Telephony Troubleshooting in the Home

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Telephony Troubleshooting in the Home

• ARRIS/SCTE

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SCTE VoIP Home Troubleshooting Seminar Objectives

• Describe the functional role of each component
  necessary for operation of a PacketCable VOIP
  network.
• eMTA installation
• List common technical problems associated with a
  PacketCable VOIP network
• Discuss impact of network problems on voice
  quality
• Isolate and repair common VoIP problems

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PacketCable Definition

• PacketCable is a set of protocols and associated
  functional requirements developed to deliver
  Quality-of-Service (QoS) enhanced secure
  communications services using packetized data
  transmission technology to a consumers home over
  the cable television hybrid fiber coax (HFC) data
  network.

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PacketCable VoIP Network Components
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PacketCable VoIP Network Components

• The PacketCable architecture is based on many
  components and systems working together.
• Embedded Multimedia Terminal Adapter (E-MTA)
  Single device containing a DOCSIS cable modem and
  a telephony device that provides one or more line
  interfaces
• Cable Modem Termination System (CMTS) Provides
  connectivity between DOCSIS network and
  PacketCable devices also performs call
  authorization enforcement, bandwidth allocation,
  and call trace functions
• Call Management Server (CMS) Provides call
  control and signaling services for the MTA, CMTS,
  and PSTN gateways typically performs both Call
  Agent (handles call state) and media gateway
  controller (authorization) functions as well.

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PacketCable VoIP Network Components

• SYSLOG server Optional server used to collect,
  store, and retrieve logging messages for devices
  on the network
• DHCP Server Provides initial boot-up networking
  information such as the querying devices IP
  addresses, next-hop routers, server information,
  etc.
• DNS Server Provides translation between the
  Domain name and the IP address of a device
• TFTP/HTTP server Provides download capability
  for device configuration files

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PacketCable VoIP Network Components

• Announcement Controller (ANC) Initiates and
  manages all announcement services that are
  provided by the announcement player
• Announcement Player (ANP) Delivers the
  appropriate announcement(s) to the MTA under
  control of the announcement controller
• Key Distribution Center (KDC) Performs security
  key negotiations for MTA and Provisioning Server
  in the PacketCable network
• Record Keeping Server (RKS) Collection point for
  all PacketCable Event Messages may also
  correlate Event Messages to create Call Detail
  Records for billing interfaces

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PacketCable VoIP Network Components

• Provisioning Server (OSS) Provides provisioning
  information for PacketCable devices via SNMPv3
• Delivery Function (DF) Aggregation point for
  electronic surveillance delivers reasonably
  available call-identifying information and call
  content based on the requirements of lawful
  authorization
• Media Gateway Controller (MGC) Provides bearer
  mediation between the PSTN and the PacketCable
  network
• Media Gateway (MG) Provides media (voice
  packets) connectivity between the PSTN and the
  PacketCable network
• Signaling Gateway (SG) Provides signaling
  mediation between the PSTN and the PacketCable
  network

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E-MTA Installation

• The following should be standard installation
  practices
• Pre Installation inspection
• Check for proper RF levels.
• Check for damage or condition of splitters and
  couplers in Coax Drop
• Check inside wiring for continuity at all jacks
• Check for shorts or foreign voltages (AC or DC)
• Check NID for proper wiring and ensure LEC
  connection is physically disconnected
• Post Installation validation
• Check for dial tone at all jacks
• Make test calls on all customer premise equipment
• Educate customer on equipment and features

Comprehensive Methods Procedures and Thorough
Training of Installation Personnel Are Key
Factors for Success
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E-MTA Installation

• Customer Education
• Equipment
• Customers need to be educated to not unplug the
  EMTA or connect to a switched outlet otherwise
  phone service can be disrupted
• Customers need to understand that EMTA consumes
  very little standby power - similar to a night
  light.
• Educate customer to not place EMTA where liquids
  may be spilled into it
• Features
• Educate customer on how to use call features,
  provide reference literature/handbook
• Educate customer that certain features require
  compatible CPE e.g. Call Waiting Deluxe, Caller
  ID, Message Waiting Indicator

