JP2006033379A - Central terminal, communications system and method of communicating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a central terminal which can regulate the upward transmission power of a subscriber side apparatus to the optimal level automatically, and to provide a communications system and a method of communication. <P>SOLUTION: A line length measuring sensor 45 TDR measures the line lengths L11-L13 of the telephone lines of subscriber side apparatuses 11-13, immediately after the power of the central terminal 1 is turned on, and applies the power to a memory circuit 46. A control circuit 43 sets the PBO reference length LR1 of the central terminal 1 based on the line lengths L11-L13 stored in the memory circuit 46, and performs an upward transmission power control. Therefore, the line length of each telephone line is measured, irrespective of the connection state of the subscriber side apparatus or ON/OFF state of the power supply, and the reference length of the optimal PBO is automatically determined from its line length information to each service area. Consequently, the upward transmission power of the subscriber side apparatus is automatically regulated to the optimal level. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a station-side device, a communication system, and a communication method, and more particularly, to a station-side device, a communication system, and a communication method that perform data communication using a telephone line.

  In the VDSL (Very High-Bit-rate Digital Subscriber Line) method for performing high-speed data communication using an existing telephone line, a station side device (DSLAM: DSL collective device) and a subscriber High-speed communication with a maximum of about 50 Mbps is realized with the side device.

  The ITU-T (ITU-Telecommunication standardization sector), which is the ITU (International Telecommunication Union) telecommunications standardization sector, recommends "G.993.1" related to the VDSL standard (for example, non-patent literature). 1). ANSI (American National Standards Institute) has published “T1.424 Trial Use” regarding VDSL standards in the United States.

  In the VDSL system, a wide frequency band up to 12 MHz is used in order to realize high-speed communication in the upstream (transmission) direction and the downstream (reception) direction as viewed from the subscriber side. Since a high frequency band with high power attenuation is used, buildings and apartment houses with a relatively short distance (for example, a track length of 500 m or less) are mainly targeted for service.

  FIG. 11 is a block diagram showing a schematic configuration of a conventional communication system using the VDSL system. 11, this communication system includes a station-side device 101 and subscriber-side devices 111 to 113,.

  The station side device 101 and the subscriber side devices 111 to 113,... Are connected by telephone lines having line lengths L111 to L113,. The station side apparatus 101 is connected to the equipment of a VDSL provider via an optical fiber FTTB (Fiber To The Building). The station side device 101 is arranged in a building, for example, and the subscriber side devices 111 to 113,... Are arranged in each room of a VDSL service subscriber in the building. In general, the line length of the telephone line connected between the station side apparatus and the subscriber side apparatus differs depending on the floor and position of the room of the VDSL service subscriber, and the longer the line length, the more the influence of line attenuation. Is big. That is, the power received by the station apparatus 101 from the subscriber apparatus on the long distance line is greatly affected by the line attenuation and becomes weak.

  FIG. 12 is a diagram illustrating the relationship between the reception power of the station side device and the transmission power of the subscriber side device. 12, the power spectral density (PSD) of the transmission power of the subscriber side devices 111 to 113,... And the power of the power received by the station side device 101 from the subscriber side devices 111 to 113,. Spectral density is shown.

  Referring to FIG. 12, when all the transmission powers of subscriber side apparatuses 111 to 113 having line lengths L111 to L113,... Are equal, the power received by station side apparatus 101 from the subscriber side apparatus of a short distance line. Becomes stronger, and the power received by the station side device 101 from the subscriber side device of the long-distance line becomes weaker (see the dotted line portion).

  Further, in upstream communication, a far-end crosstalk in which a short-distance line signal leaks into an adjacent long-distance line becomes a problem. This far-end crosstalk further reduces the communication speed of the long distance line. Therefore, by suppressing the transmission power of the subscriber side devices of the short-distance line among the subscriber side devices 111 to 113,..., The power received by the station side device 101 from each of the subscriber side devices 111 to 113,. There is an equal method (see solid line). As a result, the influence of far-end crosstalk is reduced, and a decrease in the communication speed of the long-distance line is suppressed. This method is called uplink transmission power control (PBO: Power Back Off).

  The uplink transmission power control is intended for a subscriber side device having a line length equal to or shorter than a predetermined PBO reference length LR. The PBO reference length LR has an optimum value (for example, the longest line length in the same building) for each service area (building or apartment house).

Patent Document 1 below discloses a method for reducing near-far crosstalk interference between channels in a communication system. In this case, the amount of crosstalk generated in a channel adjacent to this channel is reduced by shaping the spectrum of the signal carried on a certain channel.
JP 2000-101486 A "Very high speed digital subscriber line (VDSL)", ITU-T recommendation G.993.1

  However, in the conventional communication system, since there is no function for automatically determining a PBO reference length suitable for each service area, it is necessary to manually set the PBO reference length. Further, there was no function for measuring the line length when the subscriber side device was not connected to the station side device or when the connected subscriber side device was turned off. For this reason, it takes time and effort to calculate and set the optimum PBO reference length for each service area.

