How SMS Works?
Just when we’re finally used to seeing everybody constantly talking on their cell phones, it suddenly seems like no one is talking at all. Instead, they’re typing away on tiny numerical pads, using their cell phones to send quick messages. SMS, or text messaging, has replaced talking on the phone for a new “thumb generation” of texters.
In this article, we’ll find out how text messaging works, explore its uses and learn why it sometimes takes a while for your text message to get to its recipient.
What is SMS?
Recently it has been suggested that SMS messages could be used to attack a cell phone system. The basic idea is very simple. If a large number of SMS messages were sent by computers to phones in a small geographical area (like a city), these messages would overwhelm the control channels and make it impossible for the cell phone system to set up calls. Now that cell phone providers know about the possibility of this threat, they can design systems to throttle messages coming from the SMSC onto the network.
SMS stands for short message service. Simply put, it is a method of communication that sends text between cell phones, or from a PC or handheld to a cell phone. The “short” part refers to the maximum size of the text messages: 160 characters (letters, numbers or symbols in the Latin alphabet). For other alphabets, such as Chinese, the maximum SMS size is 70 characters.
But how do SMS messages actually get to your phone?
If you have read How Cell Phones Work, you can actually see what is happening.
Even if you are not talking on your cell phone, your phone is constantly sending and receiving information. It is talking to its cell phone tower over a pathway called a control channel. The reason for this chatter is so that the cell phone system knows which cell your phone is in, and so that your phone can change cells as you move around. Every so often, your phone and the tower will exchange a packet of data that lets both of them know that everything is OK.
Your phone also uses the control channel for call setup. When someone tries to call you, the tower sends your phone a message over the control channel that tells your phone to play its ring tone. The tower also gives your phone a pair of voice channel frequencies to use for the call.
The control channel also provides the pathway for SMS messages. When a friend sends you an SMS message, the message flows through the SMSC, then to the tower, and the tower sends the message to your phone as a little packet of data on the control channel. In the same way, when you send a message, your phone sends it to the tower on the control channel and it goes from the tower to the SMSC and from there to its destination.
The actual data format for the message includes things like the length of the message, a time stamp, the destination phone number, the format, etc. For a complete byte-by-byte breakdown of the message format, see this page.
In the next section we’ll learn about some of the uses and advantages of SMS.
Why 160 Characters?
SMS was designed to deliver short bursts of data such as numerical pages. To avoid overloading the system with more than the standard forward-and-response operation, the inventors of SMS agreed on a 160-character maximum message size.
But the 160-character limit is not absolute. Length limitations may vary depending on the network, phone model and wireless carrier. Some phones don’t allow you to keep typing once the 160-character limit is reached. You must send your message before continuing. However, some services will automatically break any message you send into chunks of 160 characters or less. So, you can type and send a long message, but it will be delivered as several messages.
Why use SMS?
SMS has several advantages. It is more discreet than a phone conversation, making it the ideal form for communicating when you don’t want to be overheard. It is often less time-consuming to send a text message than to make a phone call or send an e-mail. SMS doesn’t require you to be at your computer like e-mail and instant messaging (IM) do — although some phones are equipped for mobile e-mail and IM services. SMS is also a convenient way for deaf and hearing-impaired people to communicate.
SMS is a store-and-forward service, meaning that when you send a text message to a friend, the message does not go directly to your friend’s cell phone. The advantage of this method is that your friend’s cell phone doesn’t have to be active or in range for you to send a message. The message is stored in the SMSC (for days if necessary) until your friend turns his cell phone on or moves into range, at which point the message is delivered. The message will remain stored on your friend’s SIM card until he deletes it.
In addition to person-to-person messages, SMS can be used to send a message to a large number of people at a time, either from a list of contacts or to all the users within a particular area. This service is called broadcasting and is used by companies to contact groups of employees or by online services to distribute news and other information to subscribers.
In a 2004 University of Plymouth study on the psychology of SMS users, researchers found that mobile phone users were primarily either “texters” or “talkers” [ref]. Compared to the talkers, the texters sent nearly double the number of SMS messages and made less than half as many voice calls per month. The texters preferred SMS to voice calls for its convenience as well as for the ability to review a message before sending it.
Companies have come up with many uses for the service beyond just your typical person-to-person message. Because SMS doesn’t overload the network as much as phone calls, it is frequently used by TV shows to let viewers vote on a poll topic or for a contestant. As a promotional tool, wireless carriers put up giant screens at concerts and other large-scale events to display text messages from people in the audience.
