Enhanced messaging service (EMS) is (obviously) an enhancement of SMS. The service is provided by making use of a similar network infrastructure as SMS. In addition to text, EMS supports the sending and delivery of black-and white pictures and sound. Three formats are supported, i.e., 16 x 16 pixels, 32 x 32 pixels, and 96 x 64 pixels (the standard). EMS messages may be enhanced with graphics, and text may be formatted as boldface, italics, justified alignment, and so on. EMS also allows a message to interact more closely with the phone by incorporating music and by facilitating the delivery of complex ringing tones. The standard for defining sounds is iMelody, which is a text-based melody representation specified by the Infrared Data Association (IrDA). In addition to 10 predefined sounds, user -defined sounds can also be transported over the air and each is up to 128 bytes in size . With its expanded capabilities, EMS makes messaging more useful for mobile users, particularly business users, who may use it to transfer rich content for tasks such as arranging meetings, collaborating on draft documents, and more. Braue (2001) says that it will provide a far richer medium for mobile advertising, potentially doing for one-to-one marketing what the graphical Web browser did for the World Wide Web.
The next step in the evolution is multimedia messaging service (MMS), which allows users to send not only text messages but also images, audio, and video. MMS does not require a new network infrastructure ( assuming a GPRS or 3G bearer service is already in place), but users who wish to utilize this service will have to have MMS-compliant terminals. The designers of MMS aim to make MMS not only backward compatible but also forward compatible. One way of achieving this is by making access to MMS service independent of access point ‚ it is accessible through 2G and 3G networks, fixed networks, the Internet, etc.
Given the slow signaling channel of the current wireless network's infrastructure, supporting audio and video might be problematic as audio and video put a higher demand on bandwidth. Service providers need to determine how they can provide interactive audio and video that is of acceptable quality to users given the restriction on bandwidth. Another issue that must also be addressed is power conservation. Mobile devices with color screens will certainly consume more power, resulting in a shorter time span between recharging; thus, serious consideration should be given to power management.
An important issue that must be addressed, especially for SMS applications involving e-commerce, is security. Customers and companies need to be certain of the integrity of data that they send/receive. For example, customers need to be certain that the information they send is received only by the intended recipient, while companies need be certain that customer data are protected from theft. Any compromise on the data sent/received may cause customers to lose confidence in the company.