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Troubleshooting

• Causes of Voice Problems
• HFC plant condition
• Typical inside wiring faults
• No dial tone
• Too much delay on calls
• Voice breaking up
• The caller hears voice distortion
• Echo
• Static on the line
• Calls will not go through
• Voice in only one direction

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HFC Plant ConditionDownstream Signal Noise Ratio

• The SNR reported by the CM is a rough estimation
  of the signal to noise ratio at the F-connector.
  It is based on Modulation Error Ratio (MER).
• PHY performance beyond DOCSIS requirements is
  implementation dependent and some devices may be
  able to operate in presence of SNR values which
  are significantly lower than DOCSIS requirements.
• Thus, we provide following thresholds as values
  for troubleshooting but some devices may be able
  to be functional even in yellow or red SNR
  indications.
• For 256QAM we can roughly define
• SNRgt30 green
• 29ltSNRlt30 yellow
• SNRlt29 red
• For 64QAM we can roughly define
• SNRgt23.5 green
• 21.5ltSNRlt23.5 yellow
• SNRlt21.5 red

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RF Receive Power Level

• RF Receive level should have enough margin to
  allow for plant drift
• Range is -15dBmV to 15dBmV
• Recommended values
• GREEN -13dBmV to 13dBmV
• YELLOW -14dBmV to -13dBmV or
• 13dBmV to 14dBmV
• RED lt -14dBmV or gt14dBmV

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Transmit Power Level

• Recommended values(dBmV)

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Typical Inside Wiring Faults
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Typical Inside Wiring Faults
LEC Line
Phone Jacks
NID
Alarm Panel
Serial wiring
X
Home run wiring
X
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RJ31X Plug for Security Systems

• Used to connect security system control panel to
  home telephone wiring.
• Ensures control panel can disconnect phone users
  and has priority to seize the line to call the
  alarm monitoring station.

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Wiring a Security System with RJ31X
Demarcation
EMTA
LEC Line
X
X
Phone Jacks
Alarm Control Panel
R1
R
T
T1
Telco Line
Phones
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Wiring a Security System with RJ31X
EMTA
Demarcation
NID
LEC Line
X
X
Phone Jacks
Alarm Control Panel
R1
R
T
T1
Telco Line
Phones
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EMTA RJ-14 Connection to Inside Wiring
Method 1 Using L1/L2 and L2 Jacks
Not used
EMTA
Line 1 Jacks
Main Line 1 Jack
L1/L2 Jack
Line 1 Circuit
Line 2 Circuit
L2 Jack
Main Line 2 Jack
Line 2 Jacks
Separate 2 conductor cords to connect lines 1 and
2
Not used
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EMTA RJ-14 Connection to Inside Wiring
Not used Isolated from Main Jack and Line 2
Jacks
Method 2 Using L1/L2 Jack Only
EMTA
Line 1 Jacks
Main Jack
L1/L2 Jack
Line 1 Circuit
Line 2 Circuit
L2 Jack
Line 2 Jacks
RJ14 Feature Facilitates distribution of 2 lines
with a single 4 conductor phone cord
Not used Isolated from Main Jack and Line 1
Jacks
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Typical Inside Wiring Faults
Not used Not Isolated from Main Jack
Fault in wiring or jack causes L1 to L2 short
circuit
Method 2 Using L1/L2 Jack Only
EMTA
Line 1 Jacks
Main Jack
L1/L2 Jack
Line 1 Circuit
Line 2 Circuit
L2 Jack
Line 2 Jacks
RJ14 Feature Facilitates distribution of 2 lines
with a single 4 conductor phone cord
Not used Isolated from Main Jack and Line 1
Jacks
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Dial Tone Issues - Potential Root Causes

• EMTA Provisioning Unsuccessful
• Line card or house wiring issue (Line Card
  Protection state)
• DNS Server lookup issues (CMS or FQDN)
• Call Signaling messaging protocol problems
  between EMTA and CMS
• Slow or delayed response from CMS
• ARP Issues
• DHCP Lease expiration / obtaining new IP address
• Insufficient Bandwidth on CMTS / Lack of US
  Grants
• Intermittent Packet loss and packet retransmits
  due to RF impairment or RF noise
• T4 timeout loss of RF connectivity

