Jessica Hsu

An Efficient Intranet Networking Solution for Airborne Networks

We illustrate a novel wireless intranet networking protocol providing the flexibility and efficiency needed to operate in airborne environments. A critical component of this protocol is an efficient mobile ad-hoc networking (MANET) design, known as adaptive hybrid domain routing (AHDR) protocol, devised primarily for airborne networking. We describe the driving networking requirements and tradeoffs, protocol architecture, and measured and simulated performance. The MANET element in this protocol is composed of a strategic combination of proactive and reactive algorithms. It provides updated route information for neighbor nodes and offers optimized route resolution for unknown routes in a fast-changing topology. The set of optimization parameters for making routing decisions is configurable via a network management module. The selection of the best route, data rate, transmission power, message format, frame length, and transmission time is distributed and depends on real-time optimization parameters

Adaptive Management of Scalable Mobile Ad-Hoc Networks with Non-homogeneous Topology

In this paper, we discuss the management of scalable mobile ad-hoc networks (MANET) in which nodes are equipped with a range of adjustable capabilities (transmission range, data rate, and radio interface, etc.) and operate in quite diverse environment (in terms of channel condition and node density, etc.). To support communication in such a dynamic networking environment requires a MANET protocol that is adaptable to spatial and temporal changes. As such, it is crucial to optimize node/link controllability so that node/link resources can be best utilized and a good performance can be achieved. Moreover, it is also necessary to feature statistical measures when evaluating the performance, such as the variance of these metrics in addition to the average. As an extension of our previous research, we continue to study Adaptive Hybrid Domain Routing (AHDR) protocol in regard to the effectiveness of the flooding architecture. We also evaluate various topology control techniques that ensure guaranteed service to disadvantaged nodes and across critical links (sparse connectivity). These efforts serve as very first steps to comprehensively study the impact of network non-homogeneity and variance in topology management.

Flexible access secure transfer (FAST) tactical communications waveform for airborne networking

The military capabilities necessary to realize DODs vision on network centric operation depends upon achieving information and decision superiority through the implementation of an IP enabled jam resistant airborne networking waveform that extends the capabilities of the GIG into the tactical edge airborne and space environments. This paper describes a novel communication protocol called flexible access secure transfer (FAST) for airborne networking waveform that enables low latency communication for time sensitive tactical networking in addition to providing mobile ad-hoc networking in high mobility tactical edge operations. FAST is being developed to operate as a new mode for JTRS networking waveform primarily as an airborne Intranet. It can also be deployed in many of existing Air Force fighters equipped with multifunctional informational distribution system (MlDS) without integration impact to these platforms

Integrating Local Neighborhood Congestion and Path Stability into QoS Routing for Tactical Networks

Routing protocols for wireless Mobile Ad Hoc Networks (MANETs) have been explored extensively in recent years. However, most of the work thus far has focused on finding a feasible route from a source to a destination in a timely and efficient manner without considering the impact on the transport performance of existing application traffic or the newly added flows. As a result, parts of the network become saturated with no means of adaptively compensating for or routing traffic around the overloaded areas, thereby lowering network efficiency. While this limitation may be acceptable for best-effort or delay-tolerant data transfers, real-time applications often require a certain level of Quality-of-Service (QoS) from the network. A comprehensive QoS-enabled MANET solution benefits from a QoS-aware routing scheme that considers the applications transport requirements and the data transport conditions of available paths. We propose a distributed multi-path QoS-aware routing scheme that leverages common MANET characteristics (e.g., neighborhood congestion and path stability) to meet the transport service requirements of real-time applications. The QoS routing scheme implements a method of superimposing distributed neighborhood congestion, neighborhood density, link stability and delay information over multiple discovered paths when calculating the next hop decision. In addition, the solution increases overall network capacity by using otherwise idle network resources. In this paper, we discuss multi-path discovery, the associated QoS metric calculations, and the QoS-aware path selection process.

Network synchronization for distributed MANET

Mobile ad-hoc networks (MANET) are often characterized with rapidly changing topologies, presenting a constant challenge for time synchronization. This challenge holds especially true in tactical edge ground military networks, where topological instabilities are enhanced by hostile transmission environments. In the absence of GPS, time synchronization within the context of a tactical environment requires resilience and ease of deployment. Hardware requirements must be carefully controlled, while relying on distributed coordination techniques to avoid single points of failure. Current tactical ground networks are often deployed without high accuracy oscillators, but still require time synchronization on the order of 1us. Our work demonstrates a distributed synchronization approach with a resource efficient solution that handles these requirements. We introduce cross-layer ad-hoc network synchronization (CLANS), a low overhead time synchronization protocol designed for MANETs and enables coarse synchronization without relying on GPS data. CLANS leverages routing information, channel access schemes, and distributed scheduling protocols that typically exist in a MANET. This provides a resilient, distributed time synchronization solution with relaxed hardware requirements. Simulation results show that CLANS can achieve network synchronization within 1 us in lossy multi-hop networks with the presence of packet loss and measurement noise.