  Therefore, a main object of the present invention is to provide a station side device, a communication system, and a communication method capable of automatically adjusting the uplink transmission power of a subscriber side device to an optimum level.

  A station-side device according to the present invention is a station-side device that performs data communication with a plurality of subscriber-side devices using a telephone line, and a plurality of telephone lines provided corresponding to the plurality of subscriber-side devices. A measurement sensor that applies a measurement signal to each of the sensors and measures the line length of each telephone line using a reflected wave of the measurement signal, and a memory that stores the line length of each telephone line measured by the measurement sensor as line length information Set the reference length based on the line length information stored in the circuit and the storage circuit, so that the power received by the station side device from each subscriber side device corresponding to the line length below the reference length is the same, And a control circuit for controlling the transmission power of each subscriber side device.

  Preferably, the control circuit sets the reference length based on the longest line length included in the line length information stored in the storage circuit.

  Preferably, the control circuit sets the reference length within a range between a predetermined upper limit value and lower limit value.

  Preferably, when a plurality of frequency bands are used in data communication from each subscriber side device to the station side device, the control circuit sets a reference length corresponding to each of the plurality of frequency bands.

  Preferably, the control circuit updates the reference length when a subscriber-side device is added or deleted.

  Preferably, the storage circuit further stores management information for managing whether or not each of the plurality of subscriber-side devices is receiving a data communication service. The control circuit determines the addition and deletion of the subscriber side device based on the management information stored in the storage circuit.

  In addition, preferably, a determination sensor for determining whether or not each telephone line provided corresponding to each subscriber-side device is connected to the station-side device is provided. The control circuit determines addition or deletion of the subscriber side device based on the determination result by the determination sensor.

  In addition, preferably, when a subscriber side device is added or deleted, the control circuit forcibly stops data communication with all the subscriber side devices and then updates the reference length to The data communication with the subscriber side device is resumed.

  Preferably, the control circuit updates the reference length while continuing data communication with all the subscriber-side devices when the subscriber-side devices are added and deleted.

  In addition, preferably, when a new subscriber side device is added, the control circuit starts data communication using the updated reference length for the added subscriber side device, and performs all other subscriptions. For each of the subscriber side devices, the reference length is updated when data communication is temporarily stopped and restarted, and when the subscriber side device is deleted, the data for each of all the subscriber side devices is updated. The reference length is updated when communication is temporarily stopped and restarted.

  Further, preferably, a counter for counting time is further provided. The control circuit periodically updates the reference length for all the subscriber side devices every time a predetermined time is counted by the counter.

  A communication system according to the present invention includes a plurality of the station side devices connected to each other. A reference length common to the plurality of station side devices is set based on the line length information of each of the plurality of station side devices.

  Another communication system according to the present invention includes the above station-side device and a plurality of subscriber-side devices that perform data communication with the station-side device.

  Preferably, each of the plurality of subscriber side devices includes a switch circuit that disconnects the connection with the corresponding telephone line for a predetermined time when the measurement sensor of the station side device performs line length measurement.

  A communication method according to the present invention is a communication method for performing data communication between a station side device and a plurality of subscriber side devices using a telephone line, and is provided corresponding to the plurality of subscriber side devices. A first step of applying a measurement signal to each of the plurality of telephone lines and measuring a line length of each telephone line using a reflected wave of the measurement signal; and a line of each telephone line measured in the first step A second step of holding the length as line length information, and setting a reference length based on the line length information held in the second step, from each subscriber side device corresponding to a line length less than or equal to the reference length to the station And a third step of controlling the transmission power of each subscriber side device so that the power received by the side device is the same.

  In the station side device according to the present invention, a measurement signal is given to each of a plurality of telephone lines provided corresponding to a plurality of subscriber side devices, and the line length of each telephone line is set using the reflected wave of the measurement signal. A measurement sensor to be measured, a storage circuit that stores the line length of each telephone line measured by the measurement sensor as line length information, and a reference length is set based on the line length information stored in the storage circuit. And a control circuit for controlling the transmission power of each subscriber-side device so that the power received by the station-side device from each subscriber-side device corresponding to the line length is equal. Accordingly, the line length of each telephone line is automatically measured, and the optimum reference length is automatically set for each service area from the line length information. Thereby, the uplink transmission power of the subscriber side apparatus is automatically adjusted to an optimum level.

  Preferably, the control circuit sets the reference length based on the longest line length included in the line length information stored in the storage circuit. In this case, an appropriate reference length is set based on the longest reference length.

  Preferably, the control circuit sets the reference length within a range between a predetermined upper limit value and lower limit value. In this case, an appropriate reference length is set within the range between the upper limit value and the lower limit value.

  Preferably, when a plurality of frequency bands are used in data communication from each subscriber side device to the station side device, the control circuit sets a reference length for each of the plurality of frequency bands. In this case, an appropriate reference length is set for each frequency band.

  Preferably, the control circuit updates the reference length when a subscriber-side device is added or deleted. In this case, the reference length is automatically updated when a new subscriber is added and when the subscriber's service is suspended.

