[FS#301] ZBT-WG3526 - WIFI 5Ghz - throughput is very poor

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - camel (camel) 

Attached to Project - LEDE Project
Summary - ZBT-WG3526 - WIFI 5Ghz - throughput is very poor
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - easy to reproduce within 1-2 minute:

1.) install trunk
2.) activate wifi and use 5Ghz on client connection (default config, also the same with different wifi settings)
3.) generate traffic with "iperf" and  you will get low traffic throughput
(server): iperf -s -i 1 -w 6M
(client): iperf -c 192.168.1.19 -i 1 -w 6M -l 2M

on openwrt it shows for this client:
300.0 Mbit/s, 40MHz, MCS 15, Short GI
300.0 Mbit/s, 40MHz, MCS 15, Short GI

on openwrt interface it shows: Channel: 36 (5.180 GHz) | Bitrate: 270 Mbit/s

client to server:
------------------
C:\Users\Camel>iperf -c 192.168.1.1 -i 1 -w 6M -l 2M
------------------------------------------------------------
Client connecting to 192.168.1.1, TCP port 5001
TCP window size: 6.00 MByte
------------------------------------------------------------
[  3] local 192.168.1.196 port 16821 connected with 192.168.1.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 1.0 sec  24.0 MBytes   201 Mbits/sec
[  3]  1.0- 2.0 sec  18.0 MBytes   151 Mbits/sec
[  3]  2.0- 3.0 sec  16.0 MBytes   134 Mbits/sec
[  3]  3.0- 4.0 sec  18.0 MBytes   151 Mbits/sec
[  3]  4.0- 5.0 sec  18.0 MBytes   151 Mbits/sec
[  3]  5.0- 6.0 sec  16.0 MBytes   134 Mbits/sec
[  3]  6.0- 7.0 sec  18.0 MBytes   151 Mbits/sec
[  3]  7.0- 8.0 sec  18.0 MBytes   151 Mbits/sec
[  3]  8.0- 9.0 sec  16.0 MBytes   134 Mbits/sec
[  3]  9.0-10.0 sec  18.0 MBytes   151 Mbits/sec
[  3]  0.0-10.0 sec   180 MBytes   150 Mbits/sec

server to client:
-----------------
root at lede:~# iperf -c 192.168.1.196 -i 1 -w 6M -l 2M
------------------------------------------------------------
Client connecting to 192.168.1.196, TCP port 5001
TCP window size:  320 KByte (WARNING: requested 6.00 MByte)
------------------------------------------------------------
[  3] local 192.168.1.1 port 47600 connected with 192.168.1.196 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 1.0 sec  12.0 MBytes   101 Mbits/sec
[  3]  1.0- 2.0 sec  8.00 MBytes  67.1 Mbits/sec
[  3]  2.0- 3.0 sec  12.0 MBytes   101 Mbits/sec
[  3]  3.0- 4.0 sec  10.0 MBytes  83.9 Mbits/sec
[  3]  4.0- 5.0 sec  10.0 MBytes  83.9 Mbits/sec
[  3]  5.0- 6.0 sec  8.00 MBytes  67.1 Mbits/sec
[  3]  6.0- 7.0 sec  10.0 MBytes  83.9 Mbits/sec
[  3]  7.0- 8.0 sec  10.0 MBytes  83.9 Mbits/sec
[  3]  8.0- 9.0 sec  10.0 MBytes  83.9 Mbits/sec
[  3]  9.0-10.0 sec  10.0 MBytes  83.9 Mbits/sec
[  3]  0.0-10.2 sec   100 MBytes  82.6 Mbits/sec

System
Hostname	lede
Model	ZBT-WG3526
Firmware Version	LEDE Reboot r0+2292 / LuCI Master (git-16.324.51057-1c27f6b) from 22.11.2016
Kernel Version	4.4.32
lede-ramips-mt7621-zbt-wg3526-squashfs-sysupgra..> 22-Nov-2016 12:56             3932323

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=301