Hopping sensors are a class of mobile sensors whose mobility design are inspired by creatures such as grasshoppers. Such sensors are able to maintain mobility in harsh terrains but may lack movement accuracy of those sensors that are powered by wheels. We examine the opportunities and challenges for utilizing the mobility of low cost hopping sensors to ensure coverage and maintain energy efficiency within a sensing field. We focus on the problem of transporting a number of hopping sensors from multiple sources to a destination. Probabilistic methods are used to contain the movement inaccuracies along the hopping course. We also consider the impact of wind under an aerodynamic setting. Two transport schemes are designed to minimize the number of hops needed while considering other constraints, such as sustaining the capability of relocating sensors within the whole network. In one scheme we use upper and lower hopping limits to apply the network mobility constraints. The other scheme uses a balancing coefficient to construct a new optimization target to meet the requirement of path optimality and network mobility dynamically. Simulation results show that both schemes work well regardless of the wind factors, while the dynamic scheme is also shown to be resilient to topological changes of the network.

Network surveillance systems provide extended perception and distributed sensing capability in monitored environments through real time monitoring of the target area and target objects using multiple networked sensors. The development of wireless communication and sensing technology make it possible to deploy networked surveillance systems in various environments. We consider a surveillance network where the sensors are static. The task of tracking targets in a surveillance network is challenging because of the following reasons: (1) the location of the sensors need to be optimally deployed. (2) The view of the sensors need to be optimized so that at a given time the targets are shown with a discernable resolution for feature identification. (3) It is important to devise stable control algorithms for accomplishing the surveillance task. When the target moves, it is important to switch the sensing task between sensors to maintain the visibility of the target with adequate resolution. This paper presents a novel method to deploy static sensors given a target region and a dynamic programming method to optimally switch sensors when the target moves. Finally, simulation results demonstrate the efficacy of the proposed approach for tracking targets over an area.

This paper presents our development of a network-enabled human/robot cooperative interface for tele- diagnostics of breast pathology. To enhance telepresence capabilities, our human/robot interface is comprised of an anthropomorphic arm/hand equipped with haptic and tactile sensing, ultrasound imaging capabilities, a physician interface capable of rendering both haptic and tactile information, and two-way audio and video. This cooperative and multimedia interface was tested via the Internet and enables tele-diagnostics. Preliminary experiments had demonstrated the effectiveness of the developed human/robot tele-diagnostic interface. That is, it will greatly enhance and improve the diagnostic performance as well as promote the tele-diagnostics of breast pathology in remote areas a reality.

In a heterogeneous wireless network environment, the network nodes are equipped with both wireless local area network (WLAN) and cellular interfaces. It is desirable to combine the higher bandwidth of a WLAN and the ubiquitous nature of cellular networks to provide the transport service for QoS demanding applications, such as remote sensing and control systems. Common solutions exploit the diversity of cellular channels by recruiting multiple WLAN peers to work as proxies for a MANET node that needs to communicate through the cellular network. One important problem when utilizing channel diversity in a heterogeneous wireless network environment is to balance the trade-off of channel diversity gains with MANET peer contentions. A greater number of proxies will inevitably increase the MANET contention and possibly QoS degrading of the cell, and fewer proxies may not be able to provide sufficient diversity. This paper aims to build a dynamic mechanism to determine the appropriate number of proxies to use. The mechanism uses the MAC layer retransmission rate as an indicator of the contention level in MANET. Simulation using cellular channel fading models and prevalent cell scheduling policies indicate the scheme can provide better QoS through channel diversity by using the appropriate number of proxies

Available bandwidth (AB) defined as a minimum spare capacity of links constituting a network path is an important QoS characteristic of the path. We propose to improve a whole range of "probe-rate" AB measurement tools that send sequences of measurement packets (called "trains") across the network path. If transmission times of packets in the train, called one way delays (OWD), show an increasing trend as packet sequence number in the train increases, then AB is believed to be lower than the rate at which the train was sent. In contrast, an absence of a trend indicates that AB is higher than the rate of the train. We propose an algorithm for efficient OWD trend detection and compare it to widely used OWD trend detection tests.

