JP4389346B2 - Synchronization detection apparatus and method, and radio signal reception apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio communication apparatus, and more particularly, to a synchronization detection apparatus and method suitable for an asynchronous cellular radio communication system between base stations using a DS-CDMA (Direct Spread-Code Division Multiple Access) system, and The present invention relates to a radio signal receiving apparatus and method.
[0002]
[Prior art]
The DS-CDMA system is a multiplexing system using a pseudorandom noise (PN) code, and is actively studied for application to a cellular radio communication system as one of the radio access systems of the next generation mobile communication system. Has been. In a cellular radio communication system, an area for providing communication services is divided into cells (cells) of a desired size, and base stations as fixed stations are respectively installed in the cells, and mobile communication terminal devices that are mobile stations Is configured to establish a wireless connection with a base station that seems to have the best communication state.
[0003]
In such a cellular radio communication system, searching for a base station to which a mobile station is connected is generally called cell search. In the DS-CDMA cellular radio communication system, since each base station uses the same frequency, the timing of the spreading code included in the received signal must be supplemented simultaneously with this cell search.
[0004]
By the way, the cellular radio communication system using the DS-CDMA system can be classified into two types: an inter-base station synchronization system that performs time synchronization between all base stations, and an inter-base station asynchronous system that does not perform this. As is standardized by the IS-95 standard, the inter-base station synchronization system is configured to set the absolute reference time at each base station using GPS radio waves. Keep in sync. In this inter-base station synchronization system, each base station transmits the same code as a spreading code at a different timing for each base station with reference to its absolute reference time. Can search for a base station to connect to by simply supplementing only the timing of the spreading code.
[0005]
On the other hand, in the asynchronous system between base stations, a different spreading code is transmitted for each base station to identify the base station. Therefore, the mobile station detects the timing of the spreading code during cell search. In addition, it is necessary to detect the type of the spreading code. For this reason, in the case of an asynchronous system between base stations, there is a demerit that the time required for cell search becomes longer than that in the synchronous system between base stations. On the other hand, in the asynchronous system between base stations, it is not necessary to receive GPS radio waves, so the service area can be expanded even in places where GPS radio waves do not reach, solving the problem of cell search If possible, it is a very effective system.
[0006]
[Problems to be solved by the invention]
Several methods are conceivable as methods for increasing the cell search time in the asynchronous inter-base station system. One of them is to send a spreading code, a first synchronization code common to each base station, and a second synchronization code for identifying a spreading code group for identifying the spreading code. Based on these synchronization codes, This is a method for detecting the timing and code type of the spread code sent.
[0007]
This method will be specifically described. As shown in FIG. 8, the first synchronization code SC1 and the second synchronization code SC2i (i = 1, 2, 3,... 15) are transmitted from the base station. First, the mobile station (portable communication terminal apparatus) takes a correlation with the first synchronization code SC1 having a relatively short period common to each base station by using a correlation value acquisition means such as a matched filter, and the first synchronization code SC1. Get the transmission timing. This is the slot timing Ts. Next, the mobile station acquires the second synchronization code SC2i at the same timing as the acquired first synchronization code SC1.
[0008]
The second synchronization code SC2i is used to narrow down the timing and type of the spreading code LC having a relatively long cycle. FIG. 9 shows a specific example of the second synchronization code. The spreading code LC is divided into spreading code groups LCGP, and a second synchronization code pattern SC2PT is prepared for each of the groups Group 1, Group 2, Group 3,. The second synchronization code pattern SC2PT is a plurality of second synchronization codes SC2i arranged in a specific repetition pattern for each spreading code group LCGP. By identifying this pattern, the spreading code group LCGP is specified, and the repetition pattern The timing of the beginning of the spread code LC (referred to as frame timing TF) can be obtained by identifying the beginning of the code.
[0009]
If the second synchronization code pattern SC2PT can be obtained, the spreading code LC is limited to the code in the spreading code group LCGP, and the frame timing TF is also known, so by sequentially obtaining the correlation for the code in the LCGP, It is possible to quickly identify the spreading code LC in the base station.
[0010]
By the way, the CDMA system is characterized in that by adopting the diversity RAKE system, the influence of fading due to multipath as shown in FIG. 10 can be reduced and the S / N ratio can be improved. In other words, in addition to the direct path P1 from the base station 101 to the mobile terminal device 102, the influence of fading is generated by combining the signals S2 and S3 from the path P2 and the path P3 changed by the building 103A and the building 103B. While reducing, S / N ratio is improved.
