The number of mobile subscribers has impressively increased during the last decade; at the same time wireless data usage continues to accelerate at an unprecedented pace even when (for developed countries) subscriber numbers reach saturation.
With the adoption of the Global System for Mobile Communication (GSM), mobile phones have become indispensable devices for voice communication and, nowadays, mobile networks are available for 90% of the world population. However, GSM was mainly designed for carrying voice traffic and some data capability was only added subsequently. The ‘mobile data explosion’ is a quite recent phenomenon driven by the introduction of the ‘Third Generation’ (3G) mobile system with Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA) and its enhancements called High Speed Packet Access Plus (HSPA+). The introduction of HSPA has marked the beginning of the transformation from voice-dominated to packet data-dominated mobile networks. These 3G evolution technologies are crucial to allow upgrading the network at relatively low costs and hence those technologies will be still important for a long period of time to come. However, it is clear that only a new Radio Access Technology (RAT) comprising a new air interface together with a new network architecture can cope with the described data explosion in the longer term. Long-Term Evolution ...