JP2001189681A - Communication synchronizing device and portable terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a mobile communication terminal by reducing the circuit size of a RAM that is used when the cell search operation is carried out. SOLUTION: The correlation value is detected by a correlator 2 between the received signal and the diffusion code that is generated by a coder generator 3 of its own station and the correlation value which is detected in every slot is integrated over several slots by a power integration part 5. In such a constitution of a device which performs a cell search operation, a DRAM 7 is used to store the integrating results of the correlation value to reduce the constitution of a memory itself in comparison with a conventional SRAM. In addition, a data access occurs in the refresh cycle of the DRAM 7 by an integrating operation. Thereby no control constitution is required for a refresh operation and the memory circuit scale can be significantly reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication synchronization device and a portable terminal device, and more particularly to a communication synchronization device and a portable terminal device suitable for use in a device for synchronizing communication between a mobile communication terminal such as a portable telephone and a base station. It is.

[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 transmitted in a predetermined slot unit as shown in FIG. 3, 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. 4 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. 4, a received signal (a transmission path signal as shown in FIG. 3 transmitted from a base station not shown) has a leading 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] The in-phase component I and the quadrature component Q of the voltage of the received signal are converted into digital signals by the A / D converter 101, and are output from the timing when the power supply of the mobile station is turned on.
Each slot (10 symbols) is sequentially applied to a correlator 102 such as a matched filter or a sliding correlator. The correlator 102 performs despreading by calculating the integral of the digital signal input from the A / D converter 101 and a spreading code generated by the code generator 103 and common to each mobile station.

FIG. 5 is a block diagram showing a configuration example of the correlator 102. The correlator 102 for calculating the integral of the input digital signal composed of 256 chips per symbol and the common spreading code can be constituted by 256 taps. However, in this case, the correlator 102 becomes large.
Therefore, as shown in FIG.
Has been proposed to perform integration 16 times, add the respective integration results, and output the result.

That is, fifteen SRAs of # 1 to # 15
M202 to 204 store the integration results for 15 times sequentially calculated for each of the in-phase component I and the quadrature component Q of the voltage by the 16-tap correlator 201. Adder 2
05 and 206 are the 15 SRAMs 202 to 20.
4 and the 16th integration result currently output from the 16-tap correlator 201 are all added together and output. Here, the adder 205 performs addition on the in-phase component I of the voltage, and the adder 206 performs addition on the quadrature component Q of the voltage.

The in-phase component I and the quadrature component Q of the voltage output from the correlator 102 are supplied to the power conversion unit 104 in FIG. 4 and are converted into power at each sampling point predetermined in the slot. . The power value of each sampling point obtained in this manner is added to the static RA value through the adder 106 in the power value integration unit 105.
M (SRAM) 107 is sequentially stored at an address corresponding to each sampling point.

By performing such processing, a portion having a large correlation with the common spreading code applied by the mobile station within the 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. 3 to which a common spreading code has been 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.

However, as shown in FIG. 3, actually,
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 one slot but also for several slots after the power of the mobile station is turned on. That is, the power integrated value from the RSAM 107 to the previous slot is read out for each sampling point and given to the adder 106, the power value of the same sampling point in the current slot is added and stored in the SRAM 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.

[0017]

However, when a cell search is performed using the above-described conventional method, a capacity of 10240 words is required for the SRAM 107 that stores the power integrated value for each sampling point. That is, when a cell search is performed, the number of chips (number of cycles) in one slot in the perch channel is 256 × 10 = 2.
560. In addition, in order to improve the accuracy of peak value detection, one chip is divided into four parts and four times oversampling is performed. Therefore, the number of sampling points in one slot is 10240 in total (the chip rate is 4 Mcps). in the case of).

The area of the SRAM 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.

