JPS5824056B2 - mobile radio communication system - Google Patents

Abstract

PURPOSE:To reduce the capacity of a mobile station without degradation of the talking quality, by providing a circuit with detects the average receiving electric field of radio waves from the base station, in the mobile station and by lowering carrier wave output power for nonmodulation according to the intensity of the average receiving electric field. CONSTITUTION:Different frequencies are used for transmission and receiving, and the radio frequency is modulated to perform simultaneousu talking in the mobile station and the base station, and the receiving electric field from the mobile station is monitored by base station receiving electric field detecting circuit 10; and when the receiving electric field intensity is zero for a prescribed time or more, service is decided as terminated to open the radio circuit. Compressor circuit 1 which compresses the level range of input modulation signal A, modulation signal discriminating circuit 4 which discriminates existence of signal A, and power source current control circuit 5 which lowers the power source current applied to transmission power amplifying circuit 3 to lower transmission power to a fixed level when signal absence is decided in circuit 4 are arranged in the mobile station of this mobile radio communication system, and carrier wave output power for nonmodulation is lowered according to the intensity of the average electric field from the base station.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mobile radio communication system, and in particular to a mobile radio communication system that can save power consumption of a mobile station without degrading call quality between a mobile station and a base station, such as a mobile phone. In this method, a service area is divided into multiple wireless zones, a wireless base station is installed in each wireless zone, and communication is performed between multiple mobile stations and the base station.

Furthermore, in the public automobile telephone system, a wireless base station is connected to a general telephone network via a mobile message control station and a mobile message switching center.

In this method, simultaneous calls are made between the radio base station and the mobile station using different frequencies for transmission and reception, but since the limited frequency is shared by an unspecified number of mobile units, the frequency is used effectively. Must.

Therefore, conventionally, when a mobile device moves out of the calling area where radio waves do not reach during a call and the call cannot be made, or when the mobile device's wireless device malfunctions during a call and the call becomes impossible, In order to allow other mobile units to use the shared radio frequency without having one mobile unit hold it forever, the base station controls the wireless line.
A method is used in which communication with a mobile unit that cannot be used is considered to be terminated, and the wireless line is forcibly disconnected.

Therefore, the base station monitors the field strength received from the mobile station during a call, and determines that the mobile station has become unable to communicate when the radio waves from the mobile station are interrupted for a certain period of time or more.

By the way, in the press-to-talk format that is commonly used when performing wireless communication with a specific party, the transmission output of the mobile station is intermittent, and when the transmission output of the mobile station is cut off, the base station By providing a squelch circuit that suppresses noise output from the demodulator, high-quality communication is maintained by preventing noise from being output from the receiver.

On the other hand, in the public car telephone system, when the transmission output of the mobile station is cut off and the squelch circuit of the base station is activated, the radio waves from the mobile station are cut off, and the mobile station becomes unable to communicate. Since the base station determines that
Unlike the press-to-talk format, the transmission output cannot be intermittent.

In the conventional public car phone system, as shown in Figure 1,
After inputting the modulation signal A to the modulation circuit 2 of the mobile station to modulate the carrier wave and amplifying the transmission power in the amplifier circuit 3, the antenna B
When a radio wave is transmitted from the base station, the radio wave is received by the receiving circuit 7 of the base station via the radio propagation path C from the antenna D, and the demodulated signal E is extracted by the demodulating circuit 8.

Furthermore, at the base station, the received electric field detection circuit 10 constantly monitors the received electric waves during a call.

After setting up a wireless link between the mobile station and base station,
Mobile stations constantly send out high-power radio waves.

In order to obtain this high transmission power, a large-capacity battery or a large-capacity generator is required as the mobile wireless device power supply 6, making the device larger and more expensive.

