Evaluation of fourth generation air-interfaces for mobile communications

Abstract Development of the Fourth Generation of mobile communication systems, or 4G, has already begun in various organizations and research institutions worldwide. There is currently no single conclusive definition for 4G systems, and the process of 4G standardization will only begin after the World Radiocommunication Conference in 2007. The purpose of this report is to provide an objective definition of 4G systems based on user requirements, and to use this definition to determine an appropriate 4G access network architecture. By examining the current trends in user requirements, and the methodologies proposed by different researchers, an objective definition of 4G systems was developed. The definition states that the purpose of 4G systems is to provide users with the capacity to access any service at any time at a reasonable cost and at the required levels of quality. There are two developmental methodologies which are currently being considered to achieve this objective: first the evolution and convergence of existing systems, including cellular, IT and broadcasting communication systems, and second, the development of a new 4G access network capable of providing users with access to advanced services. The primary specification for this new access network is that it must provide a throughput of 1 Mbps for mobile users and 1 Gbps for users that are stationary. Other requirements include high spectral efficiency and high capacity and coverage. The primary focus of this report is the examination of the second of the above methodologies by evaluating the performance of candidate 4G air-interface architectures so that a recommendation could be made as to which of the architectures is the preferred choice as the core component in a new 4G access network. Orthogonal Frequency Division Multiplexing (OFDM) modulation is a high performance modulation technique capable of achieving high levels of spectral efficiency and is widely accepted as the technique most capable of meeting 4G access network requirements. There are two primary access network architectures that make use of OFDM modulation and could form the core components of a 4G air-interface, the physical component of a 4G access network. To determine which architecture is the appropriate choice for 4G systems, a series of simulations were run using realistic models of a wireless environment. The results of those simulations were analyzed, and it was determined that, due to the absence of multiple access interference found in MC-CDMA, OFDMA systems better met the defined requirements for a 4G air-interface. The use of additional techniques such as radio resource management, multi-antennae technologies and software defined radios are cited as potential methods for improving both OFDMA and MC-CDMA performance

An architecture for converging reconfigurable radio systems

Since mobile telecommunication systems were rst introduced in the early 1980s they have become a pervasive part of modern life, with an estimated 85% of the global population believed to be in possession of a mobile communications device. To address the ever-increasing demand for fast ubiquitous provision of multimedia and data services, new Radio Access Technologies (RATs) capable of meeting those demands are constantly being developed and standardised. Currently the fourth generation of RATs is being deployed by network operators around the world, with standards bodies already working to develop and standardise even more advanced RATs. The introduction of any new, and often upgraded, RATs almost always requires network operators to purchase new hardware systems capable of supporting the new RATs, which must then be integrated with the plethora of RATs already present in the network operator's heterogeneous Radio Access Network (RAN). This process is costly and poses risks for network operators, as they must rst invest signi cant amounts of capital on new network hardware and then they have to convince their subscribers to purchase new mobile devices which are capable of supporting the new RAT. Recon gurable Radio Systems (RRSs) are a relatively new approach to developing, implementing and managing RATs within a RAN. A RRS di ers from a traditional radio system, in that each RAT is de ned in software which can be reused across multiple generic hardware platforms. Many RRSs also provide the functionality to manage and control the dynamic implementation of di erent RATs in network elements throughout a RAN. Although RRSs are the subject of numerous research e orts, there is currently no unifying approach or set of requirements for an RRS architecture or framework. In- stead various researchers focus their e orts on speci c topics relating to RRS, such as the recon gurable management system, or how RATs are modelled and implemented in software. This lack of formal standardisation or approach to developing RRSs represents a hindrance to the widespread adoption of RRSs

Globular Cluster Systems in Nearby Dwarf Galaxies: I. HST/ACS Observations and Dynamical Properties of Globular Clusters at Low Environmental Density

We investigate the old globular cluster (GC) population of 68 faint (Mv>-16 mag) dwarf galaxies located in the halo regions of nearby (<12 Mpc) loose galaxy groups and in the field environment based on archival HST/ACS images in F606W and F814W filters. The combined color distribution of 175 GC candidates peaks at (V-I)=0.96 +/- 0.07 mag and the GC luminosity function turnover for the entire sample is found at Mv,to = -7.6 +/- 0.11 mag, similar to the old metal-poor LMC GC population. Our data reveal a tentative trend of Mv,to becoming fainter from late-type to early-type galaxies. The luminosity and color distributions of GCs in dIrrs shows a lack of faint blue GCs. Our analysis reveals that this might reflect a relatively younger GC system than typically found in luminous early-type galaxies. If verified by spectroscopy this would suggest a later formation epoch of the first metal-poor star clusters in dwarf galaxies. We find several bright (massive) GCs which reside in the nuclear regions of their host galaxies. These nuclear clusters have similar luminosities and structural parameters as the peculiar Galactic clusters suspected of being the remnant nuclei of accreted dwarf galaxies, such as M54 and wCen. Except for these nuclear clusters, the distribution of GCs in dIrrs in the half-light radius vs. cluster mass plane is very similar to that of Galactic young halo clusters, which suggests comparable formation and dynamical evolution histories. A comparison with theoretical models of cluster disruption indicates that GCs in low-mass galaxies evolve dynamically as self-gravitating systems in a benign tidal environment.Comment: MNRAS in press, 20 pages, 9 figures, 3 Tables (Full version of Figure 9 available upon request

