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→Non-DFS channels
(Added info on FCC wifi channel rules) |
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*157 - 5785 MHz (5765-5805) | *157 - 5785 MHz (5765-5805) | ||
*161 - 5805 MHz (5785-5825) | *161 - 5805 MHz (5785-5825) | ||
:Beware that [https://dev.openwrt.org/ticket/10136 you cannot use channel 165 as part of a HT40+/- channel] | |||
Maximum power output for these channels at 20 or 40 mhz is [http://louise.hallikainen.org/FCC/FccRules/2011/15/407/ 1 watt], with the following caveats: | Maximum power output for these channels at 20 or 40 mhz is [http://louise.hallikainen.org/FCC/FccRules/2011/15/407/ 1 watt], with the following caveats: | ||
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</blockquote> | </blockquote> | ||
=== DFS channels == | === DFS channels === | ||
None of the DFS channels allow more than 250 mW output power. The TPC requirement only applies if the EIRP is more than 500 mW. | None of the DFS channels allow more than 250 mW output power. The TPC requirement only applies if the EIRP is more than 500 mW. | ||
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Using a frequency analyzer or software-defined radio with a wide frequency range, it's possible to scan the actual frequency usage across the entire range of interest. Elonics 4000 can scan from 64 mhz to 2.2 ghz and only costs about $25. | Using a frequency analyzer or software-defined radio with a wide frequency range, it's possible to scan the actual frequency usage across the entire range of interest. Elonics 4000 can scan from 64 mhz to 2.2 ghz and only costs about $25. | ||
= OpenWRT setup = | |||
== 5 GHz == | |||
Here are some (possibly?) reasonable settings for a point to point or point to multi-point 5 GHz rooftop node: | |||
<pre> | |||
channel 149 | |||
hwmode 11na | |||
htmode HT40 | |||
chanbw 20 | |||
txpower 20 | |||
noscan 1 (?) | |||
</pre> | |||
These OpenWRT settings are documented [http://wiki.openwrt.org/doc/uci/wireless#common.options1 here]. | |||
I'm not actually sure what the noscan feature does or whether it's a good idea. There's a warning that it will violate regulatory requirements, but I'm not sure if it's related to DFS or if it's something else. - ([[User:Juul|Juul]] ([[User talk:Juul|talk]])) | |||
The ath9k driver does not yet have support for a 802.11n-only mode (also known as greenfield). The closest is 802.11n+a. Apparently you can prevent 802.11a nodes from associating somehow. [http://comments.gmane.org/gmane.linux.drivers.ath9k.devel/10735 source]. | |||
I'm not sure how to set the guard interval. The default is likely 800 ns, which we may want to lower for shorter links or heighten for longer links. | |||
= Hardware capabilities = | |||
== 5 GHz == | |||
Data rates for various settings can be looked up in [http://en.wikipedia.org/wiki/IEEE_802.11n-2009#Data_rates this table]. | |||
=== Nanostation M5 === | |||
Assuming 40 MHz channel and 800 ns guard interval: | |||
<pre> | |||
Setting | Speed | Modulation | Tx power | Rx sensitivity | | |||
------------------------------------------------------------------------ | |||
MCS12 | 162 Mbit/sec | 16-QAM | 22 dBm / 157 mW | -84 dBm | | |||
MCS13 | 216 Mbit/sec | 64-QAM | 20 dBm / 100 mW | -79 dBm | | |||
MCS14 | 243 Mbit/sec | 64-QAM | 18 dBm / 63 mW | -78 dBm | | |||
MCS15 | 270 Mbit/sec | 64-QAM | 17 dBm / 50 mW | -75 dBm | | |||
</pre> | |||