Enhanced handover mechanism in long term evolution (LTE) networks

Over the past decade, there have been great interests in cellular and fixed radio access technologies for providing mobile, nomadic and fixed telecommunication services. The fast pace development of this technology and the challenges it presents due to the increasing number of user equipments and the demand to have the service on-the-go, have presented new challenges on base stations capability and the handover (HO) techniques. To address these challenges intensive researches are being carried out to define algorithms that can handle the HO decisions based on user equipment (UE) requirements and quality of service (QoS) expectations. This paper investigates the improvement steps for HO mechanisms in long term evolution (LTE) system which is being formally submitted as a candidate 4G system. LTE network is expected to support mobility with speeds of up to 500 km/h, when the HO will then become more frequent and fast. The basis of the approach is to reduce the number of unnecessary HOs. The strengths and weaknesses for each algorithm are discussed, and conclusions are subsequently made

On fractional and semi-soft handover in long term evolution(LTE) networks

The fast pace of development of telecommunications technology and the challenges presented with the increasing number of users for any service, anywhere, anytime, access creates new problems with on the base stations capability and the handover/handoff (HO) techniques. To face these challenges much research have been made to come out with algorithms that can handle handover of user equipment (UE) while maintaining their respective quality of service (QoS). In this paper a hybrid HO algorithms called semi-soft handover (SSHO) and fractional soft handover (FSHO) in long term evolution (LTE) system are studied. The outage probability, the main metric to evaluate handover, is compared for different handover techniques

Data Centre Infrastructure: Power Efficiency and Protection

The rapid expansion of e-commerce necessitates expanding the capacity and dependability of data centres in order to provide services with the proper level of quality. A green technology that has a lot of potentials to reduce CO2 emissions is optimization data centre design. However, a large data centre required a large amount of electricity because the capacity of the racks is higher, which required more potent cooling systems, power supplies, protection and security. These will increase the cost of the data centre and render it unusable for services. In this chapter, we provide a design for a tire-four data centre that will be situated in Cyberjaya, one of Malaysia’s best locations. This design’s primary goal is to offer highly functional and high-quality e-commerce services, particularly food delivery. Each component of the data centre has been carefully developed to deliver a range of services, including the administration of IT infrastructure, co-location, cooling system and protection. Additionally, advice and support have been given to guarantee that the suggested design outperforms competing data centres in terms of dependability, power efficiency and storage capacity. The analysis, synthesis, and evaluation of each element of the proposed data centre will be considered in this chapter

Data Centre Infrastructure: Design and Performance

The tremendous growth of e-commerce requires an increase in the data centre capacity and reliability for appropriate quality of services. Optimisation of data centre design is considered to be within a green technology that shows great promise to decrease CO2 emission. However, a huge data centre requires huge power consumption due to higher capacity of racks that lead to more powerful cooling systems, power supply, protection and security. These make the data centre costly and not feasible for services. In this chapter, we will provide a tire 4 data centre design to be located in the optimal location of Malaysia, in Cyberjaya. The main purpose of this design is to provide e-commerce services, especially food delivery, with high quality of services and feasibility. All data centre components have been well designed to provide various services which include top-level security, colocation system, reliable data management and IT infrastructure management. Moreover, recommendation and justification have been provided to ensure that the proposed design outperforms compared to other data centres in terms of reliability, power effeminacy and storage capacity. In conclusion, analysing, synthesising and evaluating each component of the proposed data centre will be summarised

A novel cell-selection optimization handover for long-term evolution (LTE) macrocellusing fuzzy TOPSIS

To satisfy the demand for higher data rate while maintaining the quality of service, a dense long-term evolution (LTE) cells environment is required. This imposes a big challenge to the network when it comes to performing handover (HO). Cell selection has an important influence on network performance, to achieve seamless handover. Although a successful handover is accomplished, it might be to a wrong cell when the selected cell is not an optimal one in terms of signal quality and bandwidth. This may cause significant interference with other cells, handover failure (HOF), or handover ping-pong (HOPP), consequently degrading the cell throughput. To address this issue, we propose a multiple-criteria decision-making method. In this method, we use an integrated fuzzy technique for order preference by using similarity to ideal solution (TOPSIS) on S-criterion, availability of resource blocks (RBs), and uplink signal-to-interference-plus-noise ratio. The conventional cell selection in LTE is based on S-criterion, which is inadequate since it only relies on downlink signal quality. A novel method called fuzzy multiple-criteria cell selection (FMCCS) is proposed in this paper. FMCCS considers RBs utilization and user equipment uplink condition in addition to S-criterion. System analysis demonstrates that FMCCS managed to reduce handover ping-pong and handover failure significantly. This improvement stems from the highly reliable cell-selection technique that leads to increased throughput of the cell with a successful handover. The simulation results show that FMCCS outperforms the conventional and cell selection scheme (CSS) methods

Evaluation of 5G and Fixed-Satellite Service Earth Station (FSS-ES) downlink interference based on Artificial Neural Network Learning Models (ANN-LMS)

