Posted by: tonyteaching | April 16, 2009

What is SMS?

mobilephone SMS stands for Short Message Service.

It is a technology that enables the sending and receiving of messages between mobile phones.

SMS first appeared in Europe in 1992. It was included in the GSM (Global System for Mobile Communications) standards right at the beginning. Later it was ported to wireless technologies like CDMA and TDMA. The GSM and SMS standards were originally developed by ETSI. ETSI is the abbreviation for European Telecommunications Standards Institute. Now the 3GPP (Third Generation Partnership Project) is responsible for the development and maintenance of the GSM and SMS standards.

As suggested by the name “Short Message Service”, the data that can be held by an SMS message is very limited.

One SMS message can contain at most 140 bytes (or 8 bits/byte x140 bytes= 1120 bits) of data, so one SMS message can contain up to:

  • 160 characters if 7-bit character encoding is used. (7-bit character encoding is suitable for encoding Latin characters like English alphabets.) ………………………..1120 bits/Latin characters (7-bit/character)=160 characters
  • 70 characters if 16-bit Unicode UCS2 character encoding is used. (SMS text messages containing non-Latin characters like Chinese, Japanese, Arabic, or Korean characters should use 16-bit character encoding.) ……………….. 1120 bits/non-Latin characters (16-bit/character) = 70 characters

SMS text messaging supports languages internationally. It works fine with all languages supported by Unicode, including Arabic, Chinese, Japanese and Korean.

One major advantage of SMS is that it is supported by 100% GSM mobile phones. Almost all subscription plans provided by wireless carriers include inexpensive SMS messaging service. Unlike SMS, mobile technologies such as WAP and mobile Java are not supported on many old mobile phone models.


How SMS sends a long message (more than 1120 bits data)?

One drawback of the SMS technology is that one SMS message can only carry a very limited amount of data. To overcome this drawback, an extension called concatenated SMS (also known as long SMS) was developed.

A concatenated SMS text message can contain more than 160 English characters.

Concatenated SMS works like this: The sender’s mobile phone breaks down a long message into smaller parts and sends each of them as a single SMS message. When these SMS messages reach the destination, the recipient mobile phone will combine them back to one long message.

It’s why we found that some mobile phone said support long SMS (able to break down data more than 112o bis and to combine incoming long data as well), while some doesn’t support.

The drawback of concatenated SMS is that it is less widely supported than SMS on wireless devices.


How can SMS send picture, animation, and sound?

1. By sending binary data

Besides text, SMS messages can also carry binary data. It is possible to send ringtones, pictures, operator logos, wallpapers, animations, business cards (e.g. VCards) and WAP configurations to a mobile phone with SMS messages.

2. Using EMS (Enhanced Messaging Service)

Besides the data size limitation, SMS has another major drawback an SMS message cannot include rich-media content such as pictures, animations and melodies.

EMS (Enhanced Messaging Service) was developed in response to this. It is an application-level extension of SMS. An EMS message can include pictures, animations and melodies. Also, the formatting of the text inside an EMS message is changeable. For example, the message sender can specify whether the text in an EMS message should be displayed in bold or italic, with a large font or a small font.

The drawback of EMS is that it is less widely supported than SMS on wireless devices. Also, many EMS-enabled wireless devices only support a subset of the features defined in the EMS specification. A certain EMS feature may be supported on one wireless device but not on the other.




  1. It’s a benefit topic.

    I have a question.

    I try to send SMS which counts (160*2=320) but the mobile calculate it as 3 parts, why ?

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