JP2002204182A - Mobile radio terminal equipment and cell searching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile radio terminal equipment capable of preventing a consumption of a consuming current by preventing frequent handing-off even when the equipment is disposed at a boundary of cells of a plurality of base stations. SOLUTION: A controller 500 monitors a code power of a common pilot signal from a peripheral base station obtained by a first reverse diffusing circuit 100, and acquires the base station suitable for a communication based on the code power acquired by the circuit 100 when a difference of the code powers of a plurality of peripheral base stations is a prescribed range or more. A second reverse diffusing circuit 200 variably sets a frequency of a clock signal for controlling a generating frequency of a code system to obtain the code power, and obtains the base station in which the code power becomes high by the clock signal of as high frequency as possible as the base station suitable for receiving based on the code power obtained by the circuit 300 when a difference of the code powers of the peripheral base stations acquired by the circuit 100 falls within the prescribed range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CDMA (Code
The present invention relates to a mobile radio terminal used in a mobile radio communication system such as a mobile phone system or a mobile phone system adopting a Division Multiple Access (Division Multiple Access) system.

[0002]

2. Description of the Related Art As is well known, in the CDMA system, a baseband signal such as voice or data is transmitted by using a code sequence generated by a high-speed synchronous clock of several tens to several hundreds times the information rate. It spreads, and the result of this spreading is up-converted to radio frequency and transmitted.

On the receiving side, in order to reproduce (despread) a received signal, it is necessary to know in advance the type of code sequence used for spreading on the transmitting side and the reproduction time (despread timing). For this reason, a mobile radio terminal used in a CDMA mobile radio communication system is conventionally provided with a cell search circuit for detecting the type of the code sequence and the reproduction time.

Conventionally, a cell search circuit employing a sliding correlation system or a matched filter system has been known. In a mobile radio terminal adopting these methods, a unique code sequence assigned in advance to each base station is detected, and a cell search circuit receives a common pilot signal from the base station using this code sequence, The code power of the signal is detected.

FIG. 2 shows a basic configuration example of a despreading circuit used in such a cell search circuit. As shown in the figure, the cell search circuit includes a despreading circuit 100 and a cell detection circuit 400 as main components.

The despreading circuit 100 includes a code reproducing means 102 capable of reproducing a code sequence specified at an arbitrary time under the control of a control unit (not shown), a code sequence reproduced here, and a baseband band. Correlation means 101 for detecting instantaneous correlation power with a received signal converted to a digital signal after frequency conversion, and integration means 10 for averaging and outputting the detected instantaneous correlation power for a certain period of time.
And 3.

In the above configuration, since the signal output from the integrating means 103 is the code power of the desired signal at the time designated by the external control, by controlling the code reproducing time of the code reproducing means 102, A sample of the code power for an arbitrary reproduction time is obtained.

In the CDMA system, different code sequences are used between adjacent base stations in order to reduce systematic intersymbol interference. Therefore, the code reproducing means 10
By variably controlling the type of the code sequence to be reproduced in Step 2, the base station to be detected can be changed, and the output of the integrating means 103 is changed by the variable control so that the common pilot signal received from the base station located in the vicinity is obtained. Of the code power.

[0009] Using the code power of the common pilot signal from the peripheral base station thus determined, the cell detection circuit 400 determines a base station suitable for communication, and individually determines the base station through the determined base station. Communication of information was performed.

However, in the conventional cell search circuit, since only the code power is used as a criterion for base station selection, when the mobile communication terminal is located at a cell boundary as shown in FIG.
Common pilot signals from a plurality of base stations are detected at substantially the same level, and it is difficult to select an optimal base station.

[0011] Therefore, in such a case, in the conventional mobile radio terminal, handoff frequently occurs near the boundary of the service area of the base station, causing a problem that extra current consumption is required.

[0012]

In the conventional mobile radio terminal, when located at the cell boundary of a plurality of base stations, the common pilot signals from the plurality of base stations are detected at substantially the same level, and the optimum base station is detected. There is a problem that it becomes difficult to select a station, handoff frequently occurs depending on the situation, and extra current consumption is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is possible to prevent frequent handoffs even when located at a cell boundary of a plurality of base stations, thereby preventing waste of current consumption. It is an object to provide a possible mobile radio terminal and a cell search circuit.

[0014]

To achieve the above object, according to the present invention, there is provided a mobile radio terminal used in a mobile radio communication system for performing radio communication according to a CDMA system. Code generating means capable of selectively generating a code sequence, a correlating means for performing a despreading process on a code-spread received signal using the code sequence generated by the code generating means, and a correlating means. It is configured to variably control the generation speed of the code sequence, and to include a detection control unit that detects a communication partner suitable for wireless communication from a result of the despreading process by the correlation unit and a generation speed corresponding thereto. did.

