JP2021068962A - Wireless communication system - Google Patents

Abstract

To provide a wireless communication system that does not disrupt wireless communication even when a base station device cannot reproduce a reference clock signal.SOLUTION: A ring-type wired network is constructed in which a central device and a plurality of base station devices are connected via a wired line in a ring shape and which has an active line and a standby line. The central device distributes a reference clock signal to the plurality of base station devices via the active and standby lines. Each of the base station devices includes: a first clock reproduction unit that reproduces the reference clock signal from the active line to set the same as an active reference clock signal; a second clock reproduction unit that reproduces the reference clock signal from the standby line to set the same as a standby reference clock signal; and a clock failure alarm unit that issues a clock failure alarm when the first clock reproduction unit cannot reproduce the reference clock signal. When the clock failure alarm is issued, the central device switches the active line to the standby line.SELECTED DRAWING: Figure 2

Description

The present invention relates to a wireless communication system, and more particularly to a wireless communication system in which a plurality of base station devices connected in a column and a central device are connected by a wired network.

In a wireless communication system, a carrier wave is modulated to generate a transmission signal and transmitted. The carrier wave contains phase noise, but the lower the phase noise, the less the distortion of the radio signal, and the desired radio performance can be obtained. Atomic clocks such as rubidium atomic clocks or cesium atomic clocks, such as those used in master clock generation and clock supply devices such as synchronous digital hierarchy (SDH) communications to generate low phase noise carriers. Is conceivable to use. However, in order to operate these, it is necessary to adjust the environmental conditions such as temperature and humidity, electromagnetic waves, etc., which increases the equipment space and the cost, so that the carrier wave is generated in the base station device and the mobile station device of the wireless communication system. Not suitable for part use.

Patent Document 1 discloses a method in which a base station apparatus is separated into a master station apparatus and a slave station apparatus, connected by a wired line, and a reference clock signal is supplied from the master station apparatus to the slave station apparatus. According to Patent Document 1, the master station device connects to a higher-level mobile exchange, passes communication data to the slave station device, and the slave station device is responsible for wireless communication with the mobile station. The master station device is provided with a reference clock generator, and data is transmitted to the slave station device in synchronization with the reference clock generator. Further, the slave station device reproduces a reference clock from the transmission signal and operates in synchronization with the reference clock. Further, the slave station device generates a carrier wave based on the reference clock.

Japanese Unexamined Patent Publication No. 2004-31150

In the wireless communication system disclosed in Patent Document 1, for example, by adopting the configuration disclosed in FIG. 6, it is not necessary to deploy the reference clock generator in the slave station device, and the base station can be miniaturized. Although disclosed, there is a problem that wireless communication is interrupted in the area covered by the slave station device when the reference clock signal cannot be reproduced by the slave station device.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a wireless communication system in which wireless communication is not interrupted even when a reference clock signal cannot be reproduced in a base station apparatus. To do.

The wireless communication system according to the present invention is a wireless communication system including a central device, a plurality of base station devices, and a mobile station device that wirelessly communicates with the plurality of base stations. A ring-type wired network having a working line and a backup line is constructed by connecting the base station device with a wired line in a ring shape, and the central device uses the reference clock signal as the reference clock signal to the working line and the standby line. The reference clock signal is distributed to the plurality of base station devices via the standby line, and each of the plurality of base station devices reproduces the reference clock signal distributed via the active line to reproduce the active reference clock. A first clock reproduction unit used as a signal, a second clock reproduction unit that reproduces the reference clock signal distributed via the backup system line to be a backup reference clock signal, and at least the first clock reproduction unit. When the clock failure alarm unit is provided with a clock failure alarm unit that issues a clock failure alarm when the reference clock signal cannot be reproduced in the clock reproduction unit, and the clock failure alarm is issued from the clock failure alarm unit, the clock failure alarm unit is provided. By transferring the clock failure alarm to the central device, the line of the active system is switched to the line of the standby system in the central device.

According to the wireless communication system according to the present invention, wireless communication is not interrupted even when the reference clock signal cannot be reproduced in the base station apparatus.

It is a block diagram which shows the structure of the wireless communication system 1000 of Embodiment 1 which concerns on this invention. It is a functional block diagram which shows the structure of the base station apparatus of Embodiment 1. FIG. It is a block diagram which shows the structure of the clock reproduction part. It is a figure explaining the flow of an optical signal at the time of normal in a wireless communication system. It is a figure explaining the flow of an optical signal when an abnormality that breaks an optical fiber occurs. It is a figure explaining the flow of an optical signal when a clock failure occurs in a base station apparatus. It is a functional block diagram which shows the structure of the base station apparatus of Embodiment 2. It is a functional block diagram which shows the structure of the base station apparatus of Embodiment 2. It is a figure which shows typically the line switching condition.

<Embodiment 1>
<System configuration>
FIG. 1 is a block diagram showing a configuration of the wireless communication system 1000 according to the first embodiment of the present invention. The wireless communication system 1000 shown in FIG. 1 illustrates application to a train radio system, in which a commander in a train command room communicates with a mobile station device 50a of a crew member who is on board a train via a command desk 1. , Voice, or data communication is assumed.

