A review of performance and energy aware improvement methods for future green cloud computing

With the advent of increased use of computers and computing power, state of the art of cloud computing has become imperative in the present-day global scenario. It has managed to remove the constraints in many organizations in terms of physical internetworking devices and human resources, leaving room for better growth of many organizations. With all these benefits, cloud computing is still facing a number of impediments in terms of energy consumption within data centers and performance degradation to end users. This has led many industries and researchers to find feasible solutions to the current problems. In the context of realizing the problems faced by cloud data centers and end users, this paper presents a summary of the work done, experimentation setup and the need for a greener cloud computing technique/algorithm which satisfies minimum energy consumption, minimum carbon emission and maximum quality of service

Hybrid heuristic algorithm for better energy optimization and resource utilization in cloud computing

Energy-efficient execution of the scientific workflow is a challenging task in cloud computing that demands high-performance computing to process growing datasets. Due to the interdependency of tasks in the scientific workflow applications, energy-efficient resource allocation is vital for large-scale applications running on heterogeneous physical machines. Thus, this paper proposes a Hybrid Heuristic algorithm based Energy-efficient cloud Computing service (HH-ECO) that offers a significant solution for resource allocation, task scheduling, and optimization of scientific workflows. To ensure the energy-efficient execution, the HH-ECO focuses on executing non-dominant workflow tasks through adaptive mutation and energy-aware migration strategy. HH-ECO adopts the Chaotic based Particle Swarm Optimization (C-PSO) principle to optimize the resource allocation, task scheduling, and resource migration by generating the global best plans without local convergence. C-PSO with adaptive mutation avoids the deterioration of global optima while finding the best host to place the virtual machine and ensures an appropriate resource allocation plan. By considering the workflow task precedence relationships during C-PSO based task scheduling, the novel hybrid heuristic method efficiently solves the multi-objective combinatorial optimization problem without dominance among the workflow tasks. The Cloudsim based simulation study delivers superior results compared to the existing methods such as the Hybrid Heuristic Workflow Scheduling algorithm (HHWS) and Distributed Dynamic VM Management (DDVM). The proposed approach significantly improves the optimal makespan to 38.27% and energy conservation to 38.06% compared to the existing methods

An investigation into the application of companding to wireless OFDM systems

The everyday increase in the demand for high speed mobile multimedia communications requires transmission techniques that are robust to channel hostilities and yet providing higher data rates. Orthogonal Frequency Division Multiplexing (OFDM) promises to be a key modulation technique that caters to these requirements; however, it suffers from a very high peak to average power ratio (PAPR) resulting in other associated problems. This thesis provides a review of various PAPR reduction techniques available in the published literature and then presents a novel approach to PAPR using the less explored technique of companding. For the first time, a complete evaluation and quantification of PAPR and BER for companding in relation to OFDM is carried out in terms of different companding profiles, number of carriers and type of modulation employed. In addition, a new parameter related to the companding profile called the peak ratio (PR) is defined. It is demonstrated that PR can reduce further the PAPR of OFDM signals and further improve the BER performance. Typically, an OFDM signal companded with a PR =2 has shown a channel EtlNo gain of 5.7 dB for a BER of 0.0001, and a PAPR reduction of 5.88 dB in relation to an uncompanded OFDM signal. A thorough investigation of High Power Amplifier (HPA) nonlinearity on companded OFDM is also carried out in terms of evaluating and quantifying the BER performance and signal splatter as a function of the OFDM carriers, modulation, companding and HPA nonlinearity parameters. The most significant result is that application of companding to OFDM is demonstrated to provide robustness of improved PAPR and BER when nonlinear amplifier characteristics are present. Typically, while a 64-QAM OFDM signal under the influence of a nonlinear HPA cannot produce a BER lower than 0.001 for any value of channel EtlNo greater than 20 dB, the companded OFDM signal produces a BER of about 0.00001 for a channel EtlNo of around 19 dB. The companding technique has also been compared for performance in terms of PAPR reduction and BER with the more popular PAPR reduction techniques of clipping, peak-windowing, phasing and selected mapping. It is shown that companding surpasses these techniques for certain particular companding profiles. Typically, companding with a PR =1'.4 results in an improvement of about 2.5 dB over general OFDM and a'n improvement of about 12 dB over clipped OFDM with a clipping ratio of 1.4. The novel approach of combining companding with these popular PAPR reduction techniques has also been investigated for the first time with the results demonstrating a further dramatic improvement in PAPR reduction and BER performance for OFDM transmissions. Further, combining a particular phasing technique with companding can reduce the PAPR to as low as 0.5 dB. This research work has also resulted in some further new insights. Firstly, for multi-tone signals, standard phasing techniques can be further refined for improvement of PAPR; secondly a modified phasing scheme for QPSK is possible to reduce further PAPR, though like other PAPR reduction techniques, requires additional overhead to be transmitted; and thirdly alternative means of simple encoding techniques are possible to improve upon present implementations of selected mapping PAPR reduction methods. The results of this thesis therefore have significant implications for the practical applications of broadband OFDM transmissions in terms of improved PAPR and BER performance.EThOS - Electronic Theses Online ServiceGBUnited Kingdo