JP2008252329A - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably generate a transmission frequency regardless of a temperature change or a secular change by receiving the transmission frequency from a base station even in a mobile wireless device capable of communication by two modes of performing the communication through the base station and the communication with another mobile wireless device directly without interposing the base station. <P>SOLUTION: In the wireless communication system wherein the mobile wireless device has two communication modes of performing the communication by a frequency for base station communication with the base station when it is in the area of the base station and performing the communication by a frequency for direct communication with another mobile wireless device when it is out of the area of the base station, the base station transmits the frequency for the base station communication and the frequency for the direct communication at a prescribed interval, data indicating that it is transmission from the base station are included in transmission data by the frequency for the direct communication, and the mobile wireless device corrects the oscillation frequency of the mobile wireless device on the basis of the radio frequency in the case of receiving the frequency for the direct communication including the data indicating that it is transmitted from the base station. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a wireless communication system, and in particular, includes a mobile wireless device capable of communication in two modes in which communication is performed via a base station and communication with another mobile wireless device is performed directly without going through the base station. This mobile radio apparatus relates to a radio communication system that stably oscillates a frequency regardless of secular change of a transmitter.

As a conventional wireless communication system, for example, a wireless device of a commercial wireless communication system includes a wireless device of a type having two modes of communication via a base station and direct communication between mobile stations. is there.
For example, according to the ARIB (Association of Radio Industries and Businesses) standard established by the Radio Industries Association of Japan, “ARIB STD-T79: Prefectural / Municipal Digital Mobile Communication System” or “ARIB STD-T81: Specified Low Power Radio” It is a radio designed to operate according to standards such as “2.4 GHz band mobile radio equipment using a frequency hopping system”.

In such a wireless device, when receiving radio waves from the base station, communication is performed at the transmission frequency obtained by adjusting the frequency deviation based on the low-accuracy received frequency transmitted from the base station. ing.
On the other hand, when communicating with other mobile wireless devices, communication is performed using a transmission frequency generated based on a reference signal that the mobile wireless device has.

By the way, the frequency deviation of the reference signal which it has changes by various influences.
The main two are as follows.
(1) Temperature characteristics of the crystal oscillator that generates the reference signal that is the original oscillation (2) Aging characteristics of the crystal oscillator that generates the reference signal that is the original oscillation are the temperature characteristics of the environment in which the radio is used It changes with.
As a countermeasure, a circuit for finely adjusting the frequency deviation according to the environmental temperature is incorporated in the crystal oscillation circuit to reduce the fluctuation of the frequency deviation.

In addition, the oscillation frequency of the quartz crystal changes with time. However, for example, a change of about 0.2 pm per year occurs.

The following Patent Document 1 discloses a technique for correcting the oscillation frequency in accordance with such aging and environmental temperature.

JP 2002-305442 A

In the wireless device as described above, when communicating via the base station, the oscillation frequency can be adjusted based on the reception frequency. However, when direct communication is performed between mobile wireless devices, it becomes a frequency reference. Since frequency correction cannot be performed following the signal, there is a possibility that the frequency deviation may increase due to temperature change or aging change during use.

The present invention has been made in view of such a conventional situation, and communication is possible in two modes in which communication is performed via a base station and communication is performed directly with another mobile radio without using the base station. It is possible to provide a wireless communication system that can stably generate a transmission frequency even if it is a mobile radio by receiving a transmission frequency from a base station, regardless of a change in temperature or aging. Objective.

An invention for solving the above-mentioned conventional problems is a wireless communication system comprising at least one base station and a plurality of mobile radios, wherein the mobile radios are within the range of the base station Communicates with the base station at the base station communication frequency, and when out of the base station, the wireless communication has two communication modes for communicating with other mobile radio devices at the direct communication frequency. In the system, the base station transmits a base station communication frequency and a direct communication frequency at a predetermined interval, and transmission data at the direct communication frequency is transmitted from the base station. When the mobile radio includes a data for direct communication including data indicating that the mobile radio is transmitted from the base station, the mobile radio corrects the oscillation frequency of the mobile radio based on the radio frequency. Characteristic To.

