MUSIC and LMS together??

Started by scc November 7, 2007
Hello,

   sorry if I seem confused...but I'm actually confused...

     Could someone tell me if I need to implement a DoA stimation
algorithm (like MUSIC or ESPIRT) with an adaptative algorithm (like LMS)
on development of an intelligent beamforming system?? I mean, I don't know
the DoA of the signal so, how could I use only the LMS algorithm? Is there
a diference between using these algorithms together or using only one of
them?? I hace to choose an FPGA to do the implementation but I have ti
calculate the computational weight before choosing anything. I think that
now, after looking for understanding this methods, I understand them less
than the first day...


Thanks a lot!

On 7 Nov, 14:18, "scc" <sandracorr...@gmail.com> wrote:
> Hello, > > sorry if I seem confused...but I'm actually confused...
A very good start. Lots of people are confused without knowing it. They always end up in serious trouble.
> Could someone tell me if I need to implement a DoA stimation > algorithm (like MUSIC or ESPIRT) with an adaptative algorithm (like LMS) > on development of an intelligent beamforming system?? I mean, I don't know > the DoA of the signal so, how could I use only the LMS algorithm?
MUSIC and ESPRIT are designed for static problems (the DoA doesn't change over the course of the measurement) while adaptive methods allows for such change. Which one to choose depends on exactly how your target sourcve behaves. If it doesn't move a lot, use MUSIC or ESPRIT; if it dooes, use an adaptive method. Rune
>On 7 Nov, 14:18, "scc" <sandracorr...@gmail.com> wrote: >> Hello, >> >> sorry if I seem confused...but I'm actually confused... > >A very good start. Lots of people are confused without >knowing it. They always end up in serious trouble. > >> Could someone tell me if I need to implement a DoA stimation >> algorithm (like MUSIC or ESPIRT) with an adaptative algorithm (like
LMS)
>> on development of an intelligent beamforming system?? I mean, I don't
know
>> the DoA of the signal so, how could I use only the LMS algorithm? > >MUSIC and ESPRIT are designed for static problems (the DoA >doesn't change over the course of the measurement) while >adaptive methods allows for such change. Which one to choose >depends on exactly how your target sourcve behaves. If it doesn't >move a lot, use MUSIC or ESPRIT; if it dooes, use an adaptive >method. > >Rune > >
Thanks a lot Rune!! You don't know what you've done for me...So, since I'm looking for developing an adaptive beamforming system (with mobile sources) I should implement an adaptive algorithm like LMS...right? Thank for your answer. San
Hello,

    5 minutes after answer here I've found an article in which the author
writes:

   "A smart antenna system at the base station of a cellular mobile
system is depicted in Fig. 1. It consists of a uniform linear
antenna array for which the current amplitudes are adjusted
by a set of complex weights using an adaptive beamforming
algorithm. The adaptive beamforming algorithm optimizes
the array output beam pattern such that maximum radiated
power is produced in the directions of desired mobile users
and deep nulls are generated in the directions of undesired
signals representing co-channel interference from mobile users
in adjacent cells. Prior to adaptive beamforming, the directions
of users and interferes must be obtained using a direction-ofarrival
(DOA) estimation algorithm"

   After this, as I had seen in other documents, it talks about MUSIC and
LMS algorithms and specifies that LMS algorithm needs to know a reference
signal.

   At this point my doubts have come back...

The link to this document is: 