When the correlator 102 has 16 taps as shown in FIG. 5, the correlation value calculated by the 16-tap correlator 201, that is, the integral value of the input digital signal and the common spreading code is stored. Multiple SRAMs 202-2
04 is required. Then, these SRAMs 202 to
204 also requires a large memory capacity, and has been a bottleneck in reducing the size and weight of the mobile communication terminal.

The present invention has been made to solve such a problem, and realizes a further miniaturization of a mobile communication terminal by reducing a circuit area of a RAM used when performing a cell search. The purpose is to be able to.

[0021]

SUMMARY OF THE INVENTION A communication synchronizer according to the present invention detects a correlation value between a spread code generated in its own station and an input signal, and detects a correlation peak value within a predetermined unit slot. A communication synchronization device for performing a cell search operation, wherein a dynamic RAM is used as a memory means used when performing the cell search operation.
For example, a dynamic RAM is used as a memory for storing the integration result when performing the cell search operation. Here, in the dynamic RAM, data access occurs within a refresh cycle.

Further, the portable terminal device of the present invention is characterized in that a dynamic RAM is used as a memory means in a portable telephone which performs at least voice communication via a wireless line. Here, in the dynamic RAM, data access occurs within a refresh cycle.

According to the present invention configured as described above, the memory means conventionally constituted by a static RAM (SRAM) is replaced by a dynamic RAM (DRAM), and the structure of the memory means is simplified. In the DRAM used in the present invention, since data access occurs within a refresh cycle, the refresh operation does not need to be performed, and a control configuration for performing the refresh is not required.

[0024]

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 a cell search circuit which is an embodiment of a communication synchronization device included in the portable terminal device of the present invention.

As shown in FIG. 1, the cell search circuit of this embodiment comprises an A / D converter 1, a correlator 2, a code generator 3,
It is composed of a power conversion section 4 and a power value integration section 5. Among them, the A / D converter 1, the code generator 3, and the power conversion unit 4 are the conventional A / D converter 101 shown in FIG.
The code generator 103 and the power conversion unit 104 are the same as the code generator 103, but the correlator 2 and the power value integration unit 5 are features of the present embodiment.

The received signal (input signal from outside) shown in FIG. 1 is a transmission path signal as shown in FIG. 3 transmitted from a base station (not shown). The bits are spread by a spreading code (number of chips = 256) common to each mobile station. The in-phase component I and the quadrature component Q of the voltage of the received signal are band-limited to a frequency band of the signal transmitted by the base station by a band-limiting filter (not shown), and then supplied to the 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, in units of one slot 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 unit 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 predetermined in the slot, Find the power value of the correlation. 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 power value integration section 5 stores the power integrated value (integrated correlation value) up to the previous slot in the DRAM 7 and the power integrated value up to the previous slot stored in the DRAM 7 and is given by the power conversion section 4. An adder 6 for adding the power value in the current slot to the same sampling point is provided. The adder 6 and the DRAM 7 are used to integrate the power value.

That is, the correlation power values output from the power conversion unit 4 for each sampling point are stored in order from the top address of the power value memory configured by the DRAM 7. Here, 1 slot (625 μsec)
The power values at each of the 0240 sampling points are sequentially stored in the DRAM 7 of 10240 words.

The 10 stored in the DRAM 7
The peak point is extracted from the 240 correlation power values to detect the head of the slot. However, the reliability of the data of only one slot is poor, and the head of the slot may be erroneously determined. To prevent this, 10240
By integrating the correlation power value of a point over several slots, the reliability of data for detecting a correlation peak is improved.

That is, the power integrated value from the DRAM 7 to the previous slot is read out for each sampling point and given to the adder 6, and the power value at the same sampling point in the current slot is added and stored in the DRAM 7 again. By performing such integration of the power value for, for example, 32 slots, a portion having the largest peak in the end is
It recognizes that it is the head of the transmission path signal sent from the nearest base station.

Here, the characteristics of the DRAM will be described.
In a DRAM, a memory cell as a storage element in the DRAM is formed of a capacitor. Therefore, unless the charges are recharged at regular intervals, the contents stored in the memory cells are lost. The operation of applying a charge to the capacitor every fixed period is called a refresh, and the cycle is called a refresh cycle.

