usb lte conflict with 802.11n (300mbps) wifi

What steps will reproduce the problem?
1. install 1.9.2.7 rtn r5450 firmware on wl500w router
2. connect and configure 4g lte usb dongle as wan connection
3. configure wireless for 802.11n 

What is the expected output? What do you see instead?
802.11n capable client connected through wifi should come close to the 
40-50mbps speeds the lte modem connects with, as these speeds are in fact 
attainable when wiring the same client to the lan ports on the router.
instead, speeds cap out 15-20mbps.  

What version of the product are you using?
WL500W-1.9.2.7-rtn-r5450.trx

additional details:
the lte stick used is an alcatel onetouch l100 (vid:0x1bbb,pid:0x011e). it's 
handled by the qmi driver. it works.

i have verified that:

1) the lte modem does in fact provide speeds fof 40+ mbps, by connecting the 
client through wire to the lan port of the router. (this is the same speed the 
stick delivers when plugged directly into the win7 client - so that's nice.)

2) the wifi is in fact capable of (at least) 30-40mbps, by hooking the router 
into a (not so fast) lan (hence the speed cap) through wiring the wan port 
instead of connecting with the stick, and connecting the client through wifi.  

so while independently both connections, the lte wan, and the 802.11n wi-fi 
"deliver" expected speeds, when used together performance degrades 
significantly.

my guesses: wifi being capped back to g-mode speeds when lte usb stick 
connects, or (hopefully not) actual physical radio interference between the 
wifi and the stick.

Original issue reported on code.google.com by kolij...@gmail.com on 22 Dec 2014 at 1:29

zhuravskiy / wl500g

usb lte conflict with 802.11n (300mbps) wifi #460