JP2000083010A - Rake receiver and speed detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rake receiver capable of suppressing a drop call at the time of handover by quickly detecting a signal from a moving destination base station even at the time of high speed moving. SOLUTION: Searchers 2a to 2c inversely diffuse a digital signal from an A/D converter 1 and demodulate it by respectively using the diffusion code of a class indicated from a controlling part 5 and the timing of inverse diffusion and notifies these demodulation results to the controlling part 5. A mobile speed deciding means 5a decides the speed of a mobile communication terminal device in accordance with mobile speed information detected by a speed detection circuit in the searcher 2a. A searcher controlling means 5b performs ON/ OFF control of the searchers 2a to 2c in accordance with the speed decided by the means 5a. A forgetting coefficient controlling means 5c switches and controls the value of a forgetting coefficient αin accordance with a speed decided by the means 5a and enhances sensitivity to signal intensity from the base station of a moving destination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CDMA (Code
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rake receiver and a speed detection circuit used for a mobile communication terminal of a Division Multiple Access (Division Multiple Access) system.

[0002]

2. Description of the Related Art Recently, a CDMA (Code Division Multipl.
e Access) method has been adopted. This communication system enables multipath separation by spreading information symbols at a chip rate and widening the bandwidth of a transmission signal.

In a system conforming to the US TIA standard (IS-95A), information symbols (19.2 KHz) are spread at a chip rate (1.2288 MHz) (spreading rate 64), so that one or more chips are separated. Multipath can be separated.

On the other hand, FDMA (Frequency Divi
sion multiple access (TDMA) or time division access (TDMA)
In a system in which communication is performed using a narrow band transmission signal such as the n Multiple Access system, as shown in FIG. 12A, so-called flat fading occurs in which received power drops sharply due to multipath fading that fluctuates with time. .

On the other hand, in the CDMA system, even if multipath fading occurs due to the widening of the transmission signal, only a part of the spectrum is lost as shown in FIG. The received power does not drop, and even if a part of the received signal is lost, path diversity that actively uses the separated multipath by rake reception is performed, so that good reception characteristics can be obtained.

FIG. 13 shows a rake receiver of a conventional mobile communication terminal device that performs such rake reception. The RF signal transmitted from the base station is received by an antenna (not shown), is converted into a digital signal by an A / D converter (A / D) 1, and is then input to the search unit 20 and the demodulation unit 30. You.

The search section 20 includes searchers 20a to 20c
Consists of The searchers 20a to 20c include a control unit 5 described later.
The digital signal from the A / D converter 1 is despread and demodulated using the spreading code of the type indicated from 0 and the despreading timing, and the level of the demodulation result is detected to control the control unit 50. Notify. Note that the types of spreading codes specified by the control unit 50 are a spreading code assigned to each base station and a spreading code assigned to the own station.

[0008] The demodulation unit 30 includes fingers 30a to 30d. The fingers 30a to 30d are connected to a control unit 50 described later.
A / D using the spreading code and timing indicated by
The digital signal from converter 1 is despread and demodulated. Each of the fingers 30a to 30d detects the level of the demodulated signal and notifies the control unit 50 of the detected level.

The synthesizing circuit 4 synthesizes the signals demodulated by the fingers 30a to 30d, and outputs the synthesized result to a decoding circuit (not shown) at the subsequent stage. The control unit 50 includes the searchers 20a to 20c and the fingers 30a to 30d as described above.
To the searcher 20a to 20c and the finger 3
The level of the demodulated signal notified from 0a to 30d is monitored.

Then, the control unit 50 controls the searchers 20a to 20a.
The level notified from 20c is fingers 30a to 30d
If the level is larger than the notified level, the spreading code and the despreading timing used in the searchers 20a to 20c that have detected the higher level are assigned to the fingers 30a to 30d that have been notified of the lower level.

With such a configuration, the rake receiver has:
Among the multipath signals, one having a high reception level is assigned to the fingers 30a to 30d, and a plurality of fingers 30a to 30d are assigned.
30d realizes path diversity to be received respectively.

In addition, the rake receiver realizes cell diversity called soft handover separately from the above-mentioned path diversity. This cell diversity is
When the mobile communication terminal device M moves from the cell of the base station A to the cell of the base station B and performs handover, the mobile station M performs communication via the base station A used before the handover, and Are sequentially assigned to the searchers 20a to 20c, and the level notified from each searcher 20a to 20c is monitored to detect the base station B of the movement destination, and the base station of the movement destination is detected. Report to base station A that the station is base station B.

