A method of constructing a hierarchical constellation for broadcast channels by optimizing power allocation to each data layer is proposed. With suitable error correction, symbol clusters can overlap, allowing different layers to have closer allocations than in previously proposed methods. In many scenarios, this method of construction leads to an improved data throughput per broadcast channel transmission. Optimal constellations can be easily constructed for arbitrary broadcast scenarios using publicly available geographic data, enabling robust planning for broadcast networks.

This paper presents a simple wireless medium access control (MAC) protocol that facilitates wireless nodes' cooperatively scheduling their use of the wireless medium. With this protocol, wireless nodes can pre-plan their active and inactive periods. Nodes can also change their schedule cooperatively as data generation and required data flows change. Such planning and adaptation can significantly save energy consumption by nodes going to sleep mode during inactive periods. Features of this protocol include synchronizing superframes of time slots by all nodes, distributed scheduling of packet transmissions, and each node maintaining its own neighborhood map. A node's neighborhood map records current schedules of medium access by neighboring nodes, namely, which nodes are scheduled to use which time slots for what purpose. The use of neighborhood maps prevents packet collision and also allows spatial re-use of the same time slots for spatially far apart nodes. We discuss the presented protocol's ability to avoid packet collision and the hidden node problem. We also analyze the protocol's performance in the case of asymmetric wireless channels.

This paper introduces a new paradigm for designing wireless network protocols to reduce nodes' duty cycles. The main feature of this paradigm is to allow nodes to schedule their transmission and reception so that nodes can go to their sleep modes during unscheduled times, facilitating a lower duty cycle. Nodes can schedule their use of a wireless medium without centralized coordination by locally exchanging control messages and maintaining information that summarizes the schedules of their neighboring nodes.

A class of algorithms for finding high-performing symbol labellings for QAM constellations is discussed. These algorithms use label swaps as a basic operation, ensuring feasibility of the solution space. We investigate the impact of greediness in local neighbor selection on the computational efficiency of hill climbing algorithms and the quality of their final solutions in comparison with simulated annealing techniques.

We present a computationally efficient method of optimizing the mapper (binary labelling of symbols) in the digital communication system to minimize the bit error probability. We note that high density of local minima makes this optimization problem difficult. We experiment with the simulated annealing (SA) method for this optimization problem as this method has a proven theoretical result of convergence to a global minimum. To obtain a high-quality labelling with reduced computational load, we propose a method that uses an approximated symbol error matrix (SEM), the matrix of probabilities of pairwise symbol error, for evaluating the objective function value for each labelling. Our experiments show that this approximation approach still finds relatively good solutions, which are comparable solutions attained by the SA that uses the exact SEM.

In most communications systems, the peak-to-average power ratio of a signal must be constrained due to limits in radio-frequency power amplifiers. Constraining the peak-to-average ratio limits the ability to optimize signal constellation shapes to minimize symbol-error probability. This paper presents the shapes of optimal one-dimensional constellations subject to peak-to-average power ratio constraints, and analyzes the effect of this constraint in terms of degraded symbol-error probability. We discuss the optimization challenges introduced by the additional constraint, and approaches to effectively solving for optimal constellations. The results have promising applications to energv-efficient communications systems.

It is known that coded system performance can be improved by simply generalizing the square-shaped quadrature amplitude modulation (QAM) constellation to a rectangular-shaped QAM. In the present letter a new method of approximating bitwise log-likelihood ratios is proposed and analyzed for efficient decoding in the system employing generalized QAMs. According to numerical results in additive white Gaussian noise (AWGN) channel, the proposed scheme provides a performance comparable to the Min-approximation especially at high $E_{s}/N_{0}$ , while achieving reduction in computational complexity.

There are many ways to label symbols in a constellation. We investigate the performance impact of the Gray code choice both in the case of uniformly-spaced symbol constellations and cropped Gaussian constellations, with the BICM (bit-interleaved coded modulation) mutual information as a performance measure. We exhaustively search and find all 131 Gray codes, including cyclic and acyclic Gray codes, each representing a class of codes resulting in the same performance, that can be used with a symmetric 16PAM. Our results show that Gray codes having a bit position with only a single transition tend to outper-form codes where all bit positions have multiple transitions. The ranking of Gray code performance was similar when using both square PAM and optimized cropped Gaussian PAM, with only minor differences in the rankings of Gray codes. This indicates that joint selection of the cropped Gaussian constellation and the Gray code is not significantly important in designing a system. These results in the present paper can be applied to 256-symbol QAM constellations with in-phase/quadrature symmetry.

This paper presents signal space constellations that minimize symbol-error probability in an uncoded communications system. We develop a modified projected gradient optimization method to solve for these constellations that scales efficiently, enabling the optimization of very large constellations. The optimized constellation shapes show significant improvements in symbol-error probability over a wide range of channel conditions compared with uniformly-spaced constellations. At high SNR, small deviations from uniform spacing can make substantial improvements in system performance. These results have promising applications to low-complexity systems with real-time data transmission requirements.

RATIONALE AND OBJECTIVES:To develop a 16-fold accelerated real-time, free-breathing cine cardiovascular magnetic resonance (CMR) pulse sequence with compressed sensing reconstruction and test whether it is capable of producing clinically acceptable summed visual scores (SVS) and accurate left ventricular ejection fraction (LVEF) in patients with a cardiac implantable electronic device (CIED).MATERIALS AND METHODS:A 16-fold accelerated real-time cine CMR pulse sequence was developed using gradient echo readout, Cartesian k-space sampling, and compressed sensing. We scanned 13 CIED patients (mean age = 59 years; 9/4 males/females) using clinical standard, breath-hold cine and real-time, free-breathing cine. Two clinical readers performed a visual assessment of image quality in four categories (conspicuity of endocardial wall at end diastole, temporal fidelity of wall motion, any artifact level on the heart, noise) using a five-point Likert scale (1: worst; 3: clinically acceptable; 5: best). SVS was calculated as the sum of 4 individual scores, where 12 was defined as clinical acceptable. The Wilcoxon signed-rank test was performed to compare SVS, and the Bland-Altman analysis was conducted to evaluate the agreement of LVEF.RESULTS:Median scan time was 3.7 times shorter for real-time (3.5 heartbeats per slice) than clinical standard (13 heartbeats per slice, excluding nonscanning time between successive breath-hold acquisitions). Median SVS was not significantly different between clinical standard (15.0) and real-time (14.5). The mean difference in LVEF was -2% (4.7% of mean), and the limits of agreement was 5.8% (13.5% of mean).CONCLUSION:This study demonstrates that the proposed real-time cine method produces clinically acceptable SVS and relatively accurate LVEF in CIED patients.

Compressed sensing (CS) is a promising method for accelerating cardiac perfusion MRI to achieve clinically acceptable image quality with high spatial resolution (1.6 × 1.6 × 8 mm3) and extensive myocardial coverage (6–8 slices per heartbeat). A major disadvantage of CS is its relatively lengthy processing time (~8 min per slice with 64 frames using a graphics processing unit), thereby making it impractical for clinical translation. The purpose of this study was to implement and test whether an image reconstruction pipeline including a neural network is capable of reconstructing 6.4‐fold accelerated, non‐Cartesian (radial) cardiac perfusion k‐space data at least 10 times faster than CS, without significant loss in image quality. We implemented a 3D (2D + time) U‐Net and trained it with 132 2D + time datasets (coil combined, zero filled as input; CS reconstruction as reference) with 64 time frames from 28 patients (8448 2D images in total). For testing, we used 56 2D + time coil‐combined, zero‐filled datasets (3584 2D images in total) from 12 different patients as input to our trained U‐Net, and compared the resulting images with CS reconstructed images using quantitative metrics of image quality and visual scores (conspicuity of wall enhancement, noise, artifacts; each score ranging from 1 (worst) to 5 (best), with 3 defined as clinically acceptable) evaluated by readers. Including pre‐ and post‐processing steps, compared with CS, U‐Net significantly reduced the reconstruction time by 14.4‐fold (32.1 ± 1.4 s for U‐Net versus 461.3 ± 16.9 s for CS, p < 0.001), while maintaining high data fidelity (structural similarity index = 0.914 ± 0.023, normalized root mean square error = 1.7 ± 0.3%, identical mean edge sharpness of 1.2 mm). The median visual summed score was not significantly different (p = 0.053) between CS (14; interquartile range (IQR) = 0.5) and U‐Net (12; IQR = 0.5). This study shows that the proposed pipeline with a U‐Net is capable of reconstructing 6.4‐fold accelerated, non‐Cartesian cardiac perfusion k‐space data 14.4 times faster than CS, without significant loss in data fidelity or image quality.