The purpose of the present invention is to eliminate such drawbacks by lowering the average transmission power of mobile stations without degrading call quality, thereby making it possible to simplify and reduce the capacity of power supplies for mobile radio devices. The objective is to provide a mobile radio communication system that

In the mobile radio communication system of the present invention, a compressor circuit for compressing the audio signal level and a control means for limiting transmission output power depending on the presence or absence of an audio signal or other modulated signal are installed in the mobile station, and a compressor circuit for compressing the audio signal level is installed in the base station. Each is equipped with an expander circuit that expands the signal and reproduces the original signal, and when the radio waves sent from the mobile station are in an unmodulated state with only a carrier wave, the transmission output level is reduced to the extent that the base station does not determine that the call is over. It is characterized by allowing

Furthermore, in the present invention, the mobile station is provided with a circuit that detects the average received electric field of radio waves from the base station, and the unmodulated carrier wave output power transmitted from the mobile station is reduced according to the magnitude of the average received electric field. .

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of the mobile radio communication system of the present invention.

In FIG. 2, the mobile station newly includes a compressor circuit 1 that compresses the level range of the input modulated signal A, an identification circuit 4 that determines whether or not there is an input modulated signal A, and an identification circuit 4 that determines that there is no signal. In addition to installing a current control circuit 5 that reduces the power supply current applied to the amplifier 3 to reduce the transmission output power to a certain level when the Install the panda circuit 9.

In the mobile station, when there is a voice or other modulated signal A, the identification circuit 4 identifies it, and the current control circuit 5 supplies a large current from the power supply 6 to the transmission power amplifier circuit 3.
Transmits high-power radio waves.

In addition, in the above-mentioned voice and other modulation signal manual A, "'
The other modulated signals °' are control digital signals for controlling the wireless line, etc.

That is, in order to set up and terminate a wireless line, it is necessary to perform procedures according to predetermined regulations, and conventionally, control signals other than voice have been used for this purpose.

At the base station, the reproduced audio signal E from the mobile station is
At the same time as the receiver takes out the receiver and makes a call, the detection circuit 10 detects the received field strength and inputs the output F to a radio channel control device (not shown) of the base station.

If there is no receiving electric field at antenna D, it is determined that the mobile station has become unable to communicate, and the wireless line is disconnected by the line control device.

In this way, by providing a means for controlling the power supply current in the mobile station, the power radiated from the antenna B can be lowered when there is no input modulated signal A, so the capacity of the power supply 6 of the mobile station can be reduced. It becomes possible to do so.

In addition, although fading exists in the radio propagation path C, the received field strength detection circuit 10 of the base station does not immediately indicate that communication is impossible even if the received electric field decreases due to fading, and can signal unreceivable signals with a certain margin. Output to F.

Since the radiated power of antenna B of the mobile station is reduced within this margin, it can be clearly distinguished from when the radiated power is completely cut off, and even when the radiated power has decreased, the received field strength detection circuit 10 There is no possibility that it will be determined that reception is not possible.

Note that when the radiated power of antenna B of the mobile station is lowered,
It is expected that noise will increase in the output of the demodulation circuit 8 of the base station, but when the radiation power of the antenna B is lowered, there is no input modulation signal A and the demodulation circuit 8 is in an unmodulated state.
The noise outputted from the circuit is removed by the expander 9 at the subsequent stage.

Recently, as one of the countermeasures against multipath fading,
Silabic companders, which perform companding operations on audio signals, are attracting attention.

A syllabic compander consists of a compressor that compresses an audio signal and an expander that restores the original audio signal through expansion.

When a compander is used to transmit a tone signal of constant amplitude, the compressor expresses the difference from the reference level in decibels and compresses it to 1/2, and the expander expands the difference to double.

The compressor input is S (dB), its output level is sc (dB), and the compander reference level is U (
dB), the following equation holds true.

A signal at the level expressed by the above equation (1) and the noise added on the transmission path are input to the expander.

When the signal level Sc is sufficiently higher than the noise level N, the expander operates to double the difference from the reference level, and as a result it operates as a U-8c (dB) attenuator. Become.

Therefore, the signal level S (dB
) and the noise level N (dB) are each expressed as follows.

