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  1. #1
    Registered User
    Join Date
    Mar 2003
    Location
    Israel
    Posts
    14

    Problem in coding long SMS in 7 bit

    Why when coding long SMS in 7 bit the first octet shift left 1 time?

    See the following example:
    QRSTUVWXYZ coded in 7 bit concatenated will be
    11050003030303A2D229B56ABD62B35A

    Where
    11- udl
    05- udhl
    00- IE
    03- IEL
    03- reference number
    03 - total number of SMS
    03 - 3/3 sms
    A2D229B56ABD62B35A - UD
    A2 - 1010 0010 (the regular 7 bit coding moved left by one bit "0&quot and it's seems to be working in such way every time you send it. When trying to send the usual way it's not working (displays jibrish)

    The following example shows this phenomenon
    +CMT: ,28 ABCDEFG
    07917952140227F244038599F939F1206091018194000E05000303030182C221B1683C02

    +CMT: ,2 9 HIJKLMNOP
    07917952140227F240038599F939F120609101810500100500030303029049E592D9743EA1

    +CMT: ,30 QRSTUVWXYZ
    07917952140227F244038599F939F12060910181150011050003030303A2D229B56ABD62B35A

    By the way, found nothing about it in the specs. (03.40, 03.38)

  2. #2
    Super Contributor
    Join Date
    Mar 2003
    Posts
    509

    RE: Problem in coding long SMS in 7 bit

    Where
    11- udl
    05- udhl
    00- IE
    03- IEL
    03- reference number
    03 - total number of SMS
    03 - 3/3 sms
    Fill bits has to be added after header in order to get (7 bit)
    septet boyndary says GSM spesification 03.40 before starting the actual 7 bit data. This is to avoid shifting. 8 seven bit characters can be put in 7 octets. There are phones which do not understand headers and they can still make sence of the message after the header too this way. So the first A2 is the last octet of the 7 octet
    sequence and the coding should be according to that since the
    user data header takes only 6 octets from the beginning of normal
    user data.
    A2D229B56ABD62B35A - UD
    BR
    M, Forum Nokia

  3. #3
    Registered User
    Join Date
    Jun 2007
    Posts
    3

    Re: Problem in coding long SMS in 7 bit

    Hi could you further explain how did you arrive with "A2" as your fill bits in your example?

    Thank you so much.

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