1. Telephony Troubleshooting in the Home
ARRIS/SCTE

2. 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
July 2008

3. 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 consumer’s home over the cable television hybrid fiber coax (HFC) data network.
July 2008

4. PacketCable VoIP Network Components
July 2008

5. 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.
July 2008

6. 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 device’s 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
July 2008

7. 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
July 2008

8. 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
July 2008

9. 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
July 2008

10. E-MTA Installation Customer Education Equipment Features
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
July 2008

11. 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
July 2008

12. HFC Plant Condition Downstream 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:
SNR>30 – green
29<SNR<30 – yellow
SNR<29 – red
For 64QAM we can roughly define:
SNR>23.5 – green
21.5<SNR<23.5 – yellow
SNR<21.5 – red
TM508 Installation and Troubleshooting
April 11, 2017

13. 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 : < -14dBmV or >+14dBmV
TM508 Installation and Troubleshooting
April 11, 2017

14. Transmit Power Level Recommended values(dBmV):
TM508 Installation and Troubleshooting
April 11, 2017

15. Typical Inside Wiring Faults
July 2008

16. Typical Inside Wiring Faults
LEC Line
NID
Alarm Panel
Phone Jacks
Serial wiring
Line
CPE X
Home run wiring
Line
CPE X
Outbound call attempting to contact the monitoring station goes nowhere
WRONG!
July 2008

17. 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.
July 2008

18. Wiring a Security System with RJ31X
Demarcation
EMTA
LEC Line
RJ31X
Jack
Modular
Plug X X
Phone Jacks
Alarm Control Panel R1 T1 R T
Phones
Telco Line
July 2008

19. Wiring a Security System with RJ31X
Demarcation
EMTA
NID
LEC Line X X
RJ31X
Jack
Modular
Plug
Phone Jacks
Alarm Control Panel R1 T1 R T
Phones
Telco Line
July 2008

20. 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
July 2008

21. EMTA RJ-14 Connection to Inside Wiring
Method 2: Using L1/L2 Jack Only
Not used:
Isolated from Main Jack and Line 2 Jacks
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
July 2008

22. 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
July 2008

23. 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
TM508 Installation and Troubleshooting
April 11, 2017

24. 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
July 2008

25. 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
July 2008

26. 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
July 2008

27. Troubleshooting Voice Breaking Up
Congestion in the IP network causes packet loss
As multiple packets are lost, the listener will hear jumps in the speaker’s voice
As more packets are lost the distortion becomes worse and conversation is difficult
July 2008

28. 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.
July 2008

29. 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.
July 2008

30. 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)
July 2008

31. 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.
July 2008

32. 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
July 2008

33. 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
July 2008

34. Troubleshooting Static
May be caused by interference with a cordless telephone (2.4 GHz)
Latency
Jitter caused by congestion in the network
July 2008

35. 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.
July 2008

36. 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.
July 2008

37. 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.
July 2008

38. 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.
July 2008

39. 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.
July 2008

40. 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.
July 2008

41. 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.
July 2008

42. 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.
July 2008

43. 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 Fail—the NIU has detected an AC power failure.
AC Fail Battery Low—the NIU is operating from battery power, and has drawn down the battery to about 25 percent of its rated capacity.
AC Fail Battery Replace—the 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 Replace—the 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.
July 2008

44. 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.
July 2008

45. 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.
July 2008

46. 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.
July 2008

47. 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 V 50-60Hz.
If unit is receiving power from outlet and power cord, replace with another unit.
July 2008

48. 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.
July 2008

49. 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.
July 2008

50. 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.
July 2008

51. 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.
July 2008

52. 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.
July 2008

53. 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.
July 2008