Bandwidth efficient CCSDS coding standard proposals

The basic concatenated coding system for the space telemetry channel consists of a Reed-Solomon (RS) outer code, a symbol interleaver/deinterleaver, and a bandwidth efficient trellis inner code. A block diagram of this configuration is shown. The system may operate with or without the outer code and interleaver. In this recommendation, the outer code remains the (255,223) RS code over GF(2 exp 8) with an error correcting capability of t = 16 eight bit symbols. This code's excellent performance and the existence of fast, cost effective, decoders justify its continued use. The purpose of the interleaver/deinterleaver is to distribute burst errors out of the inner decoder over multiple codewords of the outer code. This utilizes the error correcting capability of the outer code more efficiently and reduces the probability of an RS decoder failure. Since the space telemetry channel is not considered bursty, the required interleaving depth is primarily a function of the inner decoding method. A diagram of an interleaver with depth 4 that is compatible with the (255,223) RS code is shown. Specific interleaver requirements are discussed after the inner code recommendations

Actionable Intelligence-Oriented Cyber Threat Modeling Framework

Amid the growing challenges of cybersecurity, the new paradigm of cyber threat intelligence (or CTI) has gained momentum to better deal with cyber threats. There, however, has been one fundamental and very practical problem of information overload organizations face in constructing an effective CTI program. We developed a cyber threat intelligence prototype that automatically and dynamically performs the correlation of business assets, vulnerabilities, and cyber threat information in a scoped setting to remediate the challenge of information overload. Conveniently called TIME (for Threat Intelligence Modeling Environment), it repeats the cycle of: (1) collect internal asset data; (2) gather vulnerability and threat data; (3) correlate vulnerabilities with assets; and (4) derive CTI and alerts significant internal asset-related vulnerabilities in a timely manner. For this, it takes advantage of CTI reports produced by online sites and several NIST standards intended to formalize vulnerability and threat management

The Manifestation of Stopping Sets and Absorbing Sets as Deviations on the Computation Trees of LDPC Codes

The error mechanisms of iterative message-passing decoders for low-density parity-check codes are studied. A tutorial review is given of the various graphical structures, including trapping sets, stopping sets, and absorbing sets that are frequently used to characterize the errors observed in simulations of iterative decoding of low-density parity-check codes. The connections between trapping sets and deviations on computation trees are explored in depth using the notion of problematic trapping sets in order to bridge the experimental and analytic approaches to these error mechanisms. A new iterative algorithm for finding low-weight problematic trapping sets is presented and shown to be capable of identifying many trapping sets that are frequently observed during iterative decoding of low-density parity-check codes on the additive white Gaussian noise channel. Finally, a new method is given for characterizing the weight of deviations that result from problematic trapping sets

A simulation study of the performance of the NASA (2,1,6) convolutional code on RFI/burst channels

In an earlier report, the LINKABIT Corporation studied the performance of the (2,1,6) convolutional code on the radio frequency interference (RFI)/burst channel using analytical methods. Using an R(sub 0) analysis, the report concluded that channel interleaving was essential to achieving reliable performance. In this report, Monte Carlo simulation techniques are used to study the performance of the convolutional code on the RFI/burst channel in more depth. The basic system model under consideration is shown. The convolutional code is the NASA standard code with generators g(exp 1) = 1+D(exp 2)+D(exp 3)+D(exp 5)+D(exp 6) and g(exp 2) = 1+D+D(exp 2)+D(exp 3)+D(exp 6) and d(sub free) = 10. The channel interleaver is of the convolutional or periodic type. The binary output of the channel interleaver is transmitted across the channel using binary phase shift keying (BPSK) modulation. The transmitted symbols are corrupted by an RFI/burst channel consisting of a combination of additive white Gaussian noise (AWGN) and RFI pulses. At the receiver, a soft-decision Viterbi decoder with no quantization and variable truncation length is used to decode the deinterleaved sequence

Search for optimal distance spectrum convolutional codes

In order to communicate reliably and to reduce the required transmitter power, NASA uses coded communication systems on most of their deep space satellites and probes (e.g. Pioneer, Voyager, Galileo, and the TDRSS network). These communication systems use binary convolutional codes. Better codes make the system more reliable and require less transmitter power. However, there are no good construction techniques for convolutional codes. Thus, to find good convolutional codes requires an exhaustive search over the ensemble of all possible codes. In this paper, an efficient convolutional code search algorithm was implemented on an IBM RS6000 Model 580. The combination of algorithm efficiency and computational power enabled us to find, for the first time, the optimal rate 1/2, memory 14, convolutional code

Is This Transfer Shock ? Examining the Perceptions of Engineering Students Who Articulate Within the Irish Higher Education Context.

