Accurate Modeling of the DRX Mechanism with Predetermined DRX Cycles Based on the 3GPP LTE Standard

In Long Term Evolution-Advanced (LTE-A), the Discontinuous Reception (DRX) mechanism conserves the power of a User Equipment (UE) by monitoring the UE’s downlink channels for a specific period and turning off the UE’s radio when no packets arrive during the period. There has been heated discussion in previous studies, but most previous models of DRX operation are partially inconsistent with the LTE-A specifications. The reason is that the previous models hold the assumption that a new DRX cycle starts after an expiration of a drx-InactivityTimer or a period of continuous reception. This assumption causes undetermined DRX cycles and fixed-length sleep time in a UE in a DRX mechanism. However, the drx-InactivityTimer expiration can occur at any instant within a DRX cycle, which causes the variable-length sleep time. In this paper, we first propose a novel analytical model fitting for the specification DRX mechanism by using a semi-Markov process. Two key performance indicators affected by the DRX mechanism, the power saving factor and the average buffering delay of radio-off periods, are derived. We also prove the feasibility of the proposed model with stability analysis. Finally, the analytical results are validated against the simulation results and show the effects of different DRX configurations for the Poisson arrival process.