Subject: RE: [manet] Interference in ad hoc network

From: "Manfredi, Albert E" <[email-masked]>
Date: Thu, 11 Jul 2002 17:46:57 -0400

Martin Haenggi wrote:

> > Within a single MANET, the nodes need to contend for channel access,
> 
> > and perhaps even reduce their transmitter power level (this 
> was discussed recently)
> 
> > so as not to interfere with each other. 
> 
> 
> One comment on that: if all nodes use the same power level, then the
> effect of the interference is completely independent of that 
> power level,
> since the signal-to-interference ratio remains constant.
> So, a (global) reduction of the power level does not help 
> alleviate the
> interference problem.

Hi Martin,

Hmmm. If the distance between hosts remains the same, receiver sensitivity remains the same, and the power level is reduced for all hosts in the MANET, then each host will detect fewer neighbors. This causes whatever routing algorithm is being used to have to create more hops between any random A and B host in the MANET, on average.

I guess I'm saying that the ratio that matters here is S/(N+I), not just S/I?

Bert

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From: "Kaixin Xu" <[email-masked]>
Date: Thu, 11 Jul 2002 15:24:59 -0700

Just want to say a complement point. I remember that Prof. Kumar at UIUC has
one paper saying that reducing the transmission power will reduce the
interference among nodes. However, to maintain the connectivity, there is a
minimal power level. Thus, from my point of view, reducing transmission
power is equivalent to reducing the node density. So I agree with Haenggi
that global reduction of the power level cannot help reducing interference.
It's just a optimization between the node density and transmission range.
What really matter are how fast the signal decays and the
transmitter-receiver distance. An interesting thing I have found is that
interference range is usually 1.7 times the transmitter-receiver distance.
Large interference range is harmful since RTS-CTS can only handle
interference nodes within transmission range.

Kaixin

----- Original Message -----
From: "Manfredi, Albert E" <[email-masked]>
To: "'Martin Haenggi'" <[email-masked]>
Cc: <[email-masked]>
Sent: Thursday, July 11, 2002 2:46 PM
Subject: RE: [manet] Interference in ad hoc network

> Hmmm. If the distance between hosts remains the same, receiver sensitivity
remains the same, and the power level is reduced for all hosts in the MANET,
then each host will detect fewer neighbors. This causes whatever routing
algorithm is being used to have to create more hops between any random A and
B host in the MANET, on average.

---

From: "Kaixin Xu" <[email-masked]>
Date: Thu, 11 Jul 2002 15:24:59 -0700

Kaixin