As shown in FIG. 1, the wireless communication system 1000 includes a reference clock generator 2, a server 3, a central device 4, and n base station devices 10-1, 10-2, ..., 10-n. And a mobile station device 50a.

The central device 4 includes a central IF (interface) unit 200, a central control unit 201, and a central switching unit 202. The central IF unit 200 is connected to a command table 1 and is a voice of a commander and a command table 1 by a commander. The operation content of is converted into a voice signal and an operation data signal by the command desk 1 and transmitted to the central IF unit 200. On the contrary, the voice of the crew in the train and the operation contents for the mobile station device 50a are output to the command desk 1 via the central IF unit 200.

The server 3 is a storage device that stores audio signals and data signals, but when directly connected to the central IF unit 200, the server 3 and the mobile station device 50a communicate with each other via the central IF unit 200. can do.

The audio signal and the data signal input from the command desk 1 or the server 3 are subjected to frame processing or the like by the central control unit 201 and input to the central switching unit 202. The input signal is bifurcated by the central switching unit 202, converted into an optical signal, and output to the optical fibers 7u-1, 7d- (n + 1).

The central switching unit 202 and the base station device 10-1 are connected via optical fibers 7u-1 and 7d-1. The base station apparatus 10-1 and the base station apparatus 10-2 are connected via optical fibers 7u-2 and 7d-2. In this way, the base station apparatus 10- (i-1) and the base station apparatus 10-i are connected via the optical fibers 7u-i and 7di-i. Here, i is a natural number from 1 to n. The final base station apparatus 10-n is connected to the central switching unit 202 in a ring shape via optical fibers 7u- (n + 1) and 7d- (n + 1). That is, the central device 4 and the base station devices 10-1, 10-2, ..., 10-n form a double ring-type wired network consisting of a working line and a backup line.

Here, the system in which data is output from the central device, transmits the optical fibers 7u-1, 7u-2, ..., 7u- (n + 1) and returns to the central device 4 is called a U system, and is usually here. Is the active line. On the other hand, the system that transmits the optical fibers 7d- (n + 1), 7dn, ..., 7d-1 is referred to as the D system, and this is usually referred to as the backup system.

Further, the base station devices 10-1, 10-2, ..., 10-n are connected to the antennas 9-1, 9-2, ..., 9-n, respectively, and are used for voice data, signal data, and the like. The data is output as a radio signal from the antennas 9-1, 9-2, ..., 9-n.

The mobile station device 50a selects and processes the radio signal having the highest received electric field strength from the radio signals output from the antennas 9-1, 9-2, ..., 9-n. Thereby, it is determined which of the base station devices 10-1, 10-2, ..., 10-n belongs to the subordinate of the base station device. When the mobile station device 50a transmits a radio signal, the radio signal is received by the antenna of the base station device to which the mobile station device 50a belongs, and is transmitted to the central device 4 via the base station device.

<Reference clock generator>
In the wireless communication system 1000 of the first embodiment, the reference clock generation unit 2 generates a reference clock signal and inputs it to the central device IF unit 200. Since the central device 4 operates in synchronization with the reference clock signal, the signal transmitted through the central device 4 and the signal output from the central device 4 are synchronized with the reference clock signal.

The central device 4 may use a multiplied wave of the frequency of the reference clock signal input from the reference clock generation unit 2 as the reference clock signal of the central device 4.

<Configuration of base station equipment>
FIG. 2 is a functional block diagram showing the configuration of the base station apparatus 10-1 of the first embodiment. As shown in FIG. 2, the base station apparatus 10-1 includes a U-system optical receiver 100u-1, a U-system optical transmitter 154u-1, a D-system optical receiver 100d-1, and a D-system optical transmitter 154d-1. The optical fibers 7u-1, 7u-2, 7d-1 and 7d-2 are connected to each of the above.

Further, the U-based optical receiving unit 100u-1, the U-based optical transmitting unit 154u-1, the D-based optical receiving unit 100d-1, and the D-based optical transmitting unit 154d-1 are the reception processing unit 101u-1 and the transmission processing unit, respectively. It is connected to 153u-1, reception processing unit 101d-1, and transmission processing unit 153d-1.

The reception processing unit 101u-1 is connected to the transmission processing unit 153u-1, the clock reproduction unit 102u-1 (first clock reproduction unit), and the line selection unit 103-1. The clock reproduction unit 102u-1 selects the clock. It is connected to the unit 104-1.

The reception processing unit 101d-1 is connected to the transmission processing unit 153d-1 and the clock reproduction unit 102d-1 (second clock reproduction unit), and the clock reproduction unit 102d-1 is connected to the clock selection unit 104-1. ing.

Further, the reception processing unit 101d-1 is connected to the line selection unit 103-1, the line selection unit 103-1 is connected to the D / A conversion unit 105-1, and the D / A conversion unit 105-1 is a modulation unit. It is connected to 106-1, the modulation unit 106-1 is connected to the amplification unit 107-1, and the amplification unit 107-1 is connected to the demultiplexing unit 120-1. The demultiplexing unit 120-1 is connected to the antenna 9-1 and the amplification unit 150-1.