A DRAM requiring this refresh has conventionally been used as a main memory or an extended memory of a personal computer, a workstation or the like. That is, D
When a RAM is used, a control configuration for performing refreshing other than the memory cells is required, and a large load is applied to the control. Therefore, in consideration of a disadvantage of maintaining data in a memory cell, a DRAM is not used in a small mobile communication terminal such as a mobile phone.

However, when a method of integrating the power value over several slots as in the CDMA communication system is used, data access (power from the DRAM 7 to the previous slot) is performed instead of refreshing which is a feature of DRAM. If the integrated value is read out and added to the power value in the current slot provided by the power conversion unit 4 and written, the refresh control can be made unnecessary. In fact, the time for one slot is 625 μsec, which is shorter than the refresh cycle, so that the refresh operation is not required during integration.

In the last cycle of the integration, the adder 6
In the above, peak detection is performed while performing addition 10240 times, and the address of the DRAM 7 which is the peak point is a static memory (for example, not shown in FIG. 1).
(SRAM, flip-flop, etc.), the integration result of 10240 points will be
It can be gone from above. Therefore, the refresh operation is not required even after the last cycle of integration.

As described above, in the present embodiment, the DRAM 7 is used as the power value memory in the power value integration unit 5. As is well known, the memory cell of the DRAM 7 can be configured much more easily than the memory cell of the SRAM. Further, in the DRAM 7 of the present embodiment, a control configuration for refresh which is normally required can be omitted.

Therefore, the circuit area of the power value memory used for performing the cell search can be significantly reduced. As a result, even in a wideband CDMA type portable terminal device requiring a relatively large memory capacity, the data memory is reduced to about one-fourth the size of the conventional case where the power value memory is configured by the SRAM. Now it can be realized.

In the conventional FDMA communication system and TDMA communication system, a large amount of memory capacity was not required. Therefore, even if SRAM was used as the internal memory, the circuit area rarely became a problem. In contrast, C
Since a large amount of memory capacity is required in the DMA communication method, the circuit area becomes very large if it is configured by an SRAM. Therefore, this internal memory is
The advantages obtained by configuring with the RAM 7 are as follows.
It will be very large.

In the above description, an example has been described in which the internal memory of the power value integration unit 5 is constituted by the DRAM 7. However, this is another data memory used in a mobile communication terminal that requires miniaturization. Is a memory where data access occurs in a short cycle,
A DRAM can be used for such a memory as well. For example, in the correlator 2 such as a matched filter for detecting the correlation between the input digital signal and the common spreading code, the internal memory can be configured by a DRAM.

FIG. 2 is a block diagram showing a configuration example of the correlator 2 according to the present embodiment. The correlator 2 of the present embodiment includes:
16 tap correlator 11 and 15 DRs of # 1 to # 15
AMs 12 to 14 and two adders 15 and 16 are provided. The entire slot is spread by 256 chips, but in detail, 16 pieces of data spread by 16 chips are continuous. Therefore, using the 16-tap correlator 11
The integration is performed six times, and the respective integration results are added and output.

That is, the 15 DRAMs 12 to 1
4 is sequentially calculated for each of the in-phase component I and the quadrature component Q of the voltage by the 16-tap correlator 11.
Stores the integration result of the batch. Also, two adders 15,
Reference numeral 16 denotes each of the first to fifteenth integration results stored in these 15 DRAMs 12 to 14 and the 16-tap correlator 11
, And the 16th integration result that is currently output from. Here, the adder 15 performs addition on the in-phase component I of the voltage, and the adder 16 performs addition on the quadrature component Q of the voltage.

