JPH04258030A - Mobile body communication system - Google Patents

Abstract

PURPOSE:To smoothly continue talking by detecting a specific signal in a transmission signal from a base station and raising an alarm and displaying when the degree of an error of a specific code exceeds a reference value. CONSTITUTION:A synthesis circuit 14 of a transmitter 1 of a base station synthesizes a synchronizing signal of a synchronizing signal generating circuit 13 and a specific signal of a specific signal generating circuit 19 with a digitized voice signal. A specific signal detection circuit 27 receiving a digital signal amplified and demodulated by a reception circuit 22 of a receiver 2 of the mobile station detects the specific code from the digital signal. Then a bit error of the specific code is detected and when it is detected that the bit error exceeds a reference value, a signal is fed to a sounding body 28 and a light emitting body 29, from which alarm and display are implemented. Thus, before the talking disable state is reached, the talking continue procedure such as changeover of the adjacent service area onto the base station is executed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system using a digital modulation method.

0002

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional mobile communication system. In the figure, 1 is a transmitter of a base station that constitutes a mobile communication system, and 2 is a receiver of a mobile station that moves within the service area formed by this base station.

Reference numeral 11 denotes a microphone into which the voice to be transmitted is input, and 12 denotes an analog-digital encoder (hereinafter referred to as an A/D encoder) that converts the voice input from the microphone 11 into a digital code. Reference numeral 13 is a synchronization signal generation circuit that generates a synchronization signal, and reference numeral 14 is a synthesis circuit that synthesizes the synchronization signal from the synchronization signal generation circuit 13 and the signal digitized by the A/D encoder 12.

15 is an oscillator that generates a carrier wave;
6 is a modulator that modulates the carrier wave oscillated by the oscillator 15 with the output of the combining circuit 14. 17 is a high frequency amplifier that amplifies the signal modulated by the modulator 16, and 18 is a transmitting antenna that radiates the signal amplified by the high frequency amplifier 17 into space. The receiver 1 is composed of these.

Further, 21 is a receiving antenna that receives the signal radiated from the transmitting antenna 18, and 22 is a receiving circuit that amplifies and demodulates the signal received by the receiving antenna 21. 23 is a separation circuit that separates a synchronization signal from the signal demodulated by the receiving circuit and separates a signal obtained by digitally encoding audio, and 24 is a synchronization signal detection circuit that detects the synchronization signal.

Reference numeral 25 denotes a digital/analog decoder (hereinafter referred to as a D/A decoder) which decodes the digitally encoded signal from which the synchronization signal has been separated by the separation circuit 23 into an analog signal. Reference numeral 26 denotes a speaker for outputting audio signals converted into analog signals by the D/A decoder 25. Said receiver 2
is composed of these.

Next, the operation will be explained. The transmitter 1 of the base station transmits the audio input from the microphone 11 to the A/
The signal is digitized by the D encoder 12 and input to the synthesis circuit 14. As shown in FIG. 5, the synthesizing circuit 14 synthesizes the synchronizing signals generated by the synchronizing signal generating circuit 13 at predetermined intervals of the digitized signals, and sends it to the modulator 16.

The carrier wave oscillated by the oscillator 15 is input to the modulator 16 , and the modulator 16 modulates this carrier wave with the signal from the combining circuit 14 . The signal modulated by the modulator 16 is amplified to a predetermined level by the high frequency amplifier 17, and is radiated into space from the transmitting antenna 19.

On the other hand, in the receiver 2 of the mobile station, the signal radiated from the transmitting antenna 18 of the transmitter 1 is transmitted to the receiving antenna 2.
Receive at 1. The received signal is sent to a receiving circuit 22, amplified and demodulated into a digital signal, and then sent to a separation circuit 23 and a synchronization signal detection circuit 24.

The separation circuit 23 separates the synchronization signal synthesized by the synthesis circuit 14 of the transmitter 1 from among the input signals based on the detection signal from the synchronization signal detection circuit 24.
Extract the digitally encoded audio signal. The separated digital encoded signal of the synchronization signal is sent to a D/A decoder 25.
The signal is sent to the computer, decoded into an analog signal, and output as audio from the speaker 26.

In actual operation, the distance between the transmitter 1 and the receiver 2 constantly changes as the mobile station moves. FIG. 6 shows characteristics showing the relationship between the distance between the transmitter 1 and the receiver 2, the degree to which the digital signal is erroneously received (hereinafter referred to as bit error), and the clarity of the voice output from the speaker 26. It is a diagram.

