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The development of wireless technology has penetrated in femtocell communication systems, where this communication system is very flexible to develop. However, with many networks running simultaneously, which is called a heterogeneous network, a combination of macrocell and femtocell networks, interference between networks is unavoidable. To resolve this interference, it can be done with adaptive power control techniques by the user. Adaptive power control can be achieved through the use of Game Theory and also known as Power Control Game (PCG). By determining the appropriate utility function, the optimal power is obtained when using the power update iteration process. The results show that in the Proposed method when it reaches a convergent condition, both femto users and macro users are able to reach SINR that exceeds the target SINR of 5.496 for femto users and 10.04 for macro users. Meanwhile, the Distributed Power Control (DPC) method is only able to achieve the SINR user value which is the same as the target SINR, which is 5 and 10 for femto users and macro users, respectively. The Proposed method produces a higher SINR value for the user than the DPC method so that in terms of achieving the target SINR, it is possible to conclude that the Proposed approach is superior to the DPC.

For FD-OFDMA communications we focus on resource allocation in two-tier macro-femto HetNets, in which macrocell and femtocell share spectrum .Based on OFDMA technology, we are considering here Full duplex of FBS and Half duplex of MBS and its users FUE. Macrocell got interference from users and FBS in form of crosstier To mitigate cross-tier interference, we develop model for joint subcarrier assignment, power allocation and price regulation which will maximize the utility of both macrocell and femtocell under the interference constraint for the macrocell We are demonstrate a power control, subcarrier allocation and price regulation as a joint triple optimization algorithm which solve the cross-tier interference of femtocell to macrocell. For utility enhancement we use price based resource allocation by proposed CSO cat swarm optimization Algorithm. Subcarriers assignment to the user pair is done for maximization the femtocell utility. The simulation results show effectively suppress of cross-tier interference with maximization of the utility of macrocell and femtocell.

Excitons are electron-hole quasi-particles, which strongly influence the electro-optical properties of solids and hold the potential for a variety of applications [1] . Acquiring a detailed understanding of their dynamic nature is thus essential to promote their exploitation in advanced technological areas. In particular, the ultrafast processes unfolding at the femto- and attosecond domain are of primary relevance in view of the desired extension towards the petahertz regime. Here we applied attosecond transient reflectivity spectroscopy to study the ultrafast response of a MgF2 single crystal and report the first observation of sub-fs core-exciton dynamics [2] . Combined with simulations, our results allowed us to disentangle the dual atomic-solid nature of this fundamental quasi-particle.

The diverse architectural evolution and intensive data explosion in the forthcoming 5G will have severe impacts on providing seamless and robust mobility management. In this paper, P-persistent energy-aware handover (HO) decision strategies with mobility robustness are proposed both for intra-handover cases while a femto user equipment (FUE) roams into another femto access point (FAP) and for cross-tier handover cases while a macro user equipment (MUE)/FUE roams into/out of the FAP in a dynamic cell sizing involving macro-femto two-tier networks. To approximate the densely deployed small-cells, a unique RF fingerprint (RFF)-based localization is employed to enable efficient small-cell detection by an RFF matching mechanism. The prediction of the HO trigger is jointly determined by a P-persistent decision mechanism that formulates the specific HO behaviors when an MUE/FUE roams into (HO-in) and out of (HO-out) a femtocell in terms of the correlated coverage variance and UE trajectory features, whereas the target selection follows a utility function in consideration of the UE traveling time and the achievable throughput. The closed-form stationary probabilities of the proposed VHO/HHO decisions are analyzed by a Semi-Markov-based framework. In addition, an adjustable sensing mechanism with dynamic intervals is proposed when UE is located far from the RFF matching region, which can have a positive influence on reducing unnecessary UE energy consumption. Numerical results are presented for the decision accuracy analyses (too early, too late, and ping-pong HOs), energy-efficiency, and resource utilization of the two-tier system. The comprehensive evaluations indicate that the proposed scheme can enhance the mobility robustness and enable an optimal trade-off between the energy efficiency (EE) and system capacity while eliminating the architectural impacts caused by the dynamic topology and the dense deployment for the next-generation macro-femto two-tier networks.

The deployment of heterogeneous networks (HetNets) is one of the promising approaches to meet the 5G requirements. The traditional user association approach is inefficient for HetNets due to the high transmission power of macro base stations (BSs) and the low transmission power of small cell BSs, i.e., pico and femto BSs. This approach causes macro BSs to be overloaded whereas small cell BSs are lightly loaded. To address this load imbalance in 5G HetNets, 3GPP introduced the concept of cell range expansion (CRE) where the coverage area of small cell BSs is artificially increased by adding a bias value to the power received from small cells. Although the biasing approach can better balance the load among tiers, users at the expansion area suffer from severe interference coming from neighbouring macro BSs. This work utilizes coordinated multi-point transmission (CoMP) to reduce interference. User-centric clustering where a user can be served by a number of BSs is implemented. The results have sown that user-centric CoMP can significantly improve the SINR levels of all users and cell-edge users as well.

