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Interpreting the Results

The lower frequency tones represent the bandwidth used for the upstream signal. The higher frequency tones at the right show

the frequencies used for the downstream signal.

The bits should drop to zero after the end of the upstream. This is the buffer between the upstream and downstream signals. The

actual size of this buffer varies.

If there is a major drop in bits in either the downstream or upstream section, this may indicate that there is a possible interferer at

that frequency. For example, if there is a major drop at 772 kHz, this may represent an interfering T1 signal.

Tone Allocations in ADSL/2+

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5.8.7 SNR per Tone

This feature measures the Signal to Noise Ratio (SNR) for each downstream tone used by the modem to transmit the provisioned rate.

This can be displayed as a graph or as a table.

During initial modem link up, a signal to noise measurement is made for each tone and the bit distribution is optimized to deliver the

desired bit rate. During showtime, modems constantly monitor the SNR/tone and the bit distribution is adjusted to optimize bandwidth

based on noise, interference and cross talk. If a tone degrades in quality, a bit swap command adjusts the bit allocation for that

particular tone and these bits are either re-allocated to another tone or removed completely.

As with all transmission lines, signal quality depends primarily on the attenuation and SNR. The frequency of the bin can therefore

determine how many bits can be encoded, i.e. SNR can differ from bin to bin. Generally speaking, 1 bit can be encoded reliably for each

3dB of available dynamic range above the noise floor e.g. a bin with a SNR of 21dB would be able to carry 7 bits. However, due to the

face that a 

minimum of 2 bits

 (QAM-4) are encoded per bin, the SNR of any single bin 

cannot drop below 6dB

.

 

Raw SNR per Tone

MTTplus-_Test_Module

Page 37 of 44

Содержание MTTplus-522 OSP+

Страница 1: ......

Страница 2: ... 3 Connector Panel 5 0 Setup 5 1 DMM Multimeter 5 1 1 DMM Capacitance 5 1 2 DMM Resistance 5 1 3 DMM Auto Test 5 1 4 Recommended DMM Measurements 5 1 5 Ground Resistance 5 2 TDR 5 2 1 Time Domain Reflectometer TDR 5 3 RFL Resistance Fault Locator 5 4 OSP Expert 5 4 1 Impulse Noise 5 4 2 Longitudinal Balance 5 4 3 LOSS 5 4 4 PDS Noise 5 5 POTS VF 5 5 1 NOISE 5 5 2 Ringers MTTplus 522_OSP _Test_Modu...

Страница 3: ...SL2 5 7 4 ADSL2 5 7 5 VDSL2 5 7 6 G fast 5 8 DSL G fast Measurements 5 8 1 Setup 5 8 2 Line Status 5 8 3 DSL Modem 5 8 4 Errors 5 8 5 Tones 5 8 6 Bits per Tone 5 8 7 SNR per Tone 5 8 8 HLOG 5 8 9 Quiet Line 5 8 10 Events 6 0 Common Functions 7 0 Warranty and Software 8 0 Product Specification 9 0 Certification and Declarations 10 0 About VeEX MTTplus 522_OSP _Test_Module Page 3 of 44 ...

Страница 4: ...tted electronically or otherwise without written permission from VeEX Inc This device uses software either developed by VeEX Inc or licensed by VeEX Inc from third parties The software is confidential and proprietary of VeEX Inc The software is protected by copyright and contains trade secrets of VeEX Inc or VeEX s licensors The purchaser of this device agrees that it has received a license solely...

Страница 5: ...d be stored at 20 C 68 F room temperature charged to about 30 to 50 of its capacity Spare battery packs should be charged and used at least once a year to prevent over discharge rotate them regularly It is recommended to charge and use battery packs at least every three months Battery packs must not go without recharging reconditioning for more than six months After extended storage battery packs ...

Страница 6: ...rotection and grounding gear when Inserting extracting or handling test modules Connecting or disconnecting cables from modules or platform Go back to top Go back to TOC MTTplus 522_OSP _Test_Module Page 7 of 44 ...

Страница 7: ...er SSID Analysis Fiber Optic Tools USB accessories support Digital Fiber Inspection Scope and Optical Power Meter 3 1 Evolution of Residential DSL to G fast As DSL technology continues to improve the copper wire length from a broadband provider s distribution point to the customer premises has decreased providing even greater speeds to customers ADSL relied solely on existing copper telephone wire...

