What is txpower? Should I be able to set txpower higher than 30?
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I have one of these wireless cards. Here's the datasheet (pdf). Here's the info from ifconfig -v ath0_wlan0.
ath0_wlan0: flags=8943 <up,broadcast,running,promisc,simplex,multicast>metric 0 mtu 1500 ether 00:80:48:71:10:41 inet6 fe80::280:48ff:fe71:1041%ath0_wlan0 prefixlen 64 scopeid 0x9 nd6 options=3 <performnud,accept_rtadv>media: IEEE 802.11 Wireless Ethernet autoselect mode 11g <hostap>status: running ssid ALIX0 channel 6 (2437 MHz 11g) bssid 00:80:48:71:10:41 regdomain FCC country CA indoor ecm authmode WPA2/802.11i -wps -tsn privacy MIXED deftxkey 3 AES-CCM 2:128-bit AES-CCM 3:128-bit powersavemode OFF powersavesleep 100 txpower 30 txpowmax 50.0 -dotd rtsthreshold 2346 fragthreshold 2346 bmiss 7 11a ucast NONE mgmt 6 Mb/s mcast 6 Mb/s maxretry 6 11b ucast NONE mgmt 1 Mb/s mcast 1 Mb/s maxretry 6 11g ucast NONE mgmt 1 Mb/s mcast 1 Mb/s maxretry 6 turboA ucast NONE mgmt 6 Mb/s mcast 6 Mb/s maxretry 6 turboG ucast NONE mgmt 1 Mb/s mcast 1 Mb/s maxretry 6 sturbo ucast NONE mgmt 6 Mb/s mcast 6 Mb/s maxretry 6 11na ucast NONE mgmt 0 MCS mcast 0 MCS maxretry 6 11ng ucast NONE mgmt 0 MCS mcast 0 MCS maxretry 6 half ucast NONE mgmt 3 Mb/s mcast 3 Mb/s maxretry 6 quarter ucast NONE mgmt 1 Mb/s mcast 1 Mb/s maxretry 6 scanvalid 60 -bgscan bgscanintvl 300 bgscanidle 250 roam:11a rssi 7dBm rate 12 Mb/s roam:11b rssi 7dBm rate 1 Mb/s roam:11g rssi 7dBm rate 5 Mb/s roam:turboA rssi 7dBm rate 12 Mb/s roam:turboG rssi 7dBm rate 12 Mb/s roam:sturbo rssi 7dBm rate 12 Mb/s roam:11na rssi 7dBm MCS 1 roam:11ng rssi 7dBm MCS 1 roam:half rssi 7dBm rate 6 Mb/s roam:quarter rssi 7dBm rate 3 Mb/s -pureg protmode OFF -ht -htcompat -ampdu ampdulimit 8k ampdudensity NA -amsdu -shortgi htprotmode RTSCTS -puren smps -rifs -wme burst -dwds -hidessid apbridge dtimperiod 1 doth -dfs inact bintval 100 groups: wlan</hostap></performnud,accept_rtadv></up,broadcast,running,promisc,simplex,multicast>A post on another forum says txpowmax is 2x the actual max dBm. This seems right since my card has a tolerance of +1dBm/-1.5dBm, meaning txpowmax should be 49-54.
Now, the part I'm unsure about is txpower. Is it dBm or is it a percentage of txpowmax? The dd-wrt wiki says it's dBm, but I've seen posts on this forum where people have a txpower value that is higher than txpowmax. My values above don't make sense to me either since txpowmax indicates 25dBm is the max power, but txpower would be at 30dBm.
If I change the regulator domain from CA (FCC) back to the default, which uses US (FCC), the card defaults to 26 for txpower. I'm a bit confused and Google hasn't been much help tonight. Can anyone explain to me what kind of values I should expect for txpowmax and txpower and what I should be setting them to if they need to be overridden?
Edit: I forgot to mention, I can set txpower to anything below 30 by using ifconfig ath0_wlan0 txpower XX where XX is a value (ex: 20).
