Iw dev station dump interpretation

Hi,

I am new to openwrt. I am collecting iwdev station dump results periodically. The following result is stored. I need to know the difference between signal and signal avg. ? and also what are the 4 values within the square bracket. (signal: -55 [-65, -56, -95, -95] dBm)?

inactive time:	4470 ms
	rx bytes:	26333626454
	rx packets:	18541754
	tx bytes:	438581
	tx packets:	5061
	tx retries:	0
	tx failed:	12
	rx drop misc:	19
	signal:  	-55 [-65, -56, -95, -95] dBm
	signal avg:	-55 [-65, -56, -95, -95] dBm
	tx bitrate:	400.0 MBit/s VHT-MCS 9 40MHz short GI VHT-NSS 2
	rx bitrate:	12.0 MBit/s
	rx duration:	754069640 us
	authorized:	yes
	authenticated:	yes
	associated:	yes
	preamble:	long
	WMM/WME:	yes
	MFP:		no
	TDLS peer:	no
	DTIM period:	2
	beacon interval:100
	short slot time:yes
	connected time:	1171 seconds

(Moved to the For Developers section.)

Looking through code, I see:

		printf("\n\tsignal:  \t%d %sdBm",
		printf("\n\tsignal avg:\t%d %sdBm",

I also see a 4, 3, 2, 1 section...I'm quite rusty, and don't see what interval or time frame it's using. That was just from my quick browse.

Feel free to review code yourself: https://mirrors.edge.kernel.org/pub/software/network/iw/

iw gets measurements from nl80211. Looking into the code I see following attributes:

 * @NL80211_STA_INFO_SIGNAL: signal strength of last received PPDU (u8, dBm)
 * @NL80211_STA_INFO_SIGNAL_AVG: signal strength average (u8, dBm)
 * @NL80211_STA_INFO_CHAIN_SIGNAL: per-chain signal strength of last PPDU
 *	Contains a nested array of signal strength attributes (u8, dBm)
 * @NL80211_STA_INFO_CHAIN_SIGNAL_AVG: per-chain signal strength average
 *	Same format as NL80211_STA_INFO_CHAIN_SIGNAL.

My best guess is that the signal strengths between brackets indicates the dBm value for each antenna/receiver. I presume in your case you have 4 + 4 mimo hardware thus 4 values btwn brackets. I have 3 + 3 and iw dev station dump indicates "only" 3 values btwn brackets in my case. Furthermore in your example I see -95 dBm (no signal - only noise) as value 3 and 4 which makes sense as VHT-NSS value is 2 (only 2 spatial streams are used during that specific measurement).

https://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless.git/tree/include/uapi/linux/nl80211.h?id=HEAD

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