the shared spectrum: equal-rights sharing is just a special case of that. As an example of how this may be applied consider two operators - the method is appli- cable to any number of operators but using only two (i) is common in the literature and (ii) illustrates the main features. A simple way of sharing is to pre-allocate spectrum (but not specific RBs) between opera- tors in such a way that there is no overlap. A spectrum sharing ratio (SR) is then defined as the ratio between the amount of spectrum that each operator can access, However, a better solution is to allow operators to select RBs from anywhere in the whole spectrum and use the SR as a limit on the amount each may receive; this is considered in the following section. 8 Network Slicing with Spectrum Sharing It is important to note in this discussion that spectrum sharing emphasizes the need to allocate sufficient RBs (i.e. sufficient spectrum) to each user so that their connection has a large enough capacity (in the Shannon sense) for them to meet their required QoS: users achieving that QoS are termed qualified users (QUs). 8.2.1.3 Allocation of Resources RBs can be allocated to users belonging to each operator in accordance with these prede- fined rules (termed explicit spectrum sharing) or in such a way that approximates to certain SR: implicit spectrum sharing. The problem with explicit sharing is that it takes no account of the channel conditions and an uneven distribution of users within a cell may mean that those belonging to one network operator may require spectrum to achieve their required QoS than those belonging to the other. Implicit sharing [18] does not allocate RBs according to some SR but chooses how to allocate RBs to users in such a way that it maximizes the number of qualified users, but approximates to a required sharing ratio of the users between the operators. An example could be that, in every cell, the users are served in order of their channel conditions. This could mean, in extremis, that all the capacity would be allocat