On the other hand, the base station A communicates with the base station B via a network connecting the base stations so that the mobile communication terminal M can communicate with the base station B via the base station B. Notify the assigned spreading code. On the other hand, the base station B uses the spreading code of the mobile communication terminal M notified from the base station A, and
Start transmitting the signal addressed to it.

When mobile communication terminal apparatus M is completely moved to the cell of base station B by performing rake reception while combining and receiving signals from both base station A and base station B, the mobile communication terminal apparatus M The communication by the path diversity is performed again through the station B. Such cell diversity makes it possible to continue communication without momentary interruption even if handover is performed.

[0015] However, in the conventional rake receiver having the above-described configuration, if a cell moves between cells by high-speed movement, a drop call may occur. FIG.
It shows a change in signal strength from the base station B in the mobile communication terminal apparatus M moving toward the base station B, and shows a time of low-speed movement and a time of high-speed movement, respectively.

As shown in FIG. 1, the signal strength from the base station B increases more rapidly during high-speed movement than during low-speed movement, but approaches the base station B more quickly during high-speed movement than during low-speed movement. Therefore, the number of base stations that can be verified is smaller than when moving at low speed.

For this reason, depending on the monitoring order of the base station (the allocation order of the spreading code to be verified), the verification using the spreading code of the base station B is not performed, so that the mobile station moves at a higher speed than at a lower speed. 15, the detection of the base station B is delayed on average.

If the detection of the base station B is delayed and approaches the base station B as described above, a signal addressed to the mobile communication terminal M is not yet transmitted from the base station B. The signal becomes an interference wave, and a drop call occurs.

[0019]

In the conventional rake receiver, when handover is required due to movement between cells during high-speed movement, detection of a signal from a destination base station is delayed, causing a drop call. There is a problem that there is a risk of occurrence.

The present invention has been made in order to solve the above-mentioned problem. A rake capable of quickly detecting a signal from a communication partner station when moving at high speed and suppressing a drop call at the time of handover. It is intended to provide a receiver.

Another object of the present invention is to provide a rake receiver and a speed detecting circuit capable of detecting the moving speed of the own device. Another object of the present invention is to provide a rake receiver with reduced power consumption. Still another object of the present invention is to provide a rake receiver capable of visually notifying a user of a moving speed of the own device.

[0022]

In order to achieve the above object, a rake receiver according to the present invention comprises a digital conversion means for converting a received signal into a digital signal, and various spreading means assigned to each communication partner station. Using codes in sequence,
A plurality of despreading means for despreading the received signal converted into a digital signal by the digital conversion means at various timings; and monitoring the strength of the received signal despread by the plurality of despreading means, and Path detecting means for detecting a spreading code suitable for despreading and timing of despreading; a plurality of demodulating means for despreading and demodulating a received signal using the spreading code and timing detected by the path detecting means; A moving speed detecting means for detecting a moving speed of its own device, and a moving speed detected by the moving speed detecting means. As the speed becomes faster, the path detection means is provided with a detection sensitivity control means for increasing the detection sensitivity to the intensity of the despread received signal.

The rake receiver having the above configuration detects the moving speed of its own device, and as the detected moving speed increases, the detection sensitivity of the path detecting means with respect to the strength of the despread received signal is increased. ing.

Therefore, according to the rake receiver having the above-described configuration, when the own device is moving at a high speed, the detection sensitivity of the received signal can be increased. It can be detected and speeded up. For this reason, even when handover is required due to, for example, high-speed movement between cells, signal detection from a destination base station is performed earlier than usual, and a drop call due to signal detection delay is suppressed. be able to.

In order to achieve the above object, a rake receiver according to the present invention uses digital conversion means for converting a received signal into a digital signal, and various spread codes assigned to each communication partner station in order. A plurality of despreading means for despreading the received signal converted into a digital signal by the digital conversion means at various timings, and monitoring the strength of the received signal despread by the plurality of despreading means,
A path detecting means for detecting a spreading code suitable for despreading of the received signal and a timing of despreading; and a plurality of demodulating means for despreading and demodulating the received signal using the spreading code and the timing detected by the path detecting means. A rake receiver comprising a combining means for combining a plurality of received signals demodulated by these demodulating means, a moving speed detecting means for detecting a moving speed of the own apparatus, and a moving speed detecting means An operation control means for increasing the number of operations of the plurality of despreading means as the moving speed becomes higher is provided.

The rake receiver having the above configuration detects the moving speed of its own device, and increases the number of operations of the despreading means as the detected moving speed increases. Therefore, according to the rake receiver having the above configuration, when the path does not fluctuate so much as when stopped or when moving at a low speed, it is necessary to operate unnecessarily many despreading means. No, and when the path fluctuations are active, such as when moving at high speed, to operate many despreading means, while responding to path fluctuations according to the moving speed,
Power consumption can be reduced.

Further, the rake receiver according to the present invention comprises:
Digital conversion means for sampling a received signal and converting it into a digital signal; and a digital signal for despreading by a plurality of despreading means, among the digital signal samples converted by the conversion means, Extracting means for extracting a plurality of continuous samples according to an instruction of a control signal, and an extracting position for variably controlling the samples extracted by the extracting means through a control signal in accordance with the intensity of the plurality of samples extracted by the extracting means. A moving speed detecting means for detecting a moving speed of the own device based on a control signal output from the extraction position controlling means.

In the rake receiver having the above-mentioned structure, the digital conversion means performs the sampling at, for example, 8 bits per chip, and the extraction means generates a digital signal for despreading by a plurality of despreading means. For example, a continuous 3-bit sample is extracted from the 8 bits, and the extraction position control means controls the extraction position of the sample in the extraction means according to the intensity of the 3-bit sample. Since the strength of the extracted three bits changes as the moving speed increases, when the moving speed increases, the frequency of control of the extraction means through the control signal of the extraction position control means increases. The present invention pays attention to this point, and the moving speed detecting means monitors the frequency to detect the moving speed.

Therefore, the rake receiver having the above configuration can detect the moving speed without newly providing a sensor such as an accelerometer or a gyro for detecting the moving speed.

In the rake receiver according to the present invention, the path detecting means accumulatively adds the intensity of the received signal despread by the despreading means.
An arithmetic means for adding the intensity cumulatively added in the past and the intensity of the received signal newly despread by the despreading means at a ratio corresponding to the variable value α; Detecting means for detecting the spread code used at this time and the timing of despreading as being suitable for despreading of the received signal, wherein the detection sensitivity control means detects the moving speed detected by the moving speed detecting means. As the speed becomes higher, the calculating means variably controls the variable value α so as to increase the ratio of the intensity of the received signal newly despread by the despreading means and perform cumulative addition, thereby increasing the detection sensitivity. Features.

Therefore, according to the rake receiver having the above configuration, when the moving speed is increased, the arithmetic means increases the ratio of the intensity of the received signal newly despread by the despreading means and performs cumulative addition. The result of the accumulation operation by the operation means reflects the intensity of the received signal newly despread by the despreading means. Therefore, when the strength of the received signal increases during high-speed movement, the result of the accumulative calculation by the calculating means increases more rapidly than at low-speed movement and exceeds the reference value. Signals from such devices can be quickly detected.

Further, in the rake receiver according to the present invention, the path detecting means includes a calculating means for accumulatively adding and averaging the intensity of the received signal despread by the despreading means, and an averaging result of the calculating means. In the case where exceeds the variable reference value, at this time, the spread code used in the despreading means and detection means for detecting the timing of despreading as suitable for the despreading of the received signal, and the detection sensitivity control means The detection sensitivity is increased by decreasing the variable reference value of the detecting means as the moving speed detected by the moving speed detecting means increases.

Therefore, according to the rake receiver having the above configuration, when the moving speed is increased, the threshold value (variable reference value) for detecting a signal from a communication partner is reduced, so that the strength of the received signal is increased when moving at high speed. In such a case, a signal from a destination base station or the like can be detected more quickly than when moving at a low speed.

Further, the rake receiver according to the present invention is characterized in that a speed display means for visually notifying the moving speed detected by the moving speed detecting means is provided. Therefore, according to the rake receiver of the present invention, it is possible to visually inform the user of the moving speed of the own device.

Further, in the speed detecting circuit according to the present invention, the converting means for sampling the received signal and converting it into a digital signal, and in accordance with the instruction of the control signal among the digital signal samples converted by the converting means. Extracting means for extracting a plurality of continuous samples, extracting position control means for variably controlling the samples extracted by the extracting means through a control signal in accordance with the intensity of the plurality of samples extracted by the extracting means, and extracting position. Speed detecting means for detecting a moving speed of the own device based on a control signal output from the control means is provided.

In the speed detection circuit having the above-described structure, the converting means performs sampling at, for example, 8 bits per chip, and the extracting means outputs digital signals for despreading by a plurality of despreading means. For example, a continuous 3-bit sample is taken out, and the extraction position control means controls the sample taking-out position in the extraction means according to the intensity of the 3-bit sample.
As the moving speed increases, the intensity of the extracted three bits changes. Therefore, when the moving speed increases, the frequency of control of the extraction unit through the control signal of the extraction position control unit increases. The present invention pays attention to this point, and the speed detecting means monitors the frequency to detect the moving speed.

Therefore, the speed detecting circuit having the above configuration can detect the moving speed by a method different from a sensor such as an accelerometer or a gyro for detecting the moving speed.

