081204 VUG C4 RF Troubleshooting

www.arrisi.com

ARRIS C4 CMTS:RF TROUBLESHOOTING

Mike ElliottARRIS Technical Support

Overview

This webcast will cover RF troubleshooting techniques for the ARRIS C4 CMTS. We will discuss how to identify RF problems and ways to mitigate them. We will also cover DOCSIS RF levels, Cable Access Module (CAM) operation and sparing, RF noise mitigation features, SNR, DOCSIS ping, cable flap lists and the Intelligent Channel Optimizer (ICO).

This Webcast will be focused on the 2D12U CAM capabilities and Firmware version 5.x

ARRIS Confidential and Proprietary

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Technical Services User Group C4 CMTS RF Troubleshooting

Agenda

DOCSIS RF Levels 2D12U CAM RF Specs Ranging Process Modulation Profiles CAM Sparing SNR/MER Noise Types Show cable noise Remote query Forward Error Correction Ingress Cancellation Pre-Equalization DOCSIS Ping Cable Flap-List Modulation vs Noise Basic Troubleshooting ICO Q & A


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DOCSIS RF Levels

Downstream (Rx) Receive Power (Forward Signal) level: - Modems input power range: -15 to +15dBmV

Upstream (Tx) Transmit Power (Return Signal) level: - QPSK Burst +8 to +58 dBmV- 8 & 16QAM Burst +8 to +55 dBmV- 32 & 64QAM Burst +8 to +54 dBmV

Recommended upstream CM Tx signal levels are +35 dBmV to +50 dBmV.

Signal levels not within the specifications listed above can cause slow speeds connection problems, and connection loss due to packet errors, packet loss, and/or constant packet retransmission.


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CAM Downstream RF Specifications

Each Downstream supports:- DS Frequency (DOCSIS): 91 to 857 MHz (fc)

Integrated upconverter- DS Frequency (EuroDOCSIS): 112 to 858 MHz (fc)

Integrated upconverter- DS variable output power: 50-61dBmV - DS Automatic Gain Control (AGC)- DS Modulation: 64QAM & 256QAM- DS Interleave - depth in number of taps (8,16,32,64, 128, or 12 for EuroDOCSIS)

Default Interleave-depth is 32

Note: Front panel DS test ports are -30dB and is only for verification of DS power. This port is not intended for MER/BER measurements.

Here is a useful CLI command to check the CAM downstream power This will provide the power level reading just before the CAM DS output connector that connects to the backplane.

C4# show controllers cable 2/0 downstream | include db- Provisioned Power (tenth of dBmV): 610- Measured Power (tenth of dBmV): 608


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CAM Upstream RF Specifications

12 Upstream (US) receivers Range of upstream frequencies configurable for North America, Japan,

or Europe:- - 5-42 MHz (DOCSIS)- - 5-55 MHz (Japan)- - 5-65 MHz (EuroDOCSIS)

Flexible US/DS mapping multiple USs per connector Multiple logical channels (2) per physical upstream channel Modulation types: TDMA/ATDMA/TDMA&ATDMA/SCDMA Symbol Rates: QPSK, QAM8, QAM16, QAM32, QAM64 Channel Widths: 200kHz, 400kHz, 800kHz, 1600kHz, 3200kHz,

6400kHz Adjustable receive power Supports per Upstream Ingress Cancellation (ICB) Supports per Upstream Pre-Equalization Supports Forward Error Correction (FEC) Supports Upstream Interleaving


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Ranging Process

CM scans for a downstream channel CM synchronizes to the downstream channel CM locks on the time-base clock CM receives upstream parameters (UCD US Channel

Descriptor) CM receives bandwidth allocation MAP CM performs ranging (power, timing and frequency

adjustments) CM establishes IP connectivity (DHCP) CM establishes Time of Day (TOD) CM acquires configuration file (TFTP) CM registers with the CMTS CM is operational


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Ranging Process

During modem initialization, the CM will range with the CMTS to fine-tune timing offset, center frequency, and its upstream power level. Every time the modem sends up a ranging request, the C4 will respond back with a ranging response, asking the modem to adjust its upstream power, frequency, and/or timing offset. When the upstream power level is within the desired/configured upstream power level, within the desired timing offset, and within the desired center frequency, the modem will be ranged and will then begin DHCP.