[0011]
In the diversity RAKE system, the signals S1, S2, and S3 of the plurality of paths P1, P2, and P3 having time-energy characteristics shown in FIG. Receivable receivers 121A, 121B, and 121C are prepared. Then, the timing detector 123 supplements the spreading code in each path, and this spreading code is set in the receiver 121A, 121B, 121C of each path P1, P2, P3. The plurality of receivers 121A, 121B, and 121C demodulate the signals of the plurality of paths P1, P2, and P3, respectively, and the received outputs are combined by the combining circuit 122. In this way, by demodulating the received outputs from the plurality of paths P1, P2, and P3, and synthesizing the demodulated outputs from the plurality of paths, the signal strength increases and the S / N ratio can be improved. The effect of fading due to multipath can be reduced.
[0012]
In the DS-CDMA system, the same method as the cell search is used when detecting multipaths such as the plurality of paths P1, P2, and P3. That is, acquisition of slot timing by correlation with the first synchronization code, acquisition of spreading code group and frame timing by specifying correlation with the second synchronization code and second synchronization code pattern, and specification of spreading code by correlation with spreading code I do. Here, when the second synchronization code pattern or spreading code is known in advance based on information from the base station or the like, the second synchronization code pattern or spreading code specifying process is correlated only with one known type of code, for example. Can be simplified.
[0013]
However, in an inter-base station asynchronous system, it is not necessary to supplement the first synchronization code that is common to each base station transmitted from other base stations or cells. Since it is not possible to determine whether or not a predetermined cell is exceeded, a correlation is made with either the second synchronization code or the spreading code (or both), and a comparison is made as to whether or not a preset threshold value is exceeded. It is necessary to confirm whether it is a signal.
[0014]
However, it may not be sufficient to determine whether the signal is from a desired cell by obtaining a certain threshold value for the correlation value with the second synchronization code or spreading code.
[0015]
Hereinafter, a detailed description will be given with reference to FIGS. 13 and 14. Paths P11, P12, and P2 in FIG. 13 indicate signal paths from the first base station 41 and the second base station 42 to the mobile communication terminal device 40. The correlation energy E1 between the signal transmitted from the first base station 41 via the path P11 and the code 1 is as shown in FIG. 14, and the correlation energy E2 between the signal transmitted from the path P12 and the code 1 is as shown in FIG. Is as shown in FIG. Further, the energy E3 is due to the signal and the code 2 from the second base station 42 through the path P2. In the case of a signal having a relatively large energy such as E3, the correlation value with the code 1 which is the wrong spreading code as well as the correlation value with the code 2 which is the correct spreading code shows a large value. There is a problem that the correlation energy E3 ′ that does not actually exist is erroneously detected, and it is recognized that there is a path P13 in FIG. 13 that does not actually exist.
[0016]
The present invention has been made in consideration of the above points, and an object of the present invention is to provide a synchronization detection apparatus and method, and a radio signal reception apparatus and method that can improve the accuracy of multipath search and cell search.
[0017]
[Means for Solving the Problems]
In order to solve the above-described problem, the synchronization detection apparatus according to the present invention obtains the correlation detection means for obtaining a correlation value between a signal received from a base station and at least two types of pseudo-random noise codes, and the correlation detection means. Correlation energy calculation means for obtaining the energy of the correlation value and the correlation energy calculation means At least two types of pseudo-random noise codes for in-phase and quadrature components of the signal; correlation Value energy Whether the ratio is between the lower and upper limits that can be set arbitrarily. A determination unit that determines whether or not a signal received from the base station is valid, and a synchronization timing for a spreading code transmitted from the base station based on the signal that is determined to be valid by the determination unit And a timing detection means for detecting.
[0018]
In order to solve the above problems, a synchronization detection method according to the present invention is obtained by a correlation detection step for obtaining a correlation value between a signal received from a base station and at least two types of pseudo-random noise codes, and the correlation detection step. Correlation energy calculation step for obtaining the energy of the correlation value obtained and the correlation energy calculation step At least two types of pseudo-random noise codes for in-phase and quadrature components of the signal; correlation Value energy Whether the ratio is between the lower and upper limits that can be set arbitrarily. A determination step for determining whether or not a signal received from the base station is valid, and a synchronization timing for a spreading code transmitted from the base station based on the signal determined to be valid in the determination step And a timing detection step for detecting.