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Troubleshooting Dial Tone Issues

• Provisioning
• Verify that the E-MTA or NIU is registered with
  the CMTS
• Verify that the CMTS has connectivity to the VoIP
  Switch
• Verify the VoIP Switch has connectivity to the
  E-MTA or NIU via ping
• Verify that the E-MTA or NIU has the correct IP
  address for its call agent
• Verify that the subscriber is entered in the VoIP
  Switch database and is active

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Troubleshooting Dial Tone Issues

• DNS Look Up Failure
• If the CMS FQDN DNS queries are unsuccessful then
  the MTA will not be able to send messages to the
  CMS
• ARP Problems
• If the MTA does not receive a response to an ARP
  at the beginning of the call there is no
  mechanism in place to retry

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Troubleshooting Call Delay

• Users notice delay when the end-to-end delay
  exceeds 150ms. At this point, voice quality may
  be acceptable, but the delay is not. When this
  situation occurs, the processing capabilities of
  the E-MTA and/or MG are overwhelmed and not
  processing voice traffic efficiently
• Buffering reduces jitter in the network however,
  it also adds delay as the traffic is adjusted to
  a fixed rate

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Troubleshooting Voice Breaking Up

• Congestion in the IP network causes packet loss
• As multiple packets are lost, the listener will
  hear jumps in the speakers voice
• As more packets are lost the distortion becomes
  worse and conversation is difficult

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Troubleshooting Echo

• What is echo?
• In a voice telephone call, an echo occurs when
  you hear your own voice repeated, somewhat
  attenuated and delayed
• An echo is the audible leak-through of your own
  voice into your own receive (return) path.
• The louder the echo, the more annoying it is.
• The longer the delay, the more annoying it is.

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Troubleshooting Echo

• Where does echo originate?
• 1. A signal is leaking from the transmit into the
  receive path
• Leaking in analog circuits only.
• Cross-talk
• electrically from one wire to another
• acoustically through the air from a loudspeaker
  to a microphone.
• Reflections in the hybrid part of the analogue
  side
• Telephone set, house wiring, dect
• Voice traffic in the digital part of the network
  is highly unlikely to leak
• 2. The original signal and the leaked signal
  arrive at the subscribers ear at different times
  due to difference in delay between the travel
  path of the original and reflected signal.

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Troubleshooting Echo

• The friends of echo
• Delay
• 25 milliseconds (ms) or less delay is inaudible
  PSTN calls typically have less delay in the
  network, and therefore are unlikely to have echo
  issues
• VoIP networks typically have delays well above
  25ms, so enough room for the echo to become
  annoying
• Over 400ms delay for a phone call is annoying
  even without echo
• Amplification/Attenuation
• Echo should be 55dB below original speech to not
  be considered annoying
• Amplification and attenuation occur at various
  places in an end-to-end call, and will be
  different for calls to and from different
  networks (fixed, cell, international, different
  providers etc)

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Troubleshooting Echo

• Avoiding echo
• Reflections are a result of impedance mismatches
• Line card templates set the impedances
• Phones should be approved for the country in
  which they are used
• Speaker phones can easily cause acoustic echo
• DECT phones are suspect as well
• Remember Echo at subscriber A is likely to
  originate at the remote end of a call (subscriber
  B), therefore it may not originate in your part
  of the network, even though your subscriber is
  the one hearing the echo, not the remote
  subscriber.

