ADTRAN SHDSL NxNTU Installation And Maintenance Manual

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ADTRAN SHDSL NxNTU Installation And Maintenance Manual Manual pdf 13 page image

61225101L1-5B 13Bit Error Rate TestThe SHDSL NTU contains a built-in Bit Error RateTest (BERT). The BERT involves injecting anddetecting a Pseudorandom Binary Sequence (PRBS)toward the network on the selected payload (i.e.G.703, Nx64, or entire SHDSL payload). The PRBSused in the SHDSL NTU is PRS15 as defined inITU-T O.150 and O.151. It is also known as a 2e-15pattern.The BERT is only accessible via the VT100 terminalscreens. Select “4. Test” from the Main MenuScreen. From the Test Screen, the SHDSL BERT,G.703 BERT, and Nx64k BERT options will appear,and each has one of the following status messages:N/A – This BERT is currently unavailable. Only oneBERT can be active at a time. For example, ifSHDSL BERT is active, all others will be N/A.ACTIVE – This BERT is currently in progress. Thesource column identifies the person who initiated theBERT.INACTIVE – This BERT is not currently in progress.After selecting a BERT type from the Test Screen, theBERT Screen will appear, illustrating both BERTstatistics and commands.If no BERT is currently active, the following list ofcommands will be available:Start – Starts the BERT on the selected port/service.If the BERT is currently active, the following list ofcommands will be available:Stop – Stops the BERT in progress.Inject a Single Bit Error – Injects one bit error intothe pattern.Restart – Clears out all statistics and restarts theBERT.In addition to the commands, the following statisticalinformation is provided:Bit Error Rate – Total number of bit errors dividedby the total number of bits in the current test interval.Bit Error Count – Total number of bit errors in thecurrent test interval.Pattern Sync Loss Count – Total number of timesthat the BERT has lost pattern sync.Errored Seconds – Total number of seconds in whichat least one bit error has occurred.Total Elapsed Time – Total time that has elapsedsince the test began (Days: Hours: Minutes: Seconds).A BERT status field supplies the followinginformation:On – The BERT has started and has pattern sync.Searching for pattern – The BERT has lost patternsync.Off – This BERT is currently off.LoopbacksThere are five types of local loopbacks and five typesof remote loopbacks available for each of the threeline interfaces (V.35, G.703, and SHDSL). Wheninitiating a loopback, the first step is choosing a lineinterface. When V.35 is chosen, the loopback willoccur at the V.35 drivers and receivers. When G.703is chosen, the loopback will occur at the G.703 driversand receivers. When SHDSL is chosen, the loopbackwill occur at the SHDSL drivers and receivers.NOTEAll remote loopbacks are initiated at the localExpress 6530 unit.Local Dual Sided Loopback – Provides abidirectional loopback at the NTU (Figure 12).Remote Dual Sided Loopback – Initiated at the NTUand provides bidirectional loopback at the LTU(Figure 13).Figure 13. Remote Dual Sided LoopbackNTU LTUFigure 12. Local Dual Sided LoopbackNTU LTU