The Insertion-interval is how often a modem is offered a broadcast ranging opportunity

configure interface cable / cable downstream insertion-interval The default is 40, to speed up modem registration set to 10.

After the CM has registered, the C4 will grant the CM periodic ranging opportunities on the upstream. The process works as before until the CM is within the acceptable limits. The frequency of these periodic ranging opportunities is provisioned via:

configure interface cable / cable downstream ranging-interval The default to 2400


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Ranging Process

The Station maintenance interval uses the IUC 4 burst parameters defined in the modulation profile.

If the modem is not within the thresholds with the first station maintenance ranging burst (ranging continue as opposed to ranging success), it stays on the ranging polling queue and will get station maintenance opportunities every period of time until it gets a ranging success.

The ranging cycle time is configurable, but defaulted to 1.2 seconds (120 centi-seconds).

It's not a good idea to play around with the ranging-cycle time on a live site.


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Modulation-profiles

Modulation Profiles:- Modulation Profiles define all the burst parameters for each upstream burst

type. Each Interval Usage Code (IUC) has a specific set of burst parameters.- Profiles can be changed on the fly without modems dropping offline- FEC can be modified for each IUC (usually only modified on short/long data

IUCs if needed)- The C4 CMTS automatically generates default profiles for all modulation

typesC4# configure cable modulation-profile 2 tdma qpskC4# show cable modulation-profile 2

Modulation profile 2

Interval Chan Mod Pre Dif FEC FEC Scr Max Guar L Scr ---Atdma--- Prea -----Scdma-----Usage Type Type Len Enc CW amb Bur Time C amb Int Int mble TCM Int Sp SubCode En Len Seed Siz Size S En Depth Block Type En Size En Cod------------------------------------------------------------------------------------------------1 request tdma qpsk 64 F 0 16 338 0 8 F T - - - - - - -3 initial tdma qpsk 640 F 5 34 338 0 48 F T - - - - - - -4 station tdma qpsk 384 F 5 34 338 0 48 F T - - - - - - -5 short tdma qpsk 84 F 6 78 338 45 8 T T - - - - - - -6 long tdma qpsk 96 F 8 220 338 0 8 T T - - - - - - -


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Channel width & bit rates


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QPSK 16QAMChannel Width Bit-rate (kbps) Bit-rate (kbps)

200 320 640400 640 1280800 1280 25601600 2560 51203200 5120 10240

ATDMA

SCDMA

8QAM 16QAM 32QAM 64QAMChannel Width Bit-rate (kbps) Bit-rate (kbps) Bit-rate (kbps) Bit-rate (kbps)

200 480 640 800 960400 960 1280 1600 1920800 1920 2560 3200 38401600 3840 5120 6400 76803200 7680 10240 12800 153606400 15360 20480 25600 30720

8QAM 16QAM 32QAM 64QAMChannel Width Bit-rate (kbps) Bit-rate (kbps) Bit-rate (kbps) Bit-rate (kbps)

1600 3840 5120 6400 76803200 7680 10240 12800 153606400 15360 20480 25600 30720

TDMA


CAM Sparing

CAM sparing minimizes traffic loss and customer impact in case of a module failure.

When an active CAM in a spare group fails, the spare CAM takes over almost seamlessly.

The cable modems that were connected to the upstream and downstream channels on the failed CAM are immediately connected to the spare CAM.

Cable modems do not have to re-range or re-register, and they incur minimal data loss.

Failback (The recovered CAM becomes active, taking over for the spare) from the spare CAM to a recovered CAM can be set to take place automatically or manually

- Spare-groups require all CAM rear PICs to be in place- Approximately 0.5dB of DS RF loss per slot when sparing and 0.1dB of RF loss US- DS & US RF is routed to/from spare CAM via the mid-plane through the rear PICs using RF

sparing relays- RF Sparing relays are activated via the active SCM- CAM Sparing is hitless (modems do not drop offline)- CAM sparing can only be done by like cards: a 1Dx8U can spare for only a 1Dx8U and a

2Dx12U can spare only for a 2Dx12U. No mixing is allowed in the sparing groups


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SNR/MER

US SNR is actually MER on the C4 CMTS - MER is calculated based on the average "error-vector"

magnitude that the upstream receiver reports per-burst. This is basically how far each demodulated QAM symbol was off from the ideal QAM symbol.