  Preferably, the storage circuit further stores management information for managing whether or not each of the plurality of subscriber-side devices is receiving a data communication service. The control circuit determines the addition and deletion of the subscriber side device based on the management information stored in the storage circuit. In this case, the reference length is automatically updated based on the management information stored in the storage circuit.

  In addition, preferably, a determination sensor for determining whether or not each telephone line provided corresponding to each subscriber-side device is connected to the station-side device is provided. The control circuit determines addition or deletion of the subscriber side device based on the determination result by the determination sensor. In this case, the management information need not be stored in the storage circuit, and the start / pause of the service of the subscriber is detected based on the connection state of each telephone line, and the reference length is updated.

  In addition, preferably, when a subscriber side device is added or deleted, the control circuit forcibly stops data communication with all the subscriber side devices and then updates the reference length to The data communication with the subscriber side device is resumed. In this case, the reference length update operation is quickly performed on all the subscriber side devices.

  Preferably, the control circuit updates the reference length while continuing data communication with all the subscriber-side devices when the subscriber-side devices are added and deleted. In this case, the reference length is updated quickly without stopping data communication with respect to all the subscriber side devices.

  In addition, preferably, when a new subscriber side device is added, the control circuit starts data communication using the updated reference length for the added subscriber side device, and performs all other subscriptions. For each of the subscriber side devices, the reference length is updated when data communication is temporarily stopped and restarted, and when the subscriber side device is deleted, the data for each of all the subscriber side devices is updated. The reference length is updated when communication is temporarily stopped and restarted. In this case, the reference length is appropriately updated without forcibly stopping the data communication for all the subscriber side devices.

  Further, preferably, a counter for counting time is further provided. The control circuit periodically updates the reference length for all the subscriber side devices every time a predetermined time is counted by the counter. In this case, it is not necessary to monitor the service state of the subscriber, and the line length information such as the reference length is automatically updated at a predetermined cycle.

  In the communication system according to the present invention, a plurality of the station side devices connected to each other are provided. A reference length common to the plurality of station side devices is set based on the line length information of each of the plurality of station side devices. Therefore, a common reference length is automatically set for a plurality of station side devices.

  In another communication system according to the present invention, the station side device and a plurality of subscriber side devices that perform data communication with the station side device are provided. Accordingly, the line length of each telephone line is automatically measured, and the optimum reference length is automatically set for each service area from the line length information. Thereby, the uplink transmission power of the subscriber side apparatus is automatically adjusted to an optimum level.

  Preferably, each of the plurality of subscriber side devices includes a switch circuit that disconnects the connection with the corresponding telephone line for a predetermined time when the measurement sensor of the station side device performs line length measurement. In this case, the line length of each telephone line is automatically measured regardless of the connection state of the subscriber side device and the power on / off state, and the optimum PBO reference length for each service area is determined from the line length information. Determined automatically.

  The communication method according to the present invention provides a measurement signal to each of a plurality of telephone lines provided corresponding to a plurality of subscriber side devices, and measures the line length of each telephone line using a reflected wave of the measurement signal. A first step, a second step of holding the line length of each telephone line measured in the first step as line length information, and a reference length based on the line length information held in the second step And a third step of controlling the transmission power of each subscriber-side device so that the power received by the station-side device from each subscriber-side device corresponding to a line length equal to or less than the reference length is the same. Including. Accordingly, the line length of each telephone line is automatically measured, and the optimum reference length is automatically set for each service area from the line length information. Thereby, the uplink transmission power of the subscriber side apparatus is automatically adjusted to an optimum level.

[Embodiment 1]
FIG. 1 is a block diagram showing a schematic configuration of a communication system using the VDSL system according to Embodiment 1 of the present invention. 1, this communication system includes station side devices 1 to 3,... And subscriber side devices 11 to 13, 21 to 23, 31 to 33,.

  The station side devices 1 to 3 are connected to the facilities of the VDSL operator via optical fibers FTTB, respectively. The station side device 1 and the subscriber side devices 11 to 13 are connected by telephone lines having line lengths L11 to L13, respectively. The station side device 2 and the subscriber side devices 21 to 23 are connected by telephone lines having line lengths L21 to L23, respectively. The station side device 3 and the subscriber side devices 31 to 33 are connected by telephone lines having line lengths L31 to L33, respectively. The station side devices 1 to 3 are cascade-connected to the adjacent station side devices, and line length information such as the PBO reference length is exchanged.

  The station side devices 1 to 3 are arranged in a building, for example, and the subscriber side devices 11 to 13, 21 to 23, 31 to 33, and so on are arranged in each room of the VDSL service subscriber in the building. . Depending on the floor number and position of the room in which each of the subscriber side devices 11 to 13, 21 to 23, 31 to 33,... Is arranged, the line lengths L11 to L13, L21 to L23, L31 to L33,. Is different.