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<rd id="fcc"><name>FCC</name>
<sku>0x10</sku>
<defcc ref="US"><netband mode="11b"><band><freqband ref="F1_2412_2462"><maxpower>30</maxpower>
<flags>IEEE80211_CHAN_B</flags></freqband></band></netband>
…
<country id="CA"><isocc>124</isocc> <name>Canada</name></country>No, 30 is max for US and Canada. If you want higher, you have to force it to go unregulated. which may or may not work, and may or may not actually increase the power, and may or may not violate applicable laws in your area... (technically... though I'm not sure anyone has been arrested/fined for that...)</defcc></rd>
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FYI- That's from /usr/src/etc/regdomain.xml and there are more power levels depending on the band…
<netband mode="11b"><band><freqband ref="F1_2412_2462"><maxpower>30</maxpower> <flags>IEEE80211_CHAN_B</flags></freqband></band></netband> <netband mode="11g"><band><freqband ref="F1_2412_2462"><maxpower>30</maxpower> <flags>IEEE80211_CHAN_G</flags></freqband></band></netband> <netband mode="11a"><band><freqband ref="F1_5180_5240"><maxpower>17</maxpower></freqband></band> <band><freqband ref="F1_5745_5805"><maxpower>23</maxpower></freqband></band> <band><freqband ref="F1_5825_5825"><maxpower>23</maxpower> <flags>IEEE80211_CHAN_PASSIVE</flags></freqband></band></netband> <netband mode="11ng"><band><freqband ref="F1_2412_2462"><maxpower>30</maxpower> <flags>IEEE80211_CHAN_G</flags> <flags>IEEE80211_CHAN_HT20</flags></freqband></band> <band><freqband ref="F1_2412_2462"><maxpower>30</maxpower> <flags>IEEE80211_CHAN_G</flags> <flags>IEEE80211_CHAN_HT40</flags></freqband></band></netband> <netband mode="11na"> <band> <freqband ref="F1_5180_5240"> <maxpower>17</maxpower></freqband></band></netband> -
Thanks for the reply. From what you've said, txpower is dBm, so I have a few more questions then. The card I have lists 26dBm as the max and 23dBm @ 54Mbps. I had assumed txpower was something read from the wireless card and was the power level the card was currently transmitting at, but that's not right, is it?
Something else that confuses me then is why the transmit power in the GUI shows 0-99 if the selected regulatory domain is going to limit it to 30. Are they even related? Changing that setting in the GUI doesn't do anything for me even though I know I can change txpower on my card. Using ifconfig ath0_wlan0 txpower 5 will cause the signal to be a couple bars weaker with my AP about 5 feet from my desk.
Ignoring the GUI, I'm assuming with a txpower of 30 my wifi card will be asked to use 30dBm, but won't go above 26dBm internally. Is that correct?
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I have read somewhere the TX power units in freebsd arerepresented by 0.5 dbm.
Meaning 30 dbm = 30*0.5=15 dbm=30 mWJimp can you confirm this ?
thanks
Edit: I read it here
http://osdir.com/ml/freebsd-wireless/2011-08/msg00052.html -
The author of that e-mail would know more than me. I don't know about that low down.
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Thanks Jimp
JPtech i have been looking allover for the listing of wireless caps on freebds an finaly i have found them ;D
http://www.freebsd.org/cgi/man.cgi?query=ifconfig&apropos=0&sektion=8&manpath=FreeBSD+8.1-RELEASE+and+Ports&arch=default&format=htmlHope it will help you (some pages down look for "The following parameters are specific to cloning IEEE 802.11 wireless…")
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That mailing list post might be specific to the Intel iwn(4) driver. From what I can tell, txpower is set in increments of .5dBm and stored, internally, as an integer. When I set it to 20.5 it works, but 20.6 gives an error:
ifconfig: invalid tx power (must be .5 dBm units)So, to me, that means the value shown by txpower is definitely in dBm. I'm still confused about txpowmax being 50.0 though. Is it 2xdBm? I also don't know why txpower can be set above 26dBm for my specific card.
I subscribed to the freebsd-wireless mailing list and sent a message to it to see if someone there can give a better explanation. With the exception of the GUI setting it doesn't look like pfSense actually touches any of the parts involved.