MER tells more about the quality of the RF burst- SNR only gives the ratio of noise floor power to the peak US

burst power (its doesnt provide any information about the in-channel impairments.

- There must be modems ranging on the US for MER to be calculated and provide an output.

- When large amount of modems are registering, the channel MER may report low due to the Initial ranging of the modems (this time slot is contention based so there will be some collisions causing lower MER until modems are ranged/registered)


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Noise Types

Some common linear distortions:- Micro-reflections: Caused by impedance mismatches that will reflect some of the incident

energy (US Burst) back to the source (cable modem).- Group delay: When signals at some frequencies take longer to travel through a network than

other frequencies.- Amplitude ripple/tilt: Caused by micro-reflections and poor frequency response.

Some common non-linear distortions:- CSO: Composite Second Order - is the ratio of carrier to Composite Second Order Beat- CTB: Composite Triple Beat/Composite Third Order - is the ratio of carrier to Composite

Third order Beat. - CPD: Common Path Distortion Distortion products generated from the DS (6/8MHz)

interacting with corroded connections. These distortion products are found in the return path.

- Ingress: A common type of noise found on HFC cable networks, occurs at a single spectral frequency. Common sources of this type of noise include CB (citizen band) radios and other communications devices

- Spurs: Spurious Emissions Narrow band CW noise from external sources, CTO/CTB and CPD

- Impulse: Short duration noise bursts that can be narrowband or broadband CSO & CTB: Both of these distortions are the result of multiple carriers experiencing second and third

order non-linearity , generating multiple distortion products.


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show cable noise

The CLI command show cable noise is clear on read Measures MER and FEC per logical US channel MER is calculated from the last 10,000 US symbols collected from all

IUCs There must be at least 1 modem on a logical US channel to calculate

MER/FEC.- If there is less than 100 modems on an US or not much US traffic, ping a modem

or two with 5000 1000 byte packets to provide more bursts/symbols to calculate the channel MER more accurately.

- Impulse noise can produce FEC errors when MER appears good.- Short duration impulse noise may only corrupt some of the US bursts and will be

averaged out of the MER reading by all the bursts that are passed upstream when there is no impulse present, showing a good MER reading. The codewordsthat may get corrupted will show up as FEC_corrected or FEC_uncorrectederrors.

- FEC_corrected Errors and NO FEC_uncorrected indicates FEC is doing its job but is a sign of noise issues in the plant. This should be addressed before customers service becomes degraded.

- Microreflections listed in show cable noise are always zero (not supported)


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show cable noise

C4# show cable noise cable 2

CAM/DS/US SNR(dB) MicroReflection FEC_Unerrored FEC_Corrected FEC_Uncorrected----------------------------------------------------------------------------------2/0/0.0 40.1 0 1151 0 02/0/1.0 26.0 0 491 20 02/1/6.0 19.0 0 40232 223 342/1/7.0 31.0 0 27544 151 209

C4# show interface cable 2 DS Oper Annex Freq(Hz) Mod Power Clone Spare LBal true 0State Type (.1dBmV) Enable Group Group2/0 IS B(US) 321000000 q64 610 true 02/1 IS B(US) 627000000 q256 500 US Conn Oper Chan Freq(Hz) Channel Mini Mod Power Cable LBal

State Type Width Slot Prof (dBmV) Group Group2/0/U0 0 IS tdma 35000000 3200000 4 2 0 - -2/0/U1 1 IS atdma 20000000 6400000 2 114 0 - -2/1/U6 6 IS tdma 26900000 3200000 2 6 0 - -2/1/U7 7 IS tdma 30100000 3200000 4 6 0 - -


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show cable modem

C4# show cable modem 0000.ca31.7352 Dec 3 11:33:48

Prim DOC Timing Rec Interface State SID SIS Offset Power Qos CPE IP Address MAC address --------- ---------- ---- --- ------ ----- ------------- --- --------------- --------------2/0/0 Registered 4917 1.0 2010 0.0 QoSProf 1 0 192.168.136.6 0000.ca31.7352 (Arris)