You can use text messaging subscription services to get medication reminders sent to your phone, along with weather alerts, news headlines or even novels broken into 160-character “chapters.” Internet search engines such as Yahoo! and Google have short messaging services that enable users to get information such as driving directions, movie showtimes or local business listings just by texting a query to the search engine’s phone number. Social networking services such as Dodgeball use SMS to alert people who live in big cities when their friends or crushes are nearby. The possibilities for integrating SMS into your lifestyle seem endless.
Naturally, SMS has limitations, and there are some people who feel it has outlived its usefulness. In the next section, we’ll look at the disadvantages of SMS and some of the alternatives out there.
SMS History
SMS was created during the late 1980s to work with a digital technology called GSM (global system for mobile communications), which is the basis for most modern cell phones. The Norwegian engineers who invented it wanted a very simple messaging system that worked when users’ mobile phones were turned off or out of signal range. Most sources agree that the first SMS message was sent in the UK in 1992.
As SMS was born in Europe, it’s not surprising that it took a little longer to make its way to the United States. Even today, texting enjoys much greater popularity in Europe, though its stateside use is on the rise. A July 2005 study found that 37 percent of U.S. mobile phone owners had sent or received at least one text message in the previous month [ref].
SMS Criticism and Alternatives
SMS in the News
Because of the impersonal nature of SMS, it raises certain questions of etiquette — namely, what kind of information is OK to send in a text instead of delivering it in person? Recently, several people have sought legal action after they were fired or notified of divorce proceedings via SMS.
Broadcast text messages have been used to rally political activists in Beijing and to mobilize young people for riots in Belfast. Recently, a contest pitted the efficiency of SMS against Morse code (the Morse coders won).
Despite their popularity, short messaging services have recieved some criticism. Here are a few of the disadvantages:
You have to pay for it. Most wireless plans charge for a certain number of text messages a month. Some only charge for user-originated messages, while others charge for incoming messages as well. If you exceed your message allowance, you may be charged 10 cents per message, and those little charges can add up.
Speedy message delivery is not guaranteed. During periods of high traffic, it might be minutes or even hours before a message gets through.
It’s strictly for sending text messages. SMS does not support sending pictures, video or music files.
Alternative messaging services allow for more elaborate types of messages. With EMS (Enhanced Messaging Service), you can send formatted text, sound effects, small pictures and icons. MMS (Multimedia Messaging Service) allows you to send animations, audio and video files in addition to text. If your mobile phone is EMS- or MMS-enabled, you can use these standards just as you would SMS. However, the cost per message will be higher.
Another alternative to using SMS is using an instant messaging program, such as AOL IM, on your cell phone. This can be in the form of software that’s pre-installed on your phone, or you can use WAP (Wireless Application Protocol) to access the Internet and sign into your IM account. WAP is a protocol that gives you small, simplified versions of web pages that are easily navigable on your mobile phone or PDA (check out How WAP Works for more information). You can use it to send instant messages or actual e-mails from your phone.
A common complaint about SMS is its inefficient delivery structure — when the message center is backed up, messages take longer to reach their destination. To make message delivery faster, networks are using more new next-generation technologies such as GPRS (General Packet Radio Service).
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Hi,
With the popularity of AJAX growing every day I’ve had the opportunity to
collect and try out many more tutorials in the last several months. These
examples and how-to’s represent the best tutorials that I’ve personally used or
otherwise had the opportunity to work with out of the overall group. This post
is intended for individuals who learn best by example. Most of the listed
tutorials come complete with instructions and source code. I’ve also categorized
all of the tutorials for easy browsing. Enjoy!
Please let me know through email or a comment if you know of any other great
AJAX tutorials and I’ll be glad to post them. Also special thanks to all of the
folks who produced all of these wonderful free tutorials.
Also See:
Round-up of 30 AJAX Tutorials
AJAX Activity Indicator Tutorial
CakeTimer – An Ajax File Uploads Progress Bar
This is a demonstration of an AJAX powered progressbar to monitor file uploads
with (Cake)PHP.
HowTo add Ajax in-progress indicators
Ok, so my little del.icio.us app (click link to read about how I added Ajax
functionality to a simple Rails app) is pretty cool, but it was missing one big
thing. When the user clicks the "Get Results" link she has no idea that the page
is communicating with the server.
AJAX Bookmarklets Tutorial
Creating Huge Bookmarklets
A bookmarklet is a special piece of JavaScript code that can be dragged into a
user’s link toolbar, and which later can be clicked on to implement cross-site
behavior. People have done all sorts of cool stuff with it.
AJAX Chat Tutorials
AJAX Chat Sources Code for Download
After a slow start (following the announcement of the XHTML (ajax) Chat) things
got finally busy. I had so many requests that I have decided to offer the
complete sources for download.
Lace – Ajax Chat
Lace is a free, lightweight Ajaxian communications engine suitable for a
shoutbox, chat room or similar. Version 0.1.3 brings with it several bug fixes,
a tiny bit of code reorganization and most importantly, an oft-requested User
List.
Most Simple Ajax Chat Ever
Very easy to use AJAX chat demo.
AJAX Client-Server Communication Tutorials
Implementing simple AJAX interaction in your Web Application using
XMLHttpRequest object
Everybody till now must have atleast heard about AJAX (Asynchronous JavaScript
And XML). This example will give you an idea about how you can implement simple
AJAX interaction in your web application.
Make asynchronous requests with JavaScript and Ajax
In this article, you’ll begin with the most fundamental and basic of all
Ajax-related objects and programming approaches: The XMLHttpRequest object. This
object is really the only common thread across all Ajax applications and — as
you might expect — you will want to understand it thoroughly to take your
programming to the limits of what’s possible.
Advanced requests and responses in Ajax
n this article, I move beyond the basics in the last article and concentrate on
more detail about three key parts of this request object, the HTTP ready state,
the HTTP status code and the types of requests that you can make
AJAX
In this tutorial, you’ll be introduced to Ajax, a technology that allows you to
send these requests through small JavaScript calls, meaning the user doesn’t
have to wait for the page to refresh.
All Request, All The Time
Let’s build a simple application that accepts input from the user, passes it to
some PHP on the server that checks it against a database, and returns the result
to the browser. It comes in three parts.
AJAX Drag and Drop Tutorial
Drag and Drop Tutorial (with a cool video)
Adding items to a shopping cart in common e-commerce applications isn’t very
close to the actual "add to cart" metaphor, since it requires clicking an "add
to cart" button, watch a new page (the shopping cart), and then go back to the
shop or checkout with buttons. Ajax allows to get closer to the cart metaphor,
by enabling drag-and-drop interactions and giving immediate visual feedback,
without leaving the shop.
AJAX Dynamically Content Loading Tutorials
Dynamically loaded articles
This is a basic example showing you how to use AJAX. In this script, you have a
list of article titles at the right side. When you click on one of them, AJAX
will be used to request the content of the article from an external file and
show it in the main DIV.
Ajax – Dynamic Content
This small generic script makes it easy for you to load content of external
files into HTML elements on your page.
AJAX Forms and Autocomplete Tutorials
Scriptaculous Lists with PHP
The drag-and-drop effects, most notably the sortables, caught my eye because the
look great, they are so easy to implement, and they’re just so much nicer than
the standard listbox with up/down arrows that we see in most of today’s
applications and administration tools.
Alter data with Ajax forms
Displaying rich formatted questions and lists, even paginated, is not enough to
make an application live. And the heart of the askeet concept is to allow any
registered user to ask a new question, and any user to answer an existing one.
Isn’t it time we get to it?
Dynamic Client Lookup
This script uses AJAX to autofill a form. Open the demo and type in 1001 in the
"client ID" text field. AJAX will when you have done this call a script on the
server and auto fill the rest of the form with client data.
Chained Select Boxes
This script uses Ajax to popuplate a select box with cities based on which
country you choose.
Ajax Dynamic List
This script shows you a list of options based on what you type into a text
input. Example: Type in "A" and Ajax will get you a list of all contries
starting with "A".
AJAX Framework and Toolkit Tutorials
My-BIC – Tutorials and How To’s
A collection of easy to follow tutorials using the My-Bic Framework including a,
hello world – getting your ajax setup, posting comments via AJAX and changing
views from a drop down. There are beginner and intermediate tutorials here.
New Echo2 Tutorial Series
Part 1 of a multipart Echo2 tutorial series, entitled "Ajax with Echo2 and
Eclipse" is now available from our web site. The related archive with the Echo2
distribution plus the EchopointNG library is available here.
AJAX Design Patterns – Using The Dojo Toolkit
Is this tutorial any different from the others? Well yes and no, it is different
in being a tutorial on how to design and build a complete site and not just some
fancy little details like how to turn caching in AJAX off or how to create a
fancy widget.