[0019]
In order to solve the above problems, a radio signal receiving apparatus according to the present invention obtains a correlation value between a signal received from a base station and at least two types of pseudo-random noise codes, and a correlation detection unit. Correlation energy calculation means for obtaining the energy of the correlation value obtained by the correlation energy calculation means At least two types of pseudo-random noise codes for in-phase and quadrature components of the signal; correlation Value energy Whether the ratio is between the lower and upper limits that can be set arbitrarily. A determination unit that determines whether or not a signal received from the base station is valid, and a synchronization timing for a spreading code transmitted from the base station based on the signal that is determined to be valid by the determination unit Despreading the signal transmitted from the base station via a plurality of paths using the timing detection means for detecting the signal and the spreading code obtained by the synchronization timing detected by the timing detection means, and the despread signals of the plurality of paths Demodulating means for demodulating the signals for each path, combining them, and outputting a demodulated signal.
[0020]
In order to solve the above problems, a radio signal receiving method according to the present invention obtains a correlation detection step for obtaining a correlation value between a signal received from a base station and at least two types of pseudo-random noise codes, and the correlation detection step. Correlation energy calculating step for obtaining the energy of the correlation value, and calculating the correlation energy Process Sought in At least two types of pseudo-random noise codes for in-phase and quadrature components of the signal; correlation Value energy Whether the ratio is between the lower and upper limits that can be set arbitrarily. A determination step for determining whether or not a signal received from the base station is valid, and a synchronization timing for a spreading code transmitted from the base station based on the signal determined to be valid in the determination step And a demodulation step of demodulating the received signal based on the spreading code obtained based on the synchronization timing detected in the timing detection step.
[0021]
In each of the above devices and methods, correlation values for at least two types of pseudo-random noise codes are simultaneously obtained for the received signal, and when these ratios are far from the values set as the assumed ratios, By making the value an error, erroneous detection of the synchronization signal can be reduced, and the accuracy of multipath search and cell search can be improved.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment is a radio signal receiving device incorporating a specific example of the synchronization detecting device of the present invention.
[0023]
The synchronization detection device and the radio signal reception device are realized by adopting the hardware configuration described below, but are realized by a computer system that executes the synchronization detection method and the radio signal reception method of the present invention as software. Also good.
[0024]
The radio signal receiving apparatus 1 shown in FIG. 1 is used in a CDMA system inter-base station asynchronous system, and includes a synchronization detecting apparatus 2 and a demodulating apparatus 3. The synchronization detector 2 detects the synchronization timing for different spreading codes transmitted as pilot signals for each base station, and transmits the transmission timing signal T _code Is detected. The demodulator 3 receives the timing signal T detected by the synchronization detector 2. _code The base station demodulates the transmission signal transmitted by being spread by the spreading code using the spreading code extracted based on the above.
[0025]
The radio signal receiving apparatus 1 includes an antenna 4 that receives a spread spectrum signal transmitted from a base station, an RF unit 5 that converts the spread spectrum signal received by the antenna 4 into an intermediate frequency signal, An A / D converter 6 that converts the intermediate frequency signal from the RF unit 5 into a digital signal is also provided. Specifically, the intermediate frequency signal is distributed after the RF unit 5, and the distributed signal is multiplied by two oscillation signals shifted by π / 2 as shown in FIG. The in-phase component DI and the quadrature component DQ of the spectrum-spread transmission signal are extracted through the BPF and supplied to the synchronization detection device 2 and the demodulation device 3. The radio signal receiving device 1 also includes a controller 7 that controls the synchronization detecting device 2 and the demodulating device 3.
[0026]
The synchronization detector 2 receives the in-phase component DI and the quadrature component DQ of the transmission signal, and transmits the transmission timing signal T of different spreading codes transmitted for each base station. _code , And the transmission timing signal T _code To the controller 7.
[0027]
The controller 7 transmits a transmission timing signal T of the spreading code. _code The transmission timing signal T is sent from the synchronization detection device 2 via the controller 7 to the demodulation device 3. _code The in-phase component DI and the quadrature component DQ of the transmission signal are despread based on the above, and demodulated for each path, synthesized and output from the output terminal 8.