In modern digital communication systems, a high-order modulation and advanced channel coding are often jointly used to increase the spectral efficiency and coding gain. In this work, the authors investigate a computationally efficient method for evaluating the bitwise log-likelihood ratios of generalised M-ary pulse amplitude modulation (PAM) signals with the Min approximation. The proposed scheme is simple and can be applied to demodulate the M-ary PAM having an arbitrary symbol spacing and a bit stream mapping. The computational complexity and upper bounds of the approximation error are also provided for a better understanding of the proposed scheme.

In this paper, we present a method of constructing PAM constellations with non-uniform spacing by determining the symbol amplitudes based on warping the uniform distancing by applying the inverse error function. The construction method can adapt to symbol energy (SNR) constraints by adjusting one parameter. This parameter determines the degree of separation of the outermost pair of constellation symbols from the inner symbols and the degree of spacing uniformity. Optimization of this parameter is discussed for maximizing the equiprobable mutual information of the channel having the constellation. The equiprobable mutual information of the constellation constructed by the suggested method is compared against the uniform spacing and the Gaussian approximated spacing, which asymptotically approaches the AWGN capacity.

BACKGROUND:Eleven criteria correlating electrocardiogram (ECG) findings with reduced left ventricular ejection fraction (LVEF) have been previously published. These have not been compared head-to-head in a single study. We studied their value as a screening test to identify patients with reduced LVEF estimated by cardiac magnetic resonance (CMR) imaging. METHODS:ECGs and CMR from 548 patients (age 61 + 11 years, 79% male) with previous myocardial infarction (MI), from the DETERMINE and PRE-DETERMINE studies, were analyzed. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of each criterion for identifying patients with LVEF ≤ 30% and ≤ 40% were studied. A useful screening test should have high sensitivity and NPV. RESULTS:Mean LVEF was 40% (SD = 11%); 264 patients (48.2%) had LVEF ≤ 40%, and 96 patients (17.5%) had LVEF ≤ 30%. Six of 11 criteria were associated with a significant lower LVEF, but had poor sensitivity to identify LVEF ≤ 30% (range 2.1%-55.2%) or LVEF ≤ 40% (1.1%-51.1%); NPVs were good for LVEF ≤ 30% (range 82.8%-85.9%) but not for LVEF ≤ 40% (range 52.1%-60.6%). Goldberger's third criterion (RV4/SV4 < 1) and combinations of maximal QRS duration > 124 ms + either Goldberger's third criterion or Goldberger's first criterion (SV1 or SV2 + RV5 or RV6 ≥ 3.5 mV) had high specificity (95.4%-100%) for LVEF ≤ 40%, although seen in only 48 (8.8%) patients; predictive values were similar on subgroup analysis. CONCLUSIONS:None of the ECG criteria qualified as a good screening test. Three criteria had high specificity for LVEF ≤ 40%, although seen in < 9% of patients. Whether other ECG criteria can better identify LV dysfunction remains to be determined.

It is becoming increasingly difficult for game developers to manage the cost of developing a game, while meeting the high expectations of gamers. One way to balance the increasing gamer expectation and development stress is to build an active modding community around the game. There exist several examples of games with an extremely active and successful modding community, with the Minecraft game being one of the most notable ones. This paper reports on an empirical study of 1,114 popular and 1,114 unpopular Minecraft mods from the CurseForge mod distribution platform, one of the largest distribution platforms for Minecraft mods. We analyzed the relationship between 33 features across 5 dimensions of mod characteristics and the popularity of mods (i.e., mod category, mod documentation, environmental context of the mod, remuneration for the mod, and community contribution for the mod), to understand the characteristics of popular Minecraft mods. We firstly verify that the studied dimensions have significant explanatory power in distinguishing the popularity of the studied mods. Then we evaluated the contribution of each of the 33 features across the 5 dimensions. We observed that popular mods tend to have a high quality description and promote community contribution.

