[Fwd: Xo 1.5 wlan]
andresambrois at gmail.com
Mon Jun 1 01:20:31 EDT 2009
On Sunday 31 May 2009 11:15:58 am Tomeu Vizoso wrote:
> On Sun, May 31, 2009 at 16:09, Tiago Marques <tiagomnm at gmail.com> wrote:
> > On 5/31/09, John Watlington <wad at laptop.org> wrote:
> >> On May 30, 2009, at 12:04 PM, Reinder E.N. de Haan wrote:
> >>> Subject: Xo 1.5 wlan
> >>> Date: Thu, 07 May 2009 19:56:27 +0200
> >>> From: Reinder de Haan <rs at mveas.com>
> >>> To: John Watlington <wad at laptop.org>
> >>> Hello,
> >>> I have a couple of questions regarding the wlan module in xo 1.5;
> >>> 1) will it be an off the shelf module (3th party) or a quanta/olpc
> >>> 'private' module
> >> One of the complications of the Gen 1.5 design has been improving
> >> the WLAN module. The existing module takes lots of power, and
> >> the USB driver still needs extensive modification to speed up
> >> suspend/resume.
> > Being power the major concern, will wireless range also be enhanced in
> > some way? Most of the early claims that the XO had a top class
> > wireless range have not materialized, at least when I compare it to
> > other devices like a Fon2100 or an IPW2200 from Intel, which is
> > probably the device with best wireless range that I've ever seen.
> > A way to change the transmit power in software would be great for
> > power and range, depending on the application. Does the module have
> > anything like that or are you just mainly focusing on power and
> > relegating range to 2nd place?
> I think that there have been recent improvements in the algorithm for
> choosing the transmission power in the linux kernel. I'm not sure if
> all wifi drivers benefit from it, but a laptop with b43 has improved
> dramatically its range after updating to Ubuntu Jaunty.
I think what you're talking about is the rate selection algorithm, I dont
think the kernel dynamically changes the Tx power.
Linux has moved to minstrel  as its default rate control algorithm, which
is way better than what we had previously in dealing with lots of collisions,
where slower rates may not increase the chance of getting a packet through.
This scenario is common in schools with lots of XOs.
Some drivers still have their own algorithm, it is probable that the closed
fullmac Marvell implementation has one.
> > Best regards,
> > Tiago Marques
> >> Unlike Gen 1, we don't have the time or expected market to
> >> develop and certify a custom module.
> >> The current plan is to use an existing WLAN module, based on
> >> the Marvell 88W8686 and connected to the system using an
> >> SDIO interface.
> >>> 2) if it is a private module please break out jtag and the serial port
> >>> for debugging (xo 1.0 only had jtag.. serial ended right at the
> >>> balls of
> >>> the chip :-(
> >> Sorry, the module doesn't bring any of the internal debugging signal
> >> out.
> >>> 3a) if its a 3th party moduel is it posible to buy it somewhere ?
> >> Yes and no. There are 88W8686-based SDIO modules already
> >> available, and electrically/software-wise they will be identical to the
> >> one we are planning to use.
> >> The actual module used in XO-1.5 will have a half-height miniPCI-e
> >> form factor. Even if you could buy it in small quantities, you
> >> would have
> >> to arrange an adapter board to use internally.
> >> Cheers,
> >> wad
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