[0028]
Next, a detailed configuration of the synchronization detection device 2 will be described with reference to FIG. The synchronization detection device 2 is supplied with the in-phase component DI and the quadrature component DQ of the transmission signal. These components are generated as follows. First, an intermediate frequency signal is supplied from the RF unit 5 through the input terminal 10. This intermediate frequency signal is distributed and multiplier 11. _I And multiplier 11 _Q To be supplied. Multiplier 11 _I Is supplied with an intermediate frequency oscillation signal (cosωt) from the oscillator 12. On the other hand, the multiplier 11 _Q Is supplied with an oscillation signal (sinωt) whose phase is shifted from a phase shifter 13 that shifts the phase of the oscillation signal from the oscillator 12 by π / 2. Multiplier 11 _I Multiplies the intermediate frequency signal by the oscillation signal (cosωt) and outputs the multiplication output to the A / D converter 6. _I Output to. A / D converter 6 _I Converts the multiplication output into a digital signal and outputs BPF14. _I To supply. BPF14 _I The signal passed through only the necessary band becomes a baseband signal DI having an in-phase component. On the other hand, the multiplier 11 _Q Multiplies the intermediate frequency signal by the oscillation signal (sinωt) and outputs the multiplication output to the A / D converter 6. _Q Output to. A / D converter 6 _Q Converts the multiplication output into a digital signal and outputs BPF14. _Q To supply. BPF14 _Q The signal passed through only the necessary band becomes a baseband signal DQ having an orthogonal component.
[0029]
The synchronization detection apparatus 2 includes a correlation detection unit 15 that obtains correlation values DI · C1 and correlation values DI · C2 between the baseband signal DI of the in-phase component and the two types of codes C1 and C2, and the baseband signal of the quadrature component Correlation value DQ · C1 and correlation value DQ · C2 between DQ and two types of codes C1 and C2, and correlation value DI · C1 detected by correlation detection unit 15 and correlation detection unit 17 detect The correlation energy Ea for calculating the correlation energy Ea with the correlation value DQ · C1, the correlation value DI · C2 detected by the correlation detection unit 15 and the correlation value DQ · C2 detected by the correlation detection unit 17 Correlation energy calculation unit 20 for calculating the correlation energy Eb of correlation energy Ea and correlation energy Eb obtained by correlation energy calculation unit 19 and correlation energy calculation unit 20 Based on the comparison unit 21 serving as a determination unit for determining whether or not the signal received from the base station is valid based on the signal, and transmitted from the base station based on the signal determined to be valid by the comparison unit 21 Transmission timing signal T of the spread code _code And a timing detection unit 23 for detecting.
[0030]
The synchronization detection device 2 includes a code generator 25 that generates the two types of codes C1 and C2, a memory 22 that records the correlation energy of the signal determined to be valid by the comparison unit 21 and its timing, And a counter 24 for sending a timing signal to the timing detector 23.
[0031]
The correlation detection unit 15 includes a matched filter 16 ₁ And the matched filter 16 ₂ And a matched filter 16 ₁ The correlation value DI · CI of the code CI with respect to the in-phase component DI is detected by the matched filter 16 ₂ Thus, the correlation value DI · C2 of the code C2 with respect to the in-phase component DI is detected. The correlation detection unit 17 includes a matched filter 18 ₁ And the matched filter 18 ₂ With a matched filter 18 ₁ To detect the correlation value DQ · CI of the code CI with respect to the orthogonal component DQ, and the matched filter 18 ₂ Thus, the correlation value DQ · C2 of the code C2 with respect to the orthogonal component DQ is detected.
[0032]
The configuration of a specific example of the matched filter is shown in FIG. The in-phase component DI or the quadrature component DQ is input to the shift register 31 and sequentially shifted by the clock CLK1. On the other hand, a code Ci (i is 1 or 2) expected to be included in the received signal is input as a correlation coefficient T, and the output of the shift register 31 is multiplied by the correlation coefficient T by the multiplier 32. The sum of the objects is calculated by the adder 33 and is output as a correlation value.
[0033]
Next, at least two types of codes generated by the code generator 25 will be described. In the inter-base station asynchronous system in which the radio signal receiving apparatus 1 is used, a replica code of a spreading code that is supposed to be transmitted as a pilot signal from the base station, a first synchronization code SC1 common to each base station, Based on the second synchronization code SC2 for identifying the spreading code for identifying the spreading code, the transmission timing and the code type of the spreading code sent from the base station are detected. The first synchronization code SC1, the second synchronization code SC2, and the spreading code are included in a pseudorandom noise (PN) code. Here, the first synchronization code SC1 is a synchronization code having a relatively short period common to the base stations. The second synchronization code SC2 is used for narrowing down the timing and type of a spreading code having a relatively long cycle. In this embodiment, the code generator 25 generates the first synchronization code SC1 as the code C1 and the second synchronization code SC2 as the code C2.
