Michael A. Koets

A model-based approach to designing QoS adaptive applications

In this paper we present a model-based approach for designing quality of service adaptive applications. We have developed a prototype distributed QoS modeling environment (DQME) that captures important elements of dynamic QoS adaptation at the model level. This modeling environment is designed independent of and can be integrated with, specific application domains to capture their QoS features and adaptation strategies. It combines the domain-specific modeling capability of the generic modeling environment with the QoS adaptation mechanisms of the quality objects middleware framework. DQME captures both the QoS and the functional concerns of distributed real-time embedded systems, and provides clear separation of these two. Integrated code-synthesis tools facilitate code generation and model refinement. We present a signal analyzer case study to demonstrate the use of the DQME modeling tool in real world applications.

Enabling fractionated spacecraft communications using F6WICS

Southwest Research Institute® (SwRI®) has designed a wireless transceiver to provide inter-satellite communications as part of the Defense Advanced Research Projects Agency (DARPA) System F6 program. System F6 (Future, Fast, Flexible, Fractionated, Free-Flying Spacecraft United by Information Exchange) seeks to demonstrate the feasibility and benefits of a satellite architecture wherein the functionality of a traditional “monolithic” spacecraft is delivered by a cluster of wirelessly-interconnected modules capable of sharing their resources and utilizing resources found elsewhere in the cluster. SwRIs System F6 Wireless Inter-module Communication System (F6WICS) provides the data link and physical layers of the network stack that are specifically designed to meet the needs of fractionated space missions. F6WICS provides deterministic, real-time media access mechanisms that make efficient use of limited communications bandwidth over a wide range of spacecraft separation distances and network populations. The data link protocol is highly robust to module failure. The physical layer waveform provides robust communication, precision time transfer throughout the network, and continuous estimation of distance between spacecraft for use in navigation. The views expressed are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government. Distribution Statement “A”: Approved for Public Release, Distribution Unlimited.

A case study in applying QoS adaptation and model-based design to the design-time optimization of signal analyzer applications

The capture and classification of digital signals is an important part of military communications and of signal intelligence (SIGINT). A typical signal analyzer is built from a set of elementary signal processing operations, which often include parameters whose values can affect the quality of the signal classification. In this paper we present a case study we have conducted to evaluate the efficacy of automated parameter tuning for improving signal classification. We use a prototype signal analyzer parameter tuner, which augments a signal analyzer design with a search space controller driven by a utility function based on correct classification. It tunes parameters by automatically tweaking parameter values in a systematic way and evaluating the utility of the signal analyzer with different parameter values over a set of representative signals with known ground truth. We developed the parameter tuner using a QoS adaptive design tool we developed under the DARPA MoBIES program. We have achieved improved signal classification in three signal analyzers studied. In addition, the automated parameter tuning exercise has the side effect of providing increased understanding of how parameters contribute to signal analysis. The paper describes the signal analyzer parameter tuner, the experiments that we conducted as a part of our case study, and the empirical results of the experiments.

A configurable signal analyzer for embedded systems

Rapid adaptability is a critical requirement for modern communication intelligence systems. This paper explores the concept of combining model based design with a runtime framework to realize an easily reprogrammable signal analyzer for embedded COMINT systems. Signal processing experts design algorithms using modeling tools tailored to the domain. The tools produce output that can be loaded directly to the embedded system. Platform independence is achieved by using XML and CORBA as principal elements of the design.

Increasing the capability of CubeSat-based software-defined radio applications

CubeSats are highly accessible as Earth orbiting platforms due to their low costs of development and launch when compared to traditional small satellites. This accessibility, combined with a commensurately short development timeline, can be attributed to the use of commercial-off-the-shelf (COTS) technology. However, COTS components typically have limited inherent resilience to the space environment. As such, CubeSat usage has largely been limited to experiments or applications where high availability is not required. Several technologies are enablers for increased CubeSat performance in the environment of space. Dependable Multiprocessor (DM) technology has demonstrated the capability for high system availability and reliability with COTS processors in a space environment. DM opens many possibilities for high performance, low cost processing in space, supporting technologies such as advanced software defined radios (SDR). SDR technology allows for on-orbit reconfigurability of data management, protocols, multiple access methods, waveforms, and data protection. This paper explores how these enabling technologies hold promise for increasing the availability and capability of CubeSats, allowing CubeSats to be used in advanced applications often associated with military and commercial operations.

