[e2e] I got lost in opportunistic scheduling.
detlef.bosau at web.de
Wed May 16 03:27:30 PDT 2007
Khaled Elsayed wrote:
> There are some papers that discuss the relation between OS at MAC/PHY
> and TCP. For example check
> But there are also more recent stuff.
As I see, I got this paper before but did not pay enough attention to it.
1. As far as I see, OS/multiuser diversity is yet employed in the
Qualcomm 1xEV-DO wireless system. (Is there a name for it, which one can
say within a lifetime? *got scared*)
Are there other systems which employ OS?
2. Qualc..., say C3P0, it´s shorter :-), seems to have a _common_
downlink and _dedicated_ uplinks. Is this correct? In the paper, the
uplinks are said to be "asynchronous circuit-switched". What does that
mean? (I already got criticism this year because I talked about packet
swichting in wireless networks, because packet switching were not
restricted to wireless networks or something like that.... I didn´t
understand it.) Does it mean, we have dedicated TDM channels with
something like HDLC on it to enable packet transport?
3. Somwehere in the paper, a reliable link control / reliable link
protocol is mentioned. What kind of protocol is used here? Something
like RLPv3, which fragments L3 packets into pieces of e.g. about 20
bytes? Or do we deal with IP packets directly? Particularly, does C3P0
emply any ARQ? Or does it only use FEC?
4. If C3P0 emplys ARQ and some RLP, does it use sliding window? Or does
it use stop´n wait?
5. If C3P0 only uses FEC, one could be somewhat extreme and don´t really
use even that, at least don´t use extreme spreading but one could rely
upon OS only. One goal of OS is to avoid errors in advance rather then
correct them afterwards. So one could work with only little error
correction capability intentionally. Or one could work with extensive
adaptation of channel coding / puncturing. How is this done in C3P0?
> I think that implementation of pure OS without some compensation for
> users with consistent bad channels does not make sense. I have some
> results on that for RT services that was published in MSWIM 2004.
> E-mail me if interested.
Of course, I´m interested!
Question, somewhat provoking: Does it make sense to combine OS and RT
services? Somewhere on David Tse´s "talk" (he has so many slidesets of
this one talk on his homepage that I wonder if he ever gave another one
=8-)) we learn something about voice vs. data. (Unfortunately it´s not
mentioned on the slides _what_ we learn =8-))
But I think it hardly makes sense to mixup voice and data, because data
requires data integrity and voice requires time integrity _AND_ can
tolerate errors. In data services, you either have corrupted packets or
you have error free packets. Is there a way to allow for "half correct
So, at least at this moment, I think, data services and _error_
_tolerant_ RT services should be done seperately. Or what do you think?
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