The amplification unit 150-1 is connected to the demodulation unit 151-1, the demodulation unit 151-1 is connected to the A / D conversion unit 152-1, and the A / D conversion unit 152-1 is connected to the transmission processing unit 153u-1 and the transmission processing unit 153-1. It is connected to the transmission processing unit 153d-1.

Further, the clock selection unit 104-1 is connected to the carrier wave generation unit 108-1, and the carrier wave generation unit 108-1 is connected to the demodulation unit 151-1 and the modulation unit 106-1.

Further, a line failure alarm unit 109-1 is connected to the transmission processing unit 153u-1 and the transmission processing unit 153d-1, and a clock failure alarm unit 110-1 is connected to the line failure alarm unit 109-1. In FIG. 2, the line failure alarm unit 109-1 and the clock failure alarm unit 110-1 are connected, and the line failure alarm unit 109-1 is connected to the transmission processing unit 153u-1 and the transmission processing unit 153d-1. However, the clock failure alarm unit 110-1 may be connected to the transmission processing unit 153u-1 and the transmission processing unit 153d-1, or the line failure alarm unit 109-1 and the clock failure alarm unit 110-1 may be connected. Both may be connected to the transmission processing unit 153u-1 and the transmission processing unit 153d-1.

Although not shown for convenience, the reception processing unit 101u-1 and the reception processing unit 101d-1 are connected to the line failure alarm unit 109-1 and the clock failure alarm unit 110-1, and reception data is input. Will be done.

Although not shown for convenience, the line failure alarm unit 109-1 and the clock failure alarm unit 110-1 are connected to the line selection unit 103-1, and the determination results of each are obtained by the line selection unit 103-1. Is entered in.

Although not shown for convenience, the line selection unit 103-1 is connected to the clock selection unit 104-1, and the selection result of the line selection unit 103-1 is input to the clock selection unit 104-1.

The clock failure alarm unit 110-1 can be realized by a microcomputer and an FPGA (Field-Programmable Gate Array), and the carrier wave generator unit 108-1 can be realized by a frequency synthesizer such as a PLL (phase locked loop) circuit.

Although not shown, the base station devices 10-2, ..., 10-n also have the same configuration, and the numbers after the hyphens are only changed to 2, ..., N.

<Signal flow from optical signal reception to wireless signal transmission>
Next, the signal flow from the optical signal reception to the radio signal transmission in the base station apparatus 10-1 will be described with reference to FIG. The U-based optical receiving unit 100u-1 receives a U-based optical signal via the optical fiber 7u-1. On the other hand, the U-based optical transmission unit 154u-1 transmits a U-based optical signal via the optical fiber 7u-2. The received U-system optical signal is converted into an electric signal by the U-system optical reception unit 100u-1 and input to the reception processing unit 101u-1. The reception processing unit 101u-1 performs code conversion, alarm transfer, and the like, and inputs the input to the line selection unit 103-1.

Similarly, the D-system optical signal input via the optical fiber 7u-1 is converted into an electric signal by the D-system optical reception unit 100d-1, input to the reception processing unit 101d-1, and received by the reception processing unit 101d. The reception processing unit 101d-1 performs code conversion, alarm transfer, and the like via -1, and inputs the signal to the line selection unit 103-1.

The line selection unit 103-1 selects the active system from the U system and the D system based on the determination results of the line failure alarm unit 109-1 and the clock failure alarm unit 110-1, and selects the system. The data is output to the D / A conversion unit 105-1 in the subsequent stage.

The D / A conversion unit 105-1 converts the input data into an analog signal and outputs it to the modulation unit 106-1.

The modulation unit 106-1 up-converts the input analog signal when the carrier wave is input from the carrier wave generation unit 108-1.

The up-converted analog signal is amplified by the amplification unit 107-1 and input to the demultiplexing unit 120-1.

The demultiplexing unit 120-1 is also called a duplexer, and has a function of synthesizing and distributing a transmitting signal and a receiving signal when the transmitting antenna and the receiving antenna are shared by one antenna. That is, since the carrier frequency ft of the transmission signal and the carrier frequency fr of the reception signal are different, the combined demultiplexing unit 120-1 transmits the analog signal of the carrier frequency ft input from the amplification unit 107-1 only to the antenna 9-1. It transmits and does not transmit to the amplification unit 150-1. Similarly, the analog signal of the carrier frequency fr input from the antenna 9-1 is transmitted only to the amplification unit 150-1 and not to the amplification unit 107-1.

The analog signal input to the demultiplexing unit 120-1 is transmitted to the antenna 9-1, and among the analog signals, a signal in the frequency range that can be output by the transmitting antenna is output to space as a radio signal.

