William T. Kasch

Key Challenges of Military Tactical Networking and the Elusive Promise of MANET Technology

Mobile ad hoc networks (MANETs) are considered by many as fundamental to realizing the global information grid (GIG) and the vision of network-centric warfare. Indeed, a fully realized MANET would be powerful in enabling highly mobile, highly responsive, and quickly deployable tactical forces. However, significant technical challenges remain before this realization is viable. Addressing these deficiencies is a significant task that will require the invention and adoption of new technology. The goal of this article is not to declare these capabilities impossible to achieve. Rather, it is to manage the expectation of the capabilities achievable in the foreseeable future through edification on the technical difficulties standing between current technology and the desired capabilities. This article provides an overview of the military MANET problem space, describing the ideal military MANET solution. Several deficiencies are highlighted that exist between MANET technologies and the desired capability. Identified technical issues include system-level architecture, routing (both interior and exterior), management, security, and medium access control (MAC), with an emphasis on the former two areas

Urban propagation measurements for ground based communication in the military UHF band

Results are presented from an experimental investigation to characterize path loss in urban terrain within the military ultrahigh frequency band (225 to 450 MHz) between ground-based communicators. Testing was conducted over a two-day period in downtown Philadelphia. Profiles of received power versus distance were generated along a variety of straight and L-shaped paths for different radio frequencies and antenna heights. The results were analyzed to determine the dependency of the received power on street width, frequency, antenna height, and corner distance (the distance between the transmitter and the corner on an L-shaped path). The results showed well-defined dependencies on all of the parameters except antenna height, which did not appear to affect the results over the range of values considered in this study. An empirical model for predicting received power was developed by fitting regression curves to the data. The model was found to be accurate to within approximately /spl plusmn/10 dB when compared against the data collected in this investigation. This study addresses an important but heretofore largely overlooked propagation environment.

Wireless network modeling and simulation tools for designers and developers

Modeling and simulation methods are employed by scientists and engineers to gain insight into system behavior that can lead to faster product time-to-market and more robust designs. These advantages come at the cost of model development time and the potential for questionable results because the model represents limited attributes of the actual system. M & S techniques are used to characterize complex interactions and performance at various layers of the protocol stack. This article provides a discussion of M & S for wireless network designers and developers, with particular attention paid to the architectural issues, as well as a discussion of the various communication M & S tools available today. The topics presented span the protocol stack, including radio-frequency-propagation M & S tools, physical-layer and waveform M & S, network-layer M & S, and distributed simulation, as well as waveform generation for test and evaluation.

Advanced communications networking concepts for the National Airspace System

This paper presents terminal-area and en-route communications networking concepts that aim to help meet future aviation requirements. Future aviation applications, combined with increasing air traffic density and aging and antiquated systems, will significantly change the National Airspace System (NAS) and result in a need to develop and adopt new communications technologies. An architectural study for flight information services (FIS) performed by The Johns Hopkins University Applied Physics Laboratory (JHU/APL), which considered both near-term and long-term technologies including terrestrial line-of-sight (LOS) systems, satellite communications (SATCOM) beyond LOS (BLOS) systems, and hybrid architectures which seek to use both types of systems, revealed that there are no existing or envisioned communications solutions that are well-suited for the application in all cases. Furthermore, studies of the terminal area reveal that there is a lack of near-term technologies that can address all requirements. This paper presents a vision of an Internet-like NAS networking architecture, and then presents mobile ad-hoc network (MANET) and wireless local area network (WLAN) concepts that could provide significantly improved networking both in the en-route and terminal areas

Propagation characteristics of ground based urban communications in the military UHF band

A series of experiments were conducted to characterize the propagation characteristics in an urban canyon setting between ground-based communicators operating within the military ultrahigh frequency band (225 to 450 MHz). The experiments were conducted over a two-day period in downtown Philadelphia. Profiles of received power versus distance were generated along a variety of straight and L-shaped paths for different radio frequencies and antenna heights. The results were analyzed to determine the dependency of the received power on street width, RF frequency, antenna height, and corner distance (the distance between the transmitter and the corner on an L-shaped path). The results showed well-defined dependencies on all of the parameters except antenna height, which did not appear to affect the results over the range of values considered in this study. The results are compared with similar measurements by other investigators operating at higher frequencies in an attempt to identify the impact of RF frequency on urban propagation. This study addresses an important but largely overlooked propagation environment

