1、 ETSI TR 102 930 V1.1.1 (2010-09)Technical Report PowerLine Telecommunications (PLT);Study on signal processingimproving the coexistence of VDSL2 and PLTETSI ETSI TR 102 930 V1.1.1 (2010-09) 2Reference DTR/PLT-00030 Keywords emission, powerline ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Ce
2、dex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-Prfecture de Grasse (06) N 7803/88 Important notice Individual copies of the present document can be downloaded from: http:/www.etsi.org The present docum
3、ent may be made available in more than one electronic version or in print. In any case of existing or perceived difference in contents between such versions, the reference version is the Portable Document Format (PDF). In case of dispute, the reference shall be the printing on ETSI printers of the P
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5、us.asp If you find errors in the present document, please send your comment to one of the following services: http:/portal.etsi.org/chaircor/ETSI_support.asp Copyright Notification No part may be reproduced except as authorized by written permission. The copyright and the foregoing restriction exten
6、d to reproduction in all media. European Telecommunications Standards Institute 2010. All rights reserved. DECTTM, PLUGTESTSTM, UMTSTM, TIPHONTM, the TIPHON logo and the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members. 3GPPTM is a Trade Mark of ETSI registered for the ben
7、efit of its Members and of the 3GPP Organizational Partners. LTE is a Trade Mark of ETSI currently being registered for the benefit of its Members and of the 3GPP Organizational Partners. GSM and the GSM logo are Trade Marks registered and owned by the GSM Association. ETSI ETSI TR 102 930 V1.1.1 (2
8、010-09) 3Contents Intellectual Property Rights 4g3Foreword . 4g3Introduction 4g31 Scope 5g32 References 5g32.1 Normative references . 5g32.2 Informative references 5g33 Abbreviations . 6g34 Analysis of the electromagnetic coupling between PLC and VDSL2 links . 6g34.1 Executive summary about the anal
9、ysis . 6g34.2 First consideration 7g34.3 Reference configuration . 7g34.4 Power Injected between two PLT modems 7g34.5 Theoretical approach 8g34.5.1 Coupling to aerial cables . 8g34.5.2 Synthesis processing . 10g34.6 Summary of the results . 10g34.6.1 Untwisted Telecom wires . 10g34.6.2 Twisted wire
10、s (CAT3) 11g34.6.3 Twisted wires (CAT5) 12g34.7 Examples of theoretical results . 12g35 Algorithms to allow the coexistence of PLT with VDSL2 15g35.1 Executive summary about the algorithms 15g35.2 Problem statement 15g35.3 Analysis of the PHY layers of PLT and VDSL2 15g35.4 Channel Coupling Model fo
11、r Signal Processing 16g35.5 Method 1: Adaptive interference cancelling filter 17g35.6 Method 2: Spectral management 18g36 PLT implementation of coexistence algorithms . 19g36.1 Executive summary 19g36.2 Operating Principle. 20g36.3 End-user Coexistence Tool. 20g36.4 Installer Tool 21g36.5 Service Pr
12、ovider Tool . 23g37 Crosstalk measurements in real houses 24g37.1 Executive summary 24g37.2 Measurements . 24g38 Effect of the mitigation on a VDSL2 system . 28g38.1 Executive summary 28g38.2 Measurements . 28g39 Conclusions 30g3Annex A: Bibliography 32g3History 35g3ETSI ETSI TR 102 930 V1.1.1 (2010
13、-09) 4Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI SR 000 314: “Intellectual Pr
14、operty Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/webapp.etsi.org/IPR/home.asp). Pursuant to the ETSI IPR Policy, no investigation, i
15、ncluding IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Foreword This Technical Report (TR) has b
16、een produced by ETSI Technical Committee Powerline Telecommunications (PLT). Introduction The current solution for the IPTV market is based on ADSL link from the TELCO office to the customer premises, an ADSL gateway at the customer premise to decode the signal, and a home network to distribute the
17、signal within the house. The next generation of broadband access, currently being deployed by European TELCOs, is based on VDSL2 technology. On the other hand, powerline technology is becoming the preferred solution for home networking when applications, such as IPTV, requiring high throughput and Q
18、oS are provided. However, both technologies, VDSL2 and PLT, use the same frequency band (2 MHz to 30 MHz), and several studies (i.6 and i.7) predict the interference of PLT modems over VDSL2 systems. To confirm these predictions the ETSI PLT group conducted a Plugtest where the level of interference
19、 between both technologies was measured, and set up a Specialist Task Force with the following assignments: 1) to analyze the severity of the interference; and 2) to propose solutions to mitigate it. The present document presents the result of the STF. ETSI ETSI TR 102 930 V1.1.1 (2010-09) 51 Scope