<Signal flow from wireless signal reception to optical signal transmission>
Next, the signal flow from the radio signal reception to the optical signal transmission in the base station apparatus 10-1 will be described with reference to FIG. The radio signal output from the mobile station device 50a is received by the receiving antenna of the antenna 9-1, and then, among the radio signals propagating in space, the signal in the frequency range in which the receiving antenna can be felt is converted into an analog signal. It is input to the combined demultiplexing unit 120-1.

The analog signal input to the demultiplexing unit 120-1 is transmitted to the amplification unit 150-1 and input to the demodulation unit 151-1.

The demodulation unit 151-1 down-converts the input analog signal when the carrier wave is input from the carrier wave generation unit 108-1.

The down-converted analog signal is converted into a digital signal by the A / D conversion unit 152-1 and input to the U system transmission processing unit 153u-1 and the D system transmission processing unit 153d-1.

The transmission processing units 153u-1 and 153d-1 perform code conversion, alarm transfer, and the like on the digital signal, and input the digital signals to the U system optical transmission unit 154u-1 and the D system optical transmission unit 154d-1, respectively.

The U-system optical transmitter 154u-1 and the D-system optical transmitter 154d-1 transmit U-system and D-system optical signals, respectively, and output them to the optical fibers 7u-2 and 7d-1.

<Reference clock signal and carrier wave flow>
Next, the flow of the reference clock signal and the carrier wave in the base station apparatus 10-1 will be described with reference to FIG. The U-system clock reproduction unit 102u-1 reproduces the U-system reference clock signal from the electric signal branched by the reception processing unit 101u-1. The reference clock signal (active system reference clock signal) reproduced by the clock reproduction unit 102u-1 is the U system optical reception unit 100u-1, the reception processing unit 101u-1, the transmission processing unit 153u-1, and the U system optical transmission unit. It is used as a clock to drive 154u-1. For convenience, the route of the reference clock signal is not shown.

Similarly, the D system clock reproduction unit 102d-1 reproduces the D system reference clock signal (preliminary system reference clock signal) from the electric signal branched by the reception processing unit 101d-1, and the reproduced reference clock signal. Is used as a clock for driving the D system optical reception unit 100d-1, the reception processing unit 101d-1, the transmission processing unit 153d-1, and the D system optical transmission unit 154d-1. For convenience, the route of the reference clock signal is not shown.

The U-system reference clock signal and the D-system reference clock signal are input to the clock selection unit 104-1. The clock selection unit 104-1 selects the reference clock signal of the line selected by the line selection unit 103-1 and outputs it to the carrier wave generation unit 108-1.

The carrier wave generator 108-1 generates a carrier wave based on the input reference clock signal and outputs the carrier wave. The frequencies of the reference clock signal and the carrier wave do not necessarily have to be the same, and the frequency of the reference clock signal may be multiplied to form the carrier wave.

Since the reference clock signal reproduced by the clock reproduction unit 102u-1 is reproduced in synchronization with the optical reception signal, the optical transmission signal is also synchronized with the optical reception signal. In this way, the central device 4 and the base station devices 10-1, ..., 10-n form a synchronous transmission line network.

Next, a method of reproducing the reference clock signal in the clock reproduction unit 102u-1 will be described with reference to FIG. FIG. 3 is a functional block diagram showing the configuration of the clock reproduction unit 102u-1. As shown in FIG. 3, the clock reproduction unit 102u-1 reproduces a reference clock signal by using a phase-locked loop (PLL).

That is, the clock reproduction unit 102u-1 includes a phase-locked loop composed of a phase comparator 1011 connected in a loop, a loop filter 1012, a VCO (Voltage-Controlled Oscillator: voltage controlled oscillator 1013, and a frequency divider 1014). If the VCO 1013 outputs a clock signal having the same frequency as the reference clock signal, the configuration may not include the VCO 1013.

The phase comparator 1011 compares the phases of the input signal of the clock reproduction unit 102u-1 input from the reception processing unit 101u-1 and the output signal of the VCO 1013 via the frequency divider 1014, and the electricity is proportional to the phase difference. Output a signal.

The loop filter 1012 is a low-pass filter, extracts low-frequency components of the output signal of the phase comparator 1011 and outputs them as an electric signal.

The VCO 1013 changes the frequency of the output clock signal according to the voltage of the output signal of the loop filter 1012.

Then, the gain of the loop filter 1012 is set so that the phase difference disappears. As a result, when the input signal has a phase earlier than the output signal of the VCO 1013, the phase of the output signal of the VCO 1013 is earlier. On the contrary, when the input signal has a slower phase than the output signal of the VCO 1013, the phase of the output signal of the VCO 1013 is delayed. In this way, the reference clock signal synchronized with the input signal of the clock reproduction unit 102u-1 can be reproduced.

Further, in the raw data, bits 0 or 1 may be continuous for a long time, but in this case, the cycle may be too long and the clock of the frequency originally desired to be reproduced may not be output. Therefore, in order to reproduce the reference clock signal, the input signal of the clock reproduction unit 102u-1 may be scrambled. This makes it possible to suppress a long-period bit string and reproduce the clock. The D-system clock reproduction unit 102d-1 also adopts the same configuration.

