JP2002009665A - Correlation peak detection method, correlation peak detector, searcher, and communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a correlation peak detection method, by which number of times for correlation peak detection processing can be revised according to communication conditions, so as to maintain reliability of correlation peak detection to be nearly constant, thereby efficiently detecting the correlation peak used for cell search processing or the like with reliability. SOLUTION: In the correlation peak detection method, that detects a correlation peak of a correlation function so as to identify a pattern, the ratio of a peak value of the correlation function to a non-peak value is calculated to obtain a detection ratio of the correlation peak, on the basis of the calculated ratio, and the number of times of detection processing for the correlation peak is decided on the basis of the detected ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correlation peak detection rate indicating the likelihood of a correlation peak based on a ratio between a peak value and a non-peak value. The present invention relates to a correlation peak detection method for detecting a code group of codes, a correlation peak detection device, a searcher device, and a communication terminal.

[0002]

2. Description of the Related Art In a CDMA cellular system, a mobile station needs to establish synchronization of a spread code sequence before establishing carrier or clock synchronization. It may take a long time to establish this code synchronization, and shortening it is an important issue for CDMA cellular systems.

[0003] DS-CDMA (Direct Sequence-Code D)
ivision Multiple Access) In a cell search at the time of establishing initial synchronization of a cellular system, there are three stages of processing: (1) establishment of slot synchronization, (2) establishment of frame synchronization and detection of a code group, and (3) detection of a code number. However, when the SN ratio is small or when the received signal level is extremely small under a fading environment, the above (2) is used.
Regarding (3), the probability of a detection error increases.

That is, upon detecting a code group, a correlation function between a received signal including a predetermined pattern and a plurality of patterns including the predetermined pattern is calculated,
A pattern included in the received signal is identified based on the correlation peak, and a code group is identified based on the pattern. However, in a case where the correlation level of the received signal is small and substantially equal to the noise level, etc. In
Due to the influence of noise and fading, the detection rate of the correlation peak decreases, and the possibility of identifying an erroneous code group increases. If the wrong code group is detected,
Since the code number detection process, which is the next process, is performed on a code group that is erroneously detected, the code number cannot be specified, and therefore the code number cannot be detected.

For this reason, Japanese Patent Application Laid-Open No. H11-8607 discloses a technique in which the cell search process is repeated a predetermined number of times regardless of the communication state.

[0006]

However, if the cell search process is always repeated a predetermined number of times, the communication condition is good and the initial synchronization is sufficiently established even in the single cell search process when the SN ratio is good. Even in such a case, the cell search process is repeated, so that there is a problem that the cell search process is efficiently terminated, and it is not possible to quickly enter the original communication posture such as a telephone conversation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and it is desirable to change the number of correlation peak detection processes according to communication conditions so that the reliability of correlation peak detection can be maintained substantially constant. It is an object of the present invention to provide a correlation peak detection method, a correlation peak detection device, a searcher device, and a communication terminal capable of efficiently and reliably detecting a correlation peak used for a cell search process or the like. And

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a correlation peak detecting method for detecting a correlation peak of a correlation function and performing pattern identification. A non-peak value ratio is calculated, and a correlation peak detection rate is obtained based on the calculated value.

According to such a configuration, a detection rate can be obtained as a probability that the detected peak is a correlation peak. Then, by using this detection rate, for example, in order to determine that the detected peak is a correlation peak, it is possible to set the number of required repetition processing and the like,
The reliability of correlation peak detection can be increased.

The correlation peak detection method according to the present invention is characterized in that the number of correlation peak detection processes is determined based on the detection rate. In addition, the reliability of the correlation peak detection can be maintained substantially constant, and the minimum required number of processes sufficient to maintain the predetermined reliability can be determined, so that the correlation peak detection process can be performed efficiently. it can.

