James M. Metzler

N-CET: Network-centric exploitation and tracking

The Network-Centric Exploitation and Tracking (N-CET) program is a research effort to enhance intelligence exploitation in a tactical environment by cross-cueing sensors and fusing data from on-board sources with processed information from off-board platforms and sharing the resulting products in a net-centric manner. At the core of N-CET are information management services that decouple data producers and consumers, allowing reconfiguration to suit mission needs. Network-centric algorithms utilize the availability of information from both homogeneous and complementary on-board and off-board sensors. Organic capabilities facilitate the extraction of actionable information from high bandwidth sensor data and ensure the necessary information arrives at other platforms and users in a timely manner. This paper provides an overview of the N-CET architecture and the sensors and algorithms currently implemented upon it. The extent to which such algorithms are enhanced in a network-centric environment is discussed and the challenges of managing the resulting dynamic information space in a tactical publish/subscribe/query model are presented.

Supervisory Control of a Database Unit

To effectively enhance service availability, this paper proposes a redundancy configuration for a database unit residing in a command and control (C2) system that supports air operations. The results of modeling, supervisory control, and performance analysis of the database unit are presented. The unit is modeled as a closed Markovian queuing network. State variable feedback is used to implement the functions of restoration and routing upon the identification of the failure of one of the database servers in the unit. Several control policies are evaluated in terms of the resulting mean time to unit failure, the steady state availability, the expected response time, and the service overhead of the database unit.

Opportunistic Sharing of Airborne Sensors

Airborne sensors are often idle for much of their flight, e.g., while the platform carrying them is in transit to and from the locations of sensor tasks. The sensing needs of many other potential information consumers might thus be served by sharing such sensors, allowing other information consumers to opportunistically task them during their otherwise unscheduled time. Toward this end, we have developed Mission-Driven Tasking of Information Producers (MTIP), a prototype system for opportunistic sharing of airborne sensors. This paper describes its implementation as an agent-based task allocation system on top of the Marti Quality of Service (QoS)-managed publish-subscribe information management system, and presents simulations of a disaster response scenario demonstrating how MTIP can increase the number of sensor tasks served as well as reducing the number of UAVs required to serve a given set of sensor tasks.

Adaptive Task Reallocation for Airborne Sensor Sharing

Airborne sensor platforms are becoming increasingly significant for both civilian and military operations, yet at present their sensors are typically idle for much of their flight time. Opportunistic sensor sharing, e.g., via the Mission-Driven Tasking of Information Producers (MTIP) can greatly improve sensor utilization, both decreasing the number of platforms needed to achieve a goal and increasing sensor efficacy. Dynamically changing environments, however, are likely to rapidly render any initial plan obsolete. In this paper, we address the challenge of adaptive reallocation of sensor sharing tasks, demonstrating how the adaptable sensor sharing of MTIP can provide significant performance improvements in a large-scale disaster response scenario, as well as identifying areas of inefficiency that are likely to benefit from further improvement.

Performance analysis of a controlled database unit subject to decision errors and control delays

This paper extends the performance analysis of a controlled database unit to include the cases where errors and delays can occur in state-based control actions as a result of uncertainty in the knowledge of the system state. The paper details the way such errors and delays are captured through augmenting the state space in the Markov model of the database unit. State variable feedback is used to activate the process of restoration upon the failure of one of the database servers in the unit. The performance of the database is evaluated in terms of the resulting mean time to unit failure, the steady state availability, the expected response time, and the service overhead of the database unit. All performance measures are examined with respect to the likelihood of decision error and the amount of control action delay

A hybrid publish subscribe protocol

Content-based publish/subscribe system performance depends upon the efficient subscription matching and event dissemination to interested subscribers. We propose a hybrid content-based publish/subscribe protocol for large size events wherein a centralized brokering system is coupled with a decentralized BitTorrent-like peer-to-peer (P2P) protocol for scalable event distribution among publishers and subscribers. Events are mapped to a torrent that grows as new events are published. Subscribers self-broker on event metadata and request content only if interested. Subscriber interests determine event popularity that the broker estimates with sampling. Popular events are disseminated P2P; unpopular events, directly from the broker; and somewhat popular ones, with P2P and broker-directed pre-seeding. The challenge is the dissemination of popular events without overwhelming centralized resources while efficiently disseminating unpopular events that lack sufficient interest to sustain gossip-based dissemination. The key advances include new means of handling variable event popularity inherent in content-based pub/sub and an adaptive anti-entropy mechanism for undelivered events.

