Search

Summary: The rapid growth and innovation of the various mobile communication technologies have caused a change in the paradigm of Internet access. In next‐generation mobile system, which is also known as fifth‐generation (5G) network, all user connections are expected to be heterogeneous in nature. Hence, an intelligent mobility management mechanism is essential to satisfy the requirements of lower latency, less power consumptions, and last but not least, possible uninterrupted ongoing session when a user equipment (UE) moves across network boundaries. On the other hand, device‐to‐device (D2D) communication has been proposed as a promising technology to boost the network performance in 5G. The issue related to mobility management for D2D communication in 5G heterogeneous network environments has attracted attention from academic society. In this paper, we leverage on IEEE 802.21 Media Independent Service (MIS) and propose a new framework, enhanced version of IEEE 802.21 MIS that supports D2D communication (E‐MIS‐D2D) to enhance D2D mobility experience over heterogeneous networks. Moreover, a load‐aware mode selection algorithm is proposed for selecting the best target mode. Through extensive simulation studies, we validate that the proposed method outperforms the existing methods in terms of packet loss ratio, average throughput, latency, bandwidth usage, and load rate of Evolved Node B (eNB). [ABSTRACT FROM AUTHOR]

Wireless body area networks (WBANs) have attracted great attention from both industry and academia as a promising technology for continuous monitoring of physiological signals of the human body. As the sensors in WBANs are typically battery-driven and inconvenient to recharge, an energy efficient resource allocation scheme is essential to prolong the lifetime of the networks, while guaranteeing the rigid requirements of quality of service (QoS) of the WBANs in nature. As a possible alternative solution to address the energy efficiency problem, energy harvesting (EH) technology with the capability of harvesting energy from ambient sources can potentially reduce the dependence on the battery supply. Consequently, in this paper, we investigate the resource allocation problem for EH-powered WBANs (EH-WBANs). Our goal is to maximize the energy efficiency of the EH-WBANs with the joint consideration of transmission mode, relay selection, allocated time slot, transmission power, and the energy constraint of each sensor. In view of the characteristic of the EH-WBANs, we formulate the energy efficiency problem as a discrete-time and finite-state Markov decision process (DFMDP), in which allocation strategy decisions are made by a hub that does not have complete and global network information. Owing to the complexity of the problem, we propose a modified Q-learning (QL) algorithm to obtain the optimal allocation strategy. The numerical results validate the effectiveness of the proposed scheme as well as the low computation complexity of the proposed modified Q-learning (QL) algorithm. [ABSTRACT FROM AUTHOR]

Poor ionic and electronic conductivities are the key issues to affect the electrochemical performance of Li 2 ZnTi 3 O 8 (LZTO). In view of the water solubility, low melting point, good electrical conductivity, and wettability to LZTO, Na 2 MoO 4 (NMO) was first selected to modify LZTO via simply mixing LZTO in NMO water solution followed by calcining the dried mixture at 750 °C for 5 h. The electrochemical performance of LZTO could be enhanced by adjusting the content of NMO, and the modified LZTO with 2 wt % NMO exhibited the most excellent rate capabilities (achieving lithiation capacities of 225.1, 207.2, 187.1, and 161.3 mAh g -1 at 200, 400, 800, and 1600 mA g -1 , respectively) as well as outstanding long-term cycling stability (delivering a lithiation capacity of 229.0 mAh g -1 for 400 cycles at 500 mA g -1 ). Structure and composition characterizations together with electrochemical impedance spectra analysis demonstrate that the molten NMO at the sintering temperature of 750 °C is beneficial to diffuse into the LZTO lattices near the surface of LZTO particles to yield uniform modification layer, simultaneously ameliorating the electronic and ionic conductivities of LZTO, and thus is responsible for the enhanced electrochemical performance of LZTO. First-principles calculations further verify the substitution of Mo 6+ for Zn 2+ to realize doping in LZTO. The work provides a new route for designing uniform surface modification at low temperature, and the modification by NMO could be extended to other electrode materials to enhance the electrochemical performance.