[0038]

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 of a rake receiver of a mobile communication terminal according to an embodiment of the present invention.

The RF signal transmitted from the base station is received by an antenna (not shown), is converted into a baseband signal, is converted into a digital signal by an A / D converter (A / D) 1, and is searched. The signals are input to the unit 2 and the demodulation unit 3, respectively. In addition, the A / D converter 1 is, as shown in FIG.
The baseband signal is sampled into an 8-bit digital signal per chip.

The search unit 2 includes searchers 2a to 2c. The searchers 2a to 2c operate in a control unit 5 described later.
The digital signal from the A / D converter 1 is de-spread and demodulated using the spreading code of the type indicated by the control unit 5 described later and the de-spreading timing. The level of the demodulation result is detected and notified to the control unit 5. The types of spreading codes specified by the control unit 5 are a spreading code assigned to each base station and a spreading code assigned to the own station.

The demodulation unit 3 includes fingers 3a to 3d. Fingers 3a to 3d despread and demodulate the digital signal from A / D converter 1 using a spreading code and despreading timing instructed by control unit 5, which will be described later, and then perform error correction processing. Is applied. Also, fingers 3a to 3a
d detects the level of the demodulated signal and notifies the control unit 5 of the detected level.

In particular, the finger 3a is configured as shown in FIG. The 8-bit digital signal sampled by the A / D converter 1 is first input to the decimator 31. The decimator 31 responds to a position instruction signal from a delay locked loop circuit 35 described later.
The digital signal is decimated, three consecutive bits are selected from the eight bits, and output to the despreading circuit 32 and the delay locked loop circuit 35.

The despreading circuit 32 despreads the digital signal input from the decimator 31 at the timing notified from the control unit 5 using the spread code generated by the code generation circuit 33, 34.

The code generation circuit 33 generates a type of spread code specified by the control unit 5 described later. Error correction circuit 3
4 performs error correction processing on the digital signal despread by the despreading circuit 32 and outputs the processing result to the synthesis circuit 4.

The delay locked loop circuit 35 detects a shift in the decimator position of the decimator 31 and outputs a position instruction signal for correcting this shift to the decimator 31.
Is output to This position instruction signal is also output to the speed detection circuit 36.

First, the delay locked loop circuit 35
Monitors each level of the 3-bit digital signal input from the decimator 31. Then, as shown in FIG. 4 (a), when the level of each bit becomes higher as the bit becomes later, a position indication signal "+1" is output to the decimator 31, and one decimator position is set. Instruct to shift in the slow direction.

The delay locked loop circuit 35
When the level of each bit is large in the middle as shown in FIG.
A position instruction signal "0" is output to instruct not to shift the decimator position.

The delay locked loop circuit 35
As shown in FIG. 4C, when the level of each bit becomes higher as the previous one, a position indication signal “−1” is output to the decimator 31 to set the decimator position to 1 Instruct to move in the fastest direction.

The speed detecting circuit 36 detects the moving speed of the mobile communication terminal device based on the position instruction signal given to the decimator 31 from the delay locked loop circuit 35.

First, before describing the mechanism of speed detection by the speed detection circuit 36, the relationship between the moving speed and the position instruction signal will be described. The radio frequency signal from the base station spread over a wide band as shown in FIG. 5 (a) is partially lost as shown in FIG. 5 (b) due to the effect of fading due to multipath.

When moving at a high speed in this state, the effect of fading due to multipath becomes remarkable and distortion increases. At a low speed, an eye opening as shown in FIG. 6A is obtained. The pilot signal included in one multipath also has a reduced eye opening as shown in FIG. 6B due to the high-speed movement.

When the moving speed is increased and the eye opening is reduced, the decimator position fluctuates greatly. Therefore, by monitoring the position instruction signal, it can be detected that the moving speed has increased.

FIG. 7 shows the structure of the speed detection circuit 36. The position instruction signal input from the delay locked loop circuit 35
1 is input.

The shift register 361 has ten registers 3610 to 3619 connected in series as shown in FIG. 8, and each register stores its own data by a dump clock signal synchronized with the output of the position instruction signal. The position instruction signal to be output is sequentially output to an adjacent register and is output to the parallel / serial conversion circuit 362.

The parallel / serial conversion circuit 362 converts the position instruction signal input from the registers 3610 to 3619 into a serial signal, and outputs the serial signal to the counter 363. The counter 363 counts the number of “+1” and “−1” included in the ten position instruction signals input from the parallel / serial conversion circuit 362, and inputs the count result to the comparison circuits 364 and 365. I do.