An invention for solving the above-mentioned conventional problems is a wireless communication system comprising at least one base station and a plurality of mobile radios, wherein the mobile radios are within the range of the base station Communicates with the base station at the base station communication frequency, and when outside the base station range, the SCPC digital having two communication modes for communicating with other mobile radio devices at the direct communication frequency. In the wireless communication system of the system, the base station transmits a base station communication frequency and a direct communication frequency at predetermined intervals, and transmission data from the base station is transmitted to the transmission data at the direct communication frequency. The mobile wireless device corrects the oscillation frequency based on a temperature sensor provided in the mobile wireless device, and further includes data transmitted from the base station. When receiving a contact communication frequency, and correcting the oscillation frequency due to aging of the mobile radio based on the radio frequency.

According to the present invention, even a mobile wireless device capable of communication in two modes in which communication is performed through a base station and communication directly with another mobile wireless device without going through the base station can be performed from the base station. By receiving the transmission frequency, it is possible to provide a wireless communication system that can stably generate the transmission frequency regardless of temperature change or aging.

Embodiments according to the present invention will be described with reference to the drawings.
FIG. 2 shows a configuration example of a radio communication system according to the embodiment of the present invention.
FIG. 2 shows an example of an SCPC digital radio system, where 1 is a mobile terminal and 10 is a control station. The control station 10 has a plurality of base stations 14 and each having a line control function. It is connected to the mobile terminal and connected to the public network.
The base station normally transmits to the mobile terminal 1 existing in the radio paging area in the frequency band of F1 and uses this as the frequency for base station communication.
For simplicity, only one base station 1 is shown in the figure.

The mobile terminal 1 normally receives the base station communication frequency F1 and, when making a call, transmits to the base station at the transmission frequency F1 and establishes communication with other mobile terminals and higher-order sides. .
However, for example, when the mobile terminal 1 exists outside the radio call area of the base station, the mobile terminal 1 ′ cannot receive the base station communication frequency F1, and therefore, with another mobile terminal 1 (or mobile terminal 1 ′). Is switched to a mode in which transmission / reception is performed at a direct communication frequency F2 (a predetermined frequency band different from F1).
On the other hand, the mobile terminal 1 waits for a call at the frequency F2 at a predetermined interval in order to confirm whether or not there is a call for communication at the frequency F2 while receiving the normal frequency F1.
When there is a call at the frequency F2, the mode is switched to the direct communication mode and the communication at the frequency F2 is performed.

The above-described mobile terminal 1 is in a mode that uses the frequency F2 (that is, the frequency for direct communication) in response to the call of the mobile terminal 1 ′. it can.
In this case, the base station communication frequency F1 cannot be received unless the operator performs an operation for switching to the mode for performing base station communication (that is, the base station communication frequency F1).

Therefore, the control station 10 stores the data of the direct communication frequency F2 and the data of the base station communication frequency F1 used by the mobile terminal 1 or the mobile terminal 1 ′, and at predetermined intervals. Transmit frequencies F1 and F2.
FIG. 4 shows an example of the transmission timing of the base station according to the embodiment of the present invention.
As a transmission frequency from the base station, for example, transmission at the frequency F1 is performed every several tens of seconds to several tens of minutes, and once every several times of this repeated transmission (once in four times in the figure), at the frequency F2. Is to be transmitted.
At the time of transmission at the frequency F2, the transmission data format includes data indicating that it has been transmitted from the base station.
When the mobile radio apparatus receiving at the frequency F2 is a direct communication frequency transmitted from the base station, the mobile radio apparatus corrects the oscillation frequency inside the mobile radio apparatus based on the frequency F2 from the base station. It is. Details will be described later.

FIG. 1 shows a configuration example of a mobile radio device of a radio communication system according to an embodiment of the present invention.
In the mobile radio device 1 (or 1 ′), a signal (frequency F1 or F2) from the base station received by the antenna 33 is input to the receiving unit 35 via the antenna duplexer 34.
Then, after high frequency amplification by the high frequency amplifier 36 of the reception unit 35, the frequency is converted by the local transmission signal from the frequency synthesizer 40 in the reception mixer 37 and demodulated by the demodulator 39 via the intermediate frequency amplifier 38.
The demodulated reception signal for the own station (that is, the output of the demodulator 39) is signal-processed by the reception signal processing circuit 42 of the baseband signal processing unit 41 and output to the receiver 43 or displayed via the control unit 4. Is output to the unit 56.