Therefore, if the phase noise of the reference clock signal of the reference clock generation unit 2 is low, the phase noise of the carrier waves of the base station devices 10-1, ..., 10-n can be reduced. That is, a desired carrier frequency can be obtained with high accuracy.

Here, since the atomic clock used in the generation of the master clock such as SDH communication and the clock supply device is used for the generation of the reference clock signal in the reference clock generation unit 2, the phase noise can be reduced. Such an atomic clock increases the equipment space and increases the cost, but there is no problem because it is provided only in the central device 4.

In the base station apparatus 10-1, each configuration in the base station apparatus 10-1 operates with the self-propelled clock signal until the reference clock signal is reproduced from the received optical signal.

Here, a self-propelled clock source (not shown) composed of oscillators such as TCXO (Temperature-compensated crystal Oscillator) and OCXO (Oven-Controlled crystal Oscillator) is mounted on the substrate on which the base station apparatus 10-1 is constructed. Has been done. The self-propelled clock signal is a clock signal generated by this self-propelled clock source, and is a clock signal that is not dependent on (synchronized with) other clock signals.

The self-propelled clock signal is an optical signal from the base station device at the stage where the optical signal cannot be received and at the initial startup immediately after the power of the base station devices 10-1, 10-2, ... 10-n is turned on. Is used when is not input, and is also used for the period (about several seconds to 10 seconds) from the received optical signal to the reproduction of the reference clock signal as described above.

<Flow of optical signal>
Next, the flow of the optical signal in the wireless communication system 1000 will be described with reference to FIGS. 2 and 5 with reference to FIG.

<Normal>
FIG. 4 is a diagram illustrating a normal flow of optical signals in the wireless communication system 1000. When the wireless communication system 1000 is normal, in the U system, the optical signal output from the central switching unit 202 in the central device 4 is input to the base station device 10-1 via the optical fiber 7u-1. After that, it is converted into a wireless signal inside the base station apparatus 10-1, and an optical signal is output from the base station apparatus 10-1 to the optical fiber 7u-2.

Hereinafter, similarly, the optical signal returns to the central switching unit 202 via the optical fiber 7u- (n + 1) via the base station apparatus 10-2, ..., 10-n in this order.

On the other hand, even in the D system, the optical signal output from the central switching unit 202 is input to the base station apparatus 10-n via the optical fiber 7d- (n + 1). After that, it returns to the central switching unit 202 via the optical fiber 7d-1 via the base station apparatus 10- (n-1), ..., 10-1 in order.

In this way, the optical signal returns to the central switching unit 202 in both the U system and the D system because the commander hears the voice spoken by the train crew, that is, the voice of the commander is the central device 4 → The voice of the crew is transmitted in the order of base station device 10-1 → mobile station device 50a, and the voice of the crew is mobile station device 50a → base station device 10-1 → base station device 10-2 → ... 10-n → central device 4 Is transmitted in the order of.

Next, the flow of the radio signal output from the mobile station device 50a will be described by taking the case where the mobile station device 50a is under the control of the base station device 10-1 as an example. In this case, the base station device 10-1 receives the radio signal output from the mobile station device 50a and converts it into an analog signal. In the U system, analog signal data is added to the data received via the optical fiber 7u-1, and the data is output to the optical fiber 7u-2. Therefore, since the data is received by the central switching unit 202 via the base station devices 10-2, ..., 10-n in order, the radio signal data output from the mobile station device 50a reaches the central device 4. To do.

As a result, the commander can hear the voice spoken by the crew member via the mobile station device 50a. Further, if the mobile station device 50a is connected to a device that collects vehicle failures, vehicle failure information and the like can be transmitted to the commander, and information on the vehicle side can be transmitted.

Similarly, in the D system, the radio signal data output from the mobile station device 50a reaches the central device 4 from the base station device 10-1 via the optical fiber 7d-1.

The central device 4 controls to output the data of the active system out of the data received from the above two systems to the command desk 1 or the server 3. For example, if the U system is initially set as the active system, the data of the U system is output to the command desk 1 or the server 3 in the normal state.

<When the optical transmission line is abnormal>
FIG. 5 is a diagram illustrating a flow of an optical signal when an abnormality occurs in which the optical fiber 7u-2 is disconnected in the wireless communication system 1000. In this case, in the U system, the optical signal is output from the base station apparatus 10-1 to the optical fiber 7u-2. However, since the optical fiber 7u-2 is disconnected, the optical signal does not reach the base station apparatus 10-2. In this case, the line failure alarm unit 109-2 does not receive the optical signal that should have been output from the base station device 10-1 on a regular basis, so that the line failure occurs in the working U system. As a result, a line failure alarm is issued.

When the line selection unit 103-2 detects that a line failure alarm has been issued in the U system of the active system, the line selection unit 103-2 switches the active system from the U system to the D system. As a result, the D system data is output to the D / A conversion unit 105-2 in the subsequent stage, and is transmitted from the antenna 9-2 via the modulation unit 106-2, the amplification unit 107-2, and the demultiplexing unit 120-2. A radio signal based on the correct data is transmitted.