Total Offline Ranging RgAbort Ranged IPcompl BpiInit Online Denied-----------------------------------------------------------------------------------Found 1 0 0 0 0 0 0 1 0

C4# show cable modem 0000.ca31.7352 detail Dec 3 11:32:29

2/0/0.0 CM 0000.ca31.7352 (Arris) D1.0 State=IPcomplete D1.0/tdma PrimSID=4882 Timing Offset=2006 Rec Power= 0.00 dBmV Proto-Throttle=NormalUptime= 0 days 0:00:11 IP=192.168.136.6 cfg=generic-docsis-2Meg-1-0.binPrivacy=Initializingu/d SFID SID State Sched Tmin Tmax DFrms DBytes MFrms MBytes CRC HCSu 25945 4882 Activ BE 0 0 5 1327 - - 0 0d 25946 *4882 Activ 0 0 1 64Current CPE=0 Max CPE=0


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show cable modem summary

C4# show cable modem summary slot 2 Channel Conn Total Offline Ranging RgAbort Ranged IPcompl BpiInit Online Denied RngFlap PrvFlap RegFlap

2/0/0.0 0 20 0 1 0 1 3 0 15 0 0 3 1935 2/0/0.1 0 0 0 0 0 0 0 0 0 0 0 0 10 2/0/1 1 1 0 0 0 0 0 0 1 0 0 0 151 2/1/6 6 3 0 0 0 0 0 0 3 0 0 0 0 2/1/7 7 0 0 0 0 0 0 0 0 0 0 0 0 ----------------------------------------------------------------------------------- -----------------------

2/0 Total 21 0 1 0 1 3 0 16 0 0 3 2096 2/1 Total 3 0 0 0 0 0 0 3 0 0 0 0 2 Total 24 0 1 0 1 3 0 19 0 0 3 2096 ----------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------- -----------------------

Total 24 0 1 0 1 3 0 19 0 0 3 2096

To clear the flap-list and flap counts under the summary view use the following CLI.

C4# clear cable flap-list slot 2 Flap counts have been cleared for slot 2

Use clear cable flap-list all to clear all flaps from the system.


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show controllers downstream

C4# show controllers cable 2/0 downstream Downstream Port 0---------------

Port state: ISCable Standard: Annex B from ITU-J83Frequency (Hz): 321000000Insertion interval (centiseconds): 40Interleave depth (no of taps): 32Invited ranging attempts: 16Modulation: q256Provisioned Power (tenth of dBmV): 610Measured Power (tenth of dBmV): 610Power Fine Adjustment (steps): 0Ranging interval (centiseconds): 2400Sync interval (milliseconds): 10UCD interval (milliseconds): 1600Max Round Trip Delay(microseconds): 1580Ranging Cycles Int (centiseconds): 120Clone Group Enabled: True (Hard timeouts enabled for IM opport)Load Balance Group Id: 200, 201, 202, 203Level 3 overload threshold: 500Max Allowable Normal Voice BW (%): 90Reserved Normal Voice BW (%): 0Max Allowable Emergency Voice BW (%): 90Reserved Emergency Voice BW (%): 0Max Allowed Total (Emergency + Normal) (%): 90Emergency Preemption: enabledTFTP Enforcement: enabledDynamic Secret: disabledToken Bucket Mode: shapeAutomatic Gain Control: enabled


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show controllers upstreamC4# show controllers cable 2/0 upstream 0

