A general theoretical framework is presented for analyzing information transmission over Gaussian channels with memoryless transceiver distortion, which encompasses various nonlinear distortion ...models including transmit-side clipping, receive-side analog-to-digital conversion, and others. The framework is based on the so-called generalized mutual information (GMI), and the analysis in particular benefits from the setup of Gaussian codebook ensemble and nearest-neighbor decoding, for which it is established that the GMI takes a general form analogous to the channel capacity of undistorted Gaussian channels, with a reduced "effective" signal-to-noise ratio (SNR) that depends on the nominal SNR and the distortion model. When applied to specific distortion models, an array of results of engineering relevance is obtained. For channels with transmit-side distortion only, it is shown that a conventional approach, which treats the distorted signal as the sum of the original signal part and a uncorrelated distortion part, achieves the GMI. For channels with output quantization, closed-form expressions are obtained for the effective SNR and the GMI, and related optimization problems are formulated and solved for quantizer design. Finally, super-Nyquist sampling is analyzed within the general framework, and it is shown that sampling beyond the Nyquist rate increases the GMI for all SNR values. For example, with binary symmetric output quantization, information rates exceeding one bit per channel use are achievable by sampling the output at four times the Nyquist rate.
Mixed-ADC Massive MIMO Liang, Ning; Zhang, Wenyi
IEEE journal on selected areas in communications,
04/2016, Letnik:
34, Številka:
4
Journal Article
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Motivated by the demand for energy-efficient communication solutions in the next generation cellular network, a mixed-ADC architecture for massive multiple-input-multiple-output (MIMO) systems is ...proposed, which differs from previous works in that herein one-bit analog-to-digital converters (ADCs) partially replace the conventionally assumed high-resolution ADCs. The information-theoretic tool of generalized mutual information (GMI) is exploited to analyze the achievable data rates of the proposed system architecture and an array of analytical results of engineering interest are obtained. For fixed single-input-multiple-output (SIMO) channels, a closed-form expression of the GMI is derived, based on which the linear combiner is optimized. The analysis is then extended to ergodic fading channels, for which tight lower and upper bounds of the GMI are obtained. Impacts of dithering and imperfect channel state information (CSI) are also investigated, and it is shown that dithering can remarkably improve the system performance while imperfect CSI only introduces a marginal rate loss. Finally, the analytical framework is applied to the multiuser access scenario. Numerical results demonstrate that the mixed-ADC architecture with a relatively small number of high-resolution ADCs is able to achieve a large fraction of the channel capacity of conventional architecture, while reduce the energy consumption considerably even compared with antenna selection, for both single-user and multiuser scenarios.
Since the 21st century, people’s demand for new energy has become increasingly high, and new energy vehicles have become a promising emerging industry. The purpose of this study was to find out why ...Huawei only collaborates with car companies but does not manufacture its own cars. This research applied data and information from Huawei’s research and development investment, revenue data, and sales in the new energy vehicle market for analysis. The analysis’s results showed that one of the main reasons was that Huawei’s business focus is not on car manufacturing, and the article suggested that Huawei should focus on technology development and upgrading. The second reason was the fierce, cutthroat competition in the market, and this paper suggested that Huawei strengthen cooperation with automobile enterprises. The third reason was that the cost of making cars alone is too high, and Huawei is advised to wait for a good time before making cars. This article filled some of the research gaps on Huawei and can provide relevant industry practitioners with some reference for analysing the new energy vehicle market and enterprise development strategies.
This paper discusses several events that have shaped the lives and communities of the Jingpo people in Southwest China since the 21st century. While a single event has its own logics as a result of ...subjective choices and social forces, but being placed side by side with life time events and social history, it can appear anonymous and irrelevant. Anonymity refers to the unspeakable pain, inexplicable sentimentality and nostalgia, not in words, but in tones and eyes, and in the atmosphere and temperament of the entire community. Anonymity is manifested as a new disease that is incurable and has not yet been named. Disconnection stems from the breakdown of the relationship between man and land, from the increasingly dysfunctional marriage system and dissipation of the moral world. The old gods left but the new ones have not yet arrived. People are dominated by desires but unable to fulfil them. This "nothingness" brings confusion and decadence of the people, and anxiety of the community. The handling of "nothing
The aim of this paper is to investigate the recently developed mixed-analog-to-digital converter (ADC) architecture for frequency-selective channels. Multi-carrier techniques, such as orthogonal ...frequency division multiplexing, are employed to handle inter-symbol interference. A frequency-domain equalizer is designed for mitigating the inter-carrier interference introduced by the nonlinearity of one-bit quantization. For static single-input-multiple-output (SIMO) channels, a closed-form expression of the generalized mutual information (GMI) is derived, and based on which the linear frequency-domain equalizer is optimized. The analysis is then extended to ergodic time-varying SIMO channels with estimated channel state information, where numerically tight lower and upper bounds of the GMI are derived. The analytical framework is naturally applicable to the multi-user scenario, for both static and time-varying channels. Extensive numerical studies reveal that the mixed-ADC architecture with a small proportion of high-resolution ADCs does achieve a dominant portion of the achievable rate of ideal conventional architecture, and that it remarkably improves the performance as compared with one-bit massive multiple-input-multiple-output.