http://www.academypublisher.com/jcm/vol02/no04/jcm02047177.pdf


   That's why I said that now I'm more confused than I was when I wanted
to began this project...
On 7 Nov, 17:44, "scc" <sandracorr...@gmail.com> wrote:
> Hello, > > 5 minutes after answer here I've found an article in which the author > writes: > > "A smart antenna system at the base station of a cellular mobile > system is depicted in Fig. 1. It consists of a uniform linear > antenna array for which the current amplitudes are adjusted > by a set of complex weights using an adaptive beamforming > algorithm. The adaptive beamforming algorithm optimizes > the array output beam pattern such that maximum radiated > power is produced in the directions of desired mobile users > and deep nulls are generated in the directions of undesired > signals representing co-channel interference from mobile users > in adjacent cells. Prior to adaptive beamforming, the directions > of users and interferes must be obtained using a direction-ofarrival > (DOA) estimation algorithm" > > After this, as I had seen in other documents, it talks about MUSIC and > LMS algorithms and specifies that LMS algorithm needs to know a reference > signal.
I can't read the article you cite, so I don't know what it says. I would *guess* that they use MUSIC to obtain the DoA of the source, and then use the LMS to extract the actual signal. This is the sort of thing that might look good on paper and even generate some funding, if mentioned in an application. However, using MUSIC or ESPRIT in an unsupervised setting is a sure recipe for disaster. Your first task ought to be to research the literature and find out how many people have used MUSIC or ESPRIT successfully in "the wild." Not how many say they *will*; how many who have *actually* used these methods. The reason why there are so few (any at all?) is that both MUSIC and ESPRIT require that the antenna array is tailored to the signals they will measure. If you look closely at the equations, you will find that those sorts of methods require that the dimension of certain data covariance matrices are larger than the number of signals present. The rank of the covariance matrices depend in turn on the number of elements in the array. For an N-element ULA you need to *guarantee* that there will *never* be more than N/2-1 signals present. The whole system will go down if there are N/2 or more signals. (If you don't believe me, make sure to run simulations before you engage in any large design projevts.) I know of no unsupervised, unrestricted scenarions wher such *guarantees* can be given. So stick with LMS. Stay as far away from MUSIC and ESPRIT as you possibly can. Rune
>On 7 Nov, 17:44, "scc" <sandracorr...@gmail.com> wrote: >> Hello, >> >> 5 minutes after answer here I've found an article in which the
author
>> writes: >> >> "A smart antenna system at the base station of a cellular mobile >> system is depicted in Fig. 1. It consists of a uniform linear >> antenna array for which the current amplitudes are adjusted >> by a set of complex weights using an adaptive beamforming >> algorithm. The adaptive beamforming algorithm optimizes >> the array output beam pattern such that maximum radiated >> power is produced in the directions of desired mobile users >> and deep nulls are generated in the directions of undesired >> signals representing co-channel interference from mobile users >> in adjacent cells. Prior to adaptive beamforming, the directions >> of users and interferes must be obtained using a direction-ofarrival >> (DOA) estimation algorithm" >> >> After this, as I had seen in other documents, it talks about MUSIC
and
>> LMS algorithms and specifies that LMS algorithm needs to know a
reference
>> signal. > >I can't read the article you cite, so I don't know what >it says. I would *guess* that they use MUSIC to obtain >the DoA of the source, and then use the LMS to extract >the actual signal. This is the sort of thing that might >look good on paper and even generate some funding, if >mentioned in an application. > >However, using MUSIC or ESPRIT in an unsupervised setting >is a sure recipe for disaster. Your first task ought to >be to research the literature and find out how many >people have used MUSIC or ESPRIT successfully in "the >wild." Not how many say they *will*; how many who have >*actually* used these methods. > >The reason why there are so few (any at all?) is that >both MUSIC and ESPRIT require that the antenna array >is tailored to the signals they will measure. If you >look closely at the equations, you will find that those >sorts of methods require that the dimension of certain >data covariance matrices are larger than the number >of signals present. The rank of the covariance matrices >depend in turn on the number of elements in the array. > >For an N-element ULA you need to *guarantee* that there >will *never* be more than N/2-1 signals present. The whole >system will go down if there are N/2 or more signals. >(If you don't believe me, make sure to run simulations >before you engage in any large design projevts.)
I believe you, I had read it but I didn't think that the whole system whould gone down before now.
>So stick with LMS. Stay as far away from MUSIC and ESPRIT >as you possibly can.
I've understand but then, my problem is still here...Lms needs to know the desired signal or at least knowing it by a training sequence...I'm working with a WiMax Mobile System, an OFDMA system of 5ms frames. I don't have that training sequence and I don't have an spreading code as in the cose of a CDMA system. How should I calculate the error without a reference signal?? Thanks for your help. San
>>On 7 Nov, 17:44, "scc" <sandracorr...@gmail.com> wrote: >>> Hello, >>> >>> 5 minutes after answer here I've found an article in which the >author >>> writes: >>> >>> "A smart antenna system at the base station of a cellular mobile >>> system is depicted in Fig. 1. It consists of a uniform linear >>> antenna array for which the current amplitudes are adjusted >>> by a set of complex weights using an adaptive beamforming >>> algorithm. The adaptive beamforming algorithm optimizes >>> the array output beam pattern such that maximum radiated >>> power is produced in the directions of desired mobile users >>> and deep nulls are generated in the directions of undesired >>> signals representing co-channel interference from mobile users >>> in adjacent cells. Prior to adaptive beamforming, the directions >>> of users and interferes must be obtained using a direction-ofarrival >>> (DOA) estimation algorithm" >>> >>> After this, as I had seen in other documents, it talks about MUSIC >and >>> LMS algorithms and specifies that LMS algorithm needs to know a >reference >>> signal. >> >>I can't read the article you cite, so I don't know what >>it says. I would *guess* that they use MUSIC to obtain >>the DoA of the source, and then use the LMS to extract >>the actual signal. This is the sort of thing that might >>look good on paper and even generate some funding, if >>mentioned in an application. >> >>However, using MUSIC or ESPRIT in an unsupervised setting >>is a sure recipe for disaster. Your first task ought to >>be to research the literature and find out how many >>people have used MUSIC or ESPRIT successfully in "the >>wild." Not how many say they *will*; how many who have >>*actually* used these methods. >> >>The reason why there are so few (any at all?) is that >>both MUSIC and ESPRIT require that the antenna array >>is tailored to the signals they will measure. If you >>look closely at the equations, you will find that those >>sorts of methods require that the dimension of certain >>data covariance matrices are larger than the number >>of signals present. The rank of the covariance matrices >>depend in turn on the number of elements in the array. >> >>For an N-element ULA you need to *guarantee* that there >>will *never* be more than N/2-1 signals present. The whole >>system will go down if there are N/2 or more signals. >>(If you don't believe me, make sure to run simulations >>before you engage in any large design projevts.) > >I believe you, I had read it but I didn't think that the whole system >whould gone down before now. > >>So stick with LMS. Stay as far away from MUSIC and ESPRIT >>as you possibly can. > >I've understand but then, my problem is still here...Lms needs to know
the
>desired signal or at least knowing it by a training sequence...I'm
working
>with a WiMax Mobile System, an OFDMA system of 5ms frames. I don't have >that training sequence and I don't have an spreading code as in the cose >of a CDMA system. How should I calculate the error without a reference >signal?? > >Thanks for your help. > >San >
Could someone help me with my last question please?? Rune??