[LINK] 500-Mbits/s over copper

[Tom Koltai]

Thank-you Paul,
 
You filled in a coulle of gaps in my knowledge base.
Although I am pretty sure that eftel, iinet and a couple of others in
sydney are using vdsl-2. but I could be wrong.
My reference is Zyxel hardware sales. (i.e.:
http://www.zyxel.com/web/product_family_detail.php?PC1indexflag=20040812
093058
<http://www.zyxel.com/web/product_family_detail.php?PC1indexflag=2004081
2093058&display=6239&CategoryGroupNo=4B84BD2B-12CA-4A20-9247-3A214B94B57
8> &display=6239&CategoryGroupNo=4B84BD2B-12CA-4A20-9247-3A214B94B578)
 
Regards,
 
tom
 
 
 

-----Original Message-----
From: Paul Brooks [mailto:pbrooks-link at layer10.com.au] 
Sent: Thursday, 19 March 2009 1:33 PM
To: Tom Koltai
Cc: link at anu.edu.au
Subject: Re: [LINK] 500-Mbits/s over copper


Tom Koltai wrote:


<snip>



The problem for Australia is that each Residence has two pairs only, and

the average home is further than 500 metres from the exchange.



  

<snip>


There are four ISP's utilising this technology in Australia, however

only one so far has offered phone combined (EFTEL) - which would be

necessary to take advantage of the pair bonding Ericsson implementation.

  

I think you are confusing bonded VDSL2 with bonded SHDSL Tom.

Several ISPs are using bonded SHDSL (one vendor Hatteras, others are
available) to achieve relatively high bandwidth symmetric links over
distances of a kilometre or two. SHDSL (whether bonded or not) uses the
low frequency spectrum and prevents a simultaneous baseband telephone
service from operating. If EFTel are providing a combined phone service,
its probably using VoIP within the broadband channel, which the others
could presumably also do - and it has nothing to do with pair-bonding.

None of this has anything to do with the Ericsson announcement, which is
pair-bonded *VDSL2*, and more importantly is a demonstration of
vectorisation, which is a fancy word for interference cancellation
similar to the MIMO techniques used in modern radio networks. This has
the potential to vastly improve even single-pair VDSL2 services (and
even ADSL services as well).
Today's ADSL/VDSL technology works through interference avoidance -
active interference cancellation aka vectorisation has been a hot
research topic for a few years, and its good to see it start to emerge
from the labs.



The result at 12-15mhz would be between 10 and 20 mbits per subscriber

(using bonded pairs = 4 copper wires) at no more than 1.5 kilometres

from the exchange. Therefore the NBN cabinet rollout would be an

imperitive if we want the majority of Australians to have over 50 mbit

to the home.

  

Not really. Even with an NBN cabinet rollout, your very first sentence
still applies - most residences have only one or two pairs from the
piller into the residence. The Ericsson demonstration used six pairs
bonded together - for this 500Mbps speed to be available for widespread
residential use, you would still have to run more physical copper
drop-cables to each house so that every one of them had many pairs to
bond together - and if you're going to do that, you'd be better off
making at least one of those pairs of glass rather than copper.

Yes, this demonstration  indicates that the two pairs into each house
might be bonded together to form a double-bandwidth VDSL2 service - but
then, line bonding was built into the ADSL2 and 2+ spec as well, and we
don't see any bonded-ADSL2+ services in the commercial marketplace today
- three-pair-bonded-ADSL2+ could achieve 50 Mbps+ today if the software
in the DSLAM and a suitable CPE supported it.


Cheers,
    Paul.




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