scholarly journals Secrecy Capacity of Time Reversal Beamforming for Multi-User MIMO System under Spatial Correlation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Bingyan He ◽  
Tao Sun ◽  
Chuanmu Li ◽  
Xingwang Huang
Keyword(s):  
Spatial Correlation ◽  
Time Reversal ◽  
Performance Metrics ◽  
Channel Model ◽  
Mimo System ◽  
Cost Effective ◽  
Significant Loss ◽  
Secrecy Capacity ◽  
Sum Rate ◽  
The Impact

In this paper, for strengthening the security of wireless transmission system, the time reversal (TR) beamforming method is proposed for the downlink of multi-user MIMO system with multiple users who potentially act as eavesdroppers. We develop a multi-input, single-output, multi-eavesdropper (MISOME) wiretap channel model in which Rayleigh fading and spatial correlation are taken into account. Using the proposed model, we further analyze the confidentiality provided by TR beamforming and we use achievable secrecy rates as our performance metrics. In particular, we derive novel closed-formed expressions for the average secrecy-SINR and the mean secrecy sum-rate in order to characterize the influences of propagation conditions on network secrecy metrics. These expressions provide deeper insights into the impact of network interference on communication confidentiality. We find that TR beamforming can deliver the maximum secrecy capacity potential in uncorrelated Rayleigh channels and achieve perfect confidential communication without any extra secrecy cost. On the other hand, even weak inter-user correlation may cause a significant loss of achievable secrecy sum-rate and therefore result in high secrecy cost. But benefiting more from larger signal bandwidth and rich-scattering environment, the TR beamforming technique is still an attractive and cost-effective solution for low-power indoor applications.

scholarly journals On the Performance of the Time Reversal SM-MIMO-UWB System on Correlated Channels

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Hieu Nguyen ◽  
Van Duc Nguyen ◽  
Trung Kien Nguyen ◽  
Kiattisak Maichalernnukul ◽  
Feng Zheng ◽  
...  
Keyword(s):  
Spatial Correlation ◽  
Time Reversal ◽  
Channel Model ◽  
Line Of Sight ◽  
Channel Measurements ◽  
Virtual Mimo ◽  
Correlated Channels ◽  
Multiple Transmit ◽  
Correlated Channel ◽  
The Impact

The impact of spatial correlation on the multi-input multi-output ultrawide band (MIMO-UWB) system using the time reversal (TR) technique is investigated. Thanks to TR, several data streams can be transmitted by using only one antenna in a system named virtual MIMO-TRUWB. Since the virtual MIMO-TR-UWB system is not affected by the transmit correlation, under the condition of the high spatial correlation, it outperforms the true MIMO-UWB system with multiple transmit antennas. The channel measurements are performed in short-range indoor environment, both line-of-sight and non-line-of-sight to verify the adopted correlated channel model.

Performance Funding Policy Effects on Community College Outcomes: Are Short-Term Certificates on the Rise?

2017 ◽  
Vol 46 (1) ◽  
pp. 3-39 ◽  
Author(s):  
Amy Y. Li ◽  
Alec I. Kennedy
Keyword(s):  
Postsecondary Education ◽  
Performance Metrics ◽  
State Level ◽  
Cost Effective ◽  
Performance Funding ◽  
Funding Policy ◽  
Level Control ◽  
Medium Term ◽  
Short Term ◽  
The Impact

Objective: Performance funding (PF) policies allocate a portion of state funding to colleges based on student outcomes. This study is the first to account for policy type and design differences, and explores the impact of performance funding on three levels of credential completions: short-term certificates, medium-term certificates, and associate’s degrees. Method: We create a panel dataset of 751 two-year colleges from years 1990 to 2013 using data from the Integrated Postsecondary Education Data System. We conduct a series of analyses using difference-in-differences with the inclusion of college- and state-level control variables. Results: We find that, on average, performance funding produces no significant changes in completions of any of the three credentials. Policy types characterized by a greater proportion of funding tied to the base budget, mission differentiation in performance metrics, inclusion of underrepresented student metrics, and longer periods of operating years produce an increase in short-term certificates, no significant change in medium-term certificates, and a decrease in associate’s degrees. Contributions: This study’s findings suggest that because awarding more short-term certificates is a relatively quick and cost-effective way to capture performance funds, colleges might be engaging in a path of least resistance by churning out short-term certificates and redirecting focus away from associate’s degrees, which is concerning given that short-term certificates generally offer limited labor market benefits compared to medium-term certificates and associate’s degrees. Our results also underscore the importance of policy designs in explaining differential impacts on credential completion.

