JP2000312165A - Cell search method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the capacity of a RAM used when conducting cell searching and to speed up the cell searching. SOLUTION: In this searching method, a power threshold 12 is set for as its comparison with a correlation power detected by a correlation unit 2 and a power processing section 4, and a power memory 14 stores only the correlation power which exceeds the power threshold 12 as a result of comparison by a comparator 13 so as not to store undesired noise level correlation values to the power memory 14, thereby decreasing number of stored power values. Thus, the required capacity of the memory can be reduced, and a processing of searching the largest correlation power among correlation power values stored in the power memory 14 is conducted more speedily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell search method, and is suitable for use in a method and apparatus for synchronizing communication between a mobile communication terminal such as a mobile phone and a base station.

[0002]

2. Description of the Related Art Conventionally, an analog FDMA (Frequency Division Multipl.) In which a plurality of mobile stations such as mobile phones are connected to one base station using different frequencies.
In the eAccess) system, one frequency band is occupied by communication of one mobile station, so that the efficiency of use of each divided frequency band is poor, and the number of persons that can be used in the service area (cell) of the base station There was a problem that can not be many.

At present, instead of the FDMA system, digital TDMA (Time Division Multiple Acces) in which a plurality of mobile stations connect one frequency band in a time-division manner.
s) The method is often used. According to this method, 1
Since communication can be performed by allocating a plurality of mobile stations to one frequency band, more users can be accommodated than in the FDMA system.

However, in the TDMA system, a fragmented signal is transmitted and received between a base station and a plurality of mobile stations in a time-division manner, so that the amount of information communicated by one mobile station is reduced. Therefore, in today's digital mobile phones, etc., in order to be able to communicate more information, a signal is compressed and transmitted by encoding, and it is expanded and reproduced on the receiving side. The sound quality of the voice becomes poor.

Therefore, in recent years, as a communication system that can greatly improve the use efficiency of each frequency band and improve the reproduced sound quality, code division using direct spread type spread spectrum (Spread Spectrum) has been proposed. A multiple access, that is, a CDMA (Code Division Multiple Access) system has been receiving attention.

In this CDMA system, a signal to be transmitted from a base station to a plurality of mobile stations is spread using a unique spreading code for each mobile station, and then transmitted using one frequency band. . On the other hand, the receiving mobile station multiplies the received signal by its own spreading code,
By correlating with the spreading code applied on the transmitting side, a peak value of the correlation is detected and only the signal sent to itself is extracted. According to the CDMA system, it is possible to allocate one frequency band to more mobile stations by using different spreading codes. Also, since the amount of information to be sent can be increased, the sound quality of the reproduced sound is also improved.

By the way, when a mobile station such as a mobile phone is turned on, it must receive a predetermined message from a base station in an area (cell). CD
In the MA system, a message from a base station is repeatedly sent in a predetermined slot unit as shown in FIG. 4, but as shown by an arrow in the figure, the power supply of the mobile station is always transmitted to the slot. The message is not always turned on at the first timing, and the message cannot be read correctly as it is.

Therefore, in order to correctly decode a message contained in a slot, it is necessary to detect the timing at the head of the slot (this is called a cell search) and receive the message therefrom. Also, if the mobile station is powered off
In addition to the above-described initial cell search in which a cell connected at the time of N is first acquired, a cell search is performed. That is, even after the power is turned on, for example, when the mobile station moves across cells, the synchronization may be shifted. Therefore, the synchronization is constantly monitored by periodically performing a cell search.

FIG. 5 is a block diagram showing a configuration of a cell search circuit provided in a mobile station according to a conventional wideband CDMA communication system (direct spreading CDMA system). In FIG. 5, a received signal (a transmission path signal as shown in FIG. 4 transmitted from a base station not shown) has the first bit of each slot indicated by hatching in FIG. A common spreading code prepared separately from the code (25 in one bit)
(The number of chips changing six times = 256 spreading codes). Usually, such a transmission path signal for cell search is transmitted using a common channel (perch channel).

[0010] Such a received signal is supplied to the A / D converter 10.
The digital signal is converted into a digital signal by 1 and is sequentially supplied to the correlator 102 such as a matched filter or a sliding correlator in units of one slot (10 symbols) from the timing when the power of the mobile station is turned on. In the correlator 102, A /
Despreading is performed by calculating the integral of the digital signal input from the D converter 101 and a spreading code generated by the code generator 103 and common to each mobile station.

The in-phase component I and the quadrature component Q of the voltage output from the correlator 102 are supplied to a power conversion unit 104, and are converted into power at each predetermined sampling point in a slot. Then, the power value of each sampling point obtained in this way is sequentially stored in an address corresponding to each sampling point in the memory (RAM) 107 via the adder 106 in the power value integration unit 105.