We study the information rates of unipolar orthogonal frequency division multiplexing (OFDM) in discrete-time optical intensity channels (OIC) with Gaussian noise under average optical power ...constraint. Several single-, double-, and multi-component unipolar OFDM schemes are considered under the assumption that independent and identically distributed. Gaussian or complex Gaussian codebook ensemble and nearest neighbor decoding (minimum Euclidean distance decoding) are used. We obtain an array of information rate result. These results validate existing signal-to-noise-and-distortion-ratio-based rate analysis, establish the equivalence of information rates of certain schemes, and demonstrate the evident benefits of using component-multiplexing at high signal-to-noise-ratio (SNR). For double- and multi-component schemes, the component power allocation strategies that maximize the information rates are investigated. In particular, by utilizing a power allocation strategy, we prove that several multi-component schemes approach the high SNR capacity of the discrete-time Gaussian OIC under average power constraint to within 0.07 bits.
Abstract
Objectives
To provide an overview of the three major deadly coronaviruses and identify areas for improvement of future preparedness plans, as well as provide a critical assessment of the ...risk factors and actionable items for stopping their spread, utilizing lessons learned from the first two deadly coronavirus outbreaks, as well as initial reports from the current novel coronavirus (COVID-19) epidemic in Wuhan, China.
Methods
Utilizing the Centers for Disease Control and Prevention (CDC, USA) website, and a comprehensive review of PubMed literature, we obtained information regarding clinical signs and symptoms, treatment and diagnosis, transmission methods, protection methods and risk factors for Middle East respiratory syndrome (MERS), severe acute respiratory syndrome (SARS) and COVID-19. Comparisons between the viruses were made.
Results
Inadequate risk assessment regarding the urgency of the situation, and limited reporting on the virus within China has, in part, led to the rapid spread of COVID-19 throughout mainland China and into proximal and distant countries. Compared with SARS and MERS, COVID-19 has spread more rapidly, due in part to increased globalization and the focus of the epidemic. Wuhan, China is a large hub connecting the North, South, East and West of China via railways and a major international airport. The availability of connecting flights, the timing of the outbreak during the Chinese (Lunar) New Year, and the massive rail transit hub located in Wuhan has enabled the virus to perforate throughout China, and eventually, globally.
Conclusions
We conclude that we did not learn from the two prior epidemics of coronavirus and were ill-prepared to deal with the challenges the COVID-19 epidemic has posed. Future research should attempt to address the uses and implications of internet of things (IoT) technologies for mapping the spread of infection.
For two-tier networks consisting of macrocells and femtocells, the channel access mechanism can be configured to be open access, closed access, or hybrid access. Hybrid access arises as a compromise ...between open and closed access mechanisms, in which a fraction of available spectrum resource is shared to nonsubscribers while the remaining reserved for subscribers. This paper focuses on a hybrid access mechanism for multi-channel femtocells which employ orthogonal spectrum access schemes. Considering a randomized channel assignment strategy, we analyze the performance in the downlink. Using stochastic geometry as technical tools, we model the distribution of femtocells as Poisson point process or Neyman-Scott cluster process and derive the distributions of signal-to-interference-plus-noise ratios, and mean achievable rates, of both nonsubscribers and subscribers. The established expressions are amenable to numerical evaluation, and shed key insights into the performance tradeoff between subscribers and nonsubscribers. The analytical results are corroborated by numerical simulations.
The capacity of wireless networks is fundamentally limited by interference. However, little research has focused on the interference correlation, which may greatly increase the local delay (namely ...the number of time slots required for a node to successfully transmit a packet). This paper focuses on the question whether increasing randomness in the MAC, specifically frequency-hopping multiple access (FHMA) and ALOHA, helps to reduce the effect of interference correlation. We derive closed-form results for the mean and variance of the local delay for the two MAC protocols and evaluate the optimal parameters that minimize the mean local delay. Based on the optimal parameters, we identify two operating regimes, the correlation-limited regime and the bandwidth-limited regime. Our results reveal that while the mean local delays for FHMA with N sub-bands and for ALOHA with transmit probability p essentially coincide when p=1/N, a fundamental discrepancy exists between their variances. We also discuss implications from the analysis, including an interesting mean delay-jitter tradeoff, and convenient bounds on the tail probability of the local delay, which shed useful insights into system design.
In this paper, the degradation of azo dye Acid Orange 7 (AO7) by three common peroxides (persulfate (PS), peroxymonosulfate (PMS) or hydrogen peroxide (H
2O
2)) under various activation conditions, ...i.e., heat (25–80
°C), UV light (254
nm), or anions (SO
4
2−, NO
3
−, CO
3
2−, HCO
3
−, HPO
4
2−, and Cl
−), was investigated. The order of AO7 degradation efficiencies by heat activation is PS
≫
PMS
>
H
2O
2. PS oxidation activated by heat (>50
°C) is an effective degradation technology, while PMS and H
2O
2 are hardly activated. When assisted by UV, peroxides could all be activated and degrade AO7 quickly. The order is PS
>
H
2O
2
>
PMS. We activated peroxides, for the first time, by using some anions and compared the subsequently degradation efficiencies of AO7. It was found that PMS could be activated by some anions, but PS and H
2O
2 cannot. The activation efficiencies of PMS by SO
4
2− and NO
3
− are negligible, whereas remarkable by HCO
3
−, HPO
4
2−, Cl
− and CO
3
2−. For HCO
3
−, HPO
4
2− and Cl
−, the activation efficiencies become higher with the increase of anion concentration. For CO
3
2−, however, the activation efficiency is higher at lower concentration.
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