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Troubleshooting Echo

• Echo in digital segments
• I really said the digital portion of the network
  does not cause echo but..
• we resolved echo several times by applying
  changes in the digital portion..
• The digital portion of the network can add delay,
  are amplification which makes Echo visible
• Removing this delay / amplification may remove
  the annoyance level of the echo
• Delay changes due to
• Additional network elements (e.g.router)
• Changes in jitter buffers, packetization rates
• Amplification changes due to
• Different gain/loss settings in gateways /
  switches / trunks

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Troubleshooting Voice Distortion

• Caused by tandem encoding
• With this encoding (also called dual encodings or
  dual compressions), digital calls routed to a
  tandem (toll) office are converted to analog form
  for processing and then reconverted to digital
  form for further transmission
• Converting and reconverting more than twice
  damages the signal and causes voice distortion

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Troubleshooting Static

• May be caused by interference with a cordless
  telephone (2.4 GHz)
• Latency
• Jitter caused by congestion in the network

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Troubleshooting calls that will not go through

• Problems with the CMS - during busy times it
  cannot handle another call setup.
• PSTN-bound calls may bombard the MG and/or MGC to
  the point that they cannot handle any more calls.
• The SG may not be receiving proper messages from
  the PSTN.
• The call may not be set up properly through the
  PSTN.
• Congestion in the network
• The signaling information may be dropped by the
  network.

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Troubleshooting One Way Speech Path

• Causes for one-way audio are usually IP routing
  or HFC issues.
• Routing may not be enabled on the routers or
  there may be a problem with default gateways
  configured at end stations.
• Determining the direction of the one way speech
  path is useful in order to isolate DS and US
  specific issues.

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Troubleshooting EMTA Power Problems

• The E-MTA is plugged in, but the Power light is
  off.
• Check all power connections.
• Is the AC adapter plugged in firmly at both ends?
• If you plugged the AC adapter into a power strip,
  make sure the strip is switched on.
• Avoid using an outlet controlled by a wall
  switch, if possible.
• Finally, check the fuse or circuit breaker panel.

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Troubleshooting Internet Access Issues

• It may take up to 30 minutes to establish a
  connection the first time you power up the E-MTA.
• Some E-MTA have Standby that isolate PC from the
  Internet.
• Check the front panel lights
• The Power and Online lights should be on.
• If the Online light is blinking, press the
  Standby button.
• The Link light should be either on or blinking.
• If the Power light blinks for more than 30
  minutes, call your cable company for assistance.

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Troubleshooting Internet Access Issues (continued)

• Check your cable connections. Connectors should
  be finger-tight.
• The coax cable should not be pinched, kinked, or
  bent sharply.
• Any of these issues can cause a break or short in
  the cable (you may have to replace the cable).
• If you have one or more splitters between the
  E-MTA and CATV outlet, remove the splitters and
  connect the E-MTA directly to the outlet.

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Troubleshooting Internet Access Issues (Ethernet)

• If you are using a hub, is the hub turned on?
• Are you using the right type of Ethernet cable?
  (Straight cable for direct connection to a PC,
  cross-over cable for connection to a hub.)
• Press the Reset button on the back of the E-MTA.

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Troubleshooting Slow Internet Access

• If the Web site you are visiting is very popular,
  that site may be having trouble servicing all the
  requests. If other sites download quickly, wait
  for a few minutes and try again.
• Usage during peak hours may also affect the
  connection speed.
• If your E-MTA is connected to a LAN (Local Area
  Network), either directly or through a firewall,
  other communications on the LAN may slow down
  your connection.

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Troubleshooting EMTA Alarms

• Call Agent Loss of Communications
• Severity Major, service-affecting
• Cause One of the following conditions has
  occurred
• The MTA did not receive a response from the Call
  Server for an NCS message. Re-establishing
  communications with the Call Server clears this
  alarm.
• The E-MTA received a NACK in response to the RSIP
  message that it sent on initial registration to
  the call agent, resulting in CallP functionality
  entering a permanent error state. Clearing the
  condition that caused the NACK clears this alarm.
• Impact The NIU cannot register or initiate
  calls.
• Action Check the status of the NIU and its
  network connection.

