VDSL Speeds

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ElectronicFerret

122 posts

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# 175625 6-Jul-2015 14:52

This is purely a scholarly or theoretical question, so assume minimum line lengths and perfect attenuation figures.

The Wikipedia article on VDSL2 states that when using the 17a profile on VDSL2, it's capable of connecting at 100Mbit/s.

So, why do people within a stones throw (~50 metres) of their cabinet get the "maximum" speed of 57MBit/s?

Is this due to DLM? Are the Chorus reducing the connect speeds for reliability? Is it something else?

Edit: Does this mean that the DSL reports DSL speed calculator is unreliable as at low (below 9dB) attenuation figures are reported at >58MBit/s

PeterReader

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# 1337900 6-Jul-2015 14:52

Hello... Our robot found some keywords in your post, so here is an automated reply with some important things to note regarding broadband speeds.

If you are posting regarding DSL speeds please check that

- you have reset your modem and router

- your PC (or other PCs in your LAN) is not downloading large files when you are testing

- you are not being throttled by your ISP due to going over the monthly cap

- your tests are always done on an ethernet connection to the router - do not use wireless for testing

- you read this topic and follow the instructions there.

Make sure you provide information for other users to help you. If you have not already done it, please EDIT your post and add this now:

- Your ISP and plan

- Type of connection (ADSL, ADSL2, VDSL)

- Your modem DSL stats (do not worry about posting Speedtest, we need sync rate, attenuation and noise margin)

- Your general location (or street)

- If you are rural or urban

- If you know your connection is to an exchange, cabinet or conklin

- If your connection is to a ULL or wholesale service

- If you have done an isolation test as per the link above

Most of the problems with speed are likely to be related to internal wiring issues. Read this discussion to find out more about this. Your ISP is not intentionally slowing you down today (unless you are on a managed plan). Also if this is the school holidays it's likely you will notice slower than usual speed due to more users online.

A master splitter is required for VDSL2 and in most cases will improve speeds on DSL connections. Regular disconnections can be a monitored alarm or a set top box trying to connect. If there's an alarm connected to your line even if you don't have an alarm contract it may still try to connect so it's worth checking.

I recommend you read these two blog posts:

- Is your premises phone wiring impacting your broadband performance? (very technical)

- Are you receiving a substandard ULL ADSL2+ connection from your ISP?

I am the Geekzone Robot and I am here to help. I am from the Internet. I do not interact. Do not expect other replies from me.

Jase2985

8533 posts

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# 1337911 6-Jul-2015 14:58

its due to the quality of the line, those numbers are theoritical maximums not guaranteed maximums and are subject to enviromental/physical factors.
things like cross talk (interference from other connections) also limits the speed.
also the Signal to noise threshold in NZ is 12dB so that also influences the speed that can be obtained. for example my connection is currently 51/10 with a 12dB SNR. I managed to connect during a power outage at 68/10 with a SNR of 3. the lower the SNR the lower the tolerance before you start getting noise on the line

plus in NZ 17a profiles are limited to 70/10 not 100 as stated in yoru reference