 of packets being provided from the physical layer and MAC layer to RLC. Medium Access Control (MAC) covers functions such as control of discontinuous reception and transmission, timing advance signalling, scheduling and retransmission handling and UE buffer and transmission power headroom reporting. Release 9 was rather small step in terms of radio capabilities for LTE, as there was no increase in peak data rate, rather bringing smaller enabler such a emergency call prioritization or position location-related measurement, both important for the introduction of the VoLTE functionality in LTE, as elaborated in more details in Reference 2. From the physical layer point of view, a new Transmission Mode 8 (TM8) was added to enable the use of multi-stream MIMO operation when using beamforming operation. This was especially relevant for those LTE TDD deployments where eight-port beamforming antenna is being used. 2.3 LTE Advanced in Releases 10 and 11 Release 10 introduced the first LTE-Advanced release, bringing clear increase for the data capabilities of LTE networks. Both the average achievable data rates and the peak data rate were increased. The key technologies introduced with Releases 10 and 11 LTE Advanced are as follows: Carrier aggregation, enabling the UE to receive and transmit signals using more than one carrier in downlink and uplink direction. Evolved MIMO operation, with more efficient reference signal structures and support for use of up to eight transmit and eight receiver antennas in the downlink direction. Improved support for heterogeneous network operation, especially for the co- operation from multiple transmitters or receivers with CoMP, as introduced in Release 11. There were also further enhancements in Releases 10 and 11 than the ones related to the LTE Advanced. Release 13 work on low-cost MTC is utilizing the Release 11 Enhanced PDCCH, which allows to have also the downlink signalling send with part of the downlink spectrum only and not like in Release 8 using the full system bandwidth. Enh