Crowdsourcing hypothesis tests: Making transparent how design choices shape research results

To what extent are research results influenced by subjective decisions that scientists make as they design studies? Fifteen research teams independently designed studies to answer fiveoriginal research questions related to moral judgments, negotiations, and implicit cognition. Participants from two separate large samples (total N > 15,000) were then randomly assigned to complete one version of each study. Effect sizes varied dramatically across different sets of materials designed to test the same hypothesis: materials from different teams renderedstatistically significant effects in opposite directions for four out of five hypotheses, with the narrowest range in estimates being d = -0.37 to +0.26. Meta-analysis and a Bayesian perspective on the results revealed overall support for two hypotheses, and a lack of support for three hypotheses. Overall, practically none of the variability in effect sizes was attributable to the skill of the research team in designing materials, while considerable variability was attributable to the hypothesis being tested. In a forecasting survey, predictions of other scientists were significantly correlated with study results, both across and within hypotheses. Crowdsourced testing of research hypotheses helps reveal the true consistency of empirical support for a scientific claim.</div

Correction to: A nonsynonymous mutation in PLCG2 reduces the risk of Alzheimer's disease, dementia with Lewy bodies and frontotemporal dementia, and increases the likelihood of longevity.

The IPDGC (The International Parkinson Disease Genomics Consortium) and EADB (Alzheimer Disease European DNA biobank) are listed correctly as an author to the article, however, they were incorrectly listed more than once

Correction to: A nonsynonymous mutation in PLCG2 reduces the risk of Alzheimer’s disease, dementia with Lewy bodies and frontotemporal dementia, and increases the likelihood of longevity

The IPDGC (The International Parkinson Disease Genomics Consortium) and EADB (Alzheimer Disease European DNA biobank) are listed correctly as an author to the article, however, they were incorrectly listed more than once

Correction to: A nonsynonymous mutation in PLCG2 reduces the risk of Alzheimer’s disease, dementia with Lewy bodies and frontotemporal dementia, and increases the likelihood of longevity

The IPDGC (The International Parkinson Disease Genomics Consortium) and EADB (Alzheimer Disease European DNA biobank) are listed correctly as an author to the article, however, they were incorrectly listed more than once

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Open-source image analysis tool for the identification and quantification of cortical interruptions and bone erosions in high-resolution peripheral quantitative computed tomography images of patients with rheumatoid arthritis

Identification of bone erosions and quantification of erosion volume is important for rheumatoid arthritis diagnosis, and can add important information to evaluate disease progression and treatment effects. High-resolution peripheral quantitative computed tomography (HR-pQCT) is well suited for this purpose, however analysis methods are not widely available. The purpose of this study was to develop an open-source software tool for the identification and quantification of bone erosions using images acquired by HR-pQCT. The collection of modules, Bone Analysis Modules (BAM) - Erosion, implements previously published erosion analysis techniques as modules in 3D Slicer, an open-source image processing and visualization tool. BAM includes a module to automatically identify cortical interruptions, from which erosions are manually selected, and a hybrid module that combines morphological and level set operations to quantify the volume of bone erosions. HR-pQCT images of the second and third metacarpophalangeal (MCP) joints were acquired in patients with RA (XtremeCT, n = 14, XtremeCTII, n = 22). The number of cortical interruptions detected by BAM-Erosion agreed strongly with the previously published cortical interruption detection algorithm for both XtremeCT (r 2 = 0.85) and XtremeCTII (r 2 = 0.87). Erosion volume assessment by BAM-Erosion agreed strongly (r 2 = 0.95) with the Medical Image Analysis Framework. BAM-Erosion provides an open-source erosion analysis tool that produces comparable results to previously published algorithms, with improved options for visualization. The strength of the tool is that it implements multiple image processing algorithms for erosion analysis on a single, widely available, open-source platform that can accommodate future updates

Open-source image analysis tool for the identification and quantification of cortical interruptions and bone erosions in high-resolution peripheral quantitative computed tomography images of patients with rheumatoid arthritis

Identification of bone erosions and quantification of erosion volume is important for rheumatoid arthritis diagnosis, and can add important information to evaluate disease progression and treatment effects. High-resolution peripheral quantitative computed tomography (HR-pQCT) is well suited for this purpose, however analysis methods are not widely available. The purpose of this study was to develop an open-source software tool for the identification and quantification of bone erosions using images acquired by HR-pQCT. The collection of modules, Bone Analysis Modules (BAM) - Erosion, implements previously published erosion analysis techniques as modules in 3D Slicer, an open-source image processing and visualization tool. BAM includes a module to automatically identify cortical interruptions, from which erosions are manually selected, and a hybrid module that combines morphological and level set operations to quantify the volume of bone erosions. HR-pQCT images of the second and third metacarpophalangeal (MCP) joints were acquired in patients with RA (XtremeCT, n = 14, XtremeCTII, n = 22). The number of cortical interruptions detected by BAM-Erosion agreed strongly with the previously published cortical interruption detection algorithm for both XtremeCT (r2 = 0.85) and XtremeCTII (r2 = 0.87). Erosion volume assessment by BAM-Erosion agreed strongly (r2 = 0.95) with the Medical Image Analysis Framework. BAM-Erosion provides an open-source erosion analysis tool that produces comparable results to previously published algorithms, with improved options for visualization. The strength of the tool is that it implements multiple image processing algorithms for erosion analysis on a single, widely available, open-source platform that can accommodate future updates