anyone hear about echo cancellers on an HDSL T-1 used to carry voice traffic from Meridian PBX to DMS-250 (local loop using HSDL to the customer premise from the end office)? We're trying to figure out why echo is only occuring on T-1s that are HDSL provisioned by the LECs? Two ILECs carrying those T-1s state there's no provision for cancelling echo or adjust T-1 levels.
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HSDL T-1s
- Thread starter dwaings
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Thanks Doc. The trouble is I'm an IXC using NorTel DMS-250s with SPMs and the only customers we have trouble with echo on are usually on customer-ordered loops, and those Loops are for plain jane T-1s for regular voice - and every one of those troubled customers are on a LEC HDSL loop. Usually the customer side demarc is a smartjack - we're picking up the T-1 up on an OC-3 or higher bandwidth. There's nothing we can do with these HDSL loops, and the local carriers are saying there's nothing wrong with their loops (and it works for everyone else!)...spans are totally clean, head-to-head from the demarc to the DMS clean no slips/errors. According to all the documentation I've seen on HDSL spans, there's an echo-can feature provided but none of the LECs (mostly in the SWB lan) seem to know how to provision it. We've exercised pretty much all the options from the NorTel perspective - and it's only the spans with HDSL T-1s affected. That's the quandary - and if anyone has any info about the HDSL provisioning/install/testing at the LEC CO, that's what I'm really hunting for.
Dwain
Dwain
YUCK! I fought with the same thing for months. Some were never fixed until the LEC dropped fiber into the location. We were able to fix a few by having the LEC force the cards to B8ZS/ESF. The default and recommended setting is B8ZS/Unframed for the HDSL's which is "supposed" to pass either SF or ESF between the endpoints. I also know the ESF setting did enable some additional diagnostics capabilities on the HDSL cards as well. Do the cards have an ESF light and if so, is it lit? -CL
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yep, from everything everyone sees...but then again, if the local loop is unframed and the endpoints aren't (unframed), then the local carrier wouldn't exactly admit that either...it bears looking at closer though. I don't think we've been able to say HDSL loop D4/ESF framing issues have arisen yet (we're fairly insistent on ordering loops ESF, so the occassional SF loop would probably slip by--no pun intended).
hehehe...
Trouble's leaving the office, just fine!
B8ZS is DEFINED as ESF, and will just purely stagger as SF. But chances are, your problems are with the echo can settings, and you may need to install cans. (They have to be equipped at both ends, if equipped at all.) How far is the longest run in wire miles? Also affecting echo is the gain. Depending on your equipment, you should be receiving at a -16db or at a 0db point... Any thoughts?
TBerd tests would include:
Echo
C-msg noise
Singing
and Return-loss
John
Trouble's leaving the office, just fine!
B8ZS is DEFINED as ESF, and will just purely stagger as SF. But chances are, your problems are with the echo can settings, and you may need to install cans. (They have to be equipped at both ends, if equipped at all.) How far is the longest run in wire miles? Also affecting echo is the gain. Depending on your equipment, you should be receiving at a -16db or at a 0db point... Any thoughts?
TBerd tests would include:
Echo
C-msg noise
Singing
and Return-loss
John
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- #7
The question is back to the HSDL pair...is there a controllable setting at the CO for echo? I've seen documentation that says there is but it doesn't describe how and the issues with ecans on the IXC network is moot - it doesn't matter if the loops are on DTC/DTCI shelfs with internal or external cans or on SPMs with ecans applied - the echo continues, but only on loops where the "last mile" is HSDL. That's on loops as short as 6 miles and as long as the length of Florida (from demarc to switch).
We personally think the trouble is with the gain on the pair - but since they're usually customer ordered loops, we can't get the customer to do jack about it - and the Bell companies won't test with us head to head to validate the quality of the pair - and testing a T-1 on an OC-3 carrier system usually ends up being a fruitless search for trouble.
I'll let you guys know how things go. Thanks for the input.
We personally think the trouble is with the gain on the pair - but since they're usually customer ordered loops, we can't get the customer to do jack about it - and the Bell companies won't test with us head to head to validate the quality of the pair - and testing a T-1 on an OC-3 carrier system usually ends up being a fruitless search for trouble.
I'll let you guys know how things go. Thanks for the input.
If your in Florida then I am assuming your talking about BellS. If that's the case then Adtran and ADC Pairgain are the only HDSL products they use in which you can call technical support or download the pdf file for the card in the smartjack. The PDF file will contain all options. As far as framing it should always be set to unframed , these cards have options for Auto framing which can lock up the cards in AMI if a certain pattern crosses the network. I don't understand why the ILEC won't run head to head with you, if you request they have no choice, but keep in mind you will be billed for any dispatches. Is your circuit a HCFU? if so you can call the CWINS chronic group, they are usally helpful.
Have SWB check the stats and PM's on HDSL link by logging
in to the HDSL span. Use a laptop and plug into the card.
may have to get in touch with SWB Chronic group to have
their tech instruct the field tech on how to do this.
Running T1 stress tests on an HDSL is kinda fruitless,
since the span is not running esf/b8zs.
in to the HDSL span. Use a laptop and plug into the card.
may have to get in touch with SWB Chronic group to have
their tech instruct the field tech on how to do this.
Running T1 stress tests on an HDSL is kinda fruitless,
since the span is not running esf/b8zs.
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