WO2019185539A1

WO2019185539A1 - Measurement method

Info

Publication number: WO2019185539A1
Application number: PCT/EP2019/057421
Authority: WO
Inventors: Stephen BEAUMONT
Original assignee: British Telecommunications Public Limited Company
Priority date: 2018-03-29
Filing date: 2019-03-25
Publication date: 2019-10-03

Abstract

The present invention provides a computer-implemented method of measuring the effectiveness of an intervention in a metallic access network. The effectiveness measure is determined in accordance with the improvement in the attenuation, the signal to noise ratio (SNR) and the maximum achievable data rate. The effectiveness measure is used to determine whether a further network intervention is required.

Description

MEASUREMENT METHOD

Field of the Invention

The present invention relates to a method of determining the effectiveness of an intervention in a communications network, and in particular to a method of determining the effectiveness of an intervention in a hybrid copper-fibre access network.

Background to the Invention

Since the advent of the World Wide Web, there has been a need to provide internet access to customers at ever increasing data rates. Asymmetric Digital Subscriber Line (ADSL) technology over existing copper wires can provide data rates of up to 24 Mbit/s, but some customers will experience significantly lower data rates due to the length of the network connection. One advantage of ADSL solutions is that there is no need to deploy additional infrastructure as the data signals are provided over existing copper access networks.

Figure 1 shows a schematic depiction of a copper access network 100 in which a telephone exchange 1 10 is connected to a plurality of customer premises 500 (the customer premises may be domestic, commercial or industrial premises). The telephone exchange 1 10 is connected to cabinets (sometimes referred to as primary cross-connect points [PCPs]) 120 by respective primary copper cables 1 15. Each cabinet 120 is connected to one or more distribution points 130 via respective secondary copper cables 125. A distribution point is typically connected to the customer premises 500 using a dropwire 135, via a telephone pole (not shown) or an underground route..

The testing of copper access networks to locate faults or determine whether a copper line can support telephony and/or ADSL signals is well known: see, for example the Applicant’s earlier international patent applications: W001/76208, W001/76209, W002/080505, WO201 1/151614 & WO2012/156670.

Summary of the Invention

According to a first aspect of the invention, there is provided a computer-implemented method of determining the effectiveness of an intervention on a metallic access network, the method comprising the steps of: a) determining values for the maximum achievable data rate before (MAR1 ) and after (MAR2) the intervention; b) determining values for the attenuation before (ATT1 ) and after (ATT2) the intervention; c) determining values for the signal to noise ratio before (SNR1 ) and after (SNR2) the intervention; d) determining an effectiveness score (E) for the intervention based on the determined values of maximum achievable data rate (MAR1 , MAR2), attenuation (ATT 1 , ATT2) and signal to noise ratio (SNR1 , SNR2); and e) determining whether a further intervention is required in accordance with the effectiveness score (E) determined in step d).

The effectiveness score may be determined based on i) the ratio of the maximum achievable data rate (MAR2) after the intervention to the maximum achievable data rate (MAR1 ) before the intervention; ii) the ratio of the attenuation (ATT1 ) before the intervention to the attenuation (ATT2) after the intervention; and iii) the ratio of the signal to noise ratio after the intervention (SNR2) to the signal to noise ratio before the intervention (SNR1 ).

The effectiveness score is compared with one or more predetermined threshold value: the intervention may be determined to have a negative effect if the effectiveness score is less than a first predetermined threshold value. However, the intervention may be determined to have a positive effect if the effectiveness score is greater than a second predetermined threshold value or the intervention may be determined to have a negligible effect if the effectiveness score is greater than the first predetermined threshold value and less than the second predetermined threshold value.

The values of maximum achievable data rate (MAR1 , MAR2), attenuation (ATT 1 , ATT2) and signal to noise ratio (SNR1 , SNR2) may be measured by an operational support system. Furthermore the operational support system may calculate the effectiveness score on the basis of those measured values.

According to a second aspect of the invention, there is provided a test apparatus comprising a processor, data storage and memory, wherein the test apparatus is configured to perform the method as described above.

According to a third aspect of the invention, there is provided a data carrier device comprising computer executable code for performing any of the methods as described above. Brief Description of the Figures

In order that the present invention may be better understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a schematic depiction of a hybrid fibre-copper access network; Figure 2 shows a schematic depiction of a single line from the hybrid copper-fibre access network;

Figure 3 shows a graphical depiction of the inter-relationship between the parameters used to determine an effectiveness measure; and

Figure 4 shows a graphical depiction of a flowchart describing the operation of a method according to the present invention.