  FIG. 2 is a block diagram showing the configuration of the station side device 1 and the subscriber side device 11 shown in FIG. In FIG. 2, the station apparatus 1 includes an input buffer 41, a modem unit 42, a control circuit 43, an output buffer 44, a line length measurement sensor 45, a storage circuit 46, an interface 47, and a terminal 48. Including. The modem unit 42 includes a modulator 51, a hybrid circuit 52, and a demodulator 53. Subscriber side apparatus 11 includes an input buffer 61, a modulator 62, a control circuit 63, a hybrid circuit 64, a demodulator 65, an output buffer 66, and a terminal 67. In the station side device 1, the modem unit 42 and the terminal 48 are provided corresponding to each of the subscriber side devices 11 to 13,.

  When data communication is performed in the downlink (reception) direction viewed from the subscriber side, the input buffer 41 in the station apparatus 1 buffers input data from the outside and supplies the data to the modulator 51. The modulator 51 modulates the data from the input buffer 41 and supplies the data to the hybrid circuit 52. The control circuit 43 receives control information from the outside, and controls the operations of the input buffer 41, the modulator 51, and the station side device 1 as a whole. The modulation data given to the hybrid circuit 52 is given to the subscriber side device 11 via the terminal 48.

  The modulation data given to the subscriber side device 11 is given to the hybrid circuit 64 via the terminal 67. The demodulator 65 demodulates the modulation data from the hybrid circuit 64 and supplies the demodulated data to the output buffer 66, and extracts control information and supplies it to the control circuit 63. The output buffer 66 buffers the data demodulated by the demodulator 65 and outputs it to the outside. The control circuit 63 receives the control information extracted by the demodulator 65 and controls the operation of the subscriber side apparatus 11 as a whole.

  On the other hand, when data communication is performed in the uplink (transmission) direction as viewed from the subscriber side, the input buffer 61 in the subscriber side device 11 buffers input data from the outside and supplies it to the modulator 62. The modulator 62 modulates the data from the input buffer 61 and supplies it to the hybrid circuit 64. The operations of the input buffer 61 and the modulator 62 are controlled by the control circuit 63. The modulation data given to the hybrid circuit 64 is given to the station side device 1 via the terminal 67.

  The modulation data given to the station side device 1 is given to the hybrid circuit 52 via the terminal 48. The demodulator 53 demodulates the modulation data from the hybrid circuit 52 and supplies it to the output buffer 44. The output buffer 44 buffers the data demodulated by the demodulator 53 and outputs it to the outside. The operations of the demodulator 53 and the output buffer 44 are controlled by the control circuit 43.

  The line length measurement sensor 45 immediately after the power supply of the station side device 1 is turned on (and when the reset button is pressed), the line lengths L11 to L13 of the telephone lines of the subscriber side devices 11 to 13,. Measure. As the measurement method, for example, a TDR (Time Domain Reflectometry) measurement function that is generally mounted in an xDSL tester that analyzes a line failure is used.

  FIG. 3 is a diagram for explaining TDR measurement. Referring to FIG. 3, a line length measuring sensor 45 included in the station side device 1 sends a measurement signal (for example, to the subscriber side devices 11, 12,... Via the telephone lines of the line lengths L11 to L13,. , Step signal and pulse signal). The line length measurement sensor 45 receives the measurement signals reflected by the subscriber side devices 11, 12,... And calculates the line lengths L11 to L13,.

  FIG. 4 is a time chart for explaining the operation when TDR measurement is performed using a step signal. The step signal transmitted from the line length measuring sensor 45 to the subscriber side device 11 is raised to a predetermined signal level V1 at time t0. The reception signal of the line length measurement sensor 45 is raised to the signal level V1 at time t0 by the wraparound of the transmission signal. The step signal transmitted from the line length measuring sensor 45 to the subscriber side device 11 is reflected by the subscriber side device 11 and returned. In response to the reflected wave reaching the station side device 1 at time t1, the reception signal of the line length measurement sensor 45 is further raised to the signal level V2 (> V1). The line length measurement sensor 45 calculates the line length L11 of the subscriber side device 11 by measuring the propagation time (t1-t0) from when the step signal is transmitted to when the reflected wave is received.

  FIG. 5 is a time chart for explaining the operation when TDR measurement is performed using a pulse signal. Referring to FIG. 5, the pulse signal transmitted from line length measurement sensor 45 to subscriber side device 11 is raised to a predetermined signal level V1 at time t0, and is lowered to a low level after a lapse of a predetermined time. The reception signal of the line length measurement sensor 45 is raised to the signal level V1 at time t0 by the wraparound of the transmission signal, and is lowered to the low level after a predetermined time has elapsed. The pulse signal transmitted from the line length measuring sensor 45 to the subscriber side device 11 is reflected by the subscriber side device 11 and returned. In response to the arrival of the reflected wave at time t1, the reception signal of the line length measurement sensor 45 is raised to the signal level V3 (≦ V1). The line length measurement sensor 45 calculates the line length L11 of the subscriber side device 11 by measuring the propagation time (t1-t0) from when the pulse signal is transmitted to when the reflected wave is received.

