Novel C-DRX Mechanism for Multi SIM Multi Standby UEs in 5G and B5G Networks

Multi SIM (Multi Subscriber Identity Module) Multi Standby (MSMS) feature-enabled User Equipments (UEs) hold a big share in the mobile market and expected to dominate the smartphone industry for the next decade too. Predominantly, MSMS UEs are designed with a single Radio Frequency Integrated Circuit (RFIC) to save cost and to serve the Protocol Stack Unit (PSU) of each SIM in a time-sliced manner. As a result, the amount of time RFIC is kept powered ON is higher in MSMS UEs than that in single SIM UEs and it increases with an increase in SIM count in MSMS UEs. This increased RFIC usage leads to more power consumption inherently causing a much faster battery drain compared to single SIM UEs. Connected mode Discontinuous Reception (CDRX) is a power-saving technique in 5G where networks attempt to bring a balance between Quality of Service (QoS) and power consumption. Based on the traffic pattern, 5G networks predict the RFIC usage pattern and compute the CDRX configuration for the single SIM UEs. For MSMS UEs, the network connected to SIM-1 cannot determine the optimal DRX configuration as it cannot predict the RFIC usage of all the SIMs based on the SIM-1 traffic pattern. To address the above-said problem, we propose a novel mechanism called UCM (UE defined C-DRX for MSMS UEs) in this paper. UEs shall optimally compute C-DRX configuration based on overall RFIC ON duration considering the events of other SIMs too and share it with 5G networks. Key Performance Indicators (sleep ratio and mean packet buffering delay) of the new CDRX mechanism are qualitatively compared with the legacy. Results reveal that UCM achieves better power saving with little increase in packet latency.