23,010 research outputs found
Approximation Algorithms for Energy Minimization in Cloud Service Allocation under Reliability Constraints
We consider allocation problems that arise in the context of service
allocation in Clouds. More specifically, we assume on the one part that each
computing resource is associated to a capacity constraint, that can be chosen
using Dynamic Voltage and Frequency Scaling (DVFS) method, and to a probability
of failure. On the other hand, we assume that the service runs as a set of
independent instances of identical Virtual Machines. Moreover, there exists a
Service Level Agreement (SLA) between the Cloud provider and the client that
can be expressed as follows: the client comes with a minimal number of service
instances which must be alive at the end of the day, and the Cloud provider
offers a list of pairs (price,compensation), this compensation being paid by
the Cloud provider if it fails to keep alive the required number of services.
On the Cloud provider side, each pair corresponds actually to a guaranteed
success probability of fulfilling the constraint on the minimal number of
instances. In this context, given a minimal number of instances and a
probability of success, the question for the Cloud provider is to find the
number of necessary resources, their clock frequency and an allocation of the
instances (possibly using replication) onto machines. This solution should
satisfy all types of constraints during a given time period while minimizing
the energy consumption of used resources. We consider two energy consumption
models based on DVFS techniques, where the clock frequency of physical
resources can be changed. For each allocation problem and each energy model, we
prove deterministic approximation ratios on the consumed energy for algorithms
that provide guaranteed probability failures, as well as an efficient
heuristic, whose energy ratio is not guaranteed
Adaptive Electricity Scheduling in Microgrids
Microgrid (MG) is a promising component for future smart grid (SG)
deployment. The balance of supply and demand of electric energy is one of the
most important requirements of MG management. In this paper, we present a novel
framework for smart energy management based on the concept of
quality-of-service in electricity (QoSE). Specifically, the resident
electricity demand is classified into basic usage and quality usage. The basic
usage is always guaranteed by the MG, while the quality usage is controlled
based on the MG state. The microgrid control center (MGCC) aims to minimize the
MG operation cost and maintain the outage probability of quality usage, i.e.,
QoSE, below a target value, by scheduling electricity among renewable energy
resources, energy storage systems, and macrogrid. The problem is formulated as
a constrained stochastic programming problem. The Lyapunov optimization
technique is then applied to derive an adaptive electricity scheduling
algorithm by introducing the QoSE virtual queues and energy storage virtual
queues. The proposed algorithm is an online algorithm since it does not require
any statistics and future knowledge of the electricity supply, demand and price
processes. We derive several "hard" performance bounds for the proposed
algorithm, and evaluate its performance with trace-driven simulations. The
simulation results demonstrate the efficacy of the proposed electricity
scheduling algorithm.Comment: 12 pages, extended technical repor
On Power and Load Coupling in Cellular Networks for Energy Optimization
We consider the problem of minimization of sum transmission energy in
cellular networks where coupling occurs between cells due to mutual
interference. The coupling relation is characterized by the
signal-to-interference-and-noise-ratio (SINR) coupling model. Both cell load
and transmission power, where cell load measures the average level of resource
usage in the cell, interact via the coupling model. The coupling is implicitly
characterized with load and power as the variables of interest using two
equivalent equations, namely, non-linear load coupling equation (NLCE) and
non-linear power coupling equation (NPCE), respectively. By analyzing the NLCE
and NPCE, we prove that operating at full load is optimal in minimizing sum
energy, and provide an iterative power adjustment algorithm to obtain the
corresponding optimal power solution with guaranteed convergence, where in each
iteration a standard bisection search is employed. To obtain the algorithmic
result, we use the properties of the so-called standard interference function;
the proof is non-standard because the NPCE cannot even be expressed as a
closed-form expression with power as the implicit variable of interest. We
present numerical results illustrating the theoretical findings for a real-life
and large-scale cellular network, showing the advantage of our solution
compared to the conventional solution of deploying uniform power for base
stations.Comment: Accepted for publication in IEEE Transactions on Wireless
Communication
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