JPH0523527B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an interference wave detection method in a mobile communication system without a central control station.

Conventionally, when a plurality of mobile radio devices connect to a fixed radio device using a plurality of channels, a method has been adopted in which a connection channel is determined and each communication is conducted without depending on a central control station. An example of this type of mobile communication system is a cordless telephone. In this cordless telephone system, as shown in the system diagram in FIG. mobile radio) 101', 10
2' and 103' are wireless connection devices 101 and 103', respectively.
102 and 103 are opposite to each other. And between these opposing wireless connection devices and wireless telephones, there is a pair of radio frequencies (channels) ₁ and ₁ ',
Connected by ₂ and ₂ ′ and ₃ and ₃ ′.
For this purpose, for example, the wireless connection device 101 and the wireless telephone 101', the wireless connection device 103 and the wireless telephone 1
Even if 03' is in a wireless communication state,
Since the wireless connection device 102 and the wireless telephone 102' are not in a communication state, frequencies ₂ and ₂ ' are used in vain during that time.

Therefore, as shown in FIG. 2, effective use of frequencies is achieved by a multi-frequency switching connection method. According to this system, for example, the wireless connection devices 104, 105, and 106 have ₁ and ₂ waves, respectively, and one of them can be used by switching. Wireless telephone 1
04', 105' and 106' have ₁ ' and ₂ ' waves corresponding to ₁ and ₂ , respectively, and one of them is used. As shown in the figure, wireless connection device 1
If 06 and wireless telephone 106' use ₁ and ₁ ' respectively, wireless connection device 104 and wireless telephone 104'
makes a call using the remaining ₂ and ₂ ′. Normally, the probability that all wireless connections and wireless telephones are used at the same time is small; for example, wireless connection 105 and wireless telephone 105' are not in use. This method does not waste frequency usage, and ₁ and ₁ ′ and ₂ and
₂ ′ waves are effectively used. However, since there is no special frequency control station to control the frequency of each wireless connection device and wireless telephone, the wireless connection devices and wireless telephones must operate while controlling frequency switching when transmitting and receiving radio waves. .
Now, when the wireless connection device 106 and the wireless telephone 106' are communicating with each other on frequencies ₁ and ₁ ',
Suppose that the wireless connection device 105 and the wireless telephone 105' enter into a communication state using the same waves of frequencies ₁ and ₁ '. However, if the wireless telephone 105' moves while it is busy and approaches the wireless connection device 106, the wireless telephone 105' and the wireless connection device 1
06, crosstalk occurs between the wireless telephones 106'.
In other words, in such a frequency switching connection system, it is not possible to prevent the occurrence of crosstalk due to multiple use of frequencies simply by providing a multi-frequency switching function to the wireless connection device and wireless telephone in order to make effective use of frequencies. There was a problem. For example, when this method is applied to general public communications, etc., it is possible to mutually confirm available wireless channels at the start of a call and start a call using that wireless channel, but after the call starts, the same wireless Crosstalk occurs due to the proximity of wireless telephones using the channel, and the reliability of public communications can no longer be maintained.

An object of the present invention is to detect interference waves that can prevent the occurrence of crosstalk due to the proximity of mobile radio devices to each other, even though a multi-frequency switching connection method is adopted in a mobile communication system that does not have a central station for frequency control. There is a method to provide.

According to the present invention, the transmission side of a mobile radio device is provided with a pilot signal generating means for identification, a means for superimposing the pilot signal on the audio output, and a means for attenuating the modulated output of the superimposed wave for a short time. , providing means for detecting interference waves between a transmission wave from the mobile radio device and a transmission wave from another mobile radio device using the received and demodulated pilot signal on the receiving side of the fixed connection radio device; When interference output from the interference wave detection means is detected, a control signal is sent from the transmitting side of the fixed radio device to the receiving side of the mobile radio device to change the channel frequency of the mobile radio device. An interference wave detection method for a mobile communication system is obtained.