Macro-femto heterogeneous network (HetNet) comes with tremendous inter and intra cell interference problems. This paper considered fifth generation (5G) non-stand-alone (NSA) architecture. An enhanced active power control technique (EAPC) is proposed to mitigate interference in uplink macro-femto HetNet. The MATLAB simulation result obtained in terms of average power consumption of macrocell user equipment (MUE) and femtocell user equipment (HUE) using EAPC technique stood at 6.7 dBm and 7.5 dBm respectively, as against that of active power control (APC), fixed power control (FPC) and power control 1 (PC1); which stood at 10.9 dBm, 23.0 dBm, 14.8 dBm for MUE and 11.1 dBm, 23.0 dBm, 14.8 dBm for HUE respectively. It indicates that HUE and MUE using EAPC technique had low average power consumption when benchmark. 5G NSA macrocell base station (en-gNB), 60% cumulative distributive function (CDF) of throughput based on EAPC, APC, PC1 and FPC techniques had 36.2 Mbps, 15.0 Mbps, 24.0 Mbps and 12.5 Mbps throughput respectively. And that of femtocell base station (Hen-gNB) according to EAPC, APC, PC1 and FPC was 25.0 Mbps, 23.0 Mbps, 10.0 Mbps and 18.6 Mbps throughout, respectively. This implies that EAPC has better Hen-gNB and en-gNB throughput when benchmarked with other related techniques. Hence, the proposed EAPC technique improves 5G network performance in terms of better throughput and conserving limited user equipment (UE) energy.

Vehicular communication has emerged as a powerful tool for providing a safe and comfortable driving experience for users. Long Term Evolution (LTE) supports and enhances the quality of vehicular communication due to its properties such as, high data rate, spatial reuse, and low delay. However, high mobility of vehicles introduces a wide variety of security threats, including Denial-of-Service (DoS) attacks. In this paper, we propose an effective solution for real-time detection and localization of DoS attacks in an LTE-based vehicular network with mobile network components (e.g., vehicles, femto access points, etc.). We consider malicious data transmission by vehicles in two ways - using real identification (unintentional) and using fake identification. Our attack detection technique is based on data packet counter and average packet delivery ratio which helps to efficiently detect attack faster than traditional approaches. We use triangulation method for localizing the attacker, and analyze average packet delay incurred by vehicles by modelling the system as an M/M/m queue. Simulation results demonstrate that our proposed technique significantly outperforms state-of-the-art techniques.

In cellular networks, majority of calls and data services occur in indoor areas. In some areas, macrocell does not give adequate indoor network coverage, and thus, many households and businesses experience a poor indoor coverage problem. As a result, in those areas voice and data service quality are very poor and users do not get satisfactory services. To overcome this problem, in many indoor areas, users can use small Cell network known as Femto Base Transceiver Station (BTS) or Home Node B (HNB). Femto BTS gives strong network coverage in indoor areas and it can offload traffic from macrocell layer and improve macrocell capacity. Outdoor users connect to the macro cells and when they enter into their homes, they connect to their femtocell. However, there are some problems for deploying femto BTS in indoor areas. When femto BTS are placed in indoor areas, some macro BTS signal are transmitted from outdoor to indoor and Femto BTS signal also spreads to outside areas. This unwanted signal creates interference. To overcome these problems, interference management is very important. When a user moves from one place to another, successful handover is needed. In this work, we proposed interference management scheme by using power control. To improve mobility management services in indoor environment, we also proposed a handover (HO) procedure from one femto cell to another femto cell. MATLAB is used to implement these techniques. The results prove improved interference management and solve the challenges of higher demand of indoor network coverage and mobility management for femto cells in indoor environments.

The number of devices connected to Internet of Things (IoT) and massive machine-type communication (mMTC) networks is expected to increase exponentially in the next generation of wireless communication systems, resulting in a new type of “massive” random access network. However, most of the work in this emerging field considers the single-hop setting with direct communication between the users and a fully-equipped base station. In contrast, this work explores the massive random access problem in a two-hop relay setting where users access the network through a femto- or pico-cell relay which itself only has a limited amount of bandwidth/power. We present two low-complexity relaying schemes designed to minimize power consumption and discuss their tradeoffs using numerical simulations.

MagnetoMyoGraphy (MMG) with superconducting quantum interference devices (SQUIDs) enabled the measurement of very weak magnetic fields (femto to pico Tesla) generated from the human skeletal muscles during contraction. However, SQUIDs are bulky, costly and require working in a temperature-controlled environment, limiting wide-spread clinical use. We introduce a low-profile magnetoelectric (ME) sensor with analog frontend circuitry that has sensitivity to measure pico-Tesla MMG signals at room temperature. It comprises magnetostrictive and piezoelectric materials, FeCoSiB/AlN. Accurate device modelling and simulation are presented to predict device fabrication process comprehensively using the finite element method (FEM) in COMSOL Multiphysics®. The fabricated ME chip with its readout circuit was characterized under a dynamic geomagnetic field cancellation technique. The ME sensor experiment validate a very linear response with high sensitivities of up to 378 V/T driven at a resonance frequency of fres = 7.76 kHz. Measurements show the sensor limit of detections of down to 175 pT/Hz at resonance, which is in the range of MMG signals. Such a small-scale sensor has the potential to monitor chronic movement disorders and improve the end-user acceptance of human-machine interfaces.

