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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1988

A framework for implementing data services in multi-service mobile satellite systems

Mobile satellite systems being planned for introduction in the early 1990s are expected to be invariably of the multi-service type. Mobile Telephone Service (MTS), Mobile Radio Service (MRS), and Mobile Data Service (MDS) are the major classifications used to categorize the many user applications to be supported. The MTS and MRS services encompass circuit-switched voice communication applications, and may be efficiently implemented using a centralized Demand-Assigned Multiple Access (DAMA) scheme. Applications under the MDS category are, on the other hand, message-oriented and expected to vary widely in characteristics; from simplex mode short messaging applications to long duration, full-duplex interactive data communication and large file transfer applications. For some applications under this service category, the conventional circuit-based DAMA scheme may prove highly inefficient due to the long time required to set up and establish communication links relative to the actual message transmission time. It is proposed that by defining a set of basic bearer services to be supported in MDS and optimizing their transmission and access schemes independent of the MTS and MRS services, the MDS applications can be more efficiently integrated into the multi-service design of mobile satellite systems.

Ali, Mohammed O.↗
NASA NTRS1993

US domestic and international regulatory issues

The U.S. domestic and international regulatory and policy milestones since 1982, when NASA filed its petition with the Federal Communications Commission (FCC) to establish the U.S. domestic Mobile Satellite Service (MSS), are described. In 1985, the FCC proposed to establish MSS services and allocate spectrum for such service. In 1986, the FCC allocated L-band spectrum for MSS. In 1987, at the Mobile World Administrative Radio Conference (MOB WARC-87), despite U.S., Canadian, and Mexican efforts, the WARC did not adopt a multi-service, generic MSS allocation. In 1989, the FCC licensed the first MSS system. After two decisions by the U.S. Court of Appeals, the FCC's licensing actions remain intact. The FCC also has permitted Comsat to provide international aeronautical and land MSS via the Inmarsat system. Inmarsat, however, may not serve the domestic U.S. market. In 1991, the FCC accepted applications for MSS systems, most of which were non-geostationary proposals, for operation in the Radiodetermination Satellite Service (RDSS) bands, and the VHF and UHF bands. In 1992, the FCC proposed rules for non-geostationary MSS systems and applied a negotiated rulemaking procedure to each. Also in 1992, the U.S. position for flexibility in existing MSS bands and for additional worldwide MSS allocations was adopted in large part at the 1992 World Administrative Radio Conference (WARC-92).

Levin, Lon C.↗
NASA NTRS2012

Miniature EVA Software Defined Radio

As NASA embarks upon developing the Next-Generation Extra Vehicular Activity (EVA) Radio for deep space exploration, the demands on EVA battery life will substantially increase. The number of modes and frequency bands required will continue to grow in order to enable efficient and complex multi-mode operations including communications, navigation, and tracking applications. Whether conducting astronaut excursions, communicating to soldiers, or first responders responding to emergency hazards, NASA has developed an innovative, affordable, miniaturized, power-efficient software defined radio that offers unprecedented power-efficient flexibility. This lightweight, programmable, S-band, multi-service, frequency- agile EVA software defined radio (SDR) supports data, telemetry, voice, and both standard and high-definition video. Features include a modular design, an easily scalable architecture, and the EVA SDR allows for both stationary and mobile battery powered handheld operations. Currently, the radio is equipped with an S-band RF section. However, its scalable architecture can accommodate multiple RF sections simultaneously to cover multiple frequency bands. The EVA SDR also supports multiple network protocols. It currently implements a Hybrid Mesh Network based on the 802.11s open standard protocol. The radio targets RF channel data rates up to 20 Mbps and can be equipped with a real-time operating system (RTOS) that can be switched off for power-aware applications. The EVA SDR's modular design permits implementation of the same hardware at all Network Nodes concept. This approach assures the portability of the same software into any radio in the system. It also brings several benefits to the entire system including reducing system maintenance, system complexity, and development cost.

Pozhidaev, Aleksey↗