Global Broadcast Research Articles

Assessment and Comparison of Broadcast Ionospheric Models: NTCM-BC, BDGIM, and Klobuchar

For single-frequency Global Navigation Satellite Systems (GNSSs) users, ionospheric delay is the main error source affecting the accuracy of positioning. Applying a broadcast ionospheric correction model to mitigate the ionospheric delay is essential for meter-to-decimeter-level accuracy positioning. To provide support for real-time single-frequency operations, particularly in the China area, we assessed the performance of three broadcast ionospheric correction models, namely, the Neustrelitz total electron content (TEC) broadcast model (NTCM-BC), the BeiDou global broadcast ionospheric delay correction model (BDGIM), and the Klobuchar model. In this study, the broadcast coefficients of Klobuchar and BDGIM are obtained from the navigation data files directly. Two sets of coefficients of NTCM-BC for China and global areas are estimated. The slant total electron contents (STEC) data from more than 80 validation stations and the final vertical TEC (VTEC) data of the Center for Orbit Determination in Europe (CODE) are used as independent benchmarks for comparison. Compared to GPS STEC during the period of Day of Year (DOY) 101~199, 2019, the ionospheric correction ratio of NTCM-BC, BDGIM, and Klobuchar are 79.4%, 64.9%, and 57.7% in China, respectively. For the global area, the root-mean-square (RMS) errors of these three models are 3.67 TECU (1 TECU = 1016 electrons/m2), 5.48 TECU, and 8.92 TECU, respectively. Compared to CODE VTEC in the same period, NTCM-BC, BDGIM, and Klobuchar can correct 72.6%, 69.8%, and 61.7% of ionospheric delay, respectively. Hence, NTCM-BC is recommended for use as the broadcast ionospheric model for the new-generation BeiDou satellite navigation system (BDS) and its satellite-based augmentation system.

SIS accuracy and service performance of the BDS-3 basic system

On December 27, 2018, the basic system of the third-generation BeiDou navigation satellite system (BDS-3) completed the deployment of its constellation of 18 MEO networking satellites as well as the construction of the operation control system (OCS) and began to provide basic navigation services to users worldwide. Compared with BDS-2, BDS-3 aims to offer users better navigation signals and higher precision with a series of new technologies. For example, the spaceborne atomic clock of BDS-3 is upgraded for higher performance, the Ka-band inter-satellite link is adopted for inter-satellite ranging and communication, and new B1C and B2a signals are broadcast in addition to B1I and B3I signals (compatible with BDS-2). In addition, a 9-parameter model based on a spherical harmonic function is employed for ionospheric delay corrections. Using the observation data from 18 satellites of the basic system, this paper conducts a comprehensive evaluation of the pseudorange measurement characteristics, signal-in-space (SIS) accuracy of navigation messages and global service capability of BDS-3. The results indicate that the pseudorange measurement multipath effect and observation noise of BDS-3 satellites are better than those of BDS-2; additionally, with the support of inter-satellite links, the user range error (URE) of the BDS-3 satellite broadcast ephemeris is better than 10 cm, the precision of the broadcast clock parameter is better than 1.5 ns, and the SIS accuracy is better than 0.6 m overall. Different from the traditional Klobuchar model, the BeiDou global broadcast ionospheric delay correction model (BDGIM) can provide ionospheric delay corrections better than 70% for worldwide single-frequency users. The service capability evaluation of the basic system consists mainly of the accuracy improvement of the B1I and B3I signals according to BDS-2 as well as the global positioning accuracy of the new signals. These results prove that the BDS-3 basic system has achieved the design goal; that is, both the horizontal and the vertical global positioning accuracies are better than 10 m (95%). In the future, 6 MEO satellites as well as 3 GEO satellites and 3 IGSO satellites for regional enhancement purposes will be deployed for full operation; consequently, BDS-3 will definitely provide a higher SIS accuracy and better service capability.

