Re: Questions about 802.11n support

[T. Jameson Little]

On Wed, Mar 04, 2015 at 09:28:42AM +0100, Stefan Sperling wrote:
 The actual amount of work depends on when you consider support complete.
 11n has such a large feature set and optional parts that you can't
 simply say this is an 11n device to explain what your device can do.
 
 Are you done when one driver supports 11n? When all drivers capable of
 11n support it? Out of the 77 modulation and coding schemes, which ones
 do you want? For stations the minimum is 8 out of those, which leaves
 you with a maximum 72Mbit/s (single-channel at 2Ghz). APs need at least
 16 of them (maximum 144Mbit/s). Do you want 150Mbit/s (single antenna
 maximum)?
 
 Or do you require MIMO (multiple antennas), with a maximum of 300Mbit/s
 with 2 antennas? 450 Mbit/s with 3 antennas? 600Mbit/s with 4 antennas?

I honestly just want 5GHz to work at minimum speeds in AP mode on a usb
wireless dongle. I run into interference on 2.4GHz because it's far too
common. I imagine that once this works, adding additional modulation
and coding schemes would be much easier.

Since USB 2.0 has a maximum throughput of 480Mbit/s, anything higher
than 300Mbit/s is not particularly important, and many consumer devices
only support 150Mbit/s anyway. 72Mbit/s is completely fine for an
initial implementation.

  I don't want to discourage you, but AP support for 11n will be quite
  an effort.  Even if somebody gets 11n to work, I think it will be hard
  work to make it work well.  Some people here will claim that OpenBSD
  11a/11g APs don't really work very well.
 
 My 11a athn(4) AP is working quite well.
 Apart from the fact that the soekris hardware won't really keep up
 when I pump data from cable to antenna at 54Mbit/s. 11n support would
 definitely require slightly more modern hardware ;-)

Well, I'm much more capable of fixing existing drivers to make it work
well than building something from scratch, and I imagine the same is
true for many developers, because you work on whatever affects you.

So, last question, where exactly does 11n support sit in the list of
features to be added to OpenBSD?

I understand that there are many worthy projects that require ongoing
work (e.g. LibreSSL, OpenNTPD, OpenSSH, etc), and I also understand
that many people don't need 11n support. If 11n really isn't a
priority, then I'll probably use FreeBSD as my AP until it becomes a
larger priority (I'd really prefer OpenBSD, but I can still use it as
a router). I'm moving my home network to 5GHz only because of
interference issues, and I may do the same soon at work if it works
out well.

Questions about 802.11n support

[T. Jameson Little]

From what I've been able to gather, there is no 802.11n support in
OpenBSD because more work is needed in ieee80211(9). I would greatly
appreciate it if someone could answer a few questions for me:

* Is anyone working on this?
  * If so, is there any way that I could help?
  * If not, who would be the best to ask about where to get started?
* How much work is required? Is the work required in the order of days,
  weeks, months?
* Would parts of FreeBSD's implementation be useful, or are the two
  network stacks different enough that a new implementation is
  required?

I'm a relatively competent C programmer, but I have very little
experience with kernel code, much less network protocols. I would
like to use OpenBSD as an access point, but I need wireless-n @ 5GHz in
order to do so, so I'm motivated enough to allocate some time for
testing and even writing code. I could probably also supply some basic
hardware if that would help, though I don't have a big budget.