[0034]
The correlation energy calculation unit 19 includes a matched filter 16 ₁ The correlation value DI · C1 detected in step A is A, and the matched filter 18 ₁ When the correlation value DQ · C1 detected in step B is B, ² + B ² To calculate the correlation energy Ea. In addition, the correlation energy calculation unit 20 includes the matched filter 16. ₂ Correlation value DI · C2 from A is A, matched filter 18 ₂ When the correlation value DQ · C2 from B is B, A ² + B ² To calculate the correlation energy Eb.
[0035]
The comparison unit 21 has a ratio of correlation energy Ea to correlation energy Eb, and Ea / Eb is arbitrarily settable values R1 and R2 supplied from terminals 27 and 28, if R1 <Ea / Eb <R2. The signal transmitted from the base station is determined to be valid. Further, when the correlation energy Ea and / or Eb exceeds the threshold Th from the terminal 29 and R1 <Ea / Eb <R2 is satisfied, it is determined that the signal transmitted from the base station is valid. May be.
[0036]
The memory 22 records the correlation energy Ea and the correlation energy Eb of the signal determined to be effective by the comparison unit 21 together with the time timing. That is, how much correlation energy is generated at which time timing is recorded.
[0037]
When the time timing of the correlation energy Ea and the correlation energy Eb recorded in the memory 22 coincides with the timing indicated by the count value of the counter 24, the timing detection unit 23 transmits the transmission timing signal T of the spread code. _code And is supplied from the output terminal 26 to the controller 7 of FIG.
[0038]
This radio signal receiving apparatus (CDMA system) employs a diversity RAKE system. That is, as shown in FIG. 10, in addition to the direct path P1 from the base station 101, signals from the path P2 and the path P3 changed by the building 103A and the building 103B are synthesized. Thereby, the influence of fading is reduced and the S / N ratio is improved.
[0039]
The demodulating device 3 of the radio signal receiving device 1 of FIG. 1 adopting the diversity RAKE system has fingers 34, 35, 36 for processing signals of a plurality of paths P1, P2, P3, respectively, and these fingers 34, 35, 36. Is provided with a RAKE combining circuit 37 for combining the output signals from.
[0040]
The fingers 34, 35, 36 have transmission timing signals T detected by the synchronization detector 2. _code Is supplied. In the fingers 34, 35, 36, the transmission timing signal T is transmitted. _code Is recognized as the timing at which the spreading code is received, and this transmission timing signal T _code Is used to despread the in-phase component DI and quadrature component DQ of the paths P1, P2, and P3, and demodulate the signals of the plurality of paths P1, P2, and P3, respectively. These demodulated outputs are combined by the RAKA combining circuit 37.
[0041]
Next, a case where the operation of the radio signal receiving apparatus 1 having the above-described configuration is applied to a mobile communication terminal apparatus in an inter-base station asynchronous system will be described. When this portable communication terminal apparatus is used in an asynchronous system between base stations, it is necessary to determine whether the signal is a multipath signal from the same base station or a signal from another base station. That is, in order to avoid erroneously detecting a path from another base station when searching for a multipath signal from the base station in a mobile communication terminal device that has decided to connect to a base station by cell search It is performed to check whether the signal is from a desired base station.
[0042]
For example, in FIG. 13 described above, the signal S11 of the path P11 having no obstacle and the signal S12 of the path P12 reflected by the building or the like reach the mobile communication terminal device 40 from the first base station 41. In the mobile communication terminal device 40, as shown in the flowchart of FIG. 4, the signal S11 of the path P11 from the first base station 41 and the spreading code that is supposed to be sent from the first base station 41 so far. The correlation value between the replica code (denoted as code 1) and the correlation value between the signal S12 of the path P12 and the code 1 are obtained in step S1, and the correlation energy E1 and the correlation energy E2 (shown in FIG. 14) in step S2. In step S3, the correlation energy E1 and the correlation energy E2 are compared with a predetermined threshold value Th, and when the correlation energy E is larger than the threshold value Th, a correct detection result is obtained. It was.
