[mythtv-users] Anyone know if the ar9170usb driver is supposed to support 802.11n?

[Scott Alfter]

I wanted to move a machine I'd set up as a MythTV frontend into a room without
a wired connection.  Knowing that I'd had less than optimal results in the past
streaming to my notebooks over 802.11g, I figured I'd give 802.11n a
shot...it'd be easier than stringing cable into the room.  I figured I'd get
dual-band equipment and run a dedicated video network on the 5-GHz band,
leaving my existing 802.11b/g service up and running for other purposes.

First, I just bought a dongle.  I started with a Netgear WNDA3100, but the
current version uses a Broadcom chipset not supported by Linux.  I swapped that
out for a D-Link DWA-160, which is supported by the ar9170usb driver.  It
connected without issue to my WRT54GL, and actually seemed to work well most of
the time streaming HD H.264 and SD MPEG-2 streams.  Sometimes playback would
pause for a few seconds at a time; maybe it was interference from other 2.4-GHz
devices in the building (multiple WiFi access points within range, and who
knows what else).

Yesterday, a D-Link DAP-1522 arrived.  I used it to replace the gigabit switch
in the stack of networking gear on top of the TV, set it up to offer 802.11n
service on the 5-GHz band, secured it, etc., and then made the appropriate
setting changes in the frontend.

If the access point is set to offer 802.11n only, the frontend won't connect to
it.  If I set it to do both 802.11a and 802.11n, it will connect.  HD MPEG-2
streams sometimes play properly; other times, they pause frequently.  While
this is an improvement over 802.11g, it's still not optimal.  That it works at
all only while 802.11a is enabled suggests that it's not actually using
802.11n, even though the hardware at both ends of the link now supports it.  Is
802.11n actually supported by the ar9170usb driver, or are only the slower
modes (802.11a/b/g) supported at this time?  Are there other parts of the
software stack that need to be upgraded for 802.11n support?  My last "emerge
world" was only a couple or three weeks ago, so the software on this machine is
fairly up to date.

(The frontend is an Acer Aspire Revo 1600, with the stock configuration of 1 GB
RAM and no built-in WiFi.  It's booting into Gentoo, with gentoo-sources 2.6.35
and MythTV 0.23.1.  A Bluetooth dongle receives input from a Playstation 3
remote control and (when needed) an Apple Wireless Keyboard.  A
VGA-to-composite converter connects it to an old big-tube TV.)

Scott Alfter
scott at alfter.us