Iterative Decoding and Turbo Equalization: The Z-Crease Phenomenon

Iterative probabilistic inference, popularly dubbed the soft-iterative paradigm, has found great use in a wide range of communication applications, including turbo decoding and turbo equalization. The classic approach of analyzing the iterative approach inevitably use the statistical and information-theoretical tools that bear ensemble-average flavors. This paper consider the per-block error rate performance, and analyzes it using nonlinear dynamical theory. By modeling the iterative processor as a nonlinear dynamical system, we report a universal "Z-crease phenomenon:" the zig-zag or up-and-down fluctuation -- rather than the monotonic decrease -- of the per-block errors, as the number of iteration increases. Using the turbo decoder as an example, we also report several interesting motion phenomenons which were not previously reported, and which appear to correspond well with the notion of "pseudo codewords" and "stopping/trapping sets." We further propose a heuristic stopping criterion to control Z-crease and identify the best iteration. Our stopping criterion is most useful for controlling the worst-case per-block errors, and helps to significantly reduce the average-iteration numbers.Comment: 6 page

It Is Leviathan : Family, Feminism, and American Drama.

American drama has ever occupied a stepchild position in scholarship, its denigration rooted in the lure of domestic realism for even the most resistant of our playwrights. Maligned as solipsistic and regressive, this leviathan of mainstream American theatre putatively upholds through its content the unity of the mythologized family and through its form the closure of classical realism. Yet the legacy of this leviathan is an epistemological subversion and a transformative impulse. Those very plays which apotheosize American domestic realism ironically undermine its foundation in psychological causality, narrative linearity, transparent language, unmediated consciousness, and unified meaning. Destabilizing that objective reality perceived through a binary logic of subject/object, post-war playwrights prophesied a shift from a Cartesian/Newtonian epistemology and bequeathed a legacy of reality as uncertain and boundaries as blurred. Reflecting this postmodern shift in family, feminist, and scientific theories, contemporary playwrights have furthered this legacy of a liminal realism. Critics, however, persist in denouncing mainstream American drama; the most vitriolic among these are feminists who are willing to forego broad audiences so great is their fear of both domesticity\u27s circumscription of women and realism\u27s reinscription of dominant ideology. It is a feminist redemption, then, which proves most persuasive, emerging provocatively from family theory\u27s and feminist film criticism\u27s conceptualization of family and realism respectively as unstable systems. These echo chaos theory\u27s concept of unpredictability in nonlinear dynamical systems, a perspective which reveals alternative futures on America\u27s theatrical and cultural stages. Fittingly, as the imperative of feminism is transformation, its possibility is signalled by female characters in America\u27s linchpin plays. Culturally scripted as ghosts or monsters, these (M) others haunt their houses and the stage as chaos haunts order and performance, text. Derridian hymen or Prigoginian hypnon, they embody the systemic flux of a Butterfly Effect, pushing the family to evolve from a gendered hierarchy and realism from an Oedipal order. From O\u27Neill to Mamet, American playwrights have evoked a consciousness beyond binary logic and negative mimesis, a consciousness which begs a reevaluation of American drama and America itself as liminal realms

Mobile Mapping

This book argues for a theory of mobile mapping, a situated and spatial approach towards researching how everyday digital mobile media practices are bound up in global systems of knowledge and power. Drawing from literature in media studies and geography - and the work of Michel Foucault and Doreen Massey - it examines how geographical and historical material, social, and cultural conditions are embedded in the way in which contemporary (digital) cartographies are read, deployed, and engaged. This is explored through seventeen walking interviews in Hong Kong and Sydney, as potent discourses like cartographic reason continue to transform and weave through the world in ways that haunt mobile mapping and bring old conflicts into new media. In doing so, Mobile Mapping offers an interdisciplinary rethinking about how multiple translations of spatial knowledges between rational digital epistemologies and tacit ways of understanding space and experience might be conceptualized and researched

Unreliable and resource-constrained decoding

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 185-213).Traditional information theory and communication theory assume that decoders are noiseless and operate without transient or permanent faults. Decoders are also traditionally assumed to be unconstrained in physical resources like material, memory, and energy. This thesis studies how constraining reliability and resources in the decoder limits the performance of communication systems. Five communication problems are investigated. Broadly speaking these are communication using decoders that are wiring cost-limited, that are memory-limited, that are noisy, that fail catastrophically, and that simultaneously harvest information and energy. For each of these problems, fundamental trade-offs between communication system performance and reliability or resource consumption are established. For decoding repetition codes using consensus decoding circuits, the optimal tradeoff between decoding speed and quadratic wiring cost is defined and established. Designing optimal circuits is shown to be NP-complete, but is carried out for small circuit size. The natural relaxation to the integer circuit design problem is shown to be a reverse convex program. Random circuit topologies are also investigated. Uncoded transmission is investigated when a population of heterogeneous sources must be categorized due to decoder memory constraints. Quantizers that are optimal for mean Bayes risk error, a novel fidelity criterion, are designed. Human decision making in segregated populations is also studied with this framework. The ratio between the costs of false alarms and missed detections is also shown to fundamentally affect the essential nature of discrimination. The effect of noise on iterative message-passing decoders for low-density parity check (LDPC) codes is studied. Concentration of decoding performance around its average is shown to hold. Density evolution equations for noisy decoders are derived. Decoding thresholds degrade smoothly as decoder noise increases, and in certain cases, arbitrarily small final error probability is achievable despite decoder noisiness. Precise information storage capacity results for reliable memory systems constructed from unreliable components are also provided. Limits to communicating over systems that fail at random times are established. Communication with arbitrarily small probability of error is not possible, but schemes that optimize transmission volume communicated at fixed maximum message error probabilities are determined. System state feedback is shown not to improve performance. For optimal communication with decoders that simultaneously harvest information and energy, a coding theorem that establishes the fundamental trade-off between the rates at which energy and reliable information can be transmitted over a single line is proven. The capacity-power function is computed for several channels; it is non-increasing and concave.by Lav R. Varshney.Ph.D