[0043]
However, as shown in FIG. 13, in the situation where the signal S2 of the path P2 from the second base station 42 reaches the mobile communication terminal device 40, the spreading that is supposed to be sent from the second base station 42 When the energy E3 of the correlation value using the code replica code (code 2) is large as shown in FIG. 14, the energy E3 ′ of the correlation value between the signal S2 of the path P2 and the code 1 is also greater than the threshold Th. As a result, the correlation energy E3 ′ is recognized erroneously, and a path P13 that does not actually exist is erroneously detected.
[0044]
Therefore, in the present embodiment, the synchronization detection device 2 simultaneously determines the correlation values of the two types of synchronization codes SCI (code C1) and SC2 (code C2) with respect to the received signal, and the energy of these correlation values. Ea and Eb are calculated by the energy calculation units 19 and 20, and the comparison unit 21 determines whether or not the ratio Ea / Eb satisfies a predetermined condition. Here, when the correlation energy ratio Ea / Eb does not satisfy the predetermined condition, it is not recorded in the memory 22 as a false detection.
[0045]
The detailed operation of the synchronization detection apparatus will be described below with reference to FIGS. 13, 5, and 6. FIG. The correlation value DI · C1 between the in-phase component DI and the code C1 of the signal S11 of the path P11 in FIG. 13 and the correlation value DQ · C1 between the quadrature component DQ and the code C1 are obtained by the correlation detection unit 15 in step S11 shown in FIG. Matched filter 16 ₁ And the matched filter 18 of the correlation detector 17 ₁ Is detected. The correlation value DI · C1 and the correlation value DQ · C1 are supplied to the A input terminal and the B input terminal of the energy calculation unit 19 in step S12, where A ² + B ² Is calculated to obtain the correlation energy E11 shown in FIG. Similarly, the correlation value DI · C2 between the in-phase component DI and the code C2 of the signal of the path P11 and the correlation value DQ · C2 between the quadrature component DQ and the code C2 are matched filters 16 of the correlation detection unit 15. ₂ And the matched filter 18 of the correlation detector 17 ₂ (Step S11), the correlation value DI · C2 and the correlation value DQ · C2 are supplied to the A input terminal and the B input terminal of the energy calculating unit 20, and the correlation energy E12 shown in FIG. 5 is obtained in Step S12. Desired. Here, the correlation energy E11 and the correlation energy E12 are obtained at the same timing.
[0046]
Next, the correlation energy E11 and the correlation energy E12 are supplied to the comparison unit 21, and in step S13, whether the ratio E11 / E12 is R1 <E11 / E12 <R2 with respect to the values R1 and R2 that can be arbitrarily set. It is determined whether or not. If R1 <E11 / E12 <R2 is satisfied in step S13, it is determined that the signal transmitted from the base station is valid, and the values of the correlation energies E11 and E12 are correct. In step S14, the memory 22 Recorded with time timing.
[0047]
Further, the correlation value DI · C1 between the in-phase component DI of the signal S12 of the path P12 and the code C1, the correlation value DQ · C1 of the quadrature component DQ and the code C1, the in-phase component DI and the code C2 of the signal S12 of the path P12, The correlation value DI · C2 and the correlation value DQ · C2 between the orthogonal component DQ and the code C2 are obtained in the same manner (step S11). Then, the correlation energy calculation unit 19 and the correlation energy calculation unit 20 calculate the correlation energy E21 and the correlation energy E22 shown in FIG. 5 (step S12). The comparison unit 21 determines R1 <E21 / E22 <R2 (step S13). If the signal transmitted from the base station is valid and the values of the correlation energies E21 and E22 are correct, the comparison unit 21 stores the memory 22 in step S14. Record with time timing.
[0048]
Here, as shown in FIG. 13, the second base station for the in-phase component DI2 and the quadrature component DQ2 in a situation where the signal S2 of the path P2 from the second base station 42 reaches the mobile communication terminal device 40. Even when the ratio of the correlation energy E31 of the code C1 from 42 and the correlation energy E32 of the code C2 from the second base station 42 satisfies R1 <E31 / E32 <R2, the second base station The ratio of the correlation energy E31 ′ of the code C1 of the first base station 41 to the in-phase component DI2 and the quadrature component DQ2 of the signal S2 from 42 and the correlation energy E32 ′ of the code C2 from the first base station 41 is If R1 <E31 ′ / E32 ′ <R2 is not satisfied in the determination in step S13, the signal transmitted from the base station is not valid and is not correlated with the correlation energy E31 ′. Energy E32 'is determined to be those incorrect. Therefore, the synchronization detection device 2 does not record the correlation energy E31 ′ and the correlation energy E32 ′, which are erroneous detection results, in the memory 22.
