JPH0326029A - Radio communication system - Google Patents

Abstract

PURPOSE:To prevent a malfunction due to the reception of a data communication signal or the like as a control signal by separating a voice data communication signal and the control signal. CONSTITUTION:In the case of sending a control signal from a radio terminal equipment 101, a radio terminal equipment controller 119 switches a MODEM microphone changeover switch 123 to the position of a base station control MODEM 120, an identification signal is sent from an identification signal oscillator 121 and the output of the control signal is informed to the base station and then the control signal is sent. On the other hand, when an identification signal detector 122 detects an identification signal in signals sent from the base station side, the radio terminal equipment controller 119 turns off a voice output switch 124 to prevent a control signal from being outputted to a speaker 126 and to start the monitor of the reception output of a counter base station control MODEM 120, thereby preparing the arrival of the control signal. Thus, the malfunction caused by confusing a data communication signal from the control signal is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wireless communication system, and is particularly applicable to car telephones, cordless telephones used in premises such as buildings, and mobile radio systems expanded from the same. The present invention relates to a wireless communication system.

[Prior Art] Multi-channel systems are used in car phones, cordless phones, and extended premises wireless communication systems from the standpoint of radio frequency utilization efficiency. In this method, instead of assigning a fixed radio frequency to each wireless terminal, the radio frequency (channel) to be used is set each time a call occurs.

Therefore, a lot of information is exchanged between the base station and the wireless terminal, such as the radio frequency used (communication channel), call origination and call reception. This information for controlling the S line is called a control signal. Control signal transmission generally uses a digital signal transmission method using subcarriers.

In this method, the digital signal is transmitted by a modem at 0.3 to 3KH.
z Convert to a signal within the voice band and transmit it in the same way as voice. This is discussed in Jidoken (1980), published by the Institute of Electronics and Communication Engineers, supervised by Kuwahara, pages 45 to 56.

[Problem to be Solved by the Invention] In the above-mentioned conventional technology, in order to prevent malfunctions in radio line control caused by confusion between voice signals and control signals on the receiving side, the transmitting side specifies a specific signal at the beginning of the control signal. A bit bang signal (synchronization signal) was sent to the receiver, and the receiving side detected the bit pattern.

In addition, although analog voice communication has been the main focus of conventional wireless communication and telephone communication, future wireless communication will include digital information communication (hereinafter referred to as data communication) such as fax and PC communication, telephone reservations, and non-lingual voice communication. It is important to be able to perform a variety of communications such as PB signals (push buttons) for services, etc. Since all of these forms of communication utilize signals within the voice band, for example, in data communications, a modem is used to convert digital signals into signals within the voice band for communication. However, since the data communication signal has a signal form similar to that of the control signal, the probability that the bit bang included in the synchronization signal matches the data signal is
It is higher than that of audio signals, etc. Therefore, when handling data communication signals in addition to voice signals in wireless communication, there is a problem that the receiving communication station may erroneously operate the wireless line control due to confusion between control signals and data signals. An object of the present invention is to provide a wireless communication system that does not cause malfunctions on the receiving side in a wireless communication system that uses the voice band to transmit and receive signals other than voice (data communication signals). [Means for Solving the Problems] In order to achieve the above object, an identification signal having a frequency outside the voice band is transmitted in advance before wireless communication of the present invention, and the receiving wireless communication station uses the identification signal to The reception mode can now be selected accordingly.

Specifically, it is used to indicate whether a data communication signal is being transmitted (hereinafter referred to as a call state) or a control signal is being transmitted to each wireless terminal or base station. means for generating an identification signal having a frequency of
A means for detecting an identification signal transmitted from another communication station is provided, so that the transmitting wireless terminal or base station transmits the identification signal before transmitting the control signal. ．． On the receiving side, when this identification signal is detected, a demodulation circuit for radio line control is operated to read the received signal as a control signal.

Furthermore, the time from when the identification signal is sent until the detection means inside each communication station detects the identification signal becomes longer as a lower frequency is used as the identification signal.

Therefore, especially when using an identification signal with a frequency lower than the voice band, the identification signal must be transmitted for a long time before the control signal, and it takes time to exchange the III control signal. ．． To prevent this, the transmitting side sends out an identification signal with a frequency lower than the voice band at the same time as the control signal or a little before the control signal, and the receiving side always operates the demodulation circuit and stores its output data in the storage circuit. When the identification signal is detected, the output data stored in the storage circuit for a certain period of time before the identification signal is regarded as a control signal and decoded.

In addition, as a method of storing output data in the above memory circuit,
By using the ring buffer method, storage space can be saved. In that case, the capacity of the ring buffer is at least equivalent to the amount of data received during the delay time of the identification signal.

