Early Neighbor Rejection-Aided Tabu Search Detection for Large MIMO Systems

In this study, a low complexity tabu search (TS) algorithm for multiple-input multiple-output (MIMO) systems is proposed. To reduce the computational complexity of the TS algorithm, early neighbor rejection (ENR) and layer ordering schemes are employed. In the proposed ENR-aided TS (ENR-TS) algorithm, the least promising k neighbors are excluded from the neighbor set in each layer, which reduces the computational complexity of neighbor examination in each TS iteration. For efficient computation of the neighbors’ metrics, the ENR scheme can be incorporated into QR decomposition-aided TS (ENR-QR-TS). To further reduce the complexity and improve the performance of the ENR-QR-TS scheme, a layer ordering scheme is employed. The layer ordering scheme determines the order in which layers are detected based on their expected metrics, which reduces the risk of excluding likely neighbors in early layers. The simulation results show that the ENR-TS achieves nearly the same performance as the conventional TS while providing up to 82% complexity reduction.

Robust Object Detection in Colour Images Using a Multivariate Percentage Occupancy Hit-or-Miss Transform

The extension of Mathematical Morphology to colour and multivariate images is challenging due to the need to define a total ordering in the colour space. No one general way of ordering multivariate data exists and, therefore, there is no single, definitive way of performing morphological operations on colour images. In this paper, we propose an extension to mathematical morphology, based on reduced ordering, specifically the morphological Hit-or-Miss Transform which is used for object detection. The reduced ordering employed transforms multivariate observations to scalar comparisons allowing for an order to be derived and for both flat and non-flat structuring elements to be used. We also compare other definitions of the Hit-or-Miss Transform and test alternative colour ordering schemes presented in the literature. Our proposed method is shown to be intuitive and outperforms other approaches to multivariate Hit-or-Miss Transforms. Furthermore, methods of setting the parameters of the proposed Hit-or-Miss Transform are introduced in order to make the transform robust to noise and partial occlusion of objects and, finally, a set of design tools are presented in order to obtain optimal values for setting these parameters accordingly.

Generalized Weyl Quantization and Time

This work presents quantization of time of arrival functions using generalized Stratonovich-Weyl quantization. We take into account the ordering problems involved, mainly the Born-Jordan and the symmetric ordering schemes. We call attention to the combination of the group theoretic methods usually employed in Weyl quantization with the implementation of different ordering schemes via integral kernel factors. It is possible to, and we do, apply the Pegg-Barnett method to the quantization of time to address physical issues such as boundedness and self-adjointness.

Ordering of Trotterization: Impact on Errors in Quantum Simulation of Electronic Structure

Trotter–Suzuki decompositions are frequently used in the quantum simulation of quantum chemistry. They transform the evolution operator into a form implementable on a quantum device, while incurring an error—the Trotter error. The Trotter error can be made arbitrarily small by increasing the Trotter number. However, this increases the length of the quantum circuits required, which may be impractical. It is therefore desirable to find methods of reducing the Trotter error through alternate means. The Trotter error is dependent on the order in which individual term unitaries are applied. Due to the factorial growth in the number of possible orderings with respect to the number of terms, finding an optimal strategy for ordering Trotter sequences is difficult. In this paper, we propose three ordering strategies, and assess their impact on the Trotter error incurred. Initially, we exhaustively examine the possible orderings for molecular hydrogen in a STO-3G basis. We demonstrate how the optimal ordering scheme depends on the compatibility graph of the Hamiltonian, and show how it varies with increasing bond length. We then use 44 molecular Hamiltonians to evaluate two strategies based on coloring their incompatibility graphs, while considering the properties of the obtained colorings. We find that the Trotter error for most systems involving heavy atoms, using a reference magnitude ordering, is less than 1 kcal/mol. Relative to this, the difference between ordering schemes can be substantial, being approximately on the order of millihartrees. The coloring-based ordering schemes are reasonably promising—particularly for systems involving heavy atoms—however further work is required to increase dependence on the magnitude of terms. Finally, we consider ordering strategies based on the norm of the Trotter error operator, including an iterative method for generating the new error operator terms added upon insertion of a term into an ordered Hamiltonian.

