Impact of Beam Misalignment on Hybrid Beamforming NOMA for mmWave Communications

This paper analyzes the effect of beam misalignment on rate performance in downlink of hybrid beamforming-based non-orthogonal multiple access (HB-NOMA) systems. First an HB-NOMA framework is designed in multiuser millimeter wave (mmWave) communications. A sum-rate maximization problem is formulated for HB-NOMA, and an algorithm is introduced to design digital and analog precoders and efficient power allocation. Then, regarding perfectly aligned line-of-sight (LoS) channels, a lower bound for the achievable rate is derived. Next, when the users experience misaligned LoS or non-LoS (NLoS) channels, the impact of beam misalignment is evaluated. To this end, a misalignment factor is modeled and each misaligned effective channel is described in terms of the perfectly aligned effective channel parameters and the misalignment factor. Further, a lower bound for the achievable rate is extracted. We then derive an upper bound for the rate gap expression between the aligned and misaligned HB-NOMA systems. The analyses reveal that a large misalignment can remarkably degrade the rate. Extensive numerical simulations are conducted to verify the findings

Non-Orthogonal Multiple Access Based on Hybrid Beamforming for mmWave Systems

This paper aims to study the utilization of non-orthogonal multiple access (NOMA) in hybrid beamforming (HB) multiuser systems, called HB-NOMA, to serve a large number of mobile users. First, a sum-rate expression for the HB-NOMA problem is formulated. Second, an effective algorithm is proposed to maximize the sum-rate. Then, a lower bound is derived under two cases: i) the angle between the effective channel vectors of the MU with the highest channel gain and other MUs located inside a cluster is zero (or close to it) which is denoted by perfect correlation, and ii) this angle is non-zero, which we denote by imperfect correlation. For the second case, the relationship between the effective channels of two HB-NOMA users is modeled. The lower bound for the first case indicates that only the presence of inter-cluster interference and the use of an analog precoder negatively impact the sum-rate. However, in the case of imperfect correlation, which is more realistic, an inefficient MU cluster, can cause severe intra-cluster interference in the network. To verify our findings, numerical simulations have been conducted

Lens-Based Millimeter Wave Reconfigurable Antenna NOMA

This paper proposes a new multiple access technique based on the millimeter wave lens-based reconfigurable antenna systems. In particular, to support a large number of groups of users with different angles of departures (AoDs), we integrate recently proposed reconfigurable antenna multiple access (RAMA) into non-orthogonal multiple access (NOMA). The proposed technique, named reconfigurable antenna NOMA (RA-NOMA), divides the users with respect to their AoDs and channel gains. Users with different AoDs and comparable channel gains are served via RAMA while users with the same AoDs but different channel gains are served via NOMA. This technique results in the independence of the number of radio frequency chains from the number of NOMA groups. Further, we derive the feasibility conditions and show that the power allocation for RA-NOMA is a convex problem. We then derive the maximum achievable sum-rate of RA-NOMA. Simulation results show that RA-NOMA outperforms conventional orthogonal multiple access (OMA) as well as the combination of RAMA with the OMA techniques

Reconfigurable Antennas in mmWave MIMO Systems

The key obstacle to achieving the full potential of the millimeter wave (mmWave) band has been the poor propagation characteristics of wireless signals in this band. One approach to overcome this issue is to use antennas that can support higher gains while providing beam adaptability and diversity, i.e., reconfigurable antennas. In this article, we present a new architecture for mmWave multiple-input multiple-output (MIMO) communications that uses a new class of reconfigurable antennas. More specifically, the proposed lens-based antennas can support multiple radiation patterns while using a single radio frequency chain. Moreover, by using a beam selection network, each antenna beam can be steered in the desired direction. Further, using the proposed reconfigurable antenna in a MIMO architecture, we propose a new signal processing algorithm that uses the additional degrees of freedom provided by the antennas to overcome propagation issues at mmWave frequencies. Our simulation results show that the proposed reconfigurable antenna MIMO architecture significantly enhances the performance of mmWave communication systems

NAČIN PROCJENE I KLASIFIKACIJE KAMENOLOMA OBLIKOVANOGA KAMENA S NAGLASKOM NA SIGURNOSNE PARAMETRE

Building, dimensional and decorative stones from mining and industry are among the significant resources of Iran. Following China and Italy, Iran is in third place of world production, but only has a minor contribution in international trade. One main reason of this problem is negligence regarding the introduction of dependable mines to foreign customers. On the other hand, the frequency of fatal and non-fatal accidents in these mines implies the necessity of more attention to safety parameters. The first stage to attain this aim is identifying the major factors on safety of these mines and ranking the major mines considering these indices. In this paper, a comprehensive model for ranking of mines in the sense of all imposing attributes with an emphasis on safety parameters is presented. In order to validate the model, 19 active mines of the Pyrtak Company in Lorestan province have been used. In this paper, after determining all the parameters of safety in decorative stone mines and weighting these attributes, using AHP-TOPSIS and fuzzy environment, mines have been ranked. After a systematic evaluation of the decorative stone mines, the most appropriate mine is selected.Građevinski, oblikovani i ukrasni kamen te kamenolomi iz kojih se pridobivaju pripadaju važnoj gospodarskoj grani u Iranu. Danas je ta zemlja, nakon Kine i Italije, na trećemu mjestu po pridobivanju takvih sirovina u svijetu. Međutim, u svjetskoj trgovini takvim kamenjem sudjeluje sa znatno manjim udjelom. Jedan je od razloga nedostatak predstavljanja aktivnosti vezanih uz tu gospodarsku granu inozemnim kupcima. Nadalje, broj nesreća, s ozbiljnim i manjim posljedicama, pokazao je kako se njihovu sprječavanju mora posvetiti više pozornosti. Prvi korak u tome je prepoznavanje svih onih faktora koji na to mogu utjecati te rangiranje najvećih kamenoloma po sigurnosnim kriterijima. Stoga je ovdje prikazan opsežan model za rangiranje kamenoloma, u kojemu su izdvojene sve nužne varijable važne za sigurnost rada. U cilju provjere modela analizirano je 19 kamenoloma koje vodi tvrtka Pyrtak u provinciji Lorestan. Nakon određivanja uvjeta u kamenolomima ukrasnoga kamena i određivanja njihova utjecaja primijenjena je metoda AHP-TOPSIS koja se temelji na neizravnoj logici. Kamenolomi su rangirani prema rezultatima te je izdvojen onaj s najprimjerenijim načinom rudarenja