(2) above means that the expander suppresses the noise level added on the transmission path without affecting the signal level,
This shows that the signal-to-noise power ratio of the transmission system can be improved by (U-8)/2 (dB).

If the point (reference level) at which the input and output levels of the compressor 1 provided in the mobile station and the expander 9 provided in the base station are equal is set high, the degree of improvement in the signal-to-noise ratio will be improved.

In addition, in an actual call state, the time during which a mobile station transmits modulated waves is considered to be 1/2 to 1/4 of the time of one call, so even if this is 1/2, the time spent transmitting modulated waves during non-modulation is If the power is reduced by 10 dB, the average output power for one call time can be reduced to 11/20 compared to the conventional one, and at the same time, the capacity of the power supply 6 of the mobile station can be reduced.

FIG. 3 is a block diagram of a mobile radio communication system showing another embodiment of the present invention.

In FIG. 3, the configuration on the base station side is the same as that in FIG. 2, but a field strength detection circuit 12 is installed on the mobile station side, and the transmission output power in the non-modulated state is controlled by the received field strength.

That is, the radio waves received by the antenna B of the mobile station are input to the receiving circuit 11, the received field strength is detected by the field strength detection circuit 12, and the demodulated output G is obtained. 5 to adjust the transmission output power when no modulation is performed.

That is, when the reception electric field of antenna B is strong, the transmission output power when no modulation is performed is significantly reduced, and when the reception electric field is weak, the transmission output power when no modulation is performed is slightly reduced.

When a mobile station having the circuit configuration shown in FIG. 3 communicates,
The output power of the radio waves emitted from the mobile station is adjusted depending on the condition of the radio propagation path and the distance, so no matter where the mobile unit is located within the communication area, the base station can maintain an almost constant electric field strength without modulation. radio waves can be received, and the probability of erroneously determining that the mobile station is unable to communicate is reduced.

Furthermore, when the mobile unit is near the base station, the power consumption of the mobile station can be further reduced than in the case of FIG.

As a result, the amount of heat generated by the transmitting circuit can be reduced, so that the heat dissipation fin of the mobile station radio device can be made smaller.

In the embodiment, a case has been described in which the present invention is applied to a public automobile telephone system, but it is of course applicable to a public mobile telephone system, etc.

As explained above, according to the present invention, the average transmission power per call of the mobile station can be reduced while maintaining the same call quality as when the mobile station always transmits with high output power. The capacity of the wireless device can be reduced, and the base station is less likely to misjudge that a call is unavailable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional mobile radio communication system, FIG. 2 is a block diagram of a mobile radio communication system showing an embodiment of the present invention, and FIG. 3 is a block diagram of a mobile radio communication system showing another embodiment of the present invention. FIG. 1: Compressor circuit, 2: Modulation circuit, 3: Transmission power amplification circuit, 4: Modulation signal identification circuit, 5: Power supply current control circuit, 6: Power supply device, 7: Base station reception circuit, 8: Base station demodulation circuit, 9: expander circuit, 10: base station received electric field detection circuit, 11: mobile station reception circuit, 12: mobile station received electric field detection circuit, 13: mobile station demodulation circuit, A: modulated signal input, B. D: antenna, C: radio propagation path, E: demodulated signal output, F
: Received electric field detection signal output, G: Demodulation signal output.

Claims (1)

[Claims] 1. When different radio frequencies are used for transmission and reception, the radio frequency signals are modulated to make simultaneous calls, and the received field strength from the mobile station is monitored by the base station, and the received field strength becomes zero for a predetermined period of time or more. In a mobile radio communication system in which a call is deemed to be over and the radio line is released, the mobile station is equipped with a compressor circuit for compressing the audio signal level and a control means for limiting the transmission output power depending on the presence or absence of the audio signal or other modulation signal.
In addition, each base station is equipped with an expander circuit that expands the compressed audio signal and reproduces it to the original signal, and the unmodulated carrier wave output power sent from the mobile station is within a range where the base station does not judge that the call is over. A mobile radio communication system characterized by reducing the