Max chars at SMS

Archived from groups: alt.cellular.gsm (More info?)

On 4 Jul 2004 19:26:49 -0700, sunnyshin@mtis.co.kr (sunny) wrote:

>160 7-bit characters or --> what about this?
>140 8-bit bytes of data or --> Max is 160 char?
>70 UCS2 coded characters --> Maybe 80 char?
>
>Can I send a more than 160 chars with 7-bit presentation?
>
>My colleague asked me about this.
>
>SMS can transfer upto 160bytes actually upto 170 chars can transfer.
>
>Is this right or wrong?
>
>I really wonder and confused..
>
>Sunny Shin.

Not as a single message. However most operators and most current
phones have the ability to string the 160 character messages together,
so what appears to be a single message to both the send and the
recipient, are in in fact be sent in multiple pieces. I believe this
is called Extended SMS, and fairly large messages can be sent this
way, although it may get expensive to do so if the message gets large
enough..

Archived from groups: alt.cellular.gsm (More info?)

"sunny" wrote:

> 160 7-bit characters or --> what about this?
> 140 8-bit bytes of data or --> Max is 160 char?
> 70 UCS2 coded characters --> Maybe 80 char?
>
> Can I send a more than 160 chars with 7-bit presentation?
>
> My colleague asked me about this.
>
> SMS can transfer upto 160bytes actually upto 170 chars can
> transfer.
>
> Is this right or wrong?
>
> I really wonder and confused..

As I mentioned in my earlier reply, there are 140 octets (bytes)
available in the user data area of an SMS. Unless there's
something special about that SMS, all 140 octets are available
for text (as 140 8-bit, or 160 7-bit, or 70 16-bit UCS2
characters). The message header's DCS setting specifies the
alphabet used (GSM 03.38).

But you asked about packing more than this into an SMS, and it's
now occurred to me that you might be thinking about the SMS
compression algorithm specified in GSM 03.42. As far as I know,
no handset manufacturer implements this, but I can see no reason
why a pair of computer-controlled GSM devices shouldn't be able
to pass such messages. It's not something I've tried myself.

For handset manufacturers, SMS compression is a can of worms.
The receiving handset is required by GSM 03.40 to store the
received message without tampering (in its original received
format). Optionally, the handset could uncompress and display
the message, but for practical reasons that may necessitate
reconstituting it as 2 concatenated (multi-part) messages,
correctly numbered.

On a casual reading, concatenated and compressed SMSs seem to
make different use of the first octet of the SMS user data area,
making complying compressed multi-part OTA messages impossible.

The compression uses Huffman Coding, so no generalization can be
made about how many characters can be put into a single SMS with
this mechanism.

John