Subject: RE: [manet] RE: [manet] IP addresses in MANET

From: "Mullen, John P. (Contractor)" <[email-masked]>
Date: Mon, 1 Jul 2002 09:20:41 -0600

Hi Bert,
 
It all turns on the density of your hosts and the patterns of
communications.  If you have a very large number of hosts in a rather small
geographical area, you will have increased contention for the RF channel.
By reducing power, you reduce the potential for interference among hosts
attempting unrelated communications on the same channel, but in
significantly different geographical locations.  If, on the other hand,
those conversations are of interest to all nodes, then reducing power will
increase the number of hops and channel utilization.  
 
For example, suppose your MANET consists of clusters of hosts that are about
1 km apart.  However, within a cluster, each node is within a few meters of
at least one other node.  When communications is within a cluster, it would
be prudent, to limit transmit power to that level necessary to carry out
communications within that cluster, but not high enough to cause
interference between clusters.  On the other hand, if you need to
communicate from one cluster to another, a higher power level would be
needed.
 
Also, if we agree that the MANET hosts are likely to be portable
battery-powered units, then managing transmitter power is also important
from the perspective of conserving network resources.  
 
I would say that the ability to change transmitter power has potential for
more efficient MANET management, but its success will turn on the ability of
the protocol to detect situations in which the different power levels are
appropriate.
 
John Mullen

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]]
Sent: Monday, July 01, 2002 8:18 AM
To: '??'
Cc: [email-masked]
Subject: RE: [manet] RE: [manet] IP addresses in MANET

Some miscellaneous rambling:
 
Decreasing power is useful to decrease the size of cells, to make more
efficient use of RF spectrum. In a system with base stations or access
points, the advantages seem obvious. The wired infrastructure will have to
be upgraded for a greater traffic load, but the individual wireless cells
will support the same number of hosts in a smaller area, resulting in
greater density of mobile hosts.
 
In an ad-hoc network, the advantage doesn't seem so obvious (to me). Since
ad-hoc networks depend on mobile hosts for all their intra-MANET routing,
decreasing power means increasing the number of hops required, which means
that there will be more choke points in the network and more hosts involved
in the average data path. I suppose that if one introduces faster mobile
hosts while reducing the power, same as one had to upgrade the wired
infrastructure in the cell-based network with base stations, then maybe I
can understand how you'd expect better performance.
 
Bert

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
Sent: Monday, July 01, 2002 3:52 AM
To: [email-masked]
Cc: [email-masked]; [email-masked]
Subject: [manet] RE: [manet] IP addresses in MANET

Hello Scott:
As David Young says, Using power control to increase MANET performance is an
active research area in MANET. It sure will increase MANET?ˉs throughput.
However, firstly, because of practical reason, transmitting power can not be
decreasing without limit; secondly, when the transmitting power is low
enough, it means that the talking area or clustering area is very small, In
such network, the mobility of nodes will become a big problem:) 
Practically speaking, if MANET can serve more than 10000 nodes freely, I
think it is enough for real implementation. I see no case which needs more
nodes than that:)

Hai Wang

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From: David Young <[email-masked]>
Date: Mon, 1 Jul 2002 13:26:43 -0500

In some research, a host transmits a beacon at each TX power level and
listens for beacon-replies to discover its neighbors. Then the host
labels each neighbor's route with the least TX power level necessary to
reach that neighbor.  Packets destined for a neighbor are transmitted
with the power level labeling the neighbor's route.

If a host discovers neighbors with beacons independently of discovering
routes with an ad hoc routing protocol, then sometimes a neighbor will
have two routes, one discovered by the beacon and one discovered by the
routing protocol. Then the host will have a choice between shouting at a
far away neighbor, or whispering to a nearer neighbor who will whisper
to the far away neighbor. A strategy for choosing between one "loud"
hop and several quiet ones could be quite complex, it seems. Suppose
you tried to estimate and minimize the product of a packet's on-air time
and the area silenced by its (re)transmission?

Dave

On Mon, Jul 01, 2002 at 09:20:41AM -0600, Mullen, John P. (Contractor) wrote:
> active research area in MANET. It sure will increase MANET?¡¥s throughput.

-- 
David Young             OJC Technologies
[email-masked]     Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933

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From: David Young <[email-masked]>
Date: Mon, 1 Jul 2002 13:26:43 -0500

Dave

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From: Miguel Sanchez <[email-masked]>
Date: Tue, 02 Jul 2002 00:20:39 +0200

Hi Dave,

You wrote:

>...  a choice between shouting at a
As a rule of thumb if you look at the tx power only, it is more energy 
efficient to whisper the packet twice than to transmit it loud once (due 
to the power law on the atenuation). However if you  take into account 
that receiving is not coming for free either, and if you assume that all 
neighbor nodes will receive a packet before they can check if it is 
addressed  to them or not (and therefore they will draw reception 
energy) then whispering twice could be a worse choice than one loud 
transmission. Of course this analysis may be interesting when you are 
worried about network survivability (i.e. low power sensor networks).

What it is more, the numbers of this observation will change a lot 
depending on the nodal density about these three involved nodes (i.e. 
sender, reciver and forwarder).

I just wanted to add this thought to the discussion.

Miguel Sanchez
Universidad Politecnica de Valencia, Spain

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From: Miguel Sanchez <[email-masked]>
Date: Tue, 02 Jul 2002 00:20:39 +0200

Hi Dave,

Miguel Sanchez