On the other hand, the voice signal from the transmitter 44 or the input data from the control unit 4 is subjected to signal processing in the transmission signal processing circuit 45 and then input to the transmission unit 46.
That is, the output signal of the transmission signal processing circuit 45 is subjected to predetermined modulation processing by the modulator 47, and then converted to a high frequency signal by the transmission mixer 48 to which the signal from the frequency synthesizer 40 is supplied. Then, the power is amplified and transmitted from the antenna 33 through the antenna duplexer 34.

In the control unit 4, 50 is a main central processing unit (main CPU) that controls the entire mobile radio device 1 (or 1 ′), 51 is a ROM that stores control programs, predetermined constants, and the like, and 52 is a work area. RAM 53 used as an electrical erasable and writable ROM such as a flash memory for storing various parameters and tables, data input from the input key 55 and the display unit 56, and data output to the display unit 56 The operation unit 54 is configured by a radio power control unit 58 that controls the power of the radio, and a connection bus 59 thereof.

The control unit 4 detects the difference between the reception frequency of the reception signal processing circuit 42 and the oscillation frequency of the frequency synthesizer 40, and compares the correction data based on the detected difference with the frequency data in the electrically erasable / writable ROM 53. Then, the calculated correction data is given to the D / A section 31, and the oscillation frequency is corrected by varying the control voltage of the VC-TCXO 32 based on this correction data.
The frequency data in the electrically erasable and writable ROM 53 is stored so as to update the correction data based on the direct communication frequency F2, and the mobile radio is transmitted from the base station and directly. When the communication frequency (frequency F2) is received, the frequency data output from the VC-TCXO 32 is corrected based on the frequency F2.
The ROM 51 or RAM 52 is provided with a table of frequency correction data according to temperature changes, and the frequency correction data is always sent to the D / A 31 according to the temperature detected by a temperature sensor (not shown). ing.

FIG. 3 shows an example of an operation flowchart of the mobile radio in the radio communication system according to the embodiment of the present invention.
When the operation of the mobile terminal is started, first, radio waves from the base station are received at a predetermined communication frequency (regular time in the figure) at a direct communication frequency.
It is determined whether or not the received reception frequency is deviated from a predetermined frequency range.
If it deviates from a predetermined frequency range, the frequency deviation is stored in an electrically erasable ROM.
After storing the frequency deviation, the VC-TCXO oscillation frequency is controlled by the new frequency data.
On the other hand, if the reception frequency does not deviate from the predetermined frequency range, the process returns to the state of waiting for radio wave reception from the base station at the direct communication frequency from the fixed time.
With such an operation, the frequency can be accurately matched with the frequency for direct communication from the base station.

FIG. 5 shows a configuration example of a base station of the radio communication system according to the embodiment of the present invention.
The base station includes an F1 transmitter that transmits at a base station communication frequency F1, which is a normal transmission signal, an F2 transmitter that transmits at a direct communication frequency F2, a switching unit that switches between these, A receiving antenna that receives transmission from the radio, a receiving unit that uses the received signal as a predetermined demodulated signal, a storage unit, an interface unit, and a control unit that controls these units are configured.

The embodiment of the present invention solves the problem that the oscillation frequency fluctuates due to secular change in the direct communication mode of the mobile terminal, and thus the transmission frequency and the reception frequency of the mobile terminal shift and exceed the range of the usable frequency accuracy. For example, even if a mobile radio terminal has been in direct communication mode for a long time by operation, the oscillation frequency of the mobile radio terminal can be corrected, and the radio can be transmitted without the user being aware of it. It is possible to receive various services of the system.