Upstream Port 0-------------

Port state: ISAssigned Upstream Connector: 0Assigned Downstream Port: 0Frequency (Hz): 35000000Channel width (Hz): 3200000Equalizer Coefficient State: offPower (dBmV): 0Max Power Adj Per Range Resp (1/4 dBmV): 24Ranging Power Thresh For Success (1/4 dBmV): 48Frequency priority list id: -Cable Group id: 1Clone Group id: -Load Balance Group Id: -Level 3 Overload Threshold (%): 1000Max Allowable Normal Voice BW (%): 50Reserved Normal Voice BW (%): 0Max Allowable Emergency Voice BW (%): 70Reserved Emergency Voice BW (%): 0Max Allowed Total (Emergency + Normal) (%): 70Ingress Cancellation Interval: 100Ingress Cancellation Size: 0Logical Channel: 0 1 (continued output)----------------------------------------------------------- SCDMA active codes: - -Channel State IS IS SCDMA codes per slot: - -Channel Type: tdma tdma SCDMA frame size: - -Modulation profile id: 2 6 SCDMA hopping seed: - -FlexPath Only: no no Spectrum Group ID: - -Ranging backoff range: 5 - 9 5 9 Spectrum Group State: - -Data backoff range: 2 - 8 2 - 8Map Size (800 microsecond ticks): 4 4 Slot Size (6.25 microsecond ticks): 4 4


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show cable modem phy (remote-query)

The show cable modem phy output will display the US MER for a individual modem as well as CM and CMTS measurement levels.

Capability to change the source ip of the snmp requests to the cable modems which allows the cable filters to block requests from the IPANY address 0.0.0.0 and udp port 162

C4# configure cable modem remote-query ? - Seconds between two polling cycles of CM data collection WORD - The read community string used for polling CMs source-interface - Configure cable modem SNMP remote query source interface

C4# configure cable modem remote-query source-interface ? cable - Configure cable modem SNMP remote query source interface to cablefastEthernet - Configure cable modem SNMP remote query source interface to fastEthernetgigabitEthernet - Configure cable modem SNMP remote query source interface to gigabitEthernetloopback - Configure cable modem SNMP remote query source interface to loopback

C4# configure cable modem remote-query source-interface cable ? /[.] - CAM slot number/MAC domain number[.subinterface number]

C4# configure cable modem remote-query source-interface cable 1/0C4# show ip interface brief Interface Primary IP Admin Oper

State Statecable 1/0 192.168.136.1/24 Up IS

show cable modem phy (remote-query)

The CMTS measurements and individual modem MER will still display on a per modem basis without remote query enabled but there will be no CM measurement data.

MER is calculated per modem basis using the last 5 IUC4 Station maintenance bursts

C4# show cable modem phy Dec 2 11:22:23

Last PollStarted: 2008 December 02 11:22Completed: 2008 December 02 11:22

---- CMTS Measurements ----- --------- CM Measurements ---------USPwr USSNR uReflec Timing USPwr DSPwr DSSNR uReflec Timing Last

Interface (dBmV) (db) (dBc) Offset (dBmV) (dBmV) (db) (dBc) Offset Polled MAC address --------- ------ ------ ------- ------ ------ ------ ------ ------- ------ ------ --------------2/0/0 0.0 38.7 0 1809 43.0 -17.1 30.5 22 11848 00:00 0000.ca30.0a70 (Arris)


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Forward Error Correction (FEC)

FEC T BYTE- FEC Error Correction - The number of bytes that can be corrected per FEC code

word. For DOCSIS 1.0 and DOCSIS 1.1 mode, valid values are from 0 to 10 (decimal), where 0 means no FEC. For DOCSIS 2.0 A-TDMA mode, the valid values are from 0 to 16 (decimal), where 0 means no FEC.

FEC K BYTE- FEC Codeword Len - Size (in bytes) of the FEC code word. Valid values are from

16 to 253. Note: the following must be met:

(FECCodewordLen + 2*FECErrorCorrection)

Ingress Cancellation (ICB)

The 2Dx12U Ingress Cancellation feature provides administrative control over certain proprietary capabilities of the Broadcom BCM3140 dual channel burst receiver. The BCM3140 has an ingress cancellation block that analyzes the noise environment of an upstream channel. It then suppresses narrow-band ingress or adjacent-channel interference. Analysis only occurs during unused burst intervals.

The ingress-cancellation interval:- Determines how often a grant is given specifically for ingress cancellation. The units of this parameter are

in milliseconds. Consequently, the default value of 100 means a grant is provided every 100 msec. Note, the grant is a unicast grant to a SID that is reserved specifically for ICB (0x1ffe). A value of 0 disables ICB.

