Gary Comparetto

Trends in mobile satellite technology

Demand for sophisticated personal communication services has changed communications satellite design. Satellites have moved closer to the Earth to improve communication speed and enable personal communication services. However, in so doing, they require more computing resources and more sophisticated protocols to handle intersatellite communications. This article examines the trends in communications satellite deployment and the resulting requirements for network protocols that are intended to support space communications. It reports the findings of a joint DoD/NASA effort to identify what parts of the seven-layer OSI protocol model can be adapted to support more sophisticated space applications.

Modeling and Simulation of Haipe

The high assurance Internet protocol encryptor (HAIPE) is a critical component of the global information grid (GIG) that will enable secure communications to support information assurance (IA) in the evolving network-centric architecture of the Department of Defense (DoD) and Intelligence Community networks. We developed a HAIPE model, including a HAIPE discovery approach proposed by the GIG routing working group (GRWG), to assess the impact of HAIPE overhead on the performance and scalability of the GIG. This paper describes our HAIPE model, presents the operation of the HAIPE-related protocols including HAIPE discovery, and defines future work

A communications analysis tool set that accounts for the attenuation due to foliage, buildings, and ground effects

The purpose of this paper is to describe a communications analysis tool, referred to as OPAR, that can be used in support of both in-field demonstrations and large-scale simulation activities. Using overhead imagery as a backdrop, OPAR provides a graphical user interface that allows the user to quantify the source/destination path attenuation in a mobile, ad-hoc communications network, taking into account obstructions due to foliage and buildings.

Verification and validation of the QualNet JTRS WNW and SRW waveform models

OTC, together with the JTRS JPEO and PEO-I MSO, funded a Small Business Innovative Research (SBIR) Phase 2.5 Technology Transition effort, with SNT as the contractor, to develop the JTRS Network Emulator (JNE) to support GMR LUT and MOTE test activities. The accuracy of the JNE, to a large extent, depends upon the accuracy of its constituent models. Consequently, OTC funded an effort to verify and validate the performance of the QualNet WNW and SRW waveform models. The purpose of this paper is to report on the status and results generated to date for the QualNet WNW and SRW V&V activities that are scheduled through the end of Fiscal Year 2012.

A Performance Evaluation of Transport Mechanisms in Hybrid Networks

This paper evaluates the performance of several alternative reliable unicast transport mechanisms in a hybrid network. Options investigated include end-to-end TCP (different flavors), end-to-end space communications protocol standards-transport protocol (SCPS-TP), and performance enhancing proxies (PEPs) (also called transport layer proxies). Our approach is to analyze these options in a specific scenario using modeling and simulation (M&S). We describe this scenario and the corresponding OPNET network model, our experiment plan, and the results obtained. Finally, we identify several areas for further analyses

Optimizing Route Formation Algorithm to Reduce Simulation Run-Time for Large Tactical Networks

Mobile ad-hoc networks (MANETs) are a major component of all DoD tactical networks. MANETs must be carefully analyzed to ensure integrated DoD networks perform properly on an end-to-end basis. Simulation is generally used to evaluate these networks before their actual deployment. We have identified the routing table calculation to be a major contributor to the excessive run-time and have employed an algorithm based on the breadth-first search to improve the simulation run-time. Our results show that employing the new algorithm will result in a lower run-time for the simulation

The communications resource planning tool

In tactical environments where radio communications is critical to operational missions, the ability to predict connectivity is of primary importance. Success in closing radio links in these scenarios depends to a great degree on degradations to the link including obstructions that might obscure line of sight between transmitters and receivers. Jammers can also severely degrade communications performance. The effects of these factors must be taken into consideration in the planning and performance prediction of tactical wireless links. This paper describes a tool that can be used to plan communications links in the presence of degradations such as path obstructions or the effects of jammers. We describe the tool and its features. The equations for determining the impact of jammers are provided and an example is shown.

Addressing Runtime Performance Issues in Ad-Hoc Network Simulations

Quantifying the end-to-end performance of evolving DOD communication networks is highly desired by the component and network designers during all phases of the development process. Analytical techniques, in-lab testing and field demonstrations are all necessary toward this end but all have limitations in addressing this need leaving simulation as a primary method with which to generate end-to-end performance. However, simulation often results in unacceptably long runtimes for these types of networks. The purpose of this paper is to report on the results generated in the second year of a 2-year IR&D program to investigate methods to improve simulation runtime performance of mobile ad-hoc communication networks

Small-diameter Earth terminal transmission issues in support of high data rate mobile satellite service applications

There is a growing interest by the DoD and by industry in the use of small-diameter, directional antennas in the Ku- and Ka-band frequency ranges, in order to support peer-to-peer connectivity in the Mbps data rate range. This is normally accompanied by relatively high Earth terminal (ET) transmit powers which, together with the directionality of the antenna system, may result in unacceptable off-axis ET transmission levels relative to national and international criteria. The purpose of this paper is to highlight the challenges involved in designing this type of Earth terminal in the face of evolving ET transmission limits.

Multi-band integrated satellite terminal (MIST) - a key to future SOTM for the Army

The US Armys communications capability must keep pace with the evolution of a globally deployable joint task force (JTF) and force projection army, while supporting forced entry and contingency operations. The warfighter must have the freedom and flexibility to move quickly on the battlefield using a communications terminal that is tactically responsive, mobile and interoperable and provides SATCOM-on-the-move (SOTM) and SATCOM-on-the-pause (SOTP) capability. PM MILSATCOM is helping to define this next generation army SATCOM terminal that is referred to as the multi-band integrated satellite terminal (MIST) and is currently scheduled to be fielded in several phases out to 2014. In so doing, PM MILSATCOM initiated several studies to define the MIST program better, help formulate the acquisition strategy, validate the MIST funding schedule and initiate Government cost estimates for the MIST program. The purpose of this paper is to summarize the key findings of the study performed by the MITRE Corporation in support of PM MILSATCOM. Our focus here is to summarize the notional terminal architecture design options postulated in that study and to identify the key technology areas that need to be advanced in order to ensure successful operation of the MIST terminal.