[Ns-developers] wireless PHY project
Thierry.Turletti at sophia.inria.fr
Fri Oct 27 07:37:23 PDT 2006
Ruben Merz a écrit :
> Lee, Thierry,
>>> Actually, in some cases, it is interesting to get a "realistic" bit
>>> error mask by packet -- for example, when you want to evaluate the
>>> quality of a "robust" video transmission using UDPLite. This could be
>>> an interesting _option_...
>> DCCP supports partial coverage CRC and is also a candidate for Video
>> transmission. Of course, if lower layers drop the packet than it
>> isn't very useful, so having the option for known incorrect/imperfect
>> frames would be useful.
> Out of curiosity, do you need to have the full packet (understand all
> the bit) transmitted to the upper layer(s) or (a) only a subset, say
> only the set of bit that are erroneous or (b) only the statistics of
> the error process on the bit?
> Because, if you only have to generate some statistics, it is in terms
> of complexity much lighter than to generate all the bits of a packet
> and then to have a look at all of them for potential errors. In other
> words, should the simulator stop at the packet-level or be able go
> down to the bit-level?
as an option only, yes, I believe it would be interesting to go down to
the bit-level. For example, the bit-error masks can be applied to real
video packets. These masks could be generated by some PHY model . You
can also imagine to implement Viterbi decoding as you mention below and
get soft state per bit, which would be much more cpu greedy -- and I
already know several experts in image/DSP that would love to get such
an option ;-)
> I believe NS-3 should be a packet-level network simulator and should
> avoid dealing with bit directly, mostly because the complexity is way
> too high: you would not like to simulate a Viterbi decoder in every
> node. On the other hand, computers are becoming more and more
> powerful, and maybe this should be an option. Mathieu, are there any
> guidelines about this? Also, what are thinking other people on this list.
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