JP2011035804A - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system capable of stably correcting frequency deviation in a one-wave simplex operation portable station wirelessly communicable only with a mobile station. <P>SOLUTION: A wireless communication system includes a mobile station which communicates with a base station according to a two-wave duplex operation scheme, and a portable station, which communicates with the mobile station according to a one-wave simplex operation scheme, at least one by one, and the mobile station is capable of correcting its own transmission/reception frequency with a transmission frequency from the base station as a criterion. In the wireless communication system, the mobile station includes a function for adding frequency corrected information to a signal to be transmitted by the mobile station itself and transmitting the signal in the case where the frequency correction is performed. Only in the case where the frequency corrected information is added to a received signal, the portable station corrects its own transmission/reception frequency with the received transmission frequency as a criterion. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless communication system capable of correcting a frequency deviation in a mobile station equipped with a single-wave simplex type wireless device capable of wireless communication only with a mobile station.

  In wireless communication performed between a base station, a mobile station, a mobile station, and the like, each wireless device uses a crystal oscillator as a reference signal source such as a PLL circuit that determines the frequency of a transmission / reception signal. This crystal oscillator has a characteristic that the oscillation frequency changes depending on the ambient temperature condition, and also has a characteristic that it changes over time.

  Of these changes in frequency, OCXO (Oven Controlled Xtal Oscillator) has already been proposed to prevent changes due to ambient temperature. OCXO is a crystal oscillator in which a temperature is kept constant by enclosing it in a thermostatic bath and exhibits a very stable frequency characteristic. However, since it is expensive and the entire apparatus becomes large, the mobile station It could not be used for mobile stations and was used exclusively at base stations.

  On the other hand, in mobile stations and mobile stations, VC-TCXO (Voltage Controlled Temperature Compensated Xtal Oscillator) that performs temperature compensation by controlling by voltage is adopted. Although this VC-TCXO is less stable than the OCXO, the VC-TCXO is used in mobile stations and mobile stations because it is inexpensive and small.

  The OCXO and VC-TCXO both change with time. In particular, in VC-TCXO, the frequency characteristics due to temperature change are not as stable as OCXO. If the frequency shift due to secular change is left unattended, it may not be possible to transmit at the specified frequency, and it is necessary to correct the frequency shift due to secular change. There is. Patent Documents 1 and 2 can be cited as examples of such a problem of frequency aging.

  The wireless communication system described in Patent Literature 1 is assumed to have a base station mode in which a mobile station communicates with a base station and a direct communication mode in which the mobile station and mobile station communicate with each other. In order to solve the problem that the reference variable crystal oscillator used in the PLL synthesizer oscillation circuit of the station fluctuates the oscillation frequency due to aging, the base station regularly communicates instead of the frequency used in the base station mode. By transmitting the frequency used in the mode, the correction mode on the mobile terminal side, that is, the frequency for direct communication from the base station is received, and the difference between the received frequency and the oscillation frequency of the PLL synthesizer oscillation circuit of the mobile station is calculated. Detect and compare the correction data based on the detected difference with the frequency data in the EEPROM and change the voltage based on the calculated correction data The control voltage of the crystal oscillator is obtained so as to variably.

The mobile communication frequency stabilization system described in Patent Document 2 averages frequency deviation for each communication in direct wireless communication between mobile stations in order to stabilize the transmission / reception frequency without always receiving radio waves from the base station. Thus, the frequency of transmission and reception is converged by reducing the deviation.
JP 2008-252329 A JP 2001-102992 A

  Incidentally, in addition to a base station and a mobile station that perform wireless communication with each other, there is a single-wave simplex mobile station that can perform wireless communication only with a mobile station. In the case of this mobile station, the transmission of the base station cannot be directly received regardless of the inside or outside of the base station area, and therefore the frequency deviation cannot be corrected based on the signal of the base station having a stable frequency. Although it is possible to correct the frequency deviation based on the signal of the mobile station, if the frequency deviation occurs in the mobile station, the same deviation occurs in the frequency of the mobile station.

  As in the wireless communication system described in Patent Document 1, it is conceivable that a signal for correcting a frequency deviation can be transmitted from the base station, but the function of transmitting to the base station at different frequencies in two bands. Therefore, there is a problem that the cost of the equipment is increased. Even if such a configuration is added, the frequency deviation of the mobile station existing outside the base station area cannot be corrected.

