Introduction to Short Message Service (SMS)

 1. Introduction

Short Message Service (SMS) is the technology that enables user to send and receive text messages via mobile phones. It supports alphanumeric message up to 160 characters, by packing the 7-bit ASCII characters into 8-bit octets. Message can be typed directly using cellular phones or via other interfaces such as computers.

2. SMS Service Types

There are two basic types of SMS:

o Point-to-point communication

Point-to-point communication service is the service that supports messages between two subscribers of the SMS services. This is the service type that is used by normal individual subscribers.

o SMS cell broadcast service (SMSCB)

SMS cell broadcast service is the type of service whereby the same message is broadcast to multiple SMS subscribers. Such service is only available to the network operators, and is normally used for messages like weather alerts and news reports.

3. SMS Network Architecture

SMS network architecture is based on the architecture of Global System for Mobile Communications (GSM).

SMS is a store and forward data services. This means that messages are not sent to the destination directly. Instead, messages are routed and stored in SMS Message Centre (SMSMC), and then forwarded to the destination.

An SMSMC provides a number of services, including the regulation and transfer of text messages between mobile phones. When a subscriber sends a text message to a recipient, the mobile phone actually sends the message to the SMSMC. The SMSMC stores the message and then delivers it to the designated recipient when they are available. The SMSMC usually has a configurable validity period that determine how long it will store the message, and the user can usually specify a shorter validity period if they want.

In addition to regulation of messages, the SMSMC also handles any charging that needs to take place. In general, there is at least one SMSMC per network.

4. Conclusion

This article aims to provide an introductory guide to the Short Message Service (SMS) which is part of the GSM specification. The limit in size of SMS is 160 characters if purely Latin alphabets are used. If non Latin alphabets such as Chinese characters are used, the limit will be 70 characters.

Dennis Chang is the founder of textverified He holds a Master of Science (MSc) degree in Communication Software and Networks, and a Honours degree in Electrical & Electronic Engineering from Nanyang Technological University, Singapore.