The Effects of Antenna Pointing Error on Bit Error Rate Performance in Mobile Directional Antenna Applications

This paper investigates the issue of antenna pointing error in mobile directional antenna applications and its impact on bit error rate (BER) performance of the link. BER performance is investigated for a variety of postulated antenna characteristics in order to determine the sensitivity of BER performance to antenna pointing inaccuracies. The method employed uses motion dynamics derived from vehicular road course tests to determine power fade profiles for various antenna types as a function of antenna pointing accuracy. These power fade profiles are then used to characterize these channels as Rician multipath channels. Finally antenna pointing accuracy is mapped directly to link BER performance for an uncoded differential phase shift keying (DPSK) waveform. This study has found that this is a complex multi-dimensional problem. Power fades resulting from pointing inaccuracy generally deteriorate for larger antennas with narrow beamwidths. However, smaller antennas are more susceptible to multipath effects due to increased beamwidth. Results of this paper suggests that, contrary to what intuition might initially suggest, larger antennas with more narrow beamwidths may actually outperform smaller antennas in mobile applications

Transforming legacy network systems for use in the Army Future Force

This paper proposes a method to integrate legacy networks into the overall Army Future Force (FF) network in a useful manner. A serious technical challenge presented by such coexistence of next-generation and legacy networks is the ability to provide sufficient end-to-end quality-of-service (QoS) performance. Providing end-to-end QoS is challenging when one or more subnetworks involved in the end-to-end communication was not intended to provide QoS. Another technical challenge lies in effectively managing legacy networks. Typically, legacy networks are highly reliant on static planning, and were not designed to provide a dynamic network management capability. This paper addresses a variety of technical issues associated with the integration of legacy network systems into the Army FF, focusing primarily on QoS and network management. This paper then presents concepts that address these issues using the advanced extremely high frequency (AEHF) satellite system as a case study.

The Wireless Ecosystem

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A hybrid 802.16/802.11 network architecture for a united states coastal area network

This paper presents a concept for a United States Coastal Area Network (U-SCAN) that is comprised of IEEE 802.11, 802.16, and satellite communications technologies. The Office of Naval Research (ONR) on behalf of the National Oceanographic Partnership Program (NOPP) has tasked The Johns Hopkins University Applied Physics Laboratory (JHU/APL) to perform an architectural study into the establishment of a United States Coastal Area Network (U-SCAN). The goal of this study is to define a wireless network architecture that can be deployed to enable contiguous coastal area network coverage for scientific, commercial, and homeland security (e.g. Coast Guard) applications within the United States Exclusive Economic Zone (EEZ), in a manner that is flexible, manageable, and affordable. The JHU/APL study will ultimately provide recommendations to NOPP regarding potential network architectures and technologies that could provide the desired capability, with a particular focus on commercial (both existing and emerging) technologies. This paper presents the envisioned U-SCAN architecture, and presents the envisioned technical capabilities and shortcomings of the component candidate technologies.

The evaluation of wireless networking through action

The adaptable channel testbed for investigation of wireless networks (ACTION) has been developed as a hardware-in-the-loop testbed that can model a variety of wireless network scenarios. Through the use of discrete devices, networking hardware (both client and infrastructure) can be connected directly without the need to radiate over-the-air. Signal characteristics such as amplitude, phase, and frequency can be changed to simulate wireless channels and introduce modeling features such as mobility (Doppler shift), fading (random phase changes) and amplitude (range). These discrete devices constitute the simulated wireless network environment (SWiNE), providing virtual channel paths as seen by the wireless hardware connected to ACTION. ACTION has been used to model fast-moving platforms (up to Mach 2) by introducing Doppler shift into the channels and analyzing TCP/UDP performance as seen by the application. Packet error statistics along with application throughput numbers are the appropriate metrics. ACTION also enables test setups that include injection of interfering radios and signals to model jamming and interference scenarios. This paper covers the details of the ACTION implementation, some test scenarios that have been set up with ACTION, results from those tests, implications of the results on military communications, and future possibilities for the ACTION platform as a key part of network modeling and simulation from a hardware-in-the-loop perspective