Detailed Description of Embodiments

Figure 2 shows a schematic depiction of a single line from a copper access network 100, which connects the exchange building 1 10 to the customer premises 500. The connection comprises optical fibre cable 1 15, cabinet 120, copper cable 125, distribution point 130 and dropwire 135. The network 100 further comprises a plurality of operational support systems (OSSs) 200. The OSSs, amongst other functionality, store data concerning the state and/or performance of each network line and the components which constitute the network.

An OSS will store, amongst other data, a number of parameters relating to the transmission performance of each line. For example, an OSS will store for each line the data rate, the maximum achievable date rate, the attenuation and the signal to noise ratio (SNR) for both the upstream and the downstream connections. ADSL systems use a technique known as Dynamic Line Management (DLM) which assesses the performance of each ADSL circuit. DLM is used to provide the customer with as high a data rate as possible whilst minimising the number of times that the line needs to retrain due to the ADSL modem in the customer premises needing to synchronise with the DSLAM. Therefore, the use of DLM may result in an ADSL circuit being operated at a data rate which is less than the maximum achievable data rate (MAR) in order to obtain a greater degree of stability or a lower error rate. A profile will be selected which provides an appropriate balance between data rate and stability. The DLM system will observe the operation of an ADSL line for an extended period of time before selecting a profile which will be used. Therefore, if a technician makes a repair to an ADSL line it cannot be determined at the time that the repair is made what the effect of the repair is. Therefore, there is a need for a test that can be performed by a technician following a repair, or other form of intervention, which can provide an indication of the effectiveness of that intervention.

As discussed above, the OSS hold parameter values for, amongst other parameters, the data rate, the maximum achievable date rate, the attenuation and the signal to noise ratio (SNR). These four different metrics are inter-related and thus it is not possible to construct a useful performance measure based on only one of them. As the use of DLM may lead to the value of the data rate being capped in order to provide a more stable connection, the applicant has studied the maximum achievable date rate, attenuation and SNR, using historic data obtained from the OSS operated by the applicant and analysed to determine the value of a computed metric to whether:

• A repair task resulted in a repeat fault being raised or

• How the downstream data rate (measured after the DLM had settled) compared to the downstream data rate when the fault was raised

It was found that the most significant parameters for ADSL systems were the downstream maximum achievable data rate (MAR), the downstream attenuation (ATT) and the downstream signal to noise ratio (SNR). Figure 3 shows a graphical depiction of the inter-relationship between these variables, with each of the variables being assigned to one of three orthogonal axes. A measure of the performance of an ADSL line can be found from determining the area of the triangle in which the vertices are defined by a ratio determined from the respective parameter measurement values.

In the following discussion, MAR1 is the value for the downstream maximum achievable data rate before the intervention and MAR2 is the value for the downstream maximum achievable data rate after the intervention; ATT1 is the value for the downstream attenuation before the intervention and ATT2 is the value for the downstream attenuation after the intervention; and SNR1 is the value for the downstream signal to noise ratio before the intervention and SNR2 is the value for the downstream signal to noise ratio before the intervention.

Three ratios can be defined on the basis of these parameter values, namely:

SNR 2

SNR_R SNRl [1 ]

MAR2

MAR_R [2]

MARI

ATTl

ATT_R [3]

ATT2

These ratio values can be defined as the vertices of a triangle, with the each vertex being located on an axis (see Figure 3). The length of each side of the triangle can be determined in accordance with equations [4] - [6]:

Based on these lengths it is then possible to calculate the area of the triangle, E, in accordance with Heron’s formula

where s is the semiperimeter of the triangle and is given by a+b+c

s = [8]

2 The area of the triangle is the measure of effectiveness of the intervention. If the intervention reduces ADSL performance then one or more of the parameter values will be less than 1 whereas if the intervention increases ADSL performance then one or more of the parameter values will be greater than 1 and the area if the triangle will increase.

It will be noted that the ratio in equation [3] for attenuation is inverted in relation to the ratios for maximum data rate and SNR as an improvement in the attenuation will lead to a lower numerical attenuation value. By using ratios of the three parameters before and after the intervention, any influences on the parameter values which are due to the length of the line under test are removed and thus the values of effectiveness measures determined for different lines can be compared.

Rather than displaying the raw value of the effectiveness measure to a technician, the effectiveness measure value can be processed arithmetically to provide a simple numerical indication of the effectiveness of the intervention. For example, a value of zero can indicate that the intervention had effect change in ADSL performance, with a negative number indicating that the intervention decreased the ADSL performance and positive number indicating that the intervention increased the ADSL performance. The numerical values can be presented in a range, for example from -99 to +99, to allow a technician to determine the relative improvement (or decline) in performance.

