e for small cells in the 3.5 GHz band where there is more spectrum available. By default, all the small cells utilize all the available CCs (i.e. reuse one strategy). The small cells monitor the throughput offered for each user, and only if the throughput is found to fall below the promised GBR is the ICIC framework triggered. The example pictured in Figure 8.18 shows a situation where the UE no. 1 served by small cell no. 1 is detected as a victim user, as the network is unable to serve it the promised GBR. In this example, each small cell can use up to four CCs, where used CCs are indicated with grey background colour. As only small cell no. 1 is using three of the available CCs, it can choose to enable CC3 to increase the available bandwidth. It can also decide to request some of the interfering small cells to mute certain CCs to reduce the generated interference. For each of the possible hypothesis to improve the performance of the victim user (UE no. 1) above its GBR, the UE no. 2 Small cell no. 3 Small cell no. 1 UE no. 4 UE no. 1 Small UE no. 3 cell no. 2 Figure 8.18 Basic principle of carrier-based ICIC. Solid lines indicate serving cell links, while the dashed lines are interfering links Small Cell Optimization corresponding value (benefit minus cost) is estimated, followed by implementing the action that results in the highest value. The hypothesis corresponding to taking more CCs into use for small cell no. 1 will result in benefit for that cell, but also a potential cost in the neighbouring cells that will experience interference from the CC. Similarly, if a CC is switched off in small cell no. 2 it will result in a performance loss (cost) for UE no. 3, while UE no. 1 and UE no. 4 will experience less interference (benefit). In the interest of complexity, not all the possible hypotheses need to be evaluated, but only those that involve neighbouring cells that act as dominant interferer for the identified victim user. Only hypotheses that result in a positive value without causing other users to fall b