Subject: [manet] One Hop Delay in Manet

From: Abdalla Mahmoud <[email-masked]>
Date: Fri, 13 May 2005 03:45:57 +0300

Hello All,
            I just have a quick question. I know that in wireless
communications that if the distance between two nodes is either 1
meters or even like 100 meters, the same delay of a data packet
transfer applies, since it travels by the speed of light.

So my question is: what is the average  one-hop delay in Manets? In
other words, what is the average delay between two nodes within the
same transmission range.?

Your prompt reply or feedback will be appreciated,
A.M.

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From: Marcelo Carvalho <[email-masked]>
Date: Thu, 12 May 2005 18:48:58 -0700

Hi Abdalla,

    The average one-hop delay will essentially depend on the 
contention-level around the node. For an idea of the delay and jitter 
incurred in a saturated single-hop network using the IEEE 802.11 DCF, 
take a look at:

    M. M. Carvalho and J. J. Garcia-Luna-Aceves, "Delay Analysis of IEEE 
802.11 in Single-Hop Networks," Proc. IEEE ICNP'03, Atlanta, USA, Nov. 
4-7, 2003.

    For multihop ad hoc networks under saturation, take a look at:

    M. M. Carvalho and J. J. Garcia-Luna-Aceves, "A Scalable Model for 
Channel Access Protocols in Multihop Ad Hoc Networks," Proc. ACM 
MobiCom, Philadelphia, USA, Sep. 26 - Oct. 1, 2004.

    This last one provides results on throughput, but we also present 
the  formality to obtain the average delay per node, given the network 
topology and  PHY layer parameters.

    I hope that helps.
    Best Regards,

    Marcelo Carvalho.

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From: Philippe Jacquet <[email-masked]>
Date: Fri, 13 May 2005 11:00:45 +0200

Dear Abdalla,

Most of the delays are in MAC access contention and in store-forward. Of the
order of several ms with IEEE 802.11. Propagation delay at light speed on 100 m
is negligible. In RAWNET 2005 we have presented an evaluation of the packet one
hop delay distribution in IEEE 802.11 (see
http://www.rawnet.org/rawnet_jacquet.pdf ) and in particular we have focused on
the large deviation evaluation. It turns out that the large deviations are in
power law, and this makes routing decision based on delay a polynomial
algorithm, while in general such routing is NP-hard. 

BTW, here delay based routing is not finding the route which minimizes the
avarage delay (which is just Dijsktra), it is finding the route that minimizes
the overdelay ratio: i.e. minimizing P(delay>T) for a given deadline T
depending on the traffic flow (for example T is the time buffer for a video
stream). We also give some hints on how to implement this kind of routing over
OLSR. 

I hope this helps,

Best regards,
Philippe

-- 
Philippe Jacquet
Hipercom project team leader
INRIA
tel: +33 1 39 63 52 63
fax: +33 1 39 63 55 66

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