WiMAX + WiFi = slow?

[DulacLancelot]

i have the Sprint Xohm home modem.
i also have 2 wireless routers.
i've been using SpeedTest.net to test my internet speeds.

connecting the modem directly to my computer results in speeds around 8Mbps/1.4Mbps (down/up). routing that connection through one or both of my routers via ethernet cables results in the same speed results. however, if i connect to the routers wirelessly at any stage, the speed cuts down to 3/1.4Mbps.

i've heard Xohm is Wimax at around 2.5GHz. one of the routers is capable of 802.11a (5.5ish GHz), but even with that Wireless A connection, the speed is still slow.

there is certainly a lot of other wifi networks in the area, so i tried to measure the capacity of the wifi connection itself. i downloaded some point-to-point network performance measuring software (pcattcp.exe). a wired connection through my router LAN between my laptop and my desktop showed throughput at 88Mbps. when i used my laptop's wifi connection instead that dropped to about 20Mbps, but still plenty to handle my internet connection without slowing it down i would think.

i brought one of my WiFi routers over to a 10Mbps non-WiMAX internet connection. the speed tested to be 10Mbps wired. and it tested to be 10Mbps over WiFi, too.

i have the modem on the second floor, and have brought the connection through wires down to the first floor so as to keep the wireless routers far away from the modem but this did not have any effect.

someone else seems to have noticed this as well:
dslreports.com/comment/3365/72014
(search for "Speeds for wireless" on that page)
his comments say the wifi link about halves the internet connection speed. for me it seems more like it caps it at around 3Mbps. the upload speed, which never breaks 3Mbps over wire, is unaffected over WiFi. also, if i move the modem such that the wired download speed is less than 3Mbps, the WiFi connection does not cause any further slowdown.

any ideas on why the slowdown?

[grndslm]

You have a crap router.

EDIT: Nevermind, I read it all the way, and I dunno. Sounds odd, alright.

[ericp]

I also noticed weird interactions between the Xohm routers and wireless routers. Moving the two 10 feet apart helped, even when the WiFi router was set to 5ghz, worked for me.

[DulacLancelot]

ok, so now i am seeing the same odd 3Mbps speed barrier problem WITHOUT WiFi in the connection path.

so here is the setup:

- XOhm home modem in a room on the second floor, by a window where it gets optimal signal, plugged into a wall ethernet jack
- router in a closet in another room whose WAN port is connected to the XOhm modem through the "walls"
- one of the router's LAN ports is then connected back to an ethernet jack that leads, again though the walls, to yet another room on another floor
- in the final room, there are 2 laptops in proximity to the ethernet jack that is connected through the walls to the router's LAN port
- all the ports and wiring thus far are 100Mbit

in the final room, both compters are sitting there booted up and not connected to anything but ready to go, configured to use DHCP.

----
Computer 1:
2.13GHz Pentium M
2GB RAM
60GB HDD
100Mbit ethernet port
Windows XP

i plug in the network cable, the little message in the bottom right corner says hey-i'm-connected-to-a-LAN, i run the speed test at speedtest.net, i get about 7 or 8 Mbps.
----

----
Computer 2:
3.06GHz Core 2 Duo Extreme
8GB RAM
320GB HDD
Gigabit Ethernet
Windows XP 64-bit

i unplug the cable from Computer 1, immediately plug it into Computer 2, the little message in the bottom right corner says hey-i'm-connected-to-a-LAN, i run the speed test at speedtest.net, i get about 3MBps.
----

i can go back and forth many times, with many reboots, etc., results are totally consistent.

so i take it it was not the WiFi itself that was slowing anything down, but some sort of network setting associated with my WiFi connection that was somehow giving the XOhm internet connection problems. and now, the LAN connection on Computer 2 must be set the same way.

but i don't know what this network setting might be. :( any ideas?

[djinks]

Try the Speedguide TCP optimizer tool (http://www.speedguide.net) on both computers. Select the SG Broadband Tools link from the Shortcuts section on the left. Then download and install the TCP Optimizer tool. It might help you identify any settings differences and sub-optimal settings.

Other than that, I can only suggest you may have a defective network adapter on computer 2. Can you try computer 2 on another highspeed connection?

[Flash129]

I have exactly the same problem,but am not getting the performance you are getting. I usually get between 1 and 4 MB download speeds through my XOHM modem. My wired connection through the WLAN router is approximately the same. However when I connect wirelessly to the router I can't get more than 500 kB. I had dsl previously and did not have this problem. Also, have done all the obvious things (changed channel setting to not interfere with other WLANS, moved WLAN modem away from WiMAX modem, etc.). Has anybody solved this problem??