Hello,
I'm used to measuring the network quality by it's SNR or SNR Equalized values, this is not my field but I learned a lot along the years.
I have a SNR upstream of 33 a Equalized of 36 Micro reflections = 35
quantity of errors vs no errors or corrected seems ok
channel freq. 39000000 Hz
channel modulation = tdma
channel width = 3200000 Hz
Modulation Profile: 26 SNR: 16.4dB PM Capable: no
IUC name req init stat sht1 lng1
IUC ID iuc1 iuc3 iuc4 iuc5 iuc6
Modulation qpsk qpsk qpsk qam16 qam16
ChannelMode tdma tdma tdma tdma tdma
PreambleSize 32 320 320 64 128
DiffEncoding no no no no no
FEC T 0 10 10 10 10
FEC K 16 34 34 78 78
ScramblerSeed 152 152 152 152 152
MaxBurst 0 0 0 8 0
GuardTime 16 16 16 16 30
LastFEC short no no no yes yes
Scrambler yes yes yes yes yes
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This is the profile modulation I'm using in a terayon CMTS 3200 but one of the upstreams with this modulation
has cable modems having trouble registering (Thomson) only by what was transmited to me since I'm not at that location
checking the CM's , they say they are slow at initial registering after the CM is reset.
The Downstream freq. is 415Mhz QAM 256 interleave of 32
Upstream Channel ID : 3
Upstream Channel Type : tdma
Modulation Profile : 26
Modulation Parameters : IUC 5 =qm16, TCM =n/a, RS(T =10, K =78)
Modulation Parameters : IUC 6 =qm16, TCM =n/a, RS(T =10, K =78), MAXB=255
Modulation Parameters : SNR Threshold - 16.4dB
Upstream Frequency : 39000000 Hz
Upstream Channel Width : 3200000 Hz
Minislot size : 2 ticks
Minislot Capacity : 32 symbols
Ranging Backoff Start : 3
Ranging Backoff End : 4
Data Backoff Start : 7
Data Backoff End : 8
Nominal Receive Power : 0 dBmV
Fragmentation : Enabled (Piggyback)
Minimum fragment length : 48 bytes
Concatenation : Enabled
Initial Ranging Interval : 100 msec
Periodic Ranging Interval : 29000 msec
Round Trip Delay : 1600 usec
Pre-Equalization : Enabled
Impulse Detection (IMD) : Disabled
Erasure Percentage : 0.00%
Erasure Count Time Period : 10
DataPacket Errors : 4064518
Power Management : Disabled
Includes Contention : no
Unerrored Codewords : 1139769415
Corrected Codewords : 2573926
Uncorrectable Codewords : 289070
SNR : 32 dB
SNR Equalized : 37 dB
Microreflections : 36 dBc
Total CM = 53
Any idea on what can be the issue here?
Sounds like RF issue, have you hooked up a spectrum analyzer to the return to see whats coming back in the 5-50mhz band?
That's what I thought problem is that I'm not in that location... I'll ask someone to do that for me.
Thanks.
Hi!
Are you sure the downstream is good in that area? The upstream seems quite OK, perhaps a little too many corrected CWs, but as long as uncorrectables aren't more than your 0.025 % I'd say quality is good.
Take a look at the modems SNR on the received downstream signal. If that SNR is good in other areas, but not in this area, you have a downstream problem.
You can always try to lower the modulation on the upstream to QPSK to see what happens. Modems that are online shouldn't go offline but continue to provide service without interruption.
/Fredrik
Actually, now that I look at this again, I notice your downstream frequency is 39mhz. What are your return diplexers in your amps? If you are running a 40mhz return, you could be degrading with rolloff .6mhz of that channel. Now, that may not seem like much, but digital carriers HATE rolloff. Its definately enough to cause those modems some trouble registering. You need to back away from the edge, or replace all your 40mhz diplexers with 42mhz diplexers.
If neither case is feasible, then you need to go back to a 1.6mhz channel until you can do one or the other.