Message concatenation

What is message concatenation?

Concatenated SMS messages allow you to send messages longer than 160 characters. If the message is shorter than or equal to 160 characters, it will be sent as a standard SMS message. However, if the message is longer than 160 characters, it is automatically split into several shorter messages, which are transmitted separately to the recipient, which are then collected by the recipient's phone and recombined into the original message sent. For trouble-free delivery, additional information called UDH (User Data Header) is added to each individual SMS message, which, among other things, indicates which part of the message is sent (eg Part 1 of 2). As a result, the total limit of the SMS message is reduced to 153 characters per part, as 7 characters are used up by these invisible headers and footers.

What are the character limits for concatenated SMS?

The following table shows the total number of characters available for the content of a concatenated SMS message, depending on the alphabet and character set used:

Number of SMSMaximum GSM charactersMaximum Unicode characters
1 simple SMS16070
2 concatenated SMS306 (153+153)134 (67+67)
3 concatenated SMS459 (153+153+153)201 (67+67+67)
4 concatenated SMS612 (153+153+153+153)268 (67+67+67+67)
x concatenated SMS? (x*153)? (x*67)

In general, telephone companies count individual concatenated SMS messages separately, even if they are eventually combined into one message by telephone. This means that a message containing 180 characters is charged as 2 SMS messages, even though the sender / recipient will only see one message.

Note: In theory it is possible to utilize 255 messages (39,015 characters) for a concatenated SMS. However, 3 SMS (or 459 characters), is generally considered to be the longest length message that will be displayed on the majority of mobile handsets. For this reason, we do not recommend sending SMS messages longer than 3 parts.

What is the basic character set used by the SMS service?

The basic character set is called GSM 7 bit default alphabet. The character set contains 3 control characters: Line feed, Carriage return and Escape. The Escape character is used to access theBasic Character Set Extension characters - one character per Escape is taken from these alternate characters.

Basic Character Set:

ABCDEFGH
IJKLMNOP
QRSTUVWX
YZabcdef
ghijklmn
opqrstuv
wxyz0123
456789ÄÖ
ÑÜäöñüà¿
§¡:;<>=?
!"#¤%&'(
)*+,.-/_
ÉéèùìòÇØ
øÅåÆæ@£$
¥ΔΦΓΛΩΠΨ
ΣΘΞßLFESCSP
  • LF is a Line Feed control (new line)
  • ESC is an Escape to extension table (maps to NBSP)
  • SP is a Space character

Basic Character Set Extension:

|^€{}[]~\

It is important (especially when a message is to be segmented using concatenated SMS mechanism) that characters from the Basic Character Set table cost one character in the message text, characters from the Basic Character Set Extension table cost two characters (by prepending escape character ESC (0x1B)).

Example:

7-bit character set

  • 100€ - 5 characters out of 160

Unicode character set

  • 100€ - 4 characters out of 70
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