why small cells will be deployed. All this data growth must happen without increase in the operator revenues. Therefore, the cost per bit must decrease and the network efficiency must increase correspondingly. LTE Small Cell Optimization Mobile data growth during 2-year period from 2012 to 2014 Figure 1.4 Mobile data growth during 2-year period 1.4 LTE Technology Evolution The LTE technology has been standardized by Third Generation Partnership Project (3GPP). The LTE was introduced in 3GPP Release 8. The specifications were completed and the backwards compatibility started in March 2009. Release 8 enabled peak rate of 150 Mbps with 2x2 MIMO, low latency, flat network architecture and the support for 4-antenna base station transmission and reception. Release 8 enabled in theory also 300 Mbps with 4x4 MIMO but the practical devices SO far have two antennas limiting the data rate to 150 Mbps. Release 9 was a relatively small update on top of Release 8. Release 9 was completed 1 year after Release 8 and the first deployments started during 2011. Release 9 brought enhanced Multimedia Broadcast Multicast Solution (eMBMS) also known as LTE-Broadcast, emer- gency call support for VoLTE, femto base station handovers and first set of Self-Organizing Network (SON) functionalities. Release 10 provided a major step in terms of data rates and capacity with Carrier Aggregation (CA), higher order MIMO up to eight antennas in downlink and four antennas in uplink. The support for Heterogeneous Network (HetNet) was included in Release 10 with the feature enhanced Inter-Cell Interference Coordination (eICIC). Release 10 was completed in June 2011 and the first commercial carrier aggrega- tion network started in June 2013. Release 10 is also known as LTE-Advanced. Release 11 enhanced LTE-Advanced with Coordinated Multipoint (CoMP) transmission and recep- tion, with further enhanced ICIC (feICIC), advanced UE interference cancellation and carrier aggregation improvements. First Release 11 commercial implementation was available durin