Nonconscious Pain, Suffering, and Moral Status

Pain is an unwanted mental state that is often considered a sufficient ground for moral status. However, current science and philosophy of mind suggest that pains, like other perceptual states, might be nonconscious. This raises the questions of whether the notion of nonconscious pain is coherent and what its moral significance might be. In this paper I argue that the existence of nonconscious pain is conceptually coherent; however as a matter of fact our brains might always represent pains consciously. I then characterize the concept of suffering from a naturalistic perspective, distinguishing it from pain. I offer an account of suffering based on some current theories of consciousness, in which suffering consists in the global broadcasting of representations with overall net negative valence. I argue this can explain most of suffering’s properties, such as its wholeness, significance for welfare, and conscious character. Finally, I contend that suffering, but not pain, provides sufficient grounds for moral status.

Distributed robust time-efficient broadcasting algorithms for multi-channel wireless multi-hop networks with channel disruption

Broadcasting is a fundamental problem for wireless multi-hop networks such as wireless ad hoc and sensor networks. In this paper, we study distributed robust time-efficient global broadcasting for SINR-based (i.e., Signal-to-Interference-plus-Noise-Ratio-based) multi-channel wireless multihop networks subject to channel disruption. In this study, we make the following assumptions: i) for successful packet reception, the SINR at receivers must exceed a certain threshold; ii) an adversary exists in the network, which uniformly and randomly chooses t > 0 channels to disrupt from total F > 1 available channels in every round. To address the broadcasting issue in such networks, we first propose a degree-aware broadcasting algorithm and then propose a degree-independent broadcasting algorithm. The proposed algorithms elaborately integrate distributed channel selection and transmission scheduling at different nodes while considering the following factors: the impact of SINR constraint, availability of channels, sending probability on selected channel, presence of adversary, with and without node degree information. We present the detailed design of the two algorithms. We deduce their worst-case time performance to accomplish the task of global broadcasting with high probability. We further prove that both algorithms can still preserve the same time performance under more powerful oblivious adversary and weakly adaptive adversary. Simulation results show that the proposed algorithms have satisfactory average-case time performance.

Global Workspace Theory and Animal Consciousness

Peter Carruthers has recently argued for a surprising conditional: if a global workspace theory of phenomenal consciousness is both correct and fully reductive, then there are no substantive facts to discover about phenomenal consciousness in nonhuman animals. I present two problems for this conditional. First, it rests on an odd double-standard about the ordinary concept of phenomenal consciousness: its intuitive non-gradability is taken to be unchallengeable by future scientific developments, whereas its intuitive determinacy is predicted to fall by the wayside. Second, it relies on dismissing, prematurely, the live empirical possibility that phenomenal consciousness may be linked to a core global broadcast mechanism that is (determinately) shared by a wide range of animals. Future developments in the science of consciousness may lead us to reconsider the non-gradability of phenomenal consciousness, but they are unlikely to lead us to accept that there are no facts to discover outside the paradigm case of a healthy adult human.

On simple back-off in unreliable radio networks

In this paper, we study local and global broadcast in the dual graph model, which describes communication in a radio network with both reliable and unreliable links. Existing work proved that efficient solutions to these problems are impossible in the dual graph model under standard assumptions. In real networks, however, simple back-off strategies tend to perform well for solving these basic communication tasks. We address this apparent paradox by introducing a new set of constraints to the dual graph model that better generalize the slow/fast fading behavior common in real networks. We prove that in the context of these new constraints, simple back-off strategies now provide efficient solutions to local and global broadcast in the dual graph model. We also precisely characterize how this efficiency degrades as the new constraints are reduced down to non-existent, and prove new lower bounds that establish this degradation as near optimal for a large class of natural algorithms. We conclude with an analysis of a more general model where we propose an enhanced back-off algorithm. These results provide theoretical foundations for the practical observation that simple back-off algorithms tend to work well even amid the complicated link dynamics of real radio networks.

The cost of global broadcast in dynamic radio networks

We study the time complexity of single and multi token broadcast in adversarial dynamic radio networks. Initially, k tokens (which are k pieces of information) are distributed among the n nodes of a network and all the tokens need to be disseminated to all the nodes in the network. We first consider the single-token broadcast problem (i.e., the case k=1). By presenting upper and lower bounds, we show that the time complexity of single-token broadcast depends on the amount of stability and connectivity of the dynamic network topology and on the adaptiveness of the adversary providing the dynamic topology. Then, we give two generic algorithms which allow to transform generalized forms of single-token broadcast algorithms into multi-token broadcast (k-token broadcast) algorithms. Based on these generic algorithms, we obtain k-token broadcast algorithms for a number of different dynamic network settings. For one of the modeling assumptions, our algorithm is complemented by a lower bound which shows that the upper bound is close to optimal.