Adaptive Opportunistic Airborne Sensor Sharing

Airborne sensor platforms are becoming increasingly significant for both civilian and military operations; yet, at present, their sensors are typically idle for much of their flight time, e.g., while the sensor-equipped platform is in transit to and from the locations of sensing tasks. The sensing needs of many other potential information consumers might thus be served by sharing such sensors, thereby allowing other information consumers to opportunistically task them during their otherwise unscheduled time, as well as enabling other improvements, such as decreasing the number of platforms needed to achieve a goal and increasing the resilience of sensor tasks through duplication. We have implemented a prototype system realizing these goals in Mission-Driven Tasking of Information Producers (MTIP), which leverages an agent-based representation of tasks and sensors to enable fast, effective, and adaptive opportunistic sharing of airborne sensors. Using a simulated large-scale disaster-response scenario populated with publicly available Geographic Information System (GIS) datasets, we demonstrate that correlations in task location are likely to lead to a high degree of potential for sensor-sharing. We then validate that our implementation of MTIP can successfully carry out such sharing, showing that it increases the number of sensor tasks served, reduces the number of platforms required to serve a given set of sensor tasks, and adapts well to radical changes in flight path.

Sensor management in real time and a camera control application for air vehicles

Camera systems are increasingly utilized in Intelligence, Surveillance and Reconnaissance (ISR) missions on manned and unmanned aircraft. For manned missions, the automatic control of the camera field of view and orientation through pan-tilt-zoom (PTZ) commands frees the pilot to perform higher cognitive functions. For unmanned missions, automatic PTZ commands enable higher degrees of autonomy. This paper addresses the problem of controlling the field of view and orientation of cameras mounted on air vehicles so that the resulting images of commanded areas of interest (AOIs) have specified ground sampling distances (GSDs). The problem is complicated by several factors: First, while the instantaneous positions of the vehicles are assumed to be known, their routes, including their altitude profiles, are not known in advance, which precludes preplanning. Second, the sizes of the AOIs are arbitrary, implying that a single look of the camera may not be sufficient to cover them. Third, the slew times of the cameras may be too slow, and the cameras may not operate while PTZ parameters are changing. Finally, given an AOI, the time intervals when the desired GSDs are achievable varies for different cameras. In the paper, we first show that successful collection of an AOI image (i.e. collection with a prescribed GSD) is only possible if the aircraft lies inside a spherical cap depending on the position of the AOI, and the desired GSD. Given a stream of requested AOIs, with corresponding GSDs and values characterizing their importance to a user, we then develop algorithms to service the most valuable ensemble of requests, while satisfying the requested GSDs. Three algorithms are developed: (1) a scheduling algorithm, for deciding which request to service at a given instant of time, (2) an admission control algorithm, enabling a graceful degradation in case of system overload (more requests than available timeline) and (3) an algorithm for deciding which of the platforms (air vehicle and camera) services a given request. We examine each of the three algorithms in turn. The scheduling algorithm is centered on the earliest deadline first (EDF) scheme from the real-time systems literature. Deadlines for servicing AOI requests are determined by computing the intersection between the extrapolated aircraft trajectory and the spherical caps defined earlier. The admission control algorithm is developed based on schedulability tests for EDF. Finally, the algorithm for routing the requests among platforms are based on machine shop scheduling problems, which essentially promote load balancing among the platforms. We introduce a heuristic called min-max utilization, inspired on the makespan minimization procedures developed for machine shop scheduling problems. Extensive simulation results are presented, illustrating the superior performance of the algorithms in contrast to other alternatives.

An architecture to support information availability in the tactical domain

Access to information is critical to both the commander in an AOC and the warfighter in the field. Typically information is readily available at centralized command posts, however, at the tactical edge, resources are far more limited, making information dissemination a challenge. Targeting pods, already found mounted to the hardpoints of many tactical aircraft, provide a cost effective platform for making information available to tactical users. To this end, the Network-Centric Exploitation and Tracking (N-CET) program is designing, developing, and implementing a proof of concept architecture for pods that is net-centric, reconfigurable, and allows processing at the sensor. The approach taken to achieve these attributes is to embed processing and communications on the pod, and employ net-centric exploitation and fusion algorithms to distil information from high fidelity sensor data. Information Management services provide the interface between the sensors, processing, and network, disseminating information between algorithms, and prioritizing it as it goes out over the network. This paper provides an overview of the N-CET architecture and the sensors and net-centric algorithms integrated to evaluate the performance of the architecture through ground based experimentation.

A Simulation Study of a Reconfigurable Database

Abstract The effect of supervisory control on a redundant database unit representing a command and control (C2) system that supports air operations is investigated through simulation. Several supervisory control policies are considered. They authorize restoration and/or routing upon the failure of a server in the system. The performance of the modeled system under these policies is evaluated based on the measures of system mean-time-to-failure (MTTF), steady-state availability, expected response time, and overhead. The system is modeled as a discrete event system using a simulation tool. In addition, a system update process is implemented to ensure the currency of the information contained in the database unit.