JP2000307512A - Closed loop transmission power control device for mobile radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a closed loop transmission power control device for a mobile radio communication system where the effect of an error of transmission power caused singly especially hardly takes place and the transmission power is accurately controlled within a prescribed period. SOLUTION: In the closed loop transmission power control device of the mobile radio communication system that conducts radio communication between a base station and a mobile station, where a base station generates transmission power control information from a received signal to control transmission power of a mobile station, transmits the information and the mobile station controls the transmission power on the basis of the received transmission power control information, a digital filter 22 of the mobile station receives the transmission control information to control the transmission power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile radio communication system for performing radio communication between a base station and a plurality of mobile stations, and more particularly to an improvement of a closed loop transmission power control device for controlling the transmission power of the mobile station. About.

[0002]

2. Description of the Related Art As is well known, for example, CDMA (Code D
In a mobile radio communication system typified by an ivision multiple access (ivision) multiple access system, if the transmission power of a mobile station is too low, a communication line is disconnected. In this case, an interference wave is generated in the communication path of the mobile station, and the inconvenience of reducing the capacity of the entire system occurs.

For this reason, in this type of mobile radio communication system, conventionally, when a base station receives a signal transmitted from each mobile station, its reception level is measured individually and the transmission level of each mobile station is measured. By determining whether to increase or decrease the power, by transmitting the transmission power control information generated based on the determination result to each mobile station, to control the transmission power, to perform closed loop transmission power control I have to.

FIG. 8 shows such a conventional closed-loop transmission power control device. First, on the mobile station side, transmission data is supplied to a digital modulation circuit 11 and subjected to modulation processing.
And is amplified to a predetermined transmission power and transmitted.

On the other hand, the base station receives a signal transmitted from a mobile station and demodulates the signal by a digital demodulation circuit 13 to obtain received data. The received data output from the digital demodulation circuit 13 is supplied to an Eb / Io measurement circuit 14 where the signal level is measured.

The measurement result of the Eb / Io measuring circuit 14 is
It is supplied to the power control data generation circuit 15 to determine whether to increase or decrease the transmission power of the mobile station. This power control data generation circuit 15 generates transmission power control information based on the determination result. The transmission power control information is 1-bit information. "1" indicates that the transmission power of the mobile station is increased by 1 dB, and "0" indicates that the transmission power of the mobile station is decreased by 1 dB.

The transmission power control information output from the power control data generation circuit 15 is inserted at regular intervals into a transmission data sequence transmitted on the downlink by an addition circuit 16 and then modulated by a digital modulation circuit 17. Processed and sent. Note that the transmission data is provided with an error correction code so that the mobile station can perform an error correction process. However, the transmission power control information contains error correction information in order for the mobile station to perform real-time transmission power control. Correction processing is not performed.

[0008] The mobile station receives the signal transmitted from the base station and performs demodulation processing by the digital demodulation circuit 18 to obtain received data. The received data output from the digital demodulation circuit 18 is supplied to a power control bit extraction circuit 19, where transmission power control information is extracted. The power control bit extraction circuit 19 extracts the transmission power control information by synchronizing the frame of the received data because information indicating the bit position where the transmission power control information exists and the interval between the bits is set in advance. be able to.

The transmission power control information output from the power control bit extraction circuit 19 is supplied to a threshold value judgment circuit 20. This threshold value judgment circuit 20 determines whether or not the state of the communication path is good based on the signal level of the reception data output from the digital demodulation circuit 18 measured by the Eb / Io measurement circuit 21. Only when it is determined to be good, transmission power control information is given to the transmission amplifier circuit 11 to control the gain.

[0010] That is, when the state of the communication path is good, the probability that a bit error occurs in the transmission power control information is low. Is no problem (O
N). However, since error correction processing is not performed on the transmission power control information as described above, it is highly possible that a bit error has occurred in the received transmission power control information when the state of the communication path is not good. Therefore, the transmission power control information is not supplied to the transmission amplification circuit 11 (the control is turned off) so that erroneous transmission power control is not performed.

The received signal level used by the threshold value judgment circuit 20 to judge the quality of the communication channel is determined by the average Eb of a plurality of symbol sections in the signal sequence (symbol sequence) received by the mobile station. / Io.

