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  1. #1
    Registered User
    Join Date
    Mar 2003
    Posts
    5

    Clarifications on User Data, User Data Binary and User Data Header

    This is my understanding on these three confusing parameters !!!

    1) User Data is used to send the default 7 bit GSM character text.
    The maximum size is 160.

    2) User Data Header is present ONLY if the User Data Binary is
    present.

    3) User Data binary is used to send the binary hex data. The maximum
    size of the User Data Binary is 140 - Size of User Data Header.

    Formatting of these parameters
    ------------------------------

    1) The SMS text can be directly added to the User Data if the size is
    less than 160 octets and requires 7 bit encoding. Since it is 7
    bit, the GSM to CIMD conversion of the escape sequences needs to
    be done.

    2) If 8 bit encoding is required then text is placed in the User Data
    Binary in the hex format !!! User Data header is also required.

    DOUBT: What is the format of the header now ?

    2) If the size is greater than 160, then the message needs to be
    segmented. To do this the User Data header has to be set and the
    data is placed in the User Data Binary. DCS needs to be set to F5
    to indicate 8 bit encoding.

    The formatting of the User Data Header is as follows

    06 - Length of the User Data Header
    00 - IEI ( concatenated short message)
    03 - IEDL
    01 - IE reference number
    05 - IE total number of messages
    01 - IE sequence number

    DOUBT : Does the IEI ( application port addressing scheme, 16 bit
    port address) need to be added ?

    The text is placed in the User Data Binary in the hex format !!!

  2. #2
    Regular Contributor
    Join Date
    Mar 2003
    Posts
    106

    RE: Clarifications on User Data, User Data Binary and User Data Header

    Hi,

    UDH can be used also without any User Data / User Data Binary (e.g. EMS uses this), and with normal User Data (see explanations below).

    Please find the clarifications below:

    Formatting the parameters:
    2) UDH is not necessarily needed. DCS indicates that it is a binary message.

    DOUBT : Does the IEI ( application port addressing scheme, 16 bit
    port address) need to be added ?

    Answer: Port addressing scheme is needed in cases that the mobile (destination) terminal needs to handle the incoming message in a special way. For example, if a ringing tone is sent, the phone needs to recognise it as a ringing tone and handle it accordingly, and not to display the characters on the screen. The same applies for example to picture messages. If no such intelligence is required from the destination (e.g. it is another application), then port addressing element is not needed.

    If the data to be sent is just text, it is not necessary to encode it to binary form. Just encode the header to indicate concatenation and insert the text (fitting length: 140 oct - size of UDH = remaining octets. Then "remaining octects * 8 / 7" indicates how many 7-bit characters may still be added) to the user data parameter (033). Then send the rest of the data in the next message (again with the UDH, of course). Even the dcs does not need to be present, since the data is normal text.

    Hope this clarifies,
    Antti/Forum Nokia

  3. #3
    Registered User
    Join Date
    Mar 2003
    Posts
    30
    Please give an example of a concatenated message. ie: show both messages.

    Thanks,

    Titch

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