Further, the line failure alarm issued by the base station apparatus 10-2 is stored in the overhead of the transmission data and output to both the U system and the D system optical fibers. As a result, the subsequent base station apparatus, that is, the base station apparatus 10-3 in the U system, the base station apparatus 10-1 in the D system, and the base station apparatus 10-2 are notified that a line failure has occurred. .. The subsequent base station device that received the line failure alarm further transmits the line failure alarm to the subsequent base station device, and by repeating this, a line failure occurs in the central device 4 at the base station device 10-2. You can notify that.

As a result, when the optical fiber 7u-2 is disconnected, the active system can be switched from the U system to the D system in the central device 4, and the wireless communication is not interrupted even if a line failure occurs. ..

Further, when the optical fiber 7u-2 is disconnected, instead of using the U system input data as the U system output data of the base station apparatus 10-2, the D system input data input from the optical fiber 7d-3 is used. May be used. This is schematically shown in FIG. 5 by providing a line connecting the D system to the U system of the base station apparatus 10-2.

<At the time of clock failure>
FIG. 6 is a diagram illustrating a flow of an optical signal when a clock failure occurs in the U system of the base station apparatus 10-2. When a clock failure occurs in the U system of the base station apparatus 10-2, the optical signal is not output to the optical fiber 7u-3, and the optical signal is not transmitted to the base station apparatus after the base station apparatus 10-3. .. In this case, the clock failure alarm unit 110-2 detects that the reference clock signal could not be reproduced by the clock reproduction unit 102u-2, and issues a clock failure alarm.

Here, as a method of detecting that the reference clock signal could not be reproduced by the clock failure alarm unit 110-2, when transmitting the reference clock signal, a fixed pattern is inserted into the header unit of the transmission data and transmitted, and the reference clock signal is transmitted. At the time of reproducing the clock signal, it is possible to detect whether or not the reference clock signal can be reproduced by determining whether or not the fixed pattern can be reproduced without a bit error. Further, when the time change amount of the output voltage of the loop filter of the clock reproduction unit 102u-1 becomes a certain value or less, it may be determined that the signal has converged and the reference clock signal may be reproduced.

When a clock failure occurs, the reference clock signal synchronized with the optical reception signal cannot be reproduced, and the clock frequency may be deviated. It is also possible that the U-based optical receiver 100u-2 has failed to reproduce the data.

The clock failure alarm issued by the clock failure alarm unit 110-2 is stored in the overhead of the transmission data and output to both the U system and the D system optical fibers. As a result, it is notified that a clock failure has occurred in the base station equipment in the subsequent stage of the U system and the D system. The subsequent base station device that received the clock failure alarm further transmits the clock failure alarm to the subsequent base station device, and by repeating this, a clock failure occurs in the base station device 10-2 in the central device 4. You can notify that. As a result, in the central device 4, the active system can be switched from the U system to the D system.

Further, when a clock failure occurs in the base station device 10-2, instead of using the U system input data as the U system output data of the base station device 10-3 in the subsequent stage, the input data is input from the optical fiber 7d-4. The input data of the D system may be used. This is schematically shown in FIG. 6 by providing a line connecting the D system to the U system of the base station apparatus 10-3.

As described above, in the wireless communication system 1000 of the first embodiment, each base station apparatus reproduces a reference clock signal from the received optical signal and generates a carrier wave from the reference clock signal. Further, the wireless communication system 1000 constructs a double ring-type wired network having a working system line and a backup system line, and each base station device is notified of a line failure when a line failure occurs in the working system line. A line failure alarm unit is provided to issue a clock failure alarm, and a clock failure alarm unit is provided to issue a clock failure alarm when a clock failure occurs in the base station device, and the optical signal line is used as an active line. Since it is configured to switch from to the standby system line, wireless communication can be continued even if a line failure or clock failure occurs in the active system line. Further, since each base station device is not provided with a reference clock signal generation unit, a low-cost wireless communication system can be realized.

In the first embodiment described above, each base station device has a clock failure alarm unit and a line failure alarm unit, but it may be configured to have only the clock failure alarm unit.

<Embodiment 2>
FIG. 7 is a functional block diagram showing the configuration of the base station device 10-1 in the wireless communication system of the second embodiment according to the present invention. Note that, in FIG. 7, the same components as those of the base station apparatus 10-1 described with reference to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted. The configuration of the wireless communication system is the same as that of the wireless communication system 1000 shown in FIG.

As shown in FIG. 7, in the base station apparatus 10-1, the output stop unit 111-1 is added and connected to the clock failure alarm unit 110-1 and the amplification unit 107-1 to be connected to the output stop unit. The output signal of 111-1 is input to the amplification unit 107-1.

As described in the first embodiment, when the U-system clock failure alarm is issued from the clock failure alarm unit 110-1, the clock selection unit 104-1 is selected by the line selection unit 103-1. It switches to the reference clock signal of the D system line and outputs it to the carrier wave generator 108-1. Normally, the carrier frequency of the radio signal falls within the desired frequency range.