By performing such processing, a portion having a large correlation with the common spreading code applied by the mobile station within a range of the first one slot after the power of the mobile station is turned on, that is, not shown. Only the power values in the hatched portions in FIG. 4 to which a common spreading code is applied in the base station appear as peaks. Therefore, by detecting this peak portion, the head position of the slot can be confirmed, and the subsequent communication can be performed in accordance with the timing.

[0013] However, as shown in FIG.
One mobile station receives transmission path signals from a plurality of base stations near the mobile station with a delay amount. Also, regarding a signal from one base station, not only a direct wave directly received from the base station, but also a reflected wave that is received after being reflected by a building or the ground. Therefore, in the received transmission path signal, there are many portions spread with the common code in one slot, and many peaks of the power value are also detected in one slot. When the mobile station moves during the cell search, a peak may be detected at a position different from the previous position in the next slot.

Under such circumstances, the peak value of the power value is detected not only for the first slot but also for several slots after the power of the mobile station is turned on. That is, the power integrated value from the RAM 107 to the previous slot is read out for each sampling point and given to the adder 106, and the power value at the same sampling point in the current slot is added and stored in the RAM 107 again. By performing such integration of the power value for, for example, 32 slots, the portion having the largest peak is finally recognized as the leading portion of the transmission path signal transmitted from the nearest base station.

[0015]

However, when a cell search is performed using the above-described conventional method, the RAM 107 storing the power integrated value for each sampling point has
A capacity of 10240 words is required. That is, when the cell search is performed, the number of chips (the number of cycles) in one slot in the perch channel is 256 × 10 = 2560.
It is. Further, in order to improve the accuracy of peak value detection, one chip is divided into four parts and four times oversampling is performed, so that a total of 10240 sampling points in one slot (the chip rate is 4M
cps).

The area of the RAM 107 for storing the power integrated value for 10240 words is several millimeters or more, and the circuit area becomes very large. In particular, it is important to reduce the size and weight of mobile communication terminals such as mobile phones, and it is desired that circuits such as a transmission function, a reception function, and a cell search function be included in one chip. However, the ratio of the cell search circuit to the LSI becomes very large, and the LSI itself cannot be miniaturized.

1024 stored in the RAM 107
Since data having the largest value must be selected from among the zero power integration values, there is a problem that a large processing load is applied and a long time is required until the cell search is completed. For example, there is a problem that a long time is required for an initial cell search at the time of power-on, and a start-up until communication becomes possible is very poor.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it has been made possible to reduce the size of a cell search circuit by reducing the capacity of a RAM used when performing a cell search. It is an object of the present invention to enable a high speed cell search operation.

[0019]

A cell search method according to the present invention detects a correlation value between a spread code generated in a local station and an input signal, and detects a correlation peak value within a predetermined unit slot. A search method, wherein a threshold for comparing with the detected correlation value is provided.

Here, the correlation value exceeding the threshold value may be stored in a memory. Further, the timing information when the correlation value exceeds the threshold value may be stored in the memory together with the storage of the correlation value.

According to the present invention configured as described above, of a plurality of correlation values obtained in a slot, for example, a correlation value exceeding a threshold is registered in a memory, and a correlation value not exceeding a threshold is used as noise data. It will be ignored. As a result, the number of correlation values actually registered in the memory can be reduced as compared with the conventional example in which all detected correlation values are registered in the memory, and the number of words in the memory can be significantly reduced. It becomes possible.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of the cell search circuit according to the present embodiment. The received signal (input signal from the outside) shown in FIG. 1 is a transmission path signal as shown in FIG. 4 transmitted from a base station (not shown), and the first bit of each slot indicated by hatching in FIG. Are spread by a common spreading code (the number of chips = 256) for each mobile station. This received signal is band-limited by a band-limiting filter (not shown) to the frequency band of the signal transmitted by the base station, and then provided to A / D converter 1.

The A / D converter 1 converts the above-mentioned received signal into a digital signal. The correlator 2 is, for example, on a slot-by-slot basis from the timing when the power of the mobile station is turned on.
Despreading is performed by sequentially calculating the integral of the digital signal input from the A / D converter 1 and a spreading code generated by the code generator 3 and common to each mobile station, thereby performing despreading. Detect correlation with signal. This correlator 2
For example, it is configured by a matched filter, a sliding correlator, and the like.

The power conversion section 4 calculates the sum of squares of the in-phase component I and the quadrature component Q of the voltage output from the correlator 2 for each of the 10240 sampling points determined in advance in the slot. Find the value. Further, the power value integration unit 5 integrates the power value output from the power conversion unit 4 for each sampling point for each sampling point over several slots. The A / D converter 1, the correlator 2, the code generator 3, and the power conversion unit 4 are shown in FIG.
Are the same as the conventional A / D converter 101, correlator 102, code generator 103 and power conversion unit 104 shown in FIG.
The power value integration unit 5 is a feature of the present invention.

