y planned macro-only deployments to HetNet deployments with denser and denser small cell installations. The deployment of small cells such as pico cells and micro cells poses new challenges. The use of interference mitigation techniques, therefore, plays an important role when deploying small cells to fully maximize the benefits of such investments. Interference mitigation comes in many different forms as summarized in Table 7.1, where the main options offered for LTE are listed. On the network side, neighbouring interfering cells can use different forms of resource partitioning to reduce co-channel interference. Among such options, higher order sectorization and coordinated beamforming implement resource partitioning in the spa- tial domain and are typically considered feasible for macro eNodeBs that can be equipped with the required number of antennas to enable such solutions. Resource partitioning in the time and/or frequency domain is another option, where especially coordinated time-domain muting LTE Small Cell Optimization: 3GPP Evolution to Release 13, First Edition. Edited by Harri Holma, Antti Toskala and Jussi Reunanen. © 2016 John Wiley & Sons, Ltd. Published 2016 by John Wiley & Sons, Ltd. LTE Small Cell Optimization Table 7.1 3GPP options for downlink interference mitigation Network-based Spatial-domain resource Spatial filtering techniques such as higher order resource partitioning sectorization and coordinated beamforming partitioning Time-domain resource Also known as coordinated muting. Examples partitioning include 3GPP-defined techniques such as eICIC and (e)CoMP Frequency-domain resource The frequency-domain resource partitioning can partitioning be done on PRB resolution or on carrier resolution if having networks with multiple carriers. Includes options such as using hard or soft frequency reuse between neighbouring cells Network-based Transmit power control per Adjustment of transmit power per cell to improve transmit power the interference conditions. Includes control 3GPP-defined femtocel