scholarly journals Sum Rate of Multiuser Large-Scale MIMO in the Presence of Antenna Correlation and Mutual Coupling

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Yusheng Li ◽  
Kang An ◽  
Tao Liang ◽  
Weixin Lu
Keyword(s):  
System Performance ◽  
Mutual Coupling ◽  
Large Scale ◽  
Mimo System ◽  
Base Station ◽  
Closed Form Expression ◽  
Channel State ◽  
Antenna Correlation ◽  
Sum Rate ◽  
The Impact

A multiuser large-scale MIMO system with antenna correlation and mutual coupling is investigated in this paper. Based on the maximum signal-to-interference-plus-noise ratio (SINR) criteria, the optimal beamforming (BF) vector at the base station (BS) for each user is first obtained using statistical channel state information (CSI). Then, a closed-form expression for the achievable sum rate is derived in terms of a finite number of generalized Meijer-G functions, which is applicable to an arbitrary number of array elements and/or users, and provides an efficient means of evaluating the system performance. Finally, numerical results are provided to confirm the validity of the theoretical analysis and show the impact of various channel parameters on the system performance.

scholarly journals A non-stationary relay-based 3D MIMO channel model with time-variant path gains for human activity recognition in indoor environments

2021 ◽  
Author(s):  
Rym Hicheri ◽  
Ahmed Abdelgawwad ◽  
Mathias Pätzold
Keyword(s):  
Doppler Shift ◽  
Channel Model ◽  
Mimo System ◽  
The Body ◽  
Mimo Channel ◽  
Indoor Environments ◽  
Indoor Space ◽  
Received Power ◽  
Rf Signal ◽  
The Impact

AbstractExtensive research showed that the physiological response of human tissue to exposure to low-frequency electromagnetic fields is the induction of an electric current in the body segments. As a result, each segment of the human body behaves as a relay, which retransmits the radio-frequency (RF) signal. To investigate the impact of this phenomenon on the Doppler characteristics of the received RF signal, we introduce a new three-dimensional (3D) non-stationary channel model to describe the propagation phenomenon taking place in an indoor environment. Here, the indoor space is equipped with a multiple-input multiple-output (MIMO) system. A single person is moving in the indoor space and is modelled by a cluster of synchronized moving point scatterers, which behave as relays. We derive the time-variant (TV) channel transfer function (CTF) with TV path gains and TV path delays. The expression of the TV path gains is obtained from the instantaneous total received power at the receiver side. This TV total received power is expressed as the product of the TV power of the RF signal initially transmitted and received by a body segment and the TV received power of the redirected signal. These TV powers are determined according the free-space path-loss model. Also, a closed-form approximate solution to the spectrogram of the TVCTF is derived. Here, we analyse the effect of the motion of the person and the validity of the relay assumption on the spectrogram, the TV mean Doppler shift (MDS), and the TV Doppler shift (DS) of the TVCTF. Simulation results are presented to illustrate the proposed channel model.

scholarly journals Measurement-Based Spatial Correlation and Capacity of Indoor Distributed MIMO System

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Yan Zhang ◽  
Limin Xiao ◽  
Shidong Zhou ◽  
Jing Wang
Keyword(s):  
Spatial Correlation ◽  
Antenna Selection ◽  
Mimo System ◽  
Correlation Coefficients ◽  
Small Scale ◽  
Channel Measurements ◽  
Wireless Access Networks ◽  
Indoor Scenarios ◽  
Transmitting Antenna ◽  
The Impact