5G based heterogeneous networks (HetNets) have been attracting interest recently to support manufacturing processes in smart factory use cases. Smart factories require high performing wireless systems with high data rates and improved spectral efficiency to support mobile robots and other autonomous vehicles for example. To provide low latency, high coverage 5G deployments, comprised of multi-tier, Femto, Pico, and Macro cell networks are seen as a possible solution to meeting the required data rate requirements. This work analyzes the impact of base stations association strategies such as Maximum Received Power and Maximum Signal to Interference Plus Noise Ratio (SINR) for a 5G HetNet for Low Mobility robots and High Mobility autonomous guided vehicles in conjunction with fixed wireless sensor/actor devices. Experimental results show that our deployment scheme combined with the Maximum Received Power cell association strategy outperforms the Maximum SINR cell association strategy.

This paper introduces the test technology of redistribution layer used in FOPLP. In order to lower costs, FOPLP needs to adopt the RDL first process. In addition, it is necessary to guarantee that the package such as 2.5D that formed RDL is non-defective before mounting ICs. Since RDL is mounted on a carrier such as glass, double-sided inspection of the package becomes difficult. It is capacity inspection that can be proposed as this solution. In our work, we have improved the micro capacity tester to the accuracy below femto farad. Using this tester, we have demonstrated defect detection between RDL vias, formation defects of plating etc., in the package manufactured in an actual process. This method also allowed us to consolidate probing on one side. We introduce technologies for solving 40 um fine pitched micro pad probing problems as well as achieving a lower cost of test for a line and space 2/2 um FOPLP.

International audience; 5G Wireless Networks are expected to increase substantially data rates and quality of service the users will experience , with a similar or a lower power consumption as todays 4G networks. The Joint Transmission Coordinated MultiPoint (JT-CoMP) is a promising scheme to enhance throughput by reducing the interference, especially for cell-edge users. However, some additional energy for hardware circuit and resource information is consumed by this technology. Meanwhile, the performance evaluation of energy efficiency (EE) in dense networks with JT-CoMP approach becomes a hard task in terms of time expense to conduct simulations. To evaluate the EE metric in cellular networks with JT-CoMP scheme and to capture the major factors involved in the energy consumption process, representative and accurate models are needed. In this paper, we develop a tractable and efficient model of EE based on spatial fluid modeling when JT-CoMP is applied. Simulations results show that EE is improved with the raise of the number of coordinated BSs in case of a constant backhauling power cost. Similar EE improvement is also observed in case of variable backhauling power cost, while adding a new coordinated BS. Furthermore, the EE is significantly enhanced in femto cellular networks compared to macro cellular ones, making thereby, JT-CoMP scheme more effective in small cells.

Cooperative communication is one of the emerging technologies that promise significantly higher reliability and spectral efficiency in wireless networks. It is a new form of diversity that allows users or nodes to share resources to create collaboration via distributed transmission and processing of messages. As candidate multiple access for future radio access, Non orthogonal multiple access (NOMA) over orthogonal multiple access (OMA) are adopted as downlink access scheme for future 5th generation mobile communication. In this paper, we compare user throughput when using orthogonal multiple access (OMA) and NOMA in macro femto network. We show through computer simulation the effect of imperfect interference cancellation on user throughput. We assist the performance of user selection when using fixed power allocation. Finally, we propose NOMA with COMP scenario whose performance improvement lead for user and cell throughput.

We address a resource allocation problem for joint caching and broadcast transmission in small cell networks with time-varying statistical properties. Each small base station (SBS) selects some files to store in its capacity-limited cache, given no prior information about the random and dynamic parameters such as file popularity, channel quality, and network traffic. Moreover, at consecutive rounds, a file is selected from the cache to broadcast. We define the utility of the SBS in terms of the number of successful file receptions per power consumption. The problem is formulated as to place the cache, and afterward select a file from the cache together with a transmission power for every broadcast round. The goal is to maximize the accumulated utility over the horizon. Therefore, we decompose the initial problem into two sub- problems: (i) cache placement, and (ii) joint file- and transmit power selection. The former problem boils down to a stochastic knapsack problem with stationary items' value, whereas the latter is cast as a multi-armed bandit problem with mortal arms. We develop a solution to each problem and evaluate the proposed solutions by theoretical and numerical analysis.

