802.11n Speed Drop

derekoharrow

Standard Member
I am having intermittent problems with my home WiFi network which is badly affecting my video playback.

Firstly, here's my setup.

My "server" is my old HTPC - a dual core with 4GB of RAM running Windows 7 Pro. This uses a D-Link DWA-140 USB 802.11n WiFi adapter, with latest drivers. It is sharing media to my HTPC just as a network share (i.e. not streaming).

My "htpc" is a Revo R3600L, 2GB RAM, running Windows 7 Home Premium. This also has a D-Link DWA-140 USB WiFi adapter, with latest drivers. I use ZoomPlayer to access and play the files from my server.

My router is a D-Link DIR-615 with firmware v4.11. Both PC's connect fine and are, normally, connecting at 270mbps (I've set both PC's to use AES to ensure this happens).

The problem is that sometimes, for no known reason, the speed of the wireless network drops - sometimes to as low as 13mbps - at which point video playback becomes at best stuttered, but generally stops or hangs altogether.

I've tried everything I can think of to work around this, including setting the Wireless Channel to one that doesn't seem to be used by any of the neighbours.

Anyone got any ideas how I can fix this?

As an aside I also have a WD TV Live + D-Link DWA-140 and this never seems to stutter or hang - perhaps it's more resilient to network problems?

Thanks
 

t72bogie

Novice Member
its tricky to troubleshoot wireless interference without proper tools i.e. a spectrum analyser so you can see the airwaves in the frequency band etc...freebie software tools like INSSIDER can help see neighboring access points, but not RF interference from non 802.11 sources...

it could be anything thats interfering momentarily....even down to someone driving past in a car with some non supressed electrical components :(

it really can be random and out of your control if the source is not coming from anything in your house

anyway, to start with try looking for any obvious sources of interference around the home, that can be springing up from time to time ...

the list is endless, but common things are wireless devices like baby monitors, phones, video senders, some transformers

a few weeks back I was at the inlaws who were complaining of unstable wireless, just started a few weeks back - they were looking at getting a new router as it was a few years old ....the wireless was up an down like a yo-yo ...funnily enough in the warm weather, so it was overheating....right? ....

...no...it was those bloody electric ceiling fans that they had in the rooms where the router and laptop were - must have been making some weird electrical field with the spinning motor etc as when they were switched off, it was rock solid....switch on (in warm weather) and the wireless played up again

anyway, just an example of how jumping to conclusions could send you off on a tangent with your troubleshooting.....
 

beerhunter

Novice Member
The problem is that sometimes, for no known reason, the speed of the wireless network drops - sometimes to as low as 13mbps - at which point video playback becomes at best stuttered, but generally stops or hangs altogether.

I've tried everything I can think of to work around this, including setting the Wireless Channel to one that doesn't seem to be used by any of the neighbours
I could still be a neighbour's network. Did you use inSSIDer to help you to choose the WiFi channel or just take a stab in the dark. If the latter, then try using inSSIDer. BTW you may need to do that just as the connection rate drops.
 

mickevh

Distinguished Member
As an aside I also have a WD TV Live + D-Link DWA-140 and this never seems to stutter or hang - perhaps it's more resilient to network problems?
Perhaps WD TV has bigger buffers in it...?

Are you aware that with wifi protocols, "only one device can transmit" at a time. Looking at your description you have 4 devices competing for the airwaves - do you have anything else, (phones, blackberries, laptops, etc.)

I notice you have your server connected wifi. That means on a journey from source to sink, a lump of streamed media (or anything else) has to transit server-to-AP thence the AP must wait for the airwaves to go quiet before transitting AP-to-htpc. These transmission cannot happen concurrently and thus your useful throughput is halved (at least) compared to the nominal "link rate" your devices report, before we even contemplate playing nice with any other wifi devices.

If you tried to stream from server to both WD TV & htpc at the same time the throughput would half again.

If possible, I'd prefer to have servers connected wired leaving more wifi bandwidth available for the "last hop" from the "infrstructure" (cabled) network to mobile devices. For media streaming, I'd prefer not to have the sink device wifi either if I wanted reliable and fast streaming.

Cheers, M.
 
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derekoharrow

Standard Member
Thanks, that's a very good point. I'd prefer not to use LAN cables (or rather my wife would prefer me not to use LAN cables).

I tend not to have video going to more than one device at a time - it's either downstairs on the HTPC, or upstairs on the WD TV Live.

A lot of the time it's fine, but it does tend to drop in the evening, so I'm wondering if it is interference from a neighbour.

If it keeps up I may have to revert to physical cables - unless anyone know's if powerline is good now (I used to use it, but not for heavy video transfer).

Perhaps WD TV has bigger buffers in it...?

Are you aware that with wifi protocols, "only one device can transmit" at a time. Looking at your description you have 4 devices competing for the airwaves - do you have anything else, (phones, blackberries, laptops, etc.)
 

derekoharrow

Standard Member
I used the RAlink utility to show which other networks were visible. I'll give inSSIDer a try though - thanks!

I could still be a neighbour's network. Did you use inSSIDer to help you to choose the WiFi channel or just take a stab in the dark. If the latter, then try using inSSIDer. BTW you may need to do that just as the connection rate drops.
 

t72bogie

Novice Member
200Mbps powerline is pretty good, 500Mbps is on the way

200Mbps will give you average of 50-60Mbps in the real world in 90% of use cases

its another shared medium, but you do have more control over whats plugged in and generating background noise....unlike the airwaves

still not as good as a dedicated cable.....
 

mickevh

Distinguished Member
WMP (V11 on my machine) has an option to increase how much data it buffers before playback starts. "Tools, Options, Performance, Network Buffering." Not sure where on Win7, but I think it's similar.

However that's only going to "smooth out the bumps" as it were, if the infrastructure fundamentally cannot sustain the average rate of delivery required, it'll still glitch. The downside is that having configured your player to buffer X seconds worth of data, it takes "X" seconds before playback starts whenever you open a file which some people can't put up with.

Still, if you're using WMP as your renderer, it'll cost nothing to experiment with it.
 

derekoharrow

Standard Member
WMP (V11 on my machine) has an option to increase how much data it buffers before playback starts. "Tools, Options, Performance, Network Buffering." Not sure where on Win7, but I think it's similar.
I think that only applies to streamed video whereas my setup is using SMB/CIFS and network file sharing, so WMP buffering won't apply I don't think.

Thanks for trying to help though.
 

derekoharrow

Standard Member
200Mbps powerline is pretty good, 500Mbps is on the way
I've just looked and it seems that Gigabit powerline is already here from Belkin. OK, you won't ever actually get the full 1000Mbps, but it should deliver 802.11n top speeds without the risk of drop-outs and interference. If the problems keep up I may well give this a go.

Thanks
 

t72bogie

Novice Member
I've just looked and it seems that Gigabit powerline is already here from Belkin. OK, you won't ever actually get the full 1000Mbps, but it should deliver 802.11n top speeds without the risk of drop-outs and interference. If the problems keep up I may well give this a go.

Thanks
its not industry standard...read the reviews on the Belquim stuff - its mostly marketing and not much faster than the 200Mbps ...the real, standards based chips are not due out until later this year ...the "gigabit" only refers to the ethernet port ..not the speed between the powerline modems across the ring main :thumbsdow
 

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