Short Message Service (SMS)

Short Message Service (SMS) is a text message service that enables the transmission of short messages between a cell phone, PDA, PC, or any device with an Internet protocol (IP) address. Since this service was standardized in the mid 1990s, it has recorded tens of billions of messages and is being used worldwide. SMS was introduced in the Global System for Mobile Communications (GSM) and later adopted by other mobile communication systems such as Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA).

The service supports messages that are no more than 140 to 160 alphanumeric characters in length, which is typically around 30 to 40 words in Latin and 70 characters for non-Latin alphabets like Chinese and Arabic. Initial applications of SMS were based on replacing alphanumeric pagers by supporting two-way messaging services, primarily voice mail. SMS is used for many applications. For example, GameWorld Technologies' game entitled "Women Are Smarter?" is a mobile trivia game with a gender twist. Players respond to trivia questions that include the option to make double-or-nothing wagers on which gender answers the question correctly more often. Data regarding question and regarding which gender answers correctly more frequently are updated in real-time.

Additional services were added such as electronic mail, fax, notification service in which users are notified when predetermined events occur (e.g., receipt of email, scheduled appointments), integration of email into the SMS service, paging and its integration into the SMS service, interactive banking, and information update services (e.g., financial information, weather, news, directory assistance).

The SMS service on the SMS-enabled phone is always on—the phone is able to receive or send a short message at any time, even if a voice conversation is in progress. This is possible since the SMS messages are delivered to and from the cell phones or wireless devices over the system's control channel and not over the voice channel. This helps in preserving the voice quality while utilizing the control channel. However, the control channel capacity imposes a limit on the length of the messages since the control channel is used for control services such as phone location and call management. As the numbers of SMS messages have increased, concerns about potential service problems caused by overdemand have been mentioned. SMS guarantees delivery of the short message. Temporary failures are identified, and the short message is stored in the network until the destination device becomes available. The message is sent to the nearest Short Message Service Center (SMSC), which either delivers it to the addressed mobile device or forwards it to the next SMSC. The messages are stored and forwarded in the SMSCs until they are received by the addressees. In the delivery process, the SMSC first sends an SMS request to the Home Location Register (HLR) to locate the addressed mobile phone. The HLR is a database used for storing and managing subscriptions and service profiles. If the addressed mobile phone is found, the HLR provides the routing information. If the HLR cannot locate the addressed phone, then the SMSC stores the message for a limited time and tries to deliver the message again when the addressee connects to the network. If the addressee is found, the message is delivered and the SMSC receives verification that the message has been received by the addressee. The sender is informed that the SMS message has been received by the addressee.

Enhanced Messaging Service (EMS)

Enhanced Messaging Service (EMS ) evolved from the popular SMS. Service providers started to offer EMS in early 2000. EMS allows much richer content options than text-based SMS messages and can include pictures, melodies, sound marks, graphic, animations, fonts, and formatted text. For example, a person could send this text to his date with an SMS message "I love you." Using EMS, he could add a short animation of flowers along with a love melody. EMS uses the store-and-forward mechanism provided by the SMSCs. Similar to SMS, EMS uses the control channels. EMS is enabled by SMS concatenation, linking several short messages together.

EMS supports basic and extended pictures. Basic pictures are black and white small (16x16 pixels) pictures or large (32x32 pixels) pictures. Extended pictures can be, however, black and white, grayscale, or color. Extended pictures can contain 255x255 pixels and can be transmitted in a compressed format.

EMS also supports sound. There are a few predefined sounds, including low and high chimes and chords, Claps, TaDa, and drum sounds, as well as Notify, User-Defined, and Extended Sounds. Predefined sounds are not transmitted over the air. Only a reference to the sound is included in the EMS. There are ten different sounds that can be added in the message, and when the sound reference is being displayed, the referenced sound will be played. The sender can also download melodies from various web sources. These sounds have to be formatted according to the iMelody standard. These melodies can take up to 128 bytes.

Animations in EMS provide users with a much stronger alternative for expression than plain pictures. EMS supports predefined animations that reflect happiness, sadness, flirtatiousness, gladness, skepticism, and grief. User-defined and extended animations are supported as well. Similar to sounds and pictures, EMS predefined animations are not sent as animation over the air. Only a reference to them is included in the EMS message. When the message is received by the addressee the referenced animation is displayed in a manner that is specified by the manufacturer. User-defined animations consist of four pictures. There are two different animation sizes: small (8x8 pixels) animations and large (16x16 pixels) animations. These animations are sent over the air interface. Extended animations may be black and white, grayscale, or color. The maximum size of a single animated frame is 255x255 pixels. The repetition of these animations may be controlled by the sender and can be transmitted in a compressed form.

An EMS message can be sent to a mobile phone or other wireless device, even if it does not support EMS, because all the EMS components (i.e., text formatting, pictures, animations, and sounds) are located in the message header. The EMS contents included in the header will be ignored by the receiving mobile phone if it does not support EMS, and only the text message will be displayed.