Abstract—“Transfer shock” is a well-known phenomenon during the process of articulation, when students move from short-cycle applied programs to more academic longer-cycle study programs. In the US context this problematic transition has been observed in students transferring from community colleges into the traditional university system. In Ireland’s binary higher education structure, one set of institutions, known as Institutes of Technology (IoTs) allow for this transition to take place entirely within individual institutions. This paper is part of an ongoing investigation into one such IoT, where engineering students who achieve high grades at the end of 3-year (so-called Level 7) “ordinary degree” programs frequently transfer into the 3rd year of 4-year Level 8 “honors degree” programs, with surprisingly successful outcomes. One surprise derives from the fact that the students who enter Level 7 engineering programs are deemed at the outset to be academically less able, particularly in mathematics, than those who go directly into Level 8 programs from secondary school. Relatively little work has been done on this transition to date. In the 3rd and 4th year of many honors engineering programs within this institution it is not unusual to have 30-50% of the students coming from an ordinary degree background, the majority from within the institution itself – with others transferring from other IoTs in Ireland. Previous research has shown that students from this background initially struggle in the 3rd year of the honors degree program when compared with students who have proceeded directly through the honors program, before going on to successfully graduate. Can this be attributed to ‘transfer shock’; even though most of these students are continuing in an institution and with faculty that they are already familiar with? In order to examine this phenomenon we interview students from several engineering disciplines at various points in this transition. We explore the perceptions of the students regarding this transition and, based on the information coming from the interviews, we conduct a large scale survey to be administered to articulating students across engineering programs in the institution. The preliminary results of this survey are also presented here

The Link between Spatial Skills and Engineering Problem-Solving

Well-developed 3-D spatial skills are correlated with engineering success. However, most studies examining the link between spatial skills and engineering success have been conducted at the macro level, i.e., the link between spatial skills and course grades or between spatial skills and graduation rates. In this research, a more refined approach has been taken. Relationships between spatial skills and success in solving certain types of problems that engineering students commonly encounter are examined. It was found that high levels of spatial skills predict success in solving certain types of engineering problems but not in all types of problems. Data gathered through this research will be further analyzed to determine characteristics of problems where spatial skills appear to play a role and characteristics where they do not

Beyond the CNS: The many peripheral roles of APOE

Apolipoprotein E (APOE) is a multifunctional protein synthesized and secreted by multiple mammalian tissues. Although hepatocytes contribute about 75% of the peripheral pool, APOE can also be expressed in adipose tissue, the kidney, and the adrenal glands, among other tissues. High levels of APOE production also occur in the brain, where it is primarily synthesized by glia, and peripheral and brain APOE pools are thought to be distinct. In humans, APOE is polymorphic, with three major alleles (e2, e3, and e4). These allelic forms dramatically alter APOE structure and function. Historically, the vast majority of research on APOE has centered on the important role it plays in modulating risk for cardiovascular disease and Alzheimer's disease. However, the established effects of this pleiotropic protein extend well beyond these two critical health challenges, with a demonstrated roles for APOE across a wide spectrum of biological conditions, including adipose tissue function and obesity, metabolic syndrome and diabetes, fertility and longevity, and immune function. While the spectrum of biological systems in which APOE plays a role seems implausibly wide at first glance, there are some potential unifying mechanisms that could tie these seemingly disparate disorders together. In the current review, we aim to concisely summarize a wide breadth of APOE-associated pathologies and to analyze the influence of APOE in the development of several distinct disorders in order to provide insight into potential shared mechanisms implied in these various pathophysiological processes

Connes' embedding problem and Tsirelson's problem

We show that Tsirelson's problem concerning the set of quantum correlations and Connes' embedding problem on finite approximations in von Neumann algebras (known to be equivalent to Kirchberg's QWEP conjecture) are essentially equivalent. Specifically, Tsirelson's problem asks whether the set of bipartite quantum correlations generated between tensor product separated systems is the same as the set of correlations between commuting C*-algebras. Connes' embedding problem asks whether any separable II$_1$ factor is a subfactor of the ultrapower of the hyperfinite II$_1$ factor. We show that an affirmative answer to Connes' question implies a positive answer to Tsirelson's. Conversely, a positve answer to a matrix valued version of Tsirelson's problem implies a positive one to Connes' problem