Multimedia Messaging Service
for short, is a cellular telephone
standard for sending messages that include multimedia objects (images, audio, video, rich text
). MMS is an extension of the SMS
standard, allowing longer message lengths and using WAP to display the content. Its most popular use is sending photographs from camera-equipped handsets, although it is also popular as a method of delivering ringtones
as well. The standard is developed by the Open Mobile Alliance
(OMA), although during development it was part of the 3GPP
MMS messages are delivered in a fashion almost identical to SMS, but any multimedia content is first encoded and inserted into a text message in a fashion similar to sending a MIME
e-mail. MMS defines a subset of MIME content formats in the MMS Message Encapsulation specification. The message is then forwarded to the carrier's
SMS store and forward
server, the "MMS relay". If the receiver is on another carrier, the relay forwards the message to the recipient's carrier using the Internet.
Once it reaches the correct MMS relay for the receiver, the content is extracted and sent to a temporary storage server (often the same process as the relay) with an  front-end. An SMS "control message" containing the URL of the content is then sent to the recipient's handset to trigger the receiver's WAP browser to open a receive the content from the embedded URL. Several other messages are exchanged to indicate status of the delivery attempt.
Some installations also include a conversion service that will attempt to modify the multimedia content into a format suitable for the receiver. This is known as "content adaptation", or MMSC.
E-mail and web-based gateways to the MMS (and SMS) system are common. On the reception side, the content servers can typically service requests both from WAP and normal  browsers, so delivery via the web is simple. For sending from external sources to handsets, most carriers allow MIME encoded message to be sent to the receiver's phone number with a special domain – for instance, Fido Solutions allows users to send MMS messages to Fido recipients via their email@example.com gateway.
The original SMS system was developed as part of the GSM
family of standards, able to deliver messages of up to 160 characters. Driven by low costs, SMS rapidly grew in popularity, and by 2000 over 15 billion messages were being delivered every year.
In order to add some functionality to the basis SMS system, in the late 1990s Ericsson proposed the Enhanced Messaging Service (EMS). EMS added a number of control characters to control basic text style (bold, color, etc.) as well as insert a small number of pre-defined graphics. EMS never caught on, although it was a feature of some Ericsson and Sony handsets.
At the time, 2G GSM was in the process of evolving into the 2.5G GPRS of roughly double the performance. A short 160 character limit no longer made sense, so the "Third-Generation Partnership Program" (3GPP) proposed extending the existing SMS standard to allow messages of any length. Additionally, they proposed adding MIME support for file attachments, and real multimedia support. However, modifying display systems to handle any sort of media format was a more difficult problem, so 3GPP partnered with the WAP standards process to produce MMS.
Since then, MMS has been deployed worldwide and across both GSM/GPRS and CDMA networks. The first commercial MMS launched worldwide was in March 2002 by Telenor, in Norway, using Acision infrastructure. MMS remains part of the 3G networks as well (WCDMA and CDMA2000), and will almost certainly be retained in the 4G networks currently being developed.Both 3GPP and 3GPP2 have delegated the development of the Stage 3 Technical Realizations to the OMA, a standards organization focused on specifications for the mobile wireless networks.
GSM Association has produced a MMS Interworking Guidelines IR.52 document for MMS interconnection between GSM operators.
Challenges faced by MMS
There are some interesting challenges with MMS that do not exist with SMS:
- Content adaptation: Multimedia content created by one brand of MMS phone may not be entirely compatible with the capabilities of the recipients' MMS phone. In the MMS architecture, the recipient MMSC is responsible for providing for content adaptation (e.g., image resizing, audio codec transcoding, etc.), if this feature is enabled by the mobile network operator. When content adaptation is supported by a network operator, its MMS subscribers enjoy compatibility with a larger network of MMS users than would otherwise be available.
- Distribution lists: Current MMS specifications do not include distribution lists nor methods by which large numbers of recipients can be conveniently addressed, particularly by content providers, called Value-added service providers (VASPs) in 3GPP. Since most SMSC vendors have adopted FTP as an ad-hoc method by which large distribution lists are transferred to the SMSC prior to being used in a bulk-messaging SMS submission, it is expected that MMSC vendors will also adopt FTP.
- Bulk messaging: The flow of peer-to-peer MMS messaging involves several over-the-air transactions that become inefficient when MMS is used to send messages to large numbers of subscribers, as is typically the case for VASPs. For example, when one MMS message is submitted to a very large number of recipients, it is possible to receive a delivery report and read-reply report for each and every recipient. Future MMS specification work is likely to optimize and reduce the transactional overhead for the bulk-messaging case.
- Handset Configuration: Unlike SMS, MMS requires a number of handset parameters to be set. Poor handset configuration is often blamed as the first point of failure for many users. Service settings are sometimes preconfigured on the handset, but mobile operators are now looking at new device management technologies as a means of delivering the necessary settings for data services (MMS, WAP, etc.) via over-the-air programming (OTA).
- WAP Push: Few mobile network operators offer direct connectivity to their MMSCs for content providers. This has resulted in many content providers using WAP push as the only method available to deliver 'rich content' to mobile handsets. WAP push enables 'rich content' to be delivered to a handset by specifying the URL (via binary SMS) of a pre-compiled MMS, hosted on a content provider's web server. A downside of WAP push is that from a billing perspective this content is typically billed at data rates rather than as an MMS. These charges can be significant and result in 'bill shock' for consumers.
Although the standard does not specify a maximum size for a message, 300 kB is the current recommended size used by networks due to some limitations on the WAP gateway side.
- EAIF — Nokia's External Application Interface
- MM1 — the 3GPP interface between MMS User Agent and MMS Center
- MM2 — the 3GPP interface between MMS Relay and MMS Server
- MM3 — the 3GPP interface between MMS Center and external servers
- MM4 — the 3GPP interface between MMS Centers
- MM5 — the 3GPP interface between MMS Center and HLR
- MM6 — the 3GPP interface between MMS Center and user databases
- MM7 — the 3GPP interface between MMS VAS applications and MMS Center
- MM8 — the 3GPP interface between MMS Center and the billing systems
- MM9 — the 3GPP interface between MMS Center and an online charging system
- MM10 — the 3GPP interface between MMS Center and a message service control function
- MM11 — the 3GPP interface between MMS Center and an external transcoder
- MMS-Stamp - the worlds first MMS postage stamps, published by the Swiss Post after a public competition