The present invention according to claim 5 is a CDM.
In a cell search circuit used for a mobile radio terminal performing wireless communication according to the A method, a code generation means capable of selectively generating various code sequences, and a code generation method using the code sequences generated by the code generation means. Correlation means for performing despreading processing on the spread received signal, and variably controlling the generation speed of the code sequence used in the correlation means, and from the result of the despreading processing by the correlation means and the corresponding generation speed, A detection control unit for detecting a communication partner suitable for wireless communication is provided.

In the mobile radio terminal and the cell search circuit having the above configurations, the generation speed of the code sequence used for the despreading process by the correlating means is variably controlled, and the result of the despreading process by the correlating device and the generation speed corresponding thereto To detect a communication partner suitable for wireless communication.

Therefore, according to the mobile radio terminal and the cell search circuit having the above-described configuration, the communication partner detected on the side where the generation speed is high is the communication partner existing in the approaching direction due to the characteristics of the Doppler frequency. Since the communication partner detected on the low-speed side is a communication partner existing in the direction away, the communication partner suitable for wireless communication can be detected from the result of the despreading process by the correlation means and the corresponding generation speed, Thus, even when a plurality of communication partners are located at the same distance, frequent switching of communication partners can be prevented, and waste of current consumption can be prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration related to a cell search circuit of a mobile radio terminal according to an embodiment of the present invention.

As shown in FIG. 1, a mobile radio terminal includes a first despreading circuit 100, a second despreading circuit 200,
The selection circuit 300, the cell detection circuit 401, and the control unit 50
0.

The first despreading circuit 100 is the same as the despreading circuit described in the section of the prior art, and as shown in FIG. 2, a correlating means 101, a code reproducing means 102,
And integrating means 103. Code reproducing means 102
Enables various code sequences to be selectively reproduced at a time designated by the control of the control unit 500 described later.

The correlation means 101 detects the instantaneous correlation power between the code sequence reproduced by the code reproduction means 102 and the received signal which has been frequency-converted into a baseband and converted into a digital signal.

The integrating means 103 averages (integrates) the instantaneous correlation power detected by the correlating means 101 for a certain period of time to obtain an integrated value of the code power of the common pilot signal from the peripheral base station. This integration result is output to a first input terminal of the selection circuit 300 and a control unit 500, which will be described later.

The second despreading circuit 200 obtains the code power of a common pilot signal received from a base station located in the vicinity by using the Doppler frequency, and is configured as shown in FIG.

The A / D converter 201 is a CDM that has been frequency-converted to a sufficiently low band in order to realize digital signal processing.
The A-system reception signal is converted into a digital signal using a clock signal generated by a clock reproduction unit 202 described later.

The clock reproducing section 202 is set by the target frequency setting section 204 using the reference signal generated by the reference signal generator 203 (f0-Δf to f0).
+ Δf) has an AFC function of reproducing a clock signal.

The target frequency setting unit 204 instructs the clock reproducing unit 202 to variably reproduce a clock signal within a range of ± Δf around the reference frequency f0.
The frequency of the clock signal specified here is notified to a cell detection circuit 401 described later.

The code reproducing means 205 reproduces a code sequence of a type unique to a base station located in the vicinity at an arbitrary timing synchronized with the clock signal in response to an instruction from the control section 500.

The correlating means 206 multiplies the code sequence reproduced by the code reproducing means 205 by the digital signal output from the A / D converter 201, and multiplies the signal received from the peripheral base station by the code sequence. Is calculated.

The integration means 207 averages (integrates) the instantaneous correlation power obtained by the correlation means 206 for a predetermined time,
An integrated value of the code power of the common pilot signal from the peripheral base station is obtained. This output is supplied to a selection circuit 300 described later.
Is output to the second input terminal.

The reference frequency f0 is a frequency of a clock signal suitable for receiving a common pilot signal from a base station while the mobile radio terminal is stationary. Therefore, when the reference frequency f0 is set in the clock recovery unit 202, the second despreading circuit 200 outputs the same integration result of the instantaneous correlation power as that of the first despreading circuit 100.

The selection circuit 300 has a first input terminal and a second input terminal.
The control unit 500 includes an input terminal and an output terminal
, One of the first input terminal and the second input terminal is selectively connected to the output terminal.