Ultra low current measurement has a wide range of applications spanning varied fields of science. The front end electronics of radiation monitors demand circuits capable of measuring currents as low as femto amperes. Current to frequency converters forms the heart of such low current measurement circuits. Majority of the reported designs for such circuits are realized in 350 nm technology node or higher. Lower nodes suffer from the limitation of leakage currents which impedes such measurements. In this paper, a 22 nm FDSOI technology node is analyzed as a potential technology for low current measurements. A test structure has been designed and its capability to measurement currents with 1 fA sensitivity has been demonstrated.

The distance threshold, which is used to distinguish the cell-edge region from the cell- center region, is an important factor in fractional frequency reuse (FFR) system performance. In this paper, we study the optimal distance threshold to maximize system throughput in the downlink cellular networks including aerial base stations. Subject to the constraint that a given target outage probability is satisfied, the optimal distance threshold is analyzed as a function of cell size. It is proven that when the sizes of all cells in the network are scaled at the same rate, the optimal distance threshold normalized by cell size is non-decreasing in the cell size. The analytical results in this paper provide a system design guideline for initial planning of FFR cellular networks of different sizes including macro, pico, and femto systems. In particular, for size-scalable aerial networks comprising base stations in the sky, such as balloons or unmanned aerial vehicles, our analysis offers insight into the design of the distance threshold with regard to cell size.

In this paper a non-coding method for analyzing big data without the use of Hadoop, Hive, Pig, etc. was demonstrated with the use of Neural Network regression (NNR) for predicting the remaining useful life (RUL) of a bearing. Using these nonlinear nonparametric approach to predict the RUL of a bearing is intuitively appealing. The applications of NNR model have surged over the years that it has now been recognized as a major forecasting technique in a forecaster's toolbox hence, its application here on the NASA FEMTO BEARING DATASET. The motivation for this paper is to check if without using the normal big dataset, structuring the NNR models would add value in its applications. Although comparing this results is worth doing, the ultimate decision remains with NASA FEMTO as we are checking our result against their obtained experimental value which is in their archive. In the end, for the time series concerned, we clearly showed that NNR models do indeed add value in the forecasting process and we hope that our predicted RUL for the dataset of NASA FEMTO provided which they want a predicted result is accepted within a close range.

In this paper, an auction-based spectrum leasing for hybrid access in macro-femto network with location sensing is proposed to maximize the utilities of MBS and FAPs. The macrocell base station (MBS) owns all available spectrum resource and leases its spectrum to femtocell access points (FAPs) in order to get revenue. MBS offloads the macro UEs (MUEs) which are closer to the FAPs to improve the energy efficiency of the system. Auction mechanism is introduced to analyze the spectrum renting problem. We assume each FAP bids while the MBS acts as the auctioneer. The FAPs decide their bids independently of each other. Then MBS collects the bids of FAPs and determines the optimal allocation strategy. The MBS leases the spectrum to FAPs in order to get revenue, but it compensates FAPs for serving the additional MUEs. Simulation results validate the validity of this spectrum leasing scheme.

We present a novel logic family, titled feedforward leakage self-suppression logic (FLSL), for nanowatt and sub-nanowatt always-on circuits. It addresses the prohibitively long delay of existing ultra-low leakage logic families without requiring sleep or mode control signals to exercise the leakage-suppression mode. Implemented in 180-nm CMOS, the proposed logic family achieves femto-watt per-gate leakage and a fan-out-of-4 (FO4) delay of 10.2 µs, a remarkable speed enhancement of 150X over the prior art in the same process in the same leakage level. We also investigate the impact of technology scaling by designing the FLSL logic family additionally in 65-nm and 28-nm processes. In a 28-nm process, the FLSL can achieve about 70 ns FO4 delay and 10 picowatts per-gate leakage. Finally, we prototype a finite impulse response filter core for physical sensing systems in a 180 nm. The filter can achieve the power consumption of 109 picowatts for sparse, i.e., predominantly constant or slowly changing, input signals at 1 kHz clock frequency.

In this paper an adaptive power control for co-channel femtocells in presented. In order to avoid co-channel interference, the femtocells have to sense the presence of macro users in the surrounding environment. Interference is avoided through applying adaptive power control on the femtocell downlink. Also, the femtocells are equipped with a reporting mechanism and they are connected to a coordinator so that this provides direct connections between femtocells. In this scenario, the femtocell has the ability to report any interfering neighboring femtocell with the aid of a coordinator. Moreover, victim femto user at the cell edge can report the interfering femtocell to its serving femtocell or to the macrocell. Results show that the BLER requirements are fulfilled and interference could be reduced through applying the adaptive power control and the proposed reporting scenarios.

Heterogeneous cell architecture in 5G networks has emerged as a leading solution in the field of mobile and wireless communication to meet bandwidth and coverage area requirements. The off-loading of mobile stations (MS) from Macro cell to Small Cells (Micro, Pico, Femto) increases the overall system throughput. However, heterogeneity in cell architecture comes with drawbacks like increased interference, frequent handovers, and QoS degradation for mobile users. In this paper, we deal with the issue of handover and limited resources in heterogeneous cell architecture. MS opt for Complete, Split or No hand-off based on its velocity. In case of Small cells, we exploit the overlap of coverage area of macro cell and small cells and propose ‘Shared Resource Allocation’, which gets initiated during the handover phase when small cell is unable to support the existing throughput and QoS requirement of MS. The MS then undergoes ‘Split hand-off’ rather than a conventional hand-off and continues to share the resources of both macro cell and small cell throughout its stay in the smaller cell’s coverage area.