Hereinafter, the power value integration section 5 will be described in detail. The threshold value checking unit 11 compares the power value output from the power conversion unit 4 with a preset power threshold value 12 at each sampling point by the comparator 13 and determines whether the given power value is larger than the threshold value. Pass
Controls signal active / negative. The power value memory (RAM) 14 is for storing a power value output from the comparator 13 in the threshold value inspection unit 11. The multiplexer 15 selects and reads one of the power values of each sampling point stored at each address in the power value memory 14 and supplies the selected power value to one input terminal of the AND gate 16.

Carry Propercation Adder 1
7 adds the data value output from the AND gate 16 and the power value output from the comparator 13 in the threshold value inspection unit 11 and stores the result in the power value memory 14. For example, when the power integrated value up to the previous slot at a certain sampling point read from the power value memory 14 via the multiplexer 15 has passed through the AND gate 16, the full adder 17 calculates the value of the same sampling point in the current slot. The result is added to the power value, and the addition result is stored at the same address in the power value memory 14.

On the other hand, AND operation is performed by a mask signal described later.
When “0” data is output from the gate 16, the power value at a certain sampling point in the current slot output from the comparator 13 in the threshold value checking unit 11 passes through the full adder 17 as it is, It is stored at a new address in the memory 14.

The point value memory (RAM) 18 is a sampling point value corresponding to the power value stored in the power value memory 14, that is, from the beginning of the slot in one slot measured for each slot by the timer 23. This is for storing timing information such as the relative time (the number of relative cycles) of the data. The multiplexer 19 selects and reads one of the sampling point values stored at each address in the point value memory 18, and supplies it to one input terminal of the comparator 20.

The other input terminal of the comparator 20 receives relative time information (the current sampling point value in the current slot) measured from the beginning of the slot by the timer 23. The comparator 20 compares the current sampling point value with the sampling point value read from the point value memory 18 via the multiplexer 19, and sends a signal indicating whether or not the two values match to the pointer control unit 21. Supply.

The pointer control unit 21 stores the power value memory 14 and the point value memory 18 in accordance with the pass signal supplied from the comparator 13 in the threshold value inspection unit 11 and the match / mismatch signal supplied from the comparator 20. It controls a pointer (address) for reading and writing data. The pointer control unit 21 supplies a mask signal to the other input terminal of the AND gate 16 when a non-coincidence signal is supplied from the comparator 20. In this case, as described above, the power value output from the comparator 13 passes through the full adder 17 as it is and is stored in a new address of the power value memory 14.

The register group 22 is for providing various functions in performing the cell search operation of the present embodiment. Details of this will be described later. The timer 23 counts the relative time (the number of relative cycles) from the beginning of the slot within one slot for each slot. In the case of the present embodiment, for example, the power of the mobile station is turned off.
By starting the reception by setting N, the counting operation is started, and when the count reaches 10239, it is reset to 0 again.

Next, the operation of the power value integrator 5 configured as described above will be described below. First, the operation of the first slot, for example, immediately after the power of the mobile station is turned on will be described. The power value at each sampling point output from the power conversion unit 4 is compared with a power threshold value 12 set in advance by the threshold value inspection unit 11.
The ass signal becomes active. On the other hand, when the power value is equal to or smaller than the threshold value (or smaller than the threshold value), the pass signal remains negative.

Only when the pass signal is active, the obtained power value is stored in order from the upper address of the power value memory 14 via the full adder 17. At the same time as storing this power value, the point value memory 18
, The sampling point value corresponding to the power value exceeding the power threshold 12 is stored in order from the upper address. As a result, the power values exceeding the power threshold 12 and the corresponding sampling point values are sequentially stored in the two memories 14 and 18 at the same address.

As described above, in the first slot in which the integration is performed, the power value exceeding the power threshold value 12 and the corresponding sampling point value are unconditionally registered in the two memories 14 and 18. On the other hand, in the second and subsequent slots, the threshold comparison is performed in the same manner as in the first slot, but the operation when the power value exceeds the power threshold 12 is different from that in the first slot. Note that the power value does not exceed the power threshold 12 and
When the pass signal remains negative, no processing is performed at that sampling point, as in the first slot.

In the second and subsequent slots, the sampling point value when the power value exceeds the power threshold 12 is
A search as to whether or not it has already been stored in the point value memory 18 is performed using the multiplexer 19 and the comparator 20. Here, if it is found that the sampling point value has already been registered in the point value memory 18 in the processing up to the previous slot, the pointer control unit 21 controls the power value integration unit 5 to operate as follows. I do.

