What are SMS and MMS?

Short message server enables mobile phones (including Pocket PC phones) to send short messages using GSM network. It has many interesting functions:

A short message can contain at most 160 characters (even binary).

SMS is a store and forward service. In other words, short messages are not sent directly from the sender to the receiver, but are always forwarded through the short message center. If the recipient is disconnected (the phone may be turned off), the message will be sent when the recipient connects again.

SMS has the function of sending a message to confirm. This means that SMS is different from paging, and users don't simply send short messages and then believe that the messages have been sent successfully. On the contrary, the short message sender can receive the return message and inform them whether the short message has been sent successfully.

The sending and receiving of SMS messages can be synchronized with GSM voice.

SMS messages are charged per message, so they are much more expensive (per byte) than data sent over IP-based networks (for example, using GPRS).

To use SMS, users need to subscribe to a mobile network that supports SMS, and users must be able to use SMS. Users need to have a destination to send or receive short messages. This destination is usually another mobile phone, but it can also be a server. Finally, users need to have a mobile phone that supports short messages and know how to send or read short messages with their specific mobile phone.

Why use text messages?

For application developers, the direct solution to connect Pocket PC phones to the server may be through an IP-based network, such as the Internet. The advantages of this method include: the universal standard protocol already exists and the communication tools are ready-made.

However, in some cases, IP-based network is not the most effective transmission mode. Active connection or even automatic connection will take up valuable time and it is impossible to connect during the call. If there was a way to connect to the server instantly even when talking, what would it be? Since Pocket PC Phone can send SMS messages, this may be an implementation.

Instant connection is often very useful when mobile workers need to notify business process applications of important events. It may be a salesman who informs the server that there is a new order, or a truck driver who just delivered the goods.

On the server side, there are many solutions to receive SMS messages and forward them to other systems. Examples are products of MobileSys, Inc. and Smartserv Online, Inc. In this article, we will further discuss the SMS performance of Pocket PC phone.

MMS is the abbreviation of (Multimedia Message Service), which means multimedia short message service in Chinese. Its biggest feature is that it supports multimedia functions. Multimedia information makes the transmission of content and information have comprehensive functions, including multimedia information such as images, audio information, video information, data and text, and can support various high-speed data services such as voice, Internet browsing, e-mail, conference TV and so on. With the support of GPRS network and WAP wireless application protocol as the carrier, video clips, pictures, sounds and texts are transmitted. Multimedia message service can realize instant multimedia information transmission from mobile phone end to end, from mobile phone terminal to Internet or from Internet to mobile phone terminal.

MMS information is compressed in a standard way, so the receiver can confirm the content format it does not support and process it in a controlled way. This is also a method to solve the problem of Internet content interaction.

The media types supported by MMS standard are: JPEG, GIF, text, AMR voice and other non-mainstream formats. In order to get better interactivity, Nokia and other manufacturers have drafted a "MMS conformance document", which lists the minimum set of content types that MMS phones can support.

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