As shown in the figure, the bit error increases little by little as the distance between the transmitter 1 and the receiver 2 increases, and increases rapidly after a certain distance. On the other hand, due to the characteristics of the A/D encoder 12, the clarity hardly deteriorates even if some bit errors occur, but it deteriorates extremely rapidly when the bit errors reach a certain level.

[0013] As a technical document similar to such a conventional mobile communication system, for example, Japanese Patent Application Laid-open No. 64-32
There are publications such as Publication No. 541.

[0014]

[Problems to be Solved by the Invention] Conventional mobile communication systems are configured as described above, so when a mobile station gradually moves away from a base station and moves to the boundary of its service area, the speaker The clarity of the voice output from the 26 may deteriorate rapidly, resulting in a state where it becomes impossible to make a call, and if you continue to make a call after that, it is necessary to There was a problem in that it was difficult to continue the call smoothly because procedures such as switching to another base station were required to continue the call.

[0015] This invention has been made to solve the above-mentioned problems, and it is possible to carry out procedures for continuing a call, such as switching to a base station in an adjacent service area, before the call becomes impossible. The purpose of the present invention is to obtain a mobile communication system that allows smooth continuation of telephone calls.

[0016]

[Means for Solving the Problems] A mobile communication system according to the present invention includes a specific code detection circuit that detects the degree of error in a predetermined specific code in a transmission signal sent from a transmitter of a base station. and an indicator that displays an alarm to notify the operator when it is detected that the degree of error in the specific code exceeds a predetermined reference value, to the receiver of the mobile station. It was established.

[0017]

[Operation] The specific signal detection circuit of the present invention detects a predetermined specific signal in a transmission signal sent out by a transmitter of a base station, and detects a predetermined degree of error in the specific code. If it is detected that the standard value has been exceeded, a warning will be displayed on the display to notify the operator before the clarity of the call deteriorates significantly, allowing the operator to continue the call before the call becomes impossible. To realize a mobile communication system capable of smoothly continuing a call by taking necessary measures.

[0018]

[Example] Example 1. An embodiment of the present invention will be described below with reference to the drawings. Figure 1
, 1 is a base station transmitter, 2 is a mobile station receiver,
11 is a microphone, 12 is an A/D encoder, 13 is a synchronization signal generation circuit, 14 is a synthesis circuit, 15 is an oscillator, 16 is a modulator, 17 is a high frequency amplifier, 18 is a transmitting antenna, 2
1 is a receiving antenna, 22 is a receiving circuit, 23 is a separation circuit,
24 is a synchronizing signal detection circuit, 25 is a D/A decoder, and 26 is a speaker, which are the same or equivalent parts to those of the conventional device denoted by the same reference numerals in FIG. 4, and therefore detailed description thereof will be omitted.

In the transmitter 1 of the base station, a synchronous signal 19 is generated by the synchronous signal generating circuit 13, and an A/D
This is a specific signal generating circuit that generates a specific signal to be combined with the digitally encoded signal in the encoder 12 and sends it to the combining circuit 14.

[0020] Furthermore, in the receiver 2 of the mobile station, 27
is a specific code detection circuit that detects the specific code from the digital signal received and demodulated by the receiving circuit 22, and detects that the bit error of the specific code exceeds a predetermined reference value.

[0021] Reference numeral 28 serves as an indicator that acoustically displays a warning to the operator when the specific code detection circuit 27 detects that the bit error of the specific signal exceeds a predetermined reference value. It is a functional sounding body such as a buzzer. Reference numeral 29 denotes a light emitting body such as a light emitting diode, which functions as an indicator for visually displaying the alarm.

Next, the operation will be explained. In the transmitter 1 of the base station, the A/D encoder 12 digitizes the audio input from the microphone 11 and inputs it to the synthesis circuit 14, as in the conventional case. The synthesis circuit 14 synthesizes the digitized signal with a synchronization signal generated by the synchronization signal generation circuit 13 and a specific signal generated by the specific signal generation circuit 19.

FIG. 2 is an explanatory diagram showing the structure of the signal output from the synthesis circuit 14. As shown in the figure, the specific signal is inserted at the end of a series of signals separated by synchronization signals and combined. A signal obtained by combining the synchronization signal and the specific signal with the digitized signal is sent from the combining circuit 14 to the modulator 16.

Hereinafter, as in the conventional case, the modulator 16 modulates the carrier wave oscillated by the oscillator 15 with the received signal, and the signal modulated by the modulator 16 is sent to the high frequency amplifier 17.
After being amplified to a predetermined level, the signal is radiated into space from the transmitting antenna 19.

