Wireless Messaging Demystified – SMS, EMS, MMS, IM, and others by Donald Longueuil provides a very good history of SMS, EMS and MMS. Wikipedia also has very good sections detailing the history of SMS and MMS.
In a nutshell, when SMS (Short Messaging Service) was first introduced in the late 1990s it was only conceived as a means for mobile subscribers (a.k.a. users) to send short messages (hence Short Message Service) of length 140 bytes (or 160 chars using the 7bit GSM encoding) to each other. However, as such peer-to-peer usage grew and people started to get familiar with using this technology, more and more companies (especially start-ups) started building applications around this new technology. Such apps ranged from telling your future told to purchasing a can of Coke by sending a SMS.
It was with the introduction of ringtones sent via binary SMSs, the market for SMS apps boomed. Initially, the only way for an app to send and receive SMSs was to hook up directly to the operator’s SMSC (or SMS Center). However, as the number of apps grew, operators scrambled to build app gateways to interface with apps. There were several good reasons for this – (a) operators needed a means to control the apps and not have them interface directly with the operator network (b) SMSCs were not cheap and each only had a fixed number of login accounts – enabling the sharing of such accounts meant lowering the cost per app (c) SMS protocols were difficult for app developers to implement and troubleshoot – HTTP based protocols were much easier and were closer to what developers were used to.
Unfortunately this didn’t really solve the app developer’s real problem – that of seamless and easy distribution. In fact it made the problem worse since nearly every operator developed their own version of the HTTP protocol. What was needed was an intermediary that provided a single protocol and hooked up to all the operators – these were the Messaging Aggregators or Aggregators in short.
Somewhere along the way, in order to get more usage (and revenues) out of SMS – EMS (or Enhanced Messaging Service) was introduced. This was a technology that used the existing SMS infrastructure to send images, animations, sounds and formatted messages. This was achieved by sending concatenated binary SMSs (up to 255 of them) and then having the handset reassemble them into a single file – and displaying (or playing) it.
The drawbacks of EMS were that it both took a while for all the SMSs to arrive and there was a limit to the number of SMS “packets” that could be used thus limiting the file size. Thus with the advent of 3G, another new technology – MMS or Multimedia Messaging Service – was introduced. This used the MIME format for messages which can contain images (GIF, JPG), audio clips (MP3, MIDI) and vCards. However, at a time where bucket plans (for SMS) were the norm, the high cost of MMS and the relatively limited uses of this technology meant that it would remain a niche market and with the introduction of smart phones (eg. iPhone) that come with cheap data plans, MMS usage has plummeted.
Interestingly, while MMS and EMS have languished, SMS is still widely used as a means to send bookmarks, chat, alerts etc and looks to remain a mainstay of mobile communications.