Further, the correlation peak detection method according to the present invention generates a pattern for a signal including a pattern periodically, calculates a correlation function, and calculates a correlation peak based on the correlation peak detection rate obtained from the correlation function. In order to determine the peak as a correlation peak, the correlation function calculation is performed to determine the number of times that the peak should be continuously detected at a position corresponding to the peak. According to such a configuration, the reliability of the correlation peak detection can be maintained substantially constant, and the minimum required number of processes sufficient to maintain the predetermined reliability can be determined. Correlation peak detection processing can be performed efficiently.

Further, in the correlation peak detecting method according to the present invention, the pattern is a PN sequence, and according to such a configuration, it is possible to detect a correlation peak in a communication system using a PN sequence. The present invention can be applied. In the embodiment, the PN
The sequence is generated by a feedback shift register (not shown) provided in the searcher 3024.

Further, the correlation peak detecting apparatus according to the present invention comprises a pattern generating means for generating a pattern, a signal obtaining means for obtaining a signal including the pattern, a pattern generated from the pattern generating means and the signal Correlation function calculating means for calculating a correlation function with a signal obtained from the obtaining means, ratio calculating means for calculating a ratio of a peak value to a non-peak value of the correlation function obtained from the correlation function calculating means, and the ratio calculating means And a correlation peak detection rate calculating means for obtaining a correlation peak detection rate based on the calculation ratio according to (1).

According to such a configuration, it is possible to obtain a detection rate as a certainty that the detected peak is a correlation peak. Therefore, by using this detection rate, for example, the detected peak is a correlation peak. As a result, it is possible to obtain a correlation peak detection device capable of setting a necessary number of times of repetition processing and the like. In the embodiment, the ratio calculating means and the correlation peak detection rate calculating means are constituted by the code group detecting section 30243.

Further, the correlation peak detecting apparatus according to the present invention further comprises a detection number setting means for determining a correlation peak detection processing number based on the correlation peak detection rate obtained by the correlation peak detection rate calculating means. According to such a configuration, the reliability of correlation peak detection can be maintained substantially constant, and the minimum required number of processes sufficient to maintain the predetermined reliability can be determined. It is possible to obtain a correlation peak detection device capable of performing processing efficiently.

In the correlation peak detecting apparatus according to the present invention, the number-of-detections setting means determines the peak as the correlation peak when the signal periodically includes the pattern. The number of times the peak should be continuously detected is set at a position where the correlation peak is detected. According to such a configuration, the reliability of the correlation peak detection can be maintained substantially constant, and the predetermined reliability can be maintained. Therefore, it is possible to obtain a correlation peak detection processing device that can determine the minimum necessary number of processes sufficient to maintain the correlation peak value and can efficiently perform the correlation peak detection process. In the embodiment, the number-of-detections setting means includes:
It is configured by a code group detection unit 30243.

In the correlation peak detection apparatus according to the present invention, the number of times set by the number-of-detections setting means is such that the detected peak is a correlation peak based on the detection rate obtained by the correlation peak detection rate calculating means. It is characterized in that the probability is determined to be equal to or more than a predetermined value.According to such a configuration, the reliability of correlation peak detection can be maintained almost constant,
It is possible to obtain a correlation peak detection device that can determine the minimum required number of times of processing sufficient to maintain the predetermined reliability and can efficiently perform the correlation peak detection process.

Further, according to the present invention, a plurality of patterns included in a received signal are identified by detecting a correlation peak,
Based on the arrangement of these patterns, a code group of a scramble code is detected, and in a searcher device that detects a code number of a scramble code using the detected code group, a signal including a pattern for code group detection is detected. A correlation function calculating means for receiving and correlating the signal with the same pattern as the pattern included in the signal, and a ratio for calculating a ratio between a peak value and a non-peak value obtained by the correlation function calculating means And a correlation peak detection rate calculating means for calculating a correlation peak detection rate based on the ratio calculated by the ratio calculation means.

According to such a configuration, in the correlation peak detection processing in the cell search processing at the time of establishing synchronization,
A detection rate can be obtained as a probability that the detected peak is a correlation peak. Therefore, using this detection rate, for example, the number of necessary repetition processing to determine that the detected peak is a correlation peak It is possible to obtain a searcher device capable of setting the above.

Further, the searcher device according to the present invention comprises:
Based on the correlation peak detection rate obtained by the correlation peak detection rate calculation means, to determine the peak as the correlation peak, the number of times that the peak should be continuously detected at a position corresponding to the peak position According to such a configuration, the reliability of the correlation peak detection can be maintained substantially constant, and the predetermined reliability is maintained. To determine the minimum number of required processes to
A searcher device capable of efficiently performing the correlation peak detection process can be obtained.

Further, the searcher device according to the present invention comprises:
About the number set by the detection number setting means,
When a peak is continuously detected at a position corresponding to the peak, the peak is identified as a correlation peak, and a pattern is identified.According to such a configuration, a spreading code group can be efficiently generated. Thus, a searcher device which can perform detection while maintaining a certain degree of reliability is obtained.

The present invention also provides a baseband unit,
And a communication terminal including an antenna, wherein the baseband unit includes a transmitting unit and a receiving unit, the receiving unit is a searcher unit that establishes initial synchronization to a base station,
A searcher unit according to any one of claims 9 to 11 is provided.

According to such a configuration, it is possible to obtain a communication terminal capable of performing the initial synchronization establishment process with high reliability and efficiency.

Further, in the communication terminal of the present invention, the communication terminal is a portable terminal,
According to such a configuration, it is possible to obtain a mobile terminal capable of performing the initial synchronization establishment process with high reliability and efficiency.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to DS.
-An example will be described for a mobile terminal used in a CDMA cellular system. FIG. 1 is a block diagram showing the overall configuration of the mobile terminal. This mobile terminal includes a transmitting / receiving antenna 1 and
An RF unit 2 that is connected to a transmission / reception antenna 1 and mixes a transmission baseband signal with a carrier wave and orthogonally modulates the signal to transmit from the antenna 1 or that orthogonally demodulates a reception signal to obtain a reception baseband signal; Connected, and spread-modulates the baseband signal to generate R as a transmission baseband signal.
A baseband unit 3 that receives the baseband signal delivered to the F unit 2 or the received baseband signal delivered from the RF unit 2, performs despread demodulation, and performs error correction processing or the like to obtain a speech codeword; Control unit (CPU) 4 for performing control
And encodes the audio signal input from the microphone connected to the baseband unit 3 and delivers it to the baseband unit 3, or converts the audio codeword delivered from the baseband unit 3 into an analog audio signal and outputs it to the speaker And an audio codec 5.

FIG. 2 is a block diagram showing in detail the baseband unit shown in FIG. This baseband part 3
Is a CDMA modem 30 that performs modulation / demodulation (spreading / despreading).
, A channel codec 31 for performing error correction and the like, and a DP-RAM (Dual Port RAM) 3 provided therebetween.
2, 33, a D / A converter 34 for converting a digital signal from the CDMA modem 30 into an analog signal and outputting the analog signal to the RF unit 2, and a D / A converter 34 for converting an analog signal from the RF unit 2 into a digital signal. And an A / D converter 35 for inputting to the.

The CDMA modem 30 receives frame-coded sound encoded data from the output side of the channel codec 31 via the DP-RAM 32 and transmits it as a transmission baseband signal via the D / A converter 34. A transmitting unit 301 that outputs a signal and a received baseband signal are input through an A / D converter 35, despread and demodulated into a baseband signal, and output to a channel codec 31 through a DP-RAM 33. And a sequence controller (DSP: Digital Sign) connected to the transmitting unit 301 and the receiving unit 302 and performing sequence control.
al Processor) 303 and a timing generator 304 for forming a timing pulse.

FIG. 3 shows the receiving section 302 shown in FIG.
Is a block diagram showing in detail.
AGC3 that performs automatic gain control to obtain a constant gain
021, an AFC 3022 for performing automatic frequency control based on a carrier frequency from a base station, a RAKE unit 3023 for demodulating and combining various received signals to obtain a received signal, and a cell for establishing initial synchronization. A searcher (searcher device of the present invention) 3024 that performs a search process, performs slot synchronization and frame synchronization, detects a code group of a scramble code, and further detects a code number from the code group; And a generator 304.