PURPOSE:To develop an accelerated wideband cardiac perfusion pulse sequence and test whether it can produce diagnostically acceptable image quality and whether it can be used to reliably quantify myocardial blood flow (MBF) in patients with a cardiac implantable electronic device (CIED). MATERIALS AND METHODS:A fivefold-accelerated wideband perfusion pulse sequence was developed using compressed sensing to sample one arterial input function plane and three myocardial perfusion (MP) planes per heartbeat in patients with a CIED with heart rates as high as 102 beats per minute. Resting perfusion scans were performed in 10 patients with a CIED and in 10 patients with no device as a control group. Two clinical readers compared the resulting images and retrospective images of the 10 patients with a CIED, which were obtained by using a previously described twofold-accelerated wideband perfusion pulse sequence with temporal generalized autocalibrating partially parallel acquisition. Summed visual score (SVS) was defined as the sum of conspicuity, artifact, and noise scores individually ranging from 1 (worst) to 5 (best). Resting MBF in the remote zones was quantified using Fermi deconvolution. RESULTS:Median SVS was significantly different (P < .05) between the prospective and retrospective CIED groups (13 vs nine) and between the nondevice group and the retrospective CIED group (13.5 vs nine); all median SVSs were nine or greater (clinically acceptable cut point). The median resting MBF in remote zones was not significantly different (P = .27) between patients with a CIED (1.1 mL/min/g; median left ventricular ejection fraction [LVEF], 52.5%) and patients with no device (1.3 mL/min/g; median LVEF, 64.0%). Mean MBF values were consistent with those (mean resting MBF range, 1.0-1.2 mL/min/g) reported by two prior state-of-the-art cardiac perfusion MRI studies. CONCLUSION:The proposed scan yielded diagnostically acceptable image quality and enabled reliable quantification of MBF with three MP planes per heartbeat in patients with a CIED with heart rates as high as 102 beats per minute. Supplemental material is available for this article. © RSNA, 2020.

The mutual information achieved by a pulse-amplitude modulated constellation depends strongly on the symbol labels. In general, these symbols are labeled based on a Gray code mapping, in which neighboring label bit-strings differ by only one bit value. For a 16-symbol constellation, there are numerous such Gray code mappings satisfying this property, each with distinct mutual information performance over SNR. In this paper, we present an investigation of the optimal labeling using cyclic Gray codes for symmetric 16-symbol one-dimensional constellations with uniform symbol probability and non-uniform spacing. These results can be extended to 256-symbol quadrature amplitude modulated constellations with in-phase/quadrature symmetry.

You have accessJournal of UrologyProstate Cancer: Detection & Screening II (MP20)1 Apr 2020MP20-07 CONCORDANCE BETWEEN MRI FUSION VS TRUS PROSTATE BIOPSY AND FINAL PATHOLOGY AT RADICAL PROSTATECTOMY: DATA FROM THE PURC Ruchika Talwar*, Katharine Michel, Aseem Malhotra, Bret Marlowe, Claudette Fonshell, John Danella, Serge Ginzberg, Bruce Jacobs, Thomas Lanchoney, Jay Raman, Eric Singer, Marc Smaldone, Jeffrey Tomaszewski, Edouard Trabulsi, Robert Uzzo, Daniel Lee, and Thomas Guzzo Ruchika Talwar*Ruchika Talwar* More articles by this author , Katharine MichelKatharine Michel More articles by this author , Aseem MalhotraAseem Malhotra More articles by this author , Bret MarloweBret Marlowe More articles by this author , Claudette FonshellClaudette Fonshell More articles by this author , John DanellaJohn Danella More articles by this author , Serge GinzbergSerge Ginzberg More articles by this author , Bruce JacobsBruce Jacobs More articles by this author , Thomas LanchoneyThomas Lanchoney More articles by this author , Jay RamanJay Raman More articles by this author , Eric SingerEric Singer More articles by this author , Marc SmaldoneMarc Smaldone More articles by this author , Jeffrey TomaszewskiJeffrey Tomaszewski More articles by this author , Edouard TrabulsiEdouard Trabulsi More articles by this author , Robert UzzoRobert Uzzo More articles by this author , Daniel LeeDaniel Lee More articles by this author , and Thomas GuzzoThomas Guzzo More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000853.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Studies suggest that MRI-fusion guided (MRI-fusion) biopsies are superior to the transrectal ultrasound guided (TRUS) technique. Herein, we present the Pennsylvania Urologic Regional Collaborative (PURC) experience with MRI fusion biopsy. We aimed to calculate concordance rates between TRUS prostate needle biopsy versus MRI fusion biopsy and final pathology at the time of radical prostatectomy within our cohort. METHODS: Within PURC, a prospective quality improvement collaborative of urology practices in Pennsylvania and New Jersey, we identified all men who underwent either a TRUS prostate needle biopsy, or an MRI fusion prostate needle biopsy, followed by radical prostatectomy for definitive treatment of prostate cancer from 2015 to 2018. We analyzed International Society of Urological Pathology Grade Group (GG) scoring and calculated the concordance and upgrading rates at the time of biopsy versus final pathology at radical prostatectomy. To assess for differences between our rates, we performed a test of equal proportions and Pearson's chi-squared test. We defined significance as p<0.05. RESULTS: We identified 1,437 patients who underwent TRUS (n =1247) or MRI Fusion (n=196) biopsies, followed by radical prostatectomy. Overall pathologic grading distribution at time of biopsy was: 35.8% (n=515) Grade Group (GG) 1, 28.5% (n=409) GG 2, 13.3% (n=191) GG 3, 11.5% (n=165) GG 4, and 10.9% (n=157) GG 5. Median number of cores at TRUS biopsy was 12 (IQR: 12,13). Median number of cores at MRI Fusion biopsy was 15 (IQR 13,18). Therefore, we inferred patients who underwent MRI Fusion biopsy also underwent standard TRUS biopsies at that time. Figure 1 illustrates differences in exact concordance rate between MRI fusion + TRUS and TRUS biopsies. The overall rate of upgrading on final pathology for MRI fusion +TRUS biopsies was 5.7% lower than for TRUS biopsies, but this was not statistically significant (35.2% vs 40.9%, 95% CI: 1.5-13.0%, p=0.06). CONCLUSIONS: MRI fusion plus TRUS biopsies demonstrated higher concordance rates with final pathology at the time of radical prostatectomy than TRUS prostate biopsies alone. Source of Funding: Data was provided with permission from the PURC, funded by participating urology practices and the Partnership for Patient Care, a quality improvement initiative supported by the Health Care Improvement Foundation, Independence Blue Cross, and southeastern PA hospitals and health systems. © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e309-e309 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ruchika Talwar* More articles by this author Katharine Michel More articles by this author Aseem Malhotra More articles by this author Bret Marlowe More articles by this author Claudette Fonshell More articles by this author John Danella More articles by this author Serge Ginzberg More articles by this author Bruce Jacobs More articles by this author Thomas Lanchoney More articles by this author Jay Raman More articles by this author Eric Singer More articles by this author Marc Smaldone More articles by this author Jeffrey Tomaszewski More articles by this author Edouard Trabulsi More articles by this author Robert Uzzo More articles by this author Daniel Lee More articles by this author Thomas Guzzo More articles by this author Expand All Advertisement PDF downloadLoading ...