  Further, as in Patent Document 2, in the method of converging the frequency of transmission and reception by averaging the frequency deviation for each communication between mobile stations and reducing the deviation, it is identified which mobile station has the correct frequency. Since there is no method, there is a problem that when the averaging is performed between a mobile station having a large frequency deviation and a mobile station having an accurate frequency, a deviation occurs in the frequency of the accurate mobile station.

  The present invention has been made in view of the above problems, and provides a wireless communication system capable of stably correcting a frequency deviation in a single-wave simplex portable station capable of wireless communication only with a mobile station. It is the purpose.

  Claim 1 of the present invention comprises at least one mobile station that communicates with a base station using a two-wave duplex method, and one mobile station that communicates with the mobile station using a one-wave simplex method. Is a radio communication system capable of correcting the transmission / reception frequency of the own station with reference to the transmission frequency from the base station, and the mobile station adds frequency corrected information to the signal transmitted by the mobile station when the frequency correction is performed. The mobile station has a function of adding and transmitting, and the mobile station corrects the transmission / reception frequency of the mobile station based on the received transmission frequency only when frequency-corrected information is added to the received signal. A wireless communication system.

  Claim 2 of the present invention comprises, in addition to claim 1, the mobile station having a function of transmitting frequency corrected information added to a signal transmitted by the mobile station when frequency correction is performed. A wireless communication system is characterized.

  Claim 3 of the present invention, in addition to claim 1 or 2, has a function in which the mobile station and the mobile station store the date and time when the previous frequency was corrected. When the time elapses, the wireless communication system has a function of deleting and transmitting the frequency-corrected information.

  Claim 4 of the present invention, in addition to claim 1 or 2, the mobile station and the mobile station have a function of storing the temperature when the previous frequency was corrected, and corrected the previous frequency A wireless communication system comprising a function of deleting and transmitting frequency corrected information when a predetermined temperature change occurs from time.

  According to the first aspect of the present invention, when the mobile station performs frequency correction, the mobile station has a function of transmitting the frequency-corrected information added to the signal transmitted by the mobile station, and the mobile station transmits the frequency to the received signal. Since the transmission / reception frequency of the local station is corrected based on the transmission frequency received only when the corrected information is added, the mobile station is based on the reliable frequency to which the frequency corrected information is added. And stable frequency deviation correction is possible.

  According to the invention described in claim 2, since the mobile station has a function of transmitting the frequency-corrected information added to the signal transmitted by the mobile station when frequency correction is performed, In relation to this, even in a mobile station that can communicate only with a mobile station, stable frequency deviation correction can be performed based on a reliable frequency to which frequency corrected information is added.

  According to the invention of claim 3, the mobile station and the mobile station have a function of storing the date and time when the previous frequency was corrected, and when a predetermined time has elapsed from the date and time when the previous frequency was corrected. Has the function of deleting and transmitting the frequency-corrected information, so that it is possible to prevent the frequency deviation from being corrected in the mobile station when the transmission frequency cannot be trusted over time. .

  According to the invention of claim 4, the mobile station and the mobile station have a function of storing a temperature when the previous frequency is corrected, and a predetermined temperature change has occurred since the previous frequency correction. If it occurs, the function to delete and transmit the frequency corrected information is provided, so that if the transmission frequency cannot be trusted due to the change of temperature condition, the mobile station will correct the frequency deviation. Can be prevented.

It is the schematic diagram showing an example of the positional relationship of the base station which comprises the radio | wireless system of this invention, a mobile station, and a mobile station. It is a block diagram showing the structure of a mobile station and a mobile station. It is an operation | movement diagram showing operation | movement by the present invention of the base station in Example 1, a mobile station, and a mobile station.

  A radio communication system according to the present invention includes at least one mobile station that communicates with a base station using a two-wave duplex method and one mobile station that communicates with the mobile station using a one-wave simplex method. Is a radio communication system capable of correcting the transmission / reception frequency of the own station with reference to the transmission frequency from the base station, and the mobile station adds frequency corrected information to the signal transmitted by the mobile station when the frequency correction is performed. The mobile station has a function of adding and transmitting, and the mobile station corrects the transmission / reception frequency of the mobile station based on the received transmission frequency only when frequency-corrected information is added to the received signal. To do. Details will be described below.