[Effect]

As mentioned above, by identifying the control signal exit period and the call period using an identification signal with a frequency outside the voice band, it is possible to prevent malfunctions on the receiving side due to confusion between voice, data communication signals, etc. and the control μ signal. can be prevented.

Furthermore, by temporarily storing the output data of the demodulation circuit in the storage circuit, it is possible to prevent loss of control signals and prolongation of the time it takes to retrieve control signals due to delays in the detection time of identification signals. By using a ring buffer method as the storage method, storage space can be saved. [Embodiment] FIG. 1 is a block diagram showing the structure of an embodiment of a mobile radio telephone system to which the present invention is applied. In the same figure, an electronic exchange 401 (hereinafter abbreviated as PBX) includes a wire line, an
Multiple base stations 201 via l301, 302, 303
, 202, 203. It is assumed that each of the mobile wireless terminals 101, 102, and 103 communicates with a base station via a wireless line. The system uses two frequencies: one from the base station to the wireless terminal (downlink) and the other from the wireless terminal to the base station (uplink) for simultaneous two-way communication. In addition, a multi-channel system is used to effectively utilize radio frequencies. In other words, a specific radio frequency is not assigned to each base station or each wireless terminal, but an empty communication channel is appropriately selected from among multiple radio frequencies for calls (hereinafter referred to as call channels) and used for calls. Specific control radio frequencies (hereinafter referred to as control channels) are determined for uplink and downlink respectively, and control signals such as frequency settings for use and incoming and outgoing calls are exchanged. Base stations and wireless terminals that are not making calls always receive this control channel. FIG. 2 shows an example of the exchange of control signals when a call is generated from a wireless terminal. A call signal is sent from the wireless terminal to the base station, and the base station sends a call response signal specifying the communication channel to the wireless terminal. The exchange of control signals up to this point is performed on the control channel, and thereafter is performed on the communication channel. After switching the radio frequency to the communication channel, the voice line is opened to the user and it is possible to exchange voice and data communication signals, etc.
Control signals are also exchanged between the wireless terminal and the base station, and the types include an interference detection completion signal, an audio-on signal, an off-book signal, a dial (AT number, etc.).

These control signals include several bytes of synchronization signals, as shown in Figure 3. Since the radio terminal or base station on the receiving side monitors the bit string of the synchronization signal, it can identify whether the received signal is the above-mentioned control signal, an audio signal, noise, or the like. In addition, "" included in the control signal in the same figure
The "command" includes command data indicating, for example, whether this control signal is a voice-on signal or a dialing signal, and the "parameter" includes, for example, a telephone number if this control signal is a dialing signal.

However, when using such a system to perform data communication in addition to phone calls, the probability that the bit string included in the data communication signal coincidentally matches the bit string of the synchronization signal of the control signal is higher than that of voice signals, etc. This poses a problem in that the receiving terminal may malfunction due to confusion between data communication signals and control signals exchanged on the same communication channel. In order to solve this problem, the present invention identifies the control signal sending period and the call period based on the presence or absence of an identification signal outside the audio frequency band.

