[USRP-users] Gen2 reader

Marcus Müller marcus.mueller at ettus.com
Fri Dec 5 18:08:48 EST 2014


Hello Mahran,

I really don't make much progress understanding you, I'm afraid :( 
Could you please directly answer the questions I inserted into your email below?


On December 5, 2014 7:37:52 PM CET, mahran nedal <mahran2010sawya at hotmail.com> wrote:
>Hello Marcus,
>Thank you for your reply and attention . I let my reader to send the
>carrier wave continuously, But when i plot the received signal i see
How do you plot the signal?
>that the carrier wave after each cycle dropped ,Really i dont know why
>is that ? 

I don't know either. When you record the samples you send to the USRP for transmission to a file simultaneously, and analyze them, do they show the same drop out?

> I change the time that when the carrier should power down 
>to check what happen but with no change on the received signal. 

Why do you power down the carrier?

As far as I could understand the running diagrams you referred to, there was no period where the carrier has to be powered down.

> I
>modified the code for buttner that work on usrp 1.the code very large
>and complicated to mention it. If you know please any one maybe work on
>this topic .

I'd assume no one else is working on the same standard, but there were projects concerned with reading rfid tags using USRPs before.

Best regards,
Marcus Müller 

>
>Thanks,
>
>
>
>> Date: Fri, 5 Dec 2014 11:49:15 +0100
>> From: marcus.mueller at ettus.com
>> To: mahran2010sawya at hotmail.com; usrp-users at lists.ettus.com
>> Subject: Re: [USRP-users] Gen2 reader
>> 
>> Hello Mahran,
>> 
>> I must admit that I had trouble understanding the complex problem
>you're
>> describing.
>> 
>> I'll go ahead and try to insert my questions into your mail, so that
>I
>> can get to a full understanding.
>> On 12/04/2014 06:40 PM, mahran nedal wrote:
>> > yes between transmissions the carrier wave dropped or in every
>cycle .
>> I assume that is correct by design?
>> > My implementation based on EPC Class-1 Generation-2 protocol please
>see http://www.gs1.org/gsmp/kc/epcglobal/uhfc1g2  V2.2 (page 26,42).
>> I assume you're referring to the v2.0 document -- there's only a
>> two-page v2.2 "fact sheet".
>> I must admit that I can't really justify reading a complex standards
>> document on worktime -- however, the timing diagram on page 42
>indicates
>> that the interrogator must continously send, so that is what your
>> application must ensure.
>> > The reader or interrogator send the signal which contains a Query
>,all the  communication parameters  includes inside the query  like
>preamble ,etc. the signal encoding by pulse interval encoding and
>modulated by ASK ,the tag receive the signal and back-scattering again
>to the reader ,through this time the carrier wave energize the tag for
>response .
>> Yes, I understand.
>> > I success to read one tag per cycle ,but until now i cant let the
>carrier wave continuous all the time .
>> Why?
>> >  What is happening that when the reader send a query to the tag ,
>the tag response its RN16 ,the reader Acknowledged it ,and the tag send
>the ID after that the carrier wave dropped 
>> why do you let the carrier wave drop? The timing diagram says
>"continous
>> wave", so from what I understand you must ensure that your
>interrogator
>> is always either sending data or a naked carrier.
>> 
>> From what I understand, you are implementing the interrogator, is
>that
>> correct?
>> 
>> > and start again with each transmission and this is a problem
>because  when i ran the anti- collision protocol which mean that i
>should send the number of slots through the query for many tags and
>every tag choose one slot and response back to the reader ,so i should
>see through the query for example 3 tag response before the new cycle
>start but i cant i see just one ,because the carrier wave dropped every
>cycle.
>> Sorry, this I did not understand.
>> > Hope to hear from you as soon as Thanks,
>> > Eng.Mahran jazi
>> Greetings,
>> Marcus
>> 
>> >
>> >
>> > Date: Wed, 3 Dec 2014 19:03:12 +0100
>> > To: usrp-users at lists.ettus.com
>> > Subject: Re: [USRP-users] Gen2 reader
>> > From: usrp-users at lists.ettus.com
>> >
>> >
>> >   
>> >     
>> >   
>> >   
>> >     Hello Mahran
>> >
>> >     
>> >
>> >     this is an interesting application.
>> >
>> >     
>> >
>> >     I'd like to understand what's going wrong here:
>> >
>> >     You say the USRP doesn't continously send a carrier wave. I
>assume
>> >     this is happening between your transmissions?
>> >
>> >     
>> >
>> >     The USRP will send any signal you want and will try to be as
>silent
>> >     as possible as long as you are not transmitting. If you want a
>> >     continous carrier, you will have to continously send samples
>> >     containing the appropriate signal. 
>> >
>> >     Since the N210 architecture is by principle full-duplex
>capable, as
>> >     are the RFX daughterboards, this should normally not be a
>problem,
>> >     unless crosstalk is problematic (e.g. it saturates your RX
>> >     amplifiers/mixers).
>> >
>> >     
>> >
>> >     Could you please explain in more detail how you transit your
>signals
>> >     (including the carrier)?
>> >
>> >     
>> >
>> >     Best regards,
>> >
>> >     Marcus
>> >
>> >     
>> >
>> >     On 12/03/2014 06:51 PM, mahran nedal
>> >       via USRP-users wrote:
>> >
>> >     
>> >     
>> >       Hi,
>> >
>> > Im working to implement gen 2 reader based on new generation of
>usrp n210 with RFX900 daughter board  to read the commercial tags. I
>success to read commercial tag . now i investigate to read many tags
>based on dynamic framed slotted aloaha , the main problem that the usrp
>cant continuously send the carrier wave through one cycle ,the carrier
>wave dropped and start again with each cycle so i cant sent many slots
>in each cycle because this problem . i debugging the software no
>problem . Is there any limitation on this hardware or daughter borad
>that cant support full-duplex 
>> >  
>> > Really i need help .
>> >
>> >
>> > Thanks,
>> > Eng. jazi
>> >  
>> >
>> >  		 	   		  
>> >
>> >       
>> >
>> >       
>> >       
>> >
>> >       _______________________________________________
>> > USRP-users mailing list
>> > USRP-users at lists.ettus.com
>> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>> >
>> >     
>> >     
>> >
>> >   
>> >
>> >
>> > _______________________________________________
>> > USRP-users mailing list
>> > USRP-users at lists.ettus.com
>> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>		 	   		  
>> 
> 		 	   		  

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