The comparison circuit 364 compares the count result with “3”, and when the count result exceeds “3”, “1”.
If the data does not exceed the data, the data “0” is output to the control unit 5.

On the other hand, the comparison circuit 365 compares the count result with “8”, and when it exceeds “8”, outputs “1” data; when it does not exceed “8”, outputs “0” data; Each is output to the control unit 5.

Therefore, when the mobile communication terminal device is almost in a "stop" state, the comparison circuits 364, 365
Output “0” data and are in the “low-speed movement” state, the comparison circuit 364 outputs “1” data,
The comparison circuit 365 outputs “0” data. Then, when the mobile communication terminal device is in a faster “high-speed movement” state, both of the comparison circuits 364 and 365 output “1” data.

Therefore, when both of the comparison circuits 364 and 365 output “0” data, the fluctuation of the decimator position is small, and it can be determined that the mobile communication terminal device is almost in the “stop” state. When the circuit 364 outputs “1” data and the comparison circuit 365 outputs “0” data, it can be determined that the vehicle is in the “low-speed movement” state.

When both of the comparison circuits 364 and 365 output "1" data, the decimator position greatly fluctuates, and the mobile communication terminal apparatus is "high-speed moving".
It can be determined that it is in a state.

As described above, according to the speed detection circuit 36,
Based on the ten position instruction signals, the moving speed of the mobile communication terminal device can be detected in three stages of “stop”, “low speed”, and “high speed”. Comparison circuit 3
The data output from 64 and 365 is output to the control unit 5 as moving speed information.

The combining circuit 4 combines the signals demodulated by the fingers 3a to 3d, and a decoding circuit (not shown) at the subsequent stage.
Output the result of synthesis. The control unit 5 assigns the type of the spread code and the timing of despreading to the searchers 2a to 2c and the fingers 3a to 3d as described above, and demodulates the signals by the searchers 2a to 2c and the fingers 3a to 3d. Monitor the signal level.

Then, according to the monitoring result, the path diversity is performed by switching and controlling the spread signals assigned to the fingers 3a to 3d and the despreading timing so as to receive a path having a high reception level.

When the level notified from the fingers 3a to 3d is lower than a preset level, the control unit 5 determines the spreading code and the despreading timing of the path (finger) that provides the highest level. The cell diversity processing is started by allocating to the finger 3a.

In this cell diversity processing, the control unit 5
The base station adjacent to the base station (hereinafter, referred to as base station A) receiving the finger 3a to the searchers 2a to 2c is sequentially assigned with its spreading code as a destination candidate base station.

Then, the levels sequentially notified from the searchers 2a to 2c are respectively substituted into the following expression X (n) and cumulatively added to convert them into the determined levels Y (n). Note that Y (n-1) in the following equation (1) is Y
This is the calculated value immediately before (n). Α is a forgetting coefficient, which is controlled by a forgetting coefficient control unit 5c, which will be described later.

[0067]

(Equation 1)

Then, the determined level Y (n) is averaged, and it is monitored whether or not the averaged result exceeds a preset level (hereinafter, referred to as a handover threshold). When the result of averaging the determined level Y (n) exceeds the handover threshold, the destination code is calculated based on the spread code assigned to the searchers 2a to 2c on which the determined level Y (n) is calculated. Base station (hereinafter, referred to as base station B)
Is detected.

Then, the spreading code and the despreading timing of the base station B are assigned to the fingers 3b to 3d having a lower reception level, and the base station to be received is switched from A to B.

When detecting the base station B, the control unit 5 controls a transmission system (not shown) to notify the base station A of the base station B as a destination base station. The base station A having received the notification instructs the base station B to transmit a signal addressed to the mobile communication terminal.

By the way, the control unit 5 includes a moving speed determination unit 5a and a searcher control unit 5b as new control functions.
And forgetting factor control means 5c. The moving speed determining means 5a determines the speed of the mobile communication terminal device in three stages of “stop”, “low speed moving”, and “high speed moving” in accordance with the moving speed information notified from the speed detecting circuit 36, as described above. Is determined.

The searcher control means 5b controls the searchers 2a to 2a in accordance with the speed determined by the moving speed determination means 5a.
ON / OFF control of c. In this control, all three searchers 2a to 2c are operated during "high-speed movement", and two searchers 2a and 2b are operated during "low-speed movement". If it is determined that the state is "stop", only the searcher 2a is operated.

The forgetting factor control means 5c switches and controls the value of the forgetting factor α according to the speed determined by the moving speed determining means 5a. In this control, the value of the forgetting factor α is set to “0.8” during “high-speed movement”, and is set to “0.5” during “low-speed movement”. If it is determined that the state is "stop", the value of the forgetting factor α is set to "0.3".

