Subject: RE: [manet] Hiden- & exposed terminal problem in MANET

From: "Manfredi, Albert E" <[email-masked]>
Date: Fri, 20 Sep 2002 17:57:53 -0400

> -----Original Message-----
> From: Sumeeth Nagaraj [mailto:[email-masked]]
> 
> The idea of using multiple codes was to remove the RTS-CTS over head.
> RTS-CTS can cause congestion problems for a netowork with 
> high density of
> nodes.
> 
> You can give a look at the channel access scheme proposed by 
> Dr. Schlegel:
> Here they have a common  header spread with a identical  code 
> that uses the
> basic aloha scheme and the data is spread by a random 
> spreading code, that
> is sent to the destinatioin in the header.
> http://www2.elen.utah.edu/~schlegel/publications/KotSch01.pdf
> 
> and also, the MAC protocol proposed by Dr. Rabaey for the pico radio
> project(BWRC).

How intriguing. Seems like going to a cellular telephone CDMA-like protocol, to establish unique, signaled links between hosts. The difference being that the initial setup is done with an aloha protocol instead of having a base station keep things organized?

Bert
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---

From: Sumeeth Nagaraj <[email-masked]>
Date: Sat, 21 Sep 2002 17:40:34 -0600

Hello Bert,

I would think its considerably a different idea when compared to the
cellular systems and applying the idea of multiple codes to mobile ad-hoc
networks should also be considered?(your inputs please).

 Every node, has a header  which is spread by a known spreading code and the
data part is spread by the random code sent to the destination by the
source. This is done for each packet sent by the source and the random code
changes each time the source has some data packet to send which is not the
case in cellular systems.

The available bandwidth is pretty well utilized. The base station still
exists and they have not said anything to replace the base station as noted
by you.  Although the success, is in proper detection of the header, which
is spread using a common spreading code, I would think this should not be
that problem, the same scenario exists in sending the RTS, CTS , data packet
and also the ACK in IEEE 802.11. The loss of any of the control/data
packets, which is very likely to happen, for the Unicast packets, involves
starting the whole process of sending the RTS-CTS-Data and ACK again.
Guessing the states of other nodes in the network(locally), as noted by
Cesar, is one tough job unless the node timeouts and starts all over again.

Best Regards,
Sumeeth

"Anyone who has never made a mistake
      has never tried anything new" --Albert Einstein.

.
----- Original Message -----
From: "Manfredi, Albert E" <[email-masked]>
To: "'Sumeeth Nagaraj'" <[email-masked]>; <[email-masked]>
Sent: Friday, September 20, 2002 3:57 PM
Subject: RE: [manet] Hiden- & exposed terminal problem in MANET

> How intriguing. Seems like going to a cellular telephone CDMA-like
protocol, to establish unique, signaled links between hosts. The difference
being that the initial setup is done with an aloha protocol instead of
having a base station keep things organized?

---

From: Sumeeth Nagaraj <[email-masked]>
Date: Sat, 21 Sep 2002 17:40:34 -0600

Hello Bert,

Best Regards,
Sumeeth

.