However, when the clock failure alarm is issued in both the U system and the D system, there is no guarantee that the carrier frequency of the radio signal will fall within the desired frequency range. Therefore, when a clock failure alarm is issued in both the U system and the D system, this is notified to the output stop unit 111-1. As a result, the output stop unit 111-1 outputs the output stop signal to the amplification unit 107-1. Upon receiving this, the amplification unit 107-1 suppresses the transmission of the analog signal and suppresses the transmission of the radio signal. The output stop unit 111-1 can be realized by a microcomputer, FPGA, or the like.

As described above, when the output stop unit 111-1 is connected to the clock failure alarm unit 110-1 and the clock failure alarm is issued in both the U system and the D system, the output of the amplification unit 107-1 is issued. Since the output stop signal for stopping the signal is output to the amplification unit 107-1, it is possible to suppress the transmission of the radio signal when the frequency of the carrier wave deviates from the desired frequency range.

In the second embodiment described above, each base station device has a clock failure alarm unit and a line failure alarm unit, but it may be configured to have only the clock failure alarm unit.

<Embodiment 3>
FIG. 8 is a functional block diagram showing the configuration of the base station device 10-1 in the wireless communication system of the third embodiment according to the present invention. Note that, in FIG. 8, the same components as those of the base station apparatus 10-1 described with reference to FIG. 2 are designated by the same reference numerals, and duplicate description will be omitted. The configuration of the wireless communication system is the same as that of the wireless communication system 1000 shown in FIG.

As shown in FIG. 8, in the base station apparatus 10-1, the frequency comparison unit 112-1 is added and connected to the clock reproduction units 102u-1 and 102d-1 as well as to the clock failure alarm unit 110-1. , The output signal of the frequency comparison unit 112-1 is input to the clock failure alarm unit 110-1.

The clock reproduction unit 102u-1 branches the U-system reference clock signal and outputs it to the clock selection unit 104-1 and the frequency comparison unit 112-1. Similarly, the clock reproduction unit 102d-1 outputs the reference clock signal of the D system to the clock selection unit 104-1 and the frequency comparison unit 112-1.

The frequency comparison unit 112-1 receives two reference clock signals and compares their respective frequencies. For example, one reference clock signal is used as an operating clock, and the frequency of the other reference clock signal is measured. The comparison result of the frequency comparison unit 112-1 is input to the clock failure alarm unit 110-1 as an output signal. The frequency comparison unit 112-1 can be realized by using FPGA.

The clock reproduction unit 102u-1 may be released from the locked state to the received data, and a clock failure alarm may be issued. As described above, the phase comparator 1011 (FIG. 3) is used for the clock reproduction units 102u-1 and 102d-1, and the frequency of the clock component of the received data and the output frequency of the frequency divider 1014 are measured. The matching (synchronous) state (the state in which the control of the VCO 1013 has converged) is referred to as the state in which the received data is locked. On the other hand, the state in which the control of the VCO 1013 once converges and is locked to the received data is not synchronized with the received data for some reason, which is referred to as a state in which the lock is released. Examples of this factor include momentary interruption of received data, waveform distortion in a transmission line, and noise. When the lock is released, a clock failure alarm may be issued as if a clock failure has occurred.

Even in this case, the clock reproduction unit 102u-1 can hold over the locked state and output the reference clock signal. Here, the holdover means that when the optical signal cannot be received and the reference clock signal cannot be generated due to various causes, the self-propelled clock signal by the self-propelled clock source described above is used as the reference clock signal. In order for this self-propelled clock signal to be continuously synchronized with the original reference clock signal, self-propelled control of the self-propelled clock source is called holdover.

If the holdover is not performed, the self-propelled clock source outputs a self-propelled clock signal having a phase and frequency different from the optical signal that should be synchronized as soon as the optical signal cannot be received.

Even if the self-propelled clock signal held over is used, it is continuously synchronized with the original reference clock signal. Therefore, the U-system optical receiver 100u-1, the reception processing 101u-1, and the transmission processing unit 153u -1, It is possible to operate the U-system optical transmission unit 154u-1 to perform normal communication for a certain period of time. The fixed time is not unconditionally determined because it depends on the configuration and manufacturing error of the central device and the base station device, but it is considered that the phase and frequency deviations cannot be ignored after 1 to 24 hours.

Therefore, even if a clock failure alarm is issued in the U system, if the clock reproduction unit 102u-1 holds over and the frequency comparison result (frequency difference) in the frequency comparison unit 112-1 is within a predetermined standard. , The frequency comparison unit 112-1 inputs a predetermined output signal to the clock failure alarm unit 110-1, stops the issuance of the clock failure alarm, and causes the clock selection unit 104-1 to the reference clock signal of the D system line. Suppress switching so that the reference clock signal of the U system line can be used continuously.

Here, the permissible deviation of the carrier frequency is defined by the Radio Law and varies depending on the frequency, output power and application, but is about 1 to 10 ppm. Assuming that the allowable deviation of the carrier frequency is A, the frequency difference between the U system and the D system as a predetermined standard is a value (A−α) obtained by subtracting α representing the measurement error and the margin from the allowable deviation A.