  Returning to FIG. 3, the measurement signal transmitted from the line length measurement sensor 45 to the subscriber side device 12 is reflected by a bridge tap (branch point) in front of the subscriber side device 12 and returns. Thus, when the bridge tap exists in the middle of the telephone line, the line length from the station side device 1 to the bridge tap is measured, and the line length from the station side device 1 to the subscriber side device 12 is accurately determined. May not be measured.

  However, in general, a modular for connecting a telephone, a FAX, a modem, and the like is installed inside each room, and thus a bridge tap often exists near a subscriber side device. Therefore, even when a bridge tap exists in the middle of the telephone line, the measurement error of the line length is small and does not cause a problem.

  In the TDR measurement, when the subscriber side apparatus is not connected to the telephone line, the line length is measured by using the reflected wave generated at the terminal line (subscriber side apparatus side) of the opened telephone line. . Similarly, when the power supply of the subscriber side device connected to the telephone line is turned off, the line length is measured by using the reflected wave generated at the end of the telephone line. On the other hand, when the power of the subscriber-side device connected to the telephone line is turned on, if the impedance of the telephone line matches the impedance of the subscriber-side device, the reflected wave generated at the end of the telephone line May be smaller.

  In general, however, it is rare that the impedance of the telephone line and the impedance of the subscriber-side device are closely matched, and in most cases, a reflected wave is generated. Therefore, the line length of the telephone line can be measured without any problem regardless of the connection state of the subscriber side device and the on / off state of the power source.

  Returning to FIG. 2, the line lengths L11 to L13,... Measured by the line length measurement sensor 45 are stored in the storage circuit 46, respectively. The control circuit 43 sets the PBO reference length LR1 of the station side device 1 based on the line lengths L11 to L13,... Stored in the storage circuit 46.

  FIG. 6 is a diagram for explaining the setting operation of the PBO reference length. 6, the power spectrum density (PSD) of the transmission power of the subscriber side devices 11 to 13,... And the power spectrum density of the power received by the station side device 1 from the subscriber side devices 11 to 13,.

  For example, the control circuit 43 sets the longest line length among the line lengths L11 to L13,... As the PBO reference length LR1. Uplink transmission power control is performed for a subscriber side apparatus corresponding to a line length of PBO reference length LR1 or less. That is, in this case, it is performed for all the subscriber side devices. By this uplink transmission power control, the transmission power of the subscriber side device of the short-distance line is suppressed, and the power received by the station side device 1 from the subscriber side device corresponding to the line length equal to or shorter than the PBO reference length LR1 is equalized. . As a result, the influence of far-end crosstalk is reduced, and a decrease in the communication speed of the long-distance line is suppressed.

  Here, the longer the PBO reference length LR1, the wider the range of application of uplink transmission power control, and the lower the power received by the station side device 1 from the subscriber side devices 11 to 13,. For this reason, the influence of floor noise (background noise) is increased, the SN ratio (signal to noise ratio) is deteriorated, and the communication speed of the short-distance line is reduced. On the other hand, the shorter the PBO reference length LR1, the narrower the range of application of uplink transmission power control, and the influence of far-end crosstalk cannot be alleviated, and the communication speed of the long-distance line decreases.

  Therefore, an upper limit value and a lower limit value are provided so that the PBO reference length LR1 is set within an appropriate range. As a result, even when a measurement error occurs and the measured longest line length is abnormally long (for example, 1000 m), the PBO reference length LR1 is within an appropriate range if an upper limit value (for example, 500 m) is provided. Set by. Further, by setting a lower limit value based on the PSD mask value (the mask value of the power spectral density PSD that defines the power limit of the transmission signal in a specific frequency band) shown in the ITU-T recommendation “G.993.1”. , PBO reference length LR1 is set within an appropriate range.

  Here, in the standard VDSL system, a frequency band of 12 MHz or less is divided into four bands and used for data communication. For example, in correspondence with uplink and downlink data communications, downlink band 1 (0.138 MHz to 3.75 MHz), uplink band 1 (3.75 MHz to 5.2 MHz), and downlink band 2 (5.2 MHz to 8 MHz). .5 MHz) and upstream band 2 (8.5 MHz to 12 MHz) are used. The PBO reference length LR1 is individually set corresponding to each of the upstream band 1 and the upstream band 2.

  As shown in FIG. 1, when a plurality of station-side devices 1 to 3 are installed in the same building, the PBO reference lengths LR1 to LR3,. It is necessary to unify them to the same value. For example, when the station side device 1 is a master station side device, the line length information of the PBO reference lengths LR2, LR3,... Of the station side devices 2, 3,. Is done. The control circuit 43 sets the longest PBO reference length among the PBO reference lengths LR1 to LR3,... Stored in the storage circuit 46 as the common PBO reference length. The station side devices 1 to 3 perform uplink transmission power control based on the common PBO reference length. The reason for setting the common PBO reference length in this way will be described below.

  If the PBO reference lengths LR1 to LR3 of the station side devices 1 to 3 are different, the power received by the station side device having a long PBO reference length from the corresponding subscriber side device is weak. The power received by the station-side device set to a short length from the corresponding subscriber-side device becomes stronger. For this reason, the influence of far-end crosstalk cannot be alleviated, and the communication speed of the long-distance line decreases.

