> Hi!
>
> I have performed some propagation channel measurements in frequency
> domain i.e. I stored the measurement data as complex transfer
> function. I know I can obtain the channel impulse response by taking
> the IFFT.
>
> My question is, instead of taking IFFT. Can I employ other techniques
> (usually called super-resolution techniques in radar/wireless
> communications) such as ESPRIT, EM, SAGE, etc. algorithms to estimate
> the number of multipaths, their amplitudes and their time-of-arrivals?
>
Via angle SR techniques? Yes. However, recall that multipath tends to be
correlated highly with the direct signal (i.e. with the signal backscattered
from your "target" which also produces the multipath), whilst SR usually
requires that the (multiple) sources are uncorrelated.
> I have tried to search for papers but I realized that most of them
> include angle-of-arrivals estimation. For my case, I performed my
> measurements with single antenna system. So, no angular information
> can be estimated. Can I still employ these techqiues?
>
When you say single antenna, I presume you mean a single dish antenna rather
than an array of some form (e.g. phased array). Angle SR tends to be
performed with array antennas, but you can still do it with a single dish
provided it is step-scanning. I can provide a reference if it's relevant.
Ta,
Carlos
Reply by Rune Allnor●March 30, 20042004-03-30
lindah74uk@yahoo.co.uk (Linda) wrote in message news:<124fd8f7.0403300323.1cf4ee46@posting.google.com>...
> Hi!
>
> I have performed some propagation channel measurements in frequency
> domain i.e. I stored the measurement data as complex transfer
> function. I know I can obtain the channel impulse response by taking
> the IFFT.
>
> My question is, instead of taking IFFT. Can I employ other techniques
> (usually called super-resolution techniques in radar/wireless
> communications) such as ESPRIT, EM, SAGE, etc. algorithms to estimate
> the number of multipaths, their amplitudes and their time-of-arrivals?
> I have tried to search for papers but I realized that most of them
> include angle-of-arrivals estimation. For my case, I performed my
> measurements with single antenna system. So, no angular information
> can be estimated. Can I still employ these techqiues?
While I do not know very much about telecom, I do know a bit about
the types of techniques you consider.
It is, generally, not possible to give a definite answer to your
question. Everything depends on the application. I have seen some
papers where people propose to use MUSIC to reconstruct a time-domain
reflection series of a radar echo, thereby presenting a high resolution
image of the target. See the paper
Kyung-Tae Kim, Dong-Kyu Seo, Hyo-Tae Kim: Efficient radar target
recognition using the MUSIC algorithm and invariant features
IEEE Transactions on Antennas and Propagation, Vol. 50(3),
March 2002, Pages:325 - 337
for an example. I don't know how or why MUSIC works in the radar
problem, but I do know that usually, you need some very specific
conditions to be met for the method to work. I have written several
comments about these things here on comp.dsp in the past, so if
you google for something like
author:allnor@tele.ntnu.no group:comp.dsp MUSIC
at www.groups.google.com, you might find some posts that elaborate
on these things.
The basic message is that there is no easy way to answer your question.
These methods are highly sophisticated, and need to be perfectly matched
to the problem to yield meaningful results. This means that only
somebody who understand both the methods and the problem can provide
useful advice.
Rune
Reply by Julius Kusuma●March 30, 20042004-03-30
On Tue, 30 Mar 2004, Linda wrote:
> Hi!
>
> I have performed some propagation channel measurements in frequency
> domain i.e. I stored the measurement data as complex transfer
> function. I know I can obtain the channel impulse response by taking
> the IFFT.
>
> My question is, instead of taking IFFT. Can I employ other techniques
> (usually called super-resolution techniques in radar/wireless
> communications) such as ESPRIT, EM, SAGE, etc. algorithms to estimate
> the number of multipaths, their amplitudes and their time-of-arrivals?
> I have tried to search for papers but I realized that most of them
> include angle-of-arrivals estimation. For my case, I performed my
> measurements with single antenna system. So, no angular information
> can be estimated. Can I still employ these techqiues?
>
> Thanks.
>
> Linda
>
linda, most of the techniques that you mentioned are parametric frequency
estimators, meaning that you have to know in advance how many components
exist in your signal. there are many ways to do this; for example you
can compute the sample covariance matrix of your signal, and compute the
singular / eigen values. based on these, you can estimate how many
components you have in your signal.
for example, if you compute a 5x5 covariance matrix and find 3 large
eigenvalues and 2 small ones, you can estimate that you have 3 frequency
components, assuming that you have high SNR. this is the basic idea of
subspace methods.
angle-of-arrivals are estimated by using an antenna array; you compute
the _spatial_ covariance matrix, and the angles of arrival correspond to
frequency components. in contrast, what i said in the previous paragraphs
assume that you compute the sample covariance matrix in the _time_ domain.
i think you're confusing things a bit here. i have an introductory
document that explains some of this on my website, maybe i should update
it at some point.
a good reference to frequency estimation would be the statistical signal
processing book by munson and hayes. they come with handy matlab codes,
too.
julius
--
The most rigorous proofs will be shown by vigorous handwaving.
http://www.mit.edu/~kusuma
opinion of author is not necessarily of the institute
Reply by Linda●March 30, 20042004-03-30
Hi!
I have performed some propagation channel measurements in frequency
domain i.e. I stored the measurement data as complex transfer
function. I know I can obtain the channel impulse response by taking
the IFFT.
My question is, instead of taking IFFT. Can I employ other techniques
(usually called super-resolution techniques in radar/wireless
communications) such as ESPRIT, EM, SAGE, etc. algorithms to estimate
the number of multipaths, their amplitudes and their time-of-arrivals?
I have tried to search for papers but I realized that most of them
include angle-of-arrivals estimation. For my case, I performed my
measurements with single antenna system. So, no angular information
can be estimated. Can I still employ these techqiues?
Thanks.
Linda