Transcript Understanding Quality of Experience

Understanding
Quality of Experience
Diagnostic Tools – Line Test
(or how to save money and
increase customer satisfaction)
Agenda
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• Who is Legerity?
• Quality of Experience improvement tools
– Automated Call Quality Monitoring
– In-Premise Loop Diagnostics
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Loop/line test background
Key line test specifications
Descriptions of CPE line tests
CPE line test software suite example
Summary
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Who is Legerity
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• 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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QoE Improvement Tools - Overview
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• Automated Call Quality Monitoring
– Many VoIP CPE devices (e.g. Cable EMTA’s) now automatically monitor calls and log
and store metrics
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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
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simple pass/fail results or more extensive test reports
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In-Home Wiring Creates Challenges…..
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
INSIDE HOUSE WIRING is one of the top causes for Trouble Reports.
Due to the high rate of trouble tickets related to inside wiring,
VoIP service providers recognize the need for CPE line testing
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Loop Diagnostics Background
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• ‘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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VoIP CPE Line Testing
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• Service providers recognize the need for VoIP line testing
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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
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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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GR-909 Excerpt (Section 12.4 – Testing)
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
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TIA-1063 Line Testing Excerpt
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
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Test Descriptions
Hazardous Voltage Test
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• 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
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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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Foreign Voltage Test
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• 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
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No Dial Tone
Can not dial out
No phones ring
LC in Protection State
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Resistive Faults Test
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• Tests DC resistance
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Force DC current, measure voltage,
compute the Resistance (Ohms law)
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Tip to Gnd, Ring to Gnd, Tip to Ring
Resistance below threshold indicates a fault
• Possible Cause
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Tip or Ring shorted to cable shield
Moisture in cable
Protection device shorted
Staple or nail shorting Tip and Ring
• Possible Symptoms
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No Dial Tone
No incoming calls
50Hz/60Hz buzz on line due to longitudinal imbalance
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Receiver Off Hook Test
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• The test discriminates between a resistive fault in the loop and a receiver-offhook 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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Ringer Equivalence Test
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• This test measures the CPE equipment’s AC ringer impedance
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20Hz AC Test – tests to see if the FCC part 68 REN load is within range
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REN too high – excessive load, could cause pre-trip faults
REN too low – phone is probably not plugged in
• Possible Cause
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Too many phones connected
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No phone connected
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Exceeds 5 REN
Or less than 0.175 REN
Open in loop
Ringer is open
Faulty phone
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Ringer capacitor shorted
• Possible Symptoms
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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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GR-909 Pass/Fail Criteria
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
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Line Testing Software
Example
Legerity’s VeriVoice™ Test Suite Software
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• 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™ Test Suite Demo
• VeriVoice can be remotely run, providing
pass/fail or measured results to the
system operator
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VeriVoice™ Test Suite Packages
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• Two distinct test packages corresponding to two different levels of coverage
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VeriVoice™ Auditor
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VeriVoice™ Professional
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Outward looking pass/fail line tests
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
Receiver Off Hook
●1
●1
Ringer Equivalence
●1
●1
●1
●1
●1
●1
Loopback
3
●1
DC Voltage
3
●1
DC Feed
3
●1
Ring
3
●1
On/Off Hook
3
●1
Read Battery Conditions
3
●1
Resistive Faults
All Outward Tests
Checks for hazardous and foreign AC and DC voltages on
the drop
Tests for longitudinal fault, off hook restive fault, and
receiver off hook
Tests the impedance of the line and returns a fail if the
REN is too low or too high
Measures three element resistance
Performs all outward tests in correct sequence
Inward Tests
Enables receive-to-transmit signal loopback by two
different methods
Verifies that the line circuit has the ability to drive the
voltage rangers required for the normal operation of the
line circuit
Measures the voltage and current across a known test load
resistor using the DC feed profile that has been
programmed
Verifies ring signal generation, drive capability and ring tip
Calculates on-hook and off-hook conditions on the line
using the test-load resistor
Reads the battery voltages connected to the line circuit
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Things to look for in line test software
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• 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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Summary
September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California
• 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!
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Thank You
[email protected]