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Non-orthogonal multiple access (NOMA) is considered as a potential multiple access technique for supporting massive number of devices with high spectral efficiency for the 5 G and beyond networks. Simultaneous wireless information and power transfer (SWIPT) is considered as an efficient solution for fully autonomous and sustainable communication networks. In this paper, application of SWIPT in heterogeneous networks (HetNets) employing cooperative NOMA (CNOMA) is investigated. The HetNets consists of macro-base stations (MBS) under-laid by small-base stations (SBS). The distribution of MBSs follow Poisson point process model, while the SBS tier supports NOMA and carrier sensing for its transmission. Carrier sensing helps in reducing interference by blocking the base stations within a specific range from transmitting. In this work, the analysis at SBS tier is carried out in two phases. In the direct phase transmission, the SBS transmits the superimposed signal to a user pair, comprising of a cell-centre user (CCU) and a cell-edge user (CEU), using NOMA principle. The CCU acts as a cooperative relay to forward information to the CEU in the cooperative phase. Unlike existing literature, instead of using only the superimposed signal for energy harvesting (EH), in this work, the cooperating user (i.e. CCU) employs EH using interference from the adjacent base stations along with the EH from the superimposed signal. Expressions for outage probability and throughput are derived at the user pair served using NOMA. Comparison of the proposed EH system with existing solutions are highlighted and useful insights are drawn. Monte Carlo simulations are carried out to validate the analytical results.

The ever-increasing number of wireless users (or devices) and their varied demand require the need for an advanced architecture for the future wireless network. To support massive connectivity, non-orthogonal multiple access (NOMA) has been recognized as a promising solution. NOMA increases the number of simultaneous connections using available resources for users with varying demands. Furthermore, recent measurements and experiments suggest that wide underutilized bandwidth available at millimeter-wave (mmWave) frequencies provide high data rate and therefore are capable of addressing the issue of spectrum scarcity at sub-6 GHz bands utilized by the 4G network. Consequently, co-existence of multi-radio access technologies (RATs) for 5G and beyond networks has been of interest to both industries and academia. In this context, this work studies the co-existence of the two RATs, namely, sub-6 GHz and mmWave communication using NOMA-enabled hybrid heterogeneous network (NOMA-HHN) for massive connectivity. The application of NOMA requires ordering users, which in turn requires the knowledge of users’ channel state information (CSI). However, gathering and processing CSI of such a large number of users is difficult to implement in practice. Thus, a solution based on partial CSI is proposed. Additionally, a feedback scheme for user scheduling and RAT selection using dual association is proposed to reduce the initial access delay in beam-training at the mmWave network. Moreover, utilizing directional nature of the mmWave communication, random beamforming is used to reduce system overhead in a network with massive users. The analytical results are confirmed using Monte-Carlo simulation, and various significant advantages are noted for the proposed NOMA-HHN over existing architectures.

Exponential growth in number of users with diverse data rate requirements has lead to the heterogeneity of traditional cellular networks. To support massive number of users, nonorthogonal multiple access (NOMA) has emerged as a promising solution to achieve increased number of connections and higher spectral gains as compared to orthogonal multiple access (OMA). However, studies show that weak users (WU) and strong users (SU) served using NOMA (referred as NOMA-group) experience different throughputs. In a NOMA group, an SU achieves higher throughput than a WU. Further, as the number of users in a NOMA group increases, due to superposition of signal of multiple users in NOMA, the intra-group interference dominates, thereby reducing throughput of the WUs. This article proposes novel time slotting (TS) techniques that aims at user fairness amongst the users by increasing the throughput of WUs, especially when the number of users increases in a NOMA group. The power allocation coefficients and the time slot duration for the proposed TS techniques are optimized to satisfy the minimum throughput of each user in a NOMA group while maximizing the throughput of WUs. The fairness between the users is measured by calculating both quality of service fairness and quality of experience fairness experienced by the user. It is observed that the proposed TS technique improves the fairness measures significantly. Furthermore, energy efficiency (EE) is also calculated for the TS techniques using the optimized power allocation coefficients and time duration. The numerical results suggest improvement in the EE of the system along with enhancing user fairness amongst the users.

