an averaging section 107 detects a delay profile by adding up and averaging the extracted absolute values by the amount corresponding to a prescribed number of periods. Finally, a peak-detecting section 108 detects the phase, when the maximum correlative value is detected in the delay profile.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a receiving device,
In particular, code division multiple access (Code Division)
n Multiplex Access;
A) The present invention relates to a receiving device for performing communication of the type A) and a method for acquiring the synchronization thereof.

[0002]

2. Description of the Related Art In a communication using the CDMA system, a receiving station can demodulate a signal spread and transmitted by a spreading code at a transmitting station by performing despreading processing in phase with the transmitting station. Therefore, before performing data communication, it is necessary to detect the timing at which the known spread code should be multiplied with the received signal in order to synchronize the data demodulation.

In order to detect the above timing, a known spread code is multiplied by a received signal while shifting the phase, and it is detected to what extent the phase is shifted to obtain a cross-correlation. This process is called synchronization acquisition.

A conventional receiver for performing such synchronization acquisition is described in, for example, Japanese Patent Application Laid-Open No. 2-11033.

Hereinafter, the above-mentioned conventional receiving apparatus will be described with reference to FIG. FIG. 6 is a main block diagram showing a schematic configuration of a conventional receiving apparatus.

In FIG. 6, a reception signal transmitted from a communication partner station is received by an antenna 601, input to a radio reception section 602, and converted into a baseband signal by the radio reception section 602.

[0007] The baseband signal is despread by the correlation value calculation unit 603 at regular intervals using the same spreading code generated by the spreading code generation unit 604 and used by the transmitting station. And a correlation value is calculated. The correlation value calculation unit 603 is, for example, a matched filter and a sliding correlator.

[0008] The calculated correlation value is calculated by an absolute value calculation unit 605.
Calculates the absolute value of the correlation value. The calculated absolute value of the correlation value takes the maximum value when it is in the same phase as the spread code at the time of transmission at which the peak of the correlation value is detected, and is close to 0 in other phases where no peak is obtained as a result of the despreading process. Becomes

However, when the state of the propagation path is poor, a relatively large correlation value is observed due to the influence of noise and fading even if the phase is not the same as that of the spreading code at the time of spreading processing on the transmitting side. In order to eliminate this effect, the calculated absolute value of the correlation value is averaged by the averaging unit 606 between correlation values of the same phase in a plurality of cycles (hereinafter, referred to as in-phase averaging processing), and each position in the plurality of cycles is averaged. A delay profile consisting of the average correlation value of the phases is detected.

In the detected delay profile, a peak of the delay profile is detected by a peak detecting section 607. The phase at which the peak is detected is determined to be the correct timing, and when demodulation is performed, despreading is performed based on the timing.

As described above, the conventional receiving apparatus suppresses noise components by performing in-phase averaging of correlation values of a plurality of periods when detecting a delay profile.

[0012]

However, in the conventional receiving apparatus, since the averaging process is performed using all the amplitudes of the correlation values, it is necessary to perform the averaging process over a plurality of periods due to the influence of noise and fading on the propagation path. When noise concentrates on a specific phase, there is a possibility that a peak may occur, and there is a problem that an erroneous spreading code phase is detected.

Further, since the averaging process is performed by using all the absolute values of the correlation values, there is a problem that the amount of calculation in the averaging unit is large and the hardware scale becomes large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a receiving apparatus capable of improving a noise suppressing effect at the time of detecting a peak of a delay profile and reducing a calculation amount. .

