TECHNOLOGY AREAS: Information Systems, Sensors, Space Platforms

ACQUISITION PROGRAM: Communications Satellite Program Office, ACAT I, PMW-146

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Investigate and develop algorithms and simulation techniques that reduce the variations currently experienced in received signal power due to signal shadowing and signal loss due to multipath fading. This future Land Mobile Satellite Communication (LMSC) model will more effectively and realistically simulate the spectra of signal loss by using probability models and distribution of received signal power for satellite terminals. The model will also calculate percentage of time for fade and non-fade periods, providing a significant improvement over current methods used in modeling software and hardware inefficiency and inaccuracy.

DESCRIPTION: The current LMSC modeling approach is based on recordings and a resultant channel algorithm developed and reported on by Erich Lutz in 1991 (Ref. 1). Many activities aimed at the introduction of land mobile satellite communication services have been undertaken by different organizations all over the world. The most recent and is the Mobile User Objective System (MUOS) satellite communications (SATCOM) program at the Space and Naval Warfare Systems Command (SPAWAR) in San Diego, CA. Others include: MSAT-X of NASA (Ref. 2, 3); the MSAT Program of DOC, Canada (Ref. 4); experimental programs in Japan (Ref. 5); and the Mobilesat program within AUSSAT, Australia (Ref. 6). The U.S. International Maritime Satellite (INMARSAT) program has also expanded into the area of land mobile services using the operational maritime standard-C system as an initial base (Ref. 7). Field tests have additionally been conducted on satellite paging (Ref. 8).

The current MUOS performance model suffers from a lack of realism and fidelity in simulating signal interference in stressed environments. The currently employed technique involves "offline" computation of a number representing a "down scale" in attenuation based on more qualitative than quantitative information and data. The result of this approach produces grossly over conservative results and unrealistic power demands on the system and reductions in quality of service (QoS). Improving the realism and fidelity of the model, and other like it, is the objective of this research project. The new LMSC model should show a significant improvement over existing simulations and agreement between recorded channels in past models with a significant reduction in Block Error Rate, Eb/No and QoS. In addition, if the transmission scheme is suitably adapted to the channel behavior, significantly more reliable and efficient data transmission via the land mobile satellite channel will be achievable.

Shadowing of the satellite signal by obstacles in the propagation path results in substantial reductions in total signal bandwidth. This attenuation increases with carrier frequency. Signal strength reduction occurs because the satellite signal is received not only via the direct path but also through reflections from surrounding objects. Due to their different propagation distances, multipath signals can add destructively resulting in a "deep fade" and signal strength reduction. The development of the model being proposed will utilize probability model processing to aid with improved design of both satellite software and hardware. This model will incorporate a Graphical User Interface (GUI) to provide a user friendly interface allowing an analyst the capability of configuring different SATCOM simulation scenarios.

PHASE I:
• Conduct research to develop a prototype of an improved LMSC model.
• Develop an optimal approach for building the LMSC model.
• Develop a plan to model all UHF SATCOM capabilities currently available to the warfighter.

PHASE II:
• Develop a prototype system based on the Phase I work.
• Demonstrate system feasibility, conceptual design, database design, interface capability.
• Illustrate a practical approach for the implementation of the model based on the developed prototype.

PHASE III:
• Develop a modular, scalable, and reusable system using the prototype from Phase II.
• Include a database of available SATCOM equipment and resources in the model.
• Incorporate the ability to quickly assess different SATCOM scenarios; visualization of dynamic scenarios; and an automation capability within the model.
• Develop an intuitive GUI interface to the model.
• Ensure capability of the model with existing industry and military resources that could take advantage of the LMSC model capabilities, and the GUI interface.

PRIVATE SECTOR COMMERCIAL POTENTIAL.DUAL-USE APPLICATIONS: The resulting product should provide a valuable assessment of potential shadowing and multipath fading problems for the defense industry commercial satellite users who operate LMSC constellations. This would help in the placement of future receivers and prevention of bandwidth loss. The resulting model may also be able to harness additional bandwidth from land units that are already deployed through minor modifications and antenna adjustments.

REFERENCES: 1. E. Lutz, et al. "The Land Mobile Satellite communication Channel-Recording, Statistics and Channel Model., "IEEE Log Number 9143058.

2. F. Naderi, "An advanced generation lands mobile satellite system and its critical technologies, "in Proc. Nat. Telesystems Conf., TX, and Nov. 1982.

3. R.R. Lovell, G.H. Knouse, and W.J. Weber, "An experiment to enable commercial mobile satellite service," in Proc. Nat. Telesystems Conf., TX, Nov. 1982.

4. S. Miura, "Experimental mobile satellite system for communications using Engineering Test Satellite-V (ETS-V/EMSS-C)," presented at the IAF ’84, Lausanne, Switzerland, Oct. 1984.

5. M. Wagg, "MOBILESAT, Australia’s own," in Proc. Int. Mobile Sat. Conf., Ottawa, Canada, June 1990.

6. R. Rogard, "A land-mobile satellite system for digital communications in Europe," in Proc. ESA Workshop, Noordwijk, the Netherlands, June 1986.

7. G. Berzins, "Communications on the move-INMARSAT’s services in the future" in Proc. Fourth Int. Conf. on Satellite Systems for Mobile Commun. And Navigation, London, U.K., Oct. 1988.

8. I.E. Casewell, I.C. Ferebee, and M. Tomlinsons, "A satellite paging system for land mobile users," in Proc. Fourth Int. Conf. on Satellite Systems for Mobile Commun. And Navigation, London, U.K., Oct. 1988.

KEYWORDS: Modeling, Channel Model, Stochastic, Land-Mobile, Block Error Rate, SATCOM

TPOC: Jack Nicholson
Phone: (619)524-7768
Fax:
Email: [email protected]
2nd TPOC: Pat Browne
Phone: (858)537-8617
Fax: (619)524-7861
Email: [email protected]

** TOPIC AUTHOR (TPOC) **

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