A control theoretic approach to achieve proportional fairness in 802.11e EDCA WLANs

This paper considers proportional fairness amongst ACs in an EDCA WLAN for provision of distinct QoS requirements and priority parameters. A detailed theoretical analysis is provided to derive the optimal station attempt probability which leads to a proportional fair allocation of station throughputs. The desirable fairness can be achieved using a centralised adaptive control approach. This approach is based on multivariable statespace control theory and uses the Linear Quadratic Integral (LQI) controller to periodically update CWmin till the optimal fair point of operation. Performance evaluation demonstrates that the control approach has high accuracy performance and fast convergence speed for general network scenarios. To our knowledge this might be the first time that a closed-loop control system is designed for EDCA WLANs to achieve proportional fairness

UAV-enabled wireless power transfer with base station charging and UAV power consumption

Wireless power transfer (WPT) is a promising charging technology for battery-limited sensors. In this paper, we study the use of an unmanned aerial vehicle (UAV) as a charger for WPT. Unlike the previous works, our study takes into account the power consumption of the UAV (power consumption during hovering and flight), the charging process from a base station (BS) to the UAV and the conversion loss of the energy harvester. Both one-dimensional (1D) and two-dimensional (2D) WPT systems are considered. The sum-energy received by all sensors is maximized to find the optimal strategy for UAV deployment. Two different charging schemes are proposed. Numerical results show that the sum-energy received by all sensors is determined by sensors' topology, the flight speed of the UAV and the transmit power. They also show that, when the BS charging process and the UAV power consumption are considered in the optimization, the optimal location of the UAV in the 1D and 2D WPT systems is closer to the BS than in the previous works that ignore these two practical factors

1,4-Ditosyl-1,4-diazepane

In the title compound, C19H24N2O4S2, the dihedral angle formed by the benzene rings is 82.88 (7)°, and the mol­ecular conformation is enforced by weak intra­molecular C—H⋯O contacts. Two C atoms of the 1,4-diazepane ring are disordered over two sets of sites with a refined occupancy ratio of 0.534 (13):0.466 (13). In the crystal, mol­ecules are linked by weak inter­molecular C—H⋯O inter­actions into chains parallel to the a axis

Analysis of power consumption for different sensor access modes

This paper focuses on analysis of the power consumption of wireless sensor nodes with heterogeneous multi-sensors. The power consumption is investigated in three sensor access modes: serial access mode, parallel convert mode, and event driven mode. The mathematic models of the power consumption in these sensor access modes are established and evaluated in the paper. In terms of the solutions of wireless sensor nodes provided by Crossbow and Jennie, etc., a general framework of a wireless sensor node is proposed as well. The work can be used to guide the design of control system of a wireless sensor node