Distributed MIMO (D-MIMO) system is one of the candidates for future wireless access networks. In this study, the spatial correlation and capacity in indoor D-MIMO system are presented. All results are from the actual channel measurements in typical indoor scenarios, including office and corridor. Based on measured data, spatial correlation coefficients between distributed transmitting antennas are analyzed. Although the literature about D-MIMO system assumes the small scale fading between distributed antennas is independent, we find that spatial correlation may still exist in specific propagation scenario. This correlation can also degrade the performance of D-MIMO system. To mitigate the impact of spatial correlation, one efficient method is to use transmitting antenna selection technique.

scholarly journals Investigation into the Impact of Mutual Coupling on the Performance of a Multiuser MIMO System Employing Generalized Channel Inversion Technique

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Feng Wang ◽  
Konstanty Bialkowski ◽  
Marek E. Bialkowski
Keyword(s):  
Mutual Coupling ◽  
Mimo System ◽  
Mobile User ◽  
Base Station ◽  
Multiuser Mimo ◽  
Simulation Experiments ◽  
Rate Capacity ◽  
Sum Rate ◽  
The Impact ◽  
System Operating

In this paper, the performance of generalized channel inversion (GCI) technique for a multiuser MIMO system operating under antenna mutual coupling conditions is investigated. The investigation is performed via theoretical derivations and computer simulations. The theoretical derivations show that the presence of mutual coupling may result in an increased performance in terms of sum rate capacity. The simulation experiments confirm the theoretical findings in examples of three groups of numerical results. These results show that the existence of mutual coupling in an array antenna at base station (BS) results in an increased sum rate capacity when antenna interelement spacing at BS is smaller than 0.55 λ. Also it is shown that the presence of mutual coupling at mobile user (MS) terminals results in an increased sum rate capacity when antenna inter-element spacing at MSs is smaller than 0.4 λ. When mutual coupling is considered at both BS and MSs, the system configuration with antenna inter-element spacing equal to 0.45 λat BS and 0.4 λat MSs leads to the highest sum rate capacity.

Regulatory and sustainability initiatives lead to improved polyaminopolyamide epichlorohydrin (PAE) wet-strength resins and paper products

TAPPI Journal ◽  
2018 ◽  
Vol 17 (09) ◽  
pp. 519-532 ◽  
Author(s):  
Mark Crisp ◽  
Richard Riehle
Keyword(s):  
Health And Safety ◽  
Cost Effective ◽  
Worker Safety ◽  
Regulatory Requirements ◽  
Wet Strength ◽  
The Past ◽  
Consumer Safety ◽  
Federal Institute ◽  
Sustainability Initiatives ◽  
The Impact

Polyaminopolyamide-epichlorohydrin (PAE) resins are the predominant commercial products used to manufacture wet-strengthened paper products for grades requiring wet-strength permanence. Since their development in the late 1950s, the first generation (G1) resins have proven to be one of the most cost-effective technologies available to provide wet strength to paper. Throughout the past three decades, regulatory directives and sustainability initiatives from various organizations have driven the development of cleaner and safer PAE resins and paper products. Early efforts in this area focused on improving worker safety and reducing the impact of PAE resins on the environment. These efforts led to the development of resins containing significantly reduced levels of 1,3-dichloro-2-propanol (1,3-DCP) and 3-monochloropropane-1,2-diol (3-MCPD), potentially carcinogenic byproducts formed during the manufacturing process of PAE resins. As the levels of these byproducts decreased, the environmental, health, and safety (EH&S) profile of PAE resins and paper products improved. Recent initiatives from major retailers are focusing on product ingredient transparency and quality, thus encouraging the development of safer product formulations while maintaining performance. PAE resin research over the past 20 years has been directed toward regulatory requirements to improve consumer safety and minimize exposure to potentially carcinogenic materials found in various paper products. One of the best known regulatory requirements is the recommendations of the German Federal Institute for Risk Assessment (BfR), which defines the levels of 1,3-DCP and 3-MCPD that can be extracted by water from various food contact grades of paper. These criteria led to the development of third generation (G3) products that contain very low levels of 1,3-DCP (typically <10 parts per million in the as-received/delivered resin). This paper outlines the PAE resin chemical contributors to adsorbable organic halogens and 3-MCPD in paper and provides recommendations for the use of each PAE resin product generation (G1, G1.5, G2, G2.5, and G3).