The display unit 6 has an LC capable of displaying various characters.
D (Liquid Crystal Display), etc., which can display the identification number of the destination, the setting state of the own device, etc., and "stop" the speed of the mobile communication terminal device determined by the moving speed determining means 5a. ”,“ Low-speed movement ”,“ High-speed movement ”
Is displayed in three stages.

Next, the cell diversity processing operation at the time of handover in the rake receiver having the above configuration will be described below. FIG. 9 is a flowchart thereof. Finger 3
When the level notified from a to 3d becomes lower than the preset level, the control unit 5 starts the cell diversity processing shown in FIG.

First, in step 9a, the fingers 3a to 3a
Among the levels notified from 3d, the spreading code of the path (finger) and the despreading timing at which the highest level is obtained are assigned to the finger 3a. As a result, the finger 3a receives the path of the highest level.

Then, in step 9b, the finger 3a
The base station adjacent to the base station A which is being received by the base station A is set as a candidate base station of the movement destination, and the spread codes thereof are sequentially searcheder 2a to 2
Assign to c.

However, at this time, the operations of the searchers 2a to 2c are controlled by the searcher control means 5b according to the speed determined by the moving speed determination means 5a. For this reason,
The spreading code is assigned only to the searcher in the operating state, and FIG. 10 shows the assignment order of each state of “stop”, “low-speed movement”, and “high-speed movement”.

In the example of FIG. 10, it is assumed that there are eight base stations N1 to N8 adjacent to the base station A, and the search time per base station is set to 10 [ms]. In this case, when the moving speed determination means 5a determines that the state is "stop", only the searcher 2a operates, and therefore, FIG.
As shown in FIG. 0 (a), the currently used base station A and the other base stations N1 to N8 are alternately searched, so that it takes 160 [m] to go around all the searched base stations.
s]

When the moving speed judging means 5a judges that it is in the "low speed moving" state, the searchers 2a and 2b operate, and as shown in FIG. Since the base station A currently being used is searched, and the other searcher 2b searches for the other base stations N1 to N8, it takes 80 [ms] to go around all the base stations to be searched.

If the moving speed judging means 5a judges that the state is "high speed moving", the searchers 2a, 2b, 2
Since c operates, as shown in FIG. 10C, the searcher 2a searches for the base station A currently used, and the searchers 2b and 2c search for the other base stations N1 to N8, respectively. Therefore, it takes 40 [ms] to go around all the base stations to be searched.

Next, in step 9c, the searchers 2a to 2a
The levels notified sequentially from 2c are described in (1) above.
Substituting into X (n) of the equation, the determined level Y
(N).

At this time, the forgetting factor α used in the equation (1) is determined by the forgetting factor controlling means 5c by the moving speed determining means 5a.
Switching control is performed in accordance with the speed determination result. In this control,
As described above, the higher the moving speed, the greater the degree of forgetting (coefficient). Therefore, the reception level detected at a time closer to the present time is reflected on the determined level Y (n).

Then, each searcher 2a to 2
It is monitored whether or not the averaging result of the determined level Y (n) of 2c exceeds the handover threshold, and if there is no exceeding, the process proceeds to step 9b to assign another spreading code to the operating state. This is performed for the searchers 2a to 2c.
On the other hand, if there is a handover exceeding the handover threshold, the process proceeds to step 9d.

In step 9d, the base station B is detected from the spread codes assigned to the searchers 2a to 2c corresponding to the averaging result of the determined level Y (n) exceeding the handover threshold. Then, the spreading code of the base station B and the despreading timing are assigned to the fingers 3b to 3d having the lower reception level.

In step 9e, the transmission system is controlled to notify base station A of B as a destination base station. Next, in step 9f, it is verified whether or not the fingers 3a to 3d all use the spreading code of the same base station. Here, if they are not all the same, it is determined that the handover has not been completed, and the process proceeds to step 9a to continue the cell diversity processing. On the other hand, when the spreading codes of the same base station are all used, the cell diversity processing ends.

As described above, in the rake receiver having the above configuration, the moving speed is detected from the fluctuation of the decimator position, and as the detected moving speed increases, the forgetting coefficient α is increased, and the base station B To increase the agility with respect to the increase in the intensity of the signal from

For this reason, as shown in FIG. 11, for example, at the same handover threshold during high-speed movement, the forgetting factor α
With respect to the change w0 of the averaging result of the determined level Y (n) calculated when is constant, the rake receiver having the above configuration increases the forgetting coefficient α to obtain the determined level Y (n).
The rising of the change W1 in the averaging result of (n) is earlier by dt.