Symmetry Incorporated Cost-Effective Architectures for Two-Dimensional Digital Filters

Professor Fettweis as far back as 1977 published a paper generalizing McClellan transformation to obtain circular symmetry in 2-D and spherical, hyper-spherical symmetries in multidimensional digital filters [1]. This survey paper presents stateof-the-art two-dimensional (2-D) VLSI digital filter architectures possessing various symmetries in the filter magnitude response. Preceding the symmetry structures, a generalized formulation is given that allows the derivation of various new 2-D VLSI filter structures of any order without global broadcast. Following this, two types (namely, Type 1 [20] and Type 3 [21], [25], [26]) of cost-effective 2-D magnitude symmetry filter architectures possessing diagonal, four-fold rotational, quadrantal, and octagonal symmetries with reduced number of multipliers are given. By combining the identities of the Types-1 and 3 symmetry filter structures, multimode 2-D symmetry filters which enable the above four symmetry modes are discussed. The Type-1 and Type-3 multimode filters can result in a 65.3% cost reduction in terms of number of multipliers compared with the sum of the multipliers of the four individual Type-1 symmetry filter structures studied in this paper. Furthermore, Type-3 has shorter critical path than Type-1 multimode filter. The paper is concluded with the presentation of a 2-D filter design example and a corresponding structure.

Mathematical modelling and analysis of hierarchical modulation in AWGN and Rayleigh channel

In digital video broadcasting either multi-frequency or single frequency network is used to transmit local and global broadcasting contents respectively. Multi-frequency network consumes large spectrum to transmit local information alone. Therefore an efficient technique is required to embed both local and global content in single constellation. In this paper, hierarchical modulation or multilayered modulation is employed to satisfy this requirement in which the task is achieved by layered constellation. The base layer carries the high priority global contents and the low priority information is carried by the enhancement layer. The performance of the system is highly determined by the detection rules and the coder chosen. The performance of hierarchical modulation system is analysed by framing decision rules for both high priority and low priority streams. In addition to derivation of probability of error of the system, the analysis of bit error rate of coded and uncoded system is done. Convolutional encoder with code rate 1/3, 1/2 and 2/3 is used in this paper.

The BeiDou global broadcast ionospheric delay correction model (BDGIM) and its preliminary performance evaluation results

A global ionospheric delay correction model (BeiDou global broadcast ionospheric delay correction model [BDGIM]) is proposed for the single-frequency ionospheric delay correction of the third phase of the BeiDou navigation satellite system (BDS-3). An initial performance assessment of BDGIM was conducted with data collected in China and worldwide. For regional analysis, the broadcast coefficients of BDGIM were provided by the operational control system of BDS, while for global analysis, the coefficients of BDGIM were estimated using global positioning system (GPS)-derived total electron contents (TECs) obtained from 19 globally distributed monitoring sites. In China, the performance of BDGIM was evaluated by GPS-TEC derived from 40 test sites during day of year (DOY) 060 to 181, 2015. The ionospheric errors can be mitigated by 80.9% for BDGIM. On the global scale, the ionospheric TECs derived from 50 sites of the International Global Navigation Satellite System (GNSS) Services (IGS) were used as references during DOY 220 to 365, 2014, and BDGIM can correct for 77.6% of the ionospheric delay.

The development of Complex Emergent Modularity: A reply to Favela, Amon, & van Rooij (2018)

In our reply to Favela, Amon, & van Rooij (2018) we note points of agreement such as the necessity for the interaction between components in a system for it to be complex emergent and that the Dual Processes approach to human thinking has limitations. We also discuss several critical points of disagreement with the paper. We assert that Complex Emergent Modularity (CEM) does not proliferate the interaction problem but instead proposes a solution to the problem based on the contribution of the global workspace and the process of global broadcast. The nature of the entities which interact is described and emphasized as central to CEM theory.

