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Alien Crosstalk for the Inexperienced User

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					                         Alien Crosstalk for the
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                          Inexperienced User




                                                   1
                                              Agenda
                         �What is alien crosstalk
                         �Where does alien crosstalk occur in the link
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                         �Standards & guidelines defining alien crosstalk
                         �Creating a quality plan to address requirements
                         �Link performance requirements
                         �Link certification




                                                                            2
                         What is Alien Crosstalk
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                                                   3
                                        What is Alien Crosstalk
                         � Alien crosstalk (AXT) is a unwanted disturbing signal coupling
                           from one balanced twisted-pair component, channel or
                           permanent link to another
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                         � The term “Alien” is used because unlike pair to pair crosstalk,
                           alien crosstalk is a disturbing noise source that originates from
                           outside the affected link’s cable and components




                                                                                               4
                                      History - Alien Crosstalk
                         � In 2006 the IEEE ratified 10GBASE-T and later published
                           IEEE 802.3-2008 defining a version of Ethernet with a nominal
                           data rate of 10 Gbit/s, ten times faster than Gigabit Ethernet
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                         � Achieving 10GBASE-T over copper required new encoding
                           schemes, 500MHz bandwidth and full duplex transmission
                         � Due to these changes alien crosstalk, which has always been
                           present in twisted pair copper networks and cannot currently be
                           cancelled, became a significant noise source capable of
                           disrupting 10GBASE-T
                         � In response the industry defined new standards and guidelines
                           for acceptable levels of alien crosstalk and developed test
                           methods for measuring alien crosstalk


                                                                                             5
                              Reflected Mode of Alien Crosstalk
                         � Near end alien crosstalk is a reflected mode that is
                           sourced and received at the same ends of the
                           disturbing and disturbed links
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                                                                                  6
                          Transmitted Mode of Alien Crosstalk
                         � Far end alien crosstalk is a transmitted mode that
                           is sourced and received at opposite ends of the
                           disturbing and disturbed links
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                                                                                7
                         Where Does Alien Crosstalk
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                             Occur in the Link




                                                      8
                              Where Does Alien Crosstalk Occur
                         � Alien crosstalk occurs between the cables and components
                           of a disturber link and a disturbed (victim) link
                         � Alien crosstalk coupling increases as the components and
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                           cables of the two links approach each other
                         � Alien crosstalk is extremely dependent upon installation
                           practices such as patch cord positioning, cable bundling,
                           use of tie-wraps, pathway fills and component placement
                         � Alien crosstalk is not simply limited to a single disturbing
                           link, multiple disturbing links may add to the total alien
                           crosstalk present on a disturbed link



                                                                                          9
                            Alien Crosstalk in the Horizontal Link
                         � Alien crosstalk occurs when
                           different cables run in parallel for
                           an extended distance in close
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                           proximity
                         � Long, tightly bound cable bundles
                           present an ideal location for
                           significant levels of alien crosstalk
                         � A worst case condition exists
                           when a disturbed (victim) cable is
                           surround by six disturbing cables



                                                                     10
                                      Alien Crosstalk in Cords
                         � Alien crosstalk occurs when
                           different equipment and patch
                           cords are routed together in
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                           close proximity
                         � Bound cords present an ideal
                           location for significant levels
                           of alien crosstalk in the first
                           few metres of the link
                         � Management bar lay and
                           waterfalls also present
                           opportunity for alien crosstalk


                                                                 11
                                 Alien Crosstalk in Components
                         � Alien crosstalk occurs where
                           components of different links
                           come into close proximity
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                         � Patch panels present an ideal
                           location for significant levels
                           of alien crosstalk
                         � A worst case condition exists
                           when a disturbed port is
                           surrounded on three or four
                           sides by disturber ports



                                                                 12
                         Standards & Guidelines
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                         Defining Alien Crosstalk




                                                    13
                              Standards Defining Alien Crosstalk
                         � ISO/IEC 11801 Ed 2.0 Amendment 1 provides channel
                           and alien crosstalk requirements for Class EA, Class F and
                           Class FA
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                         � BS EN 50173-1 A1 provides channel and alien crosstalk
                           requirements for Class EA, Class F and Class FA
                         � ANSI/TIA-568-C.2 provides channel, permanent link and
                           alien crosstalk requirements for Category 6A