The RAKE section 3023 includes a plurality of finger sections 30231 for performing despreading according to each path, a RAKE combiner 30232 for combining baseband signals obtained in the respective finger sections,
A wireless frame processing circuit 30233 for performing frame processing based on the output of the synthesizer.

FIG. 4 is a block diagram showing a searcher in detail, and FIG. 5 is a time chart showing slots (Primary-SCH, Secondary-SCH) detected by the searcher. In FIG. 5, (a) shows the PCCPCH (Prim
ary Common Controll Physical Channel)
(B) shows Primary-SCH (Synchronized Channel), and (c) shows Secondary-SCH. PCCPCH (BCH) shown in (a) is 15 ksps (= 30 ksps).
(bps) BCH is transmitted at a fixed rate. The first symbol (256 chops) of each slot is in a transmission off state, and is handled by a searcher only during that period.
(B) The Primary-SCH and Secondary-SCH shown in (c) are transmitted.

The Primary-SCH shown in (b) is a channel for initial synchronization (slot synchronization), and is 256 chips.
s / slot and the code is common to all cells. Secondary-SCH shown in (c) is a channel for identifying a scrambling code (Scrambling Code) group, which is a scrambling code, and is a channel similar to Primary-SCH.
Although there are 6 chips / slot, there are 16 types of codes, which are appropriately changed for each slot, and the combination of the combinations corresponds to the scramble code group.

The searcher shown in FIG. 4 includes a matched filter 30241 to which a received signal is inputted, a path search section 30242 connected to the matched filter, and a code group detecting section 30243 to which the received signal is inputted.
And a code number detecting section 30244 connected to the code group detecting section. Both the path information detected by the path search unit and the code number detected by the code number detection unit are input to the sequence controller 303 and used for communication control after the initial synchronization is established.

In the above configuration, the searcher first detects the slot timing indicated in the Primary-SCH in order to establish the initial synchronization. This slot timing is detected by averaging the pulse positions obtained by the matched filter by a path search. When the slot timing is detected, the code group detection unit
Identify each pattern (16 types) of each slot (S1 to S15) in the y-SCH, synchronize the frame (detect the head of the frame) and detect the scramble code group based on the arrangement of these patterns. I do.
When a scramble code group is detected, the code number detection unit detects a scramble code number from the scramble code group.

FIG. 6 is an explanatory diagram showing an operation of detecting a scramble code group in the code group detection section. The code group detection unit 30243 includes Secondar
Pattern signals (function patterns) corresponding to 16 types of patterns attached to the y-SCH and transmitted are input in synchronization with the pattern (Secondary-SCH) assigned to the Secondary-SCH, and these correlation functions are calculated. 16 first to first
Six correlators C1 to C16 are provided. Then, the scramble code search block 3024a detects the arrangement of the patterns of the 15 slots from the correlation peak (slot position) output from these correlators, and detects the scramble code group based on the arrangement. Each scramble code group includes eight scramble codes having eight scramble code numbers.

The scramble code search block 302
The method of obtaining the correlation peak performed in 4a will be described with reference to FIGS. When the function pattern input to a certain correlator matches the pattern of the slot, the correlation function which is the output of the correlator is shown as in FIG. Here, when the peak is a correlation peak, it is determined that the function pattern and the slot pattern match. However, when the S / N ratio such as noise decreases, the difference between the correlation peak level (A level) and the noise level (B level) decreases, that is, the A / B ratio decreases, and the reliability of correlation peak detection increases. That is, the reliability with which the detected peak can be determined to be the correlation peak decreases.

