Jerry Brand

Short Messaging Services using TDRSS with low-power Personal Communication Devices

The Tracking and Data Relay Satellite (TDRS) and the TDRS System (TDRSS) form the basis for NASAs Space Network (SN) originally intended for manned spaceflight communications. While admirably serving this function, the TDRSS can also provide alternate communications for a variety of low-power operational requirements. This includes the use of Short Messaging Services (SMS) with personal-sized devices where small amounts of text can be communicated over beyond line-of-sight distances (BLOS). TDRSs high-gain Ku-band antennas enable BLOS communication to low-power Personal Communications Devices (PCD). In analyzing these communication links, several factors must be considered and alternatives studied to obtain optimum performance. This paper addresses several such factors including link parameters, link closure, data rates, suitable error correction and coding, antenna constraints, transmit power, and area coverage and their relationship in establishing a high-probability of successful communication. Overall, this paper presents a functional concept including practical considerations using TDRSS for SMS with personal communications devices.

Overcoming stressed satellite networks using alternative communications

As advanced communications techniques reach capacity, have reduced performance or system availability, or become unusable, the warfighter must have a reliable, high-capacity communications system in place and standing ready to supplant the degrading systems. Events in the recent past have shown satellites vulnerable to a number of ills or potential problems that could be debilitating. This paper addresses supporting the warfighter as satellite communications (SATCOM) vanishes during stressed communications conditions such as jamming. The text presents example networks encompassing representative operational conditions and scenarios. Various analysis results present available user rates, expected latencies, and network capacities replacing the stressed SATCOM links as well as future potential research directions.

On the use of the wideband gapfiller satellite at Ka-band for communications-on-the-move

As the military moves toward the objective force, satellite communications on-the-move (SATCOM OTM) becomes a key element in maintaining continuous warfighter communications. The wideband gapfiller satellite (WGS) will operate at X and Ka-band and offers great near-term potential to fill the SATCOM OTM gap that exists today. This paper addresses the general mobile ground segment requirements including channel specifications; noise power generation and satellite transponder gain states; system operational limitations, and how satellite operations can address potential solutions at Ka-band. The paper includes appropriate background material, practical satellite link calculation results and examples of small aperture terminals, suitable for OTM operation, over the WGS.

Real-time control and management of roaming wideband SATCOM terminals

Wideband SATCOM provides essential beyond line-of-sight communications services. At this time, however, no widely adopted protocols exist to facilitate roaming between access domains. In addition, most commercial SATCOM networks rely on proprietary network management systems. This paper addresses use of a Manager of Manager architecture, supported by local intelligent agents, for managing a global “mixture of media” SATCOM network with multiple access domains. Emphasis is on managing cross-domain roaming, where challenges include terminal mobility, waveform switching, adaptive modulation/coding, antenna beam handover, terminal reconfiguration, service transfer, along with associated management and control of multiple service providers in realtime. Policy planning and enforcement coordination between subsidiary network managers and element managers is discussed.

On the use of a standard backplane in a modular satellite communications terminal architecture

As the future of modular satellite communication terminals heads toward commercial standards, the use of a common or standard backplane drives the overall architecture to a more useable and reusable reference model. This paper delves into a reference architecturepsilas backplane formation from multiple perspectives. This includes suggested hardware and software module features that facilitate re-usability as well as interoperability, and an open system approach enabling ease in adding capabilities. Other areas of interest examined include items such as the overall data throughput and any dependencies incurred from the architectures interrelationships. Overall, the paper covers a general topical discussion of the standard backplane and related architectural artifacts. The paper offers some concluding remarks including suggested topics for further study.

Available user information rate capacities in battlespace network centric sensor operations

As network centric operations (NCO) deploy in military missions on the land, sea and in the air, bandwidth demands dictate exploitation of available electromagnetic spectrum. This valuable warfighter resource must deliver timely information across various communication networks in the most efficient and reliable manner. Internet protocol version4/6 (IPv4/6) intends to achieve such bandwidth utilization but the more important question of latency and reliable information delivery stands paramount for swift and decisive actions. This bandwidth utilization comes to the warfighter in terms of available data rates and subsequent to that, information rates. Overall, the paper describes the major aspects desired in a reliable NCO communications system as well as the required element performances. This paper offers typical scenarios for various networked links, their associated data and information rates, expected latencies, and typical link closure distances. Analysis couples realistic example network formations to present a representative foundation for performance prediction, evaluation and measurement. This includes realistic constraints in representative environments producing analytical results suitable for communication system lay-downs. The paper concludes with system observations and a look to future efforts that would benefit the warfighter when completed.