Offloading traffic from macrocell to femtocell network is a promising way to cope with the fast-growing mobile data traffic at macrocells. Femtocells have been densely deployed in urban areas. In this paper, we propose an intelligent network selection mechanism to assist users' decision making when simultaneously confronting with macrocell and femtocell network. We consider a two-tier macro-femto heterogenous networks (HetNets): femtocell network provides higher data rate but charges higher price; on the other hand, macrocell network may offer unsatisfied data rate but charges lower price. Our network selection problem is modeled in two different ways: (i) payment minimization subject to a delay tolerance constraint; and (ii) throughput maximization subject to a budget constraint. We present an Integer Linear Program (ILP) solution. An efficient heuristic for provisioning complementary supervisory paths and cycles is also introduced and the solution quality is compared with ILP for different sets of random user light paths and different parameters.

In this paper, we analyze the performance of non- orthogonal multiple access (NOMA) for the down-link transmission of a Base-Band Unit (BBU) pool to multiple Radio Remote Heads (RRH) serving multiple types of cells (e.g., macro, micro, pico, and even femto) in a heterogeneous cloud radio access networks (H-CRAN). Our analytic model is intended for NOMA with imperfect successive interference cancellation (SIC) implementation for the wireless down-link in an H-CRAN. We conduct extensive numerical experiments to investigate the performance of the NOMA with imperfect SIC implementation taking into account power consumption levels at the remote radio head (RRH) of different cell types and front-hauling power. The numerical results reveal an interesting fact that increasing the imperfect SIC factor will degrade the energy efficiency (EE) of multi-cell cellular networks significantly.

Waveform-stable, pulsed laser sources have enabled both time-domain and frequency-domain precision metrology, through real-time measurement of electric-field-driven light-matter interactions on their native femto- and attosecond time scales, and by harnessing the frequency-comb nature of high-repetition-rate pulse trains. Particular interest has been shown in these sources for use in infrared (IR) molecular fingerprinting [1,2], offering increased sensitivity and specificity compared to traditional, thermal-source-based Fourier-transform spectroscopy, for applications such as biomedical spectroscopy or trace-chemical sensing. Here, we present a compact, 50-MHz source of high-power, waveform-stable IR pulses. Driven by a 2μm based fiber chirped pulse amplifier (FCPA), three parallel nonlinear fiber channels are used to cover the spectral range of 1.4 to 20 μm.

Over the last decades, experiments with femto- and attosecond temporal resolution have explored the nonequilibrium physics of matter emerging under excitation with high energies or electromagnetic fields provided by intense laser pulses. At the same time, the sensitivity of ultrafast technology has increased tremendously, thus enabling a complementary development: measurements on individual electrons and even virtual photons on the elementary time scales that are intricately linked to the physics at ultrasmall length scales.

The demand of traffic in cellular network is increasing exponentially, so in order to cope up with the rising demand of traffic cellular operators require deploying new cell sites to serve the purpose. But, to construct and operate macro base station is very costly. So the approach of Heterogeneous Network (HetNet) in Long Term Evolution (LTE) is taken into consideration, where a composition of high power Macro Base Station (MBS) and Small Base Station (SBS) like pico, femto and micro are deployed within the coverage area. Intercell Interference management has become a critical issue for HetNet with respect to cellular mobile systems. HetNet is comprised of macro base station and pico base station, generally macro overrules the transmission of Pico base station, so it can be served as a provision to make macro base station silent for some period of time and small base stations are allowed to transmit known as Almost Blank Subframes (ABSs). Enhanced Inter-Cell Interference Coordination (eICIC) technique is an efficient way of managing intercell interference in heterogeneous network. The main intention of this article is to enhance the network performance with respect to throughput and Energy Efficiency (EE). Another objective is to mitigate the interference. Simulation result shows that Relaxed ABS can attain a remarkable gain in EE of the system and users, but at the same time throughput of the system slightly decreases.

Enhanced inter-cell interference coordination (eICIC) techniques are designed to mitigate cross-tier interference in heterogeneous networks. Another advantage of eICIC is energy saving by the suppression of the data transmission over almost blank subframes (ABS). In this paper, we present the area spectral efficiency and worst-region capacity analysis, and then present an energy efficiency optimization problem with respect to the number of ABS's. The analysis comprises open access networks of macro/pico-cells and closed access networks of macro/femto-cells. We propose an optimization algorithm to evaluate the feasible regions for both open and closed access networks. The results include valuable feasible region comparisons and show energy efficiency gains achieved by the optimal number of ABS's for different network parameters.

