Concatenated SMS

A concatenated SMS is a long message split into several SMS that the phone reassembles, each segment carrying only 153 characters in GSM-7.

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In brief

A concatenated SMS is a long message split into several SMS that the phone reassembles, each segment carrying only 153 characters in GSM-7.

Going deeper

Beyond 160 characters, the text is split into segments dispatched one by one, then reassembled on arrival. The recipient sees only one message, whereas the network conveyed several.

Each segment must fit a reassembly header that eats into space: the usable capacity falls to 153 characters per segment in GSM-7, and to 67 in UCS-2. Staying under 160 characters therefore remains the surest way to go off in a single SMS, short and clear.

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GSM-7 alphabetGSM-7 is the 7-bit character set used by default for SMS: it opens up 160 characters per message but leaves out some accented letters.UCS-2UCS-2 is the 16-bit encoding triggered as soon as an SMS contains a character foreign to GSM-7: capacity then drops to 70 characters per message.

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