ed Universal Terrestrial Radio Access (E-UTRA); Mobility Enhancements in Hetero- geneous Networks', v.11.1, 2013. [8] K. I. Pedersen, S. Barbera, P.-H. Michaelsen, and C. Rosa, 'Mobility Enhancements for LTE-Advanced Multi- layer Networks with Inter-site Carrier Aggregation', IEEE Communications Magazine, 51, 64-71 (May 2013). LTE Small Cell Optimization [9] S. Barbera, K. I. Pedersen, P.-H. Michaelsen, and C. Rosa, "Mobility Analysis for Inter-site Carrier Aggregation in LTE Heterogeneous Networks', IEEE Proceedings on VTC, September 2013. [10] V. Fernandez-Lopez, B. Soret, and K.I. Pedersen, 'Effects of Interference Mitigation and Scheduling on Dense Small Cell Networks', IEEE Proceedings on Vehicular Technology Conference (VTC-2014 Fall), September 2014. [11] B. Soret, K. I. Pedersen, N. Jorgensen, and V. Fernandez-Lopez, 'Interference Coordination for Dense Wireless Networks', IEEE Communications Magazine, 53, 102-109 (January 2015). [12] 3GPP TR 36.872, 'Evolved Universal Terrestrial Radio Access (E-UTRA); Mobility Enhancements in Hetero- geneous Networks', v.12.1, 2013. Learnings from Small Cell Deployments Brian Olsen and Harri Holma Introduction Small Cell Motivations by Mobile Operators Small Cell Challenges and Solutions Summary of Learnings from Small Cell Deployments Installation Considerations Example Small Cell Case Study Summary Introduction This chapter gives an overview of the main learnings from the small cell deployments in live networks. The results are collected from a large number of cases from multiple networks in Asia Pacific, United States and Europe. Section 9.2 discusses the small cell motivations from the operator point of view and Section 9.3 discusses the challenges. The main learnings are summarized in Section 9.4. The installation considerations are presented in Section 9.5. A small cell case study from the United States is illustrated in Section 9.6 and the chapter is summarized in Section 9.7. Small Cell Motivations by Mobile Operators The traffic volumes have grown rapidly in th