Reinforcement Learning for Self Organization and Power Control of Two-Tier Heterogeneous Networks

Self-organizing networks (SONs) can help manage the severe interference in dense heterogeneous networks (HetNets). Given their need to automatically configure power and other settings, machine learning is a promising tool for data-driven decision making in SONs. In this paper, a HetNet is modeled as a dense two-tier network with conventional macrocells overlaid with denser small cells (e.g. femto or pico cells). First, a distributed framework based on multi-agent Markov decision process is proposed that models the power optimization problem in the network. Second, we present a systematic approach for designing a reward function based on the optimization problem. Third, we introduce Q-learning based distributed power allocation algorithm (Q-DPA) as a self-organizing mechanism that enables ongoing transmit power adaptation as new small cells are added to the network. Further, the sample complexity of the Q-DPA algorithm to achieve ϵ-optimality with high probability is provided. We demonstrate, at density of several thousands femtocells per km2, the required quality of service of a macrocell user can be maintained via the proper selection of independent or cooperative learning and appropriate Markov state models

Paradigmatic Typology of Economic Schools and the Role of Transaction Cost in the Paradigm Shift

The paradigm includes a set of values, beliefs and perceptions of reality with theories based on them, which uses a distinctive methodology to achieve research goals. The dominant paradigms in the humanities are Positivism, Interpretation, Criticism, Complexity and Postmodernism. This research seeks to understand the meta-theoretical and paradigmatic typology of economic schools by using the documentary and content analysis.The results show that Neoclassical is positivist. Austrian tendencies are in the region of complexity, but the use of hermeneutics puts New Austrians closer to the interpretive paradigm, while the older part tends to be a Positivism. The existence of variable structures in the Post-Keynesian and Evolutionary indicates the influence of the Complexity. OIE is dominated by the Criticism because of its emphasis on domination and dialectics.NIE uses the principles of Neoclassical and OIE as opposing currents. The elimination of this inconsistency has been due to the invention of Transaction Costs, which provides the basis for a paradigm shift from Positivism and Criticism to Complexity. The transaction cost is the unit of analysis and the connection of institutions to economic performance, the use of which will lead to objectivity and generalization

A New Reconfigurable Antenna MIMO Architecture for mmWave Communication

The large spectrum available in the millimeter- Wave (mmWave) band has emerged as a promising solution for meeting the huge capacity requirements of the 5th generation (5G) wireless networks. However, to fully harness the potential of mmWave communications, obstacles such as severe path loss, channel sparsity and hardware complexity should be overcome. In this paper, we introduce a generalized reconfigurable antenna multiple-input multiple-output (MIMO) architecture that takes advantage of lens-based reconfigurable antennas. The considered antennas can support multiple radiation patterns simultaneously by using a single RF chain. The degrees of freedom provided by the reconfigurable antennas are used to, first, combat channel sparsity in MIMO mmWave systems. Further, to suppress high path loss and shadowing at mmWave frequencies, we use a rate-one space-time block code. Our analysis and simulations show that the proposed reconfigurable MIMO architecture achieves full-diversity gain by using linear receivers and without requiring channel state information at the transmitter. Moreover, simulations show that the proposed architecture outperforms traditional MIMO transmission schemes in mmWave channel settings

Emergency Department Quality Dashboard; a Systematic Review of Performance Indicators, Functionalities, and Challenges

Introduction: Effective information management in the emergency department (ED) can improve the control and management of ED processes. Dashboards, known as data management tools, efficiently provide information and contribute greatly to control and management of ED. This study aimed to identify performance indicators and quality dashboard functionalities, and analyze the challenges associated with dashboard implementation in the ED. Methods: This systematic review began with a search in four databases (Web of Science, PubMed, Embase, and Scopus) from 2000 to May 30, 2020, when the final search for papers was conducted. The data were collected using a data extraction form and the contents of the extracted papers were analyzed through ED performance indicators, dashboard functionalities, and implementation challenges. Results: Performance indicators reported in the reviewed papers were classified as the quality of care, patient flow, timeliness, costs, and resources. The main dashboard functionalities noted in the papers included reporting, customization, alert creation, resource management, and real-time information display. The dashboard implementation challenges included data sources, data quality, integration with other systems, adaptability of dashboard functionalities to user needs, and selection of appropriate performance indicators. Conclusions: Quality dashboards facilitate processes, communication, and situation awareness in the ED; hence, they can improve care provision in this department. To enhance the effectiveness and efficiency of ED dashboards, officials should set performance indicators and consider the conformity of dashboard functionalities with user needs. They should also integrate dashboards with other relevant systems at the departmental and hospital levels