Ralink RT5572 2,4GHz performance

Hardware Questions and Recommendations
1

Hi folks!

I have a usb wifi adapter with Ralink RT5572 (300Mbit/s) chipset running on PineA64+, connected to a usb 2.0 port. It runs flawless except of the bandwith, what is ~45Mbit/s on 2,4GHz, 20MHz channel with, N mode. Tested on my Lenovo with 2x2 Intel N-2200 with "iperf", 4m away, clear view, but approx. 30 other access points around. 5GHz is not an option, my clients only have 2,4GHz wifi.The PineA64 usb should not be the bottleneck, on my usb lan adapter I get 270-300Mbit/s on usb 2.0.

What do you think about the weak performance?

2

On 20MHz channel width you can get maximum ~105Mbit, but if there are 30AP around, I consider 45Mbit/s as a good result

3

On one stream or both? The adapter is 2x2 (2 antennas).

4

I know; for 1 stream theoretically phy rate is 72Mbit/s, about 50 Mbit/s in use.

5

I did a second test with my linux tablet with 1x1 wifi and get the same result ~45Mbit/s. So if the RT5572 would be 1x1 also it would be ok. But with 2x2..

6 
Band 1:
		Capabilities: 0x2fe
			HT20/HT40
			SM Power Save disabled
			RX Greenfield
			RX HT20 SGI
			RX HT40 SGI
->          TX STBC
->          RX STBC 2-streams
			Max AMSDU length: 3839 bytes
			No DSSS/CCK HT40
		Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
		Minimum RX AMPDU time spacing: 2 usec (0x04)
		HT TX/RX MCS rate indexes supported: 0-15, 32

It's possible, that the RT5572 uses only 1 stream for TX? The specs say "2,4GHz up to 150Mbit/s" what would be the data rate for 1 stream on 40MHz channel.
Mysterious

8

I did some further test with iperf, client on LAN, server on wifi:

2,4GHz, 20MHz channel width: 30-45Mbps
2,4GHz, 40MHz channel width (forced): 60-75Mbps
5GHz, (40MHz channel width?): 65-75Mbps

Strange that the 5GHz is equal to 2,4GHz, 40MHz. Well, maybe that's the price to pay for a 17€ wifi dongle with open source driver!? Since my internet rate is 30/5 Mbps I'm not too scared, but if someone with Ralink RT5572 could share his experience it would be nice....