Multimedia Messaging Service (MMS)

Multimedia Messaging Service (MMS) technology is the ultimate messaging application, allowing users to create messages that include any combination of text, graphics, photographic images, speech, and audio or video clips. MMS supports standard image formats such as JPEG and GIF, video formats such as MPEG 4, and audio formats such as MP3 and MIDI. Multimedia messaging depends on the high transmission speeds that will be available via 3G technologies. MMS is expected to be the future multimedia messaging technology. As compared with the SMS size limitation of 160 bytes, MMS will have no limitation even if some initial implementations may pose restrictions on the message size. Rather than sending a simple message such as "I am late," the user will be able to send a message that better explains the reasons of being late. This unlimited message size will allow users to express rich content in their messages for ultimate expression of ideas, personality, and feelings. Being able to send pictures allows users to share experiences with friends, family members, and business partners. In business applications, users can capture relevant pictures and send them to colleagues or to their home office or they can store them locally for future retrieval.

MMS built-in presentation layering can control timing and synchronization, allowing users to view, listen to, and read the messages simultaneously. MMS can support picture sharing. MMS will be able to include still images such as pictures, screensavers, postcards, graphics, greeting cards, maps, and business cards. In addition, MMS will support animation, video, cartoons, and interactive video.

MMS will use the Wireless Application Protocol (WAP) as supporting technology and the highspeed 2.5G and 3G transmission technologies such as Enhanced Data rate for Global Evolution (EDGE), General Packet Radio Service (GPRS), and Universal Mobile Telecommunications System (UMTS). These high-speed connection technologies can provide users with the necessary bandwidth to send and receive rich-content multimedia messages. In SMS and EMS, the messages are transmitted over the control channel, which severely limits the transmission capacity. Instead, MMS will use the data channels used by all other voice and data applications. Consequently, MMS will be able to deliver much larger messages. MMS is also expected to use MExE (Mobile Execution Environment), which is a flexible and secure application environment for 2.5G and 3G mobile devices. MExE includes a variety of current technologies such as WAP and Java. Similar to SMS and EMS, MMS is a non-real-time service that routes multimedia messages to MMS servers.

MMS can include the following:

• Audio, sound, streaming audio, melodies, songs. For example, instead of sending a downloaded birthday jingle in EMS, a user can send a personalized video clip combined with the song "Happy Birthday."
• Images or pictures that are either stored or taken via a camera that is attached or part of the wireless phone or terminal. Users can take a snapshot and immediately send it to an addressee.
• Video clips. Initially the video clip may be limited to 30 seconds. This will allow users to include video clips recorded with their digital camera and to add text, labels, and appropriate audio to their messages. MMS will also support streaming video so that users can subscribe to news and entertainment services and send their own captured video as a video stream.
• Synchronized Multimedia Integration Language (SMIL, pronounced "smile") which enables simple authoring of interactive audiovisual presentations. SMIL can be used to create rich-content multimedia presentations that include streaming video and audio as well as pictures, images, text, or any other medium type. SMIL is based on an HTML-like language (standard defined by www.w3.org).

Wireless Application Protocol (WAP)

Wireless Application Protocol (WAP) is an open, global standard that provides a microbrowser environment optimized for wireless devices, such as phones and pagers. The goal is to easily access and interact with information over the Internet. WAP is being employed in the broad area of wireless applications. This standard is defined by the WAP forum whose members are wireless and Internet companies around the world to ensure interoperability and foster growth of the wireless markets. It ensures that all WAP-based applications work across all devices, from cell phones to more powerful hand-held devices. Also it allows for WAP-based applications to use less memory, processing power, display, and key handling than legacy Internet applications. Thus the WAP standard helps in delivering the multimedia content while using less bandwidth.

The most recent standard is WAP 2.0, published in 2002. It adds support for the standard Internet communication protocols: IP, TCP, and HTTP. It also allows applications to work over all existing and coming wireless 3G technologies. It provides a rich application environment, which enables delivery of information and interactive services to digital mobile phones, pagers, PDAs, and other wireless devices. It addresses the unique characteristics of wireless devices. These devices have hardware limitations (e.g., small screens, limited battery life, and limited memory) requiring special attention to user interface design (e.g., one-finger navigation). WAP uses the Pull Model, where the user requests content from the server. WAP 2.0 adds telephony support with WTA (Wireless Telephony Application) which enables a wide range of advanced telephony applications in addition to their legacy support of data-only functionality. These tools include call handling services, such as making calls, answering them, placing them on hold, and redirecting them.

WAP 2.0 supports a Push Model, which allows server-based applications to send or "push" the content to the devices via a Push Proxy. Push functionality is especially important for sending news, announcements, and notifications to interested users. The content can include stock prices, location-based promotions, and traffic update alerts. Without push functionality, these types of applications would require the devices to specifically pull or request application servers for such new information. In wireless environments such pulling activities, if done persistently and frequently, would burden the limited resource network with wasteful traffic.

The External Functionality Interface (EFI) service specifies the interface between the Wireless Application Environment (WAE) and plug-in modules, which extends or enhances the capabilities of browsers or other applications. The EFI framework provides for future growth and extendibility of supported WAP devices and can be used to access external devices (e.g., smart cards, GPS devices, digital cameras).

A WAP proxy (or WAP gateway) was required in the original WAP standard. Such proxy handles the conversion between the WAP client and the origin server equipped with legacy Internet servers that are not optimized for the limited bandwidth of the wireless channel. WAP 2.0 does not require a WAP proxy. However, use of a WAP proxy can provide several important benefits such as optimizing the communication process in the wireless network and may offer mobile service enhancements such as location, secure channels (privacy), caching, and presence-based services. A proxy can also translate between WAP and other WWW protocols, allowing WAP clients to communicate with servers that do not support WAP. A WAP proxy is necessary to offer push functionality. Proxies may be located in several locations, for example, at the wireless telephone service providers and hosting companies.