The result of the integration of the instantaneous correlation power obtained by the first despreading circuit 100 is input to a first input terminal, while the second despreading circuit is input to a second input terminal. 20
The integration result of the instantaneous correlation power obtained at 0 is input.

The cell detection circuit 401 calculates the integration result of the instantaneous correlation power obtained by the first despreading circuit 100 or the second integration result.
The integration result of the instantaneous correlation power obtained by the despreading circuit 200 is selectively input through the selection circuit 300, and the control unit 500 notifies which integration result is input.

When the integration result of the instantaneous correlation power obtained by the first despreading circuit 100 is input, the cell detection circuit 401 bases on the base station ( Cell).

When the integration result of the instantaneous correlation power obtained by the second despreading circuit 200 is input, the cell detection circuit 401 is notified of the integration result and the target frequency setting unit 204. On the basis of the frequency of the clock signal, a base station whose code power is high with a clock signal of the highest possible frequency is determined as a base station suitable for reception.

The control section 500 controls the respective sections of the mobile radio terminal in a centralized manner. The control section 500 controls the first despreading circuit 100 and the second despreading circuit 200 to generate code sequences at the timings of generation and generation. It performs general control related to communication, such as designating the type of code sequence to be performed.

Further, the control section 500 includes the first despreading circuit 1
Based on the integration result of the code power of the common pilot signal from the peripheral base station obtained at 00, switching control is performed to the selection circuit 300.

Under this control, the control unit 500 compares the above integration results of a plurality of peripheral base stations, and if the difference is equal to or larger than a predetermined range, connects the first input terminal and the output terminal of the selection circuit 300 to each other. Then, the integration result of the instantaneous correlation power obtained by the first despreading circuit 100 is input to the cell detection circuit 401.

On the other hand, if the difference is within the predetermined range, the control section 500 connects the second input terminal and the output terminal of the selection circuit 300 and outputs the instantaneous value obtained by the second despreading circuit 200. Control is performed so that the integration result of the correlation power is input to the cell detection circuit 401.

In accordance with the switching control, the control unit 500 instructs the cell detection circuit 401 to integrate the instantaneous correlation power obtained by the first despreading circuit 100 with the second despreading circuit. At 200, it is notified which of the integration results of the instantaneous correlation power has been input.

Next, a cell search operation of the mobile radio terminal having the above configuration will be described. First, as shown in FIG. 4, a case where the mobile radio terminal is outside the cell formed by other peripheral base stations B and C, such as being located at a point P0 in the cell of one base station A will be described. .

In this case, the integrated value of the instantaneous correlation power of the common pilot signal from the base station A and the other base stations B and C
It is found from the integration result that the code power of the common pilot signal obtained by the first despreading circuit 100 is different from the integrated value of the instantaneous correlation power of the common pilot signal from Therefore, the control unit 500 controls the selection circuit 300 to perform switching control so that the integration result of the instantaneous correlation power obtained by the first despreading circuit 100 is input to the cell detection circuit 401.

By this switching control, the cell detection circuit 40
Reference numeral 1 denotes an input of an integration result of the instantaneous correlation power obtained by the first despreading circuit 100, and a base station A suitable for communication is obtained based on the integration result.

Next, as shown in FIG.
A case will be described in which two base stations A, B, and C move at a point P1, which is a boundary between cells formed respectively.

In this case, the first despreading circuit 100 determines that the difference between the integrated values of the instantaneous correlation powers of the common pilot signals from the base stations A, B, and C falls within the above-mentioned predetermined range. In order to determine the code power of the common pilot signal from the integration result, the control unit 500 controls the selection circuit 300 to calculate the integration result of the instantaneous correlation power obtained by the second despreading circuit 200 in the cell detection circuit. Switching control is performed so as to input to 401.

At this time, in the second despreading circuit 200, the clock reproducing unit 202
The reproduction is performed by varying the frequency of the clock signal within the range of ± Δf around the reference frequency f0.

By such a frequency variable control of the clock signal, the base stations A, B,
The result of integrating the code power of the C common pilot signal is shown in FIG.
It is as shown in

That is, when the mobile radio terminal is moving at the point P as shown in FIG. 5, the base station A which is going to get away can obtain high code power on the lower frequency side than the reference frequency f0. On the other hand, the base station C whose distance changes in the direction of getting closer can obtain higher code power on the higher frequency side than the reference frequency f0. Further, the base station B whose change in distance is smaller than that of the base stations A and C exhibits high characteristics at a frequency between these peak frequencies.