Current cellular data networks provide relatively low throughput, which results in long delays when downloading large files. We propose a cooperative parallel file downloading scheme to reduce latency in cellular data networks. Mobile nodes form a mobile ad hoc network (MANET) via their IEEE 802.11-based links to share their cellular link capacity. A file is split into pieces and downloaded simultaneously by the client and several neighbor nodes that act as relay proxies. The proxies then use the MANET to forward packets to the client. Thus, the client uses multiple paths for parallel downloading. No special hardware or modifications on the base stations are needed. An on-demand proxy discovery algorithm is proposed for fast and efficient proxy discovery. Experimental and simulation results show that cooperative parallel file downloading may significantly improve cellular network utilization and file download performance.

For Internet based real-time teleoperation systems, random time delay can cause instability in the closed loop control system and hence hinder task accomplishment. Event based control systems have been proposed to overcome the instability caused by the random time delay. High latency at the transport layer can still impede effective and reliable execution of tasks with high dexterity requirements. Network QoS based dynamic resource allocation has been proposed to increase the efficiency and reliability of task execution. However, these approaches only try to mitigate or overcome the effects of random time delay and do not address the cause of latency issues in the communication channel. This paper addresses the efficiency and reliability requirements for supermedia enhanced teleoperated systems by reducing the end-to-end transmission latency through the use of overlay networks. The proposed system reduces the transmission latency by using multiple, disjoint paths in overlay networks. The proposed system facilitates reliable and efficient task completion for tasks with high dexterity requirements. Experimental validation of the proposed teleoperated system using the PlanetLab Network is provided for the task of teleoperating a mobile manipulator system.

In supermedia enhanced Internet based teleoperation systems, the data flowing between the operator and the robot include robotic control commands, video, audio, haptic feedback and other media types. The difference between an Internet based teleoperation system and other Internet applications are that (1) there are many media types involved in teleoperation systems and each of them has a particular quality of service (QoS) requirement; and (2) some media types are very latency sensitive. Overlay networks have been proposed to improve the QoS of teleoperation applications. However efficient use the overlay network resources and the distribution of these resources optimally to all supermedia streams remains an important problem. This paper aims to provide a framework of QoS management for teleoperation systems over overlay networks. The validity and performance of the system is evaluated using the PlanetLab overlay network.

Networked surveillance systems provide an extended perception and distributed reasoning capability in monitored environments through the use of multiple networked sensors. The challenge for such large scale networked systems is to design an efficient modeling and analysis tool and devise stable control algorithms for accomplishing the surveillance task. Current feature (point) based visual servo and tracking techniques generally employed do not provide an optimal solution for the surveillance task. This paper presents a mutational analysis approach for shapes, and shape based control to model and design mechanisms for such active surveillance systems. The techniques of image based Hausdorff tracking and cooperative Hausdorff tracking are introduced. Finally, experimental results demonstrate the efficacy of the proposed approach for tracking targets over a large area.

In a bilateral teleoperated system, the signal transmissions between the operator and the slave manipulators have different QoS requirements in comparison to traditional network traffic. Running teleoperated systems over wireless networks poses more challenges in comparison to wired networks. The media streams involved differentiate themselves from other media types in that they require both reliable and smooth delivery. Reliable delivery requires the transport service to have TCP style semantics. By being smooth, the transport service should be able to deliver the control and sensing data with bounded and reduced latency and its variation. For example, we have conducted numerous teleoperated experiments using our system. We have found in some of our applications that if the end-to-end latency variance becomes larger than 0.3 second, the operator has difficulty maintaining smooth control of the slave manipulator. However, our simulations show that using TCP, the end-to-end latency variance can be as much as 2.5 seconds in an ad hoc wireless network. This paper proposes an improved transport service for remote sensing and control (TRSC). The service reduces the end-to-end latency and latency variance (jitter) for real-time reliable media in mobile ad hoc networks by using forward error correction encoding and multiple network paths. Simulation using NS2 shows the approach performs well under different wireless scenarios.

Some mobile devices are beginning to support both cellular and IEEE 802.11 based network interfaces. Although rates are increasing, current cellular networks provide relatively low bandwidth that do not meet the QoS requirements of many high-demanding multimedia applications. In this paper, we propose an integrated network architecture that utilizes both wireless interfaces to provide better QoS support by QoS aware wireless bandwidth aggregation (QAWBA). Via QAWBA, mobile nodes form a mobile ad hoc network (MANET) using their IEEE 802.11 interfaces to share their cellular link capacity. Some mobile nodes act as proxies to contribute their idle cellular links to support a QoS request that may exceed the available bandwidth of any individual mobile node. A K-path proxy discovery algorithm is proposed for fast and efficient proxy discovery. Simulation results show that QAWBA can significantly improve network utilization and the admission rate of QoS requests.