Страница 8: ...Resistance Meter with Ring Tip and Ground results Verify insulation resistance Detect the presence of shorts DC Volt Meter with Ring Tip and Ground results Verify proper POTS line power Detect foreign DC voltage AC Volt Meter with Ring Tip and Ground results Detect Foreign AC induced voltage T G R G T R from adjacent power lines DC Current Meter with Ring to Tip results Verify POTS DC Loop current...

Страница 9: ...talk immunity VF Noise Measurement Metallic Noise measures the background noise on a cable pair Power Influence measures the noise from sources such as power Balance is derived from Metallic Noise minus Power Influence MTTplus 522_OSP _Test_Module Page 10 of 44 ...

Страница 10: ...Go back to TOC 4 2 Battery The MTTplus chassis is equipped with an intelligent Li ion rechargeable battery pack which is located in the rear of the unit The battery will be partially charged upon delivery so it is recommended to charge the battery fully before use Please charge the battery at room temperature to preserve its life and to obtain maximum charge The battery is charged during operation...

Страница 11: ...e desired leg e g Tip Ring or All which will measure all three legs Go back to top Go back to TOC 5 1 1 DMM Capacitance Capacitance Loop Length Estimate Based on Capacitance Tip Ring value requires an Open circuit at the far end of the line Capacitance Balance Ratio of Capacitance Tip Ground Capacitance Ring Ground displayed as a percentage from 1 0 to 100 0 Pass Threshold is typically 95 MTTplus ...

Страница 12: ...p Resistance Length Estimate based on Resistance Tip Ring value with a hard short at the far end of the line Use Ω mode for measuring a circuit less than 10 kohms Use MΩ mode for measuring Insulation Resistance or Leakage Go back to top Go back to TOC MTTplus 522_OSP _Test_Module Page 13 of 44 ...

Страница 13: ...M Measurements 5 1 5 Ground Resistance A special mode that measures the resistance between the ground at the CO Exchange and the ground at the test set location Go back to top Go back to TOC 5 2 TDR Fault identification and location Impedance mismatch detection MTTplus 522_OSP _Test_Module Page 14 of 44 ...

Страница 14: ...Open At Far End Short Bridge Tap Go back to top Go back to TOC MTTplus 522_OSP _Test_Module Page 15 of 44 ...

Страница 15: ... distance range When using Two Pair Mode you can select between Split Mode or Over Mode Split Mode presents two separate TDR traces with Trace One at the top half of the screen and Trace Two at the bottom half of the screen Overlay Mode superimposes the two traces into a single presentation which can be used for troubleshooting a problem pair against a known good pair 5 3 RFL The Resistance Fault ...

Страница 16: ...ep a running count of the number of impulse events over time Impulse noise is defined as a random pulse whose amplitude is much higher than that of background noise Impulse noise is transient short duration noise which can cause transmission errors Difficult to detect with a Spectrum Analyzer Presented as Impulse Noise Event Counter and Graph MTTplus 522_OSP _Test_Module Page 17 of 44 ...

Страница 17: ...ive and Resistive is significant a normal mode crosstalk signal arises Longitudinal Balance is another measurement technique used to quantify the degree of cable unbalance Transmit a common mode test signal along the shield of the cable and measure the resultant differential signal across Tip A and Ring B reported in units of dB Voiceband Longitudinal Balance typical Pass Limit is 60 dB Wideband L...

Страница 18: ...OC 5 4 4 PSD To access PSD go to OSP Expert PSD 8MHz and PSD 35 MHz PSD Field Spectrum Analyzer Wideband Background Noise Measurement Measure induced crosstalk from in service neighboring cable pairs or external noise MTTplus 522_OSP _Test_Module Page 19 of 44 ...

Страница 19: ... end of the cable pair It is measured in dBrn decibels relative to noise dBrn dBm 90 First press Noise V then Measure 2 Power Influence is noise to ground measurement that measures noise from sources such as induced AC voltage from power utility lines It is displayed in the Power Influence box First press Power Infl then Measure 3 Balance Displays CALC BALANCE This is the difference between Power ...