As described above, in the present embodiment, the internal memory of the power value integrator 5 is not only constituted by the DRAM 7 but also the internal memory of the correlator 2 is constituted by the DRAMs 12 to 1.
4. As described above, the time of one slot is 625 μsec, which is shorter than the refresh cycle. Therefore, the refresh operation is not required during integration using the DRAMs 12 to 14. Also, in the final cycle of integration, after all the integrated values are added and output by the adders 15 and 16, the integration results in the DRAMs 12 to 14 may be lost thereafter. Therefore, the refresh operation is not required even after the last cycle of integration.

Thus, in the present embodiment, the internal memory of the correlator 2 can be realized with a very simple configuration.
The circuit area of the memory used when performing the cell search can be further reduced.

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 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. Also,
The cell search system according to the present invention can be applied to digital television and the like in addition to mobile communication such as a mobile phone and satellite communication.

Further, the configurations and connection relations of the components 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.

[0048]

According to the present invention, as described above, a dynamic R is used as a memory means used for performing a cell search operation.
Since the AM is used, the static RA
The configuration of the memory itself can be reduced as compared with the conventional configuration using M. Further, in the present invention, since data access occurs in the dynamic RAM within a refresh cycle, a control structure for performing refresh is not required, and the circuit scale of the memory means can be significantly reduced. Thereby, for example, a wideband CD
Even in a portable terminal device requiring a relatively large memory capacity of the MA system, the size of the device can be reduced.

[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 of a correlator of the present embodiment.

FIG. 3 is a diagram for explaining a cell search operation.

FIG. 4 is a block diagram showing a configuration of a conventional cell search circuit.

FIG. 5 is a block diagram showing a configuration example of a conventional correlator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 A / D converter 2 Correlator 3 Code generator 4 Power supply part 5 Power value integration part 6 Adder 7 DRAM 11 16 tap correlator 12-14 DRAM 15,16 Adder

Continuation of the front page (72) Inventor Masami Kanasugi 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Masahiro Hikita 4-1-1 Kamikadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture No. Fujitsu Limited F term (reference) 5K022 EE02 EE36 5K027 AA10 AA11 CC08 EE00 5K047 AA16 CC01 GG34 GG37 HH01 HH03 HH15 MM24 5K067 AA42 CC00 CC10 DD25 EE02 EE10 GG11 HH21 KK15

Claims (7)

[Claims] 1. A communication synchronizer for detecting a correlation value between a spreading code generated in a local station and an input signal and performing a cell search operation for detecting a correlation peak value within a predetermined unit slot, A communication synchronization apparatus, wherein a dynamic RAM is used as a memory means used when performing the cell search operation. 2. The communication synchronization apparatus according to claim 1, wherein a dynamic RAM is used as a memory means for storing an integration result when performing the cell search operation. 3. The communication synchronization apparatus according to claim 1, wherein a data access occurs in the dynamic RAM within a refresh cycle. 4. A process for detecting a correlation value between a spread code generated in the own station and an input signal is performed over several slots for each predetermined unit slot, and a correlation value obtained by integrating each slot is integrated. What is claimed is: 1. A communication synchronizer for performing a cell search operation for detecting a peak value, wherein a dynamic RAM is used as a memory unit for accumulating an integration result of the correlation value. 5. A process for detecting a correlation value between a spread code generated in the own station and an input signal is performed over several slots for each predetermined unit slot, and a correlation value obtained by integrating the correlation value obtained in each slot is obtained. What is claimed is: 1. A communication synchronizer for performing a cell search operation for detecting a peak value, comprising: detecting a correlation value for each small unit obtained by dividing said spread code when detecting a correlation value in said slot by a correlator; A communication synchronizer characterized in that a dynamic RAM is used as a memory means of the correlator, wherein the dynamic RAM is stored in the means, and all small unit correlation values are added and output. 6. A mobile terminal device using a dynamic RAM as a memory means in a mobile phone that performs at least voice communication via a wireless line. 7. The portable terminal device according to claim 6, wherein a data access occurs in the dynamic RAM within a refresh cycle.