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Triple-Play Service Testing Carlene Gardner Strategic Marketing Manager JDSU Cable Networks Division For CCTA Training, San Juan PR, August 26, 2009 Outline Problems in reverse path – What to look for to check carrier health – What causes performance to degrade DOCSIS testing – Recap of process to get online – Tips for testing to check where the problem is VoIP testing – Specific parameters for voice service – Why it is different Future services 2 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Upstream Test Parameters Metric: Carrier to Noise, Signal to Noise Noise 4 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metric: Carrier to Noise, Signal to Noise C/N and SNR, versus the noise floor, are somewhat predictive of BER and MER 5 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metric: MER Modulation Error Ratio (MER) on downstream QAM carrier is similar to S/N or C/N MER on upstream QAMs is similar to SNR read at CMTS MER determines how much margin the system has before failure 6 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metric: MER MER math Indicates how close symbols are to ideal point MER(dB) = 10 x log RMS error magnitude average symbol magnitude Upstream channel fails if MER is not better than – QPSK: 18 dB MER Average – 16 QAM: 24 dB MER symbol magnitude – 64 QAM: 27 dB MER RMS error magnitude 7 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metric: MER of constellation 8 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metric: MER degradation due to noise Symbols cannot reach ideal point due to noise Ideal points 9 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION What Causes MER and BER to degrade? Noise Ingress in Upstream Cause: – Often originating from subscriber’s homes, loose RF connectors, or faulty coax cable – Upstream noise is worse at headend due to “funneling” – A little bit of noise from many locations becomes a lot of noise at the headend Effect – When noise ingress gets too high, data symbols start falling outside their constellation boundaries – The CMTS can no longer correctly determine good data from bad – FEC is no longer able to correct corrupted data packets – The CMTS discards packets with too much data corruption – Web & email traffic will re-transmit and may eventually get through – VoIP traffic is lost forever! 10 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION What Causes MER and BER to degrade? Noise Note that the higher noise floor causes the MER measurement To degrade 11 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION What Causes MER and BER to degrade? Coherent Ingress Cause – Coherent Ingress are carrier waves or other constant carrier signals that exist in the HFC network – Ingress: Often originating from subscriber’s homes, loose RF connectors, or faulty coax cable – Internally-generated impairment: Common Path Distortion (CPD) Effect – Within a DOCSIS upstream channel, can cause intermittent, complete data loss or cause a complete DOCSIS outage – Subscribers may complain about a problem that comes and goes • 24x7 monitoring of ingress is the only way to confidently identify intermittent ingress problems 12 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION What Causes MER and BER to degrade? Compression – Laser / RF Amplifier Cause – Excessive input levels into an active device causing the laser or amplifier to “clip” or not be able to transmit the highest amplitude voltage signals – Not rebalancing upstream devices after a change such as adding another DOCSIS channel Effect – Laser or amplifier clipping causes data loss because the highest amplitude symbols (bits) are pushed into other symbol decision boundaries – Data loss can be continuous or sporadic depending upon system and device conditions – Web traffic can be re-transmitted, but VoIP traffic is permanently lost 13 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION What Causes MER and BER to degrade? Group Delay Cause – Linear changes in phase of a signal – Inherent difficulty of maintaining even speed of propagation through multiple devices, long amplifier cascades – Group delay can also occur due to amplitude changes throughout the upstream band Effect – Frequencies propagate at different speeds through the HFC plant – Group delay affects cable modem signal quality and thus MER – If group delay is bad enough, the CMTS will be unable to recover the transmitted signal and data will be lost (<200 nsec/MHz is spec) – Data and VoIP communications will be impacted or lost completely 14 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION DOCSIS Testing DOCSIS Test – Initialization of a Modem “Ranging” Scan and synchronize to downstream Obtain upstream parameters Range “Registration” Send device class Establish IP connectivity Establish time of day Get operational parameters 16 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Qualify the Drop Verify receive level at cable modem MER shows that downstream is clean and clear with margin BER shows that downstream is clean and clear of impulse noise Upstream is properly aligned and CMTS has “ideal” receive level Packet Loss Throughput 17 