Страница 20: ...ngitudinal Balance Cable Balance is critical for crosstalk immunity Interference is a common mode longitudinal signal When the degree of unbalance with respect to earth ground Capacitive and Resistive is significant a normal mode crosstalk signal arises Longitudinal Balance is another measurement technique used to quantify the degree of cable unbalance Transmit a common mode test signal along the ...

Страница 21: ...Go back to top Go back to TOC MTTplus 522_OSP _Test_Module Page 22 of 44 ...

Страница 22: ...ice accessory for the MTTplus 522 module Provides shorting function for RFL Signal transmission for Insertion Loss Battery operated V FED requires a special RJ45 to multiple alligator clips test cable P N F02 00 100G MTTplus 522_OSP _Test_Module Page 23 of 44 ...

Страница 23: ...low Color banded clips are currently not being used Go back to top Go back to TOC 5 6 1 Insertion Loss with V FED To access LOSS go to OSP Expert LOSS Insertion Loss is a dual ended frequency response measurement done in conjunction with the V FED accessory connected at the far end of the pair under test Currently the frequencies tested are 5 2 MHz 8 5 MHz 12 MHz 17 664 MHz and 35 328 MHz which re...

Страница 24: ... FED FED Connections for RFL Strap Function Red Banded Test Clips Ground Clip Communication with MTTplus 522 Blue Banded Test Clips Go back to top Go back to TOC 5 6 3 Basic Test Procedure Make FED connections to the copper pair s under test Make MTTplus 522 connection to the copper pair s under test Launch RFL Press FED ON to turn on the far end V FED Then immediately Press FED STRAP to initiate ...

Страница 25: ...dth is extended from 4 kHz to 2 2 MHz in the case of ADSL2 and up to 30 MHz for VDSL2 Extended bandwidths make the copper pair far more susceptible to faults impairments and other degradation Modem Emulation testing at this layer not only provides information about the copper s performance but connection to the DSLAM or customer s modem can also be assessed MTTplus 522_OSP _Test_Module Page 26 of ...

Страница 26: ... referred to as ITU G 992 1 the standard expands the usable bandwidth of existing copper telephone lines to rates up to 12 Mbit s downstream and 1 3 Mbit s upstream Discrete Multi Tone DMT mode divides the ADSL signal into 255 carriers bins spaced in multiples of 4 3125kHz The DMT spectrum has 224 downstream frequency bins and up to 31 upstream bins In Annex A systems where Voice POTS is used on t...

Страница 27: ...the same parameter and when implemented an INP value between 2 and 16 can correct errors from noise impulses ranging from 250µs to 3 75ms in length INP is a key feature in most IPTV video deployments and enables better Video QOS by minimizing the effects of Impulse Noise The INP value for the interleaved channel can be set by the user and is expressed in symbols For example an INP value of 1 means...

Страница 28: ...standard which has numerous configuration profiles and bandplans to meet regional service provider requirements The frequency bandwidth has increased from 12 MHz to 30 MHz with options for 8 5 MHz 12 MHz 17 7 MHz and 30 MHz spectrums The standard also defines asymmetric Plan 998 and symmetric Plan 997 bandplans for the transmission of upstream and downstream signals Profiles To simplify configurin...

Страница 29: ... the DSL line Messages are sent using the pilot tones to ensure that both ends are ready for transceiver training process 2 Training DSLAM measures and adjusts the power output to equalize the circuit Unless configured otherwise it negotiates the fastest possible speed based on local loop conditions 3 Channel Analysis DSLAM tells the modem which options are configured and sends a predefined medley...

Страница 30: ...rate SNR Margin dB Signal to Noise Ratio margin Attenuation dB Difference in the power level transmitted at the near end and received at the far end Delay ms Interleave delay INP sym See the note on Impulse Noise Protection Depth fm Interleave depth Tx Power Transmitting power output is typically the level needed to achieve the noise margin configured in the DSLAM Mode Indicates the current test m...

Страница 31: ...inst an impulse noise environment Aggregate Rate The sum of Downstream and Upstream rates SNR Margin dB Maximum dB increase in equalized noise or maximum dB decrease in equalized signal that a system can tolerate and maintain a BER of 1E 7 Start ST and duration time ET DSL synchronization status ADSLx VDSLx mode and profile and estimated length are displayed in a separate table MTTplus 522_OSP _Te...