Using Dojo and JSON to Build Ajax Applications
In this article, I will show how to build Ajax-enabled applications using Dojo
and JSON–two very different but complementary technologies that can
significantly enhance the interface and usability of web applications.
AJAX General Tutorials
Building a Spy
Step by step instructions on how to build a Digg like spy page.
Building a Shelf in WordPress
Nice tutorial on how to build a sliding shelf in WordPress.
AJAX from Scratch: Implementing Mutual Exclusion in JavaScript
This AJAX from Scratch series of articles describes fundamental techniques
needed to develop AJAX Rich Internet Applications in JavaScript from scratch.
Saving Session Across Page Loads Without Cookies, On The Client Side
This is a mini-tutorial on saving state across page loads on the client side,
without using cookies so as to save large amounts of data beyond cookies size
limits.
A Tale of Two IFrames or, How To Control Your Browsers History
This is a mini-tutorial on the black art of iframes and browser history, known
to AJAX experts but rarely presented clearly.
AjaxWorld Special: What Is AJAX?
Learn more about AJAX and ColdFusion
Simple Ajax Functions – Snippets
I’ve created a list of very common JavaScript functions for Ajax. They have been
created in quick reference fashion and do not contain any fancy stuff. Instead
of creating one function which can handle various tasks depending on passed
values, they are split into seperate basic task functions. The reason for this
is simplicity.
AJAX Using ASP.NET 1.1
You’ve heard of it. It is the latest buzz term for web programmers these days.
AJAX is an acronym that stands for Asynchronous JavaScript and XML. AJAX gains
its popularity by allowing data on a page to be dynamically updated without
having to make the browser reload the page. I will describe more about how AJAX
works, and then go into some sample code to try out.
Speed up Your AJAX Based Webapps
It sets the expiry of the JavaScript to years and not days. Once the JavaScript
file is downloaded it is never downloaded again, ofcourse unless you force it by
removing the file in the cache. If you visit the site often the JavaScript will
not be removed from the cache.
Kick-start your Java apps, Part 2
This tutorial guides you through the development of a small human-resources
application, first using conventional JavaServer Pages (JSP) based technology,
and then migrating it to a highly interactive solution using Ajax.
Howto integrate Google Calendar in your website using AJAX
One of the features I find it interesting in Google calendar is the possibility
to create shared calendars, but also the availability of your calendar as XML or
ICAL whatever it’s a private or public one. As soon as we have XML of our
calendar available I was wondering why not integrating Google calendar directly
in website.
Create Your Own Ajax Effects
Why let script.aculo.us have all the fun? Start building your own Ajax-driven
visual effects today. The basic and prebuilt effects in script.aculo.us are
nice, but if you really want to build something great why not investigate doing
your own, homegrown, do-it-yourself effects. We’re going to show you how to take
basic effects and build on them to create your own.
AJAX Getting Started Tutorials
An Introduction to AJAX
A very nice introduction to AJAX.
Nitty Gritty Ajax
In the course of this tutorial, we’re going to look at what Ajax can do. Then
we’ll use a JavaScript class to simplify your first steps toward the ultimate in
speedy user interactivity.
A simple AJAX example
Based on Rasmus’s 30 second AJAX tutorial, I’ve cobbled together a very
rudimentary example of one approach to AJAX programming. A "Hello, World" AJAX
program, if you will. You can view the demo here on my site, and download the
source code (document attachment at the bottom of this article).
A List Apart: Articles: Getting Started with Ajax
The start of 2005 saw the rise of a relatively new technology, dubbed "Ajax" by
Jesse James Garrett of Adaptive Path. Ajax stands for Asynchronous JavaScript
and XML. In a nutshell, it is the use of the nonstandard XMLHttpRequest() object
to communicate with server-side scripts.
Ajax Toybox
Justin has put together a nice group of AJAX tutorials including, Hello, World,
Dynamic City, State Lookup, Ajax to Clean Your Clock, Ajax Calculator and an RSS
News Ticker.
Introduction to Ajax
When it comes to Ajax, the reality is that it involves a lot of technologies —
to get beyond the basics, you need to drill down into several different
technologies (which is why I’ll spend the first several articles in this series
breaking apart each one of them).
Ajax Toolbox / XMLHttpRequest AjaxRequest Library Examples
A great group of AJAX examples.