Such a characteristic is obtained when the second despreading circuit 200
Is obtained from the integration result of the instantaneous correlation power obtained in (1), the cell detection circuit 401 finds the base station C having the higher code power on the higher frequency side as possible as a base station suitable for reception. Here, when the base station C does not exist, the base station B whose code power is higher on the higher frequency side than the base station A is determined as a base station suitable for reception.

As described above, the mobile radio terminal having the above configuration monitors the integration result of the code power of the common pilot signal from the peripheral base station obtained by the first despreading circuit 100, and If the difference between the integration results of the base stations is equal to or greater than a predetermined range, the first despreading circuit 100
A base station suitable for communication is obtained based on the integration result of the instantaneous correlation power obtained in.

Further, the second despreading circuit 200 varies the frequency of the clock signal for controlling the generation frequency of the code sequence, and obtains the integration result of the code power of the common pilot signal from the peripheral base station. If the difference of the integration result between the neighboring base stations obtained by the first despreading circuit 100 is within a predetermined range, the difference is as high as possible based on the integration result obtained by the second despreading circuit 200. A base station whose code power is increased by a clock signal of a frequency is determined as a base station suitable for reception.

This is because, due to the characteristics of the Doppler frequency, the base station detected on the side where the code sequence generation speed is high is a base station existing in the approaching direction, and is detected on the side where the code sequence generation speed is low. Are based on the fact that the base station is a base station existing in a direction away from the base station.

That is, if the difference between the integration results of the code powers of the common pilot signals transmitted from a plurality of peripheral base stations is equal to or larger than a predetermined range, a base station suitable for communication is obtained in the same manner as in the prior art. If the difference between the integration results is within a predetermined range, a base station that tends to approach is determined as a base station suitable for reception based on the integration result obtained by the second despreading circuit 200.

Therefore, according to the mobile radio terminal having the above configuration, the mobile radio terminal is located at a boundary between cells of a plurality of base stations.
Even if there are multiple base stations that can communicate, even if they are as far from any base station as possible, it is possible to find a base station that tends to approach as a base station suitable for reception. Therefore, it is possible to prevent frequent handoffs and prevent waste of current consumption.

The present invention is not limited to the above embodiment. In the above embodiment, the first despreading circuit 100 and the second despreading circuit 200 are operated in accordance with the difference between the integration results of the code powers of the common pilot signals from the peripheral base stations.
Is selectively used, but the present invention is not limited to this.

For example, as shown in FIG. 7, a speed detecting circuit 60 for detecting based on the fading pitch of the received signal.
0 is provided, and if the detected moving speed is less than a predetermined value, the integration result of the first despreading circuit 100 is used. As in the case of using the spreading circuit 200, the control unit 500
0 may be switched and controlled. This takes into account the fact that handoffs are likely to occur frequently during high-speed movement.

Further, in the above-described embodiment, the first power is determined according to the difference between the integration results of the code powers of the common pilot signals from the peripheral base stations, or according to the moving speed as described above.
Although the despreading circuit 100 and the second despreading circuit 200 are selectively used, the present invention is not limited to this.

That is, for example, the second despreading circuit 200
When the difference between the integration results of the code powers of the common pilot signals from the peripheral base stations is large or when the moving speed is less than a predetermined value, the clock recovery unit 202 is controlled by the target frequency setting unit 204. A clock signal is generated at the reference frequency f0.

On the other hand, when the difference between the integration results is small,
When the moving speed is equal to or higher than the predetermined value, the clock reproduction unit 202 generates the clock signal by changing the clock signal in the range of f0−Δf to f0 + Δf under the control of the target frequency setting unit 204. Even with such a configuration, a similar effect can be expected.

Further, in the above-described embodiment, the frequency range of the clock signal generated by the clock reproducing unit 202 is f0−Δf to f0 + Δf centered on the reference frequency f0, but is not limited to this. Absent. It goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0061]

As described above, according to the present invention, the generation speed of the code sequence used for the despreading process by the correlating means is variably controlled, and the result of the despreading process by the correlating means and the generation speed corresponding thereto are obtained. To detect a communication partner suitable for wireless communication.

Therefore, according to the present invention, due to the characteristics of the Doppler frequency, the communication partner detected on the side with the higher generation speed is the communication partner existing in the approaching direction, and is detected on the side with the lower generation speed. Since the communication partner is a communication partner existing in the direction away, the communication partner suitable for wireless communication can be detected from the result of the despreading process by the correlation means and the corresponding generation speed, whereby multiple communication partners are the same. It is possible to provide a mobile radio terminal and a cell search circuit that can prevent frequent switching of communication partners even when located at a short distance, and can prevent waste of current consumption.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of an embodiment of a cell search circuit of a mobile radio terminal according to the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a first despreading circuit of the cell search circuit shown in FIG.