  Next, operations when a new subscriber service is started and when a subscriber service is suspended will be described. The storage circuit 46 further stores subscriber management information (“in service”, “not in service”, etc.) of each of the subscriber side devices 11 to 13. Based on the subscriber management information stored in the storage circuit 46, the control circuit 43 controls the operation of the station-side device 1 when a new subscriber service is started and when the subscriber service is suspended.

  FIG. 7 is a flowchart for explaining the operation when a new subscriber's service is started and when the subscriber's service is suspended. First, the operation when a new subscriber service is started will be described. In step S1, when a subscriber whose management information is “in service” is newly added, the control circuit 43 determines that the service of the new subscriber has started (YES), and proceeds to step S2. Here, the line length measurement sensor 45 performs TDR measurement of the line length of the new subscriber, and the measured line length of the new subscriber is stored in the storage circuit 46.

  In step S <b> 2, based on the line length information stored in the storage circuit 46, the control circuit 43 has the longest line length of the new subscriber among all the line lengths of all the subscribers connected to the station side device 1. Determine if it exists. When the line length of the new subscriber is the longest (YES), the process proceeds to step S3, and the control circuit 43 updates the PBO reference length held in the storage circuit 46. However, when the line length of the new subscriber exceeds the upper limit shown in FIG. 6, the PBO reference length is not updated. If the line length of the new subscriber is not the longest (NO), the PBO reference length is not updated.

  In step S3, when the PBO reference length is updated, for example, the link between the station side device 1 and the subscriber side devices 11-13,... Is forcibly disconnected once to update the PBO reference length, and the new PBO reference length is updated. The link between the station side device 1 and the subscriber side devices 11 to 13,... Is reestablished using the length, and the service is resumed. As a result, when the service of the new subscriber is started, the PBO reference length is quickly updated for all the subscriber side devices 11 to 13,. In this case, however, the service is stopped for a certain period of time for the subscriber side devices 11 to 13,.

  Therefore, the PBO reference length may be updated without stopping the service for the subscriber side devices 11 to 13,. For example, for each existing subscriber side device, when each link is reestablished (when resetting, when the service is temporarily suspended, or when the link is disconnected due to abnormal noise mixing), The PBO reference length is updated as appropriate. Moreover, you may update PBO reference | standard length, without cut | disconnecting a link with respect to all the existing subscriber side apparatuses 11-13, .... In this case, the level of transmission power of the subscriber side device changes instantaneously while the service is continued.

  Next, the operation when the service of the subscriber is suspended will be described. In step S1, the control circuit 43 determines that the service of the subscriber has been suspended when the management information of a subscriber has been changed from “in service” to “in suspension” (YES), and proceeds to step S2. .

  In step S2, the control circuit 43, based on the line length information stored in the storage circuit 46, sets all the line lengths of the subscriber side devices deleted along with the suspension of service to the station side device 1. It is determined whether it is the longest line length of the subscriber side device. When the line length of the subscriber who has suspended the service is the longest (YES), the process proceeds to step S3, and the control circuit 43 updates the PBO reference length held in the storage circuit 46. However, the PBO reference length is not updated when the line length of the subscriber who has suspended the service exceeds the upper limit shown in FIG. Further, when the line length of the subscriber who has suspended the service is not the longest (NO), the PBO reference length is not updated. The operation of updating the PBO reference length in step S3 is the same as the operation when the service of the new subscriber described above is started.

  As described above, in the first embodiment, the line length of each telephone line is measured regardless of the connection state of the subscriber-side device and the power on / off state, and is optimal for each service area from the line length information. The correct PBO reference length is automatically determined. Also, the PBO reference length is automatically updated when a new subscriber service is started and when a subscriber service is suspended. Therefore, the uplink transmission power of the subscriber side device is automatically adjusted to an optimum level.

  Here, the case where the longest line length is set to the PBO reference lengths LR1 to LR3,... In each of the station side devices 1 to 3 is described, but a predetermined distance (for example, 50 m) from the longest line length. ) May be set as the PBO reference length.

  Alternatively, the second longest line length may be set as the PBO reference length. This method is particularly effective when only the longest line length is extremely longer than other line lengths.

  Further, the average value and standard deviation of the line length may be obtained, and the PBO reference length may be set using a statistical method. For example, the average value of the line length + (standard deviation × 2.33) may be set as the PBO reference length. In this case, the risk factor (probability that the line length is longer than the PBO reference length) is 1%. Further, the average value of the line length + (standard deviation × 1.65) may be set as the PBO reference length. In this case, the danger rate is 5%. Further, the average value of the line length + (standard deviation × 1.280) may be set as the PBO reference length. In this case, the danger rate is 10%. Further, the average value of the line length + (standard deviation × 0.840) may be set as the PBO reference length. In this case, the danger rate is 20%.

