[USRP-users] Gen2 reader

mahran nedal mahran2010sawya at hotmail.com
Thu Dec 4 12:40:59 EST 2014

Thank you for reply Marcus . yes between transmissions the carrier wave dropped or in every cycle . 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). 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 . I success to read one tag per cycle ,but until now i cant let the carrier wave continuous all the time . 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 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.Hope to hear from you as soon as Thanks,
Eng.Mahran jazi

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


    Could you please explain in more detail how you transit your signals
    (including the carrier)?


    Best regards,



    On 12/03/2014 06:51 PM, mahran nedal
      via USRP-users wrote:


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 .

Eng. jazi




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