Two of the most challenging goals for the fifth generation (5G) and beyond communication systems are massive connectivity and higher capacity. The use of traditional orthogonal multiple access techniques limits the number of users that can be served using available resources due to orthogonality constraint. Moreover, the available resources may not be utilized effectively by alloted users thereby resulting in inefficiency and user unfairness. This imposes a severe drawback in cases where the number of users to be served are high, like in the Internet of Things or ultra-dense 5G networks. Hence, introducing non-orthogonality to multiple access scheme is advocated as a superior methodology to serve multiple users simultaneously, thereby achieving multi-fold enhancement in connectivity. In scenarios with massive number of users, non-orthogonal multiple access scheme (NOMA) increases the number of active connections by superimposing signals of multiple users on the same resource block, thereby also utilizing the available resources efficiently. This article presents an overview of the integration of NOMA with several other leading technologies for 5G and beyond networks to enhance the connectivity.

Ever increasing number of cellular users and their high data requirements necessitates need for improvement in the present heterogeneous cellular networks (HetNet). Non-orthogonal multiple access (NOMA) has proven its superiority for the 5th generation networks. This paper proposes a mathematical model for an improved HetNet with macro base station (MBS) and femto base station (FBS) tier. The FBS tier is equipped to support NOMA and carrier sensing for its transmissions. Carrier sensing prevents base stations within a certain range of the transmitter from transmitting, and hence, aids in reducing the interference. Offloading is performed for load balancing in HetNet, where the macro users (MU) from congested MBS tier are offloaded to the FBS tier. The FBS tier pairs the offloaded MU (OMU) with an appropriate pairing user (PU) to perform NOMA. The performance of the OMU is studied under different channel conditions with respect to the available PU at the FBS and some useful observations are drawn. A decrease in outage probability by $\text{74.04}\%$ for cell center user (CCU) and $\text{48.65}\%$ for cell edge user (CEU) is observed for low-density FBS. The outage probability decreases by $\text{99.60}\%$ , for both the CCU and CEU, for high-density FBS using the proposed carrier sensing in NOMA. The results are validated using simulations.

Rapid increase in number of cellular users and high demand for data has lead to the formation of multi-tier networks. Non-orthogonal multiple access (NOMA) has proved to be an efficient method to cater to the paradigm shift from 4G to 5G. This paper employs NOMA in an heterogeneous cellular network consisting of a macro base station (MBS) tier underlaid with femto base station (FBS) tier and device-to-device (D2D) tier, where NOMA is employed in FBS and D2D tier only. The congestion at the MBS tier is relieved by offloading macro users (MU) to the FBS tier. The offloaded MU are further supported by the D2D tier when the FBS tier fails to find a corresponding pairing user for the incoming offloaded MU. Since, absence of pairing user means outage for offloaded MU, D2D cooperation is employed, which decreases the rate outage probability by $86.87\%$ for the MU offloaded as cell edge user (CEU) in comparison to no cooperation. Also, a three times increase in ergodic rate and four times increase in sum ergodic rate for MU offloaded as CEU is achieved using cooperation from D2D tier. Verification of the results is done using Monte Carlo simulations.

The present antibiotic susceptibility testing (AST) techniques based on bacterial culture, gene amplification and mass spectrometry are highly time consuming, labour intensive or expensive. Impedance spectroscopy is an emerging tool for rapid bacterial analysis as it is label-free, real-time, affordable and high-throughput. The over-reliance of this technique on complex chip designs and cell enrichment strategies has, however, slowed its foray into clinical AST. We demonstrate a label-free approach in which a low conductivity zwitterionic buffer is used for boosting impedance sensitivity in simple interdigitated electrodes (IDEs) allowing rapid AST in just 20 min without any liquid flow, biofunctionalization or cell enrichment steps. The detection principle relies on measuring changes in solution resistance due to antibiotic-induced bacterial cell death or growth. While the death-based approach is faster (20 min), it's restricted to surface-acting bactericidal antibiotics. The cell growth approach is longer (60-80 min) but more versatile as it applies to all drug types. Results for antibiotic sensitivity analysis and minimum inhibitory concentration (MIC) determination are illustrated for Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus against a wide class of antibiotics (penicillins, cephalosporins, polymyxins, carbapenems etc.).

Studying the role of buffers in impedance spectroscopy is a relatively unexplored area. We demonstrate a special class of biologically relevant buffers known as Good's zwitterionic buffers that show improved performance over standard electrolyte buffers (e.g. PBS) currently widely used in impedance spectroscopy measurements of bacterial suspensions. Our theoretical and experimental comparisons of conductivity of classical and zwitterionic buffers at various different concentrations show that ion-ion interaction effects are significantly higher in zwitterionic buffers as compared to classical buffers at the concentrations at which they are used. This and the fact that zwitterions have larger sizes leads to the lowering of their conductivity which significantly improves their impedance sensing ability. We illustrate through an example of heat-induced ionic release in model S. typhi and S. aureus bacteria that having a low conductivity buffer is indeed beneficial for biological impedance measurements. In fact, the best buffer for impedance studies can be chosen solely based on their electrical properties as long as they are also biologically compatible. This gives Good's zwitterionic buffers an edge over conventional media as they satisfy both these criteria.

Antimicrobial resistance (AMR) is caused by inappropriate or excessive antibiotic consumption. Early diagnosis of bacterial infections can greatly curb empirical treatment and thus AMR. Current diagnostic procedures are time-consuming as they rely on gene amplification and cell culture techniques that are inherently limited by the doubling rate of the involved species. Further, biochemical methods for species identification and antibiotic susceptibility testing for drug/dose effectiveness take several days and are non-scalable. We report a real-time, label-free approach called DEPIS that combines dielectrophoresis (DEP) for bacterial enrichment and impedance spectroscopy (IS) for cell viability analysis under 60 min. Target bacteria are captured on interdigitated electrodes using DEP (30 min) and their antibiotic-induced stress response is measured using IS (another 30 min). This principle is used to generate minimum bactericidal concentration (MBC) plots by measuring impedance change due to ionic release by dying bacteria in a low conductivity buffer. The results are rapid since they rely on cell death rather than cell growth which is an intrinsically slower process. The results are also highly specific and work across all bactericidal antibiotics studied, irrespective of their cellular target or drug action mechanism. More importantly, preliminary results with clinical isolates show that methicillin-susceptible Staphylococcus aureus (MSSA) can easily be differentiated from methicillin-resistant S. aureus (MRSA) under 1 h. This rapid cell analyses approach can aid in faster diagnosis of bacterial infections and benefit the clinical decision-making process for antibiotic treatment, addressing the critical issue of AMR.

The increase in number of cellular users had lead to the evolution from the traditional cellular networks to the more efficient heterogeneous cellular networks (HetNet) to handle the traffic. Offloading plays a vital role in handling the traffic from the congested macro base station by handing users to the less congested femto base stations (FBS). Further, non-orthogonal multiple access (NOMA) has proved to be efficient for the future generation networks. In this work, we study the offloading in HetNets, where the FBS tier serves the users using NOMA. Imperfect channel state information (CSI) is considered to analyze the outage probability of offloaded user, since, in practice CSI estimation requires significant system overhead, especially when the number of users are large. Hence, for practical systems, the analyses with imperfect CSI is more relevant. Some important observations regarding offloading to FBS tier with NOMA based on imperfect CSI are drawn. The analytical results are validated using Monte Carlo simulations.

Surge in number of cellular users and data-intensive applications require the traditional cellular networks to evolve towards a more promising heterogeneous cellular networks (HetNets). Offloading in HetNets alleviates congestion on the overloaded cellular network where the femto base stations (FBS) acts as offloading spots. The offloaded user (OU) is paired with the user available at the FBS (called as pairing user (PU)) and served using non-orthogonal multiple access. Two parameters namely, power allocation factor (PAF), i.e., the power to be allocated to the OU, and channel ratio (CHR), i.e., the ratio of channel gain between the OU and the PU play a crucial role in determining the ergodic rate achieved by the OU. If the PAF and the CHR are not optimally selected, it results in degradation in overall rate performance. This work jointly optimizes the PAF and the CHR to maximize the ergodic rate performance of the OU. The impact of optimized and non-optimized parameters on the performance of OU is studied to prove the advantage of using optimized scenario for the OU. An increase of upto 3 times is observed in the ergodic rate and sum ergodic rate by using the optimized parameters.

The current literature characterizes the performance gain achieved by non-orthogonal multiple access (NOMA) using stochastic geometry based on the assumption of Poisson Point Processes (PPP) to model the spatial distribution of base stations. This paper develops an analytical framework to analyze the gain achieved by NOMA in a heterogeneous cellular network (HCN) consisting of a macro base station (MBS) tier and a femto base station (FBS) tier modeled using repulsive point process namely modified hard core point process (MoHCPP). It is observed that modeling NOMA network using MoHCPP approach decreases the outage probability by $ 74.04 \% $ for a cell center user (CCU) and by $48.65 \%$ for a cell edge user (CEU) as compared to NOMA using PPP. This improvement is attributed to decrease in dominant interferers due to thinning process of MoHCPP. It is also observed that with the increase in FBS density the advantage of NOMA with MoHCPP modeling is more for CEU as compared CCU due to additional benefit of dense FBSs for CEU. Hence, it is inferred that high density FBS network with NOMA modeled using MoHCPP proves to be better suited for CEU as compared to PPP modeling. The results for the proposed NOMA with MoHCPP model are also verified using simulations.

This paper describes the effect of varying experimental parameters on the morphology and optoelectronic response of cadmium telluride quantum dot (CdTe QD) microwires formed using alternating current dielectrophoresis (AC-DEP). The thioglyocolic acid (TGA) capped CdTe QDs were assembled at room temperature across interdigitated electrodes (IDEs) under an applied electric field while simultaneously allowing solvent evaporation. The number of iterative rehydration steps required for bridging the microelectrode gaps of sizes 50–150 μm was found to depend on the electric field strength, particle concentration and electrode gap size. The frequency of the AC field applied, particle concentration and capping ligand were further optimized to regulate the fluorescence intensity, current density and chemical sensing behavior of the microassemblies. The overall process was found to be simple, rapid and scalable, and potentially holds promise for energy and sensing applications.

Femtocell deployment improves the data rate and indoor coverage of the heterogeneous cellular network (HCN). However, it also increases the cross-tier interference of the system which results in performance degradation of the macro base station (MBS) tier. In this work, a mathematical framework is developed to mitigate the cross-tier interference of MBS tier using a power control scheme (PCS). This PCS works on path loss inversion and location-based power level rule for femto base stations (FBS) to improve the coverage of the MBS tier. Furthermore, a cooperation scheme and association policy are proposed to improve the performance of the FBS tier. Stochastic geometry is considered for deriving the signal to interference and noise ratio (SINR) outage probability, total outage probability, and area spectral efficiency (ASE) for MBS and FBS tiers. The impact of the PCS, proposed cooperation scheme with association policy on outage probability, and ASE are numerically evaluated. Numerical results show that considerable improvement in outage performance of MBS tier is obtained using proposed PCS. Moreover, applying PCS results in degradation of outage performance of FBS tier. This loss in performance can be compensated by using the proposed cooperation scheme and association policy.

A simplified analytical drain current model for the long-channel pinch-off junctionless (JL) double-gate field effect transistor (DGFET) is proposed. The drain current is generally expressed in terms of the mobile charge density and it has been expressed in terms of the pinch-off voltage and the gate capacitance. The proposed model is validated against TCAD simulation results, and is able to predict the behaviour of the JL DGFET for different bias conditions and device dimensions, accurately. The transconductance and the transconductance-to-drain-current ratio are important parameters for analogue circuits, and have been calculated and exhibit good agreement with the TCAD results.