  The wireless communication system according to the present invention includes at least one base station, one mobile station, and one mobile station, and will be described below based on the positional relationship shown in FIG. 1 as an example. In the present invention, the base station has a function of transmitting at the frequency FH and receiving at the frequency FL (two-wave duplex method), and the mobile station receives the frequency FH and transmits at the frequency FL and the frequency FL. It is assumed that the mobile station has a function (two-wave duplex method) for performing transmission / reception at a frequency, and the mobile station has a function (one-wave simplex method) for transmitting / receiving at the frequency FL. Further, in the present invention, a single station simplex (one wave simplex) radio device that can communicate wirelessly only with a mobile station is referred to as a mobile station. In FIG. 1, the positional relationship between one base station, two mobile stations 1 and 2, and three mobile stations 1 to 3 is shown.

FIG. 2 is a block diagram showing a basic configuration common to mobile stations and mobile stations. As shown in FIG. 2, the mobile station and the mobile station are configured by a radio unit 11 and a control calculation unit 12. The radio unit 11 is provided with a TCXO 13 and can be adjusted in oscillation frequency by voltage control via a D / A conversion unit 21 and a low-pass filter (LPF) 22. Further, a temperature sensor 14 is provided in the vicinity of the TCXO 13, and the measured temperature is output to the control unit 29 via the A / D conversion unit 23. The reference signal generated by the TCXO 13 is frequency-converted by a local oscillator in the PLL synthesizer unit 15 and input to the transmission / reception circuit unit 16 as a local frequency (transmission / reception frequency of the own station).
The TCXO 13 includes a voltage-controlled VC-TCXO.

  When demodulating the received signal in the control operation unit 12, the received signal from the transmission / reception circuit 16 is input to the demodulation unit 24 via the A / D conversion unit 20. The demodulation unit 24 performs filtering processing, phase error detection / correction, timing correction, demapping processing, and the like. The power detection unit 26 calculates the amplitude of the demodulated data and the current received electric field level, and the timing detection unit 27 performs symbol position detection processing for decoding the data. The demodulated data obtained by the demodulating unit 24 is decomposed into functional channels by the channel decomposing unit 25, and the telegram / control information is decoded by the control unit 29. Further, frequency deviation information is obtained from the demodulated data in the frequency deviation detection unit 28, a correction amount is calculated from the frequency deviation in a TCXO · AFC (Auto Frequency Control) unit 30, and the D / A conversion unit 21 is calculated. By controlling the output voltage value, the oscillation frequency of the TCXO 13 is changed, and the reception frequency and the local frequency of the own station are corrected. The latest voltage value output to the D / A converter 21 is stored in the memory 31.

  In the case of generating a transmission signal in the control calculation unit 12, the message / control information to be transmitted in the control unit 29 is collected, and a data format is created in the channel assembly unit 32. Next, a baseband signal is generated in the modulation unit 33 and the D / A conversion unit 17, mixed with the local frequency from the PLL synthesizer unit 15 in the transmission / reception circuit unit 16, and transmitted from the transmission / reception circuit unit 16.

  When a mobile station that has performed frequency correction based on a transmission frequency from a base station transmits a signal to communicate with another mobile station or a mobile station, frequency-corrected information is added to the transmission signal. In the following, the operation description based on the positional relationship of FIG. 1 will be described in detail with reference to FIG.

  In FIG. 3, the mobile station 1 and the mobile station 2 in the base station area correct the frequency deviation with reference to the transmission frequency transmitted from the base station at the frequency FH. Usually, since the crystal oscillator in the base station adopts OCXO, it is transmitted at a very stable frequency. In the mobile station 1 and the mobile station 2 that have corrected the frequency deviation, the memory 31 stores the date and time when the frequency deviation was corrected. Then, as shown in FIG. 3, when transmitting from the mobile station 1 to the mobile station 1 and the mobile station 2, the frequency corrected information is added and transmitted. Specifically, when creating a message to be transmitted by the control unit 29 of the mobile station 1, an information bit indicating that correction has been made is provided, and the message is created after rewriting this to information indicating that correction has been made. (For example, “1” in one information bit) is a transmission signal.