[0012]

The above-described closed-loop transmission power control device is usually used to cope with sudden fluctuations in power such as Rayleigh fading. As described above, when the state of the communication path is good, there is almost no bit error in the transmission power control information received by the mobile station, and by using the transmission power control information as it is, the transmission power can be correctly adjusted. Control is performed. Also, when the state of the communication path is poor, the transmission power control information received by the mobile station has many bit errors, so the transmission power control based on the transmission power control information is not performed, and the transmission power is maintained as it is. I do.

However, in such a conventional closed-loop transmission power control device, when the reception signal level fluctuates due to fading or the like while the transmission power is not controlled due to the poor communication path condition. However, the mobile station cannot follow the level fluctuation, causing a problem that the communication line is disconnected and the capacity of the entire mobile radio communication system is reduced. In addition, the average Eb / Io of the received signal level is used to determine the quality of the communication path, and the Eb / Io of the received transmission power control information itself is not looked at. Occurs.

Therefore, the present invention has been made in view of the above circumstances, and is particularly susceptible to an error in transmission power control information that occurs sporadically, and achieves accurate transmission power control within a predetermined period. An object of the present invention is to provide a very good closed-loop transmission power control device for a mobile radio communication system.

[0015]

A closed-loop transmission power control apparatus for a mobile radio communication system according to the present invention is a mobile radio communication system for performing radio communication between a base station and a mobile station. Generating and transmitting transmission power control information for controlling the transmission power of the mobile station from the received signal,
The mobile station is intended for a closed-loop transmission power control device that controls transmission power based on received transmission power control information.

Then, the mobile station transmits the received transmission power control information through a digital filter to control the transmission power. In this case, the filter characteristics may be varied by changing the multiplication coefficient of the digital filter according to the quality of the received signal.

Further, the closed-loop transmission power control apparatus for a mobile radio communication system according to the present invention, in the above-mentioned object, provides the mobile station with transmission power control information received by the mobile station and information obtained by passing the transmission power control information through a digital filter. Are selectively provided for the control of the transmission power according to the quality of the received signal.

Furthermore, the closed-loop transmission power control apparatus for a mobile radio communication system according to the present invention, in the above-mentioned object, is configured such that the mobile station multiplies the received transmission power control information by a coefficient corresponding to the quality of a received signal. By controlling the transmission power, the control range of the transmission power is changed.

According to the above-described configurations, all of them are designed to alleviate the change in the transmission power and reduce the level fluctuation, and thus are particularly susceptible to the one-time error of the transmission power control information. It is difficult to perform accurate transmission power control within a predetermined period.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, the same parts as those in FIG. 8 are denoted by the same reference numerals.
That is, on the mobile station side, the threshold judgment circuit 20 and the Eb / Io measurement circuit 21 do not judge the quality of the communication path, and the transmission power control information output from the power control bit extraction circuit 19 is passed through the digital filter 22. What is different from the related art is that the gain control of the transmission amplifier circuit 12 is performed.

As the digital filter 22, for example, a FIR (Finite Impulse Response) filter or II
An R (Infinite Impulse Response) filter or the like is applied. FIG. 2 shows an example of the FIR filter. In this example, a three-stage filter using two shift registers 22a and 22b is shown.

That is, the input transmission power control information X
in is the two shift registers 22a, 22 connected in series.
2b. Then, the transmission power control information X0 before the delay and the transmission power control information X1, X2 output from the shift registers 2a, 22b are added to the multiplication circuits 22c, 22c.
Predetermined coefficients a0, a1 and a2 are multiplied by 22d and 22e, respectively, and the multiplication results are added by an adder circuit 22f to become an output Yout.

FIG. 3 shows that the transmission power control information extracted by the power control bit extraction circuit 19 is, for example, “1,
0, 1, 0, 1, 1, 1, 1, 0,... ”, A change in the transmission power when the gain control of the transmission amplifier circuit 12 is directly performed using the transmission power control information; The transmission power control information is passed through an FIR filter serving as a digital filter 22, and a change in transmission power when gain control of the transmission amplifier circuit 12 is performed is shown for comparison.

When the transmission power control information is used directly for the gain control of the transmission amplifier circuit 12, as described above, the transmission power is increased by 1 dB at "1" and decreased by 1 dB at "0". Is controlled as follows. The coefficients a0, a1, and a2 of the FIR filter are 1/2, 1 /
4, 1/4, and the transmission amplifier circuit 12 has a linear output characteristic.