Fifth-generation (5G) networks have been deployed alongside fourth-generation networks in high-traffic areas. The most recent 5G mobile communication access technology includes mmWave and sub-6 GHz C-bands. However, 5G signals possibly interfere with existing radio systems because they are using adjacent and co-channel frequencies. Therefore, the minimisation of the interference of 5G with other signals already deployed for other services, such as fixed-satellite service Earth stations (FSS-Ess), is urgently needed. The novelty of this paper is that it addresses issues using measurements from 5G base stations (5G-BS) and FSS-ES, simulation analysis, and prediction modelling based on artificial neural network learning models (ANN-LMs). The ANN-LMs models are used to classify interference events into two classes, namely, adjacent and co-channel interference. In particular, ANN-LMs incorporating the radial basis function neural network (RBFNN) and general regression neural network (GRNN) are implemented. Numerical results considering real measurements carried out in Malaysia show that RBFNN evidences better accuracy with respect to its GRNN counterpart. The outcomes of this work can be exploited in the future as a baseline for coexistence and/or mitigation techniques.Agencia Estatal de Investigación | Ref. PID2020-115323RB-C33Agencia Estatal de Investigación | Ref. PID2020-113240RB-I0

An Implementation of Indoor Visible Light Communication System Using Simulink

The implementation of indoor visible light communication (VLC) systems using a direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) scheme is investigated in this paper. The main contribution of this work is to analyze the VLC system using Simulink design. Simulink design uses blocks that are much easy and deliver optimized results for hardware implementation. The system analysis comprises, first the effect of signal scaling and biasing operation on the peak to average power ratio (PAPR) which is a major drawback in OFDM based VLC system. Second the use of the channel estimation for the received signal. Simulation results show that the PAPR is significantly reduced by employing the signal scaling combined with biasing operation. Furthermore, the bit error rate (BER) can be reduced by utilizing channel estimation algorithms such as minimum mean square error (MMSE) and least squares (LS)

A Novel Approach for PAPR Reduction in OFDM-Based Visible Light Communications

One of the best techniques to increase data rate and improve spectral efficiency for indoor visible light communication (VLC) is by employing Orthogonal Frequency Division Multiplexing (OFDM). To efficiently exploit the optical bandwidth, we propose a novel transmission approach for OFDM based VLC that increases the bandwidth efficiency by 50% compared to conventional optical OFDM systems. Unlike existing approaches of OFDM-based VLC systems, the real and positive signal is obtained without the Hermitian symmetry and signal clipping. Through simulation results, the proposed scheme shows significant peak-to-average power ratio (PAPR) reduction can be achieved, namely up to 10dB compared to the conventional asymmetrically clipped optical OFDM (ACO-OFDM) and 5dB compared to DC biased optical OFDM (DCO-OFDM) at complementary cumulative distribution function (CCDF) of 10-1 with acceptable bit-error-rate (BER) performance. A Novel Approach for PAPR Reduction in OFDM-Based Visible Light Communications | Request PDF. Available from: https://www.researchgate.net/publication/315637822_A_Novel_Approach_for_PAPR_Reduction_in_OFDM-Based_Visible_Light_Communications [accessed Jan 11 2018]

Performance analysis of DCO-OFDM in VLC system

The performance of indoor visible light communication (VLC) systems using a direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) scheme is investigated in this paper. The impact of nonlinearity of Light Emitting Diode (LED) and its beam angle on the VLC system performance is studied. We later analyze the effect of modulation order, number of subcarriers, signal scaling and biasing operation on the peak to average power ratio (PAPR) which is a major issue in OFDM based VLC system. Simulation results show that the bit error rate (BER) decreases as the degree of nonlinearity increases and a better BER can be achieved as the LED behavior approaches linear model. In addition, it is shown that reducing the QAM order or increasing the number of subcarriers may reduce the effect of the LED nonlinearity, thus improving the BER performance of the VLC system. Moreover, it is demonstrated that PAPR is higher for a large number of subcarriers and modulation order. Finally, the PAPR of the visible light OFDM system can significantly be reduced by employing the signal scaling combined with biasing operation

On performance analysis of LS and MMSE for channel estimation in VLC systems

Channel estimation is a key feature for wireless optical communication systems. This paper presents an evaluation of channel estimation techniques for indoor visible light communication (VLC) systems using a direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) scheme. The VLC system can simultaneously provide illumination and wireless communication at a high data rate. However, the coverage area is limited and the distance is about 3 m. In this paper, performance analysis of two channel estimation methods is presented, one using the least squares (LS) algorithm and the other the minimum mean square error (MMSE) algorithm, to estimate channel response by applying them to various M-QAM modulations. The performance of these two methods is compared by mathematical analysis and by simulation by measuring bit error rate (BER) and mean square error (MSE) versus signal-to-noise ratio (SNR). The results shown that, at higher SNR, the MMSE algorithm outperforms the LS for both BER and MSE