  Further, here, a case has been described in which the control circuit 43 sets the longest PBO reference length as the common PBO reference length among the PBO reference lengths LR1 to LR3 of each of the station side devices 1 to 3. The circuit 46 receives line length information (line lengths L11 to L13, L21 to L23, L31 to L33,...) Of the station side devices 1 to 3 through the interface 47, and the control circuit 43 receives the line length information ( The longest line length among the line lengths L11 to L13, L21 to L23, L31 to L33,...) May be set as the common PBO reference length.

  Also, here, a case has been described where the PBO reference length is updated based on subscriber management information (such as “in service” and “not in service”) stored in the control circuit 43 or the storage circuit 46. The person in charge may update the PBO reference length by manually transmitting a command indicating the start / pause of the subscriber's service to the station apparatus 1.

  Also, here, the operation when a new subscriber's service is started and when the subscriber's service is suspended in a situation where the station-side device 1 cannot be reset has been described. However, the station-side device 1 can be reset. In some cases, the line length information may be updated by pressing the reset button and re-measuring all the subscriber's line lengths.

[Modification of Embodiment 1]
FIG. 8 is a block diagram showing the configuration of the station side apparatus 1 and the subscriber side apparatus 71 according to a modification of the first embodiment of the present invention, and is a figure compared with FIG. Referring to the subscriber side device 71 in FIG. 8, the difference from the subscriber side device 11 in FIG. 2 is that a switch circuit 72 is added. In FIG. 8, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The switch circuit 72 is connected between the hybrid circuit 64 and the terminal 67, and its operation is controlled by the control circuit 63. When the line length measurement sensor 45 of the station side device 1 measures the line length corresponding to the subscriber side device 11, the control circuit 63 opens the switch circuit 72 for a predetermined time.

  As a result, when the power of the subscriber side device 71 is turned on, the switch circuit 72 is opened even if the impedance of the telephone line and the impedance of the subscriber side device 71 are strictly matched. Accordingly, a reflected wave is surely generated. The other subscriber side devices have the same configuration as the subscriber side device 71 and operate in the same manner. Therefore, in the modification of the first embodiment, the line length of each telephone line is reliably measured even when the power supply of the subscriber side device is turned on.

  Here, the case where the switch circuit 72 is provided in the subscriber side device 71 has been described. However, the control circuit 63 does not provide the switch circuit 72, and the control circuit 63 performs the analog circuit portion (amplification) of the subscriber side device 71 when measuring the line length. The power supply to the circuit or the like may be controlled to be forcibly cut off for a certain period of time. In this case, the same effect can be obtained.

[Another modification of the first embodiment]
FIG. 9 is a block diagram showing configurations of the station side device 81 and the subscriber side device 11 according to another modification of the first embodiment of the present invention, and is a diagram to be compared with FIG. Referring to the station side device 81 in FIG. 9, the difference from the station side device 1 in FIG. 2 is that a connection determination sensor 82 is added. 9, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The connection determination sensor 82 monitors whether a telephone line is connected to the terminal 48. When a new telephone line is connected to the terminal 48, the connection determination sensor 82 determines that the service of the new subscriber has started, and when the telephone line connected to the terminal 48 is removed, the service of the subscriber is determined. Is determined to have been paused. The determination result of the connection determination sensor 82 is stored in the storage circuit 46. The control circuit 43 updates the line length information such as the PBO reference length based on the determination result stored in the storage circuit 46. The connection determination sensor 82 monitors the connection state of the telephone lines of all the subscriber side devices provided corresponding to the station side device 1.

  Therefore, in another modification of the first embodiment, the subscriber management information (such as “in service” and “not in service”) may not be stored in the storage circuit 46 as shown in the first embodiment. Based on the connection state of the telephone line (station side device side), the start / pause of the service of the subscriber is detected, and the PBO reference length update operation is performed. Thus, the PBO reference length is automatically updated when a new subscriber service is started and when the subscriber service is suspended.

[Still another modification of the first embodiment]
FIG. 10 is a block diagram showing configurations of the station side device 91 and the subscriber side device 11 according to still another modification of the first embodiment of the present invention, and is a diagram to be compared with FIG. Referring to the station side device 91 in FIG. 10, the difference from the station side device 1 in FIG. 2 is that a counter 92 is added. 10, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The counter 92 counts time in a state where the station side device 1 is operating. The control circuit 43 is connected to the telephone lines of all the subscriber side devices provided corresponding to the station side device 1 in response to the counter 92 counting a predetermined time (for example, 24 hours, 168 hours, etc.). The length is measured again, and the line length information such as the PBO reference length is updated.