Redistribution layer (RDL) first is advantageous to enhance the total yield of fan out wafer level package (FOWLP) and fan out panel level package (FOPLP). The key to success is a cost effective testing to assure reliability of known good RDL prior to KGD attachment. This paper shows a cost effective single-sided open/short testing utilized femto farad capacitance tester. The capacitive test vehicle performed RDL includes fine pitched of line width/line spacing 2um/2um for a glass carrier panel level package. The result shows the throughput advantage than double-sided resistance based open/shot test.

In the last few years, we have witnessed an exponential increase in the popularity of Internet-enabled smart devices. In this era, various smart devices generate a huge amount of data during computing and communication. However, fixed infrastructure, especially in the dense population, have the issues of coverage and connectivity in this environment. But, 5G technology based femtocell emerges as one of the solutions for the aforementioned issues. Hence, in this paper, we investigate the non-orthogonal multiple access (NOMA) transmission with 5G enabled cognitive femtocell to attain higher spectral efficiency and to maximize the sum rate of femto users (FUs) with guaranteed QoS. A paring algorithm between strong and weak users has been proposed to reduce the NOMA interference between different FUs. To achieve higher data rates, the calculation of sum rate for an even/odd number of FUs in a femtocell is also proposed. Numerical results show that the proposed schemes effectively improve the sum rate of the cognitive femtocell under NOMA transmission to minimize the interference.

Smart grid is a next generation electricity network that transmits electricity to end users and enable two way digital communication for providing remote reading and other advanced metering functions. For Smart grid domains to interact with each other, a reliable communication is required. This reliable two-way communication can be achieved with the use of small cells technology (femto, pico, etc), relay, or any of the transmission scheme proposed in 5G systems. With the use of femto cells and relay nodes in the network, the allocation of resources for the purpose of smart grid communication needs to be done efficiently. Power being one of the resource has been studied for its allocation in a femto cell network for Smart grid communication, however, transmission reliability and interference is generally ignored. In this paper, we investigate the problem of power allocation in a Neighborhood Area Network (NAN) with femto cell and relay technology as a communication mechanism. We formulate the problem as a power minimization problem such that the transmission reliability is ensured. Our performance evaluation shows that the average transmit power required for transmission through femto cell is 99% less as compared with cooperative transmission.

Two-tier network is one of the most promising solutions to improve indoor coverage of cellular networks. When macro-tier and femto-tier share frequency spectrum, management of interference as a critical issue, attract much attention from industry and academia. Joint sub-carrier assignment and power control is considered as a way to interference management in orthogonal frequency division multiple access based two-tier networks. In this paper, a joint sub-carrier assignment and power control problem is addressed to maximize femtocells’ total data rate such that the maximum transmit power budget and minimum data rate of users (macro and femto users) are satisfied. This problem is a mixed-integer non-linear programming problem, thus its optimal solution cannot be obtained in polynomial time. So, to tackle this issue, we decompose this problem into two sub-carrier assignment and power control sub-problems. To solve these sub-problems, heuristic algorithms are proposed. The simulation results demonstrate that our proposed algorithms outperform the existing algorithms in terms of femtocells’ total data rate.

With the increasing tendency of dense femtocell deployment, the inter-femtocell interference has become one of the most critical issues that need to be concerned in future cellular networks. In this paper, we propose a novel dynamic base station sleep based resource allocation algorithm to mitigate the interference among femtocells. First, we build an interference map to indicate whether a user is interfered by any femtocell base station (FBS). Then, to reduce the inter-femtocell interference, we design a set of sleep criterions based on the interference map to let certain FBSs to be deactivated, which is proved to be more effective than the existing base station sleep methods. On the basis of the sleep control, we propose a heuristic resource allocation algorithm to get the optimal allocation of subchannel and power, which achieves a remarkable overall performance and outperforms other methods, such as the random assignment method and the self-organizing method. Moreover, the proposed algorithm is especially suitable for the scenario with dense femtocell deployment.

High quality single-crystal GaSe nanoribbons (NRs) are fabricated and demonstrated as waveguides with good performance. By taking advantage of the strong confinement and long interaction length of the waveguiding approach, significantly enhanced nonlinear light–matter interaction is observed in GaSe NRs. Based on transverse SH generation, a single GaSe NR-configured optical auto-correlator is constructed for ultrashort pulse characterization. Because of the large second-order nonlinear susceptibility, high sensitivity with femto-joule-level pulse energy that has higher sensitivity than those reported before is demonstrated.

In heterogeneous network (Het-Net) deployment, when multiple low-power node base stations (i.e., relay, pico, and femto) are deployed outdoor and indoor in the same frequency across macro coverage, the geographical coverage overlap can cause unbalanced cost resource allocation and severe co-channel interference. A scheme of multi-domain cooperative cost resource management in Het-Net is proposed for the mixed outdoor + indoor heterogeneous scenario, which can effectively allocate the load resource and power resource across domains. By the genetic algorithm, the optimal solution for minimizing the network cost resource can be obtained. In numerical evaluation, the cost resource usage in proposed scheme is better than that in the traditional intra-domain scheme.