This paper studies the channel capacity of the discrete-input continuous-output channel in which the input signal constellation has a rectangular-grid shape and the noise is additive white Gaussian. The channel capacity of such a system depends on the two parameters defining the shape of the constellation and the signal-to-noise ratio. We study the capacity as a function of these variables.

Prior work has shown that gamer loyalty is important for the sales of a developer’s future games. Therefore, it is important for game developers to increase the longevity of their games. However, game developers cannot always meet the growing and changing needs of the gaming community, due to the often already overloaded schedules of developers. So-called modders can potentially assist game developers with addressing gamers’ needs. Modders are enthusiasts who provide modifications or completely new content for a game. By supporting modders, game developers can meet the rapidly growing and varying needs of their gamer base. Modders have the potential to play a role in extending the life expectancy of a game, thereby saving game developers time and money, and leading to a better overall gaming experience for their gamer base. In this paper, we empirically study the metadata of 9,521 mods that were extracted from the Nexus Mods distribution platform. The Nexus Mods distribution platform is one of the largest mod distribution platforms for PC games at the time of our study. The goal of our paper is to provide useful insights about mods on the Nexus Mods distribution platform from a quantitative perspective, and to provide researchers a solid foundation to further explore game mods. To better understand the potential of mods to extend the longevity of a game we study their characteristics, and we study their release schedules and post-release support (in terms of bug reports) as a proxy for the willingness of the modding community to contribute to a game. We find that providing official support for mods can be beneficial for the perceived quality of the mods of a game: games for which a modding tool is provided by the original game developer have a higher median endorsement ratio than mods for games that do not have such a tool. In addition, mod users are willing to submit bug reports for a mod. However, they often fail to do this in a systematic manner using the bug reporting tool of the Nexus Mods platform, resulting in low-quality bug reports which are difficult to resolve. Our findings give the first insights into the characteristics, release schedule and post-release support of game mods. Our findings show that some games have a very active modding community, which contributes to those games through mods. Based on our findings, we recommend that game developers who desire an active modding community for their own games provide the modding community with an officially-supported modding tool. In addition, we recommend that mod distribution platforms, such as Nexus Mods, improve their bug reporting system to receive higher quality bug reports.