[Discuss-gnuradio] How to confirm the GPS data captured from USRP N210 (L1 IF Signal)

[Eddie Sun]

Hi all,

I would like to ask a similar question as the link below

the link

I'm using GNU Radio-companion v3.4.0git-130-g207a2ae7 running on ubuntu 10.04 with a USRP N210 and DBSRX2 daughter board.
With some help from the list and take the document "SDR_Final_Report" as reference and do some modify, i draw a simple flow graph to get the L1 IF Signal and store into a data file,

UHD: usrp source -----> File Sink

where usrp source coefficient is as below 

The center frequency is 1575.42MHz for L1 signal
The sample rate is 4M Sps, Gain is 40 dB, Bandwidth is 2M Hz, and Output type is short vector(dark yellow)
The file sink input type is short with Vector length 2.

My problem is that i'm not sure if this is right for capturing the L1.
I used the software provide by the document SDR_Final_Report to up-convert short type to int8, and then used the Matlab code provide by the book "A software-defined GPS and Galileo receiver: a single-frequency approach" to do acquisition. 

After the acquisition, i still can't get the right result and PRN code. Is there anyone has some experience about this?
Or it's just my flow graph is wrong, or have a wrong parameter?

Or someone have other method can help to confirm if the data captured is correct or not? I really need some help or advice.

Thanks,
Eddie