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Understanding Quality of Experience

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Due to the high rate of trouble tickets related to inside wiring, ... US Cable MSOs (e.g Comcast, Cox) require GR-909 line testing in EMTAs ... – PowerPoint PPT presentation

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Title: Understanding Quality of Experience


1
Understanding Quality of Experience
  • Diagnostic Tools Line Test (or how to save
    money and increase customer satisfaction)

2
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

3
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.)

4
QoE Improvement Tools - Overview
  • Automated Call Quality Monitoring
  • Many VoIP CPE devices (e.g. Cable EMTAs) 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

5
In-Home Wiring Creates Challenges..
  • 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

6
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.

7
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 (ATAs)
  • 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

8
GR-909 Excerpt (Section 12.4 Testing)
9
TIA-1063 Line Testing Excerpt
10
Test Descriptions
11
Hazardous Voltage Test
  • Tests for the presence of hazardous AC or DC
    voltage on the line
  • AC gt50V or DC gt135V
  • 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

12
Foreign Voltage Test
  • Tests for the presence of foreign AC or DC
    voltage on the line
  • AC gt10V or DC gt6V
  • 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

13
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

14
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

15
Ringer Equivalence Test
  • This test measures the CPE equipments 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

16
GR-909 Pass/Fail Criteria
17
Line Testing Software
  • Example

18
Legeritys 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
19
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.

20
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?

21
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!

22
Thank You
  • rick.bye_at_legerity.com
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