Abstract-The Long Term Evolution (LTE) standard specifies the Discontinuous Reception Mechanism (DRX) mechanism for saving power at the User Equipment (UE). Here, a UE switches off its RF circuitry when there are no packets to be transmitted or received. The existing DRX algorithms use static operational parameters that are determined by the evolved nodeB (eNB) at the start of a UE's session. During the switch-off period, packets destined to the UE are buffered in the eNB leading to higher packet latency. This paper presents two adaptive algorithms to dynamically adjust the DRX parameters, in order to reduce both energy consumption and the extra delay incurred. The algorithms use application Quality-of-Service and channel quality information to adjust the DRX parameters. ns3-based simulation performance studies show that the algorithms are able to reduce packet delay compared to static DRX by up to 60%, 60% and 75% and reduce energy consumption by up to 75%, 43% and 90% for video streaming, VoIP and bursty data applications respectively. I. INTRODUCTIONLong Term Evolution (LTE) is a fourth generation wireless technology, designed to provide data rate and reduced latency to users [1]. LTE uses advanced physical layer techniques that lead to increased power consumption of the User Equipment (UE). The LTE standards have proposed the Discontinuous Reception mechanism (DRX) method to save battery power by enabling the UE to switch off its RF circuitry in the absence of packets for transmission and reception. Despite the use of DRX, an LTE UE is about 23 times less power efficient compared to WiFi and even worse compared to 3G [2]. Hence, there is a need to improve the operation of DRX for better power savings.A DRX-enabled UE listens to the downlink control channel at intervals determined by DRX parameters that are established by the base station, i.e. evolved NodeB (eNB), at the time of session establishment. The parameters include DRX short cycle, DRX long cycle, and DRX Inactivity Timer. These timers have a significant impact on power savings and the delay incurred by the UE applications. When the UE is in sleep mode, the packets intended for the UE get buffered at the enodeB till the UE returns to active mode. If the UE follows a long sleep cycle, it can save more power; however, the delay incurred by the application also increases. Similarly, the channel quality experienced by the users will also impact when, and for how long, the UE has to remain awake to receive the packets. A high channel quality implies a longer sleep time and vice-versa. Thus, there is a need to update the DRX parameters so that the trade-off between the power savings and the application delay is well-balanced.
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