Therefore, according to the rake receiver having the above-described configuration, the timing of exceeding the handover threshold is advanced at the time of high-speed movement, whereby the detection of the base station B is accelerated, and the drop call at the time of the handover is performed. Can be suppressed.

In the rake receiver having the above configuration, the number of searchers to be operated is increased as the moving speed is increased. Therefore, when the path does not fluctuate so much as when not moving, unnecessary searchers are not operated, and when the path fluctuates actively such as when moving at high speed. Since a large number of searchers operate, power consumption can be reduced while coping with path fluctuations according to the moving speed.

In the rake receiver having the above configuration, A /
When extracting a part of continuous samples from the digital signal sampled by the D converter 1, paying attention to the fact that the position of the sample suitable for the extraction changes with high-speed movement, the change of the position is considered. The moving speed is detected from. Therefore, according to the rake receiver having the above configuration, the moving speed can be detected without newly providing a sensor such as an accelerometer or a gyro. Furthermore, in the rake receiver having the above configuration, the detected moving speed is displayed on the display unit 6, so that the user can be visually notified of the moving speed of the own device.

The present invention is not limited to the above embodiment. For example, in the above embodiment, in order to increase the agility with respect to the increase in the strength of the signal from the base station B, the forgetting coefficient α is increased as the moving speed increases. Alternatively, for example, even if the handover threshold is set lower as the moving speed increases, the agility with respect to the increase in the strength of the signal from the base station B can be increased. It goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0093]

As described above, according to the present invention, the moving speed of the own device is detected, and as the detected moving speed increases, the detection sensitivity of the path detecting means with respect to the intensity of the despread received signal is increased. To increase. Therefore, according to the present invention, when the own device is moving at high speed, the detection sensitivity of the received signal is increased, so that it is possible to quickly detect a signal from a communication partner station during high speed movement, and to perform handover. A rake receiver capable of suppressing a drop call at the time can be provided.

In the present invention, the moving speed of the own device is detected, and as the detected moving speed increases, the number of operations of the despreading means is increased. Therefore, according to the present invention, when the path does not fluctuate so much as when stopped or when moving at a low speed, unnecessary despreading means is not operated unnecessarily, and In the case where the path fluctuation is active such as when moving at a high speed, a large number of despreading means are operated, so that rake reception can reduce power consumption while coping with path fluctuation according to the moving speed. Machine can be provided.

Also, in the present invention, when extracting a continuous part of samples from a sampled digital signal, attention is paid to the fact that the position of a sample suitable for the extraction changes with high-speed movement. The moving speed is detected from the change in the position. Therefore, according to the present invention, it is possible to provide a rake receiver and a speed detection circuit capable of detecting a moving speed without newly providing a sensor such as an accelerometer or a gyro.

Further, according to the present invention, a speed display means for visually notifying the moving speed detected by the moving speed detecting means is newly provided. Can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of a rake receiver of a mobile communication terminal device according to the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a finger 3a of the rake receiver shown in FIG.

FIG. 3 is a diagram for explaining sampling of the A / D converter 1 of the rake receiver shown in FIG. 1;

FIG. 4 is a view for explaining correction of a decimator position by a delay locked loop circuit 35 of the rake receiver shown in FIG. 1;

FIG. 5 is a diagram illustrating a state in which a radio frequency signal from a base station is partially lost due to the influence of multipath fading.

FIG. 6 is a diagram for explaining how the eye opening of a pilot signal is reduced by high-speed movement.

7 is a speed detection circuit 36 of the finger 3a shown in FIG. 2;
FIG. 2 is a circuit block diagram showing the configuration of FIG.

8 is a circuit block diagram showing a configuration of a shift register 361 of the speed detection circuit 36 shown in FIG.

FIG. 9 is a flowchart for explaining a cell diversity processing operation at the time of handover of the rake receiver shown in FIG. 1;

FIG. 10 is a diagram for explaining a searcher base station search order according to the moving speed of the rake receiver shown in FIG. 1;

11 is a diagram for explaining a change in a determined level Y (n) due to a variable forgetting factor α of the rake receiver shown in FIG. 1;

FIG. 12 is a diagram for explaining a difference in the influence of multipath fading between the CDMA system and another communication system.

FIG. 13 is a circuit block diagram showing a configuration of a conventional rake receiver of a mobile communication terminal device.

FIG. 14 is a diagram illustrating a change in signal strength from a destination base station B due to a change in moving speed.