That is, of the power integrated values up to the previous slot stored in the power value memory 14, the point value memory 18 storing the sampling point value is stored.
Multiplexer 1 with the same address as above
5 and supplies it to the full adder 17 via the AND gate 16. Then, the power integrated value up to the previous slot thus read and the current power value supplied from the comparator 13 are added by the full adder 17, and the addition result is stored in the same address of the power value memory 14. I do.

On the other hand, if the power value exceeds the power threshold value 12 in the second and subsequent slots, and the sampling point value at that time has not been registered in the point value memory 18 in the processing up to the previous slot, the new value is set. Is stored in a new address of the point value memory 18 and a mask signal is output from the pointer control unit 21, so that the power value output from the comparator 13 is converted into the power value via the full adder 17. It is stored at a new address in the memory 14.

When such power value integration processing is performed over several slots, the power value memory 14 and the point value memory 18 store the integration result of the power value exceeding the power threshold 12 in the processing in each slot. And the sampling point value corresponding to each power integrated value are stored in order from the upper address. Then, data bus 2
DSP (Digita) connected to the power value integrator 5 via
l Signal Processor) 25 selects the largest value among the at least one or more power integrated values stored in the power value memory 14 to determine the position of the sampling point value corresponding to the selected value. Can be recognized as the head of the slot of the transmission path signal sent from the.

As described above, according to the cell search method of the present embodiment, the power threshold 12 is set in advance, and when the data value converted into a power by applying a spreading code is stored in the memory (RAM), the threshold is set to Only data values exceeding the threshold are stored, and data values below the threshold are not stored, so that unnecessary data values of the noise level can be prevented from being stored in the memory from the beginning. The required number of words can be significantly reduced as compared with the conventional case.

For example, when it is desired to detect the integrated correlation power value for the 20 largest waves, the memory capacity should be at least 20 words. Also, assuming that one mobile station receives a direct wave or a reflected wave from the nearest base station, a radio wave from a different base station, or another interfering radio wave, the power detected in one slot is reduced. Even if it is assumed that the peak value is about 80 waves in 20 waves × 4 multipaths, the power value memory 14 and the point value memory 18 need only have a storage capacity of at least that many words. In the example of FIG. 1, the memory has a storage capacity of 128 words with some allowance, but requires much less storage capacity than the conventional 10240 words.

As described above, in the present embodiment, the number of words required as the storage capacity of the RAM can be significantly reduced, so that the circuit area of the RAM can be extremely reduced as compared with the related art.

Also, the process of searching for the data with the largest value from the power integrated values stored in the RAM may be selected from at most 128 power integrated values.
The processing load can be reduced, and the maximum power peak value can be detected at higher speed.

Next, the register group 22 shown in FIG. 1 will be described. The power threshold register 31 is for arbitrarily setting the power threshold 12 to be compared by the comparator 13 in the threshold test unit 11. By rewriting the contents of the power threshold register 31, the user can freely select a desired threshold. For example, when a portable terminal equipped with the cell search circuit of the present embodiment is used in an urban area where buildings are densely populated, the number of peaks existing in one slot is expected to increase. Memory overflow can be prevented. Also, 1
By adjusting the power threshold value 12 according to the registration status of the correlation power value in the slot, despreading can be performed in accordance with the radio wave reception state.

The integration time register 32 is for arbitrarily setting the integration time of the power value in the cell search, that is, the number of slots for integration. By rewriting the contents of the integration time register 32, the user can freely select a desired integration time. For example, in a city where buildings are densely populated, the number of peaks existing in one slot is expected to increase. Therefore, by setting a large number of slots to be integrated, cell search can be performed with higher accuracy. On the other hand, when a mobile terminal or the like is used in a region where there are few reflected waves or interfering waves, the cell search can be executed at a higher speed by setting the number of slots small.

The control register 33 is for starting the cell search operation or clearing the pointers of the memories 14 and 18 when the cell search operation is stopped halfway. That is, a start bit is prepared in a certain area of the control register 33, and when "1" is written therein, a cell search operation is started. 1
The relative time in the slot is counted by the timer 23 starting from the start timing. A reset bit is also provided in other areas of the control register 33. When "1" is written in this area, only the pointers of the memories 14 and 18 are cleared.
The control register 33 is provided to ensure that an abnormal operation or the like occurs in a test stage before the product is shipped.

The time information register 34 is a register for reading out time information (sampling point value) stored in the point value memory 18 on the data bus 24 as a result of the cell search. That is, when the time information register 34 is read, the time information stored in the point value memory 18 is sequentially read in a form of being incremented one by one, and is output via the data bus 24.