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Registration Full list of registration addresses, Service Identifier (SID) and config file assigned Error messages detail where a failed test halted, can help locate source of problem 18 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION IP or RF? 19 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION IP Impairments Traffic Congestion – CMTS Over-utilization – Switch / Router Over-utilization – Viruses, Worms or just General Killer Apps Routing Errors – Cable Modem routes – MTA routes – IP Gateways Provisioning Issues – Subnet Rules – Configuration Files such as TFTP Files – SNMP – BPI & PacketCable Certificates 20 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION VoIP Testing VoIP – Bullet Train Analogy Ideal World: – Packets like train Cars through a station – 1 at a time, evenly spaced, and Fast 22 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION VoIP – Train Analogy Real World – VoIP Packets don’t always do what you want… 23 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metric: MOS Score, R-Factor Test the HFC Performance – VoIP Quality • MOS • R-Value – Processing • Packet Loss • Jitter • Delay 24 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metrics: Delay, Packet Loss and Jitter Delay X-Time X-Time D C B A Point A Network Point B – Time it takes a packet to ‘transverse’ the network – Too much delay affects the quality of a call • Over-talk and Echo • Usually an architecture (traffic/capacity) issue • Generally not a HFC issue with equipment such as amplifiers Aim for 100ms or better 25 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metrics: Delay, Packet Loss and Jitter Packet Loss ∞ -Time X-Time D C B A Point A Network Point B – Packet did not arrive (Point B) or out of sequence – Worse if it is ‘bursty’, many lost in a row – “lossy” – Can be architecture or physical layer • Ingress (especially upstream) • Routers over capacity (too full to hold any more) Aim for 1% or better 26 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Metrics: Delay, Packet Loss and Jitter Jitter X-Time D C B A Point A Network D A B C Point B Slower than X Slower than X Faster than X – Packets not arriving with the same timing (different from X-Time) – time between packets is different – You never notice with Data, doesn’t matter how the information arrives, just care that it shows up but VoIP is Real-Time • Key Causes are IP packet routing, IP based equipment Aim for 10ms or better 27 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Use Metrics to Segment HFC and IP layer Segment HFC and IP impairments – Identify if issues are occurring in HFC Plant or in the IP network Check MOS of VoIP over DOCSIS channel Check VoIP packet statistics – Noise and Ingress on plant are major causes of Packet Loss 28 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Testing the Home for Ingress Contribution 7 dB TAP Return Equalizer House Drop Cable OLDER TV SET WIRELESS LAPTOP DIGITAL SET-TOP COMPUTER GROUND BLOCK 2-Way Amplifier VoIP High Pass Filter ETHERNET 3-Way Splitter eMTA-CABLE MODEM INGRESS SPECTRUM MEASUREMENTS 29 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION ONLINE GAMING Adjust Goals Per Location Test Criteria Service Level Test RF At Home RF At Node 30 © 2009 JDSU. All rights reserved. Degradation Threshold Measurement Goal Delay (1-way) Jitter Packet Loss R-Value MOS MER PRE-FEC BER Rx - Level < 100 ms < 10 ms < 1% > 70 > 3.6 30dB(64), 33dB (256) 1.00E-09 -5~+5 dBmV Tx - Level 35 ~45 dBmV > 150 ms > 15 ms > 2% < 58 <3 25dB(64), 28dB(256) 1.00E-07 <-10dBmV or >+10dBmV < 30dBmV or >50dBmV MER PRE-FEC BER Freq Response 32dB(64), 35dB (256) 1.00E-09 < 4dB 28 dB(64), 31dB(256) 1.00E-07 > 5dB JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Future DOCSIS® 3.0 – Channel Bonding Individual 256 QAM DOCSIS channel Versions 1.0/1.1/2.0 used only one channel for upstream and one channel for downstream communications 256QAM = ~40Mbps (38.8 Mbps) BONDED 4 x 256QAM 4 x ~40Mbps = ~160 Mbps 33 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Trends in the upstream Expanding digital environment – Upstream becoming increasingly crowded – More carriers More challenging than before – Wider carriers offer a wider target for interference – Higher modulation has more sensitivity to ingress 34 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Use constellations to view impairments Microreflections etc. Microreflection pattern over time 35 © 2009 JDSU. All rights reserved. Cloud pattern over time JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Back to the Basics Most problems are still physical layer issues Most of the test strategy remains the same – Divide and conquer Check forward and return RF levels – analog and digital 36 Check for leakage Sweep the forward / reverse to detect issues Replace questionable connectors / passives Tighten F-connectors … but not too tight Robust plant will be ready for the next great thing © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Future Services 37 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION Thank you! Carlene Gardner JDSU Cable Networks Division 38 © 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION