14 research outputs found
Halo orbit design around Lagrangian points using gradient and non gradient based optimization techniques
No full textMulti-IRS empowered terahertz wireless communication over generalized fading
No full textIntelligent reflecting surfaces (IRS) have emerged as a promising technology for addressing the inherent challenges associated with terahertz (THz) bands, thereby enhancing system performance and offering immense potential for future wireless systems. However, existing single and multi-IRS-aided wireless systems often overlook crucial IRS-related factors such as IRS unit-cell dimensions, IRS gain, and inter-IRS collaboration, potentially limiting system performance. To mitigate these limitations and leverage the unique advantages of the THz band, this study investigates a multi-IRS-empowered THz system that incorporates design parameters such as transceiver antenna gains, operation frequency, link distances, molecular absorption losses, beam misalignment, transceiver hardware imperfections, and statistical characteristics of the THz channel. By utilizing a sophisticated channel model that integrates the joint effects of these parameters with IRS properties and inter-IRS collaboration, this study demonstrates significant enhancement in system performance and power savings. Moreover, exact closed-form expressions and asymptotic approximations for outage probability are derived to quantify the effects of the deterministic and statistical channel parameters. These findings provide valuable insights into the practical implementation of multi-IRS-assisted THz networks, contributing to ongoing efforts to unlock the potential of the THz band for future wireless applications.Info-communications Media Development Authority (IMDA)National Research Foundation (NRF)This research is supported by the National Research Foundation, Singapore, under its Competitive Research Programme (NRF-CRP23-2019-0005), and the National Research Foundation, Singapore and Infocomrn Media Development Authority under its Future Communications Research & Development Programme (FCP-NTU-RG-2022-014)
Performance analysis of IRS-assisted terahertz communication system
No full textIntelligent reflecting surfaces (IRS), a new paradigm for controlling the wireless propagation environment, is an excellent cost-effective technology for terahertz (THz) systems. In this paper, the performance of an IRS-assisted THz system, with N reflective elements, is systematically analyzed over the deterministic IRS channel gain, the THz path loss model, and the sum of independent and non-identically distributed (i.ni.d.) cascaded a-µ fading channels. The probability density function (PDF) and the cumulative distribution function (CDF) of the proposed system are statistically characterized in terms of programmable multi-variate Fox's H function. Using derived statistical results, the closed-form solution for outage probability of THz-IRS system is reported along with its simple asymptotic expansions. The analytical results are validated using Monte-Carlo simulations. Results show that, sufficient signal-to-noise ratio (SNR) can be achieved with enough number of IRS antenna elements, making THz communication feasible.Info-communications Media Development Authority (IMDA)Ministry of Education (MOE)National Research Foundation (NRF)This research is supported by the Ministry of Education, Singapore, under its Academic Research Fund Tier 1, National Research Foundation, Singapore, under its Competitive Research Programme, and the National Research Foundation, Singapore and Infocomm Media Development Authority under its Future Communications Research & Development Programme
Related Data for: IRS-assisted access link-based multihop THz communication
No full textThis paper proposes an amplify-and-forward (AF) multihop terahertz (THz) backhaul communication system integrated with an intelligent reflecting surface (IRS)-assisted access THz link to address challenges in THz environments. The statistical analysis derives the probability density function (PDF) and cumulative distribution function (CDF) of the instantaneous signal-to-noise ratio (SNR) for the system, considering path loss, atmospheric attenuation, and generalized fading. Exact expressions for outage probability and asymptotic analysis in the high SNR regime are provided. Simulations validate the analysis and explore design aspects of the proposed system
IRS-assisted access link-based multihop THz communication
No full textThis paper proposes an amplify-and-forward (AF)-
based multihop THz backhaul communication integrated with
an access THz link. The access link is assisted with an intel-
ligent reflecting surfaces (IRS) with an aim to deal with the
impediments in THz communication environment. The statistical
analysis is presented by deriving the probability density function
(PDF) and cumulative distribution function (CDF) of the in-
stantaneous signal-to-noise ratio (SNR) for the proposed system.
The combined effect of path loss, atmospheric attenuation, and
generalized fading is considered for modelling the THz channel.