As is apparent from FIG. 3, it is understood that the change in the transmission power is alleviated as a whole when the FIR filter is used, as compared with the case where the FIR filter is not used. For example, in section 1 shown from time t0 to t5, F
In the control without using the IR filter, the transmission power is repeatedly increased and decreased by 1 dB. This is because control for maintaining the level of the transmission power cannot be performed.

On the other hand, when the transmission power control information is passed through the FIR filter to control the gain of the transmission amplifier circuit 12, the change in the transmission power is reduced and the level fluctuation is reduced. In such a transmission power control state, for example, if the transmission power control information obtained at time t7 in section 2 has an error, that is, what is originally “0” is determined to be “1” due to the error. In this case, the error from the correct transmission power becomes 2 dB without the FIR filter, but the error can be suppressed to about 1.2 dB.

According to the first embodiment, the mobile station extracts the transmission power control information from the received signal, and uses the transmission power control information to control the gain of the transmission amplifier circuit 12 through the digital filter 22. As a result, the change in transmission power is mitigated and its level fluctuation is reduced, so that it is hard to be affected by errors of transmission power control information which occur especially spontaneously, and accurate transmission power is observed within a predetermined period. Control can be performed.

Next, FIG. 4 shows a second embodiment of the present invention. In FIG. 4, the same parts as those in FIG.
The switch 23 selectively transmits the transmission power control information output from the transmission power control information 9 and a signal obtained by passing the transmission power control information through the digital filter 22 to the gain control of the transmission amplifier circuit 12.

In this case, the switching of the switch 23 is controlled based on the output of the reception quality measuring circuit 24. The reception quality measurement circuit 24 determines the quality of the reception signal by measuring the quality of the reception data output from the digital demodulation circuit 18 and comparing the measurement result with a predetermined threshold value. .

When it is determined that the quality of the received signal is good, the switch 23 switches the transmission power control information output from the power control bit extraction circuit 19 to the transmission amplification circuit 12 as it is. If it is determined that the quality of the received signal is degraded enough to cause a bit error, the output is switched to guide the output of the digital filter 22 to the transmission amplifier circuit 12.

According to the second embodiment, when the quality of the received signal is good and the reliability of the transmission power control information is high, the transmission power control information is used as it is for the control of the transmission power. Quick transmission power control according to the reception state can be performed. Further, in a state where the quality of the received signal is degraded and the reliability of the transmission power control information is low, the transmission power control information is controlled by the signal passed through the digital filter 22 so that the bit of the transmission power control information can be controlled. Transmission power control that is hardly affected by errors can be performed.

Next, FIG. 5A shows a third embodiment of the present invention. This is because the control width of the transmission power based on the transmission power control information output from the power control bit extraction circuit 19 is 1 dB as described above, but this control width is to be varied according to the reception quality. .

That is, the transmission power control information output from the power control bit extraction circuit 19 is
Supplied to The variable control width device 25 includes a multiplication circuit 2
5a, the transmission power control information and the reception quality measurement circuit 2
Multiplying by a coefficient b corresponding to the reception quality determined in 4,
The result of the multiplication is used for gain control of the transmission amplifier circuit 12, thereby changing the control range of the transmission power.

The reception quality measurement circuit 24 measures the quality of the reception data output from the digital demodulation circuit 18, and compares the measurement result with two predetermined thresholds Thstep1 and Thstep2.
As shown in FIG. 5 (b), the quality of the received signal can be changed between a state where the bit reliability is higher than Thstep1 and a state where the bit error is larger than Thstep2 and
It is divided into the states of Thstep1 and Thstep2 between them.

In the variable control width device 25, the lower the received signal quality is, that is, each state of the quality Thstep1
As described above, the control width of the transmission power is changed by changing the value of the coefficient b to a small value of 1.0, 0.8, and 0.5 for Thstep1 to Thstep2 and Thstep2 and lower, respectively. According to the coefficient b, when the received signal quality is good and the reliability is high, the control width of the transmission power is 1 dB, and as the received signal quality deteriorates, the control width of the transmission power becomes 0.8 dB, 0. It will change to 5 dB.

FIG. 6 shows a fourth embodiment of the present invention. This is to use an active filter whose characteristic can be changed by changing the multiplication coefficient as the digital filter 22, and to change the multiplication coefficient of the digital filter 22 according to the reception quality.

As described above, it is considered that an FIR filter is used as the digital filter 22 and its coefficients a0, a1, and a2 are changed according to the reception quality. The reception quality measurement circuit 24 measures the quality of the reception data output from the digital demodulation circuit 18 and compares the measurement result with three predetermined thresholds Thf1, Thf2, Thf3, as shown in FIG. In addition, the quality of the received signal is set to Thf1 or higher,
The state is divided into a state of f1 to Thf2, a state of Thf2 to Thf3, and a state of Thf3 or less.

Then, in the FIR filter, the values of the coefficients a0, a1, and a2 are changed as shown in FIG. 7 for each of the states of the received signal quality Thf1 or more, Thf1 to Thf2, Thf2 to Thf3, and Thf3 or less. This changes the filter characteristics. According to the coefficients a0, a1, and a2, when the received signal quality is equal to or higher than Thf1, which is highly reliable, the transmission power control information is directly provided to the gain control of the transmission amplifier circuit 12, and the reception signal is received. If the signal quality is equal to or less than Thf3, the sum of the coefficients a0, a1, and a2 is less than 1, indicating that the control width has been changed.

Here, in the reception quality measurement circuit 24 shown in FIG. 4 and FIG. 6, the average Eb / Io of a plurality of symbol sections is not used for the judgment of the quality of the reception signal as in the conventional case.
If the energy value of the transmission power control information, that is, Eb / Io of the transmission power control information is used, more accurate determination can be performed.

It should be noted that the present invention is not limited to the above-described embodiments, and can be variously modified and implemented without departing from the scope of the invention.

[0041]

As described in detail above, according to the present invention,
In particular, the present invention provides a very good closed-loop transmission power control apparatus for a mobile radio communication system which is hardly affected by an error of transmission power control information which occurs sporadically and which can perform accurate transmission power control within a predetermined period. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing an example of an FIR filter according to the first embodiment.

FIG. 3 is a view for explaining a transmission power control operation in the first embodiment.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a view for explaining a third embodiment of the present invention;

FIG. 6 is a block diagram showing a fourth embodiment of the present invention.

FIG. 7 is a view for explaining the relationship between received signal quality and filter coefficients according to the fourth embodiment.

FIG. 8 is a block diagram showing a conventional closed-loop transmission power control device.

[Explanation of symbols]

 11: Digital modulation circuit, 12: Transmission amplification circuit, 13: Digital demodulation circuit, 14: Eb / Io measurement circuit, 15: Power control data generation circuit, 16: Addition circuit, 17: Digital modulation circuit, 18: Digital demodulation circuit Reference numeral 19: power control bit extraction circuit, 20: threshold value judgment circuit, 21: Eb / Io measurement circuit, 22: digital filter, 23: switch, 24: reception quality measurement circuit, 25: control width variable device.

Claims (5)

[Claims] 1. A mobile radio communication system for performing radio communication between a base station and a mobile station, wherein the base station comprises:
In a closed-loop transmission power control device that generates and transmits transmission power control information for controlling transmission power of a mobile station from a received signal and controls the transmission power based on the received transmission power control information at the mobile station. A closed loop transmission power control apparatus for a mobile radio communication system, wherein the mobile station transmits the received transmission power control information through a digital filter to control transmission power. 2. The closed-loop transmission of a mobile radio communication system according to claim 1, wherein the filter characteristic of the digital filter is changed by changing a multiplication coefficient according to the quality of a received signal. Power control device. 3. A mobile radio communication system for performing radio communication between a base station and a mobile station, wherein the base station comprises:
In a closed-loop transmission power control device that generates and transmits transmission power control information for controlling transmission power of a mobile station from a received signal and controls the transmission power based on the received transmission power control information at the mobile station. In the mobile station, the received transmission power control information and the information obtained by passing the transmission power control information through a digital filter are selectively subjected to transmission power control according to the quality of a received signal. A closed-loop transmission power control device for a mobile radio communication system. 4. A mobile radio communication system for performing radio communication between a base station and a mobile station, wherein the base station comprises:
In a closed-loop transmission power control device that generates and transmits transmission power control information for controlling transmission power of a mobile station from a received signal and controls the transmission power based on the received transmission power control information at the mobile station. The mobile station multiplies the received transmission power control information by a coefficient corresponding to the quality of a received signal to control the transmission power, thereby changing the control width of the transmission power. A closed loop transmission power control device for a mobile radio communication system, characterized in that: 5. The closed-loop transmission power of a mobile radio communication system according to claim 2, wherein the quality of the received signal is determined based on an energy value of the received transmission power control information. Control device.