FIG. 15 is a diagram illustrating a difference between a detection position of a destination base station during high-speed movement and low-speed movement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... A / D converter (A / D) 2 ... Search part 2a, 2b, 2c ... Searcher 3 ... Demodulation part 3a, 3b, 3c, 3d ... Finger 31 ... Decimator 32 ... Despreading circuit 33 ... Code generation circuit 34 ... Error correction circuit 35 ... Delay locked loop circuit 36 ... Speed detection circuit 361 ... Shift register 3610-3609 ... Register 362 ... Parallel / serial conversion circuit 363 ... Counter 364,365 ... Comparison circuit 4 ... Synthesis circuit 5 ... Control unit 5a ... Moving speed determination means 5b Searcher control means 5c Forgetting coefficient control means 6 Display unit

Claims (7)

[Claims] 1. A digital conversion means for converting a received signal into a digital signal, and various spread codes assigned to each communication partner station are sequentially used to convert the received signal converted into a digital signal by the digital conversion means into various types. A plurality of de-spreading means for de-spreading at the timing, and monitoring the strength of the received signal de-spread by the plurality of de-spreading means to detect a spreading code suitable for de-spreading of the received signal and de-spreading timing Path detecting means, a plurality of demodulating means for despreading and demodulating the received signal using the spreading code and timing detected by the path detecting means, and a plurality of received signals demodulated by these demodulating means are combined. In a rake receiver including a synthesizing unit, a moving speed detecting unit that detects a moving speed of the own device, and a moving speed detected by the moving speed detecting unit is increased. Thus, a rake receiver characterized by comprising a sensitivity control means for the path detection means, increase the sensitivity to the intensity of the despread received signal. 2. A digital conversion means for converting a received signal into a digital signal, and various spreading codes assigned to each communication partner station are sequentially used to convert the received signal converted into a digital signal by the digital conversion means into various types. A plurality of de-spreading means for de-spreading at the timing, and monitoring the strength of the received signal de-spread by the plurality of de-spreading means to detect a spreading code suitable for de-spreading of the received signal and de-spreading timing. Path detecting means, a plurality of demodulating means for despreading and demodulating the received signal using the spreading code and timing detected by the path detecting means, and a plurality of received signals demodulated by these demodulating means are combined. In a rake receiver including a synthesizing unit, a moving speed detecting unit for detecting a moving speed of the own device, and a moving speed detected by the moving speed detecting unit is increased. Thus, a rake receiver characterized by comprising an operation control means for increasing the number of operation the plurality of despreading means. 3. The digital conversion means, wherein: a conversion means for sampling a received signal and converting it into a digital signal; and a digital signal converted by the conversion means as a digital signal for despreading by the plurality of despreading means. Extracting means for extracting a plurality of continuous samples corresponding to the instruction of the control signal from the digital signal samples, and extracting the plurality of samples through the control signal in accordance with the intensities of the plurality of samples extracted by the extracting means. Extraction position control means for variably controlling a sample to be taken out by the means, wherein the movement speed detection means detects a movement speed of the own device based on a control signal output from the extraction position control means. The rake receiver according to claim 1 or 2, wherein 4. The path detecting means accumulatively adds the intensity of the received signal despread by the despreading means. At the time of the accumulative addition, the intensity of the signal accumulated in the past is newly added to the despreading signal. Calculating means for adding the intensity of the received signal despread by the means at a ratio corresponding to the variable value α, and when the cumulative addition result of the calculating means exceeds a preset reference value, Detecting means for detecting the timing of the spreading code and the despreading as suitable for the despreading of the received signal, wherein the detection sensitivity control means performs the calculation as the moving speed detected by the moving speed detecting means increases. 2. The detection means according to claim 1, wherein said means variably controls said variable value α so as to increase the ratio of the intensity of the received signal newly despread by said despreading means and perform cumulative addition.
Alternatively, the rake receiver according to claim 3. 5. The path detecting means, a calculating means for accumulatively adding and averaging the intensity of the received signal despread by the despreading means, and an averaging result of the calculating means exceeding a variable reference value. In this case, at this time, there is provided a detecting means for detecting the spreading code used by the despreading means and the timing of the despreading as suitable for the despreading of the received signal, wherein the detection sensitivity control means comprises the moving speed detecting means. 4. The rake receiver according to claim 1, wherein the detection sensitivity is increased by decreasing a variable reference value of the detection unit as the moving speed detected by the detection unit increases. 6. The rake receiver according to claim 1, further comprising speed display means for visually informing the moving speed detected by said moving speed detecting means. 7. A converting means for sampling a received signal and converting it into a digital signal, and extracting a plurality of continuous samples according to an instruction of a control signal from samples of the digital signal converted by the converting means. Means, extraction position control means for variably controlling the samples taken by the extraction means through the control signal in accordance with the intensities of the plurality of samples taken out by the extraction means, and output from the extraction position control means. A speed detecting means for detecting a moving speed of the own device based on a control signal.