Alternatively, threshold values for the effectiveness measure can be pre-determined such that the effectiveness measure calculated for a particular network repair or intervention can be compared with the effectiveness measure threshold values and the effectiveness of the intervention can be categorised. For example, by defining a lower and a higher threshold value, if a calculated effectiveness measure is less than the lower threshold then the intervention can be categorised as having a negative impact (that is, worsening the performance of the network). If the calculated effectiveness measure is greater than the upper threshold then the intervention can be categorised as having a positive impact (that is improving the performance of the network). If the calculated effectiveness measure is greater than the lower threshold but lower than the upper threshold then the intervention can be categorised as having negligible effect (that is, the network performance has not changed significantly). It will be understood that it will be possible to use a different number of thresholds in order to provide a number of different categories which can be used to describe the effects of the intervention. In a variant to the method described above, a weighting may be applied to one or more of the parameter value ratios when determining the effectiveness of a repair. In this case the weighted ratios are determined in accordance with:

„ , . _ MAR2

MAR_RW -—— X w₂ [10]

MARI

ATTl

ATT RW - X W

ATT2 ^ά [1 1 ]

These weighted parameter value ratios are then used in equations [4] - [6] to determine the length of each side of the triangle whose vertices are defined by the parameter value ratios and these length values are then used in equation [7] & [8] to determine the area of the triangle. By applying a weighting which is greater than one to a parameter value ratio then the ratio value for that parameter will have an increased effect when determining the effectiveness of the intervention. Conversely, applying a weighting which is less than one to a parameter value ratio will have a decreased effect when determining the effectiveness of the intervention. Applying a weighting of 1 to a parameter value ratio will have no effect on the determination of the effectiveness of the intervention.

Analysis of historical fault data indicates that an improvement in the attenuation is more strongly linked to an improvement in performance and a decrease in the likelihood that any further intervention is required. Consequently, a weighting of 2 may be applied to the value of ATTR. Similar analysis indicates that an improvement in the signal to noise ratio is less strongly linked to an improvement in performance. Consequently, a weighting of 0.5 may be applied to the value of SNRR.

Figure 4 shows a graphical depiction of a flowchart describing the operation of a method according to the present invention. At step S400 a fault is reported and in response a technician is assigned to investigate the fault (S420) and the most recent parameter values (for example, parameter values for the downstream maximum achievable data (MAR1 ), the downstream attenuation (ATT 1 ) and the signal to noise ratio (SNR1 ) before the intervention) are recovered (S410). The technician will use their skill and expertise to diagnose the fault and then perform an appropriate intervention (S430). Following the intervention, the parameter values (i.e. downstream maximum achievable data (MAR2), the downstream attenuation (ATT2) and the signal to noise ratio (SNR2) after the intervention) are measured again (S440) and an effectiveness measure calculated on the basis of the four parameter values (S450). An indication of the effectiveness of the intervention can then be provided to the technician (S460) who then decides at S470 if any further intervention is required (returning to S430). For example, based on the categorisation scheme described above, if the intervention is categorised as having a negative impact then the technician must perform one or more further interventions. If the intervention is categorised as having no impact then the technician should consider a different intervention as the reported fault condition may still be present. If the intervention is categorised as having a positive impact then the technician may not need to make any further intervention and thus the process can terminate (S480).

Referring to Figure 2, the measurements made after the intervention need to be made at the customer premises such that the downstream parameters can be measured properly. The technician may be provided with test apparatus 400 which is able to measure the downstream maximum achievable data (MAR2), the downstream attenuation (ATT2) and the signal to noise ratio (SNR2) after the intervention. These parameter values may be reported to the OSS 200 (for example, via a wireless data connection) such that the OSS calculates the effectiveness measure and sends a message, such as, for example, an email, SMS or MMS, to the technician to communicate the effectiveness measure. Rather than communicating the calculated value of the effectiveness measure the OSS may transmit the category which is relevant to the effectiveness of the intervention and any other further information which may assist the technician in making a further intervention.

Alternatively, when the technician is assigned the repair task, the relevant parameter values (that is the downstream maximum achievable data (MAR1 ), the downstream attenuation (ATT1 ) and the downstream signal to noise ratio (SNR1 ) before the intervention) for the line in question may be downloaded to the test apparatus 400 such that when the downstream maximum achievable data (MAR2), the downstream attenuation (ATT2) and the downstream signal to noise ratio (SNR2) are measured after the intervention the test apparatus is able to calculate the effectiveness measure, categorise the effectiveness measure and then display the relevant information to the technician.

