EMS is also an abbreviation for Enhanced Messaging Service, an extension to the mobile phone SMS or text message communication protocol. SMS is part of the GSM standard for mobile phone communication; EMS was designed by 3GPP (3rd Generation Partnership Project, a part of ETSI), the standardizing body responsible for GSM and SMS. EMS is designed to build on SMS to allow users to send melodies (like ringtones), graphics and animations, as well as formatted or unformatted text in excess of the 160-character limit imposed on SMS messages.
EMS is a universal standard, although that does not mean it is being implemented by all mobile phone vendors. Ericsson are keen on it as a means of overcoming Nokia's market dominance which is interrelated with Nokia's proprietary standards for messaging. In addition, Alcatel, Motorola and Siemens have all expressed their intention to support the format, having worked with Ericsson on its development. Nokia, being market leaders, would prefer to use their own systems.
EMS messages are designed so that a portion of the message will show up as a normal SMS on a phone without EMS capability, so they can be sent to any GSM mobile phone. The messages comprise three parts: an SMS header, a User Data Header including the media being transmitted, and a 160-character SMS-compatible text message.
It can be seen from the description that follows that the facilities in EMS are still quite limited compared to what people are used to sending in emails between desktop PCs. The successor to EMS will be MMS, Multimedia Messaging Service, which will offer more powerful facilities for sending audio and graphics over GPRS and 3G mobile phone networks.
Contents of EMS
There are ten predefined sounds that can be included in EMS messages:
These are sent as codes specified in the standard, but the actual noise is implementation-dependent
Melodies are specified in the iMelody format, as notes and durations, similar to the system used for downloadable ringtones on existing mobile handsets. However, there are facilities to extend this to support polyphonic melodies (only monophonic are included initially) and other data formats such as MIDI. However, standardization is limited due to the widely varying audio capabilities of mobile phones.
Simple pictures can also be sent; each picture is a 1024-pixel block, with one bit per pixel representing either black or white. The dimensions are variable, but the maximum pixel limit must not be exceeded, giving a maximum size of 128 bytes. As an example a 32 x 32 pixel image is possible.
Animations are even more limited graphically. User-defined animations have a maximum of four 16 x 16 pixel frames. In addition, more complex predefined animations may be sent by transmitting an index number rather than an entire animation.
Styled text is another new feature, adding left/right/center alignment, three text sizes, bold, italic, underline and strikethrough.