The popularity of handheld devices, which are usually powered by batteries, has made power saving an important and practical issue in recent years. Techniques of power saving for user devices using mobile communication systems such as WiMAX and LTE (Long-Term Evolution) are parts of the major focuses in the literature. In this paper, two revised schemes of the authors' previously proposed power saving schemes for IEEE 802.16 are proposed to be applied in LTE. The proposed schemes, namely LTE-LBPS-Aggr and LTE-LBPS-Merge, estimate the input load by traffic measurement and the channel capacity by channel quality indicator (CQI) reports, calculate the length of the sleep cycle, and notify related user equipments (UEs) of the next radio-on time for receiving data. The difference between LTE-LBPS-Aggr and LTE-LBPS-Merge lies in the grouping of UEs for sleep scheduling. LTE-LBPS-Aggr treats all UEs in a group, while LTE-LBPS-Merge allows multiple groups of UEs in sleep scheduling. The simulation study shows that in comparison with standard-based mechanisms, the proposed schemes can achieve better power saving efficiency at the cost of moderate increase on delays and the signaling overhead.
By introduction of relay nodes, LTE-Advanced can provide enhanced coverage and capacity at cell edges and hot-spot areas. The authors have been researching the issue of power saving in mobile communications technology such as WiMax and Long Term Evolution (LTE) for some years. Based on the previous idea of load-based power saving, two strategies each with associated schemes to integrated relay nodes and user equipment in power saving are proposed in the paper. Simulation study shows the benefit of the proposed schemes in terms of better power saving than the standard-based scheme at the cost of moderately increased delay. Extended discussion about the impact of different load distribution among user equipments and the impact of a worse backhaul link on power saving is also presented in the paper.
Long-Term Evolution (LTE) is a 4G wireless broadband technology developed bythe Third Generation Partnership Project. Two duplex modes, namely, frequency division duplex and time division duplex (TDD), are defined in LTE for transmission in both downlink and uplink directions simultaneously. Power saving mechanisms for LTE-frequency division duplex were proposed in the authors' previous work. Applicability of the previously proposed mechanisms to LTE-TDD is investigated in this paper, and the idea of "virtual time" associated with the mapping mechanism from the virtual time domain to the actual time domain for different TDD configurations is proposed. With the help of the mapping mechanism, 3 revised power saving schemes are proposed to support real-time user equipments and nonreal-time user equipments in LTE-TDD. Simulation study demonstrates the effectiveness of the mapping mechanism as well as the benefit of the proposed schemes in power saving efficiency and real-time support in comparing with the standard-based mechanism.
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