The time information register 34 is used, for example, when detecting the maximum value from the power integrated values stored in the power value memory 14 by the cell search operation and grasping the corresponding sampling point value. . Also,
By reading out all the time information in the point value memory 18 at the test stage before the product is shipped, it can be used for verifying at what time and how many peaks appear.

The power integrated value register 35 is a register for reading out the power integrated value stored in the power value memory 14 on the data bus 24 as a result of the cell search. That is, when the power integrated value register 35 is read, the power integrated values stored in the power value memory 14 are sequentially read in a form of being incremented one by one.
Is output via. This power integration value register 35
For example, it is used when the maximum value is detected from the power integrated values stored in the power value memory 14 by the cell search operation.

The status register 36 indicates whether the cell search operation has been completed to the end or the power value exceeding the power threshold 12 is too large, and the power value memory 14 and the point value memory 18 overflow during the cell search. This is for notifying the DSP 25 via the data bus 24 of the state of whether the data has been lost. By displaying the contents of the status register 36 notified to the DSP 25 on a display unit (not shown), the user can know the state of the cell search operation. For example, by using this status register 36 in a test stage before product shipment,
It is possible to verify what the default value of the power threshold value 12 should be, how many words should be prepared as the storage capacity of the power value memory 14 and the point value memory 18, and the like.

The registration number register 37 stores the result of the cell search in the power value memory 14 and the point value memory 18.
This is for notifying the DSP 25 of how many words the power integration value and the corresponding sampling point value have been registered. For example, when it is confirmed from the contents of the status register 33 that the cell search has been completed to the end, the number of words actually registered is known by looking at the contents of the registration number register 37 next. In this case, by reading the power integrated value from the power integrated value register 35 at least for the number of words, the maximum peak value can be detected, so that the cell search processing time can be shortened.

As described above, the cell search method according to the present embodiment is realized by the circuit configuration as shown in FIG. 1, but the program stored in the RAM or ROM of the computer operates. Can also be realized. FIG. 2 is a block diagram showing a configuration example when the cell search method described in FIG. 1 is realized by software. In FIG. 2, the same blocks as those shown in FIG. 1 are denoted by the same reference numerals.

In FIG. 2, a ROM 41 is a read-only memory that stores a program for executing the cell search operation of the present embodiment and various other necessary data. The RAM 42 is a random access memory for temporarily storing various data obtained in the course of the cell search operation based on the above program, and for storing data finally obtained by the cell search. It is. The RAM 42 includes the power value memory 14 and the point value memory 18 shown in FIG. Further, the program may be stored in the RAM 42.

The operation unit 43 is used to perform operations necessary when the user uses the portable terminal to make a call, and to perform operations required for the register group 2.
2 is used to make desired settings for the various registers 31 to 37 shown in FIG. The display unit 44 displays various settings in the register group 22 and displays various messages.

The DSP (CPU) 25 as the control means
According to the program stored in the ROM 41 or the RAM 42, the operations of the correlator 2, the power conversion unit 4 and the power value integration unit 5 shown in FIG. 1 are mainly performed, and the power integration value stored in the RAM 42 by the cell search. For example, a process of detecting the maximum value from among the above and searching for the head of the slot is performed. Here, the operation of the correlator 2 and the power conversion unit 4 is also performed by the DSP 25.
Alternatively, the correlator 2 and the power conversion unit 4 may be provided separately from the control unit 5 and executed.

The I / F unit 45 performs processing such as taking in a signal received by a receiving unit (not shown) or transmitting various signals to a transmitting unit (not shown). This I / F
The unit 45 is also used when reading a program that causes the DSP 25 to perform the cell search function. For example, a program for realizing the cell search method of the present embodiment is recorded on a recording medium such as a CD-ROM, and supplied to the RAM 42 or a hard disk (not shown) via the I / F unit 45. As a recording medium for supplying the program, a floppy disk, a hard disk, a magnetic tape, a magneto-optical disk, a nonvolatile memory card, or the like can be used in addition to the CD-ROM.

FIG. 3 is a flow chart showing the operation when the cell search is executed by software processing.

In FIG. 3, when reception of a transmission path signal from the base station is started in step S1, step S2
Then, the timer 23 for counting the relative time (the number of relative cycles) from the beginning of the slot in one slot for each slot is started, and the process proceeds to step S3.

In step S3, it is determined whether or not the integration has been completed to the end, that is, whether or not the integration has been performed for a preset number of slots. Here, if the integration has been completed to the end, the cell search operation is completed. If the remaining slots still remain, the process further proceeds to step S4 to determine whether the timer 23 has completed counting for one slot. to decide. If the counting for one slot has been completed, the timer 23 is reset in step S5, and then the process proceeds to step S6. If it is still in the middle of the slot, the process proceeds to step S6 without performing any processing.

