e time of writing this book in mid 2015, with the Releases 12 and 13 features covered mostly in the Chapters 3 and 4 to follow in the marketplace in the next phase. While there are over 300 networks with LTE Release 8 rolled out to the market place, already more than 50 networks [6] have rolled-out LTE Advanced, mostly based on Release 10 downlink carrier aggregation. References [1] Holma, H. and Toskala, A., HSPA, John Wiley & Sons, Ltd (2014). [2] Poikselkä, M., Holma, H., Hongisto, J., Kallio, J., and Toskala, A., Voice Over LTE (VoLTE), John Wiley & Sons (2012). [3] 3GPP Tdoc RP-RP-091440, 'Work Item Description: Carrier Aggregation for LTE', December 2009. [4] 3GPP Technical Specification, TS 36.101, 'Evolved Universal Terrestrial Radio Access (E-UTRA); User Equip- ment (UE) Radio Transmission and Reception', Release 12, Version 12.6.0, December 2014. [5] Holma, H. and Toskala, A., LTE Advanced: 3GPP Solution for IMT-Advanced, John Wiley & Sons (2012). [6] www.gsa.com (accessed March 2015). LTE-Advanced Evolution in Releases 12-13 Antti Toskala Introduction Machine-Type Communications Enhanced CoMP FDD-TDD Carrier Aggregation WLAN-Radio Interworking Device-to-Device Communication with LTE Single Cell Point to Multipoint Transmission Release 12 UE Capabilities Conclusions References 3.1 Introduction This chapter covers summary of Release 12 and 13 enhancements outside the big themes such as small cells, macro cell evolution or LTE-unlicensed. The topics covered in this chapter are Machine-Type Communications, enhanced CoMP with non-ideal backhaul, FDD-TDD carrier aggregation, WLAN interworking as well as device-to-device (D2D) operation intended both for public safety and commercial use cases. Machine-Type Communications One of the use cases for mobile communications is Machine-Type-Communication (MTC), also known as Machine-To-Machine (M2M) or as Internet of Things (IoT). A typical use case LTE Small Cell Optimization: 3GPP Evolution to Release 13, First Edition. Edited by Harri Holma, Antti Toskala and Juss