Does an AP behind a wireless bridge necessarily incur a speed penalty?
November 30, 2011 8:52 PM   Subscribe

I've been trying to setup a wifi network behind a wireless bridge, and keep finding that internet speeds are 1/3 to 1/10 of those I get by when connecting directly to the bridge or source network. What gives?

My landlord has provided a wirelessly shared 20Mbs DSL connection for the tenants of a small property. He's (wisely) located the (802.11g) wireless router centrally, but I get spotty coverage throughout my apartment, especially on handheld devices, so I've been trying to figure out a way to boost the signal - and also establish a secure 'walled garden' for my devices to talk to each other on that's inaccessible by my neighbors.

To that end, I've acquired a bunch of routers, including a Linksys E3000, Asus RT-N10+, Asus WL-330Ge, and D-Link DIR-655, all but the last of which support various alternative firmwares.

When a router is configured in client or bridge mode and has a good signal, I can get 10Mbs speedtest results from a laptop wired to it - same as I get from my desktop that's connecting to the landlord's SSID. But when I plug in a device to serve as an AP, I can't get anything near that speed on internet transfers, just 1-3Mbs.

What's especially confounding here is that wireless file transfers from the bridge+AP (the E3000 has a USB port) are zippy, at ~20Mbs. It's just the relayed internet that's problematic.

Landlord AP is on channel one; I've put mine on 6 or 11. I thought this would mitigate the bandwidth halving of repeating?
posted by unmake to Computers & Internet (5 answers total) 2 users marked this as a favorite
Are you using the 2nd AP that's plugged into the client bridge as a router? Make sure its setup on a different subnet than the landlords AP and that its DHCP server is handing out IP addresses in the appropriate range.
posted by jmsta at 3:40 AM on December 1, 2011

Are you using two wireless boxes on your side (one in client mode to talk to the landlord's AP, one in router+AP mode to talk to your local clients) or are you trying to do the whole thing with a single WAP in repeater mode? I'd expect the two-boxes setup to work better. A single box in repeater mode is going to need to do a lot of channel switching and associated handshaking to flip between your clients and the landlord's WAP, all of which is going to need to happen on every single packet transferred.

Also, if you've got a good upstream ADSL2 connection you don't have a heap of bandwidth to spare over 802.11g. You might get much better results by using an 802.11g box in client mode to talk to your landlord, and running your own WLAN over 802.11n on 5GHz; that would also eliminate all interference with the 2.4Ghz 802.11b landlord link.
posted by flabdablet at 5:44 AM on December 1, 2011

Right now I've got the E3000/Tomato mounted in a position where it seems to have a solid connection. Its 2.4Ghz radio is connected to the landlord's AP; its 5Ghz is disabled as I don't presently have any equipment that uses that band.

Landlord IP's are 192.168.0.x; mine are 192.168.1.x.

It's connected by ethernet to the RT-N10+/dd-wrt AP, which is in mixed G/N mode.

[LANDLORD/g/ch1]~~~[E3000/g/ch1]===[RT-N10+/gn/ch11]~~~[wireless clients]

For some reason, even though the RT-N10+ AP is connected to the E3000 bridge by a cable, internet throughput is highly dependent on where the AP is situated (and the orientation of its antenna). By queuing up some downloads I was able to find a spot on the wall where the routers' bandwidth monitors showed a stable 10+mbs, so that's where I stuck it.

I'm still curious why transferring files from the storage attached to the E3000 to wifi clients connected to the AP isn't subject to this placement sensitivity, but my network appears to be sorted for now.
posted by unmake at 12:56 PM on December 1, 2011

Even though they're tuned to different channels, it might be that a strong 2.4GHz-band signal from your nearby RT-N10+ is swamping the E3000's input stage (the inverse square law is a bitch). You might want to experiment with using a directional antenna for the hop to your landlord's AP.
posted by flabdablet at 6:25 PM on December 1, 2011

Interesting, flabdablet.

Advice for future readers in a similar situation:

You'll want to wire a laptop to the client or bridge router and initiate some lengthy downloads that you know will max out your connection. Open that router's admin interface and monitor the bandwidth and signal quality from there; take note if its link speed is changing frequently. Move it around until you find a location with maximal signal quality and bandwidth.

Setup your AP, making sure its IP doesn't conflict with the client/bridge device, to which it should now be wired. Connect to it by wifi, and repeat the downloading/positioning exercise. I found it helps to try different orientations of the router and/or antennas.

My landlord's AP didn't have "AP Isolation" enabled, so it was possible to communicate with my neighbors' devices, and vice-versa (even though they're on a different subnet); it's simple (and probably prudent) to add a line to dd-wrt's firewall to disable this.
posted by unmake at 7:53 PM on December 3, 2011

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