PLT / HomePlug Networking

peckerhead

Sorry to resuscitate an old thread, but it came up in a search...

Since I don't already have any wireless gear, I'm half-thinking of trying out one of those Homeplug kits, to connect a PC & Xbox in the young lad's bedroom upstairs to our wired (BT) 1MB router downstairs. For something like Xbox Live, would it make any appreciable difference whether I got the 14MBPS instead of the 85MBPS kit? The former can be had very cheaply on eBay, and of course I'll need two of them. But I've heard a couple of people say that 14MBPS — or whatever fraction of that you actually get in practice! — isn't fast enough (and indeed that it's a bit of a struggle with standard 54MBPS wireless) ...is that the case?

Also, I presume we'd then be sharing the bandwidth? So if daughter dearest was limewiring away at +100Kb/s downstairs (that's the fastest we get in practice) and yer man went online upstairs, they'd each get about half of that?

bminish

peckerhead wrote:

Also, I presume we'd then be sharing the bandwidth? So if daughter dearest was limewiring away at +100Kb/s downstairs (that's the fastest we get in practice) and yer man went online upstairs, they'd each get about half of that?

I would have thought that even the '14' Mb ones should be easily able to keep up with the the ADSL speeds.
I have never tried homeplug, I like HF radio too much! but I would be interested in hearing how you get on with it if you do decide to go down that route

.brendan

peckerhead

Well, I'm tracking a few 2x85MBPS pairs on eBay. But I'd love if someone could tell me that this would do the job just as well. The guy selling it says it will, but then he would, wouldn't he!

watty

As an engineer I'm very sceptical about "homeplug". It's not true PLT in the traditional sense so does not create as much interference.

HOWEVER. These are running on unshielded cable and can cause interference. You could in theory be offically asked to disconnect it.

Any multidrop shared bus system like WiFi or Home Plug can in Theory only manage slightly less than 1/2 the quoted speed. In practice a good rule of thumb is 1/3rd. As more terminals / users added, the speed can drop faster than linear, i.e. doubling the number of users on WiFi from 3 to 6 could give 1/10th of the 3 users speed, which is about 4Mbps on 54Mbps, so for 6 or 7 users 400kbps is not extraordinary. Note that a "server" with a single SATA can drop even slower with 6 users due to 8ms average head seek (200kbps), which is why a supposedly 10 times slower old array of 5 SCSI discs will outperform giving more than 1Mbps with 5 or 6 users simultaneously streaming.



So 14Mbps = 4.5Mbps typical for one user. If there is noise or longer line it will less. So on higher BB packages it is too slow.

Only buy CE marked ones as a slight insurance that you are getting something working and safe. It MUST be meeting UK / Irish safety standards with an Anglo/Irish 3 pin plug, not a two pin Euro plug.


Running some cheap CAT5 cable is a better deal and can give cheaply 100Mbps full duplex or 1000Mbps full duplex if you have PCs, Server, Switch that supports it.

You would need 300Mbps to 400Mbps WiFi to duplicate 100mbps CAT5 for one user. If you have a 8 port switch and 1Gbps server for video and MP3s with 6 users still connected at 100Mps each doing peer applications and server & Internet, the equivalent WiFi or home plug performance would need to be about 1200Mbps or more.


14Mbps is too slow. Especially if we ever get any BB upgrades.

The technology while clever OFDMA on mains, is over hyped. Performance may degrade a lot if neighbours get it.

Anyone checked what it does to R4 LW or any MW Radio? We have a new station starting on MW. RTE MW/LW regularly switches to sport not on VHF.

bminish

watty wrote:

Anyone checked what it does to R4 LW or any MW Radio? We have a new station starting on MW. RTE MW/LW regularly switches to sport not on VHF.

Home plug occupies 4 Mhz to 21 Mhz. One of the reasons it does not go lower is that extreme powerline noise such as this can get into (and screw up) ADSL modems.
In the access PLT trials in Norway the PLT system got into (Via the mains supply) and had a serious impact upon the operation of another provider's Cable modems

You can see some plots etc for homeplug in the following PDF
http://www.sonic.net/~n6gn/netgear_modem_P1-1.pdf

Notching of the amateur bands is built into Homeplug V1 but can be turned off with Home plug V2 to improve throughput somewhat (guess they could not hit 85 Mbs under perfect lab conditions with the notches in place.. )
The notches are not deep enough to prevent all interference to amater users and of course do nothing to protect the SW broadcast bands.
The notches being software implemented do nothing whatsoever to protect the homeplug equipment from the effects of licensed HF users in the vicinity.


.brendan

cgarvey

Thread split from old one and moved from IoffL > Nets/Comms

watty

So if your broadband is either Metro or UPC/Chorus/NTL or Caseyvision, then this might seriously interfere with your upload. DOCSIS Modems use a 6MHz channel between 5MHz and 60MHz for upstream, typically 10MHz to 21Mhz.

The Sky remote Eye is about 6MHz I think on the coax.