[0049]
As described above, the correlation energies Ea and Eb for the codes C1 and C2 included in one path are simultaneously obtained, and whether or not they are correct is determined by the determining means (step S13), as shown in FIG. Even under the circumstances, the correlation energy E31 ′ and the correlation energy E32 ′ in FIG. 5 are E31 ′ / E32 ′ <R1 or E31 ′ / E32 ′> R2, and the signal transmitted from the base station is not effective, and its correlation The energy is recognized as an incorrect correlation energy, and is not stored in the memory, so that false detection can be avoided.
[0050]
Next, another detailed operation of the synchronization detection apparatus will be described with reference to FIG. In FIG. 2, when the comparison unit 21 uses the threshold value Th input from the terminal 29, the correlation energy Ea and / or Eb exceeds the threshold value Th, and further when R1 <Ea / Eb <R2 is satisfied, This is an operation in which it is determined that the signal transmitted from the station is valid and the correlation energy is correct.
[0051]
The processing of step S21, step S22, step S24 and step S25 is the same as step S11, step S12, step S13 and step S14 shown in FIG. 6, but step S23 is inserted between step S22 and step S24. When the correlation energy Ea and / or Eb exceeds the threshold Th, the process proceeds to step S24. Thus, when the correlation energy Ea and / or Eb exceeds the threshold Th and R1 <Ea / Eb <R2 is satisfied, it is determined that the signal transmitted from the base station is valid, and the correlation energy Is considered correct. In this way, it is possible to more accurately determine the certainty of the correlation energy.
[0052]
Although not shown, instead of step S13 in FIG. 6, a threshold Th for the correlation energy Eb is set based on the correlation energy Ea, and it is determined whether or not the correlation energy Eb exceeds the threshold Th. It may be determined whether a signal received from the base station is valid.
[0053]
The series of synchronization detection processes shown in the flowchart of FIG. 6 and the flowchart of FIG. 7 may be programmed and executed by a computer system. In this case, after step S14 or step S25, the transmission timing signal of the spread code can be detected from the correlation energy and timing information read from the memory in the timing detection process.
[0054]
Further, the computer may use the transmission timing signal of the spread code detected in the timing detection process of the synchronization detection program in the demodulation process, obtain a spread code from the transmission timing signal, and demodulate the received signal. Good. In this case, a program obtained by programming the wireless signal receiving method is executed by a computer system.
[0055]
【The invention's effect】
According to the present invention, the correlation value for at least two types of pseudo-random noise codes is simultaneously obtained for the received signal, and when these ratios are far from the values set as the assumed ratios, the correlation values By making the error as an error, it is possible to reduce erroneous detection of the synchronization signal and improve the accuracy of the multipath search and cell search, so that the accuracy of the multipath search and cell search can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a radio signal receiving apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a detailed configuration of a synchronization detection device included in the wireless signal reception device.
FIG. 3 is a diagram illustrating a specific example of a matched filter included in the synchronization detection device.
FIG. 4 is a flowchart illustrating a synchronization detection method by a conventional mobile communication terminal device.
5 is a characteristic diagram for explaining processing in a comparison unit in the synchronization detection device shown in FIG. 2; FIG.
6 is a flowchart for explaining detailed operations of the synchronization detection apparatus shown in FIG. 2; FIG.
7 is a flowchart for explaining another detailed operation of the synchronization detection apparatus shown in FIG. 2; FIG.
FIG. 8 is a diagram for explaining a DS-CDMA spreading code synchronization method;
FIG. 9 is a diagram illustrating a specific example of a second synchronization code pattern.
FIG. 10 is a diagram for explaining the features of the diversity RAKE method adopted by the CDMA mobile terminal device;
FIG. 11 is a diagram illustrating energy characteristics of signals of different paths in the diversity RAKE method.
FIG. 12 is a diagram for explaining a reception operation of a diversity RAKE mobile communication device;
FIG. 13 is a diagram illustrating a specific example of multipath from a plurality of base stations.
