understanding quality of experience diagnostic tools – line test (or how to save money and...
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Understanding Quality of ExperienceDiagnostic Tools – Line Test (or how to save money and increase customer satisfaction)
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Agenda
• Who is Legerity?• Quality of Experience improvement tools
– Automated Call Quality Monitoring– In-Premise Loop Diagnostics
• Loop/line test background• Key line test specifications• Descriptions of CPE line tests• CPE line test software suite example• Summary
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Who is Legerity
• Legerity, now part of Zarlink Semiconductor, is the leading supplier of voice interface integrated circuits
– FXS (POTS interface) solutions for all points in the network from the central office to residential gateways, and everywhere in between
• MSAN, DLC, etc. and Enterprise gateways (PBX, etc.)
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
QoE Improvement Tools - Overview
• Automated Call Quality Monitoring– Many VoIP CPE devices (e.g. Cable EMTA’s) now automatically monitor calls and
log and store metrics• Listening quality and conversational quality (MOS) scores• Residual echo return loss scores• Packet loss analysis• Broadband signal quality • IP and call processing message logs
• In-Premise Loop Diagnostics– Many VoIP CPE devices now have the capability to performing remote tests on the
in-home wiring and provide troubleshooting data– The system operator can remotely perform these tests returning either
simple pass/fail results or more extensive test reports
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
In-Home Wiring Creates Challenges…..
INSIDE HOUSE WIRING is one of the top causes for Trouble Reports.INSIDE HOUSE WIRING is one of the top causes for Trouble Reports.
Due to the high rate of trouble tickets related to inside wiring,Due to the high rate of trouble tickets related to inside wiring,
VoIP service providers recognize the need for CPE line testing VoIP service providers recognize the need for CPE line testing
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Loop Diagnostics Background
• ‘Metallic Loop Testing’ or ‘Line Testing’ involves testing for faults in the ‘copper plant’ (telephone wires)
• Line testing was originally deployed in central offices using large expensive test heads that tested each wire pair one at a time
– The test head is connected to each telephone line via a switch or relay
• Today, line testing also needs to be deployed in remote equipment, DLCs, MSANs, PBXs and even residential gateways (CPE), etc.
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
VoIP CPE Line Testing
• Service providers recognize the need for VoIP line testing– US Cable MSOs (e.g Comcast, Cox) require GR-909 line testing in EMTAs
– US ILECs (e.g. Verizon) require GR-909 line testing in FTTH gateways
– Vonage deploys GR-909 line testing in residential gateways (ATA’s)
– DSL Forum TR-122 requires TIA-1063 line testing (p. 28)
• Benefits of deploying remote line testing capability in VoIP CPE– Automated, remote testing capability eliminates costly truck rolls
– Enhances call center support capabilities to identify simple faults
– Reduces maintenance costs
– Decreases mean time to repairs
– Increases customer satisfaction through quick problem resolution and therefore reduces customer churn
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
GR-909 Excerpt (Section 12.4 – Testing)
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
TIA-1063 Line Testing Excerpt
Test Descriptions
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Hazardous Voltage Test
• Tests for the presence of hazardous AC or DC voltage on the line– AC >50V or DC >135V– Force Zero Voltage (to discharge the line) and measure AC and DC Voltages
• Tip to Gnd, Ring to Gnd, Tip to Ring
– Indicates that a hazardous is present on the drop
• Possible Cause– Tip or Ring shorted to home AC power line (110V-240V)– Tip or Ring shorted to other equipment DC power supply
• Possible Symptoms– No Dial Tone– Can not dial out– No phones ring– Phone interface in Protection State– 60Hz/50Hz buzz on line– Phone may ring at 60Hz/50Hz
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Foreign Voltage Test
• Tests for the presence of foreign AC or DC voltage on the line– AC >10V or DC >6V– Force Zero Voltage (to discharge the line) and measure AC and DC Voltages
• Tip to Gnd, Ring to Gnd, Tip to Ring
– Indicates that a hazardous or foreign voltage is present on the drop
• Possible Cause– Connected to PSTN– Tip or Ring shorted to other
equipment DC power supply
• Possible Symptoms– No Dial Tone– Can not dial out– No phones ring– LC in Protection State
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Resistive Faults Test
• Tests DC resistance– Force DC current, measure voltage,
compute the Resistance (Ohms law) • Tip to Gnd, Ring to Gnd, Tip to Ring