Comparative psychology without consciousness.

The goal of this paper is to establish the truth of the following conditional: if a global workspace theory of phenomenal consciousness is correct, and is fully reductive in nature, then we should stop asking questions about consciousness in nonhuman animals-not because those questions are too hard to answer, but because there are no substantive facts to discover. The argument in support of this conditional turns on the idea that while global broadcasting is all-or-nothing in the human mind, it is framed in terms that imply gradations across species. Yet our concept of phenomenal consciousness doesn't permit mental states to be to some degree conscious. Before getting to that argument, however, and in order to motivate the subsequent discussion, some of the virtues of global workspace theory are displayed.

Xi Jinping, China, Africa, and Global Realignment

This presentation is on “Xi Jinping, China, Africa, and Global Realignment”. It deals with the changing power relations and how various countries and regions react to those changes. Roughly two years ago, the international version of Central China Television, CCTV, changed its name and brand to that of China Global Television Network, CGTN. The objective was to defend and promote Chinese policies globally probably in competition with other giant global television networks in advancing the interests of their home countries. The BBC, for instance, makes effort, mostly in subtle ways, to promote British policies worldwide and sound credible. CGTN was seemingly to do the same for China. It initially established two global broadcast centers, the main one in Beijing and the second one in Nairobi to cover the entire Africa. Then it added Washington as the third center. Thus CGTN drives Xi Jinping’s development global agenda from the triangular perspective of Beijing, Nairobi, and Washington. This is part of China’s global power projection. Key words : Xi Jinping, China, Africa, Geopolitics, Policy

KDSR

This article deals with a key distribution protocol to secure routing in large-scale Wireless Sensor Networks (WSNs) and proposes a new protocol called KDSR. The authors' protocol has two originalities: to provide a secure network structure for large-scale WSNs, and to use lightweight local process to share efficiently the Local Broadcast Keys, the Pairwise Keys and the Global Broadcast Key. These keys are useful to secure several communication patterns in WSNs: one-to-many, one-to-one and one-to-all. Security analyses show that KDSR can withstand several attacks against WSNs. Through fast node revocation process, KDSR offers a good resilience against node capture. Immunity against MiM and replay attacks are well checked with the AVISPA tools. The experimentations are done on real TelosB motes and through the TOSSIM simulator. Simulation results confirm that KDSR is scalable, provides a good key connectivity and a good resilience. Comparison to earlier work shows that KDSR causes less computation complexity, less communication overhead and much less storage space even for large-scale WSNs.

Exploring the Role of Social Media and Individual Behaviors in Flood Evacuation Processes: An Agent‐Based Modeling Approach

AbstractFlood warnings from various information sources are important for individuals to make evacuation decisions during a flood event. In this study, we develop a general opinion dynamics model to simulate how individuals update their flood hazard awareness when exposed to multiple information sources, including global broadcast, social media, and observations of neighbors' actions. The opinion dynamics model is coupled with a traffic model to simulate the evacuation processes of a residential community with a given transportation network. Through various scenarios, we investigate how social media affect the opinion dynamics and evacuation processes. We find that stronger social media can make evacuation processes more sensitive to the change of global broadcast and neighbor observations, and thus, impose larger uncertainty on evacuation rates (i.e., a large range of evacuation rates corresponding to sources of information). For instance, evacuation rates are lower when social media become more influential and individuals have less trust in global broadcast. Stubborn individuals can significantly affect the opinion dynamics and reduce evacuation rates. In addition, evacuation rates respond to the percentage of stubborn agents in a nonlinear manner, i.e., above a threshold, the impact of stubborn agents will be intensified by stronger social media. These results highlight the role of social media in flood evacuation processes and the need to monitor social media so that misinformation can be corrected in a timely manner. The joint impacts of social media, quality of flood warnings, and transportation capacity on evacuation rates are also discussed.

What is consciousness, and could machines have it?