20、The present document presents the result of the work of the STF and suggests the methods and practices to reduce or mitigate the crosstalk between electricity and telephone cables. The present document also includes the results of a small measurement campaign in real housed aimed at confirming the r
21、esults of the Plugtest and validating the mitigation methods. The work was organised in three phases assigned to different STF members: Phase 1: Modelling the coupling channel between VDSL2 and PLT (clause 4). Phase 2: Simulations of signal processing algorithms for coexistence (clause 5). Phase 3:
22、Implementation of the algorithms in PLT devices (clause 6); field measurements (clause 7) and laboratory validation (clause 8). 2 References References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For specific references, only the c
23、ited version applies. For non-specific references, the latest version of the reference document (including any amendments) applies. Referenced documents which are not found to be publicly available in the expected location might be found at http:/docbox.etsi.org/Reference. NOTE: While any hyperlinks
24、 included in this clause were valid at the time of publication ETSI cannot guarantee their long term validity. 2.1 Normative references The following referenced documents are necessary for the application of the present document. Not applicable. 2.2 Informative references The following referenced do
25、cuments are not necessary for the application of the present document but they assist the user with regard to a particular subject area. i.1 “Analysis of Multiconductor Transmission Lines“, C.R. Paul. John Wiley this observation is correlated to the coupling factor between DSL lines in a same cable.
26、 In the following clause 5.5, H(f) is the transfer function, based on the PLT and VDSL2 channel coupling model (Figure 10), expressed as a matrix. The following equations describe the coupling process between VDSL2 signal X1and PLT signal X2as linear mixing of signals with additive gaussian noise: 2
27、222121212121111nXhXhYnXhXhY+=+=Equation (5) The input signals are X1for VDSL2 and X2for PLT and output signals (the ones actually received by the modems) are Y1for VDSL2 modem and Y2for PLT modem. 5.5 Method 1: Adaptive interference cancelling filter The present method relates to a cancellation filt
28、er to suppress the interference of a PLT signal carried by a power distribution network in the user premises to the VDSL signal carried by a telephone system that is located close to some power cable. The method is based on feeding the signal carried by the power network to the adaptive filter in or
29、der to obtain an estimate of the PLT signal that couples on the telephone line. The estimated signal is then subtracted from the signal carried by the telephone line. This estimation is based on minimization of mean square error and following equation are classical for estimation of original signals
30、 (X1, X2) from linear combination of corrupted data (Y1, Y2). ()= 21121YYHHHXXTTeach gain step corresponds to 6 dB. There is a conversion factor (67) that includes the calibration of the AFE in order to produce the result in true dBm/Hz. Finally Attiis the attenuation in dB that should be applied to
31、 the PLT carrier under consideration. The installer has the possibility to confirm that the calculated power mask produces the expected result by performing a second acquisition of the crosstalk level. If the mitigation is correct, the crosstalk curve will look flat in the downstream bands, as shown
32、 in Figure 16. ETSI ETSI TR 102 930 V1.1.1 (2010-09) 23Figure 16: Crosstalk profile after the mitigation has been applied 6.5 Service Provider Tool When the Service Provider or Telecom Operator detects a problem with the VDSL2 link that could be due to the PLT modems, there are ways to remotely chec
33、k the coupling level and change the PLT spectrum. The measurement of the crosstalk level is done indirectly by checking the noise margin of the VDSL2 downstream bands. The operator may need to ask the customer to plug and unplug the PLT modems in order to evaluate the effect on the VDSL2 link. The v
34、ariation in the noise margin indicates the amount of attenuation required on the PLT spectrum to prevent the adverse effects. The method to obtain this information from the DSLAM is not covered in this document. The adjustment of the PLT spectrum can be done remotely using the TR-69 protocol that is