The mobile station 1 and the mobile station 2 that have received the signal from the mobile station 1 check whether or not the received signal includes frequency corrected information. Is used as a reference wave to correct the transmission / reception frequency of the station. Specifically, the frequency deviation is acquired based on the signal from the mobile station only when the frequency-corrected information is added to the signal received from the mobile station, and from the mobile station based on the acquired frequency deviation. The control voltage applied to the TCXO 13 is changed so that the frequency of the received signal matches the local frequency of the local station.
Also, in the mobile station 1 and the mobile station 2, the date and time when the frequency deviation was corrected is stored in the memory 31, and for example, as shown in FIG. 3, transmission is performed from the mobile station 2 to the mobile station 3. Is transmitted with the frequency-corrected information added, and the mobile station 3 uses this as a reference wave to correct the frequency deviation.

  On the other hand, in the mobile station 1, when a predetermined time has elapsed since the date and time when the frequency deviation was corrected last time stored in the memory 31, the frequency corrected information is deleted (for example, in one information bit). “0”) to create a transmission message. Therefore, in this case, even if the transmission signal from the mobile station 1 is received by the mobile station 1 and the mobile station 2, the frequency deviation is not corrected. The elapsed time in this case can be set to a length in a range where good communication is not hindered by a frequency deviation due to a change with time.

  As described above, according to the present invention, in a single-wave simplex portable station capable of wireless communication only with a mobile station regardless of the inside or outside of the base station area, the frequency deviation is corrected according to the presence / absence of frequency corrected information. This makes it possible to determine whether or not to perform a reliable and stable frequency deviation correction in the mobile station.

  In the above example, the frequency corrected information is deleted when a predetermined time has elapsed from the date and time when the frequency deviation was corrected last time. However, the present invention is not limited to this. For example, the temperature near the TCXO 13 when the frequency deviation was corrected last time is stored in the memory 31, and the frequency has been corrected when the temperature has changed to such an extent that good communication is hindered by the frequency deviation due to the temperature change. It can also be configured to delete information. By adding in the case of such a change in temperature conditions, more reliable and stable correction of the frequency deviation becomes possible.

  In this description, the communication between the base station and the mobile station is assumed to be two-wave duplex. However, even if this is an operation using two-wave half duplex and two-wave simplex, the mobile station The transmission / reception frequency of the mobile station can be corrected.

DESCRIPTION OF SYMBOLS 11 ... Radio | wireless part, 12 ... Control calculating part, 13 ... TCXO, 14 ... Temperature sensor, 15 ... PLL synthesizer part, 16 ... Transmission / reception circuit part, 17 ... D / A conversion part, 20 ... A / D conversion part, 21 ... D / A conversion unit, 22... Low-pass filter, 23... A / D conversion unit, 24... Demodulation unit, 25... Channel decomposition unit, 26 ... power detection unit, 27 ... timing detection unit, 28. ... Control unit, 30 ... TCXO / AFC unit, 31 ... Memory, 32 ... Channel assembly unit, 33 ... Modulation unit.

Claims (4)

  At least one mobile station that communicates with a base station using a two-wave duplex method and one mobile station that communicates with the mobile station using a one-wave simplex method, and the mobile station transmits from the base station In a wireless communication system capable of correcting a transmission / reception frequency of a local station based on a frequency, the mobile station has a function of transmitting a frequency-corrected information added to a signal transmitted by the mobile station when the frequency is corrected The mobile communication system corrects the transmission / reception frequency of the mobile station based on the received transmission frequency only when the frequency-corrected information is added to the received signal.   2. The wireless communication system according to claim 1, wherein the mobile station has a function of transmitting frequency corrected information added to a signal transmitted by the mobile station when frequency correction is performed.   The mobile station and the mobile station have a function of storing the date and time when the previous frequency was corrected, and when a predetermined time has elapsed from the date and time when the previous frequency was corrected, the frequency corrected information is deleted and transmitted. The wireless communication system according to claim 1, further comprising:   The mobile station and the mobile station have a function of storing the temperature when the previous frequency is corrected, and when a predetermined temperature change has occurred since the previous frequency correction, the frequency corrected information The wireless communication system according to claim 1, further comprising a function of deleting and transmitting a message.

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