Performance Evaluation of LTE eSRVCC with Limited Access Transfers

Long Term Evolution (LTE) evolved from Universal Mobile Telecommunications System (UMTS), which utilizes IP Multimedia Core Network Subsystem (IMS) to provide voice service. In most existing commercial operations, the LTE networks provide zonal coverage as compared with UMTS networks which provide full service coverage. A User Equipment (UE) can initiate or receive an IMS call in either LTE or UMTS. The UE uses LTE whenever it is available. If LTE is out of service, then the UE is transferred to UMTS. To support access transfer between LTE and UMTS during an IMS call, 3rd Generation Partnership Project (3GPP) proposed Enhanced Single Radio Voice Call Continuity (eSRVCC). If the UE frequently moves back and forth between LTE and UMTS during an IMS call, it may incur large access transfer traffic. To resolve this issue, we propose the limited access transfer algorithm that limits the number of access transfers in an eSRVCC call (referred to as the transfer limit) to reduce the transfer traffic. An analytic model is proposed to investigate the performance of the limited access transfer algorithm. Our study indicates that the selection of the transfer limit is not a trivial issue, and an appropriate transfer limit effectively reduces the access transfer traffic to enhance the LTE call control performance.