                                                                                        14
                             Guidelines Defining Alien Crosstalk
                         � Guidelines provide methods for re-characterizing installed
                           Class E and Category 6 cabling to ensure 10GBASE-T
                           operation
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                         � ISO/IEC TR 24750 and CLC/TR 50173-99-1:2007 both
                           provide channel and alien crosstalk recommendations for
                           installed Class E
                         � TIA TSB-155 provides channel, permanent link and alien
                           crosstalk recommendations for installed Category 6
                         � Class E and Category 6 cabling is not recommended for
                           new installations supporting 10GBASE-T operation



                                                                                        15
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                         Creating a Quality
                                Plan



                                              16
                                       Cable Considerations
                         � UTP Class EA and Category 6A cables with improved alien
                           crosstalk performance may be constructed with an inner
                           seperator, a larger outside wall thikness and an increased
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                           cable diameter.
                         � Cable alien crosstalk performance can be compromised by
                           deforming the outer jacket or inner separator due to tie
                           wraps, excessive conduit/pathway fill or exceeding
                           recommended bend radius
                         � Pathway and conduit fill ratios increase for the same
                           number of cables if the cable diameter increases



                                                                                        17
                            Cord and Component Considerations
                         � UTP Class EA and Category 6A equipment and patch
                           cords typically have a larger outside wall thickness to
                           reduce alien crosstalk
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                         � Cord alien crosstalk performance can be compromised by
                           deforming the outer jacket due to tie wraps and exceeding
                           recommended bend radius
                         � Compacting cords in management bars and trays brings
                           cords into closer proximity increasing alien crosstalk in the
                           critical first few meters of the link
                         � UTP Class EA and Category 6A patch panels are typically
                           lower density than Class E and Category 6


                                                                                           18
                                     Reducing Alien Crosstalk
                         � Minimize the number of cables in a bundle, reducing the
                           number of possible disturbers
                         � Un-bundle the horizontal link in the first 15 metres
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                           allowing the cables to separate
                         � Eliminate cable ties if possible, if not reduce cable tie
                           tension and space cable ties farther apart
                         � Randomly lay cable in trays to prevent any two cables from
                           running in close proximity their entire length
                         � Use F/UTP or S/FTP cables and cords to significantly
                           reduces alien crosstalk



                                                                                        19
                                Reducing Alien Crosstalk (cont)
                         � Separate equipment and patch cords and eliminate cable
                           ties to reduces the alien crosstalk coupling in the first few
                           metres of the link
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                         � Lay cords randomly in management bars to prevent any
                           two cords from running in close proximity their entire
                           length
                         � Reduce the number of cords in a waterfall and maximize
                           the radius to reduce cord compaction
                         � Use fully shielded components to significantly reduce alien
                           crosstalk



                                                                                           20
                                  Alien Crosstalk Consideration
                         � Alien crosstalk is extremely dependent upon installation
                           practices such as patch cord positioning, cable bundling,
                           use of tie-wraps, pathway fills and component placement
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                         � Alien crosstalk certification is unique, its a selective process
                           using statistical data about the installation to identify and
                           certify the links deemed most prone to alien crosstalk
                           interference
                         � Certifying alien crosstalk on each Class EA/F/FA and
                           Category 6A link or re-certifying alien crosstalk on each
                           Class E or Category 6 link may not be necessary nor
                           plausible due to test times


                                                                                              21
                             Alien Crosstalk Consideration (cont)
                         � Alien crosstalk testing consumes significantly more time
                           than channel or link testing
                         � Worst case instrument test time for a single disturbed link
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                           testing PSANEXT and PSAACRF at both ends of the link

                               # of Disturbing Links   Worst Case Instrument Test Time
                                         1                       1.5 minutes
                                        2                         3 minutes
                                        4                         6 minutes
                                        8                        12 minutes



