With the introduction of 5G New Radio (NR), telecom operators are planning to integrate network elements of NR in different configurations for a phased and overlaid deployment and coexistence with 4G. Third Generation Partnership Project (3GPP) standardizes the deployment operation mode of the next-generation network, viz. working in Stand Alone (SA) NR scenarios and Non-Stand Alone (NSA) NR mode scenarios. As defined in the specification, Option 7 is where UE connects to 5G Core Network (5GCN) via either 4G enhanced Node B (eNB) cell or 5G next-generation NodeB (gNB) cell. The power consumption for a User Equipment (UE) is dependent on the physical resource allocation strategy in the serving cell. Available procedures of system selection defined in 3GPP are based on measurement of reference signal power levels and priority criteria as defined in the System Information of the 5G/4G network. In this paper, we have discussed novel protocol and algorithm through which the UE maintains a history of availability of features like Semi-Persistent Scheduling (SPS), Connected Mode Discontinuous Reception (CDRX) and Voice over NR (VoNR) in the serving area of a cell and uses this information later during system reselection evaluation due to mobility. Through our proposed changes, a UE a) gets VoNR service more often and b) conserve more energy when the user activates VoNR service. We present an analytical model and through simulation show that during VoNR service, power is conserved due to SPS and CDRX on the selected cell.
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