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428 posts

Ultimate Geek
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Topic # 60373 25-Apr-2010 23:26
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Well, Chorus has started work on the cabinet in our street (about 300m from the house!), so I've pulled the pin on Orcon and changed to Telecom.  (I'd had enough of slow international speeds in the evenings and during school holidays.)  I expected the line speed to drop, and sure enough, it's now about 4500 Kbps compared to 7500 with Orcon.

Is this simply due to the higher SNR that Telecom run compared to Orcon?  (12dB / 8dB respectively)  I note that the actual rate and the attainable rate are now the same, whereas with Orcon, the attainable rate was always higher.  Or does it also reflect equipment differences in the exchange?

Just curious, as we should get much higher speeds with a cabinet just up the road.




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  Reply # 322851 26-Apr-2010 00:06
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You'll still probably be connected to the exchange for awhile. If they have just started work on the cabinet it won't be fully active, tested and all the lines migrated for a few months.

To answer your other question yes for the same distance (to the exchange) Orcon's noise margin of 6dB will give you higher sync speed than Telecom's 12dB. Apparently Telecom choose to use 12dB by default for stability as there is a lot of old dodgy wiring around in NZ.





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  Reply # 322852 26-Apr-2010 00:07
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Also Signal to Noise Ratio is not the same thing as Noise Margin

Signal to Noise Ratio (SNR)
This is the ratio between clean / clear (good) signal to background Noise (Bad)

Noise Margin (NM)
This is a buffer that allows for stability

 
 
 
 




428 posts

Ultimate Geek
+1 received by user: 2


  Reply # 322895 26-Apr-2010 09:42
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Yes, it is noise margin.  It's called "SNR margin" in the old router, clearly an attempt to confuse!

The cabinet is due to be in service in June.  The Chorus website shows about 10 cabinets due for completion in the next couple of months for our exchange (Onehunga).




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