[0015]

The gist of the present invention is that the in-phase averaging process is performed using only a correlation value whose absolute value of a correlation value between a received signal and a known spread code exceeds a predetermined threshold value. In this case, a delay profile is created and peak detection is performed, thereby simultaneously improving the noise suppression effect and reducing the calculation amount.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A receiving apparatus according to a first aspect of the present invention comprises: a receiving means for receiving a signal spread by a spreading code; A correlation value calculating means for calculating a correlation value for each phase by multiplying a spreading code while shifting the phase, and a correlation value whose absolute value exceeds a predetermined value among correlation values at each phase within the unit period. An extracting means for extracting, an averaging means for integrating the absolute value of the extracted correlation value for a predetermined period for each phase in the unit cycle, averaging the sum, and detecting a delay profile; Phase detecting means for detecting the phase at the time of detecting the maximum correlation value in the profile.

According to this configuration, only the correlation value whose absolute value of the correlation value between the received signal and the known spreading code exceeds a predetermined threshold value so that the delay profile does not include a noise component. The in-phase averaging process prevents new peaks due to noise components, improves the accuracy of peak detection in the delay profile, and eliminates the effects of propagation path noise and fading even when they are large. can do. Further, since the amount of calculation required for detecting the delay profile can be reduced, the hardware scale can be reduced.

A receiving apparatus according to a second aspect of the present invention, in the first aspect, further comprises a threshold value setting means for setting the predetermined value in the extracting means, and the averaging means comprises: Before the predetermined period is performed, an averaging process is performed to detect a provisional delay profile, and the phase detection unit detects a maximum correlation value in the provisional delay profile and outputs the maximum correlation value to the threshold value setting unit, The threshold value setting means adopts a configuration in which the predetermined value is determined for the extracting means based on a maximum correlation value of the provisional delay profile.

According to this configuration, the threshold value is adaptively changed according to the propagation environment, so that more correlation values are regarded as noise components and removed, and then the delay profile is created. 1, the noise suppression effect can be improved. Also, by adaptively changing the threshold value according to the propagation environment, the number of correlation values used for the averaging process can be reduced as compared with the first embodiment.
The time required for synchronization acquisition can be reduced.

A communication terminal device according to a third aspect of the present invention employs a configuration including the receiving device according to the first aspect or the second aspect.

According to this configuration, since the noise suppressing effect is improved and the amount of calculation is reduced, the time required for synchronization acquisition can be reduced, and the hardware scale can be reduced.

[0022] A base station apparatus according to a fourth aspect of the present invention comprises:
A configuration including the receiving device according to the first mode or the second mode is adopted.

According to this configuration, since the noise suppressing effect is improved and the amount of calculation is reduced, the time required for synchronization acquisition can be reduced, and the hardware scale can be reduced.

[0024] A synchronization acquisition method according to a fifth aspect of the present invention includes a receiving step of receiving a signal spread by a spreading code;
In a unit cycle obtained by dividing the received signal for each predetermined cycle,
A correlation value calculating step of multiplying the signal by a spread code while shifting the phase to obtain a correlation value for each phase; and a correlation value whose absolute value exceeds a predetermined value from among the correlation values at each phase within the unit period. An extraction step of extracting a value, an averaging step of integrating the absolute value of the extracted correlation value for each phase within the unit cycle for a predetermined period, averaging the sum, and detecting a delay profile; A phase detecting step of detecting a phase at the time of detecting a maximum correlation value in the delay profile.

According to this method, only the correlation value whose absolute value of the correlation value between the received signal and the known spreading code exceeds a predetermined threshold value so that the delay profile does not include a noise component. The in-phase averaging process prevents new peaks due to noise components, improves the accuracy of peak detection in the delay profile, and eliminates the effects of large noise and fading on the propagation path, and captures synchronization. can do. Further, since the amount of calculation required for detecting the delay profile can be reduced, the hardware scale can be reduced.

[0026] A synchronization acquisition method according to a sixth aspect of the present invention, in the fifth aspect, further comprises a threshold setting step of setting the predetermined value in the extraction step, and the averaging step includes: Before the predetermined period is performed, an averaging process is performed to detect a provisional delay profile, and the phase detection step detects a maximum correlation value in the provisional delay profile and outputs the maximum correlation value to the threshold setting step, In the threshold setting step, the predetermined value is determined for the extraction step based on a maximum correlation value of the provisional delay profile.

According to this method, a threshold profile is adaptively changed in accordance with the propagation environment to remove more correlation values as noise components and then create a delay profile. 1, the noise suppression effect can be improved. Also, by adaptively changing the threshold value according to the propagation environment, the number of correlation values used for the averaging process can be reduced as compared with the first embodiment.
The time required for synchronization acquisition can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) The receiving apparatus according to the present embodiment uses an in-phase signal using only a correlation value whose absolute value of a correlation value between a received signal and a known spread code exceeds a predetermined threshold value. The averaging process is performed to create a delay profile.

Hereinafter, the receiving apparatus according to the present embodiment will be described with reference to FIGS. FIG. 1 is a main block diagram illustrating a schematic configuration of a receiving apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a diagram illustrating signal processing in an extracting unit of the receiving apparatus according to Embodiment 1 of the present invention. FIG. 3 is a flowchart showing a synchronization acquisition operation in the receiving apparatus according to Embodiment 1 of the present invention.

In FIG. 1, an antenna 101 transmits and receives a radio signal, and a radio receiving section 102 receives a received carrier signal and a carrier frequency control signal as input, converts the received carrier signal into a baseband signal, and outputs the baseband signal.

The spreading code generator 103 outputs a spreading signal used for spreading the received signal. The correlation value calculation unit 104 fixes the spread code output from the spread code generation unit 103 as a known spread code, multiplies the baseband signal at a constant period by a known spread code while shifting the phase, and Is calculated. The correlation value calculation unit 104 is, for example, a matched filter or a sliding correlator.

The absolute value calculation unit 105 receives the calculated correlation value as input, and outputs the absolute value of the correlation value. Extraction unit 106
Compares the calculated absolute value of the correlation value with a predetermined threshold value and outputs only the absolute value of the correlation value exceeding the threshold value.

The processing in the extraction unit 106 will be described with reference to FIG. FIG. 2A shows the correlation value absolute value at each phase output from the absolute value calculation unit 105.

Here, the correlation value at the phase to be detected always has a certain magnitude or more, and the correlation value at a phase other than the above-mentioned phase is almost always a small correlation value. Further, in consideration of the fact that only one peak of the correlation value is originally detected, a correlation value below a predetermined threshold is not added to the in-phase average.

FIG. 2B shows the absolute value of the correlation value after the processing. As shown in the figure, the noise component less than the threshold value can be removed by this processing, and the noise suppression effect is improved. Further, since the number of bits used for the in-phase averaging process performed after this process is reduced, the required amount of calculation can be reduced.

The averaging unit 107 receives the extracted correlation value absolute value as an input, and calculates correlation values for a predetermined number of cycles.
The correlation values having the same phase are averaged, and the obtained delay profile is output.

The peak detector 108 detects a peak of the input delay profile. The phase at the time of peak detection is determined to be correct timing, and demodulation is performed based on the timing at the time of demodulation.

Next, the operation of the receiving apparatus having the above configuration will be described with reference to the flowchart of FIG.

First, step (hereinafter referred to as ST) 3
In 01, the signal received by the antenna 101 is converted into a baseband signal by the radio reception unit 102, and the correlation value is calculated by the correlation value calculation unit 104.

Next, in ST 302, the absolute value of the calculated correlation value is calculated by absolute value calculation section 105.

Next, in ST303, the calculated absolute value of the correlation value is compared in magnitude with a predetermined threshold value by extraction section 106, and only the correlation value exceeding the threshold value is extracted.

Next, in ST304, averaging section 107
Thus, it is determined whether correlation values for a predetermined number of cycles have been calculated. If the predetermined number of cycles has not been reached, ST301
If it has reached, the process proceeds to ST305, in-phase averaging is performed on the correlation value absolute values for a predetermined number of periods, and a delay profile is detected.

Next, in ST306, the peak detector 1
08, a peak is detected from the detected delay profile, and the phase at which this peak is obtained is used as the demodulation processing timing.

As described above, according to the present embodiment, the absolute value of the correlation value between the received signal and the known spread code exceeds a predetermined threshold value so that the delay profile does not include a noise component. Performing in-phase averaging using only correlation values prevents new peaks due to noise components, improves the accuracy of peak detection in delay profiles, and has an effect even when propagation path noise or fading is large. Can be removed and synchronization can be acquired.

Further, since the amount of calculation required for detecting the delay profile can be reduced, the hardware scale can be reduced.

(Embodiment 2) The receiving apparatus according to the present embodiment has the same configuration as that of Embodiment 1 except that the threshold value is changed according to the propagation environment to further improve the noise suppression effect. Things.

Hereinafter, the receiving apparatus according to the present embodiment will be described using FIG. 4 and FIG. FIG. 4 is a main block diagram showing a schematic configuration of a receiving apparatus according to Embodiment 2 of the present invention, and FIG. 5 is a flowchart showing a synchronization acquisition operation of the receiving apparatus according to Embodiment 2 of the present invention. It is. A detailed description of the same configuration as in the first embodiment will be omitted.

In order to improve the noise suppression effect, it is desirable to set the threshold value as large as possible and to remove all correlation values other than peaks in the delay profile. However, the magnitude of the peak value changes depending on the propagation environment.

Therefore, in this embodiment, a small threshold value is set immediately after the start of synchronization acquisition, and based on the peak value at an arbitrary stage during the in-phase averaging process, the correlation value other than the peak value is set. Is increased to such an extent that can be removed.

Referring to FIG. 4, an averaging section 401 averages correlation values having the same phase by using the extracted absolute value of the correlation value as an input, and outputs the obtained delay profile. Further, at an arbitrary stage before reaching a predetermined number of cycles, which is one unit period of the averaging process, the delay profile at that time (hereinafter referred to as “at the time of threshold setting”) is output to the peak detection unit 108.

The threshold value setting section 402 sets a threshold value used by the extraction section 106 for processing based on the peak value detected by the peak detection section 108 at the time of setting the threshold value, as a correlation value other than the detected peak value. Change the value so that the value can be removed.

The threshold value may be set to any value as long as the purpose of removing the correlation value other than the peak value is achieved. For example, a threshold value equal to the maximum correlation value may be set and a correlation value less than the threshold value may be removed, or a threshold value equal to the second largest correlation value may be set, and Correlation values below the threshold may be removed.

Next, the operation of the receiving apparatus having the above configuration will be described with reference to the flowchart of FIG. Note that S
Steps T501 to ST504 are the same as those in the first embodiment, and a detailed description thereof will be omitted.

In ST505, averaging section 401 determines whether or not correlation values for a predetermined number of cycles have been calculated. If the predetermined number of cycles has not been reached, the process proceeds to ST506. If the number has been reached, the process proceeds to ST507, where a peak is detected from the delay profile detected by the peak detection unit 108, and the phase at which the peak was obtained is determined. This is the demodulation processing timing.

In ST 506, threshold setting section 402 determines a new threshold based on the peak value of the delay profile, and sets the new threshold in extraction section 106. When a new threshold is set, the process returns to ST501.

As described above, according to the present embodiment, by adaptively changing the threshold value according to the propagation environment,
Since the delay profile is created after removing more correlation values as noise components, the noise suppression effect can be improved as compared with the first embodiment. Also, by adaptively changing the threshold value according to the propagation environment, the number of correlation values used for the averaging process can be reduced as compared with the first embodiment, so that the time required for synchronization acquisition can be reduced. it can.

In the flowchart of FIG. 5, the case where the threshold value is set for each calculation of the correlation value has been described.
The frequency at which the threshold value is set can be set arbitrarily as long as it is less than a predetermined number of cycles, which is one unit period for performing the averaging process.

In the first and second embodiments, the predetermined number of cycles as one unit period for performing the averaging process can be arbitrarily determined.

[0060]

As described above, according to the present invention,
The absolute value of the correlation value between the received baseband signal and the replica spreading code is compared with a predetermined threshold value, and a correlation value below the threshold value is set to 0, and an averaging process is performed to create a delay profile. By detecting the peak, the noise suppression effect at the time of detecting the peak of the delay profile can be improved, and the amount of calculation can be reduced.

Further, by changing the threshold value according to the propagation environment, the time required for synchronization acquisition can be reduced.

[Brief description of the drawings]

FIG. 1 is a main block diagram showing a schematic configuration of a receiving apparatus according to Embodiment 1 of the present invention.

FIG. 2A is a schematic diagram illustrating an output of an absolute value calculating unit of the receiving device according to the first embodiment of the present invention. FIG. 2B is a diagram illustrating an output of an extracting unit of the receiving device according to the first embodiment of the present invention. Pattern diagram

FIG. 3 is a flowchart showing a synchronization acquisition operation in the receiving apparatus according to the first embodiment of the present invention.

FIG. 4 is a main block diagram showing a schematic configuration of a receiving apparatus according to Embodiment 2 of the present invention.

FIG. 5 is a flowchart showing a synchronization acquisition operation of the receiving apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a main block diagram showing a schematic configuration of a conventional receiving apparatus.

[Explanation of symbols]

 105 Absolute value calculating unit 106 Extracting unit 107 Averaging unit 108 Peak detecting unit 402 Threshold setting unit

Claims (6)

[Claims] 1. A receiving means for receiving a signal spread by a spreading code, and a unit code obtained by dividing the received signal by a predetermined period, multiplying the signal by a spreading code while shifting the phase, and Correlation value calculation means for obtaining a correlation value, extraction means for extracting a correlation value whose absolute value exceeds a predetermined value from correlation values at each phase within the unit period, and absolute value of the extracted correlation value For each phase within the unit cycle, averaging processing by integrating for a predetermined cycle, and averaging processing to detect a delay profile; and phase detecting means for detecting a phase at the time of detecting a maximum correlation value in the delay profile. A receiving device comprising: 2. The method according to claim 1, wherein the extracting means includes a threshold value setting means for setting the predetermined value, wherein the averaging means performs an averaging process to perform the provisional delay profile before the integration is performed for the predetermined period. The phase detection means detects a maximum correlation value in the provisional delay profile and outputs the maximum correlation value to the threshold setting means, and the threshold setting means detects a maximum correlation value based on the maximum correlation value of the provisional delay profile. 2. The receiving apparatus according to claim 1, wherein the predetermined value is determined for the extracting means. 3. A communication terminal device comprising the receiving device according to claim 1 or 2. 4. A base station device comprising the receiving device according to claim 1 or 2. 5. A receiving step of receiving a signal spread by a spreading code, and, within a unit period obtained by dividing the received signal by a predetermined period, multiplying the signal by a spreading code while shifting the phase, and A correlation value calculating step of obtaining a correlation value, an extraction step of extracting a correlation value whose absolute value exceeds a predetermined value from correlation values in each phase within the unit cycle, and an absolute value of the extracted correlation value For each phase in the unit cycle, a predetermined period is integrated and averaged, and an averaging step of detecting a delay profile, and a phase detecting step of detecting a phase at the time of detecting a maximum correlation value in the delay profile And a synchronization acquisition method. 6. A threshold setting step for setting the predetermined value in the extraction step, wherein the averaging step performs an averaging process before the integration is performed for the predetermined cycle to perform a provisional delay profile. The phase detection step detects a maximum correlation value in the provisional delay profile and outputs it to the threshold setting step, and the threshold setting step is based on the maximum correlation value of the provisional delay profile. 6. The method according to claim 5, wherein the predetermined value is determined for the extracting step.