[e2e] Regarding use of Reed-Solomon code in wireless networks

[Khaled Elsayed]

If it is performed using dedicated hardware, e.g. an FPGA, then of course
it can be done.


On Wed, May 6, 2015 at 3:02 PM, Debarshi Sanyal <debarshisanyal at gmail.com>
wrote:

> Hi Detlef, Khaled,
>
> Thanks for sharing your views.
>
> For the detection mechanism to work, retransmission must be explicitly
> switched off (as retransmitting same nonce gives advantage to the wormhole
> attacker).
>
> One way to avoid actually measuring the delay is to stipulate that the
> response nonce from the receiver must come back after a SIFS delay as it
> happens for any ACK frame in IEEE 802.11. This is possible if minimal
> processing is involved at the receiver node.
>
> If the response doesn't come back after SIFS, the receiver is probably far
> away and is likely to be connected by a wormhole to this sender. That way,
> we should be able to flag at least long wormholes.
>
> Do you think the above heuristic will work in real networks?
>
> Now if the nonces are encoded with RS code, is it still possible for the
> receiver to decode the nonce, process it, encode it back with RS code and
> transmit it after a SIFS delay from the time of reception?
>
> Thank you in advance for your valuable comments.
>
>
>
>
> Regards,
> Debarshi Kumar Sanyal
> KIIT University, Bhubaneswar
>
>
>
> On 6 May 2015 at 17:47, Khaled Elsayed <kelsayed at gmail.com> wrote:
>
>> Yes, it is usually a good idea to use RS encoding to combat channel
>> problems.
>> The time taken usually is function of the RS code word length and the
>> parity bits.
>> Usually it is very fast compared to other blocks like Viterbi decoder etc
>> if you are talking about lower layers where Viterbi is common.
>>
>> On Wed, May 6, 2015 at 8:14 AM, Debarshi Sanyal <debarshisanyal at gmail.com
>> > wrote:
>>
>>> 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
>>> nonce
>>> 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?
>>>
>>> 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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>>>
>>
>>
>