Subject: [manet] AODV Collision Avoidance

From: "Schwentner, Jeffrey" <[email-masked]>
Date: Wed, 04 Feb 2004 16:59:17 -0500

I am working on a project which requires a very low-level implementation of an Ad-Hoc routing mechanism.  I found the AODV concept to be quite interesting, and had a question regarding the transmission of packets.
 
Consider the case when a node transmits a RREQ to it's neighbors.  When the neighbors receive the packet and prepare to send it on to their neighbors collisions might occur if they transmit at the same time.  Has there been any thought in the group to incorporating some kind of delay scheme to avoid simultaneous transmission following packet reception?  My implementation requires the use of a half-duplex RF transceiver, which is why I cannot detect collisions during transmission!

Any suggestions would be greatly appreciated,

Jeff Schwentner
> Lockheed Martin Simulation, Training & Support
email: [email-masked]

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From: "Philippe Jacquet" <[email-masked]>
Date: Thu, 5 Feb 2004 16:31:18 +0100

Hi, Jeff,

If the MAC layer provides its service in "best effort" (like with CSMA-CA),
it is preferable not to stress the link layer. Why not you use a random time
jitter before retransmission? Tests show  significant reduction in collision
rate when flooding are too frequent. There is no need to implement it at low
level. We have specified a time jitter in OLSR RFC, but there are many other
equivalent way and I don't see any problem to adapt them to AODV
implementation.

Best regards,
Philippe
----- Original Message -----
From: Schwentner, Jeffrey <[email-masked]>
To: <[email-masked]>
Sent: Wednesday, February 04, 2004 10:59 PM
Subject: [manet] AODV Collision Avoidance

> I am working on a project which requires a very low-level implementation
of an Ad-Hoc routing mechanism.  I found the AODV concept to be quite
interesting, and had a question regarding the transmission of packets.
>
> Consider the case when a node transmits a RREQ to it's neighbors.  When
the neighbors receive the packet and prepare to send it on to their
neighbors collisions might occur if they transmit at the same time.  Has
there been any thought in the group to incorporating some kind of delay
scheme to avoid simultaneous transmission following packet reception?  My
implementation requires the use of a half-duplex RF transceiver, which is
why I cannot detect collisions during transmission!