JP4382691B2 - ADSL modem device - Google Patents

Description

  The present invention relates to an ADSL modem apparatus that connects an ADSL (Asymmetric Digital Subscriber Line) line and a terminal such as a personal computer as a WAN (Wide Area Network) interface.

  In general, a data communication method in an ADSL line is to perform communication by assigning bits to a carrier wave (bin) determined every 4.3125 kHz. In the bit allocation method, the line attenuation and noise of the line are measured by transmitting and receiving a signal called training between the station side and the terminal side that perform communication before the start of communication, and based on the measurement result. The number of bits to be assigned to each carrier is determined.

  However, when non-stationary noise other than the noise confirmed during training is applied after synchronization of the ADSL line is established, a line error occurs on the ADSL line due to the non-stationary noise. Due to the line error, data retransmission in data communication occurs, thereby degrading the line performance.

Therefore, a threshold is set for the frequency of occurrence of line errors, and when the frequency of occurrence of line errors exceeds the threshold, the overall speed is reduced by halving the number of communication subchannels, resulting in the occurrence of line errors. There has been considered a method of suppressing the frequency and retransmission of data caused thereby and reducing the degradation of the performance of the line (for example, see Patent Document 1).
JP 2002-280998 A

  However, in the method described in Patent Document 1, when the frequency of occurrence of a line error exceeds a predetermined threshold, the number of subchannels that can be used for communication is halved. Therefore, there is a problem that the communication speed is greatly reduced in order to suppress the frequency of occurrence of errors.

  The present invention has been made in view of the problems of the prior art as described above, and minimizes degradation of line performance even when non-stationary noise occurs on the ADSL line. It is an object of the present invention to provide an ADSL modem apparatus that can be reduced to the above.

In order to achieve the above object, the present invention provides:
An ADSL modem device for connecting a terminal to a station side ADSL line terminator for terminating an ADSL line at the station side,
The frequency of occurrence of a line error detected on the ADSL line with the station side ADSL line terminator is monitored, and when the occurrence frequency is equal to or higher than a preset threshold , bit allocation to the ADSL line The number of allocated bits is reduced, it is determined whether data communication is being performed on the ADSL line, and if it is determined that data communication is not being performed on the ADSL line, the ADSL line is disconnected. Then, resynchronization is performed at the line speed at which the reduced number of allocated bits is allocated, and the ADSL line is connected.

Further, the error conversion means for monitoring the frequency of occurrence of the line error and determining whether the frequency of occurrence is equal to or higher than a preset threshold value;
When the error conversion means determines that the frequency of occurrence of the line error is equal to or higher than the threshold value, forced bit allocation calculation means for reducing the number of bits allocated for bit allocation to the ADSL line;
It is determined whether or not data communication is being performed on the ADSL line. If it is determined that data communication is not being performed on the ADSL line, the ADSL line is disconnected, and the forced bit allocation calculating means And ADSL processing means for performing resynchronization at the line speed to which the reduced number of assigned bits is assigned and connecting the ADSL line.

A method for controlling an ADSL modem apparatus for connecting a terminal to a terminal ADSL line terminator that terminates an ADSL line on the station side,
A process of monitoring the frequency of occurrence of a line error detected on the ADSL line with the station-side ADSL line terminator, and determining whether the frequency of occurrence is equal to or higher than a preset threshold;
When it is determined that the frequency of occurrence of the line error is equal to or higher than the threshold, a process of reducing the number of bits allocated for bit allocation to the ADSL line;
A process for determining whether data communication is performed on the ADSL line;
A process of disconnecting the ADSL line when it is determined that data communication is not performed on the ADSL line;
Processing for re-synchronizing at the line speed to which the reduced number of allocated bits is allocated and connecting the ADSL line.

  In the present invention configured as described above, when a line error occurring on the ADSL line is detected and a line error is detected, the bit allocation to the ADSL line is controlled to be reduced.

