E M C activities. Carried out at. France Telecom

Transcription

1 E M C activities Carried out at France Telecom Ph. Lancelin A.Zeddam F.Moulin R.Razafferson R.Tarafi France Telecom R&D TTC Workshop Tokyo Orange Labs

2 Radio has no future

3 Outline I Immunity of DSL systems Impact of "Impulsive Noise on real time services II PLT Performance versus EMC standard compliance and coexistence with other services III EM disturbances in Home Network PSU lifetime problematic Coexistence between PLT and VDSL 3

4 I Immunity of xdsl systems to Impulsive Noise 4

5 Context and Problematic Impulsive Noise example and analysis Origin, coupling mechanism, statistics Impact on Real Time services (QoS) Present-day situation and investigations Action in standardisation 5

6 Context / Problematic Advanced digital processing technique & technology have made possible to enlarge the variety of applications being supported by twisted telecom pair : Remote controlled of apparatus High speed internet connection Real time applications ( Tv over DSL ) Consequence : Rapid increase of number of equipment plugged into the mains and telecom networks without Operator's control Raised of broadband noise level Drawbacks : real time applications are very sensitive to impulsive noise Up to now, present EMC standards do not consider the broadband disturbances phenomena 6

7 Origin of impulsive noise & coupling mechanism Impulsive noises generated within the customer installation come from many different sources : - periodic ( REIN : T = 10ms / PSU ) - non periodic ( electro domestic equipment, lighting, switch, motor ) - defective apparatus can generate noise levels > 20 db above standard limit Disturbances are transferred to telecom lines by EM coupling - CM disturbances are converted to DM disturbances due to unbalanced length cabling Investigation methodology Caring out of "in-situ" measurement campaigns in multiple environmental configurations - recording of more than data samples of impulsive noise (max duration 1 ms ) Characterisation & statistical analysis 7

8 Impulsive Noise example and statistical analysis Actual impulsive noise recording Cumulative distribution val med=67.7 µs val moy=221.5 µs dev std=281.6 µs Vmd(mVolts) S i Distribution cumulative val max=999.2 µs Largeur des impulsions en µsec i t t(µs) pulse duration ( µs ) 70% of Impulsive Noises have a duration < 250µs 8

9 Impact of Impulsive Noise on Real Time services General degradation of QoS Fall of data transfer rate (slow refreshment of screen pages) => may be acceptable for data transmission services (internet) Pixelling Frozen screen Loss of synchronisation, black screen => not acceptable for real time services (Tv, Video streaming ) pixelling Frozen screen 9

10 Existing solutions to minimize the impact of impulsive noise Implement INP technique ( Impulsive Noise Protection ) INP order => protection efficiency INP order = bandwidth consuming ( data rate) Increase the noise margin => restriction in eligibility XdB Noise Margin => XdB in eligibility 10

11 On-going work and actions to solve the remaining issues Today's imperfect situation : INP = 2 is a minimum requirement 70% of impulse noises are corrected by an INP = 2 ( impulse duration < 250 µs ) New ways must be found to solve the remaining 30% of Impulse noise not corrected by INP 2 Action within EMC standardisation committees : update existing immunity standards CISPR 24 improve test set-up configurations to reflect actual conditions of use Develop a specific annex for xdsl applications testing in the new "Multimedia standard" CISPR 35 Noise bursts testing method simulating actual impulsive noise impact 11

12 II PLT Performance Versus EMC Standard compliance 12

13 PLT : Interest & Issues Interest to support the development of PLT technology Extension of DSL offer for "in-home" applications Use of existing infrastructure High data rate capability (IPTV / TVHD) Reasonable cost Performance & Regulatory issues EMC conformity assessment (CE marking) Bit-rate limitation New Fields of investigation Future generation of products to be controlled PLT channel characterisation Extension of frequency band & reduction of PSD Expected performance (max. bit-rate) Impact of impulsive noise 13

14 Why France Télécom is interested with PLT Provide an extension of the DSL offer "in-home" Allow easy accessible multiple connection point possibilities Do not require any additional cabling work High data rate capabilities (VoD / IPTV / TVHD) New techniques are ready and enough mature to provide efficient radio spectrum protection while expecting significant increase of data rate capabilities ( 1Gb/s? ) 14

15 Performance & Regulatory issues Millions of products are already in the field (next products generation must be controlled) A minimum bit-rate performance is required from PLT systems to be economically viable and able to support multiple real time applications and services Coexistence shall be maintained with other services (VDSL) Products must be compliant with EMC relevant standards (CISPR 22 / EN 55022) Primary objective is to protect the radio services 15