The ingress-cancellation size:- Refers to the size of the grant that is given for ingress cancellation. The units of this parameter is in terms

of mini-slots. The grant for ingress cancellation must contain enough mini-slots to transfer 256 symbols plus one additional mini-slot for ingress cancellation to work properly. We recommend a default value of 0 which basically means that the software will automatically calculate this based upon the upstream parameters. Otherwise a value that is too small will cause ICB to not work properly and a value that is too large will waste upstream bandwidth.

- With a typical upstream configuration and using the default ICB parameters, this is typically a couple percent of the upstream bandwidth.

Configuring Ingress Cancellation (ICB)configure interface cable 1/0 cable upstream 0 ingress-cancellation interval 100 configure interface cable 1/0 cable upstream 0 ingress-cancellation size 0


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Pre-Equalization

Adaptive equalization (Pre-Equalization): Counters the affects of linear distortions: These impairments cause the Upstream burst at the input to the CMTS to be tilted/distorted.

Pre-Equalization will Pre distort the modems US burst so it arrives at the CMTS flat and undistorted

Enabled on a per US basis

To enabled/disable Pre-EQ:configure interface cable / cable upstream pre-eq-enable

NOTE: 1.0 modems do not support Pre-EQ , most should ignore equalization when its enabled but some have been known to drop offline. If there are 1.0 modems on the network, enabled in a maintenance window and verify modem counts.


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DOCSIS Ping

Supported by Software Releases 5.1.x and higher Great for troubleshooting modem and plant issues

This feature provides CMTS administrators with a method of detecting intermittent plant issues by pinging a given modem at the DOCSIS layer. It causes the C4 CMTS to schedule several station maintenance opportunities and record the results. These results can be used to isolate issues between the CMTS and upstream channels, nodes, or cable modems.

C4# ping docsis 0000.ca31.7352 10 verbose Providing 10 DOCSIS station maintenance opportunities, timeout is 1 sec:! Reply from 0000.ca31.7352 (Arris) tadj= -1 padj= 0.0 fadj= 0 response=successa Reply from 0000.ca31.7352 (Arris) tadj= 2 padj= 0.0 fadj= 0 response=success! Reply from 0000.ca31.7352 (Arris) tadj= -1 padj= 0.0 fadj= 0 response=success

The command that follows is an example of DOCSIS ping in default (brief) mode with a count of 50:

C4# ping docsis 10.135.232.254 50Providing 50 DOCSIS station maintenance opportunities, timeout is 1 sec:fffa!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Success rate is 94 percent (47/50)

- The characters displayed in the system response define the results of the range request received from each station maintenance opportunity.


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DOCSIS Ping (cont)

The meaning of each character is as follows:

! The range request received required no adjustments.a The range request received required a timing adjustment greater

than 1/64th of a DOCSIS tick (6.25 microseconds), or a power adjustment greater than 0.25dB, or a frequency adjustment greater than 0 Hz, and the ranging response indicates success.

A The range request received required a timing adjustment greater than 1/64th of a DOCSIS tick, or a power adjustment greater than 0.25dB, or a frequency adjustment greater than 0Hz, and the ranging response indicates continue.

. There was no range request received from a station maintenance opportunity.

f Failure: the CM is offline.

When determining the success rate, ! and a are counted as successes and A, . and f are counted as failures.


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show cable flap-list

The flap types are:- Ranging Flap if the previous state is Ranging or RangingAborted- Provisioning Flap if the previous state is RangingComplete, IPComplete or AccessDenied- Registration Flap if the previous state is RegistrationComplete- By default the show cable flap-list will output all modems with non-zero flap counts by CM MAC

address. The sort-flap and sort-time are alternative sorting methods.- Another command which includes flaplist data is the show cable modem summary. This

command displays the per-channel flap counts.C4# show cable flap-list cable 13 Nov 18 18:24:51