  In this way, by controlling the bit allocation to be reduced, when non-stationary noise occurs, the line speed of the ADSL line is forcibly reduced, thereby preventing the occurrence of a line error. Thus, data retransmission caused by a line error is avoided, and a decrease in the usable bandwidth of the line is minimized.

  As described above, in the present invention, when a line error occurring on the ADSL line is detected and the line error is detected, the bit allocation to the ADSL line is reduced. Even when noise occurs, it is possible to minimize degradation of line performance.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of an ADSL modem apparatus according to the present invention.

  In this embodiment, as shown in FIG. 1, a station DSLAM (Digital Subscriber Line Access Multiplexer) device 1 which is a station side ADSL line termination device, and an ADSL modem connected to the station DSLAM device 1 via a telephone line 4 The apparatus 2 and a personal computer 3 which is a terminal connected to the ADSL modem apparatus 2 are configured. Further, the ADSL modem apparatus 2 is connected between the ADSL processing unit 10 that performs modulation / demodulation and synchronization establishment of the main signal on the ADSL line using the telephone line 4 with the station DSLAM apparatus 1 and the personal computer 3. A LAN (Local Area Network) interface unit 5 that transmits and receives data, a data control unit 6 that performs data protocol conversion between data in the ADSL processing unit 10 and data in the LAN interface unit 5, and an ADSL line An error detection unit 9 that monitors the occurrence of a line error, a timer unit 8 that measures the period at which the error detection unit 9 monitors the occurrence of a line error, and an error detection unit 9 within the time set by the timer unit 8 An error conversion unit 7 for determining whether or not the number of occurrences of the line error detected in the step is greater than or equal to a predetermined threshold; And a force bit allocation calculating unit 11 for performing control to reduce the number of allocated bits of the current bit allocation when the number of occurrences of error is determined to be equal to or greater than the threshold value.

  Hereinafter, processing of the ADSL modem apparatus 2 shown in FIG. 1 will be described.

  FIG. 2 is a flowchart for explaining processing of the ADSL modem apparatus 2 shown in FIG.

  First, when data which is a main signal transmitted from the station DSLAM apparatus 1 shown in FIG. 1 via the telephone line 4 is received by the ADSL processing unit 10 (step S1), the data is received by the ADSL processing unit 10. Whether or not a line error has occurred in the received data is monitored by the error detection unit 9 (step S2). The line error here is a CRC error of data on the ADSL line, and is detected when the error detection unit 9 performs CRC calculation processing on the data received by the ADSL processing unit 10.

  If the occurrence of a line error is not detected by the error detector 9, the line error monitoring state is restored. On the other hand, if the occurrence of a line error is detected, whether a line error equal to or greater than the threshold has occurred within a predetermined time set by the timer 8 with the preset number of line errors occurring as a threshold. Whether or not the error conversion unit 7 determines is determined (step S3). Here, a threshold corresponding to the line speed of the ADSL line is set, and the error conversion unit 7 determines whether or not a line error exceeding the threshold has occurred, based on the time calculated from the threshold and the number of occurrences of the line error. Will be.

  If it is determined that a line error exceeding the threshold has not occurred, the line error monitoring state is restored. On the other hand, when it is determined that a line error equal to or greater than the threshold has occurred, the number of allocated bits set in advance by the forced bit allocation calculating unit 11 so as to decrease the line speed is output to the ADSL processing unit 10. (Step S4).

  When the number of allocated bits for reducing the line speed is input to the ADSL processing unit 10, the ADSL processing unit 10 determines whether data communication is currently being performed on the ADSL line (step S5). If it is determined that data communication is being performed, the timer unit 8 waits for a predetermined time (step S6), and then it is determined again whether data communication is being performed.

  On the other hand, if it is determined that data communication is not being performed, the line is forcibly disconnected by the ADSL processing unit 10, and resynchronization is performed at the line speed at which the number of allocated bits reduced in step S4 is allocated. The line is connected again (step S7).

  FIG. 3 is a diagram showing an image of changing the number of assigned bits assigned to each subchannel in ADSL modem apparatus 2 shown in FIG.

  As shown in FIG. 3, before changing the number of assigned bits, the number of assigned bits assigned to each subchannel of subchannel numbers 32-35 is “10”, and the number of assigned subchannel numbers 508-511 It is assumed that the number of assigned bits assigned to each subchannel is “6”.

  After that, when a line error is detected by the error detection unit 9 and it is determined that the frequency of occurrence of the detected line error is equal to or higher than a preset threshold value, each of the subchannels with subchannel numbers 32 to 35 is assigned to each subchannel. The assigned bit number “9” is assigned, and the assigned bit number “5” is assigned to each of the subchannels of the subchannel numbers 508 to 511, thereby reducing the communication speed of the line.

  FIG. 4 shows the threshold value of the number of occurrences of line errors for reducing the number of assigned bits and the number of assigned bits set when a line error exceeding the threshold value occurs in the ADSL modem apparatus 2 shown in FIG. It is a flowchart for demonstrating the process in case two or more are set.

  First, when data that is a main signal transmitted from the station DSLAM device 1 via the telephone line 4 is received by the ADSL processing unit 10 (step S11), a line is connected to the data received by the ADSL processing unit 10. Whether or not an error has occurred is monitored by the error detection unit 9 (step S12). The line error here is a CRC error of data on the ADSL line, and is detected when the error detection unit 9 performs CRC calculation processing on the data received by the ADSL processing unit 10.

  If the occurrence of a line error is not detected by the error detector 9, the line error monitoring state is restored. On the other hand, if the occurrence of a line error is detected, whether or not a line error exceeding the threshold has occurred within a predetermined time set by the timer unit 8 is set as a threshold. The conversion unit 7 determines (Step S13). Let X be the threshold at this time.

  When it is determined that a line error equal to or greater than the threshold value X has not occurred, the line error monitoring state is restored. On the other hand, when it is determined that a line error equal to or greater than the threshold value X has occurred, a line error equal to or greater than the threshold value is generated with the preset number of times set as a threshold value within a predetermined time set in advance by the timer unit 8. It is determined in the error conversion unit 7 whether or not it is (step S14). The threshold value at this time is Y. Regarding the threshold value X and the threshold value Y, the threshold value Y is larger than the threshold value X.

  When it is determined that a line error equal to or greater than the threshold Y has not occurred, the number of allocated bits set in advance by the forced bit allocation calculation unit 11 so as to decrease the line speed is output to the ADSL processing unit 10. (Step S15). The number of assigned bits set at this time is L, and the line speed based on the set number of assigned bits L is a.

  On the other hand, when it is determined that a line error equal to or greater than the threshold Y has occurred, a line error equal to or greater than the threshold occurs with the preset number of times as a threshold within a predetermined time preset by the timer unit 8. It is determined in the error conversion unit 7 whether or not it is being performed (step S16). Let the threshold at this time be Z. Regarding the threshold value Y and the threshold value Z, the threshold value Z is larger than the threshold value Y.

  When it is determined that a line error of the threshold value Z or higher has not occurred, the number of allocated bits set in advance by the forced bit allocation calculation unit 11 so as to reduce the line speed is output to the ADSL processing unit 10. (Step S17). The number of assigned bits set at this time is M, and the line speed based on the set number of assigned bits M is b.

  On the other hand, when it is determined that a line error equal to or greater than the threshold value Z has occurred, the number of assigned bits set in advance by the forced bit assignment calculation unit 11 so as to reduce the line speed is output to the ADSL processing unit 10. (Step S18). The number of assigned bits set at this time is N, and the line speed based on the assigned number of assigned bits N is c. Here, the relationship between the number of allocated bits L, the number of allocated bits M, and the number of allocated bits N is L> M> N, and the size relationship between the line speed a, the line speed b, and the line speed c is: a> b> c.

  When the number of allocated bits output from the forced bit allocation calculation unit 11 in step S15, step S17, or step S18 is input in the ADSL processing unit 10, data communication is currently performed on the ADSL line. It is determined by the ADSL processing unit 10 (step S19). If it is determined that data communication is being performed, the timer unit 8 waits for a predetermined time (step S20), and then it is determined again whether data communication is being performed.

