cific BS, say BS k, we use Sk to denote the set of NSs supported by BS k. We identify a specific NS, say NSj, by transmission rate, delay, and the resource allocation in core and access networks. Specifically, besides the slice ID, four elements (Rj, Dj, Aj, Bj) are used to identify the j-th slice, where R and D respectively denote the minimum trans- mission rate and the maximum delay that NS j can provide to its serving UEs, Aj denotes the bandwidth allocated to NS j in the core network, and Bi is a vector denoting the wireless bandwidth allocation of NS j from all BSs. Let bck) be the k-th element of vector Bj denoting the bandwidth of NS allocated by BS k. when BS k is not in the coverage of NSj For a specific UE, say UE n with qn volume data to transmit, the QoS can be described by two metrics: transmission rate I'n and delay dn [9]. Thus, NS j is admissible for UE n only if Rj rn and Dj<dn. We now study the two QoS metrics respectively. Let risk be the transmission rate of UE n served by NS j via BS k. For simplicity, we use Shannon theory to define the transmission rate, i.e. rink = wn log2(1 + SINR), where wik is the wireless bandwidth that BS k allocates to the UE n served by NS j, and SINR is the signal-to-interference-plus-noise-ratio (SINR) between UE n and BS k. We use dn=qn/rn to denote the delay in RAN of UE n served by NS j via BS k. Thus, combined with the delay in core network, the end-to-end delay can be approximately calculated as dink - Dj. Note that more sophisticated and accurate transmission rate and delay models can be used here. However, these do not affect the following derivations. This is because the models in this work may affect the absolute value of bandwidth consumption, but do not invalidate the relative performance enhancement of our proposed policies. Traditional networks usually provide the best effort service model to users [8]. In this model, the network allocates resources among all of the active UEs and attempts to serve 9 Access Control and Handoff Policy Design for RAN Sl