In step S6, the correlation between the local station spread code and the received signal is detected for the sampling point currently being processed, and the detected correlation value is converted to power. Then, in step S7, it is determined whether or not the correlation value (correlation power value) thus converted into an electric power is larger than a preset threshold value. Here, if the correlation power value is larger than the threshold, the process proceeds to step S8,
It is further determined whether or not the slot currently targeted for integration is the first slot after starting reception.

If the integration has been performed for the first slot, the process proceeds to step S11, where the correlation power value obtained in step S6 is written to a new address of the RAM 42 (corresponding to the power value memory 14 in FIG. 1), and a timer 23
The corresponding time information (relative time from the beginning of the slot) counted by the above is written to a new address of the RAM 42 (corresponding to the point value memory 18 in FIG. 1). Then, after the sampling point is advanced by one in step S12, the process returns to step S3, and the same processing is performed for the next sampling point.

On the other hand, if the slot to be integrated is not the first slot, that is, if it is the second slot or later, the process proceeds from step S8 to step S9, where the same time information as the current sampling point time information is stored in the RAM 42. It is determined whether or not the data has already been stored in the (point value memory 18). If the same time information has been stored, the process proceeds to step S10, and the power integrated value corresponding to the time information (sampling point value) up to that time is represented by R
Integration is performed by reading from the AM 42 and adding the power value obtained this time to it, and the integration result is stored at the same address on the RAM 42.

If the same time information is not stored in the RAM 42, the process proceeds to step S11, where the newly obtained correlation power value is written to a new address of the RAM 42 (power value memory 14), and the corresponding time information is stored. Is written to a new address of the RAM 42 (point value memory 18). Step S10 or step S1
When the process of 1 is completed, the sampling point is advanced by one in step S12, and then the process returns to step S3, and the same process is performed for the next sampling point.

The above is the operation in the case where the correlation power value at a certain sampling point is larger than the preset threshold. If it is determined in step S7 that the correlation power value is equal to or smaller than the threshold, steps S8 to S8 are performed. The process of step S11 returns to step S3 via step S12 without performing anything, and moves to the process of the next sampling point. As described above, in the present embodiment, the correlation power value is stored in the RAM 42 only when the obtained correlation power value is larger than the threshold, and otherwise, the storage in the RAM 42 is not performed.

As a result, the storage capacity of the RAM 42 can be remarkably reduced as compared with the related art, and the circuit area of the RAM 42 can be extremely reduced. Furthermore, RAM4
Also, the processing load of the DSP 25 for searching for the data having the largest value from the power integrated values stored in 2 can be reduced, and the cell search operation can be performed at higher speed.

In the above-described embodiment, two types of voltage information of the in-phase component I and the quadrature component Q obtained by the correlator 2 are converted into electric power, and an integration operation is performed on the converted correlation value. However, the integration operation may be performed on each of two types of correlation values of the in-phase component I and the quadrature component Q. In this case, two types of thresholds are prepared for the in-phase component I and the quadrature component Q.

In the above embodiment, the power value exceeding the threshold value is stored in the memory in order to integrate the power value over several slots. On the contrary,
If the transmission path signal from the base station is transmitted with higher power, the head of the slot can be detected only by detecting the peak power value within the range of the first one slot. Need not be performed. Therefore, in this case, for example, every time a power value exceeding the threshold is detected,
By performing the process of leaving the larger value, it is not necessary to save the power value.

In the embodiment shown in FIG. 1, the power value memory 14 and the point value memory 18 are provided separately.
One RAM may store both the correlation power value and the corresponding time information. For example, if the correlation power value and the corresponding time information are stored in one word, the pointer control by the pointer control unit 21 can be further simplified.

In the embodiment shown in FIG. 1, the output signal of the multiplexer 15 and the mask signal are input to the input terminal of the AND gate 16. The signal is output when the signal is supplied. When the output signal of the comparator 13 and the mask signal are input to the input terminal of the AND gate 16 and the pass signal is negative (the detected correlation power The mask signal may be output when the value does not exceed the power threshold value 12).

In this way, when the obtained correlation power value does not exceed the threshold value and the pass signal is negative,
The full adder 17 has the output signal of the multiplexer 15
Since "0" data is input from the D gate 16,
The contents stored in the power value memory 14 are maintained as they are. Also, if the calculated correlation power value exceeds the threshold value and p
When the ass signal becomes active, the correlation power value output from the comparator 13 passes through the AND gate 16 and is supplied to one input terminal of the full adder 17.