In this way, if the frequency difference is within a predetermined standard, suppressing the switching of the D system line to the reference clock signal by the clock selection unit 104-1 is temporary such as momentary interruption of received data and noise. A clock failure alarm may be issued due to some phenomenon, and if only the clock failure alarm is issued as a line switching condition, the line may be switched when it is not necessary to switch, or the U system may be interrupted momentarily. This is because if a momentary interruption occurs in the D system and then a momentary interruption occurs in the U system again, switching may occur continuously. In order to reduce such unnecessary switching, by providing a frequency comparison unit in the base station device, not only the clock failure alarm is issued but also the frequency difference becomes a certain value or more as a line switching condition. Since it is added, unnecessary switching can be reduced.

The line switching conditions described above are schematically shown in FIG. FIG. 9 shows a U-system clock fault alarm, a D-system clock fault alarm, a frequency difference, and a working line. Even if a U-system clock fault alarm is issued, if the frequency difference is within the standard, U It shows that the system line is continued as the working system line, and when the frequency difference becomes out of the standard, the D system line is switched as the working system line.

In the third embodiment described above, each base station device has a clock failure alarm unit and a line failure alarm unit, but it may be configured to have only the clock failure alarm unit.

In the present invention, each embodiment can be freely combined, and each embodiment can be appropriately modified or omitted within the scope of the invention.

4 Central unit, 10-1 Base station equipment, 50a Mobile station equipment, 102u-1, 102d-1 Clock reproduction, 108-1 Carrier wave generator, 109-1 Line failure alarm unit, 110-1 Clock failure alarm unit, 111 -1 Output stop unit, 112-1 Frequency comparison unit.

Claims (6)

Centralized traffic control
With multiple base station equipment,
A wireless communication system including a mobile station device that wirelessly communicates with the plurality of base stations.
The central device and the plurality of base station devices are connected in a ring shape by a wired line to construct a ring-type wired network having a working line and a backup line.
The centralized traffic control
The reference clock signal is distributed to the plurality of base station devices via the active line and the standby line.
Each of the plurality of base station devices
A first clock reproduction unit that reproduces the reference clock signal distributed via the active line to obtain the active reference clock signal.
A second clock reproduction unit that reproduces the reference clock signal distributed via the standby line to obtain a standby reference clock signal, and a second clock reproduction unit.
At least the first clock reproduction unit includes a clock failure alarm unit that issues a clock failure alarm when the reference clock signal cannot be reproduced.
When the clock failure alarm is issued from the clock failure alarm unit, the clock failure alarm is transferred to the central device, whereby the active line is switched to the standby line in the central device. Wireless communication system. Each of the plurality of base station devices
It is provided with a carrier wave generator that generates a carrier wave for wireless communication with the mobile station apparatus based on the active system reference clock signal or the backup system reference clock signal.
The carrier wave generator
When the reference clock signal can be reproduced in the first clock reproduction unit, the carrier wave is generated based on the active system reference clock signal to perform wireless communication with the mobile station apparatus.
The first aspect of claim 1, wherein when the reference clock signal can be reproduced in the second clock reproduction unit, the carrier wave is generated based on the backup reference clock signal to perform the wireless communication with the mobile station apparatus. Wireless communication system. Each of the plurality of base station devices
The first and second clock reproduction units further include an output stop unit that stops the output of the radio signal to the mobile station apparatus when the reference clock signal cannot be reproduced and the clock failure alarm is issued. , The wireless communication system according to claim 1. Each of the plurality of base station devices
Further, a frequency comparison unit for comparing the frequencies of the working system reference clock signal and the backup system reference clock signal is provided.
The frequency comparison result in the frequency comparison unit is given to the clock failure alarm unit.
Even when the clock failure alarm is issued from the clock failure alarm unit,
If the first clock reproduction unit or the second clock reproduction unit is held over and the frequency comparison result satisfies a predetermined standard, the issuance of the clock failure alarm is stopped. The wireless communication system according to claim 1, wherein the line switching is suppressed. Each of the plurality of base station devices
Further provided with a line failure alarm unit that issues a line failure alarm when the wired line is disconnected and a signal does not reach from the base station device in the previous stage.
When the line failure alarm is issued from the line failure alarm unit, the line failure alarm is transferred to the central device via the base station device in the subsequent stage, so that the line of the active system in the central device is used. The wireless communication system according to claim 1, wherein the line is switched to the standby line. Each of the plurality of base station devices
A carrier generation unit that generates a carrier wave for the wireless communication with the mobile station device based on the active system reference clock signal or the backup system reference clock signal is provided.
The carrier wave generator
When the line failure alarm is issued from the line failure alarm unit,
The wireless communication system according to claim 5, wherein the second clock reproduction unit generates the carrier wave based on the backup reference clock signal that reproduces the reference clock signal to perform the wireless communication with the mobile station apparatus. ..

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