Next, embodiments according to the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram showing the structure of an embodiment according to the present invention. In this figure, a
is a subscriber line, R is a rosette, 13 is a wireless connection device, and 27 is a wireless telephone. Of these, the wireless connection device 13 includes a hybrid 1, a synthesis circuit 2, a modulation transmitter 3, an antenna 4, a control signal generation circuit 5, a transmitting station oscillator synthesizer 6, a connection device control device 7, a pilot signal detection circuit 8, and a receiver. power measurement circuit 9;
It is composed of a receiving station synthesizer 10, a filter 11, and a demodulation receiver 12. Hybrid 1 connects subscriber line a to rosette R.
The audio signal that has arrived via the demodulation receiver 12 and the filter 11 is sent to the synthesis circuit 2, and is received from the radio telephone 27 using b of the channel frequencies a and b used. It is sent to subscriber line a. A pilot signal detection circuit 8 detects a pilot signal from among the received signals demodulated by the demodulation receiver 12. A filter 11 removes the pilot signal from the demodulated received signal and extracts only the audio signal. The connecting device control device 7 receives the signals from the pilot signal detection circuit 8 and the received power measurement circuit 9, and
Depending on the output state, the frequencies of the transmitting station synthesizer 6 and the receiving station synthesizer 10 are controlled to be changed, and the control signal generating circuit 5 is controlled to send out a control signal for changing the channel frequency of the radio telephone 27. .

The radio telephone 27 also includes an antenna 14, a variable attenuator 15, a modulating transmitter 16, a combining circuit 17, a transmitter 18, a transmitting station synthesizer 19, a pilot signal generating circuit 20, a telephone controller 21, and a receiving station transmitter. Synthesizer 22, control signal detection circuit 2
3, a demodulation receiver 24, a filter 25, and a receiver 26. The synthesis circuit 17 superimposes the pilot signal from the pilot signal generation circuit 20 on the audio signal from the transmitter 18. The variable attenuator 15 receives the modulated signal from the modulated transmitter 16, changes its level under the control of the telephone controller 21, and then sends it to the antenna 14. When the control signal detection circuit 23 detects a control signal from the received signal demodulated by the demodulating receiver 24, the detection output is sent to the telephone control device 21, and sent to the transmitting station synthesizer 19 and the receiving station synthesizer 22. Control is performed to change the channel frequency. The filter 25 removes the control signal and extracts only the audio signal from the demodulated received signal.

Now, at the start of a call, the variable attenuator 15 of the wireless telephone 27 performs a short-time (several tens of milliseconds) attenuation operation according to instructions from the telephone control device 21 to a level that does not interfere with the call. Do the following.
On the other hand, the output of the demodulation receiver 12 of the wireless connection device 13 is connected to the pilot signal generation circuit 20 of the wireless telephone 27.
This pilot signal is detected by a pilot signal detection circuit 8. Here, if there is interference from another radio telephone different from the radio telephone 27, the radio telephone 2
When the radio waves from 7 are weakened by the attenuation of the variable attenuator 15, the pilot signal is not detected in the pilot signal detection circuit 8 even though there is sufficient power measured by the received power measurement circuit 9. become. Pilot signal detection circuit 8 at this time
And according to the measurement results of the received power measurement circuit 9,
The connecting device control device 7 controls the control signal generation circuit 5. The control signal generation circuit 5 sends out a control signal to contact the radio telephone 27 in order to change the channel frequency of the radio telephone 27. The telephone controller 21 changes the frequencies of the synthesizers 19 and 22 in accordance with the control signal received by the control signal detection circuit 23. On the wireless connection device 13 side, the frequencies of synthesizers 6 and 10 can also be changed.
Thus, once the pilot signal detection circuit 8 is in a state where it can receive the pilot signal at a sufficient level, it is then possible to make a call without crosstalk using this new channel frequency.

FIG. 4 is a circuit diagram showing a first specific example of the pilot signal detection circuit shown in FIG. In the figure, 30 is a high-Q tone filter that responds only to specific frequency components that correspond to the wireless telephone. This tone filter 3
The output of 0 is given to a rectifier and smoothing circuit composed of capacitors 31, 34, 37, diodes 32, 33, and resistors 35, 36, and converted to a DC voltage proportional to the input level. is obtained on the output side through. If there is sufficient level, the output of buffer 38 will be in a high level "1" state, but if there is interference, the level will drop to indicate a low level "0" state.

