[Fwd: Xo 1.5 wlan]

[Andrés Ambrois]

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 [0] 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. 

[0] 
http://linuxwireless.org/en/developers/Documentation/mac80211/RateControl/minstrel


>
> > 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