Efficient Protocol for Performance Enhancement of B4G and 5G Networks for MultiSIM Deployment

MultiSIM feature offers convenience to a user by providing connection to multiple operators for accessing different services through different SIMs with a User Equipment (UE). Generally, MultiSIM is deployed as a Dual Subscriber-Identity-Module (SIM) Dual Standby (DSDS) feature; sharing transceiver with secondary SIM (SIM-2), while primary SIM (SIM-I) is on an active data session with Operator-1. The sharing of transceiver (called tune away), causes inactivity on the Radio Link (RL) between UE and eNodeB (eNB) leading the Physical Channel Resource (PCR) wastage for Operator -1. Multi SIM Multi Standby (MSMS) feature is an enhancement over DSDS to scale up the usage with three or more SIMs with single transceiver. With MSMS deployment, PCR wastage will scale up as compared to DSDS, as it additionally introduces more challenges, like (a) increased number of tune away events due to more than two SIMs, (b) increase in tune away duration due to a cascading effect of simultaneous and back-to-back high priority procedures on secondary SIMs. MSMS will thus affect by increasing the backhaul retransmissions and buffering at Operator -1. To overcome the above challenges and to ensure MSMS is a reality soon, to the best of our knowledge for the first time, this paper proposes a new signaling via Non Access Stratum (NAS) layer, from UE to Evolved Packet Core (EPC) to indicate tune away when the duration of tune away spans several seconds. We propose to apply NAS signaling in a scenario specific manner to address tune away events. Through extensive simulation derived from mathematical modeling and measurements obtained from test bed with commercial UEs, the results reveal that for three SIMs in cascaded scenarios, with the proposed solution, the PCR wastage is reduced to only 7.9 % against 48.5% and eNB buffering reduced by 95% in comparison to the available literature for a practical deployment.