Furthermore, in the receiver 2 of the mobile station, the signal received by the receiving antenna 21 is sent to the receiving circuit 22 for amplification and demodulation, as in the conventional case, and the signal is received and demodulated by the receiving circuit 22. The digital signal is sent to a separation circuit 23, a synchronization signal detection circuit 24, and a specific signal detection circuit 27.

The separation circuit 23 separates the synchronization signal and the specific signal from the input digital signal, extracts the digitally encoded audio signal, sends it to the D/A decoder 25, and converts it into an analog signal. It is decoded and output as audio from the speaker 26.

On the other hand, the specific signal detection circuit 27 that receives the digital signal amplified and demodulated by the receiving circuit 22 detects the specific code synthesized by the synthesizing circuit 14 of the transmitter 1 from among the digital signals. Then, a bit error of the particular code is detected and compared with a predetermined reference value, and when it is detected that the bit error exceeds the reference value, a signal is sent to the sounding body 28 and the light emitting body 29.

When the sounding body 28 receives the signal from the specific code detection circuit 27, it sounds and displays an acoustic warning to the operator. Further, the light emitting body 29 is the specific signal detection circuit 2
It emits light in response to a signal from 7 and visually displays a warning to the operator. Here, the case where this alarm display is performed acoustically and visually has been shown, but it is also possible to display only one of them.

[0029] The operator notices that the bit errors in the digital signal being received have deteriorated by the sounding of the sounding body 28 and the warning display caused by the light emission of the light-emitting body 29, and switches to a base station in an adjacent service area. Take the following steps to continue the call before it becomes impossible to make a call.

Example 2. In the above embodiment, a case has been described in which the specific signal is generated from a separately provided specific signal generation circuit, but a parity code may be used as the specific signal. FIG. 3 is an explanatory diagram showing the structure of a signal output from the synthesis circuit 14 in such an embodiment.

In this case, as shown, a parity code is inserted at the position where the specific signal was inserted in FIG. This parity code is set by counting the number of "1"s and "0"s in a digital signal separated by a synchronization signal so that the total number of "1s" is an even number (or an odd number).

[0032] The specific signal detection circuit 27 of the receiver 2 counts the number of "1"s in the digital signal separated by the synchronization signal, and determines whether the number is an even number (or an odd number) specified by the transmitter 1 side. bit errors in the digital signal are detected.

Example. 3 In addition to the above-mentioned specific signals, it is also possible to use, for example, a synchronization signal. That is, the synchronization signal may be regarded as a specific signal, and the degree to which it is erroneously detected may be detected by the specific signal detection circuit 27, and the same effect as in the above embodiment can be achieved.

[0034]

[Effects of the Invention] As described above, according to the present invention, a predetermined specific signal in a transmission signal sent out by a base station transmitter is detected, and the degree of error in the specific code is determined in advance. If it is detected that a predetermined standard value has been exceeded, the system is configured to display a warning, so the user can take steps to continue the call, such as switching to a base station in an adjacent service area, before the call becomes impossible. This has the effect of providing a mobile communication system in which calls can be continued smoothly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a mobile communication system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the structure of a signal output from the combining circuit.

FIG. 3 is an explanatory diagram showing the structure of a signal output from a synthesis circuit according to another embodiment of the invention.

FIG. 4 is a block diagram showing a conventional mobile communication system.

FIG. 5 is an explanatory diagram showing the configuration of a signal output from the synthesis circuit.

FIG. 6 is a characteristic diagram showing the relationship between the distance between a transmitter and a receiver, bit errors, and intelligibility.

[Explanation of symbols]

1 Transmitter 2 Receiver 27 Specific signal detection circuit 28 Display device (sounding body) 29 Indicator (luminous body) In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] Claim 1: A mobile station moving within a service area formed by a base station is connected to the previous base station by radio using a digital modulation method, and the mobile station is connected to the base station via a line connected to the base station. In a mobile communication system that is in communication with a partner device, the receiver of the mobile station detects a predetermined specific code in a transmission signal sent by the transmitter of the base station, and detects that the specific code is incorrect. a specific code detection circuit that detects that the degree to which the specific code is received in error exceeds a predetermined reference value; and the specific code detection circuit detects that the degree to which the specific code is received in error exceeds a predetermined reference value. A mobile communication system characterized by being provided with a display that displays a warning to an operator when it is detected that the limit has been exceeded.