To achieve this, the wireless terminal of this system has the configuration shown in Figure 4. The solid line shows the flow of signals, and the dashed line shows the flow of control from the controller. Further, in the same figure, the wireless terminal 101 has an acoustic coupler 501 and a modem 5.
02 to the computer 503 for data communication. In FIG. 4, 111 is a transmitting/receiving antenna, and 112 is a duplexer for separating transmitted waves and received waves. The audio signal input from the 125 microphone is 114F.
The audio frequency is FM modulated by the M modulator, and 1 unit is 5 Tx.
It is converted to a radio frequency by a transmitting amplifier, amplified, and 112
Sent to dubrexa. On the other hand, the received wave separated in the 112 duplexer is amplified and radio frequency selected in the 117RX receiving amplifier, and the 116F
It is demodulated in the M demodulator and becomes a voice. Also. The FM demodulator 1 and 6 includes a speaker 126 and a modem for controlling the base station]. ．． A built-in filter for cutting frequencies outside the audio band is included to prevent identification signals from leaking to the output to the 20 side. A frequency synthesizer 113 generates a fundamental wave for selecting the number of receiving and transmitting radio station waves according to data from the radio terminal controller 119. 118 is an envelope detector that detects the strength of the received wave, and the result is sent to the wireless terminal controller 119. 120 is a control modem for the base station, which converts (modulates) the digital control signal sent from the wireless terminal controller 119 to the base station into a subcarrier modulation signal within the voice band, and also converts the digital control signal sent from the base station converts the subcarrier modulation signal into a digital signal,
119 wireless terminal controller. 12
3 is a microphone/modem input selector switch, and during the control signal sending period, the output from the base station control modem is switched to FM.
It is connected to the modulator 114, and has the role of connecting the output from the microphone 125 during the call period. Reference numeral 124 denotes an audio output switch, which functions to cut off the control signal from entering the speaker 126 during the control signal transmission period. In FIG. 4, the microphone/modem input selector switch 123 is on the microphone side, and is in a state where audio is sent from the wireless terminal 101. Furthermore, the audio output switch 124 is shown in a state in which the connection to the speaker 126 is disconnected, and a state in which it is receiving a signal from the base station side as a control signal. 127 is a keypad for inputting phone numbers of other wireless terminals, etc.
Used for control of 01. When transmitting a control signal from the wireless terminal 101 side, the wireless terminal controller 119 executes a control signal transmission subroutine 601 shown in FIG. 5(a). Switch the modem/mic switch 123 to the modem side (611),
The identification signal is sent from the identification signal oscillator 121 (612)
．． Inform the base station 201 that a control signal will be issued,
After the delay time of the receiving side detector (6 1 3), the control signal is sent (614). Finally, stop the identification signal (61
5) Switch the modem/mic selector switch 123 to the microphone side. On the other hand, when the identification signal detector 122 detects an identification signal from among the signals sent from the base station 201 side, the identification signal detector 22 interrupts the wireless terminal controller 119. The wireless terminal controller 119 executes the control signal reception subroutine shown in FIG. 5(b) in response to this interruption. The audio output switch 124 is turned off (621) to prevent the control signal from being output to the speaker 126 side, and monitoring of the reception output of the base station control modem 120 is started (622). Prepare for the arrival of control signals. A synchronization signal is detected from the received output of the base station control modem 120 (623), followed by command/parameter input (624), command decoding/execution (6 2 5)
). Finally, turn on the audio output switch 124 (
6 2 6) and end. This prevents malfunctions caused by confusing data communication signals and control signals. Figures 6 and 6 show an example of the structure of the base station 201 according to the present invention. In the figure, 211 is a transmitting and receiving antenna;
212 is a duplexer for separating transmitted waves and received waves, 213 is a frequency synthesizer, 214 is an FM modulator, 2/5 is a transmitting amplifier, 216 is an FM demodulator, 2/7 is a receiving amplifier, 218 is an envelope detection 219 is a base station controller, 220 is a wireless terminal control modem, 221
222 is an identification signal oscillator, 222 is an identification signal detector, 223 is a changeover switch for the communication voice from the telephone line/wireless terminal control modem output, and 224 is a received voice output switch.
Its operation is similar to that of a wireless terminal. However, there is no microphone, speaker, or keypad, and a circuit for connection to the electronic exchange 401 is installed. i! Child exchange 40
The signal from the base station side is separated from the voice signal from the base station side by a hybrid through the telephone line, $lI 301, and sent to the FM modulator 214. Also, the audio signal from the FM demodulator is transmitted to the hybrid 230, l! The data is sent to the electronic exchange 401 through the telephone line 301. The basic operation and structure of a base station is the same as that of a wireless terminal, but the method of the present invention is also used in the wired line between the base station and PBX, and the base station has a connection to the PBX! ill control modem 225, to PBX
A signal oscillator 226 for Ilt and a signal detector 227 for PBXIa are built-in. The figure shows a case where a control signal is sent from the wireless terminal 101 side, and the received audio output switch 224 is turned off. FIG. 7 shows an example of frequencies used for identification signals.

300 Hz as the band for voice and data communication signals
Figure 7(a) shows a case in which the identification signal is placed at a frequency below 3KHz, and Figure 7(b) shows a case in which the identification signal is placed at a frequency higher than that. Although the same effect can be obtained in either case, detection of the identification signal takes less time if a frequency above the voice band is used.

On the other hand, if FM modulation is used as a radio frequency modulation method,
The more high frequencies are included, the wider the occupied radio frequency band becomes, so in terms of narrowing the occupied band, it is more advantageous to use a frequency below the voice band as an identification signal. Become. In this example, a single frequency signal was used as the identification signal, but the same effect can be obtained by combining multiple frequencies. FIG. 8(a) shows an example of the time relationship of identification signal transmission. The figure shows the output of the call signal (voice/data communication signal), control signal, a-specific signal, and identification signal detector. In the figure, the transmitting side sends out an identification signal prior to sending out the control signal, and the receiving side detects this identification signal, and the receiving side detects the identification signal as shown in Fig. 5(b).
Executes the control signal reception subroutine. However, 'I
There is a time delay td in detecting the li-specific signal, and the lower the frequency used as the identification signal, the longer the time required. For this reason, for example, when using a frequency below the audio band of about 300Hz to 3KHz as an identification signal,
The delay time td is several 100 msec, which means that it takes a long time to exchange control signals. In the present invention, in order to prevent this, a storage circuit for temporarily storing the output of the receiving side demodulator is provided in the terminal, etc.
After detecting the lt-specific signal, the contents corresponding to the detection delay time are read out from the memory circuit and decoded. This is shown in Figure 8(b). Here, the memory circuit requires a buffer large enough to store the data sent during the time difference tm between the output of the control signal and the identification signal. The output from the modem is written to the buffer by interrupts at regular intervals, and old contents are sequentially rewritten with new contents. FIG. 9 shows a control signal reception subroutine 60 in this method.
3 is shown. This subroutine is executed by an interrupt from the output of the identification signal detector, turns off the first audio output switch (631), and sets a pointer indicating the position from which data is to be read from the buffer at the beginning of the buffer (
632). Next, a synchronization signal is detected from the buffer contents (6
33). Enter command parameters (634). If the command parameters are not completely stored in the buffer, reception continues and the command is then decoded and executed (635).