As described above in detail, the conventional mobile terminal has a base station mode in which the mobile station communicates with the base station and a direct communication mode in which the mobile station and the mobile station communicate, and the synthesizer of the mobile station in the direct communication mode. The reference variable crystal oscillator used in the system oscillation circuit has its oscillation frequency fluctuated due to secular change.Therefore, in the process of using a mobile terminal, fluctuations in the transmission frequency and reception frequency are inevitable, and the range of frequency accuracy used. There was a possibility of getting out of place.
However, according to the present invention, in the direct communication mode of the mobile terminal, the oscillation frequency fluctuates due to secular change, and therefore, the transmission frequency and the reception frequency of the mobile terminal shift and exceed the range of the usable frequency accuracy. On the other hand, the base station periodically transmits the frequency used in the direct communication mode, not the frequency used in the base station mode, from the base station so that the correction mode on the mobile terminal side, that is, direct communication from the base station. The difference between the reception frequency and the oscillation frequency of the synthesizer oscillation circuit of the mobile station is detected, the correction data based on the detected difference is compared with the frequency data in the EEPROM, and the calculated correction data is This can be solved by varying the control voltage of the voltage variable crystal oscillator as a reference.

According to the present invention, for example, in a SCPC digital radio communication system, a radio terminal transmits a frequency of a frequency for direct communication from a base station, and a radio terminal that receives the frequency controls the synthesizer unit of the radio terminal, Even in the direct communication mode, a mobile radio terminal including a control unit that corrects the oscillation frequency can be provided.
In such a wireless communication system, the base station is a base station that transmits a frequency based on a frequency for direct communication between mobile stations in addition to a normal communication frequency.

Here, the configurations of the wireless communication system, the master station device, and the slave station device according to the present invention are not necessarily limited to those described above, and various configurations may be used.
The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various devices and systems.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
For example, the present invention can be applied not only to communication of voice information but also to communication of various information such as text and images.

In addition, as various processes performed in the wireless communication system, the master station device, and the slave station device according to the present invention, the processor is stored in a ROM (Read Only Memory) in a hardware resource including a processor, a memory, and the like, for example. A configuration controlled by executing the control program may be used, and for example, each functional unit for executing the processing may be configured as an independent hardware circuit.
Further, the present invention can be grasped as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, or the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

1 shows a configuration example of a mobile radio device of a radio communication system according to an embodiment of the present invention. 1 shows a configuration example of a wireless communication system according to an embodiment of the present invention. An example of the operation | movement flowchart of the mobile radio apparatus of the radio | wireless communications system which concerns on embodiment of this invention is shown. An example of the transmission timing of the base station according to the embodiment of the present invention is shown. The structural example of the base station of the radio | wireless communications system which concerns on embodiment of this invention is shown.

Explanation of symbols

1, 1 ′: mobile terminal, 4: control unit of mobile terminal, 10: control station, 14: base station,
31: D / A conversion unit, 32: VC-TCXO, 34: antenna sharing device, 35: reception unit, 40: frequency synthesizer, 41: baseband signal processing unit, 46: transmission unit.

Claims (2)

A wireless communication system comprising at least one base station and a plurality of mobile radios,
When the mobile radio is within range of the base station, the mobile radio communicates with the base station at a frequency for base station communication. When the mobile radio is out of the base station, the mobile radio is used for direct communication with another mobile radio. In a wireless communication system having two communication modes for performing communication at a frequency,
The base station transmits a base station communication frequency and a direct communication frequency at a predetermined interval,
And the transmission data at the frequency for direct communication includes data indicating transmission from a base station,
When the mobile radio receives a direct communication frequency including data indicating that the mobile radio is transmitted from the base station, the mobile radio corrects the oscillation frequency of the mobile radio based on the radio frequency. Communications system. A wireless communication system comprising at least one base station and a plurality of mobile radios,
When the mobile radio is within range of the base station, the mobile radio communicates with the base station at a frequency for base station communication. When the mobile radio is out of the base station, the mobile radio is used for direct communication with another mobile radio. In an SCPC digital wireless communication system having two communication modes for performing communication at a frequency,
The base station transmits a base station communication frequency and a direct communication frequency at a predetermined interval,
And the transmission data at the frequency for direct communication includes data indicating transmission from a base station,
The mobile radio performs an oscillation frequency correction based on a temperature sensor provided in the mobile radio,
Furthermore, when a direct communication frequency including data indicating that the base station has been transmitted is received, an oscillation frequency due to secular change of the mobile radio is corrected based on the radio frequency. Communications system.

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