Therefore, in this embodiment, as shown in FIG. 8, the detection rate (%) of the correlation peak with respect to the A / B ratio is determined, and the detection rate is obtained from the calculated A / B value. . The relationship between the A / B ratio and the detection rate is stored as a table in, for example, the scramble code search block 3024a. Then, based on the detection rate at this time, the processing is repeated a predetermined number of times, and it is determined that the correlation peak is present.

For example, when the detection rate is 95%, it can be determined that the peak is almost a correlation peak.
The correlation process is performed only once. When the detection rate is 80%, if the peak is detected twice consecutively at the same corresponding position, the probability that the peak can be determined as a correlation peak is (1).
00-4) = 96% (95% or more). In this case, the correlation processing is repeated twice and a peak is detected at the same corresponding position, and it is determined to be a correlation peak.

As described above, in the present embodiment, the number of times the processing is repeated is determined in advance for the detection rate obtained in the first processing, and the peak is detected at the same position by that number of times. Therefore, it is determined to be a correlation peak. If a peak is not continuously detected at the position corresponding to the number of times, the detected peak is reset and the same processing is repeated.

For example, from the obtained detection rate, in order to satisfy a predetermined value (for example, 95%) as a probability that the detected peak is a correlation peak, the same peak is obtained several times in succession. It may be calculated whether or not the correlation peak can be obtained, and the operation of detecting the correlation peak may be repeated on the calculation result.

As described above, in the above-described embodiment, the number of times of processing is determined in accordance with the detection rate obtained first, but it is further determined that the peak obtained for each processing is a correlation peak. It is also possible to calculate the probability of being performed and determine the final number of times of processing (at the end of processing) based on the calculation result. According to such a configuration, even when the detection rate differs every time a correlation peak is detected, a correlation peak can be detected while maintaining a certain level of reliability.

As described above, according to the present embodiment, when the communication environment is good and the SN ratio is good, the value of A / B (R1) increases, and the detection rate (C1) also increases. And the correlation peak can be determined by, for example, one detection operation, and the efficiency and speed of the detection operation processing can be improved.

On the other hand, when the communication environment is poor and the SN ratio is poor, the value of A / B (R1) decreases, and the detection rate (C1) also decreases. ,
The detection operation is repeated a predetermined number of times (or until the detection probability exceeds a predetermined value) based on R1, and when the corresponding correlation peak is continuously obtained, the correlation peak is regarded as reliable and the detection operation is terminated. I do.

FIG. 9 is a flowchart showing the overall operation of the process of establishing the initial synchronization (cell search process). First,
At the time of the initial synchronization probability, it is determined whether or not the time is the initial synchronization probability (S1).
A correlation peak is obtained from the output of the 16th correlator, and a code group is specified based on the result (S3). In this case, when determining the correlation peak, as described above, C1
The correlation peak detection process is repeated until the detection probability exceeds a predetermined detection probability based on the value (S2, S3). When the code group is detected, the code group number is output and the frame is synchronized (S4). Next, a scramble code identification process is performed (S5, S6). This is performed by performing a matching process by correlation operation on all (eight types) of scramble codes. When the scramble code is determined, a code number is output (S7), a scramble code search end signal is output (S8), and the process ends.

Although the embodiment of the present invention has been described above with reference to a portable terminal of the CDMA communication system, the present invention can be applied to a portable terminal or a communication system using another system. It is needless to say that the present invention can be widely applied to a measuring device, a discriminating device, a pattern discriminating device, and the like that use the device.

[0045]

As described in detail above, according to the present invention, the number of correlation peak detection processes can be changed according to communication conditions so that the reliability of correlation peak detection can be kept constant. Thus, it is possible to quickly and reliably detect a correlation peak used for a cell search process or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a portable terminal according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a baseband unit of the mobile terminal.

FIG. 3 is a block diagram illustrating a configuration of a receiving unit.

FIG. 4 is a block diagram showing a searcher.

FIG. 5 is a diagram showing a reception signal.

FIG. 6 is a block diagram illustrating a code group detection unit.

FIG. 7 is a diagram showing a correlation function.

FIG. 8 is a diagram showing a correlation peak detection rate.

