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Title
What are concatenated messages?
A concatenated short message service overcomes the limit on the number of characters that can be sent in a single SMS text message transmission (usually 160 characters).
With this method, the sending device divides the long message into smaller ones and merges them at the receiving end, charging each message as a single SMS message. The complete message appears to the receiving user as a single long text message (a concatenated SMS message). On networks that do not support concatenated SMS, each smaller message is delivered as an individual SMS text message.
Concatenated message character count is reduced by seven characters per message. Messages over 160 characters are reduced to 153 characters, while messages outside the GSM-7-character set (i.e., Unicode) are reduced from 70 to 67 characters.
How do you send a concatenated message?
Sending a concatenated message is no different from sending a message shorter than 160 characters. The mobile network splits the text for transmission and combines it back on the receiver’s mobile phone.
The recipient won’t notice anything out of the ordinary has happened.
Delivery reports for concatenated messages
Most mobile networks provide only one delivery report for the entire concatenated message, not for each individual segment. This means you’ll receive confirmation when the whole message has been successfully delivered to the recipient’s phone, but you won’t get separate notifications for each part.
Here’s why this is the case:
- Simplified tracking: It simplifies the tracking process for both the sender and the network. Imagine receiving multiple delivery reports for a single message – it could get confusing!
- Resource efficiency: Generating individual delivery reports for each segment would consume more network resources and potentially cause delays.
- Focus on overall delivery: The primary concern is whether the entire message was delivered successfully, not the status of individual parts.
However, some carriers might handle delivery reports differently. While the single delivery report is the most common approach, there might be exceptions.
How do concatenated messages work for different languages?
Concatenated messages work pretty much the same way across different languages, but there’s a key difference to keep in mind: character limits.
Character limits and encoding
- GSM-7 encoding: For languages that use the standard Latin alphabet (like English, French, and Spanish), each character typically uses 7 bits of data. This allows for a maximum of 160 characters per SMS segment.
- Unicode encoding: For languages with characters outside the standard Latin alphabet (like Chinese, Japanese, Arabic), Unicode encoding is used. This uses 16 bits per character, reducing the character limit per segment to 70 characters.
So, a message in English will be split into 160-character segments, while a message in Chinese will be divided into 70-character segments. Each segment still includes headers with information about the total number of parts and their order. The recipient’s phone uses these headers to reassemble the complete message, regardless of the language.
GSM encoding
- 1 standard SMS message = up to 160 characters
- 2 concatenated SMS messages = up to 306 characters
- 3 concatenated SMS messages = up to 459 characters
- 4 concatenated SMS messages = up to 612 characters
- 5 concatenated SMS messages = up to 765 characters
- (153 x number of individual concatenated SMS messages)
UTF-16 encoding (including special characters)
- 1 standard SMS message = up to 70 characters
- 2 concatenated SMS messages = up to 134 characters
- 3 concatenated SMS messages = up to 201 characters
- 4 concatenated SMS messages = up to 268 characters
- 5 concatenated SMS messages = up to 335 characters
- (67 x number of individual concatenated SMS messages)
Example of a concatenated SMS message
Example of a concatenated message
This image shows how a long SMS message is split and delivered to the recipient using concatenation.
- Ana is sending a long birthday invitation to Stefy. The message exceeds the typical 160-character limit of a single SMS.
- Ana’s phone automatically splits the message into two segments to comply with the character limit. Each segment includes a hidden header that tells the recipient’s phone how to reassemble the message. (right image)
- Stefy receives the two segments. Notice that each segment is within the character limit (158 characters and 70 characters, respectively).
- Stefy’s phone uses the information in the headers to put the two segments back together in the correct order.
- Stefy sees the complete message as intended without indicating that it was sent in multiple parts. (left image)
Key takeaway
The image illustrates how concatenated SMS messages allow for sending longer messages without compromising the user experience. The splitting and reassembly happen behind the scenes, ensuring the recipient receives a cohesive message.
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