Furthermore, with the aid of PDF and CDF statistics, we
propose the exact expressions for outage probability and develop
asymptotic analysis in high SNR regime. The simulations are
presented to validate the exact analysis and to study various
design aspects for the proposed system.Info-communications Media Development Authority (IMDA)National Research Foundation (NRF)This research work is supported by the National Research Foundation, Singapore and Infocomm Media Development Authority under its Future Communications Research & Development Programme (FCP-NTU-RG-2022-014), and under its Competitive Research Programme (NRF-CRP23-2019- 0005)
Related Data for: Intelligent Reflecting Surfaces-Assisted Hybrid THz/RF System Over Generalized Fading
No full textThis paper investigates a novel IRS-assisted hybrid framework that seamlessly combines both THz and radio frequency (RF) technologies using a selection combining (SC) scheme, thereby enhancing system reliability. The study incorporates the deterministic and statistical properties of IRS in both RF and THz domains employing a sophisticated spatial scattering chan-nel model across generalized α - µ fading channels. Specifically, the exact closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the output signal-to-noise ratio (SNR) are derived for both THz and RF links. From this, the outage probability and average symbol error rate (SER) are derived
Intelligent reflecting surfaces-assisted hybrid THz/RF system over generalized fading
No full textIntelligent reflecting surface (IRS) technology is a promising solution for addressing the limitations of terahertz (THz) systems, including blockage effects and tremendous path loss. This paper investigates a novel IRS-assisted hybrid framework that seamlessly combines both THz and radio frequency (RF) technologies using a selection combining (SC) scheme, thereby enhancing system reliability. The study incorporates the deterministic and statistical properties of IRS in both RF and THz domains employing a sophisticated spatial scattering chan-nel model across generalized α - µ fading channels. Specifically, the exact closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the output signal-to-noise ratio (SNR) are derived for both THz and RF links. From this, the outage probability and average symbol error rate (SER) are derived. Furthermore, asymptotic expressions are evaluated for outage and average SER, offering insights into diversity gain of the system. Simulation results reveal a significant enhancement in system performance and power savings for the proposed IRS-aided hybrid THz/RF system. These findings provide valuable insights into the practical implementation of IRS-assisted hybrid networks, contributing to the ongoing efforts for future wireless networks.Info-communications Media Development Authority (IMDA)National Research Foundation (NRF)This research is supported by the National Research Foundation, Singapore, under its Competitive Research Programme (NRF-CRP23-2019-0005), and the National Research Foundation, Singapore and Infocomm Media Development Authority under its Future Communications Research & Development Programme (FCP-NTU-RG-2022-014)
Related Data for: Multi-IRS Empowered Terahertz Wireless Communication over Generalized Fading
No full textIntelligent reflecting surfaces (IRS) have emerged as a promising technology for addressing the inherent challenges associated with terahertz (THz) bands, thereby enhancing system performance and offering immense potential for future wireless systems. However, existing single and multi-IRS-aided wireless systems often overlook crucial IRS-related factors such as IRS unit-cell dimensions, IRS gain, and inter-IRS collaboration, potentially limiting system performance. To mitigate these limitations and leverage the unique advantages of the THz band, this study investigates a multi-IRS-empowered THz system that incorporates design parameters such as transceiver antenna gains, operation frequency, link distances, molecular absorption losses, beam misalignment, transceiver hardware imperfections, and statistical characteristics of the THz channel. By utilizing a sophisticated channel model that integrates the joint effects of these parameters with IRS properties and inter-IRS collaboration, this study demonstrates significant enhancement in system performance and power savings. Moreover, exact closed-form expressions and asymptotic approximations for outage probability are derived to quantify the effects of the deterministic and statistical channel parameters. These findings provide valuable insights into the practical implementation of multi-IRS-assisted THz networks, contributing to ongoing efforts to unlock the potential of the THz band for future wireless applications
Related Data for: Performance Analysis of IRS-assisted Terahertz Communication System
No full textIn this paper, the performance of an IRS-assisted THz system, with N reflective elements, is systematically analyzed over the deterministic IRS channel gain, the THz path loss model, and the sum of independent and non-identically distributed (i.ni.d.) cascaded α−µ fading channels. The probability density function (PDF) and the cumulative distribution function (CDF) of the proposed system are statistically characterized in terms of programmable multi-variate Fox’s H function. Using derived statistical results, the closed-form solution for outage probability of THz-IRS system is reported along with its simple asymptotic expansions. The analytical results are validated using Monte-Carlo simulations. Results show that, sufficient signal-to-noise ratio (SNR) can be achieved with enough number of IRS antenna elements, making THz communication feasible
Biased signalling in platelet G-protein‐coupled receptors.
No full textPlatelets are small megakaryocyte-derived, anucleate, disk-like structures that play an outsized role in human health and disease. Both a decrease in the number of platelets and a variety of platelet function disorders result in petechiae or bleeding that can be life threatening. Conversely, the inappropriate activation of platelets, within diseased blood vessels, remains the leading cause of death and morbidity by affecting heart attacks and stroke. The fine balance of the platelet state in healthy individuals is controlled by a number of receptor-mediated signaling pathways that allow the platelet to rapidly respond and maintain haemostasis. G-protein coupled receptors (GPCRs) are particularly important regulators of platelet function. Here we focus on the major platelet-expressed GPCRs and discuss the roles of downstream signaling pathways (e.g., different G-protein subtypes or β-arrestin) in regulating the different phases of the platelet activation. Further, we consider the potential for selectively targeting signaling pathways that may contribute to platelet responses in disease through development of biased agonists. Such selective targeting of GPCR-mediated signaling pathways by drugs, often referred to as biased signaling, holds promise in delivering therapeutic interventions that do not present significant side effects, especially in finely balanced physiological systems such as platelet activation in haemostasis.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