Towards a practical cognitive communication network for satellite systems

We present progress toward the formulation of a mathematical model for a cognitive communication network with applications to satellite systems. Our model employs abstract concepts including communicators, communications channels, and demand for capacity. These model elements may be tailored to represent a wide variety of practical communication scenarios. We present a dynamic automated reasoning methodology which uses the model to find communication resource allocations for specific scenarios that are superior to static scheduling approaches. This reasoning process resolves resource dependencies, enforces communication policies, and learns from previous communication attempts. We have implemented this reasoning process using Answer Set Prolog and used it to plan communications for a constellation of 8 satellites and 3 ground stations. The example demonstrates performance improvement over a static scheduling approach and shows how solutions can be found with reasonable computational effort.

A specialized programming language for coordinating software execution timing in embedded systems

We have developed Representation and Implementation of Temporal Event Sequences (RITES), a domain specific programming language which enables users to precisely specify how software and firmware execute with respect to real time on embedded systems hardware. Precise timing of software and firmware operations is critical to many functions within a space system, including coordination of hardware components, scheduling of spacecraft resources, and execution of communications protocols. RITES provides a highly expressive and precise mechanism to specify when software and firmware operations occur. The programming languages commonly used to develop the software and firmware for space systems (i.e. C, C++, and Verilog) do not have a built-in semantic concept of time. In contrast, RITES allows the specification of scheduled behaviors to be made and modified using concepts natural to the scheduling problem and with a compact, intuitive syntax. RITES components coordinate the activities and temporal behavior of other modules within the system rather than encapsulating complete system behavior. The RITES language is supported by a family of code generators that produce executable implementations of RITES programs. Code generators translate RITES programs to C functions for execution as software on sequential processors and to Verilog hardware description language (HDL) modules for execution within Field Programmable Gate Arrays (FPGAs). Additional code generators produce HDL implementations with error tolerance features allowing execution on FPGAs susceptible to single event effects (SEEs) in environments with significant radiation. Specifically, RITES modules may be automatically implemented as Verilog with local or distributed triple modular redundancy (TMR). We provide several examples of the implementation of precision timed behavior at various timing granularities, including clock-by-clock control of a digital signal processing (DSP) core within an FPGA for efficient execution of signal processing applications, implementation of a time division multiple access (TDMA) radio communications protocol, and a detailed study of the configuration and control of an external image compression ASIC.

Data access architectures for high throughput, high capacity flash memory storage systems

We present a design framework and software tools which support the development of high performance, high capacity data storage hardware systems employing flash memory technology. This framework facilitates the design of data storage systems which provide multiple terabits of storage and access and retrieval rates of several gigabits per second. This methodology supports the design of data storage systems with widely varying functional requirements by enabling rapid exploration of the design space, providing automatic validation of functional correctness, and providing accurate quantitative predictions of performance. We present two case studies demonstrating the flexibility and scope of this approach, and describe progress toward the implementation of a prototype data storage system designed using the framework.

Application of an image processing architecture for the Solar Orbiter SPICE instrument

The ongoing development of avionics to support the Spectral Imaging of the Coronal Environment (SPICE) Electronics Box (SEB) program as part of the European Space Agencys (ESA) Solar Orbiter mission has resulted in the development of an Image Processing Field Programmable Gate Array (FPGA) (IPF). The IPF is a single FPGA containing functions to communicate with a Front End Electronics (FEE) assembly/extreme ultraviolet camera, to apply data corrections on incoming pixels, and to compress the final image product for transmission to the ground. The IPF is used as part of a larger science “observation” campaign envisaged as a series of “studies” that are scheduled using a macro execution engine maintained by the Flight Software (FSW). A macro is a lookup table (LUT) stored in memory which contains a series of SPICE commands with relative time tags for each, which determines when each command is executed. This paper discusses the design and architecture of the IPF and associated controlling software employed to meet the various engineering and science requirements of the SPICE instrument.

Flexibility and Extensibilty in the Design of Spacecraft Communications Systems

Southwest Research Institute® (SwRI®) has developed a wireless transceiver that incorporates a flexible and extensible design and implementation strategy, enabling deployment of the radio to numerous roles for space missions. The transceiver was architected such that the software and the hardware could be quickly repurposed based on mission need. The software is written in ANSI standard and object oriented C++, facilitating modularity and functional reuse. The control and processing hardware is reprogrammable, allowing for the same hardware to be used in numerous applications. Although the radio frequency hardware is inherently narrow band in its conversion architecture, careful consideration to the implementation allows for quick, low cost rework to migrate between frequency bands and bandwidths. While the transceiver was originally intended for CubeSat telemetry, tracking, and command, it has now been extended in design for micro-satellite space-ground communication at S-band, micro-satellite inter-satellite crosslink communication at S-band, and small-satellite inter-satellite crosslink at Ka-band. An example of rapid repurposing of the transceiver from a Ka-band crosslink to an S-band crosslink shows the benefits of modularity and hardware/software that is architected for extensibility.