– Resistance below threshold indicates a fault
• Possible Cause– Tip or Ring shorted to cable shield
– Moisture in cable
– Protection device shorted
– Staple or nail shorting Tip and Ring
• Possible Symptoms– No Dial Tone
– No incoming calls
– 50Hz/60Hz buzz on line due to longitudinal imbalance
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Receiver Off Hook Test
• The test discriminates between a resistive fault in the loop and a receiver-off-hook condition from properly working terminal equipment
– Indicates that a telephone receiver (or other CPE) is off-hook as opposed to a resistive fault – phone has non-linear signature, different than a resistor
• Possible Cause– One of multiple phones left off hook
• Possible Symptoms– No Dial Tone– Can not receive calls
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Ringer Equivalence Test
• This test measures the CPE equipment’s AC ringer impedance– 20Hz AC Test – tests to see if the FCC part 68 REN load is within range
• REN too high – excessive load, could cause pre-trip faults• REN too low – phone is probably not plugged in
• Possible Cause– Too many phones connected
• Exceeds 5 REN
– No phone connected• Or less than 0.175 REN
– Open in loop– Ringer is open– Faulty phone
• Ringer capacitor shorted
• Possible Symptoms– Phone does not ring– Line ring trips after a short burst of ring (pre-trip)– Not all phones ring– Low ring loudness
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
GR-909 Pass/Fail Criteria
Line Testing Software
Example
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Legerity’s VeriVoice™ Test Suite Software
• VeriVoice™ Test Suite is a subscriber line test software package for VoIP equipment
– Provides outward, GR-909, tests and/or inward self-tests
– GR-909 Tests include:• Line Voltage Test
– Hazardous and foreign voltages
• Receiver Off Hook Test • Ringer Equivalence Test
– No phone or too many phones
• Resistive Faults Test – Wiring shorts
• VeriVoice can be remotely run, providing pass/fail or measured results to the system operator
VeriVoice™ Test Suite Demo
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
VeriVoice™ Test Suite Packages
• Two distinct test packages corresponding to two different levels of coverage– VeriVoice™ Auditor
• Outward looking pass/fail line tests
– VeriVoice™ Professional • Outward looking line tests returning measured results and inward self tests
– The outward looking tests check customer equipment & copper pair leading to it
– The inward looking self tests check the VoIP equipment itself.Tests VeriVoice Auditor VeriVoice Professional Description
Outward Tests
Line Voltage ●1 ●1 Checks for hazardous and foreign AC and DC voltages on the drop
Receiver Off Hook ●1 ●1 Tests for longitudinal fault, off hook restive fault, and receiver off hook
Ringer Equivalence ●1 ●1 Tests the impedance of the line and returns a fail if the REN is too low or too high
Resistive Faults ●1 ●1 Measures three element resistance
All Outward Tests ●1 ●1 Performs all outward tests in correct sequence
Inward Tests
Loopback 3 ●1 Enables receive-to-transmit signal loopback by two different methods
DC Voltage 3 ●1Verifies that the line circuit has the ability to drive the voltage rangers required for the normal operation of the line circuit
DC Feed 3 ●1Measures the voltage and current across a known test load resistor using the DC feed profile that has been programmed
Ring 3 ●1 Verifies ring signal generation, drive capability and ring tip
On/Off Hook 3 ●1 Calculates on-hook and off-hook conditions on the line using the test-load resistor
Read Battery Conditions 3 ●1 Reads the battery voltages connected to the line circuit
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Things to look for in line test software
• Is it easy to integrate with the other software that is running on the device?
• Is it fully tested, characterized and validated against FXS actual silicon?– Or is it merely sample code?
• Has the software been optimized for the particular FXS silicon in your product?
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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
www.ITEXPO.com
Summary
• Metallic Loop Testing Systems (MLTS) or Line Testing has been used for many years in central offices, using big, expensive test heads
• As central office line cards move closer to the home with neighborhood DLCs and MSANs, etc., and residential gateways in the homes, the use of these test heads is no longer practical
• In the NGN VoIP networks the most effective way to implement line testing is through the deployment of software running on processors in residential gateways and other remote line card equipment
• Many VoIP operators are deploying remote line testing capability in their residential gateways resulting in reduced customer support costs and increased customer satisfaction
– More profit and less customer churn!