We demonstrate the sub-cycle optical field emission of electron wave packets with bunch charges up to 12 femtoCoulombs from a tungsten nanotip illuminated by intense THz pulses.

Device to device (D2D) communication technology is widely considered in 5G for providing higher data rates and increase network capacity. The performance benefits of D2D communication are best achieved if it takes place in shared mode in which it reuses the spectrum being utilized by conventional cellular users. This induces significant challenges in allocating resources because of severe interference among D2D and cellular users. Moreover, centralized resource allocation techniques proposed in literature for D2D users can no longer be practical in dense heterogeneous networks considered for 5G. In this paper, we present a distributed learning based spectrum allocation scheme in which D2D users learn the environment and autonomously select spectrum resources to maximize their Throughput and Spectral Efficiency (SE) while caus- ing minimum interference to the cellular users. We have employed distributed learning in a stochastic geometry based realistic network. Our evaluation results show that the employed learning scheme enables users to achieve high Throughput and Spectral Efficiency while meeting QoS requirements of macro and femto tier.

Recently, significant researches have been devoted to develop some remedial solutions to cell-edge effect issues such as inter-cell interference coordination and coordinated multipoint transmission. However, they were unable to completely remove the cell-boundary effect and led to increased complexity and overhead. In order to realize the gain of user virtualization, this paper proposes a tractable virtual user equipment (UE) forming procedure in which a set of qualified UEs is selected to serve as small cells. Specifically, the UE group completes discovery and connection among each other in a self-organized manner, and the donor femto transmission point (FTP) manages the data transmission and handover of the virtual UE group cooperatively. Meanwhile, the context information from both users and networks is utilized to locally optimize the composition of the virtual UE group, which adapts to each user’s environment and quality of service (QoS) requirements. Simulation results illustrate that the virtual UE design achieves an increase of maximum 65% for success probability under high spectral efficiency request compared to the LTE system and efficiently improves average user throughput.

The inter-cell interference coordination techniques which include frequency reuse and Dynamic Channel Allocation (DCA) play a vital role in improving the spectrum efficiency. The techniques of frequency reuse are very sophisticated. Depending on the traffic demand, channels allocated to each cell is varied in DCA. In OFDM based cellular systems, the channel information and interference signals can be measured easily whose knowledge is essential for DCA. Hence, in OFDM systems, DCA can improve the spectral efficiency to a great extent. The next generation cellular systems would incorporate small cell (Micro, Pico and Femto) base stations for extensive frequency reuse and spectrum utility. They would also include millimeter wave (mmWave) for communication i.e. 5G cellular networks. DCA techniques in such a HetNet would improve the efficiency to a great extent. With the development of Software Defined Mobile Networking (SDMN), the protocol-specific features of mobile networks for various radio access technologies can be carried out with software improving the functionality of network. Thus, the implementation of DCA techniques becomes less complex. In this paper, DCA in small cells with respect to three cases namely spatial, temporal and spatio-temporal allocation is proposed. The problem formulated for DCA is solved using integer linear programming (ILP) technique and the solution is an effective prediction based model to optimize the channel allocation problem. Simulation results show the performance for various number of available resources and number of cells for allocation.

In heterogeneous networks, a user equipment (UE) can directly communicate with the macro base station (BS) or a small, low-power pico or femto BS. Alternatively, it can indirectly communicate with the macro BS through one or more intermediate device (UE) or a relay-station that uses the over-the-air backhaul to the macro BS. Due to the highly dynamic and uncertain nature of wireless communication, it is essential for a UE to choose an optimal communication mode and a neighbor to which it connects, e.g., a macro/small BS in the direct communication mode or a nearby relay/device in the indirect communication mode. In this paper, we apply an effective reinforcement learning method, called multi-armed bandit (MAB), to shed light on this problem. Especially, we apply MAB supported by the Thompson sampling theorem to pick an optimal arm—a neighbor that determines the communication mode and resulting performance, while effectively dealing with the exploration-exploitation dilemma in MAB. In a simulation study undertaken in Matlab, we compare the performance of the proposed approach to several baselines representing the current state of the art. Our approach enhances the throughput normalized to the optimal throughput by approximately 8-97% compared to several baselines representing the state of the art. Further, it improves the throughput by up to 15% compared to the best performing baseline [1], [2].

5G networks provide an interesting research challenge with the widespread use of Internet and the scale of mobile data traffic that grows explosively. The emerging need to bring data closer to users and minimizing the traffic off the macrocell base station (MBS) introduces the use of small, low power small base stations (SBS) with small cache space (termed femto caches, or more popularly, helpers). Helpers have low rate backhaul but high storage capacity that can be used to cache most popular files. When users request files that do not exist in helpers, then the files will be transmitted from MBS to helpers. The availability of the data in local cache can significantly improve performance since it overcomes the constraints in wireless environment. This leads to improving network throughput and reducing end-toend and backhaul delay. Caching the optimal contents into femto caches proactively depending on the knowledge about files popularity distribution is not enoughthe since Internet users have different context and different preferences. In this paper, we propose an algorithm for proactive caching based on fuzzy softset (FSS) approach for decision making. The algorithm decides which files to cache and where to cache them depending on file popularity distribution, file to user preferences, file clustering, and helpers to connected users clustering. The simulation results show significant overall cache hit rate increase with the increasing number of user requests. The algorithm can effectively improve system performance by reducing the delay for downloading the files and proactively cache those files which will improve user satisfaction.

