Page 182 - DCAP311_DCAP607_WIRELESS_NETWORKS

Wireless Networks

Notes SMS technology allows the “push” of information. This is different from the “pull” model where
a device has to poll the server regularly in order to check whether there is any new information.
The “pull” model is less suitable for alert and notification applications, since it wastes bandwidth
and increases server load.
Some common SMS alert and notification applications are described below.
1. Email, Fax and Voice Message Notifications: In an email notification system, a server sends
a text message to the user’s mobile phone whenever an email arrives at the inbox. The SMS
text message can include the sender’s email address, the subject and the first few lines of
the email body. An email notification system may allow the user to customize various
filters so that an SMS alert is sent only if the email message contains certain keywords or if
the email sender is an important person. The use cases for fax or voice message are similar.

2. E-commerce and Credit Card Transaction Alerts: Whenever an e-commerce or credit card
transaction is made, the server sends a text message to the user’s mobile phone. The user
can know immediately whether any unauthorized transactions have been made.

3. Stock Market Alerts: In a stock market alert application, a program is constantly monitoring
and analyzing the stock market. If a certain condition is satisfied, the program will send a
text message to the user’s mobile phone to notify him/her of the situation. For example,
you can configure the alert system such that if the stock price of a company is lower than a
certain value or drops by a certain percentage, it will send an SMS alert to you.

4. Remote System Monitoring: In a remote system monitoring application, a program
(sometimes with the help of a group of sensors) is constantly monitoring the status of a
remote system. If a certain condition is satisfied, the program will send a text message to
the system administrator to notify him/her of the situation.

Example: A program may be written to “ping” a server regularly. If no response is
received from the server, the program can send an SMS alert to the system administrator to notify
him/her that the server may be hanged.

11.3.5 Two-way Interactive Text Messaging Applications

SMS messaging technology can be used as the underlying communication medium between
wireless devices and servers in a two-way interactive text messaging application. For example,
search engines are two-way interactive text messaging applications. Let’s say there is a dictionary
search engine that supports queries in SMS text messages. It may operate like this:
To find out the meaning of the term “SMS text messaging”, you can type “find: SMS text
messaging” in an SMS text message and send it to the search engine’s phone number. After
receiving your SMS text message, the search engine parses it and finds that it begins with the
command “find” and follows by the words “SMS text messaging”. The search engine then knows
you want to find out the meaning of the term “SMS text messaging”. So, it sends a text message,
which contains the meaning of the term “SMS text messaging”, back to your mobile phone.

If the search result is very long and it cannot contain within a single SMS text message, the search
engine adds “Page 1 of 2”, “Page 1 of 3”, etc, at the end of the reply SMS text message. The search
engine also creates a session using your mobile phone number as the session ID and stores the
term that you searched for (i.e. “SMS text messaging”) in the session object.
To request the second page, you can send a text message with the content “page: 2” to the search
engine’s phone number. After receiving your SMS text message, the search engine parses it and
finds that it begins with the command “page” and follows by “2”. The search engine then knows
you want the second page of the search result. It retrieves the term that you searched for last time
from the session object and finds that it is “SMS text messaging”. The search engine then sends a

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