kchan345:

router: linksys ea4500v1
lede version: 17.01.2 (https://downloads.lede-project.org/releases/17.01.2/targets/kirkwood/generic/lede-17.01.2-kirkwood-linksys-viper-squashfs-factory.bin)

Observation:
1)
wireless client: EA4500 using STA mode on 5ghz radio
wireless AP: linksys wrt1900acv1 using AP mode on 5ghz radio
setup: iperf client <--lan--> EA4500 <--5ghz radio--> wrt1900acv1 <--lan--> iperf server

iperf result:
38 Mbps with EA4500 sirq maxing out at 99%

wireless client: EA4500 using STA mode on 2.4ghz radio
wireless AP: asus rtn12d1 using AP mode on 2.4ghz radio
setup: iperf client <--lan--> EA4500 <--2.4ghz radio--> rtn12d1 <--lan--> iperf server

iperf result:
38 Mbps with EA4500 sirq maxing out at 99%

wireless client: samsung galaxy note 5
wireless AP: EA4500 in AP mode on 5ghz radio
setup: iperf client <--5ghz radio--> EA4500 <--lan--> iperf server

iperf result:
142 Mbps with EA4500 sirq around 58%

wireless client: samsung galaxy note 5
wireless AP: linksyswrt1900acv1
setup iperf client <--5ghz radio-->linksyswrt1900acv1 <--lan--> iperf server

iperf result
~220 Mbps

So the low throughput seems to be a problem specifically with EA4500 (mwl8k driver) using STA mode.