                                                                                         22
                                        Additional Guidance
                         � Seek guidance from cable and component manufacturers
                           for installing and certifying Class EA/F/FA or Category 6A
                           links
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                         � Seek additional guidance from cable and component
                           manufacturers for identifying and selecting disturbed and
                           disturbing links for alien crosstalk certification
                         � Consult ISO/IEC TR 24750, CLC/TR 50173-99-1:2007
                           or TIA TSB-155 for determining the Class E or Category 6
                           alien crosstalk environment and alien crosstalk mitigation
                           techniques



                                                                                        23
                                         Create a Quality Plan
                         � Create a quality plan that considers how the selection and
                           installation of cable and components affects the alien
                           crosstalk environment
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                         � The quality plan should identify changes to the installation
                           brought on by Class EA/F/FA or Category 6A components
                         � The quality plan should address alien crosstalk certification,
                           including identification & selection of test links and criteria
                           for obtaining satisfactory performance
                         � A Class E and Category 6 quality plan should address alien
                           crosstalk mitigation practices
                         � Obtain agreement from all parties


                                                                                             24
                                 Create a Quality Plan (cont)

                         �A good quality plan that
                          considers and incorporates the
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                          elements in the previous slides
                          will reduce installation and
                          certification time while
                          increasing confidence in
                          installation’s ability to meet
                          alien crosstalk requirements



                                                                25
                         Link Performance Requirements
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                                                         26
                         Performance 10GBASE-T Class E & Category 6

                         � Pair measurements              � Alien crosstalk added
                             � Wiremap                      1-500MHz
                             � Delay/Delay Skew/Length*       � PSANEXT
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                             � Resistance**                   � Average PSANEXT
                                                              � PSAACRF
                         � Pair to pair performance
                                                              � Average PSAACRF
                           extended to 500MHz
                                                              � Marginal Computation
                             � Insertion Loss
                             � Return Loss
                             � NEXT & PSNEXT
                             � ACR-N & PSACR-N**
                                                              * Not a recognized Class E measurement
                             � ACR-F & PSACR-F                ** Not a recognized Category 6 measurement



                                                                                                           27
                            Performance Class EA & Category 6A
                         � Pair measurements              � Alien crosstalk 1-500MHz
                             � Wiremap                        � PSANEXT
                             � Delay/Delay Skew/Length*       � Average PSANEXT
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                             � Resistance**                   � PSAACRF
                                                              � Average PSAACRF
                         � Pair to pair performance
                           1-500MHz
                             � Insertion Loss
                             � Return Loss
                             � NEXT & PSNEXT
                             � ACR-N & PSACR-N**
                                                              * Not a recognized Class EA measurement
                             � ACR-F & PSACR-F                ** Not a recognized Category 6A measurement



                                                                                                            28
                                        Performance Class F
                         � Pair measurements          � Alien crosstalk added
                             � Wiremap                  1-600MHz
                             � Delay/Delay Skew           � PSANEXT
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                             � Resistance                 � Average PSANEXT
                                                          � PSAACRF
                         � Pair to pair performance
                                                          � Average PSAACRF
                           1-600MHz
                             � Insertion Loss
                             � Return Loss
                             � NEXT & PSNEXT
                             � ACR-N & PSACR-N
                             � ACR-F & PSACR-F


                                                                                29
                                       Performance Class FA
                         � Pair measurements          � Alien crosstalk 1-1000MHz
                             � Wiremap                    � PSANEXT
                             � Delay/Delay Skew           � Average PSANEXT
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                             � Resistance                 � PSAACRF
                                                          � Average PSAACRF
                         � Pair to pair performance
                           1-1000MHz
                             � Insertion Loss
                             � Return Loss
                             � NEXT & PSNEXT
                             � ACR-N & PSACR-N
                             � ACR-F & PSACR-F


                                                                                    30
                            Power Sum Alien NEXT (PSANEXT)
                         � PSANEXT sums four near end alien crosstalk measurements from
                           each pair of the disturbing link to a single pair of the disturbed link
                         � Four PSANEXT results are calculated at the end of a disturbed link for
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                           a total of 8 results if both ends are tested




