High latency and sound distortion when using WiFi (X200t)

[geka3250]

Hello!
I'm using Thinkpad X200t. When using WiFi system starts to lag, sound becomes distorted. Default card for this laptop is Intel 5300 ABGN. I swapped it to Advanced-N 6200 with the same result. But if N-mode disabled system latency is normal.
After that I installed Broadcom BCM4313 and it works fine, but with link limit 65mbps. Intel WiFi able to link at 300mbps.
My OS are WIN8.1 x64 and WIN10 x64.
Here is screenshots of latency when downloading same file with the same speed limit set at 4mb/s:

Intel 6200


BCM4313


Installed different drivers with no result.
Can X200t users test N-type connection with DPCLAT on high speeds?
Thanks

[geka3250]

Same latency spikes with Intel Wireless-N 2230.
Latency source in all cases is windows network driver - ndis.sys

[rjwilmsi]

Well, I can't answer directly, but I observe what sounds like the same sort of issue under Linux on X200s, X220 and T410 machines (all with Intel Wi-Fi cards): I find that sometimes Wi-Fi doesn't work well (either refuses to connect in case of X200s or in case of X220 or T410 becomes intermittently very slow, with ping times varying from 20 to 2000 ms to the same site with significant packet loss) and the workaround is to disable 802.11n mode, which fixes the problem (consistent ping times, no packet loss). Sounds to me like you see the same/very similar issue under Windows, so it's either a driver or hardware limitation/issue. With these machines spanning a couple of years it suggests Intel won't or cannot fix the issue anytime soon, so I stick with the simple workaround.

As I understand it if 802.11n is disabled then max speed would be 802.11g i.e. 54 Mbit/s, which for me given my internet connection is only 12 Mbit/s and I do limited internal network transfers is no issue, but there are some people with 100 Mbit/s or higher connections where this workaround would be limiting.

For info, under Linux to disable 802.11n mode for Intel Wi-Fi card when using NetworkManager, as root do:
service NetworkManager stop
rmmod iwldvm
rmmod iwlwifi
modprobe -v iwlwifi 11n_disable=1
service NetworkManager restart

[geka3250]

Shame on Intel they haven't fixed such a problem and discontinued support for these cards.
And yes, BG-mode gives max link rate 54mbps with real connection speed 25-30mbps.
Im using BCM94313 without any problems in N-mode at link 65mbps with real speed 40-45mbps now.
Waiting for Atheros QCWB335 combocard WiFi&Bluetooth. Hope it'll give more speed