At this time, when the existing power integrated value is read from the power value memory 14 by the multiplexer 15 to the other input terminal of the full adder 17, the value is output from the comparator 13. The calculated correlation power value obtained this time is added and stored at the same address. On the other hand, if the correlation power value of the same sampling point is not stored in the processing up to the previous slot, and a new address is designated as an area for storing the correlation power value this time,
The correlation power value output from the comparator 13 is directly stored in a new address of the power value memory 14 via the full adder 17.

In the embodiment of FIG. 2, it is determined in step S8 whether the slot is the first slot or a subsequent slot, and the processing is divided according to the determination result. Even if the processing is performed in the same manner as described above, the same result is eventually obtained, and therefore the processing in step S8 is not necessarily required.

In the above embodiment, the initial cell search when the power of the portable terminal is turned on has been particularly described. However, the present invention is similarly applied to the cell search performed during the standby state. Is possible.

The cell search system according to the present invention can be applied not only to mobile communications such as mobile phones and satellite communications, but also to digital televisions and the like.

Further, the configurations and connection relations of the respective parts in the circuit shown in the above embodiment are merely examples of the embodiment for carrying out the present invention, and the technical scope of the present invention is not limited thereto. Should not be construed as limiting. That is, the present invention can be embodied in various forms without departing from the spirit or main features thereof.

The following is a summary of various embodiments of the present invention. (1) A cell search method for detecting a correlation value between a spread code generated in the own station and an input signal and detecting a correlation peak value within a slot of a predetermined unit, and comparing the detected correlation value with the detected correlation value A cell search method characterized by providing a threshold value for performing a cell search. (2) The cell search method according to (1), wherein the correlation value exceeding the threshold value is stored in a memory. (3) The cell search method according to (2), wherein timing information when the correlation value exceeds the threshold value is stored in a memory. (4) The correlation value detection process in the slot is performed over several slots, the correlation value obtained in each slot is integrated to detect the correlation peak value, and after the integration is started, The cell search method according to (3), wherein in the first slot, the correlation value exceeding the threshold value and the timing information corresponding thereto are unconditionally stored in a new area of the memory. (5) The process of detecting the correlation value in the slot is performed over several slots, the correlation value obtained in each slot is integrated to detect the correlation peak value, and after the integration is started, In the second and subsequent slots, when the timing information when the correlation value exceeds the threshold value matches the timing information already stored in the memory, the correlation value already stored in the memory is used. The cell search method according to (3) or (4), wherein the integration is performed, and the result is stored in the same area. (6) The detection process of the correlation value in the slot is performed over several slots, the correlation value obtained in each slot is integrated to detect the correlation peak value, and after the integration is started, In the second and subsequent slots, when the timing information when the correlation value exceeds the threshold value does not match the timing information already stored in the memory, the correlation value and the corresponding timing information are compared. Is stored in a new area of the memory, the cell search method according to any one of the above (3) to (5). (7) The cell search method according to any one of (1) to (6), wherein the threshold can be arbitrarily set. (8) The cell search method according to any one of (4) to (7), wherein the number of times of performing the integration can be arbitrarily set. (9) A communication synchronizer for detecting a correlation value between a spread code generated in the local station and an input signal and detecting a synchronization point of the input signal by detecting a correlation peak value within a predetermined unit slot. A communication synchronization device, further comprising a comparison unit for comparing the detected correlation value with a predetermined threshold value. (10) The communication synchronization device according to (9), further including a first storage unit that stores a correlation value exceeding the threshold value as a result of the comparison by the comparison unit. (11) The communication synchronization device according to (10), further including a second storage unit that stores timing information when the correlation value exceeds the threshold value. (12) Correlation value detection means for detecting the correlation value in the slot over several slots and integrating the correlation value obtained in each slot is provided. The correlation value exceeding the threshold value and the timing information corresponding to the correlation value are unconditionally stored in a new area of the first and second storage means. When the timing information at the time of exceeding the value coincides with the timing information already stored in the second storage means, integration is performed using the correlation value already stored in the first storage means. The result is stored in the same area, and conversely, if they do not match, the correlation value and the corresponding timing information are stored in a new area of the first and second storage means. (11 Synchronizer communications described. (13) The above (11) or (1), wherein the first and second storage means are constituted by one memory.
A communication synchronization device according to 2). (14) The communication synchronization device according to any one of (9) to (13), further including a register unit for arbitrarily setting the threshold value. (15) A register means for arbitrarily setting the number of times of performing the integration is provided.
(14) The communication synchronization device according to any one of (14). (16) The communication according to any one of the above (9) to (15), further comprising an end notification unit for notifying when the correlation peak value detection processing is completed to the end. Synchronizer. (17) When there is a shortage of at least one of the first and second storage means, an overflow notification means is provided for notifying the shortage of the storage area. A communication synchronization device according to any one of the preceding claims. (18) The communication synchronization according to any one of (9) to (17), further including a registration number notification unit that notifies the number of correlation values stored in the first storage unit. apparatus. (19) The above (12) to (18), wherein the integration over the several slots is started after activation is started.
A communication synchronization device according to any one of the preceding claims. (20) A communication synchronizer that detects a correlation value between a spread code generated in the local station and an input signal and detects a synchronization point of the input signal by detecting a correlation peak value in a predetermined unit slot. 3. The computer-readable recording medium according to claim 1, wherein a program for causing a computer to function as comparison means for comparing the detected correlation value with a predetermined threshold value is recorded. (21) A program for causing a computer to further function as control means for controlling the correlation value exceeding the threshold value to be stored in a memory as a result of the comparison by the comparison means is recorded. The computer-readable recording medium according to (20). (22) A program for causing a computer to further realize a function as control means for controlling to store timing information when the correlation value exceeds the threshold value in a memory is recorded. The recording medium which can be read by a computer according to (1).