The controversial question of whether machines may ever be conscious must be based on a careful consideration of how consciousness arises in the only physical system that undoubtedly possesses it: the human brain. We suggest that the word "consciousness" conflates two different types of information-processing computations in the brain: the selection of information for global broadcasting, thus making it flexibly available for computation and report (C1, consciousness in the first sense), and the self-monitoring of those computations, leading to a subjective sense of certainty or error (C2, consciousness in the second sense). We argue that despite their recent successes, current machines are still mostly implementing computations that reflect unconscious processing (C0) in the human brain. We review the psychological and neural science of unconscious (C0) and conscious computations (C1 and C2) and outline how they may inspire novel machine architectures.

Networked SIS Epidemics With Awareness

We study a susceptible-infected-susceptible epidemic process over a static contact network where the nodes have partial information about the epidemic state. They react by limiting their interactions with their neighbors when they believe the epidemic is currently prevalent. A node’s awareness is weighted by the fraction of infected neighbors in their social network, and a global broadcast of the fraction of infected nodes in the entire network. The dynamics of the benchmark (no awareness) and awareness models are described by discrete-time Markov chains, from which mean-field approximations (MFAs) are derived. The states of the MFA are interpreted as the nodes’ probabilities of being infected. We show a sufficient condition for the existence of a “metastable,” or endemic, state of the awareness model coincides with that of the benchmark model. Furthermore, we use a coupling technique to give a full stochastic comparison analysis between the two chains, which serves as a probabilistic analog to the MFA analysis. In particular, we show that adding awareness reduces the expectation of any epidemic metric on the space of sample paths, e.g., eradication time or total infections. We characterize the reduction in expectations in terms of the coupling distribution. In simulations, we evaluate the effect social distancing has on contact networks from different random graph families (geometric, Erdős-Renyi, and scale-free random networks).

Global Representations of Goal-Directed Behavior in Distinct Cell Types of Mouse Neocortex

SUMMARYThe successful planning and execution of adaptive behaviors in mammals may require long-range coordination of neural networks throughout cerebral cortex. The neuronal implementation of signals that could orchestrate cortex-wide activity remains unclear. Here, we develop and apply methods for cortex-wide Ca2+ imaging in mice performing decision-making behavior and identify a global cortical representation of task engagement encoded in the activity dynamics of both single cells and superficial neuropil distributed across the majority of dorsal cortex. The activity of multiple molecularly defined cell types was found to reflect this representation with type-specific dynamics. Focal optogenetic inhibition tiled across cortex revealed a crucial role for frontal cortex in triggering this cortex-wide phenomenon; local inhibition of this region blocked both the cortex-wide response to task-initiating cues and the voluntary behavior. These findings reveal cell-type-specific processes in cortex for globally representing goal-directed behavior and identify a major cortical node that gates the global broadcast of task-related information.

A Unified Model for BDS Wide Area and Local Area Augmentation Positioning Based on Raw Observations.

In this study, a unified model for BeiDou Navigation Satellite System (BDS) wide area and local area augmentation positioning based on raw observations has been proposed. Applying this model, both the Real-Time Kinematic (RTK) and Precise Point Positioning (PPP) service can be realized by performing different corrections at the user end. This algorithm was assessed and validated with the BDS data collected at four regional stations from Day of Year (DOY) 080 to 083 of 2016. When the users are located within the local reference network, the fast and high precision RTK service can be achieved using the regional observation corrections, revealing a convergence time of about several seconds and a precision of about 2–3 cm. For the users out of the regional reference network, the global broadcast State-Space Represented (SSR) corrections can be utilized to realize the global PPP service which shows a convergence time of about 25 min for achieving an accuracy of 10 cm. With this unified model, it can not only integrate the Network RTK (NRTK) and PPP into a seamless positioning service, but also recover the ionosphere Vertical Total Electronic Content (VTEC) and Differential Code Bias (DCB) values that are useful for the ionosphere monitoring and modeling.

A role for the anterior insular cortex in the global neuronal workspace model of consciousness.

According to the global neuronal workspace model of consciousness, consciousness results from the global broadcast of information throughout the brain. The global neuronal workspace is mainly constituted by a fronto-parietal network. The anterior insular cortex is part of this global neuronal workspace, but the function of this region has not yet been defined within the global neuronal workspace model of consciousness. In this review, I hypothesize that the anterior insular cortex implements a cross-modal priority map, the function of which is to determine priorities for the processing of information and subsequent entrance in the global neuronal workspace.