Since microprocessors with small storage capacity and processing power are used for this purpose, it is necessary to adopt a buffer method that is compatible with this. Adopting a ring buffer method as a buffer in the memory circuit saves memory and shortens execution time. The ring buffer has a ring shape as shown in FIG. 10(a), and every time new data is written, old data is erased. The pointer indicates the position to write this new data, and it moves one by one each time data is written. Since the actual memory circuit is not ring-shaped as shown in Figure 1O(b), the tail of the buffer area is connected before the head of the buffer area in software. By doing this, the oldest data is sequentially erased, while a certain amount of the latest data is stored, and is sent at the difference tm between the start time of the control signal and the identification signal detection time delay. All you need is a buffer large enough to store the data, and there is no need to prepare an unnecessarily large buffer. It is suitable for implementation on a small microprocessor. [Effects of the Invention] As described above, according to the present invention, voice/data communication signals and control signals can be separated in a wireless communication device, and malfunctions caused by receiving data communication signals etc. as control signals can be avoided. can be prevented. Furthermore, by storing the output of the demodulator (modem) in a ring buffer, it is possible to prevent the exchange of control signals from becoming prolonged due to the detection time delay of the identification signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the configuration of a communication system according to the present invention, FIG. 2 is a flow diagram showing an embodiment of control of a base station/wireless terminal at the time of call origination, and FIG. FIG. 4 is a block diagram showing an example of the configuration of a wireless terminal device, FIG. 5jlfi is a flowchart showing the control signal transmission and reception subroutine, and FIG. FIG. 7 is a block diagram showing an example of the usage band of the identification signal; FIG. 8 is a diagram showing an example of the time relationship between the identification signal, the control signal, and the identification signal. , FIG. 9 is a flowchart showing the reception subroutine when control signals are temporarily stored, and FIG. 10 is a diagram showing the structure of the ring buffer. 10-127...Wireless terminal, 201-230...
Base station, 301-303...Telephone line. 401 mountain exchanger, 501-503... computer system for data communication, 601-603... program flow chart. ) Abuse Zu Kuzu Z Figure No. 5 En (Jou 2 Kuzu 5 Figure (b) Fu 7 times (a-fu Cb) Fu 6 Figure (E) τi (b) U 9 Nagi 10 Figure (Arai no] f Teno θ Figure (.b)

Claims (1)

[Claims] 1. In a wireless communication system in which control signals for wireless line control or voice and data signals are transmitted and received between two wireless communication stations using a voice band, the wireless communication station on the transmitting side is Wireless communication characterized in that before transmitting the control signal, an identification signal having a frequency outside the audio band is transmitted in advance, and the receiving side wireless communication station selects a reception mode according to the identification signal. method. 2. In a wireless communication system in which control signals for wireless line control or voice and data signals are transmitted and received between two wireless communication stations using a voice band, each wireless communication station:
The radio communication station includes means for transmitting an identification signal having a frequency outside the audio band and means for detecting the identification signal, and the transmitting wireless communication station transmits the identification signal in advance before transmitting the control signal, and receives the identification signal. A wireless communication system characterized in that a side wireless communication station selects a reception mode according to the identification signal. 3. The receiving wireless communication station has a first receiving mode in which the received signal from the transmitting communication station is received as the control signal, and a second receiving mode in which the received signal is received as a voice or data signal. and the first reception mode is selected while the identification signal is being detected, and the second reception mode is selected when the identification signal is not detected. The wireless communication method described in Items 1 and 2. 4. The radio communication station on the receiving side includes storage means for storing the received signal from the transmitting communication station for a predetermined period, and after detecting the identification signal, the received signal stored in the storage means 4. The wireless communication system according to claim 1, wherein the control signal is read out as the control signal. 5. The storage means includes a plurality of buffer areas, and the receiving side wireless communication station stores the received signal in a buffer area indicated by a pointer that sequentially moves between each buffer area. The wireless communication system according to claim 4, characterized in that: