JPH0616595B2 - Transmission power control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The transmission power of a transmitting station is set to a value sufficient to maintain sufficient line quality in normal times, and the degree of change in a received signal due to fading applied to the line increases, In response to the differential coefficient of the received signal at the receiving station exceeding the reference value, the transmission power of the transmitting station when the differential coefficient of the received signal is smaller than the reference value is sufficient to compensate the changing speed of radio wave propagation. Increase the transmission power by the value and transmit the radio wave to the receiving station.

TECHNICAL FIELD The present invention relates to a transmission power control method, and more specifically,
The present invention relates to a transmission power control method that uses a differential coefficient of a received signal for transmission power control for power reduction and the like.

In a wireless communication network such as digital multiplex wireless communication, when transmitting desired information from a transmitting side to a receiving side,
The information will be sent on radio waves. In order for the reception side of the radio wave to be successfully received, the radio wave must be radiated from the transmission side to the reception side with the transmission power required for it. Then, in the transmission, the transmission power must be determined in consideration of not only the transmission capacity of the transmission / reception system but also the state of the transmission medium. In addition, it is important to consider the state of other transmission / reception systems regardless of whether they are existing or not in the area where the transmission / reception system is in custody in order to maintain various unmanned communication systems in that area. It is a matter.

[Conventional technology]

The conventional digital multiplex wireless communication system is constructed as shown in FIG. The transmission signal modulated by the modulator 2 on the transmitting side is frequency-converted from the IF band to the RF band by the transmitter 4. The output signal of the transmitter 4 is the power amplifier 14
Power is amplified by the transmitting antenna 16 to the receiving antenna 3
It radiates toward 0. The signal received by the receiving antenna 30 is frequency-converted from the RF band to the IF band by the receiver 32, and then AGC-amplified by the AGC amplifier 34 to be demodulated by the demodulator 36.
It is used for reproduction of the transmission signal in.

The transmission power in such a transmission / reception system is the AG of the reception side.
Even when the gain adjusting function of the C amplifier 34 approaches the upper limit thereof, the radio wave having a sufficient intensity to maintain the line quality can be radiated from the transmitting antenna 16 to a predetermined value. , It used to be set.

[Problems to be solved by the invention]

However, the setting of the transmission power as described above can be affirmed from the viewpoint of maintaining the line quality, but from the viewpoint of power saving, the transmission power is unnecessarily large for a long time. It means that the information is transmitted by electric power. This is because the transmission power set as described above has a large line loss (mainly a loss due to fading) that lasts only about 5 to 10 hours a year, so that such a large transmission power is used in other time zones. This is because it is determined that the desired line quality is maintained in the time zone in which a large line loss occurs as described above, although the above is not required.

Further, with the above-mentioned large transmission power, there is no problem if there is no other transmission / reception system in the area where the transmission / reception system is installed, but if it is not so, the influence occurs, which is inconvenient.

The present invention was created in view of such problems, and when the rate of change of the received signal is equal to or lower than the reference value, the transmission power is set to a small value, and only when the rate of change of the received signal exceeds the reference value, the transmission power is set. It is an object of the present invention to provide a transmission power control method for improving communication quality and maintaining communication quality.

[Means for solving problems]

FIG. 1 shows the principle configuration of the present invention. In the figure, 2 is a transmitter of the transmitting station 4, 6 is a transmission power changing means for changing the transmission power level, and 7 is a transmission level control means. Reference numerals 10 and 12 are transmission / reception antennas. 13 is connected to the receiving station 16 and its receiver 18,
The transmission electrode control information output means outputs the first transmission power control information when the differential coefficient of the received signal is smaller than the reference value determined from radio wave propagation, and outputs the second transmission power control information when the differential coefficient is larger.

The second transmitted from the transmission power control information output means 13 to the transmitter 18 of the transmission station 4 via the system of the wireless communication system.
The transmission level control means 7 that responds to the transmission power control information of is the change rate of the radio wave propagation that has generated the second transmission power control information rather than the transmission power at the time of the first transmission power control information. By making the transmission power changing means 6 output a power large enough to compensate for
The present invention has been constructed.

[Work]

During communication in a state where the fading speed is relatively small and the differential coefficient of the received signal is less than or equal to the reference value, the transmission power changing means 6 causes the transmission power control information output means 13 to feed back the first transmission power control information. The transmission level changing means 7 for receiving the signal sets the transmission power to a predetermined relatively low level, radiates radio waves from the transmission antenna 10 of the transmission station 4 to the reception antenna 12 of the reception station 16, and performs the required communication. Is done.

When the fractional number of the received signal received by the receiving station 16 via the communication line becomes larger than the reference value due to fading, the second transmission power control information for increasing the transmission power is the transmission power control information. It is generated from the output means 13 and transmitted from the reception antenna 12 to the transmission level control means 7 via the transmission antenna 10 and the receiver 18.

The transmission level control means 7 changes the set level of the transmission power changing means 6 so as to raise the transmission power level in response to the second transmission power control information. Then, as the fading is restored, the transmission level control means 7 changes the transmission power level to a low level.

Since the normal period of radio wave propagation is long and the transmission power during that period is small, the abnormal period of radio wave propagation as described above is short throughout the year, so even if the transmission power is increased during an abnormality, the amount of power required for communication is , Less is required.

Further, at the low transmission power as described above, the degree of communication interference to other systems can be reduced and the radio wave distribution to the area can be increased.

〔Example〕

FIG. 2 shows an embodiment of the present invention. In this figure, 4
_1, 16 ₁ transceiver station, 2,18 are each transmitter of each transceiver stations, a receiver. 8 is a transmission level control circuit, 14
Is a fading speed detection circuit. These circuits 8, 1
4 is shown only for one transmitting / receiving station for the sake of clarity of the drawing, but is provided for each station.

The configurations of the transmitter 2 and the transmission level control circuit 8 are shown in FIG. The transmitter 2 includes an IF amplifier 2 ₂ , a mixer 2 ₂ ,
Transmitter local oscillator 2 ₃ , variable attenuator 2 ₄ and RF amplifier 2
₅ (in the figure, between f _If, f _{TL, and} f _T , | f _T −f
_TL | = f _If . As the variable attenuator 2 ₄ shows a configuration example of a transmission power changing means 6 of FIG. 1, which is input to the RF amplifier 2 ₅ gives attenuation determined in accordance with the analog voltage value to the RF signal, i.e. the transmission power It is for changing the level. The analog voltage is output from the transmission level control circuit 8, which is connected to the receiver 18
Signal output from the instruction signal reproducing circuit 20 connected to the output of the AGC amplifier 18 _5, for example, for the attenuation decreased in response to the high level signal "1" when a transmission power control command, for example, attenuation An analog signal for canceling, and an analog signal for increasing the attenuation amount according to the low level signal "0" are output when there is no analog signal.

The structure of the receiver 18 is shown in FIG. In this figure, the receiver 18 comprises an RF amplifier 18 ₁ , a mixer 18 ₂ ,
Reception local oscillator 18 ₃ , IF band pass filter (IFB
PF) 18 ₄ and AGC amplifier 18 ₅ . AGC amplifier 18 ₅ has an output 1 and output 2, output 1 is connected to a demodulator (not shown), output 2 command signal reproduction circuit 2
Connected to 0.

The fading speed detection circuit 14 detects the fading speed with a signal differential coefficient and outputs a transmission power control command, and the output signal thereof is configured to be transmitted to the opposite station via the transmitter 2 of the own station. . Fading speed detection circuit 14 AGC of the AGC amplifier 18 ₅ above the receiver 18
Differentiating circuit 14 ₁ receiving the control voltage, absolute value generating circuit 14 ₂ ,
It is composed of a comparison circuit 14 ₃ and a knot circuit 14 ₄ . The absolute value generation circuit 14 ₂ receives the output of the differentiation circuit 14 ₁ at _one input,
Operational amplifier 14 ₂₁ , which receives a zero voltage at the other input, diodes 14 ₂₂ and 14 ₂₃ having cathodes connected to the non-inverting output and the inverting output of the operational amplifier 14 ₂₁ , and diodes 14 ₂₂ and 14
A resistor 14 ₂₄ connecting the anode to the operating power supply V _23, the output of the absolute value generating circuit 14 ₂ is diode 14 _22,
14 ₂₃ and the resistor 14 ₂₄ are connected.

The transmission power control mode under the above configuration will be described below.

Now, the transmission level control circuit 8 of the transceiver station 4 _1, 16 _1, the derivative of the received signal between the transmitting and receiving stations 4 _1, 16 _1, i.e., the fading speed in a state in the following predetermined values,
It is assumed that the antenna 10 or 12 is set to radiate radio waves toward the opposite station at a relatively low transmission power level that is sufficient to make the transmission level equal to or higher than a predetermined value.

In such a setting, the IF input signal of the frequency f _If to the transmitter 2 is amplified by the IF amplifier 2 ₁ to be mixed by the mixer 2 ₂
Input to, RF signals are frequency converted in the mixer _{2 2} which receives a local oscillation signal of a frequency _{f T} from the transmission local oscillator _{2 3} together with its signal is changed to _{(| = f If | f T} -f TL). This RF signal is amplified by the RF amplifier ₂₅ and its amplitude is attenuated by the analog signal from the transmission level control circuit 8 so that the transmission power level supplied to the antenna 10 becomes the above-mentioned level. ₅
Is input to. Thus, a radio wave whose transmission power level is the above level is radiated toward the opposite station to perform the required communication.

It is received by the antenna 12 of the opposite station 16 _1, RF amplifier 1
The RF signal amplified by 8 ₁ is input to the mixer 18 ₂ ,
Mixer 18 the RF signal for receiving a local oscillation signal of a frequency f _RL = f _TL from the reception local oscillator 18 ₃ with the signal
_{In 2} the frequency is converted into an IF signal of frequency f _If , which is input to the AGC amplifier 18 ₅ via the IF bandpass filter 18 ₄ . The IF signal increased to the output 1 and output is input to a demodulator (not shown) and used to reproduce the transmission signal.

AGC control voltage of the AGC amplifier 18 ₅ differentiating circuit 14 ₁
And the differential coefficient signal of the voltage signal is output from there. This differential coefficient signal is a signal that reflects the differential coefficient of the received signal, that is, the fading speed, as shown in FIG. Its derivatives signal as can be seen from Figure 6, since a positive and negative value, to generate the absolute value from the absolute value generating circuit 14 _2. Its value is compared in a comparison circuit 14 ₃ with a reference voltage r for the fading speed. When the absolute value <r, a binary signal of high level "1" is output from the comparison circuit 14 ₃ . Therefore, from the NAND circuit 14 ₄ is output transmit power control command "0". This command is sent to your own station 16 ₁
Is transmitted to the opposite station 4 ₁ via the transmitter 2 and the antenna 12, and is given to the transmission level control circuit 8 via the antenna 10 and the receiver 18 of the opposite station 4 ₁ . Thus, the signal from the circuit 8 maintains the transmission power level at a level capable of maintaining the line quality.

In such a transmission / reception state, if the rate of change in the received signal due to fading increases, the change in the signal level received at the opposite station radiated at the set transmission power level as described above also increases accordingly.

Therefore, the larger the derivative signal outputted from the differentiation circuit 14 ₁ and as described above. The absolute value signal from the generating circuit 14 ₂ is allowed to output a signal of "0" from the comparator circuit 14 _3. As a result, transmission power control command "1" from the NAND circuit 14 ₄ is output. This command is also transmitted to the opposite station in the same manner as described above. In this case, the signal level given from the receiver 18 to the transmission level control circuit 8 is a high level "1". To the variable attenuator 2 ₄ from the transmission level control circuit 8, allowed to reduce the amount of attenuation therein, the analog signal is generated, for example do not provide damping. As a result, the transmission power level of the radio wave radiated from the antenna 10 is increased, and the opposite station can receive the radio wave at a reception level that can maintain the line quality at a desired value.

The reduction of the transmission power level at the time of restoration of the reception level change due to fading occurs with the loss of the transmission power control command of "1".

It should be noted that, in the above-mentioned embodiment, the transmission power is controlled by 2
Although the example in which the binary information “0” or “1” is used has been shown, the transmission power control may be performed in another binary information format, for example, the multilevel adjustment format may be changed. The change in transmission power may be brought about by adjusting the variable power amplifier. Also, the reduction of the transmission power level mentioned above may occur with a certain time delay.

〔The invention's effect〕

As described above, according to the present invention, according to the conventional knowledge, the time required to transmit under a large transmission power is only a relatively small time even in a year. According to the method of the present invention, in which the transmission power is increased only to maintain the line quality, the transmission power can be significantly reduced, the degree of communication interference to other systems can be reduced, and the radio wave distribution to the area can be increased. it can.

[Brief description of drawings]

1 is a block diagram of the principle of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, FIG. 3 is a block diagram of a transmitter and a transmission level control circuit, FIG. 4 is a block diagram of a receiver, FIG. 5 is a fading speed detection circuit diagram, FIG. 6 is a reception level fluctuation curve diagram, and FIG. 7 is a configuration diagram of a conventional digital multiplex wireless communication system. 1 to 5, 2 is a transmitter, 4 is a transmission station (transmission / reception station 4 ₁ ), 6 is transmission power changing means (variable attenuator 2 ₄ ), and 7 is transmission level control means (transmission level control circuit). 8), 10 and 12 are transmission / reception antennas, 13 is transmission power control information output means (fading speed detection circuit 14), 16 is a reception station (transmission / reception station 16 ₁ ), and 18 is a receiver.

Claims (1)

[Claims] 1. A wireless communication system for amplifying a transmission signal by a transmitter (2) of a transmission station (4) and radiating the amplified signal toward an opposite reception station (16) to perform required communication. 4) is provided in the transmitter (2),
While the transmission power changing means (6) and the transmission level control means (7) for changing the transmission power are provided, the receiving station (16) is connected to the receiver (18) thereof, and the differential coefficient of the received signal is Outputs the first transmission power control information when it is smaller than the reference value determined from radio wave propagation,
A transmission power control information output means (13) for outputting the second transmission power control information when the transmission power is large is provided, and the transmission power control information output means (13) outputs the transmission power control information from the transmission station (4) via the system of the wireless communication system. The transmission level control means (7) that responds to the second transmission power control information sent to the receiver (18) has the second transmission power higher than the transmission power at the time of the first transmission power control information. The transmission power control method is characterized in that the transmission power changing means (6) outputs electric power that is large enough to compensate for the changing speed of the radio wave propagation that has caused the transmission power control information.