FIG. 14 is a diagram illustrating an example of erroneous detection of multipath.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Radio signal receiver, 2 Synchronization detection apparatus, 3 Demodulation apparatus, 7 Controller, 15 Correlation detection part, 16 ₁ , 16 ₂ Matched filter, 17 correlation detector, 18 ₁ , 18 ₂ Matched filter, 19, 20 Correlation energy calculation unit, 21 Comparison unit, 22 Memory, 23 Timing detection unit, 24 Counter, 25 Code generator

Claims (10)

Correlation detection means for obtaining a correlation value between a signal received from a base station and at least two types of pseudo-random noise codes;
Correlation energy calculation means for obtaining energy of the correlation value obtained by the correlation detection means;
The ratio of the energy of the correlation value of at least two types of pseudo-random noise codes to the in-phase component and quadrature component of the signal obtained by the correlation energy calculation means is between a lower limit value and an upper limit value that can be arbitrarily set. determination means for signals received is equal to or valid from the base station whether the determination to the,
A synchronization detection apparatus comprising: timing detection means for detecting synchronization timing for a spreading code transmitted from the base station based on a signal determined to be effective by the determination means. A correlation detection step for obtaining a correlation value between the signal received from the base station and at least two types of pseudo-random noise codes;
A correlation energy calculation step for obtaining energy of the correlation value obtained in the correlation detection step;
The ratio of the energy of the correlation value of at least two types of pseudo-random noise codes to the in-phase component and quadrature component of the signal obtained in the correlation energy calculation step is between a lower limit value and an upper limit value that can be arbitrarily set. a determining step of the signal received from the base station to determine whether it is valid or whether the determination to the,
A synchronization detection method comprising: a timing detection step of detecting a synchronization timing for a spreading code transmitted from the base station based on a signal determined to be effective in the determination step. Correlation detection means for obtaining a correlation value between a signal received from a base station and at least two types of pseudo-random noise codes;
Correlation energy calculation means for obtaining energy of the correlation value obtained by the correlation detection means;
The ratio of the energy of the correlation value of at least two types of pseudo-random noise codes to the in-phase component and quadrature component of the signal obtained by the correlation energy calculation means is between a lower limit value and an upper limit value that can be arbitrarily set. determination means for signals received is equal to or valid from the base station whether the determination to the,
Timing detection means for detecting a synchronization timing for a spreading code transmitted from the base station, based on a signal determined to be effective by the determination means;
Using the spreading code obtained by the synchronization timing detected by the timing detection means,
A radio signal comprising: demodulation means for despreading a signal transmitted from the base station through a plurality of paths, demodulating the despread signals of the plurality of paths for each path, and combining and outputting a demodulated signal Receiver device. The determination means performs the determination based on a ratio of the correlation energies when any one of the correlation energies and / or other correlation energies exceeds a predetermined threshold. 4. The radio signal receiving apparatus according to claim 3, wherein it is determined whether or not a signal received from the base station is valid.   The determination means sets a threshold for another correlation energy based on any one of the correlation energies, determines whether the other correlation energy exceeds the threshold, and determines the base station The radio signal receiving apparatus according to claim 3, wherein it is determined whether or not the signal received from is valid.   A recording unit for adding timing information to the correlation energy of the signal received from the base station determined to be effective by the determination unit, and recording the timing energy; The radio signal receiving apparatus according to claim 3, wherein synchronization timing for the spreading code is detected from timing information.   The radio signal receiving apparatus according to claim 3, wherein each of the at least two types of pseudo-random noise codes is a synchronization code. 8. The radio signal receiving apparatus according to claim 7 , wherein one of the synchronization codes is a synchronization code common to base stations, and the other is a synchronization code specific to each base station.   4. The radio signal receiving apparatus according to claim 3, wherein the at least two types of pseudo random noise codes are a synchronization code common to base stations and a spreading code of a pilot channel. A correlation detection step for obtaining a correlation value between the signal received from the base station and at least two types of pseudo-random noise codes;
A correlation energy calculation step for obtaining energy of a correlation value obtained in the correlation detection step;
The ratio of the energy of the correlation value of at least two types of pseudo-random noise codes to the in-phase component and quadrature component of the signal obtained in the correlation energy calculation step is between a lower limit value and an upper limit value that can be arbitrarily set. a determining step of the signal received from the base station to determine whether it is valid or whether the determination to the,
Based on the signal determined to be effective in the determination step, a timing detection step of detecting a synchronization timing for the spreading code transmitted from the base station,
A demodulation step of demodulating the received signal based on the spreading code obtained based on the synchronization timing detected in the timing detection step.

Images