Somebody often ask to me why SMS text messages are
limited to 160 characters for one message or one SMS. So I just share
with this articles to explain what I know. Even you can send SMS until
960 characters but they are just sent in 6 separated text messages.
Back to question why SMS text message limited to 160 characters. To
answer that question, we should have basic concept of SMS text message. We have to know about SMS Protocol Description UnitPDU ) which is way sending SMS text mode. SMS text message is sent by SMSC ( SMS Center ) handset using SS7 protocol. If you see more in SS7, we need application layer called Mobile Application Part ( MAP ) which send SMS text message using application module Message Originating ( MO ) and Message Terminating ( MT ).
In this protocol we can answer that limitation is in SMS development. When it was built, SMS just have Digital Coding Scheme ( DCS ) signalling protocol limited 140 octets, which means 140 * 8 bits = 1120 bits. For default alphabet, we use 7 bit / characters, and for another purpose like smart messaging
like images and ringing tones or chinese and japanese we user 8 bit.
For other purposes 16 bit characters encoding will be used like for
Flash SMS which show blinking or alerting SMS.
So for default alphabet we have 1120 bits / 7 bits = 160 characters. In
same we way, we have 140 characters in 8 bit, and 70 characters in 16
So we can see now that for one SMS text messages we have limited 160
characters for 7 bit alphabet, 140 characters for 8 bit alphabet and 70
characters for 16 bit characters.
In the next innovation and improvement you can adjust maximum Digital
Code Scheme upper 140 octets, so we can expand maximum characters for
one SMS text message.
Even your mobile phone has capabilities to write more than 160
characters, the SMS system just see that in several messages. You can
see the indicator in your text messaging that your long SMS based on
phone capabilities only the way to write SMS. SMS system only see it in
several messages. For example if you can write until 400 characters,
the system only see it in 3 SMS text messages and you will be charged
for 3 messages by the mobile operators.But you have alternative way to
send long messages to your mobile operators. To increase the maximum
characters in one SMS text message we can concatenate SMS in larger
content, it is called as long SMS. It is configured in your mobile operator not in your handset.
In concatenated SMS, you will have additional User Data Header ( UDH )
contains segmentation information. Because of that the maximum capacity
will decrease becomes 153 for 7 bit, 133 for 8 bit and 67 for 16 bit.
Here some mobile operators have tariff scheme for this implementation.
Most of them will charge additional UDH bits, because they uses system
Next I will explain about SMStariff scheme
from Bakrie Telecom which apply tariff scheme SMS for characters you
sent, not based on how many messages you sent. So here, I hope you
clear about the maximum of SMS characters you have in one SMS text