Question Router Operating in Mixed Mode Delivers Slow 2.5GHz Performance


Feb 14, 2010
Hello. I have an old Lenovo G560 laptop with Broadcom 802.11n wireless network card. I wanted to connect it to my TP-Link Archer C6U wireless router. It did not detect 5GHz signal so I switched on mixed mode with 2.5GHz. It could not connect successfully but the maximum download speed was 35mbps at most. I disabled mixed mode and enabled only 2.5GHz to test if same is experienced on that laptop and on my smartphone. There was no difference. I have not tried other devices but most likely I won't see difference. Strangely wireless card DELL DW1530 802.11n(Broadcom too) on my old Dell Latitude laptop is able to pick 5GHz and work at almost full speed.

5GHz on my router works very well. It's just 2.4GHz that is even slower than 2.5GHz on my 10 year-old Edimax BR-6428nS that I replaced with current router. Could it be that they cheaped out on 2.5GHz radio on TP-Link Archer C6U?

I also started noticing once in a while disconnections on my smartphone from my router in mixed mode. I have checked the log but can only see one message repeating:

not sure if it was a typo but there is only the 2.4g radio band for wifi. Mixed mode generally means it also support older protocols and in theory if you were running a mix of devices it could slow the rates. I doubt you have 802.11b devices you are using.
It would not be unusual to only get 35mbps on 2.4. Many times even using fancy data encodings that claim numbers like 600 on 2.4 you get only 80-90mbps.

Your first step would be to see what connection rate it shows on the interface. This is more the data encoding rate rather the actual speed. You many times will see 150 or maybe 300 on 2.4 but if it can only use 20mhz channels and only 1 mimo channel it will get 72.2
You only get a very small fraction of these so called rates so it could be as simple as you are only connecting at 72.2. You might force your router to use 40mhz radio bands if that is possible.

Why it can't see the 5g radio can be many things. Not sure about a laptop that old since it likely does not support windows10 officially and many times the drivers used are older ones. What I would normally recommend is to try to find a unix USB boot image that would let you try a different OS to see if you have a hardware issue or if it is some crap windows setting thing. These USB images run 100% from the stick and do not install on your hard drive.....many do have a option so be careful what you click. It appears your laptop is all intel parts so it is likely you can find a image that has support. Laptops can be very strange at times and need special drivers....lenvo in particular. Still there is little risk since you are not installing anything you just unplug the USB and reboot.

I am going to bet it is some driver or software setting because the wifi in end device is a single chip that can switch between 2.4 and 5 unlike a router that has 2 different chips one for each. You would think it would fail on both 2.4 and 5 but hardware stuff you really don't know.
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