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

Multirate control in internet-based control systems

One of the major challenges in Internet-based control systems is how to overcome the Internet transmission delay. In this paper, we investigate the potential of using the multirate control scheme and the time-delay compensation to overcome the Internet transmission delay. A two-level hierarchy is used for the Internet-based control systems.At the lower level, a local controller is implemented to control the plant at a higher frequency. At the higher level, a remote controller is employed to remotely regulate the desirable set-point at a lower frequency for the local controller. A compensator located at the feedback channel is designed to overcome the time delay occurring in the transmission from the local site to a remote site. Another compensator in the feedforward channel is designed to compensate the time-delay occurring in the control action transmission. The simulation and experimental application results illustrate that the multirate control scheme with the time delay compensation offers a promising way to efficiently reduce the effect of Internet time delay on control performance

RFID based automatic speed limit warning system

Speeding is one of the major causes of road accidents. As drivers usually claim they exceed the speed limit unintentionally, having an in-vehicle automatic speed limit warning system could help to prevent a significant number of speeding and accidents from happening. Existing systems cannot provide consistent and satisfactory performance. In this paper we investigated automatic speed limit transmission based on RFID technologies. We conclude that both passive and active RFID systems show potential in such scenario, but are suitable for different scales of applications. For both technologies, challenges are identified and addressed, with system prototypes proposed and demonstration systems developed to prove the feasibility of our design concept

Connectionless indoor inventory tracking in Zigbee RFID sensor network

Abstract: Zigbee is one of the most exciting wireless sensor network (WSN) technologies for monitoring and control. In our previous research, an integrated Zigbee RFID sensor network was designed as an ‘all-in-one’ system solution for Humanitarian Logistics Center (HLC) resource management. Various field trials, which have justified the feasibility and features of such a system structure, have also revealed the requirement for simple yet reliable mobile tracking architecture for Zigbee network. In this paper a connectionless tracking architecture based on Zigbee RFID sensor network is proposed for inventory management applications. Such architecture features a consistent network structure, low hardware energy consumption and no accumulated error for localization algorithms with the least additional cost and hardware required on top of the existing Zigbee RFID sensor network systems. A simple demo system is also developed to demonstrate the feasibility of our design

Indoor localization systems-tracking objects and personnel with sensors, wireless networks and RFID

Advances in ubiquitous mobile computing and rapid spread of information systems have fostered a growing interest in indoor location-aware or location-based technologies. In this paper we will introduce the primary technologies used in indoor localization systems by classifying them in three categories: Non-RF technologies, Active-RF technologies and Passive-RF technologies. Both commercialized products and research prototypes in all categories are involved in our discussion. The Passive-RF technologies are further divided into “Mobile tag” and “Mobile reader” systems. We expect such classification can cover most of the indoor localization systems. Features of these systems are briefly compared at the end of this paper

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

A Benchmarking Model for Household Water Consumption Based on Adaptive Logic Networks

Household water benchmarking is an important step in evaluating a household's water usage and comparing it with similar house- holds. It can provide an indicator if a household consumes more water than usual during a certain period of time or some households consume more than other similar households in a particular region. This paper proposes a benchmarking model for household water consumption based on Adaptive Logic Networks (ALNs). Real world data collected by a water consumption monitoring system installed in Sosnowiec, Poland and Skiathos, Greece is respectively used to build a model for each city. The results indicate that the developed models can successfully prediction for a particular use purpose