FIG. 3 is a circuit block diagram showing a configuration of a second despreading circuit of the cell search circuit shown in FIG.

FIG. 4 is a diagram illustrating an operation of the cell search circuit shown in FIG. 1;

FIG. 5 is a diagram for explaining the operation of the cell search circuit shown in FIG. 1;

FIG. 6 is a diagram for explaining an operation when performing a cell search using the second despreading circuit shown in FIG. 3;

FIG. 7 is a circuit block diagram showing a configuration of a modification of the cell search circuit of the mobile radio terminal according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 first despreading circuit 101 correlation means 102 code reproducing means 103 integrating means 200 second despreading circuit 201 A / D converter 202 clock reproducing section 203 reference signal generator 204 target Frequency setting unit 205 Code reproducing unit 206 Correlating unit 207 Integrating unit 300 Selection circuit 401 Cell detection circuit 500 Control unit 600 Speed detection circuit

Claims (8)

[Claims] 1. A CDMA (Code Division Multiple Acc)
ess) In a mobile radio terminal used in a mobile radio communication system that performs radio communication by a method, a code generation means capable of selectively generating various code sequences, and a code sequence generated by the code generation means are used. A correlation means for performing a despreading process on a code-spread received signal; and variably controlling a generation speed of a code sequence used in the correlation means, and a result of the despreading process by the correlation means and a corresponding A mobile radio terminal comprising: a detection control unit that detects a communication partner suitable for the wireless communication from the generation speed. 2. The detection control means detects a plurality of communication partners capable of the wireless communication based on a result of the despreading process performed by the correlation means using a code sequence generated at a preset speed. If the difference between the detected communication qualities with a plurality of communication partners is less than a preset value, variably control the generation speed of the code sequence used by the correlator, and the result of the despreading process by the correlator. The mobile radio terminal according to claim 1, wherein a communication partner suitable for the radio communication is detected based on the generation speed corresponding thereto. 3. A moving speed detecting means for detecting a moving speed, wherein said detecting control means is used by said correlating means when the moving speed detected by said moving speed detecting means is equal to or higher than a preset value. 2. The communication system according to claim 1, further comprising: variably controlling a generation speed of the code sequence, and detecting a communication partner suitable for the wireless communication from a result of the despreading process by the correlation unit and the generation speed corresponding thereto. The mobile radio terminal according to the above. 4. The detection control means, when variably controlling the generation speed of a code sequence used by the correlation means, detects a plurality of communication partners capable of the wireless communication from the result of the despreading processing by the correlation means. 2. The communication method according to claim 1, wherein, among the plurality of detected communication partners, a communication partner having the highest generation speed used in the detection is detected as a communication partner suitable for the wireless communication. To claim 3
A mobile wireless terminal according to any one of the above. 5. A CDMA (Code Division Multiple Acc)
ess) In a cell search circuit used for a mobile wireless terminal that performs wireless communication according to the method, a code generation unit capable of selectively generating various code sequences, and a code sequence generated by the code generation unit are used. A correlating means for performing despreading processing on the code-spread received signal; and variably controlling a generation speed of a code sequence used in the correlating means, the result of the despreading processing by the correlating means and the corresponding A cell search circuit, comprising: detection control means for detecting a communication partner suitable for the wireless communication from a generation speed. 6. The detection control means detects a plurality of communication partners capable of the wireless communication based on a result of the despreading process performed by the correlation means using a code sequence generated at a preset speed. If the difference between the detected communication qualities with a plurality of communication partners is less than a preset value, variably control the generation speed of the code sequence used by the correlator, and the result of the despreading process by the correlator. 6. The cell search circuit according to claim 5, wherein a communication partner suitable for the wireless communication is detected from the generation speed corresponding thereto. 7. A moving speed detecting means for detecting a moving speed, wherein said detecting control means is used by said correlating means when the moving speed detected by said moving speed detecting means is equal to or higher than a preset value. 6. The method according to claim 5, wherein a code partner generation speed is variably controlled, and a communication partner suitable for the wireless communication is detected from a result of the despreading process by the correlation unit and the corresponding generation speed. The cell search circuit according to the above. 8. The detection control means, when variably controlling the generation rate of a code sequence used by the correlation means, detects a plurality of communication partners capable of the wireless communication from the result of the despreading processing by the correlation means. 6. A communication partner whose generation speed used at the time of the detection is the highest among the plurality of detected communication partners is detected as a communication partner suitable for the wireless communication. To claim 7
The cell search circuit according to any one of the above.