17 [49] under the author copyright agreement of the IEEE. 8 Network Slicing with Spectrum Sharing Isolation Isolation is seen as the key in providing effective slicing and is defined as "The operator shall be able to operate different network slices in parallel with isolation that, for example, prevents one slice's data communication to negatively impact services in other slices" [23]. In the RAN, isolation is affected by interference. Unless a frequency resource factor 1 is used, there will be co-channel ICI and, depending on the slicing structure, this may gener- ate co-channel interference between slices. If the ICI reduces the SINR of an existing user to such an extent that can no longer meet its QoS requirements, then there is no isola- tion. Hence, it is necessary to consider the effect of ICI on the different resource allocation approaches. This can be exacerbated by movement of users and changing channel condi- tions leading to changes in ICI. With fixed allocation there is no impact between slices but there will be ICI that leads to intra-slice interference (Figure 8.15a). However, with fully dynamic allocation inter-slice interference may occur as well (Figure 8.15b) as the co-channel interference may be between users allocated to different slices. Although this is not a problem in lightly loaded networks, as more users are admitted it becomes difficult to allocate spectrum SO that there is no ICI, and the purpose of this section is to show how the effects of the ICI can be mitigated in order to achieve isolation. The literature generally considers inter-slice isolation: the isolation of a slice from the effects of other slices in another cell, but there is also implicit isolation that is applicable to a sharing environment. This means that instead of a physical separation [23], suitable radio resource management can be used to ensure that any change in one slice should not lead to deterioration in the QoS of users in that slice or in other slices in neighboring cells. It is noted in Foukas et al. [50] 