[Fwd: Xo 1.5 wlan]

[Tomeu Vizoso]

On Mon, Jun 1, 2009 at 07:20, Andrés Ambrois <andresambrois at gmail.com> wrote:
> 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.

Ok, then it may have been a improvement in that particular wifi driver.

Regards,

Tomeu

> 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
>