FIG. 5 is a circuit diagram showing a second specific example of the pilot signal detection circuit shown in FIG. In this example, a specific pattern is used as a pilot signal. In the figure, 4
0 is a filter, which separates the audio signal and the pilot signal to obtain the pilot signal on the output side. This pilot signal is compared by a comparison circuit 41 and shaped into a digital waveform. This digital signal is applied to a clock pulse regeneration circuit 42 and is regenerated as a clock pulse. Reference numeral 43 denotes a register for storing a pilot signal, which operates in response to a reproduced clock pulse. The contents of register 43 are [Q ₁ Q ₂ Q ₃ Q ₄ Q ₅ Q ₆ Q ₇ Q ₈ ] =
[10101101], inverters 44, 45,
46, the output of the AND gate 47 becomes "1". 48 is a counter, which is cleared when the output of the AND gate 47 is "1". When the output of the counter 48 is "0", the output of the inverter 49 becomes "1", and as a result, the gate 50 is opened and the counter 48 counts the output pulses of the clock pulse regeneration circuit 42. Normally, if the pilot signal is received normally,
Since the counter 48 is cleared each time, the output of the counter 48 is always in the state of "0". Here, if an error occurs in the pilot signal due to interference, the specific pattern of the pilot signal will not be input to the register 43, so the output of the AND gate 47 will not become "1", and as a result, the counter 48 will not be cleared. . Therefore, the gate 50 is open, and the counter 48 continues counting in response to the regenerated clock pulse, and eventually the output of the counter 48 becomes "1". As a result, the output of the inverter 49 becomes a low level "0", which notifies the connected device control circuit that there has been interference.

Comparing the pilot signal detection circuits in Figures 4 and 5, the circuit in Figure 4 is simple, but because it uses a specific frequency as the pilot signal, it When the number of pilots increases, the frequency settings of the pilot signals must be prepared for each number of pilots. Considering that there is a limit to the frequency arrangement, this results in a restriction on the number of devices that can be used. On the other hand, although the circuit configuration shown in FIG. 5 is complex, it has the advantage that hundreds of types of pilot signals can be prepared in principle by variously changing the pattern of the pilot signals.

As is clear from the above description, according to the present invention, when interference is received from another mobile radio telephone, the transmission power including the pilot signal from the own mobile radio telephone is reduced for a short period of time before crosstalk occurs. The fixed wireless connection device determines the presence or absence of a pilot signal in the received signal and detects the interference wave, thereby switching the wireless channel frequency and easily preventing crosstalk. It can be applied to any mobile communication system with a control central station, and a great effect can be obtained to improve the reliability of calls.

[Brief explanation of drawings]

Figure 1 is a system example showing a conventional mobile communication system without a central control station, Figure 2 is an example of a system in which a multi-frequency switching connection method is applied to a conventional mobile communication system without a central control station, and Figure 3 is a system example showing a mobile communication system without a conventional central control station. 4 is a block diagram showing the configuration of an embodiment according to the present invention, FIG. 4 is a circuit diagram showing a first specific example of the pilot signal detection circuit in FIG. 3, and FIG. FIG. 7 is a circuit diagram showing a second specific example. In the figure, 1 is a hybrid, 2 and 17 are synthesis circuits, 3 and 16 are modulation transmitters, 4 and 14 are antennas, 5 is a control signal generation circuit, 6 and 19 are transmitting station synthesizers, and 7 is a control for connecting equipment. 8 is a pilot signal detection circuit, 9 is a received power measurement circuit,
10, 22 are receiving station synthesizers, 11, 25
is a filter, 12 and 24 are demodulation receivers, 13 is a wireless connection device, 15 is a variable attenuator, 18 is a transmitter, 2
0 is a pilot signal generation circuit, 21 is a telephone control device, 23 is a control signal detection circuit, and 26 is a receiver.

Claims (1)

[Scope of Claims] 1. A pilot signal generating means for identification, means for superimposing the pilot signal on the audio output, and means for attenuating the modulated output of the superimposed wave for a short time are provided on the transmitting side of the mobile radio. and means for detecting an interference wave between a transmission wave from the mobile radio device and a transmission wave from another mobile radio device using the received and demodulated pilot signal on the receiving side of the fixed connection radio device. , when an interference output from the interference wave detection means is detected, a control signal is sent from the transmitter side of the fixed radio device to the receiver side of the mobile radio device to change the channel frequency of the mobile radio device. interference wave detection method for mobile communication systems. 2. In the interference wave detection method as set forth in claim 1, the interference wave detection means includes a circuit that receives the pilot signal and detects that the level thereof has fallen below a predetermined value. An interference wave detection method in a mobile communication system characterized by being configured as follows. 3. In the interference wave detection method according to claim 1, the interference wave detection means receives the pilot signal and determines by pattern matching whether or not the pattern matches a predetermined pattern. An interference wave detection method in a mobile communication system, characterized in that the system is configured by a circuit that performs the following steps.