                                                                                                     31
                             Power Sum Alien ACRF (PSAACRF)
                         � PSAACRF sums four far end alien crosstalk measurements from each
                           pair of the disturbing link to a single pair of the disturbed link
                         � Four PSACRF results are calculated at the end of a disturbed link for a
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                           total of 8 results if both ends are tested




                                                                                                     32
                                Average PSANEXT & PSAACRF
                         � Average PSANEXT is the average of the PSANEXT
                           results on each of the disturbed link pairs
                         � Average PSAACRF is the average of the PSAACRF results
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                           on each of the disturbed link pairs
                         � One Average PSANEXT or PSAACRF result is calculated
                           at the end of a disturbed link for a total of 2 results if both
                           ends are tested




                                                                                             33
                            Alien Crosstalk Margin Computation
                         � The alien crosstalk margin computation is used if the
                           PSANEXT or the PSAACRF limits are not met on Class
                           E or Category 6 links
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                         � The alien crosstalk margin computation ensures that the
                           total combined PSAFEXT and PSANEXT that couples
                           into a channel is limited in order to maintain the
                           10GBASE-T minimum signal to noise ratio
                         � The alien crosstalk margin calculation is a sufficient
                           qualification for suitability of Class E or Category 6
                           channels to support 10GBASE-T operation



                                                                                     34
                             35
Link Certification
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                           Certifying Class EA/F/FA & Category 6A
                         � Certify the channel or link performance of every link saving
                           the Autotest result and graphical data
                         � Using the test plan criteria and result data, identify the
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                           disturbed links deemed most prone to alien crosstalk
                           interference and their associated disturbing links
                         � Per the test plan criteria, select from the identified links
                           those disturbed and disturbing links that require alien
                           crosstalk certification
                         � Certify the alien crosstalk of the selected disturbed links per
                           the test plan



                                                                                             36
                                Re-certifying Class E & Category 6
                         � Re-certify the channel or link performance of every link
                           designated to support 10BASE-T saving the Autotest
                           result and graphical data
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                         � Using the test plan criteria and result data, identify the
                           disturbed links deemed most prone to alien crosstalk
                           interference and their associated disturbing links
                         � Re-test the channel or link performance of all identified
                           disturbing links saving the Autotest result and graphical
                           data*
                         � Certify the alien crosstalk of the selected disturbed links
                           per the test plan
                          *Links designated only as a disturber do not have to pass channel or link certification



                                                                                                                    37
                         Typical PSANEXT Test Setup
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                                                      38
                         Typical PSAACRF Test Setup
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                                                      39
                                       Alien Crosstalk Testing
                         � Testing is conducted from
                           the PC result manager alien
                           crosstalk (AXT) application
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                         � The AXT application
                           provides the tools needed to
                           certify alien crosstalk
                         � The AXT application
                           displays alien crosstalk
                           certification results and link
                           statistics in real time



                                                                 40
                                               Conclusion
                         � Alien crosstalk is a unwanted disturbing signal coupling
                           from one balanced twisted-pair component, channel or
                           permanent link to another
www.meggernetworks.com




                         � Alien crosstalk is extremely dependent upon installation
                           practices and occurs where links come into close proximity
                           such as in cable bundles and patch panels
                         � ISO/IEC 11801 Ed 2.0 Amendment 1 and BS EN 50173-
                           1 A1 provide channel and alien crosstalk performance
                           requirements for Class EA/F/FA links
                         � ANSI/TIA-568-C.2 provides channel or link and alien
                           crosstalk performance requirements for Category 6A links


                                                                                        41
                                           Conclusion (cont)
                         � ISO/IEC TR 24750 & CLC/TR 50173-99-1:2007 provide
                           guidance for supporting 10GBASE-T on Class E channels
                         � TIA TSB-155 provides guidance for supporting
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                           10GBASE-T on Category 6 channels and links
                         � Create a quality plan addressing the unique requirements for
                           installation, certification and alien crosstalk mitigation prior
                           to starting
                         � A good quality plan will reduce installation and certification
                           time while increasing confidence in installation’s ability to
                           meet alien crosstalk requirements



                                                                                              42
                           43
Thank you
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