icing all of them without making any explicit commitment on rate or any other service quality [8], while NS-based networks need to guarantee the different and heterogeneous QoS of UEs without interference among one another [10]. Hence, the best effort service model cannot be applicable directly to RAN slicing since it cannot guarantee the individual user's QoS. In the following, we will formulate the joint access control and bandwidth allocation problem in RAN slicing to meet individual UE requirements. 9.1.2 UE Association Problem Description The optimization problem in this work can be stated as: minimizing the wireless band- width consumption subject to QoS requirements, NS and BS resource constraints through joint access control and bandwidth allocation for UEs. To formulate this problem, we define a binary variable xink E {0,1}, (n,j,k) EUXSXB, where xik=1 indicates that UE n is served by NS j via BS k. We can now formulate the access control and bandwidth allocation problem as P1: P1 min , (9.0) (9.1-1) (9.1-2) (9.1-3) jes keB (9.1-4) jes KEB (9.1-5) jes keB :=1, Vn E V (9.1-6) jes KEB (9.1-7) where xink and wink are the optimization variables. Constraint (9.1-1) refers to the wired link resource constraint to guarantee that the total transmission rate offered by an NS does not exceed the link budget. Constraint (9.1-2) states the wireless bandwidth constraint, ensur- ing that the total bandwidth allocated to UEs by NS j via BS k does not exceed the wireless bandwidth budget of NS j allocated from BS k. Note that constraint (9.1-2) also ensures that UEs cannot access an NS via the BSs that cannot provide such a service. Constraints (9.1-3)-(9.1-5) guarantee that the QoS (rate and delay) of UEs can be satisfied by its serving BS and NS. Constraints (9.1-6) and (9.1-7) ensure that each UE can only access one NS via one BS at a time. 9.1.3 Admission Control Mechanisms Design for RAN Slicing We first design AC schemes to find a set of admissible UEs whose QoS can be satisfied simul- taneously. The main idea is 