Research on road topology based mobility prediction schemes

Geographic routing has been introduced in mobile ad hoc networks and sensor networks. But its per-formance suffers greatly from mobility-induced location errors that can cause Lost Link （LLNK） and LOOP problems. Thus various mobility prediction algorithms have been proposed to mitigate the errors, but sometimes their prediction errors are substantial. A novel mobility prediction technique that incorpo-rates both mobile positioning information and road topology knowledge was presented. Furthermore, the performance of the scheme was evaluated via simulations, along with two other schemes, namely, Linear Velocity Prediction （LVP） and Weighted Velocity Prediction （WVP） for comparison purpose. The results of simulation under Manhattan mobility model show that the proposed scheme could track the movement of a node well and hence provide noticeable improvement over LVP and MVP.

A New MAC Protocol for Moving Target in Distributed Wireless Sensor Networks

A wireless sensor network (WSN) is composed of many nodes with limited power supply;most nodes are stationary in the network which could probably involve a few mobile nodes. Various medium access control (MAC) protocols specially aimed at a target locating application for WSNs have been proposed. However, most of these protocols based on the problem of energy-limited does not consider the mobility of nodes. Therefore, in order to solve such problem, this paper proposes a MAC protocol—Distribute Moving-MAC (DM-MAC). Under the condition of keeping high network coverage, the protocol utilizes the redundancy of nodes to strengthen the robustness and energy efficiency of network, and decreases the packet loss rate of the mobile node’s communication links for realizing reliable communication of two nodes. Simulation indicates that the new protocol has higher energy efficiency, lower packet loss rate and higher network coverage which suit for wireless sensor network with mobile nodes well.

Retarded Harrier Maneuver as a New and Efficient Approach for Fixed-Wing Aircraft to Achieve S/VTOL

Modern day VTOL fixed-wing aircraft based on quadplane design is relatively simple and reliable due to lack of complex mechanical components compared to tilt-wings or tilt-rotors in the pre-80’s era. Radio-controlled aerobatic airplanes have thrust-to-weight ratio of greater than unity and are capable of performing a range of impressive maneuvers including the so-called harrier maneuver. We hereby present a new maneuver known as the retarded harrier that is applicable to un/manned fixed-wing aircraft for achieving VTOL flight with a better forward flight performance than a quadplane in terms of weight, speed and esthetics. An airplane with tandem roto-stabilizers is also presented as an efficient airframe to achieve VTOL via retarded harrier maneuver, and detailed analysis is given for hovering at 45° and 60° and comparison is made against the widely adopted quadplane. This work also includes experimental demonstration of retarded harrier maneuver using a small remotely pilot airplane of wingspan 650 mm.

Prediction of urban human mobility using large-scale taxi traces and its applications

This paper investigates human mobility patterns in an urban taxi transportation system. This work focuses on predicting human mobility from discovering patterns of in the number of passenger pick-ups quantity （PUQ） from urban hotspots. This paper proposes an improved ARIMA based prediction method to forecast the spatial-temporal variation of passengers in a hotspot. Evaluation with a large-scale real- world data set of 4 000 taxis＇ GPS traces over one year shows a prediction error of only 5.8%. We also explore the applica- tion of the pl^di^fioti approach to help drivers find their next passetlgerS, The sinatllation results using historical real-world data demonstrate that, with our guidance, drivers can reduce the time taken and distance travelled, to find their next pas- senger＋ by 37.1% and 6.4% respectively,

Utilization and Analysis of Resource Mobility in Space Information Networks

In space information networks,resource mobility is an important factor affecting the network performance,which not only results in challenges in resource management but also brings opportunities to the improvement of network service capability.In order to explore the restriction and improvement mechanism of resource mobility on network performance,we firstly use the time-expanded resource relationship graph to represent the moving behavior of multidimensional resources and the collaborative relationship between different resources.Then by jointly considering the number of disjoint resource combinations,the length of moving time window,and the parameter of resource independence,we propose(k,n,L)degree of freedom on resource combination as a metric measuring performance gain resulted from resource mobility.Furthermore,the analysis of resource mobility is transformed into the problem of finding disjoint paths in the graph,and the tradeoff relationship between QoS requirements of task and resource mobility utilization is discussed.Finally,the tradeoff between the gain of resource mobility utilization and the payment of service process delay is revealed through simulation.

Comparison for the carrier mobility between the III–V nitrides and AlGaAs/GaAs heterostructure field-effect transistors

Using the measured capacitance-voltage curves ofNi/Au Schottky contacts with different areas and the current-voltage characteristics for the A1GaAs/GaAs, A1GaN/A1N/GaN and InoAsA10.szN/A1N/GaN heterostructure field-effect transistors （HFETs） at low drain-source voltage, the two-dimensional electron gas （2DEG） electron mobility for the prepared HFETs was calculated and analyzed. It was found that there is an obvious difference for the variation trend of the mobility curves between the Ⅲ-V nitride HFETs and the A1GaAs/GaAs HFETs. In the III-V nitride HFETs, the variation trend for the curves of the 2DEG electron mobility with the gate bias is closely related to the ratio of the gate length to the drainto-source distance. While the ratio of the gate length to the drainto-source distance has no effect on the variation trend for the curves of the 2DEG electron mobility with the gate bias in the A1GaAs/GaAs HFETs. The reason is attributed to the polarization Coulomb field scattering in the Ⅲ-V nitride HFETs.