Computational and Numerical Simulations

Computational and Numerical Simulations is an edited book including 20 chapters. Book handles the recent research devoted to numerical simulations of physical and engineering systems. It presents both new theories and their applications, showing bridge between theoretical investigations and possibility to apply them by engineers of different branches of science. Numerical simulations play a key role in both theoretical and application oriented research

Good Mourning Canada? Canadian Military Commemoration and Its Lost Subjects

Using the Highway of Heroes as my point of departure, in “Good Mourning Canada? Canadian Military Commemoration and its Lost Subjects” I interrogate the role of Canadian military commemoration in the production of hierarchies of grievability and the construction of nationalist narratives. I argue that military commemoration plays a critical role in the performative constitution of the privileged—and the “lost”—subjects of Canadian nationalism. My investigation looks first at how Canadian military memorial projects operate as a means of interpellating Canada’s citizen populations into a particular kind of settler-nationalism, and second, at how performance might serve as a methodology towards the production of counter-memorials that resist the forgetful narratives of Canadian nationalism. My methodological approach weaves historical, theoretical, and performance analyses with first-person reflections on three counter-memorial meditations I performed as a method of embodied inquiry and critical engagement. While the reflective remains of Impact Afghanistan War are scattered throughout this dissertation, and Unravel: A meditation on the warp and weft of militarism and Flag of Tears are discussed explicitly in the final chapters, all three counter-memorial meditations inform—and are informed by—the entire project. Throughout this dissertation I deliberately posit both Canadian military commemoration, and performance, as broadly construed. I investigate repertorial performances of commemoration—like the Highway of Heroes, Remembrance Day ceremonies, and Impact—in addition to the archival performances of institutions and objects—like the Canadian War Museum, military fatigues, and Unravel’s threaded remains. I also intentionally wander outside the constructed borders of Canadian military commemoration to consider how these memorials disappear the violence of settler-colonialism. I bring popular culture performances of nationalist and counter-nationalist narratives—like the Winter Olympics and Jeff Barnaby’s film, Rhymes for Young Ghouls—into conversation with performances overtly linked to the contested terrains of Canadian social memory, like the World War I and II documentary, The Valour and the Horror, and Canada’s Truth and Reconciliation Commission. In bringing this range of performances together under the umbrella of Canadian military commemoration I make visible the larger scenario of Canadian settler nationalism and its sticky “inter(in)animations” with militarism and colonialism.

"Inventories of Limbo": Post-Minimal Aesthetics in Cinema From the Readymade to Institutional Critique

This dissertation charts the philosophical premises of post-minimalism in the practices of experimental filmmakers and video artists, exploring specific reorientations of cinematic works since the late 1960s. Post-minimalism refers to a myriad of aesthetic transformations initiated by the conceptual art movement, interrogating the ontology of art from a perspective outside its historical bonds to medium, style, and Kantian aesthetic judgment. I examine three strategies in the progression of post-minimal aesthetic practice: the readymade, institutional critique, and seriality. A central goal of this research is to remap entrenched language and ideas in the spheres of the arts and cinema to point to a profound reciprocity between cinematic technology and post-minimal aesthetic intelligence, perception, and judgment. This research moves away from the problems raised by artificially constructed movements and prescriptive categories which inevitably produce important sites of exception, and look instead to the aesthetic engines of post-minimal artmaking offering opportunities for constant renewal, evolution, and refinement. I follow these aesthetic engines like a knights tour in chess, jumping through history, appearing in unexpected places and at unexpected times to draw continuities in the approach to the heretical breaks from modernism found in post-minimal aesthetic intelligence. I will primarily focus on four objects: William E. Jones Tearoom, Robert Smithsons Underground Cinema, Lis Rhodes collaborative intervention into the Film as Film exhibition, and Christian Marclays The Clock. Examining the use of Marcel Duchamps concept of the readymade, and its profound assault on both medium specificity and authorship, I illustrate radical new ethical imperatives in the presentation of found footage filmmaking. My two core chapters grapple with ontological and locative explorations of cinematic architectures and sites. The two projects discussed engage with institutional critique, a philosophical model of artmaking which directly engages the sites, economic infrastructures, administrative imperatives, and power dynamics of the cinema, museum, and gallery. Finally, I examine a case study in contemporary post-minimal practice through Christian Marclays 24-hour installation The Clock, and will explore its relationship to archival projects engaging in the collection, ordering, and hermeneutic approach to 20th century media. I will explore this installation as symptomatic of both a technologically determined grammar of collection for the now immense digital archive, and an archeological inclination for artists to thematize film history

Gathering Ecologies

What might an interactive artwork look like that enabled greater expressive potential for all of the components of the event? How can we radically shift our idea of interactivity towards an ecological conception of the term, emphasising the generation of complex relation over the stability of objects and subjects? Gathering Ecologies explores this ethical and political shift in thinking, examining the creative potential of differential relations through key concepts from the philosophies of A.N. Whitehead, Gilbert Simondon and Michel Serres. Utilising detailed examinations of work by artists such as Lygia Clark, Rafael Lozano-Hemmer, Nathaniel Stern and Joyce Hinterding, the book discusses the creative potential of movement, perception and sensation, interfacing, sound and generative algorithmic design to tune an event towards the conditions of its own ecological emergence