35、 supported in UPA-compatible PLT chips Aitana and Aitana+ running Spirit 4.8 or higher. The RPC method to change the spectrum of the PLT modems is the Download method described in clause A.3.2.8 of the TR-069 Specification i.10. This method allows the modem to download a vendor-specific configuratio
36、n file containing the amplitude values of all the OFDM carriers. The download of this file is started from the ACS. Figure 17 shows a screenshot of the Work Systems ACS interface that controls the download of the configuration file to a PLT modem. The automation of this process requires a script tha
37、t is able to read the noise margin data from the DSLAM in the vendor-specific format, correlate the frequencies of VDSL2 carriers to PLT carriers, calculate the attenuation required for each PLT carrier and download the configuration file to the modem using TR-69 i.10. Most of the work is related to
38、 protocols and data formats, being the data processing a small piece of work. ETSI ETSI TR 102 930 V1.1.1 (2010-09) 24Figure 17: Snapshot of the Work Systems ACS interface to download the configuration file to change the PLT spectrum The main drawback of this method is that there is no special hardw
39、are as in the installer kit that allows a true-value measurement of the crosstalk from the electricity cable to the telephone cable. In addition, a turnkey solution cannot be provided due to the diversity in the formats and protocols to access the VDSL and PLT equipment. 7 Crosstalk measurements in
40、real houses 7.1 Executive summary The availability of a kit to measure the coupling between electricity and telephone cables opens an interesting opportunity to confirm the measurements performed in the Plugtest. The installer tool described in clause 6.4 allows a quick acquisition and recording of
41、this data for later analysis. This clause presents the data obtained in measurements performed in several houses in Spain and France and compares the crosstalk level between houses with co-localized cables and separate cables. 7.2 Measurements The measurements were performed plugging a PLT modem in
42、an electrical outlet and the measurement unit in a telephone outlet. For every house, 2 telephone outlets are tested in combination with 5 to 10 electrical outlets, producing 10 to 20 measurements. Each combination of an electrical outlet and a telephone outlet is called a “pair“ from now on. The in
43、staller tool records the crosstalk level measured in every OFDM carrier, producing a set of 1 536 points in the range from 2 to 30 MHz. The resulting data is tagged with the location of the electrical and telephone outlets and recorded in a text file in CSV format. The data is then processed to prod
44、uce the following results: The maximum and average crosstalk values for every pair, presented in Figure 18 for Spain and in Figure 19 for France. The first 20 readings of Figure 18 correspond to a house having 20 meters of telephone cable co-localized in the same ducts as the electrical cable. The a
45、verage crosstalk level is 7 dB higher than in the rest of the houses and the maximum level is 6 dB higher. The average crosstalk levels are between -120 dBm/Hz and -140 dBm/Hz in most of the cases. ETSI ETSI TR 102 930 V1.1.1 (2010-09) 25Crosstalk between pairs-160-140-120-100-80-60-40-2001 3 5 7 9
46、11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67Outlet pairCrosstalk (dBm/Hz)Average Maxi mum20m co-localized cableFigure 18: Crosstalk measurements between outlet pairs in Spain Crosstalk between pairs-160-140-120-100-80-60-40-2001 3 5 7 9 1 1315171921232527293
47、1333537394143454749Outlet PairPSD (dBm/Hz)Average MaximumFigure 19: Crosstalk measurement between outlet pairs in France The mean crosstalk profile as a function of frequency is presented in NOTE: The grey trend line show the dependency with frequency. Figure 20. This graph averages the crosstalk va
48、lue for all the pairs, on a carrier by carrier basis. More measurements are required to dilute the statistical dispersion, but the trend line (in grey) shows a dependency with frequency of around 0,27 dB / MHz. ETSI ETSI TR 102 930 V1.1.1 (2010-09) 26Average Crosstalk PSD-150-145-140-135-130-125-120
49、-115-1102 4 6 8 1012141618202224262830f (MHz)PSD (dBm/Hz)NOTE: The grey trend line show the dependency with frequency. Figure 20: Average level of all outlet pairs Another interesting comparison is the mean crosstalk profile of the house with co-localized cables and the rest of the houses. This comparison is presented in NOTE: The red line is a house with 20m of co-localized cable. The blue line is the average of all the other houses with installation according to regulation. Figure 21. ETSI ETSI TR 102 930 V1.1.1 (2010-09) 27Average Cros