16 Comparison of results using different measurement networks Which network is suitable to assess PLT modems? => Comparisons of disturbance levels measured using either an AMN or a T-ISN (LCL 30 db) show an average difference of 18 db ISN RSIL Limite 50MB 5MB 1MB 0MB ISN RSIL Limite 50MB 5MB 1MB 0MB Quasi-peak limit Average limit NormeQP NormeMoy debit max 50 debit10% de max debit 1Mb pas de débit Qp Moy QP Moy QP Moy QP Moy ISN RSIL

17 Choice of measurement network problematic Method using an AMN : not suitable not adapted and designed to measure the launched CMC does not take into account the good symmetry properties of electronic engineering design imposes a reduction of PSD not compatible with a viable development of PLT technology Method using a T-ISN : suitable But!... Does not provide adequate protection of radio services over the SW Fq. bands unless mitigation techniques are implemented ( notches, power management ) OK with the requirement of mitigation techniques but : what final impact on bit-rate and usable capacity Fq. Bandwidth? 17

18 New fields of investigation & development Present situation : (2-30 MHz) : Ask for a relaxation of CISPR 22 limits ( 18dB) Implement notches (Fixed and dynamic) and power management techniques to protect radio services Improve immunity (hardware/software) to minimize impact of impulsive noise Challenge : How to increase the bit-rate performance (>200 Mb/s) & be EMC friendly?? Extend the frequency band 18

19 III EM disturbances in Home Network 19

20 Dealing with domestic disturbances Identification of domestic disturbance sources Appliance failure (insufficient lasting quality of PSU) Disturbance coupling path : radiated & conducted Impact on services 1 st order : decrease of QoS (quality of service) 2 nd order : breaking-down of DSL services Multiple ADSL subscribers impacted (same binder) High economic cost Actions On customer side On manufacturer side On Standardization side & Regulation side 20

21 Conducted and radiated coupling paths AC mains network Domestic apparatus AC mains network P S U Module Conducted coupling Ethernet DC Modem Radiated coupling DSLAM Telecom lines To other users 21

22 Example of defective PSU impact on multiple ADSL users AC mains network P S U Module 1 P S U Module 2 9V DC output of damaged PSU DC ADSL Modem WiFi DC TV Decoder Ethernet Telecom lines DSL access break-down for > 20 users!! DSLAM 22

23 Example of high noise level resulting from damaged components in a PSU PSU with damaged filtering capacitor < = > PSU with no filtering capacitor! dbµv PSU : OK Freq(Hz) PSU (built in or external) are responsible > 50% of identified disturbances 23

24 Consequences High level "REIN" (Repetitive Electrical Impulsive Noise) generated by the faulty PSU on the DC and/or AC power port increased QLN (Quiet Line Noise = stationary noise) on the DC port Damaged PSU generate impulsive noise inside the modem impulsive noise injected by coupling from mains cables to the telecom lines EMC standard should take this problematic into consideration 24

25 Impact on services QLN can seriously affect the synchronisation process of the modem (worst case : synchro. loss) Impulsive noise may more or less seriously affect the ADSL downstream bit-rate depending on : PSU type ADSL profile Loop length In case telecom cables and electric cables run in parallel : impulsive noise will affect all the ADSL subscribers connected via the same binder High economic cost 25

26 Actions On customer side : Expertise and maintenance action In situ measurements campaigns (data base constitution) Noise characteristics statistical studies (modelling) On manufacturer side : Quality product selection Endurance lifetime tests in laboratory Testing procedures elaboration On Standardization & Regulation side : Contribution in ITU 26

27 Contribution in ITU Context and issues Serious increase of interference cases from AC powered equipment and AC-DC converters High quality DSL connection required due to intensified deployment of "real time applications" (IPTV) Problem is easy to solve when the victim and interferer devices are located in the same customer's household Shutdown of defective device not belonging to the victim customer remains an open issue! Technical solutions (Mitigation technique) Cable selection, shielding, higher cable balance DSL planning and configuration Non-Technical solution Call for radio regulation authority to shutdown interfering equipment in case EMC limits are exceeded 27

28 Coexistence between PLT and VDSL Context Both technologies use the same frequency bands (up to 30MHz) In case the two services operate in the same subscriber s home = > Interference may occur EM coupling mode Conducted via power supplies (plugged on the same AC mains branch) Radiated via the cabling (nearby running copper pair cables) Signal on a phone line with and without neighbouring PLC Signal on an electrical line with and without neighbouring VDSL Impact studies : On transmission: loss of synchronization, performance reduction On services: breakdown, pixelling 28

29 Well informed people know it is impossible to transmit the voice over wires and that were it possible to do so, the thing would be of no practical value. Editorial in the Boston Post (1865)

30 Thank you for your attention Ph. LANCELIN 30 France Telecom R&D Orange Labs