Pre-Flap Time Since Latest ( Flaps ) Interface State State Last Flap Uptime SM Rsp % PowerAdj Range Prov Reg MAC address--------- ---------- ---------- ----------- ----------- ----------- -------- ----- ----- ----- -----------13/0/0 Offline Ranging 0:01:26 0:00:40 92.0851 3006 647 0 7 xxxx.xxxx.xxxx (Vendor_X)13/0/0 Offline Ranging 0:00:52 0:00:39 74.3699 4313 8986 0 0 xxxx.xxxx.xxxx (Vendor_X)13/0/0 Registered Registered 24:55:57 20:58:32 99.5135 0 0 6 58 xxxx.xxxx.xxxx (Vendor_X)13/0/0 Registered Registered 27:19:02 27:19:02 98.0988 43 2 1 2 0015.a2ba.177c (Arris) 13/0/0 Registered Registered 6:20:44 6:20:44 99.5334 19 0 0 3 0015.a303.9003 (Arris)13/0/0 Registered Registered 130:43:51 130:41:31 99.6997 0 0 0 3 0015.a3e1.6d96 (Arris) 13/0/0 Registered Registered 15:34:26 15:34:26 99.3821 0 0 0 1 0015.ce4c.0cee (Arris)

C4# configure cable flap-list power-adjust threshold ? - The threshold (int TenthdB) used to monitor the power adjust in the flap list.

Default value is 3dBC4# show running-config full verbose | include power-adjustconfigure cable flap-list power-adjust threshold 30


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C4# show cable flap-list ? cm-mac - Filter on CM MAC address cm-ip - Filter on CM IP address vendor - Filter on CM vendor namestate - Filter on CM statecable - Filter on CAM interface identifierupstream - Filter on upstream identifiercpe-mac - Filter on MAC address of CPE under CM cpe-ip - Filter on IP address of CPE under CM max-lines - Maximum number of CMs to display sort-flap - Sort CMs by decreasing flap count sort-time - Sort CMs by increasing latest flap time min-fcount - Filter on minimum flap count max-ftime - Filter on maximum latest flap time (in minutes) H.H.H - Filter on CM MAC addressA.B.C.D - Filter on CM IP addressslot - Filter on CAM interface identifierregistered - Filter on registered CMs unregistered - Filter on all but registered CMs count - Display only CM count totals lchan - Filter on logical channel number min-error - Filter on minimum combined CRC and HCS error count offline - Filter on offline CMs | - Output modifiers


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Another command which makes use of flaplist information is the show cable modem offline command. This command displays only modems which are currently offline.

C4# show cable modem offline Dec 3 14:09:39

Offline Last Previous Timing Rx Interface Time UpTime State Offset Power MAC address --------- ----------- ----------- ---------- ------ ----- --------------2/0/0 0:00:08 0:01:16 IPcomplete 0 0.3 0000.ca31.7676 (Arris) 2/0/0 0:01:25 0:01:18 IPcomplete 0 0.3 0000.ca44.fc65 (Arris) 2/0/0 0:02:13 0:01:15 IPcomplete 0 0.2 0000.cac3.28d2 (Arris) 2/0/0 0:01:13 0:01:16 IPcomplete 0 0.0 0011.e3dc.b997 (RCA/Thomson)

Total Offline Ranging RgAbort Ranged IPcompl BpiInit Online Denied-----------------------------------------------------------------------------------Found 4 4 0 0 0 0 0 0 0

Also note that the Interface, US, Timing Offset, and Rx Power are based on the last communication with the cable modem.


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Ranging Flap: - A Ranging Flap indicates the cable modem did not successfully complete the

Initial Ranging process before flapping. A Ranging Flap means the CM Status did not successfully reach ranging complete before the flap was detected.

- Last Up Time - A very small value (1-2 seconds) may indicate the cable modem did not receive the RNG-RSP message. A more typical value (15-20 seconds) may indicate a ranging adjustment problem.

- The upstream receive power level. See debugging tips below. Some potential causes for a Ranging flaps are: Too much or too little attenuation Interference Amplifier degradation Poor upstream or downstream connections Downstream sync loss Thermal sensitivity Mis-configured RF paths

Provisioning Flap:- A Provisioning Flap indicates the cable modem did successfully range but flapped

before successfully registering


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Registered Flap:- A Registered Flap indicates the cable modem has flapped after successfully

reaching registration complete.

Key information:- Current state of the modem, whether the modem is still offline or has re-

registered.- If the modem is offline, then the LastUpTime indicates how long the cable modem

was online (registered) before the flap.