Rasmus’ 30 second AJAX Tutorial
I find a lot of this AJAX stuff a bit of a hype. Lots of people have been using
similar things long before it became "AJAX". And it really isn’t as complicated
as a lot of people make it out to be. Here is a simple example from one of my
apps.
An Ajax "Hello World" project to Get You Going
Sometimes we all want something very simple to build a thorough understanding of
the mechanics of a new technique before we dive into the deeper water beyond.
Now, if you are into ASP.NET and not PHP you might like to take a look at my
version of this ultra-simple introduction to Ajax with sincere thanks to the
original author.
Ajax Beginners Tutorial
In this tutorial we’ll discuss the basic principles of remote scripting using
Ajax, a combination of javascript and XML to allow web pages to be updated with
new information from the server, without the user having to wait for a page
refresh.
AJAX Image and Gallery Tutorials
Image crop – DHTML user interface
This script gives you an Image crop/resize DHTML user interface. Drag a
rectangle around the area you want to crop. Click the "Crop" button and let Ajax
send crop data to the server and the cropped image back to you. PHP uses
ImageMagick on the server to crop and convert the image.
Prototype Javascript Lightboxes
This class is based on Prototype 1.5. The code is inspired of the powerful
script.aculo.us library. You can even use all script.aculo.us effects to show
and hide windows if you include effects.js file.
AJAX Sortable List Tutorial
How to Make Sortable Lists
Many web applications need to offer an interface to order items – think about
categories in a weblog, articles in a CMS, wishes in an e-commerce website…
The old fashion way of doing it is to offer arrows to move one item up or down
in the list. The AJAX way of doing it is to allow direct drag-and-drop ordering
with server support.
AJAX RSS Tutorials
Simple Ajax RSS ticker script
This very small and simple script reads RSS data from an external source and
shows them inside a predefined box DIV or other tag) on your page. What you have
to do is to specify the url to the RSS feed, how many items you want to show,
and for how many seconds you want the script to display each item.
Dragable RSS boxes
This is is a script that uses Ajax to read data from external RSS sources and
display them inside dragable boxes. You can also create new boxes dynamically
directly from the page. This is the first version of this script. New
functionality will be added to this script during the following weeks and
months.
Slide In RSS items
This scripts reads RSS feeds from an external source and displays them on your
page. Each items appears after a predefined number of seconds by sliding in from
the right side.
RSS Ticker with AJAX
Well, with this powerful RSS ticker script, you can now easily display any RSS
content on your site in a ticker fashion! This script uses a simple PHP based
RSS parser called LastRSS for retrieving a RSS feed, then Ajax and DHTML to
display the feed dynamically and with flare. As a pre-requisite then, your site
itself must support PHP, though the page using this ticker can be any regular
HTML file.
AJAX Shopping Cart Tutorials
Fly to basket (Shopping cart)
This is a DHTML shopping cart module. The products will fly to the shopping
basket when you click on the "Add to basket" button. Ajax is used to dynamically
update the content of the basket.
Flexstore on Rails Tutorial
Flexstore is a traditional Shopping Cart application that you can write in Ruby
on Rails. Very comprehensive and cool.
AJAX Sorting Tutorial
Sorttable: Make all your tables sortable
While the web design community gradually moves away from using tables to lay out
the structure of a page, tables really do have a vital use, their original use;
they’re for laying out tabular data.
AJAX Trees Tutorials
Update a tree with AJAX
his scripts adds an AJAX extension to my static folder tree. Open the demo and
press down your mouse button on one of the nodes in thee tree. This will make a
text box appear which makes it possible for you to rename nodes. AJAX is used to
send this value to the server without reloading the page.
Static list based folder tree
This is a list based folder tree. What you have to do is to create a UL LI list.
The script will then create the tree based on this list. The script uses cookies
to remember state of nodes. It also includes functions for expanding/collapsing
all nodes.
AJAX Username Availability Tutorial
AJAX username availability checking
The goal of this AJAX example is to allow a user who is registering for your
site to see if the username they want to use is taken already or not, without
having to submit a form and reload the page.
AJAX Voting Tutorial
Digg-like AJAX Vote On
This tutorial will show you how to add AJAX-enhanced interactions to askeet. The
objective is to allow a registered user to declare its interest about a
question.
Ajax Poller
A poller script that uses Ajax to send vote to the server and receives vote
results from the server. The results are displayed in some animated graphs.
Thanks
Popularity: 1%
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