A new heuristics for the event ordering in binary decision diagram applied in fault tree analysis

Fault tree is a common approach in probabilistic risk assessment of complex engineering systems. Since their introduction, binary decision diagrams proved to be a valuable tool for complete quantification of hard fault tree models. As is known, the size of the binary decision diagram representation is mainly determined by the quality of the selected fault tree event ordering scheme. Finding the optimal event ordering for binary decision diagram representation is a computationally intractable problem, for which reason heuristic approaches are applied to find reasonable good ordering schemes. The existing method for finding optimal ordering schemes related to special types of fan-in 2 read-once formulas is employed in our research to develop a new heuristic for fault tree. Various fault tree simplification methods are used for the sake of reducing fault tree model discrepancy from fan-in 2 read-once formulas. The reduced fault tree is traversed in a depth-first manner, as for every gate, the best ordering scheme is chosen from selected sets of input permutations. The quality of the final event ordering scheme is compared to orderings produced with depth-first left most heuristic on a set of fault tree models addressed in the literature as well as on a set of our hard models. Our method proves to be a useful heuristic for finding good static event ordering, and it compares favourably to the known heuristic based on a depth-first left most assignment approach.

Transversal city and transtopia – reflecting and analyzing migration, the city, and “the urban” after the postmigrant city

“Transversal city” and transtopia are an invitation to rethink, conceptually and empirically, our urban future. Individual actors, persons with and without migration/flight background, today appear more and more transversal with respect to how they perceive the world, how they give themselves an identity, how they confront others, and how they observe, reflect, and produce knowledge. Previous “modern” static, clearly defined, and discernible constructions of belonging, which follow the “either/or” logic of socio-structural statistical ordering schemes, are actively rejected in a reflected way. Instead, belonging and identity are constructed individually following a reasoning which is transversal: spontaneously, situationally, by improvisation, oriented to potentials, crossing boundaries, transgressing, and generating abstract order and multiple references. Observed transgressive tendencies are discussed starting from a postmigrant perspective, which is part of the recent migration discourse. By identification of four main characteristic discursive moments, transversality is conceptualized, analyzed, and differentiated from the explicitly postmigrant perspective, which is part of the critical perspective. Instead, the concept of the “transversal city” arises with its changed modes of knowledge production, its consequences for social justice and sustainable development, and the evolution of a new processuality of governance, in politics and planning, urban agendas, and the production of “the urban”.

Typologie und Klassifikation in Sozialer Arbeit und Sozialpolitik

Basic questions relating to typologies and classifications shape the discussions in social work and social policy, but have not yet been systematically addressed. This study first explains the foundations of those two ordering schemes in terms of their theory, methodology and definition. Subsequently, it explains their different perspectives and uses in social work and social policy and discusses questions about their relation to each other and their options for use. Among other things, it is important to find out whether the ordering schemes, as medium-range theories, can build communicative bridges between the formative individual case perspective of social work and the formative aggregated perspective of social policy. These considerations, together with the results of a qualitative survey of experts at several US universities, lead to a discussion of the advantages and disadvantages of regulatory schemes and to the presentation of a test catalogue of their critical use in theory and practice.

The Functions of Constitutional Identity Performed in the Context of Constitutionalization of the EU Order and Europeanization of the Legal Orders of EU Member States

This article provides an analysis of the functions performed by constitutional identity in constitutional discourses of both the EU and its Member States, in the context of emerging post-Westphalian and supranational constitutionalism. The analysis tries to demonstrate that constitutional identity may serve as one of the key normative ideologies, legitimation strategies and ordering schemes of EU constitutionalism. It reasserts through functional analysis the suitability of constitutional identity for organizing and explaining multiple constitutional orders in a non-hierarchical and inclusive way. The article is based on a socio-legal approach, deliberately avoiding the predominant legal realist and legal positivist discourses. This is due to the fact that a functional analysis presupposes admitting the existence of ideal, legal and socio-legal dimensions of constitutional concepts and institutions and the taking into account of social implications produced by their functioning. The article deliberately takes a constitutionalist stance on the EU and the EU integration. It is focused on the contribution of constitutional identity for the further constitutionalization of the EU from a socio-political and constitutionalist perspective.

Implementation Strategies for High-Performance Multiuser MIMO Precoders

The multiuser MIMO environment enables the communication between a base-station and multiple users with several antennas. In such a scenario, the use of precoding techniques is required in order to detect the signal at the users' terminals without any cooperation between them. This contribution presents various designs and hardware implementations of a high-capacity precoder based on vector perturbation. To this aim, three tree-search techniques and their associated user-ordering schemes are investigated in this chapter: the well-known K-Best precoder, the fixed-complexity Fixed Sphere Encoder (FSE), and the variable complexity Single Best-Node Expansion (SBE). All of the aforementioned techniques aim at finding the most suitable perturbation vector within an infinite lattice without the high computational complexity of an exhaustive search.