[0077]

As described above, according to the present invention, a threshold value for comparing with a detected correlation value is provided, and only a correlation value exceeding the threshold value is stored in a memory. Such a correlation value can be prevented from being stored in the memory, and the number of correlation values to be stored can be reduced. As a result, the required storage capacity of the memory can be significantly reduced as compared with the related art, and the physical circuit area of the memory can be significantly reduced. Further, it is possible to reduce the load of the process of searching for the largest correlation value from the correlation values stored in the memory, and it is also possible to detect the correlation peak value at a higher speed. As a result, for example, in a wideband CDMA mobile phone, it is possible to increase the speed of cell search and reduce the size of the circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a cell search circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example when the cell search method according to the present embodiment is implemented by software.

FIG. 3 is a flowchart illustrating a cell search method according to the embodiment;

FIG. 4 is a diagram for explaining a cell search operation.

FIG. 5 is a block diagram showing a configuration of a conventional cell search circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 A / D converter 2 Correlator 3 Code generator 4 Power supply unit 5 Power value integration unit 11 Threshold check unit 12 Power threshold 13 Comparator 14 Power value memory 15 Multiplexer 16 AND gate 17 Full adder 18 Point value memory 19 Multiplexer 20 Comparator 21 Pointer control unit 22 Register group 23 Timer 24 Data bus 25 DSP (CPU) 31 Power threshold register 32 Integration time register 33 Control register 34 Time information register 35 Power integrated value register 36 Status register 37 Registration number register 41 ROM 42 RAM 43 operation unit 44 display unit 45 I / F unit

Continued on the front page (72) Inventor Masahiro Hikita 4-1-1 Kamikadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Shoji Taniguchi 4-1-1 Kamikadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Limited F term (reference) 5K022 EE02 EE36 5K047 AA02 AA16 BB01 CC01 GG34 GG37 HH15 MM24 MM35 5K067 AA14 AA42 BB04 CC00 CC10 EE02 EE10 EE71 GG11 HH22 HH23 JJ00

Claims (6)

[Claims] 1. A cell search method for detecting a correlation value between a spread code generated in a local station and an input signal and detecting a correlation peak value within a slot of a predetermined unit. A cell search method, wherein a threshold value for comparing with a cell search is provided. 2. The cell search method according to claim 1, wherein a correlation value exceeding the threshold value is stored in a memory. 3. The cell search method according to claim 2, wherein timing information when said correlation value exceeds said threshold value is stored in a memory. 4. A process of detecting a correlation value in the slot over several slots, integrating the correlation value obtained in each slot to detect the correlation peak value, and starting the integration. 4. The cell search method according to claim 3, wherein, in a first slot after that, the correlation value exceeding the threshold value and the timing information corresponding to the correlation value are unconditionally stored in a new area of the memory. 5. A process for detecting a correlation value in the slot over several slots, integrating the correlation value obtained in each slot to detect the correlation peak value, and starting the integration. In the second and subsequent slots, the timing information when the correlation value exceeds the threshold is
5. The method according to claim 3, wherein when the timing information coincides with the timing information already stored in the memory, integration is performed using the correlation value already stored in the memory, and the result is stored in the same area. The cell search method described in 1. 6. A process of detecting a correlation value in the slot over several slots, integrating the correlation value obtained in each slot to detect the correlation peak value, and starting the integration. In the second and subsequent slots, the timing information when the correlation value exceeds the threshold is
6. The method according to claim 3, wherein when the timing information does not match the timing information already stored in the memory, the correlation value and the corresponding timing information are stored in a new area of the memory. 2. The cell search method according to claim 1.