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Troubleshooting EMTA Alarms

• Power Supply Telemetry
• Severity Major, service-affecting
• Cause The NIU has lost AC power. The alarm
  includes one of the following battery status
  codes
• AC Failthe NIU has detected an AC power failure.
• AC Fail Battery Lowthe NIU is operating from
  battery power, and has drawn down the battery to
  about 25 percent of its rated capacity.
• AC Fail Battery Replacethe NIU is operating from
  battery power, and the battery has deteriorated
  to about 75 percent of its off-the-shelf capacity
  and should be replaced.
• AC Fail Battery Low Replacethe NIU is operating
  from battery power, and has drawn down the
  battery to about 25 percent of its rated
  capacity. In addition, the battery has
  deteriorated to about 75 percent of its
  off-the-shelf capacity and should be replaced.

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Troubleshooting EMTA Alarms

• Power Supply Telemetry (continued)
• Impact None at time of alarm. Depending on the
  condition of the battery and the nature of the
  power failure, the NIU may exhaust the battery
  before AC power is restored.
• Action Depends on the scope of the power outage.

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Troubleshooting EMTA Alarms

• Voice Line Failure
• Severity Major, service-affecting
• Cause One of the following conditions has
  occurred
• An In-Service line card has detected a Line Card
  Protection Fault condition (an overcurrent
  protection state). A Line Card Protection Fault
  occurs when the line card detects foreign voltage
  between tip and ring, or there is an excessive
  imbalance in loop current.
• An attempt was made to put an Out-of-Service
  line, in an overcurrent protection state, into
  service.

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Troubleshooting EMTA Alarms

• Voice Line Failure (continued)
• Impact The affected voice line is disabled. Look
  for Voice Line Protection State Change logs to
  determine which line is in the fault condition.
• Action Run the line card diagnostics on the NIU.
  If the NIU fails diagnostics, disconnect the
  house wiring from the NIU and proceed as follows
• If the alarm clears, correct the faulty house
  wiring.
• If the alarm persists, replace the NIU.

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E-MTA Registration - Common Problems

• Power - Telephony modem is not receiving AC
  power.
• Verify power cord is plugged into an unswitched
  outlet.
• Verify power cord by measuring with voltmeter.
  Voltage should be 100-240V 50-60Hz.
• If unit is receiving power from outlet and power
  cord, replace with another unit.

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E-MTA Registration - Common Problems

• Downstream Scanning - Telephony modem is not able
  to lock onto a downstream signal.
• Verify cabling from house splitter to unit.
• Verify Downstream signal level at assigned
  frequency is within the telephony modem Rx range
  -15dBmV to 15dBmV.
• If no signal, verify the drop by measuring a CATV
  channel level for proper level at the CPE
  demarcation point.
• If CATV channel is at the proper level, contact
  head end to verify CMTS is transmitting.
• If CATV channel is not present, troubleshoot drop
  cable from the tap.
• If Downstream signal is at proper level, replace
  unit.

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E-MTA Registration - Common Problems

• Upstream Ranging E-MTA is not able to
  establish upstream communications with the CMTS.
• Verify cabling from house splitter to unit.
• Verify upstream path by sending signal back to
  head end and measure for proper level.
• Contact head end to verify CMTS RF level is set
  to proper level.
• If Upstream signal loss is at proper level,
  replace unit.

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E-MTA Registration - Common Problems

• DHCP E-MTA is not receiving a IP address for
  the data component from the DHCP server.
• Contact head end to verify DHCP server is
  functional and receiving address requests from
  unit.
• Head end should verify provisioning information.

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E-MTA Registration - Common Problems

• TFTP E-MTA is not able to download the
  configuration file for the data component from
  the TFTP server.
• Contact head end to verify TFTP server is
  functional and receiving configuration file
  requests from unit.
• Head end should verify provisioning information.

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E-MTA Registration - Common Problems

• Telephony DHCP E-MTA is not receiving an IP
  address for the MTA component from the Telephony
  DHCP server.
• Contact head end to verify Telephony DHCP server
  is functional and receiving address requests from
  unit
• Head end should verify provisioning information.

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E-MTA Registration - Common Problems

• Telephony TFTP E-MTA is not able to download
  the configuration file for the MTA component from
  the Telephony TFTP server.
• Contact head end to verify Telephony TFTP server
  is functional and receiving configuration file
  requests from unit.
• Head end should verify provisioning information.