On the use of Small Satellites for Operational Responsive Space Missions

As the warfighter moves through the 21st century, an Operational Responsive Space (ORS) segment can bring significant force advantages. These benefits support diverse missions providing the combat commander enhancements such as ISR data, data exfiltration, current weather and terrain mappings, container or ship tracking as well as others such as hyperspectral or multispectral imaging. While the ORS segment contains many diverse and interesting aspects, this paper addresses the basic deployment and mission capabilities while focusing on the orbital parameters, communications requirements and the resulting information exchange capacities and capabilities. This work further describes using Programmable Modems (or Software Defined Radios (SDR)) with Radiation Hardened (RH) properties. An offered conclusion and suggested additional areas of study round out the paper.

On the Implementation Advantages of an Open Modular Modem Architecture

As the warfighter moves into the transformational world of communications beyond the line-of-sight (BLOS) of the near future, a key component of the architecture revolves around the core modem and its adaptability to various operational needs. This paper explores these needs and the requirements necessary to fulfill the communication alternatives and how they apply to various applications. Among these requirements the need for a modular, scaleable and adaptable modem working with a suitable backplane interface to external networks becomes paramount for continued information flow under dynamic conditions. The paper details various configurations such as mobile, manpack, fixed and airborne. The architecture describes a scaleable platform ranging in terms of computational elements from single to multiple signal processors and suitable memory storage. Additionally, the paper addresses the need for a common internal modem communication interface, such as the Open Core Protocol (OCP), enabling expandability and the incorporation of modules required for the particular implementation. The paper also includes a backplane interface amenable to various system incorporations without hardware changes and requiring a minimal software application interface. We explore backplanes such as those described by the Advanced Telecommunications Computing Architecture (ATCA) or VMEbus International Trade Association (VITA) references that enable versatile deployments with external equipment and systems. The paper concludes with various recommendations and areas for additional study and applications.

Improving Mission Assurance using Bit-True Hitless Data Path Selection at 10 Gbps #220

The packetization presents several problems in terms of protocol adaptation and data continuity as switching occurs. This paper addresses such issues and illustrates methods to overcome such adversity as well as alternatives for reuse across multiple domains. The DoD, Intelligence Community and NASA can benefit from higher mission assurance as the network-centric operation transformation continues. The data streams exhibit significant delay between them as well as varying error rates. These data flows require careful alignment and as the data rate increases to 10 Gbps or greater, particular attention must be paid in obtaining the desired bit-true alignment. The equipment contains the necessary switching information but only maintains this control knowledge embedded within the equipment. As such, an external user of this equipment does not have visibility or control of these embedded switching paths. Forward error correction (FEC) also plays a major role in establishing the highest quality information flow. One method that overcomes this limitation delves down to the bit level, aligning each redundant source on the bit boundary. This paper describes such a method of switching on a bit-by-bit, or bit-true basis. This includes adjusting for delays between each source, buffering to account for advancement or retardation of the sources, sorting based on internal or external control parameters, and selecting the optimum source for output. Results presented by the paper include technology realizations such as field-programmable gate array (FPGA) implementations, general parameter measurement and protocol adaptations necessary to provide such robust switching. Methods to handle the embedded FEC are discussed with associated ramifications. Overall, the paper presents a general method of maintaining high-reliability in redundant sourced systems with specific analysis applied to high-speed (10 Gbps) information transfer and network implementation

On the design of satellite transponder receive chain gain distribution for efficient wideband channel utilization

As the warfighter becomes mobile and beyond line-of-sight (BLOS) information exchange provides essential capabilities, satellite transmission systems arrive as a critical communications component. Receive chain gain characteristics drive the wideband satellite system noise performance. These characteristics must be carefully considered in regard to communication link closure. This paper presents solid evidence that not only must the low noise amplifier (LNA) noise characteristics be optimized, the entire receive gain/loss structure must be crafted to compensate for overall transponder gain distributions. In particular, the variable and cascaded gain or loss of each controlling the overall transponder transfer function must be properly designed. This paper highlights results showing the cascading of LNAs and attenuators in a fashion to accommodate large effective isotropic radiated powers (EIRP) as well as the generally smaller EIRP available from the warfighters mobile terminals. The paper presents transponder gains for various cases of power and/or bandwidth limited terminals. Graphs and figures detail the overall satellite transfer characteristics as well. From these canonical cases, we explore different operational effects and the resulting communication link parameters. Combinations of large and small ground terminal EIRPs define useful transponder gain operating ranges as well as non-desirable regions. The paper further provides results of such operational conditions and how they can best be accommodated in MILSATCOM systems such as the wideband gapfiller satellite (WGS). Conclusions on reliable gain/loss combinations and channel utilization round out the paper. Overall, the paper presents various methods of achieving suitable satellite transponder transfer characteristics through careful satellite receive chain design.