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leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

Pros and cons

This is definitely a logical approach that has much going for it:
Up 12 or 15 homes are wired into a ring with short distance copper pairs. The short distance allows maximizing the performance of VDSL2 but the ring design also means that the top speed of 400Mbps is shared for those homes. Concurrent Internet use means each home is only getting a slice of the pie but it will still be plenty fast.

By sharing a connection for 12 (or 15) homes existing copper pairs are being freed up that can be used for bonding (ADSL2+ and VDSL2 can bond up to 32 pairs). This allows existing copper wires to connect from CO to the CN instead of installing new fiber. Little cost and time to deploy.

Using existing VDSL2 standard components means little development cost and faster speed to a marketable product.

Where it will all break down is at the CN. DSL (all variants) work by transmitting a strong signal over a copper pair to a very sensitive receiver at the other end. The reason this works is because the uplink and downlink frequencies are different and neither the DSLAM nor the DSL CPE are transmitting and receiving at the same frequency.

In order for the DSL Ring idea to work DSL signals need to be retransmitted. This means that the CN will need to receive DSL signals at the same frequencies (from the CO) at which it will forward it into the Ring (to the CPE) and vice versa. If the HGW are active components (retransmitting instead of just passing through) the same problem exists there as well. I'm not sure how realistic it is under real life conditions to avoid the feedback problems (from local transmitter to receiver) this is going to cause.
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raytaylor

join:2009-07-28
kudos:1
said by leibold:

In order for the DSL Ring idea to work DSL signals need to be retransmitted. This means that the CN will need to receive DSL signals at the same frequencies (from the CO) at which it will forward it into the Ring (to the CPE) and vice versa. If the HGW are active components (retransmitting instead of just passing through) the same problem exists there as well. I'm not sure how realistic it is under real life conditions to avoid the feedback problems (from local transmitter to receiver) this is going to cause.

By placing a notch filter on the line, you can allow the voice coming from the exchange to pass through the line while effectivley cutting the line at dsl frequencies. Or you could feed the voice circuits from the exchange by running a PCM encoded system or voip over the top of the DSL signals between the local ring and the exchange backhaul.