  On the other hand, if it is determined that data communication is not being performed, the line is forcibly disconnected by the ADSL processing unit 10, and the line to which the number of allocated bits reduced in step S15, step S17, or step S18 is allocated. Resynchronization is performed at the speed, and the line is connected again (step S21).

  In this way, it is first determined whether or not a line error equal to or higher than the threshold has occurred using a threshold having a low occurrence frequency. It is determined until it is determined that a line error exceeding the threshold has not occurred by using a threshold having a high frequency of occurrence and determining whether a line error exceeding the threshold has occurred. The line error occurrence frequency is determined based on a plurality of thresholds, and when it is determined that no line error exceeding the threshold value has occurred, the line speed is determined accordingly. Thus, a more suitable line speed is set.

  The type of threshold value for the frequency of occurrence of line errors is not limited. Further, the change of the threshold value of the frequency of occurrence of line errors can be changed at any time.

It is a figure which shows one Embodiment of the ADSL modem apparatus of this invention. It is a flowchart for demonstrating the process of the ADSL modem apparatus shown in FIG. It is a figure which shows the image of the change of the number of allocation bits allocated to each subchannel in the ADSL modem apparatus shown in FIG. In the ADSL modem apparatus shown in FIG. 1, a plurality of line error occurrence threshold values for reducing the number of assigned bits and a plurality of assigned bit numbers set when a line error exceeding the threshold value is set. It is a flowchart for demonstrating the process of.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Station DSLAM apparatus 2 ADSL modem apparatus 3 Personal computer 4 Telephone line 5 LAN interface part 6 Data control part 7 Error conversion part 8 Timer part 9 Error detection part 10 ADSL processing part 11 Compulsory bit allocation calculation part

Claims (3)

An ADSL modem device for connecting a terminal to a station side ADSL line terminator for terminating an ADSL line at the station side,
The frequency of occurrence of a line error detected on the ADSL line with the station side ADSL line terminator is monitored, and when the occurrence frequency is equal to or higher than a preset threshold , bit allocation to the ADSL line The number of allocated bits is reduced, it is determined whether data communication is being performed on the ADSL line, and if it is determined that data communication is not being performed on the ADSL line, the ADSL line is disconnected. An ADSL modem apparatus that performs resynchronization at the line speed to which the reduced number of allocated bits is allocated, and connects the ADSL line. The ADSL modem apparatus according to claim 1, wherein
Error conversion means for monitoring the frequency of occurrence of the line error and determining whether the frequency of occurrence is equal to or higher than a preset threshold;
When the error conversion means determines that the frequency of occurrence of the line error is equal to or higher than the threshold value, forced bit allocation calculation means for reducing the number of bits allocated for bit allocation to the ADSL line;
It is determined whether or not data communication is being performed on the ADSL line. If it is determined that data communication is not being performed on the ADSL line, the ADSL line is disconnected, and the forced bit allocation calculating means An ADSL modem apparatus comprising: ADSL processing means for performing resynchronization at a line speed to which the reduced number of assigned bits is assigned, and connecting the ADSL line. A method for controlling an ADSL modem apparatus for connecting a terminal to an ADSL line terminator that terminates an ADSL line at the station side, and a terminal,
A process of monitoring the frequency of occurrence of a line error detected on the ADSL line with the station-side ADSL line terminator, and determining whether the frequency of occurrence is equal to or higher than a preset threshold;
When it is determined that the frequency of occurrence of the line error is equal to or higher than the threshold, a process of reducing the number of bits allocated for bit allocation to the ADSL line;
A process for determining whether data communication is performed on the ADSL line;
A process of disconnecting the ADSL line when it is determined that data communication is not performed on the ADSL line;
A method of controlling an ADSL modem apparatus, comprising: resynchronizing at a line speed to which the reduced number of allocated bits is allocated and connecting the ADSL line.

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