5G will require a number of Key Technological Components to meet its very ambitious goals, including Heterogeneous Networks a nd Small Cells. The Dense Deployme nt of Small Cell Base Stations (SBSs) will play a major role as they can be installed in a more targeted manner to relieve traffic in hot spot areas, increase coverage, and spectral efficiency. However, the current deployment of the SBS is static (examples include Femto, Pico, and Nano cells), normally deployed on demand around hotspots. In the scenario of unpredictable crowd movement, these static deployment of small cell can be inefficient with high CAPEX and OPEX. This paper focuses on the scenario where UE-based Virtual Small Cell Base Stations (UE-VBSs) can be dynamically selected among UEs to deal effectively with the non-stationary, non-uniform distribution of mobile traffic with respect to time and space domain. To implement this concept, we propose an efficient clustering technique (Affinity Propagation Clustering) to select the best set of UE-VBSs to supplement an overlay loaded SBS. Simulative evaluation highlights salient features of the technique, as well as its limitations with regard to scalability. Further, we discuss the modification of the algorithm according to our objec tive sc enario focusing on red ucing the message passing procedure to and from only a number of eligible UE-VBSs using the power received by a UE from the eligible UE-VBSs as a parameter. The algorithm is implemented and evaluated in MATLAB and, also validated using NS3 simulator. 1104 1109

Most of users in heterogeneous networks (HetNets) associate to macro base stations (BSs) due to their high transmission power while small cell BSs are underutilized. Current research has addressed this load balancing problem based on biased user association where all small cell BSs that belong to the same tier, e.g femto or pico BSs are assigned a static biasing value in order to increase their coverage area. This work utilises particle swarm optimisation to assign each small cell BS a certain biasing value with the objective of maximising the achievable throughput and controlling the load per-BS. Simulation results show that the proposed PSO approach achieves better performance in terms of the achievable throughput. In addition, the proposed approach is ableto provide fairness among users by controlling the load per-BS.

In this paper, we address the problem of channel allocation for femtocells that share the use of regular macrocell spectrum. The femto basestation (FBS) scheduling problem is formulated in the form of restless multiarmed bandit (RMAB) framework. Our goal is to choose the arms/channels that maximize the total expected discounted reward over infinite horizon while minimizing the induced interference due to channel sharing with macrocell. Without direct observation of true channel state, we use the available macrocell user feedback known as channel quality indicator (CQI). In general, the RMAB problem is P-SPACE hard. We propose a heuristic low complexity indexing policy referred as approximated Whittle index to rank available channels for FBS. Although finding a closed form channel ranking solution typically involve dynamic programming, we show that based on the partial channel information within CQI, there exists a closed form for the channel index. Moreover, we demonstrate the performance advantage of the proposed indexing policy over a myopic policy.

This paper proposes a self-optimized coverage coordination scheme for a macro/femto network, where each Femtocell Base Station (FBS) divides the transmit power among its users based on the bargaining game. The downlink connection between each FBS and one of its femtocell user equipments takes the role of players. The main goal is to design a coalition formation game in which players cooperate with each other to mitigate the co-tier interference. Deploying the interference alignment mechanism, the null shaping constraints are enforced in the design of transmit covariance matrices to enable the co-tier interference mitigation among links. Simulation results show that a significantly improvement of the users' coverage probability and the data transmission rate is achieved even at the low signal-to-noise ratio regime when compared to the conventional interference alignment and the non-cooperative schemes.

Transmission power control methods appear to be the most conventional practices to enhance system capacity and to mitigate the effects of cross-tier and co-tier interference of small cell networks (e.g. femtocell networks). Additionally, full duplex communications appear to be a novel solution for the increase in the spectrum efficiency and the reduction in latency for mobile stations. In this paper, we propose an algorithmic game method for power control of a femto-relay network that implements the full duplex communication between its nodes and mobile stations. Our proposed approach shows that the corresponding game sustains a Nash equilibrium by a small number of iterations that is near to the number of femto-relays in the network in the presence of self-interference. Moreover, we show the effects of self-interference on the overall system power.

We review our recent achievements in various energy-efficient nanophotonic devices based on photonic crystals. Strong light confinement of photonic crystals enables large enhancement of light-matter interactions and ultrasmall capacitance for OE/EO conversion devices. Owing to these two features, we have demonstrated that the energy consumption of photonic devices can be reduced down to fJ/bit or less. This achievement may suggest energy-efficient optical link in a processor chip, and even opportunity for ultrasmall latency optoelectronic computations.