Страница 32: ...d in unavailable time Once unavailable the xDSL line becomes available at the onset of 10 contiguous seconds with no SES However these 10 seconds with no SES are excluded from unavailable time Retrain Press to resynchronize the modem Tap Reset to reset error counters On line Reconfiguration OLR During initial modem link up a signal to noise measurement is made for each tone and the bit distributio...

Страница 33: ... 5 Tones Carrier tone measurements of tables and graphs aid the detection of copper faults that degrade DSL service quality Graphs and tables of carrier tone measurements are displayed in the Tones tab Select a tone measurement from the side panel to view Viewing Exact Measurements on a Graph To find the exact measurement on a graph such as bit count and frequency of a specific tone tap on the gra...

Страница 34: ...s talk issues It provides valuable insight to ADSL spectrums or VDSL2 channel plan implemented Frequency Division Duplexing FDD in ADSL VDSL is used to divide upstream and downstream bandwidth Discrete Multitone DMT Overview In traditional VDSL2 ADSLx Discrete Multitone DMT divides the signal into multiple carriers bins centered in multiples of 4 3125 kHz The spectrum of each bin overlaps with its...

Страница 35: ...lexing OFDM Number of subcarriers in a FFT 4000 2000 in 106 MHz profile Duplexing method FDD Frequency Division Duplex TDD Time Division Duplex OFDM symbol time Approximately 250 µs in 17 MHz profile Approximately 20 µs Vectoring method Using ITU T G 993 5 Supported along with adaptations required for high frequency Transmit power It depends on profile 14 5 dBm 4 dBm FEC type RS Coding Reed Solomo...

Страница 36: ...ble During initial modem link up a signal to noise measurement is made for each tone and the bit distribution is optimized to deliver the desired bit rate During showtime modems constantly monitor the SNR tone and the bit distribution is adjusted to optimize bandwidth based on noise interference and cross talk If a tone degrades in quality a bit swap command adjusts the bit allocation for that par...

Страница 37: ...h The frequency response curve can depict the presence of Bridge Taps which can have a characteristic magnitude dip A clean Hlog curve s slope will decline gradually and evenly Clean Line HLOG Graph with No Bridge Taps Dips on Curve May Indicate Bridge Taps MTTplus 522_OSP _Test_Module Page 38 of 44 ...

Страница 38: ...lp detect the presence of RF interference on the copper pair under test QLN Go back to top Go back to TOC 5 8 10 Events The Events tab displays a date and time log of events such as synchronization status and errors that occur during testing Events Go back to top Go back to TOC MTTplus 522_OSP _Test_Module Page 39 of 44 ...

Страница 39: ...TTplus platform common fuctions please refer to the MTTplus Platform Manual here The following functions are common to all VeEX test sets Tool Utilities Files Tools tab Tools tab Go back to top Go back to TOC MTTplus 522_OSP _Test_Module Page 40 of 44 ...

Страница 40: ...c by the customer along with proof of purchase within thirty 30 days of the request by the customer freight prepaid Additionally during the warranty period VeEX Inc will provide without charge to the customer all fixes patches and enhancements to the purchased software firmware and software options VeEX Inc does not warrant that all software or firmware defects will be corrected New enhancements a...

Страница 41: ...8 0 Product Specifications The most recent product specifications can be downloaded here from the VeEX website Go back to top Go back to TOC MTTplus 522_OSP _Test_Module Page 42 of 44 ...

Страница 42: ...uropean Free Trade Association EFTA EN61010 1 Click here for CE Declaration of Conformity relating to VeEX products What is RoHS RoHS is the acronym for Restriction of Hazardous Substances Also known as Directive 2002 95 EC it originated in the European Union and restricts the use of specific hazardous materials found in electrical and electronic products All applicable products imported into the ...

Страница 43: ...ice turn up and integrate service verification features across DSL Fiber Optics CATV DOCSIS Mobile backhaul and fronthaul CPRI OBSAI next generation Transport Network Fibre Channel Carrier Metro Ethernet technologies WLAN and Synchronization Visit us online at www veexinc com for latest updates and additional documentation VeEX Incorporated 2827 Lakeview Court Fremont CA 94538 USA Tel 1 510 651 05...

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