wifi for 600, alex

Thu Feb 15 21:22:54 UTC 2007

> There are things underway that can mitigate some of this, 
> neighbor lists for example.

For the sake of the lists topic centrism, I was avoiding getting into
points like that. :) Which brings me to the part about:

> Hmm. I think it would be good to frame which parts of a "CDMA 
> system" (whatever that actually refers to ;-) you mean by that

Well, neighbor lists for one. That is, if a client device is continually
informing something like a "BSC" what it perceives is the 'hearable
topology,' we can then implement far more useful logic in the BSC to
better direct the underlying activities. Second is network assisted
handovers and handoffs (even in the absence of policy-knobs such as
neighbor lists). Perhaps third would be more related to the way the PCF
shim can be used to schedule up and downlink activity in each BTS by a
rather "well informed" BSC. Perhaps even more useful would be support
like handup/handown for moving clients (when possible) from .11g to
.11a, just like CDMA BSC's would do to direct a mobile station between a
classic IS-95 BTS to IS-2000 BTS. 

Anyway, I don't mean to stray too far off topic, but indeed there are
many 'good' things already designed (some decades ago) and understood
within the wireless community which would be well to appear in .11 at
some point. Hopefully my comment makes more sense now! :)

> There's actually a lot more to clean hand-overs between AP.  
> For starters, you need to know what's around, find them(!) 
> (i.e., channel), and reestablish any security associations 
> and take care of IP mobility (at least at scale).

Indeed. IAPP and things like it were designed to assist or deal with
carry-over of authentication after all the layer-2 and 1 things are
accounted for. Who even interoperates with IAPP today? 

> And which have similar scaling challenges with small cell 
> sizes and mobility.  In fact, you could argue the model is 
> particularly challenged in that case.

Some aspects are improved even in small, dense environments. Some of the
interesting work that Meru does is to aggregate & schedule back to back
.11 frames for things like RTP delivery. Meru, for example, also
globally schedules & coordinates delivery across all APs for specific
management messages. But even still, you cannot create capacity where
there is none, so if there's simply no free RF, we're hosed.

> So goes the theory at small scale, yes.  And I would contend 
> that "RF- ideal" is something you will only find inside of an RF tent.

I should have said 'comparatively equal' to whatever shade of grey is
available... :)

> I don't I agree.  Having QoS mechanisms in a cooperative, 
> unlicensed frequency has its limitations, rather than 
> anything amounting to scheduled access.  And scheduled access 

I see your point there. In the case of .11e and EDCF, significant
improvement can be had even if only one half of the path has the
support. In our cases, yea, we only down control of the downlink to the
mobile station. I'm not sure I'd even want clients using
"self-medicated" EDCF, so the unlink prioritization/scheduluing issue
looms large without a great solution.

> in WiFi is of limited availability in chipsets today, not to 
> mention incompatible with non- scheduled access.

Check out EDCF. It's not changing any fundamental part other than the
radios behavior during CCA backoff, and any client can benefit from it.
Also, I explain how it works briefly in the lightning talk video. 

-Tk