  Therefore, in yet another modification of the first embodiment, it is not necessary to monitor the service state of the subscriber as shown in the first embodiment, and the line length information such as the PBO reference length is automatically updated at a predetermined cycle. Updated to

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram which shows schematic structure of the communication system by Embodiment 1 of this invention. It is a block diagram which shows the structure of the station side apparatus and subscriber side apparatus which were shown in FIG. It is a figure for demonstrating TDR measurement. It is a time chart for demonstrating operation | movement in the case of performing TDR measurement using a step signal. It is a time chart for demonstrating operation | movement in the case of performing TDR measurement using a pulse signal. It is a figure for demonstrating the setting operation | movement of PBO reference length. It is a flowchart for demonstrating operation | movement when a new subscriber's service is started and a subscriber's service is suspended. It is a block diagram which shows the structure of the station side apparatus and subscriber side apparatus by the example of a change of Embodiment 1 of this invention. It is a block diagram which shows the structure of the station side apparatus by the other modification of Embodiment 1 of this invention, and a subscriber side apparatus. It is a block diagram which shows the structure of the station side apparatus by the further another modification of Embodiment 1 of this invention, and a subscriber side apparatus. It is a block diagram which shows schematic structure of the conventional communication system using a VDSL system. It is a figure which shows the relationship between the reception power of a station side apparatus, and the transmission power of a subscriber side apparatus.

Explanation of symbols

  1, 2, 3, 81, 91, 101 Station side device, 11-13, 21-23, 31-33, 71, 111-113 Subscriber side device, 41, 61 Input buffer, 42 Modulator / Demodulator, 43, 63 Control circuit, 44, 66 output buffer, 45 line length measurement sensor, 46 storage circuit, 47 interface, 48, 67 terminals, 51, 62 modulator, 52, 64 hybrid circuit, 53, 65 demodulator, 72 switch circuit, 82 Connection determination sensor, 92 counter.

Claims (15)

A station side device that performs data communication with a plurality of subscriber side devices using a telephone line,
A measurement sensor that provides a measurement signal to each of a plurality of telephone lines provided corresponding to the plurality of subscriber-side devices, and measures a line length of each telephone line using a reflected wave of the measurement signal;
A storage circuit that stores the line length of each telephone line measured by the measurement sensor as line length information; a reference length is set based on the line length information stored in the storage circuit; A station-side device comprising a control circuit that controls transmission power of each subscriber-side device so that the power received by the station-side device from each subscriber-side device corresponding to the length is the same.   The station-side device according to claim 1, wherein the control circuit sets the reference length based on a longest line length included in the line length information stored in the storage circuit.   The station-side device according to claim 1, wherein the control circuit sets the reference length within a range of a predetermined upper limit value and lower limit value.   The control circuit sets the reference length corresponding to each of the plurality of frequency bands when a plurality of frequency bands are used in data communication from each subscriber side device to the station side device. The station side apparatus in any one of Claim 1 to 3.   5. The station-side device according to claim 1, wherein the control circuit updates the reference length when a subscriber-side device is added or deleted. The storage circuit further stores management information for managing whether each of the plurality of subscriber-side devices is receiving a data communication service,
6. The station side device according to claim 5, wherein the control circuit determines addition or deletion of a subscriber side device based on the management information stored in the storage circuit. Furthermore, a determination sensor for determining whether or not each telephone line provided corresponding to each subscriber side device is connected to the station side device,
The station-side device according to claim 5, wherein the control circuit determines addition or deletion of a subscriber-side device based on a determination result by the determination sensor.   When the subscriber side device is added or deleted, the control circuit forcibly stops the data communication with all the subscriber side devices and then updates the reference length to update all the subscriber units. The station side apparatus in any one of Claim 5 to 7 which restarts data communication with the side apparatus.   The control circuit updates the reference length while continuing data communication with all the subscriber side devices when the addition and deletion of the subscriber side devices are performed. The station side apparatus in any one.   When a new subscriber-side device is added, the control circuit starts data communication using the updated reference length for the added subscriber-side device, and all other subscriber-side devices When the data communication is temporarily stopped and restarted, the reference length is updated. When the subscriber side device is deleted, the data communication is performed for each of all the subscriber side devices. The station-side device according to any one of claims 5 to 7, wherein the reference length is updated when it is temporarily stopped and restarted. In addition, it has a counter that counts time,
5. The control circuit according to claim 1, wherein the control circuit periodically updates the reference length for all subscriber-side devices each time a predetermined time is counted by the counter. 6. The station side apparatus as described in. A plurality of the station side devices according to any one of claims 1 to 11 connected to each other,
A communication system in which the reference length common to the plurality of station-side devices is set based on the line length information of each of the plurality of station-side devices. A communication system comprising: the station side device according to any one of claims 1 to 11; and the plurality of subscriber side devices that perform data communication with the station side device.   The plurality of subscriber side devices each include a switch circuit that disconnects a connection with a corresponding telephone line for a predetermined time when the measurement sensor of the station side device performs line length measurement. Communication system. A communication method for performing data communication between a station side device and a plurality of subscriber side devices using a telephone line,
A first step of providing a measurement signal to each of a plurality of telephone lines provided corresponding to the plurality of subscriber side devices, and measuring a line length of each telephone line using a reflected wave of the measurement signal;
A second step of holding the line length of each telephone line measured in the first step as line length information, and setting a reference length based on the line length information held in the second step; Including a third step of controlling transmission power of each subscriber-side device so that power received by the station-side device from each subscriber-side device corresponding to a line length equal to or shorter than the reference length is the same. Method.

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