Distributed medium access control for multiple hop tactical networks

In mobile ad-hoc networks (MANET), traffic coordination is a constant challenge. Node topologies and transmission patterns are continuously changing, making wireless communications complicated and difficult to maintain. Adaptive transmission scheduling must be implemented in order to relieve the stresses placed upon a MANET by packet collisions. In this paper, we identify the impact of hidden nodes in a multiple hop network with reference to a new shift in warfare style. We introduce Distributed medium access control (DMAC), a distributed TDMA channel access protocol designed with low physical requirements (single-channel, half-duplex radio with clear channel assessment) that manages outgoing traffic based on traffic type. By selectively handling outbound packet types using transmission techniques suited to each type, DMAC reduces the overhead and complexity of coordinating channel access. DMAC strives to be portable and versatile while using distributed scheduling and traffic control to protect the network against hidden nodes. These techniques provide resilient collision avoidance with nodes beyond carrier sensing range. This allows DMAC to provide an adaptable solution for MAC access in a MANET. We compare DMAC performance to Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA) in relevant tactic1al scenarios. The scenarios model a realistic military field deployment with emphasis on the importance of multiple hop communications within a small network. In these scenarios, DMAC provides higher system throughput than CSMA/CA, by avoiding collisions and minimizing scheduling overhead. This provides compelling evidence for DMACs potential efficiency gains in MANET environments.

Distributed sensing and communications in tactical robotic networks

In this paper, we address the issues of distributed sensing, communications, mobility control, and self-configuration in robotic networks. In particular, we develop a distributed algorithm that exploits the proactive movements of robotic platforms to achieve a perfect balance between providing sensing coverage and maintaining RF connectivity. The main elements of our proposed approach are based on the concept of virtual potential force (VPF). To circumvent the limitations of existing robotic movement and deployment algorithms, our algorithm takes its inputs directly from local measurements corresponding to RF signal strength or signal to noise ratio (SNR) and maps various control objectives onto a set of corresponding virtual forces. The sum of all the virtual forces directs the adaptive movements of robots. Using simulations, we demonstrate the viability and robustness of our proposed approach.

Minimizing Control Management Overhead for Scalable Mobile Ad-Hoc Networks

In this paper, we provide a parametric model for analyzing the control overhead usage In mobile ad-hoc networks (MANET). In particular, we focus on evaluating the Impact of the hierarchy of both topology formation and routing on the scalability of overhead usage. Via an analytical approach, we quantitatively characterize the amount of overhead under different domain sizes, as well as other design parameters. The results help us to assess optimal scaling of overhead traffic as a function of network size N and to provide insights into developing scalable routing architectures for MANET.

Efficient Dissemination Techniques for MANET Routing Control Messages

The challenges of optimal flooding of network control messages in Mobile Ad-Hoc Network (MANET) have been well studied in the literature [2]-[10] and [12]-[19]. A particular case of this problem is encountered in MANET routing protocols, which need to distribute routing control information to all member nodes as efficiently as possible. While both proactive and reactive MANET routing protocols exist, in some environments a proactive approach will be used to reduce communications latency as much as possible. Even in a hybrid protocol, the proactive portion requires some amount of information exchange among all nodes. Many previous papers have discussed optimal flooding in a variety of environments under a variety of assumptions, but none have assessed the performance of a recently developed cluster based routing protocol called Adaptive Hybrid Domain Routing (AHDR). In this paper, the optimal flooding architecture developed for the clustered based AHDR protocol is discussed in detailed. The paper also compares AHDRs flooding architecture against two prominent MANET routing protocols, OLSR [3] and OSPFMDR [11]. The paper also shows simulation results for each of the flooding architectures using an unbiased and non-intrusive monitoring technique. The performance results show that AHDRs flooding architecture imposes lower overhead control traffic as compared to OLSR and OSPF-MANET-MDR while still providing better network reachability.

Improving Network Reachability and Data Rate in Tactical Wireless Networks via Collaborative Communications

In this paper, we study simple collaborative communication schemes and evaluate how they can increase the reachability and data rate of a wireless network in a tactical environment. Often nodes employed in such an environment are constrained by transmitting power, range, and dead zones. As such, maintaining network connectivity in a tactical environment presents many challenges. Collaborative power combining schemes can overcome power and range constraints. This is done by exploiting the broadcast nature of signals - collaborating nodes first listen to the transmitted data packets and then constructively combine transmissions to increase radiated energy to the receiver. As a consequence, range and SNR increase. Using analysis and simulation, we demonstrate that, by utilizing such techniques, an increase in both network reachability and data rates is possible, even in the presence of detrimental environmental conditions. Our analysis shows that these schemes not only are useful in low SNR regimes and power constrained environments, but also can improve the variance of system performance.