Dear Marcus M.:

Actually my problem is:

y=useful information+x*h(channel)*cfo(carrier offset

due to the local oscillator between the interference and the

radar)+noise.

I want to turn y to

new_y=useful information+noise.

So I need know the channel(h) and the cfo exactly(I know the x in

advance while I don’t know the cfo and h.So I have to estimate them).The

root question I faced is the cfo estimated from the SCA isn’t enough.

Thank you so much. I will read the paper you mentioned.Maybe

helpful.Thanks.

Best regards,

zs

At 2015-06-24 17:08:16, “Marcus M.” [email protected] wrote:

Hi zs,

this reminds me very much of OFDM radar technologies, as your problem

boils down to finding a good estimator for the spectral properties of

your OFDM frame as well as the time it reached you.

I think you should have a look at chapter 3, “OFDM Radar Algorithms” of

[1]; you might find that considering the unknown timing being a result

of the time it took a OFDM signal to reach you (and hence an effect of

range) a useful approach. You can find some shorter information on the

accuracy of these estimates in [2].

The difference in the algorithms described in [1] and your problem is

that you don’t a priori know the transmitted signal – you’ll have to

figure that out by using something like S&C to receive and decode the

OFDM symbol prior to “clean” reconstruction; you could then use the

parameters (range == timing, doppler == frequency) that the radar

estimators give you to model the symbol like you received it, and

subtract it from your incoming signal. Of course, the mistakes you make

when decoding the incoming symbol will have an influence on the accuracy

of your estimates.

Best regards,

Marcus

[1] Braun, Martin. OFDM Radar Algorithms in Mobile Communication

Networks. Diss. Karlsruhe, Karlsruher Institut fr Technologie (KIT),

Diss., 2014, 2014;

http://nbn-resolving.org/urn:nbn:de:swb:90-388921

[2] Braun, Martin, Christian Sturm, and Friedrich Jondral. “On the

single-target accuracy of OFDM radar algorithms.” PIMRC. 2011.;

http://www.cel.kit.edu/download/PIMRC2011_BraunSchuSturmJondral.pdf

On 06/24/2015 10:29 AM, zs wrote:

Dear Marcus M.:

Thank you so much for your kindly reply.

The SCA is adequate for a correct demodulation of the signal while maybe

inadequate for estimate the precise frequency shift.I don’t have the

synchroniztion device.In my application,I need to reconstruct one

transmit signal in time domain,and remove it from the received

signal.For example,y=x1+x2,and I want to remove x2 from the baseband

recevied signal.

Now my idea is no only used the SCA algorithm mentioned in the new ofdm

example, but also use other similar finer carrier frequency estimation

algorithm.I want to combined the algorithms.So I ask the question in the

maillist.

Thank you so much.

Best regards,

zs

At 2015-06-24 15:54:30, “Marcus M.” [email protected] wrote:

Dear zs,

basically, Schmidl and Cox is a very good algorithm, because it can

achieve the same quality of synchronization with half of the

synchronization overhead compared to other approaches, or a better

performance with the same amount.

I must admit that from the top of my head, there’s probably not much

that’s better than S&C in a real world OFDM receiver, but I must admit

that I haven’t implemented many OFDM synchronizers myself.

However, you say

Now in my application,maybe this algorithm isn’t enough.

which means that you have a mathematical measure that’s not OK for S&C,

I guess. So in what way doesn’t S&C suffice? What is it about your

application that makes S&C insufficient or impossible to use?

Best regards,

Marcus

On 06/24/2015 09:00 AM, zs wrote:

Dear all:

Thank you in advance.

1.

I want to ask a question about the new ofdm example.And

I know the receiver have used the SCA(schmidl and cox algorithm)

algorithm.Now in my application,maybe this algorithm isn’t enough.And I

want to ask whether have other good frequency offset correction

algorithm which have been implemented.

2.What is the algorithm used by the old version of the

ofdm example?Thanks.

Best regards,

zs