ADSL systems are used to provide applications and services to customers which require relatively high data rates, such as streaming video, IPTV transmissions, downloads of operating systems, online gaming etc. In most cases the requirement is greater for transmitting data in the downstream direction, that is from the local exchange to the customer premises, than it is for transmitting data in the upstream direction, that is from the customer premises to the local exchange. Thus, the foregoing discussion is focussed on determining the effectiveness of an intervention based on measurements of downstream parameters made at the customer premises. However, it should be understood that it would also be possible to determine the effectiveness of an intervention based on measurements of upstream parameters made at the local exchange.

As the present invention can be implemented using an appropriately configured and programmed test apparatus, appropriate computer code may be accessed via download, for example via the internet from an ISP, or on some physical media, for example, DVD, CD-ROM, USB memory stick, etc. for which the test apparatus has an appropriate media reader.

According to one aspect, the present invention provides a computer-implemented method of measuring the effectiveness of an intervention in a metallic access network. The effectiveness measure is determined in accordance with the improvement in the attenuation, the signal to noise ratio (SNR) and the maximum achievable data rate. The effectiveness measure is used to determine whether a further network intervention is required.

Claims

1 . A computer-implemented method of determining the effectiveness of an intervention on a metallic access network, the method comprising the steps of:

a) determining values for the maximum achievable data rate before (MAR1 ) and after (MAR2) the intervention;

b) determining values for the attenuation before (ATT 1 ) and after (ATT2) the intervention;

c) determining values for the signal to noise ratio before (SNR1 ) and after (SNR2) the intervention;

d) determining an effectiveness score (E) for the intervention based on the determined values of maximum achievable data rate (MAR1 , MAR2), attenuation (ATT 1 , ATT2) and signal to noise ratio (SNR1 , SNR2); and

e) determining whether a further intervention is required in accordance with the effectiveness score (E) determined in step d).

2. A computer-implemented method according to Claim 2, wherein in step d) the effectiveness score (E) is determined based on

i) the ratio of the maximum achievable data rate (MAR2) after the intervention to the maximum achievable data rate (MAR1 ) before the intervention; ii) the ratio of the attenuation (ATT1 ) before the intervention to the attenuation (ATT2) after the intervention; and

iii) the ratio of the signal to noise ratio after the intervention (SNR2) to the signal to noise ratio before the intervention (SNR1 ).

3. A computer-implemented method according to any preceding claim wherein the effectiveness score is compared with one or more predetermined threshold value.

4. A computer-implemented method according to Claim 3, wherein the intervention is determined to have a negative effect if the effectiveness score is less than a first predetermined threshold value.

5. A computer-implemented method according to Claim 3, wherein the intervention is determined to have a positive effect if the effectiveness score is greater than a second predetermined threshold value.

6. A computer-implemented method according to Claim 3, wherein the intervention is determined to have negligible effect if the effectiveness score is greater than the first predetermined threshold value and less than the second predetermined threshold value.

7. A computer-implemented method according to any preceding Claim, wherein the values of maximum achievable data rate (MAR1 , MAR2), attenuation (ATT 1 , ATT2) and signal to noise ratio (SNR1 , SNR2) are measured by an operational support system.

8. A computer-implemented method according to Claim 7, wherein the operational support system calculates the effectiveness score on the basis of the measured values of maximum achievable data rate (MAR1 , MAR2), attenuation (ATT 1 , ATT2) and signal to noise ratio (SNR1 , SNR2).

9. A computer-implemented method according to Claim 8, wherein the calculated effectiveness score is transmitted to a mobile terminal.

10. Test apparatus comprising a processor, data storage and memory, wherein the test apparatus is configured to perform the method according to any of Claims 1 to 9.

1 1 . Test apparatus according to Claim 10, wherein the test apparatus is further configured to

i) store values for the maximum achievable data rate (MAR1 ) before the intervention, the attenuation (ATT1 ) before the intervention and the signal to noise ratio (SNR1 ) after the intervention;

ii) measure values for the maximum achievable data rate (MAR2) after the intervention, the attenuation (ATT2) after the intervention and the signal to noise ratio (SNR2) after the invention; and

iii) calculate the effectiveness score (E) based on the determined values of maximum achievable data rate (MAR1 , MAR2), attenuation (ATT 1 , ATT2) and signal to noise ratio (SNR1 , SNR2).

12. A data carrier device comprising computer executable code for performing a method according to any of Claims 1 to 9.