Re: Regarding use of Reed-Solomon code in wireless networks

Am 06.05.2015 um 08:14 schrieb Debarshi Sanyal:
> Hi,
>
> Hi,
>
> We were working on design of wormhole detection methods in MANETs.
> To achieve detection, we propose to measure the time taken for a test non=
ce
> to move from one node to it's neighbor node. If the time taken is larger
> than the expected time for a packet to travel between two neighbor nodes,
> the link is probably a wormhole link.
>
> Now to combat channel errors, is it worth encoding the nonce with
> Reed-Solomon code?

ANY (emphasis on ANY) wireless network I know, employs a recovery layer.

I should add: I do not know even one single exception.

Hence, the time for a packet to "travel" from one node to a neighbour is
highly volatile. In general, it isn't even stationary, hence it doesn't
even make sense to observe or to measure an "average value" here or some
kind of expectation.

What RS codes is concerned: RS codes may be - and are - used in computer
networks. A closer look to your hardware's documentation will exhibit,
if your hardware uses RS codes or other coding schemes.

That's a reason for my frequent comments on this issue: In summary, the
quite sad truth is: packet latencies in wireless networks are pretty
useless for any kind of
- load analysis,
- congestion analysis,
- wormhole detection
and the like, as you will run into the well known "cum hoc ergo procter
hoc" fallacy almost for sure.



>
> Our understanding is that propagation time between neighbor nodes in
> commodity wi-fi setups is much smaller than the time taken to encode and
> decode a nonce (say, 64 bytes long). So delay variations in encode/decode
> process will easily mask any delay in propagation time.
>
> We would be immensely thankful if you could throw some light on this since
> we do not have access to hardware platforms to get real measurements. We
> are interested to know the approximate encode and decode times for RS code
> on common hardware platforms.
>
>
>
>
> Regards,
> Debarshi Kumar Sanyal
> KIIT University, Bhubaneswar, India
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