Presentation 11/08: Location Estimation in Ad-Hoc Networks with Directional Antennas
Su Kim
Chappell
Title: Location Estimation in Ad-Hoc Networks with Directional
Antennas
Published: Proceedings of the 25th IEEE International Conference on
Distributed Computing Systems (ICDCS'05), 2005
Please reply to this message in order to write your critique and
summary.
shayok.ch...@asu.edu
Hi all,
The paper "Location Estimation in Ad-Hoc Networks
with Directional Antennas", which Saleel presented in class yesterday,
provides three main schemes for localization. One is using a single
anchor and aligned antennas, the second is using aligned antennas with
two anchors and the third is the generalized technique for unaligned
antennas. In a mobile environment, the alignment of the antennas with
respect to one another is time dependent. (I am not talking about the
kids' network problem where each kid is equipped with 4 sensors, but a
general mobile environment). Thus, while applying the algorithm at a
particular point of time, which scheme can prove most effective? Will
it be safe to use the generalized unaligned antenna scheme as it is
more generic? I just want to have an idea.
Thank you,
Shayok.
Ayan Banerjee
I cant understand what does alignment mean in this context. What is meant by the term "aligned antennas"
Ayan
Shiraz Saleem
Hey Shayok and Ayan,
First let me answer Ayan's question cause its really important we understand what alignment means. Basically the localization here uses power received at two antennas and solves a set of equations to get the receiving angle estimates. "Aligned antennas" means orienting the transmitting anchor antenna and receiving antennas on sensor node in some pre-determined direction which helps in estimation.
Ayan Banerjee
Again I wanted to know that we are solving a set of 4 equations to get the location of a single target. So in case of multiple targets is this scheme computationally feasible?
Ayan
shayok.ch...@asu.edu
Hi,
Yes, this is exactly what I wanted to point out in my previous
post. In a mobile environment, it is never possible to guarantee that
he antennas will be aligned at all time during localization. That is
why I feel that the generic scheme of unaligned antennas will be more
justified.
- Shayok.
On Nov 10, 10:54 am, "Ayan Banerjee" <abane...@asu.edu> wrote:
> How can one ensure that the antennas will be aligned at all time during the
> target localization?
>
> Again I wanted to know that we are solving a set of 4 equations to get the
> location of a single target. So in case of multiple targets is this scheme
> computationally feasible?
>
> Ayan
>
jay.e...@asu.edu
orientation (with respect to true North, for instance). There are some
cases
where this can be done. (The paper mentioned motes that are physically
attached to a bridge as an example). So, if you can align the motes
when you
deploy them, you can use two of the three schemes mentioned in the
paper. If
you can not align the nodes with you deploy them, the paper offered
another
scheme using a base anchor that had a pair of directional antennas.
One question that came up in class is how the authors defined "%
error". As
near as I can tell, they took the distance between the estimated
position
and the actual position of the target node, and divided by the
distance from
the anchor node to the actual position of the target node. So, if the
target
node is actually 100m from the anchor, and the estimated position is
105m,
the error is 5%.
Hope this helps!
Jay
jay.e...@asu.edu
Antennas" by Malhotra et al
Critique by: Jay Elston
Critique of paper
Summary
This paper presented analysis, experiments and simulation of the
effectiveness of using directional antenna to determine a mobile
node's position.
The paper analyzed four configurations of directional antenna use.
1. Aligned Nodes
Anchor(s): Single anchor node using a single directional antenna, Node
is aligned
Target: Two directional antenna, Target is aligned with anchor.
2. Omni-directional
Anchor(s): Single anchor node transmitting with Omni-directional
dipole antennas
Target: Two directional antenna, Target's alignment is known.
3. Unaligned Nodes
Anchor(s): Dual directional antennas, Anchor's alignment is known.
Target: Two directional antenna, Target is unaligned.
4. Dual anchor Nodes
Anchor(s): Two anchor nodes, each with Directional antenna, Anchor's
alignment is known.
Target: Single directional antenna, Target's alignment is known.
Key Contributions
The combination of analysis, simulation and actual experimentation
using motes is unique.
Analysis & Results
The research determined that it is possible to obtain location
information using directional antennas. There are some situations
where the positional information is not very accurate, especially if
the target node is at certain angles from the anchor node. Accuracy
can be improved with the addition of anchor nodes.
Localization using directional antenna is more accurate than using
omni-directional antenna.
Conclusions
The use of directional antenna with a suitable number of anchor nodes
provides a means to implement a localization scheme for an ad hoc
network. The data in this paper can be used to help engineer a
solution. For instance - if you can deploy the target nodes with known
alignment, and you can keep your target nodes "in front" (in a field
that is between 30 and 60 degrees) of an anchor node, you can get
positional estimates with a distance that is within +/- 20% error
(from the anchor node). If you cannot guarantee the alignment of your
nodes, you should use the scheme where the anchor nodes transmit with
a pair of directional antenna. If you cannot keep your target nodes
"in front" of an anchor node, or you need additional accuracy, you
will need additional anchor nodes.
On Nov 6, 1:13 pm, Su Kim <sujin...@gmail.com> wrote:
ejs...@gmail.com
The problem of antenna alignment doesnt arise at all, that is what I
was stressing in the class. Since a directional antenna is going to be
there in every direction, It is always goin to receive the power.
We cannot say about the feasibility computationally. because we do not
know what other methods do to get the location. Also its good here
that only two anchor node can give a pretty close estimation of
location. So in a way we can say there is a tradeoff for the number of
anchor nodes to get the location to compution.
Saleel
On Nov 12, 1:33 pm, shayok.chakrabo...@asu.edu wrote:
> > > Shiraz- Hide quoted text -
>
> - Show quoted text -