FIG. 9 is a flowchart showing an entire process of a cell search.

[Explanation of symbols]

1 transmitting / receiving antenna, 2 RF section, 3 baseband section, 4 control section (CPU), 5 voice codec, 30
CDMA modem, 302 receiver, 3024 searcher, 3024a scramble code search block,
30241 matched filter, 30242 path search unit, 30243 code group detection unit, 30244
Code number detector, C1 to C16 correlator.

Claims (13)

[Claims] 1. A correlation peak detection method for detecting a correlation peak of a correlation function and performing pattern identification, comprising: calculating a ratio between a peak value and a non-peak value of the correlation function;
A correlation peak detection method, wherein a correlation peak detection rate is determined based on the calculated value. 2. The correlation peak detection method according to claim 1, wherein the number of times the correlation peak is detected is determined based on the detection rate. 3. The correlation peak detection method according to claim 1, wherein the pattern is generated for a signal containing the pattern periodically, and a correlation function operation is performed, and the signal is obtained from the correlation function. Based on the correlation peak detection rate, in order to determine the peak as a correlation peak, perform the correlation function calculation to determine the number of times that the peak should be continuously detected at a position corresponding to the peak. A correlation peak detection method, characterized in that: 4. The correlation peak detection method according to claim 1, wherein the pattern is a PN sequence. 5. A pattern generating means for generating a pattern, a signal obtaining means for obtaining a signal including the pattern, a correlation function between a pattern generated by the pattern generating means and a signal obtained from the signal obtaining means. , A ratio calculating means for calculating a ratio between a peak value and a non-peak value of the correlation function obtained by the correlation function calculating means, and a correlation peak detection rate based on the calculation ratio by the ratio calculating means. And a correlation peak detection rate calculating means for calculating the correlation peak detection rate. 6. The correlation peak detection device according to claim 5, wherein the number-of-detections setting unit that determines the number of correlation peak detection processes based on the correlation peak detection ratio obtained by the correlation peak detection ratio calculation unit. Correlation peak detection device provided. 7. The correlation peak detection device according to claim 6, wherein the detection count setting unit determines the peak as the correlation peak when the signal includes the pattern periodically. A correlation peak detection device for setting the number of times the peak should be continuously detected at a position corresponding to the position. 8. The correlation peak detection device according to claim 6, wherein the number set by the number-of-detections setting means is based on a detection rate obtained by the correlation peak detection rate calculating means. A correlation peak detection device characterized in that a probability that a detected peak is a correlation peak is determined to be equal to or more than a predetermined value. 9. A plurality of patterns included in a received signal are identified by detecting a correlation peak, a code group of a scramble code is detected based on an arrangement of these patterns, and the detected code group is used. In a searcher device for detecting a code number of a scramble code, a correlation function calculating means for receiving a signal including a pattern for detecting a code group and correlating the signal with the same pattern as the pattern included in the signal A ratio calculating means for calculating a ratio between a peak value and a non-peak value obtained by the correlation function calculating means; and a correlation peak detection rate calculating means for obtaining a correlation peak detection rate based on the calculation ratio by the ratio calculating means. A searcher device comprising: 10. The searcher device according to claim 9, wherein the peak is determined as the correlation peak based on the correlation peak detection rate obtained by the correlation peak detection rate calculation means. A searcher device comprising: a number-of-detections setting unit that sets the number of times that the peak should be continuously detected at a corresponding position. 11. The searcher device according to claim 10, wherein the number of times set by the number-of-detections setting means is:
A searcher characterized in that when a peak is continuously detected at a position corresponding to the peak, a pattern is identified using the peak as a correlation peak. 12. A communication terminal including a baseband unit, an RF unit, and an antenna, wherein the baseband unit includes a transmission unit and a reception unit, and the reception unit establishes initial synchronization with a base station. A communication terminal comprising: the searcher unit according to claim 9. 13. The communication terminal according to claim 12, wherein the communication terminal is a portable terminal.