Exploring the Benefits of Early Contractor Involvement (ECI) and the Mechanism for Automated 5D BIM Quantification Process in Offsite Modular Construction

2016 ◽  
Author(s):  
Tochukwu Moses ◽  
David Heesom ◽  
David Oloke ◽  
Martin Crouch
Keyword(s):  
Effective Means ◽  
Cost Effective ◽  
Modular Construction ◽  
Automated Quantification ◽  
Building Information ◽  
Project Risks ◽  
Value Add ◽  
The Uk ◽  
The Impact ◽  
Level 2

The UK Construction Industry through its Government Construction Strategy has recently been mandated to implement Level 2 Building Information Modelling (BIM) on public sector projects. This move, along with other initiatives is key to driving a requirement for 25% cost reduction (establishing the most cost-effective means) on. Other key deliverables within the strategy include reduction in overall project time, early contractor involvement, improved sustainability and enhanced product quality. Collaboration and integrated project delivery is central to the level 2 implementation strategy yet the key protocols or standards relative to cost within BIM processes is not well defined. As offsite construction becomes more prolific within the UK construction sector, this construction approach coupled with BIM, particularly 5D automated quantification process, and early contractor involvement provides significant opportunities for the sector to meet government targets. Early contractor involvement is supported by both the industry and the successive Governments as a credible means to avoid and manage project risks, encourage innovation and value add, making cost and project time predictable, and improving outcomes. The contractor is seen as an expert in construction and could be counter intuitive to exclude such valuable expertise from the pre-construction phase especially with the BIM intent of äóÖbuild it twiceäó», once virtually and once physically. In particular when offsite construction is used, the contractoräó»s construction expertise should be leveraged for the virtual build in BIM-designed projects to ensure a fully streamlined process. Building in a layer of automated costing through 5D BIM will bring about a more robust method of quantification and can help to deliver the 25% reduction in overall cost of a project. Using a literature review and a case study, this paper will look into the benefits of Early Contractor Involvement (ECI) and the impact of 5D BIM on the offsite construction process.

MIMO Systems in a Composite Fading and Generalized Noise Scenario: A Review

2020 ◽  
Vol 14 ◽  
Author(s):  
Keerti Tiwari
Keyword(s):  
System Performance ◽  
Performance Enhancement ◽  
Channel Model ◽  
Mimo Systems ◽  
Mimo System ◽  
Spatial Diversity ◽  
Spatial Multiplexing ◽  
Channel Models ◽  
Efficient System ◽  
Composite Channel

: Multiple-input multiple-output (MIMO) systems have been endorsed to enable future wireless communication requirements. The efficient system designing appeals an appropriate channel model, that considers all the dominating effects of wireless environment. Therefore, some complex or less analytically acquiescent composite channel models have been proposed typically for single-input single-output (SISO) systems. These models are explicitly employed for mobile applications, though, we need a specific study of a model for MIMO system which can deal with radar clutters and different indoor/outdoor and mobile communication environments. Subsequently, the performance enhancement of MIMO system is also required in such scenario. The system performance enhancement can be examined by low error rate and high capacity using spatial diversity and spatial multiplexing respectively. Furthermore, for a more feasible and practical system modeling, we require a generalized noise model along with a composite channel model. Thus, all the patents related to MIMO channel models are revised to achieve the near optimal system performance in real world scenario. This review paper offers the methods to improve MIMO system performance in less and severe fading as well as shadowing environment and focused on a composite Weibull-gamma fading model. The development is the collective effects of selecting the appropriate channel models, spatial multiplexing/detection and spatial diversity techniques both at the transmitter and the receivers in the presence of arbitrary noise.

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