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