Some potential causes for a Registered flap are:- Subscriber reset or powered modem off- Modem went out of ranging success threshold(s) (see Ranging Flap causes)- Downstream signal quality problems- Overloaded bandwidth problems- Failure to complete BPI setup- Failure to complete MTA provisioning


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RF Troubleshooting

Nodes with customer complaints and/or connectivity issues should be investigated by first checking the channel MER and FEC counts.

- Helpful commands to debug: show cable noise show cable modem summary show cable modem phy show cable modem detail show cable modem errors show cable modem errors min-error 5 show interface cable x/y show cable flap-list

- The magnitude of the problem can be verified by pinging a few modems on the problem nodes to see if some or all packets are being dropped. The noise level may be bad enough to stop data from flowing but not bad enough to cause the modem to flap, this can happen when running 16QAM or higher modulations. This is due to the fact the station maintenance burst always uses QPSK, which is the most robust modulation type in the presence of noise.


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RF Troubleshooting

Evaluate SNR and FEC errors Utilize the ARRIS ICO or ASA to monitor upstream for noise issues Spare the CAM over to verify CAM is/is not the issue Change the US frequency to another part of the spectrum to see if there is an in-

band noise Reduce the US channel width Change the modulation profile to a more robust modulation type (QPSK for

example) to help reduce packet errors while troubleshooting noise problems Increase the configured US RX power level to increase SNR Move RF plant to another connector on the CAM PIC and see if the issue

follows The upstream cable can be disconnected and reconnected; this may help noise

issues by resolving a poor coax connection Connect a six foot plant to the upstream in the headend with a few modems and

see if noise is still present Swap out the CAM PIC (inspect backplane and PIC connectors for damage

before adding new PIC)


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C4 Preventive CMTS Maintenance

Basic C4 CMTS preventive maintenance to prevent noise issues:- Verify ALL unused F connectors are terminated with 75

ohm terminators (especially front panel DS test ports)- Make sure all front and rear cards/PICs are seated

properly- Verify chassis is well grounded- Keep RF cables properly dressed and tight- Keep all RF noise sources away from C4 CMTS chassis


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Intelligent Channel Optimizer (ICO)

HFC & DOCSIS Performance Diagnostic Tool- Non-Service Impacting Real-time HFC Spectrum Analysis on All Active C4 DOCSIS Upstreams- Assists in Isolating Impairments of the HFC or Service Per Upstream Port- Trouble Shooting Tool to Improve Mean Time to Diagnose/Repair (MTTD / MTTR)- Provides Remote Visibility & Real-Time Measures of Noise Margin & Impairments

C4 Configuration Optimizer Tool- Assess affects of Actual or Current Noise Conditions (AWGN, Ingress, & Impulse Noise)- Examines and Suggests C4 Configuration Enhancements to Optimize Network Performance - Simulates C4 Configuration Enhancements Without Placing Changes In-Service- Enables the Operator to Select a CMTS Configuration to Immediately Improve Network Performance

(perhaps delaying or avoiding truck rolls to Re-establish Service Performance)

Performance Modeling & Planning Tool- Aids in Modeling & Planning for the use of Very High Order Modulation (QAM) Schemes, Channel Modes

(A-TDMA, S-CDMA, etc), Channel Width, & Frequency Selection - Provides Assurance that Spectrum is Fully Optimized with Minimal Risk to Operations & Services- Models affects of Hypothetical Noise Conditions (AWGN, Ingress, & Impulse Noise) on Network & Service

Performance- Based on Hypothetical Noise Conditions, Channel Modulation, Mode, Width, and Frequency Determine

the Optimized C4 Configuration Settings


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Runs on any Windows XP Computer Communicates with C4 CMTS via SNMP, Telnet or

Ssh Taps FFT Spectrum Analyzer on any Upstream

Receiver Analyzes Upstream Noise (AWGN, Ingress or

Impulse) Predicts Packet Error Rate (PER) Performance Suggests ways to Increase Data Rate Provides optimized modulation profiles Gives the engineer the ability to see the US In-Channel

noise floor characteristics


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081204 VUG C4 RF Troubleshooting