Towards energy efficiency in virtual topology design of elastic optical networks

Elastic optical networks offer a reliable platform for achieving energy efficiency by supporting extensive optical grooming of variable‐rate data traffic along with the traditional electrical data aggregation methods. The procedure of routing and spectrum allocation in a topology of nodes has explicit effect to the amount of consumed power. A new energy‐efficient method for designing the virtual topology in IP‐over‐elastic networks is introduced and evaluated. It is concluded that it consumes less power under different elastic transponder types, it designs the virtual topology using fewer transponders, and finally, there is a slight increase in the number of end‐to‐end lightpath hops. The proposed method is characterized by high performance and low lightpath establishment complexity. Therefore, it is suitable for a broad range of network configurations and transponder types.     

基于约束路由的绿色虚拟拓扑设计算法

摘 要：针对Internet核心网日益严重的能耗问题,建立了绿色虚拟拓扑设计(GVTD)问题的形式化模型,通过业务汇聚、按需配置网络资源、动态虚拟拓扑设计和多粒度睡眠机制降低网络能耗。提出了一种基于约束路由的启发式算法——CBR-GVTD算法,利用单跳路由和多跳路由相结合的方法构建网络虚拟拓扑,并通过基于约束的路由实现网络功耗与路由性能的折衷。模拟结果表明,CBR-GVTD算法可在接口平均利用率为80%~90%和最大路由跳数不超过5的条件下,最多可降低62%~90%的网络功耗     

An energy‐efficient algorithm based on sleep‐scheduling in IP backbone networks

This paper relates to the problem of energy conservation in Internet backbone networks. We propose a new Distributed Green Algorithm based on Sleep‐scheduling (DGAS) to switch off some network links and nodes resulting in less energy consumption. Our solution does not depend on any centralized controller and uses a link‐state protocol like Open Shortest Path First to share required information. In addition, DGAS does not require any knowledge of traffic matrix and switches off network nodes and links in 2 phases. In the first phase, some core nodes are switched off on the basis of their usage in network paths. In the second phase, DGAS starts with a minimal topology on the basis of resulted topology from the first phase and adds some links to it to minimize network paths length. Results, obtained by several real network scenarios, show that DGAS can switch off up to 27% of core nodes and up to 80% of links compared to the maximum number of switchable links.     

Energy‐aware virtual multi‐input‐multi‐output‐based routing for wireless ad hoc networks

Virtual multi‐input‐multi‐output (vMIMO) technology is becoming a promising way to improve the energy efficiency of wireless networks. Previous research always builds up the vMIMO‐based routing on the fixed structure such as clusters, and the MIMO mode is omitted in most cases. So, they cannot fully explore the advantage of vMIMO in routing. In this paper, we study a general routing scheme in which no fixed structure is required, and any communication mode of vMIMO is allowed for sake of the energy efficiency. We define two vMIMO‐based routing problems aiming to energy‐minimization and lifetime‐optimization. The first problem can be solved by our distributed energy‐minimum vMIMO‐based algorithm. The algorithm constructs the virtual cooperative graph, and applies the shortest path method on the virtual cooperative graph to solve this problem. The second problem is non‐deterministic polynomial‐time hard, and we design the distributed lifetime‐oriented vMIMO‐based algorithm, which is based on the modified Bellman‐Ford method. It can reach approximation ratio of four. The simulations show that our algorithms can work well in many situations. For example, distributed lifetime‐oriented vMIMO‐based algorithm can prolong the lifetime about 20.2% in dense topologies compared with the cooperative routing algorithm on average. Copyright © 2015 John Wiley & Sons, Ltd.     

An adaptive energy‐efficient framework for time‐constrained optical backbone networks

Power management has emerged as a challenge of paramount importance having strong social and financial impact in the community. The rapid growth of information and communication technologies made backbone networks a serious energy consumer. Concurrently, backbone networking is deemed as one of the most promising areas to apply energy efficient frameworks. One of the most popular energy efficient techniques, in the context of backbone networks, is to intentionally switch off nodes and links that are monitored underutilized. Having in mind that optical technology has thoroughly dominated modern backbone networks, the function of switching off techniques entails fast operation and rigorous decision‐making because of the tremendous speed of the underlying optical media. This paper addresses this challenge by introducing a novel, adaptive, and efficient power management scheme for large‐scale backbone networks. The proposed framework exploits traffic patterns and dynamics in order to effectively switch off the set of network entities in a periodic fashion. An adaptive decision‐making algorithm is presented to maximize the network energy gains with respect to time constraints as well as QoS guarantees. The conducted simulation results reveal considerable improvements when applying the proposed framework compared with other inflexible energy efficient schemes. Copyright © 2015 John Wiley & Sons, Ltd.     

Toward energy‐proportional Internet core networks: an energy‐minimized routing and virtual topology design for Internet protocol layer

With the exponential growth of Internet traffic, the energy consumption issue of core networks is increasingly becoming critical. Today's core networks are highly underutilized most of the time because of the over‐provisioning and redundancy dimensioning, which results in severe energy inefficiency. In previous work, many non‐deterministic polynomial‐time hard mathematics formulation models have been proposed to minimize the energy consumption of core networks. However, effective heuristics are needed to solve these models in medium/large‐size networks. This work studies the energy‐minimized routing and virtual topology design problem of the power‐hungry Internet protocol (IP) layer in core networks, aiming to achieve an energy‐proportional IP layer by exploiting the variation of traffic with hours to reconfigure virtual topology and reroute traffic. We formulate energy‐minimized routing and virtual topology design as an Integer linear programming problem and propose a LR algorithm, a heuristic based on the Lagrangian relaxation, to solve this problem in a polynomial‐time. The simulation results indicate that the LR algorithm outperforms the best previous algorithm and can achieve a near energy‐proportional IP layer with significant power saving. Furthermore, a detailed analysis of simulation results is conducted, which suggests a design principle of network equipment to facilitate the power saving. Copyright © 2013 John Wiley & Sons, Ltd.     

Energy efficiency of virtual multi‐input,multi‐output based on sensor selection in wireless sensor networks

In this paper, a weighted node selection technique in wireless sensor networks is proposed. It is an energy‐efficient cooperative technique where a selected number of sensors at the transmitting end are connected with a selected number of sensors at the receiving end to form a virtual multi‐input multi‐output. The proposed technique is based on a weighted selection function that combines geographical location, inter‐sensor distance in a cluster, channel estimate energy, power circuit, channel loss, mobility factor, and residual energy of each sensor. The weight of each of these parameters in the selection function depends on the degree that this parameter affects the energy consumption. Then, the cluster head selects the sensors with better selection parameters that reduce the overall energy consumption. The numerical results show that the proposed weighted node selection technique achieves a significant improvement in the energy consumption, delay, and network lifetime than the conventional techniques with and without the selected number of sensors. Its improvement reaches 15% in the energy consumption that leads to an increase in the network lifetime by four times the network lifetime of other techniques. Copyright © 2012 John Wiley & Sons, Ltd.     

Energy efficient virtual network embedding for federated software‐defined networks

In this paper, we focus on energy efficient virtual network embedding in federated (multidomain) software‐defined networks (SDNs). We first formulate an optimization problem as an integer linear program (ILP) that minimizes the energy consumption of the network links, while at the same time adhering to the bandwidth and CPU requirements of the virtual network requests. We then propose a polynomial‐time heuristic algorithm, which consists of three stages. In the first stage, the top SDN controller decides on whether to partition the virtual network request into smaller subrequests and give subrequests to multiple domains or give the enitre virtual network request to a single domain, while in the second stage, each SDN controller implements virtual network embedding in its own domain. Finally, in the third stage, the algorithm performs interdomain routing if partitioning decision had been made in the first stage. Our simulation results demonstrate that our proposed algorithm yields close performance to the solutions obtained by using the optimization software CPLEX that implements our ILP.     

Implementing virtual platform for global‐scale cyber physical system networks

The need for global‐scale cyber physical system (CPS) is increasing with the evolution of CPS research. A global‐scale CPS requires additional considerations beyond the well‐known CPS requirements, such as security, reliability, and timely delivery, which cannot be easily satisfied when a CPS becomes global scale. Building an entire dedicated network for a global‐scale CPS cannot be a solution, because it requires a large capital outlay in order to be actualized. To overcome these obstacles, we implement a virtual platform named Xebra that includes effective CPS middleware for realizing a global‐scale CPS and isolation techniques based on virtualization. In this paper, we discuss the requirements for realizing global‐scale CPS network, and also, we introduce our implementation as a virtual platform with its performance evaluation. Copyright © 2014 John Wiley & Sons, Ltd.     

An energy‐efficient localized topology control algorithm for wireless ad hoc and sensor networks

Topology control plays an important role in the design of wireless ad hoc and sensor networks and has demonstrated its high capability in constructing networks with desirable characteristics such as sparser connectivity, lower transmission power, and smaller node degree. However, the enforcement of a topology control algorithm in a network may degrade the energy‐draining balancing capability of the network and thus reduce the network operational lifetime. For this reason, it is important to take into account energy efficiency in the design of a topology control algorithm in order to achieve prolonged network lifetime. In this paper, we propose a localized energy‐efficient topology control algorithm for wireless ad hoc and sensor networks with power control capability in network nodes. To achieve prolonged network lifetime, we introduce a concept called energy criticality avoidance and propose an energy criticality avoidance strategy in topology control and energy‐efficient routing. Through theoretical analysis and simulation results, we prove that the proposed topology control algorithm can maintain the global network connectivity with low complexity and can significantly prolong the lifetime of a multi‐hop wireless network as compared with existing topology control algorithms with little additional protocol overhead. Copyright © 2008 John Wiley & Sons, Ltd.     

Efficient location‐based topology control algorithms for wireless ad hoc and sensor networks

Topology control is an efficient strategy for improving the performance of wireless ad hoc and sensor networks by building network topologies with desirable features. In this process, location information of nodes can be used to improve the performance of a topology control algorithm and also ease its operations. Many location‐based topology control algorithms have been proposed. In this paper, we propose two location‐assisted grid‐based topology control (GBP) algorithms. The design objective of our algorithm is to effectively reduce the number of active nodes required to keep global network connectivity. In grid‐based topology control, a network is divided into equally spaced squares (called grids). We accordingly design cross‐sectional topology control algorithm and diagonal topology control algorithm based on different network parameter settings. The key idea is to build near‐minimal connected dominating set for the network at the grid level. Analytical and simulation results demonstrate that our designed algorithms outperform existing work. Furthermore, the diagonal algorithm outperforms the cross‐sectional algorithm. Copyright © 2016 John Wiley & Sons, Ltd.     

Efficient handover measurement technique for small‐cell networks using a virtual cell synchronization signal

A small‐cell network (SCN) constructed by splitting a macro‐cell into numerous small cells using an active antenna array system is studied. A synchronization signal appropriate for the SCN, virtually generated by an eNodeB with 3D beamforming, is proposed for efficient handover in SCNs. The virtual cell synchronization signal (VCSS) carries a macro‐cell ID (MCID) and virtual‐cell ID (VCID) in a hierarchical manner, allowing us to distinguish between an intra‐cell handover (virtual cell handover within a cell without changing the serving eNodeB) and inter‐cell handover (virtual cell handovers across cells while changing the serving eNodeB) in SCNs. Using the signal metrics obtained by the VCSS, an efficient handover measurement technique is proposed which can significantly reduce the processing time and overhead by distinguishing between the intra‐cell/inter‐cell handovers. The performance of the proposed technique is evaluated by simulating two different deployment scenarios of LTE‐based SCN with 3D beamforming. Copyright © 2017 John Wiley & Sons, Ltd.     

A wavelet‐based expert system for digital subscriber line topology identification

This work proposes a new method for automatically identifying topologies of lines with one or more sections in a telephone network. The method is based on the examination of both impulse response and time‐domain reflectometry trace of a line under test. They are analyzed using a method based on the wavelet transform that identifies and extracts features that contain information about the line topology. Those features are interpreted by an expert system composed of three sequential modules that estimate, respectively, the type of line makeup (serial or bridge tap), the lengths of the line sections, and the corresponding cable type, which are the parameters that completely identify the topology according to the assumed model. A thorough comparison with two state‐of‐the‐art methods is also presented using several twisted‐pair copper cables. The results show that the proposed method provides good accuracy with respect to topology identification at low computational cost. Copyright © 2014 John Wiley & Sons, Ltd.     

Perfect match model‐based link assignment to design topology for satellite constellation system

In satellite constellation network, the satellites visible from one satellite are more than communication terminals (CTs) equipped. Each inter‐satellite link (ISL) would occupy one CT on each of two satellites connected by this ISL. Therefore, a fundamental problem considering link assignment is how to assign limited CTs for each satellite to establish ISLs with its visible satellites. Link assignment scheme based on perfect match model (LAS‐PMM) is proposed to make full use of huge bandwidth provided by CT. In LAS‐PMM, the problem of assigning all the CTs of each satellite to establish ISLs is modeled as a perfect matching problem, where a perfect matching is searched over a mixed complete bipartite graph. Simulation results show that LAS‐PMM is better than the regular and greedy LASs, in terms of CT utilization and average node‐to‐node distance. Copyright © 2015 John Wiley & Sons, Ltd.     

Lifetime evaluation in energy‐efficient rectangular ad hoc wireless networks

Ad hoc wireless network nodes are typically battery‐powered, therefore energy limit is one of the critical constraints of ad hoc wireless networks' development. This paper evaluates the network lifetime of a rectangular network model that achieves energy efficiency by optimizing the node radio range based on the geographical adaptive fidelity (GAF) topology management protocol (Proceedings of ACMMobil'01, July 2001; 70–84). We derive the optimal transmission range of nodes and analyze both static and dynamic traffic scenarios in both equal‐grid and adjustable‐grid rectangular GAF models, where the results show that the adjustable‐grid model saves 78.1% energy in comparison with the minimum energy consumption of equal‐grid model. The impact of node density on both equal‐grid and adjustable‐grid models is investigated to achieve grid‐lifetime balance among all grids to optimize the entire network lifetime. The lifetime estimation results show that without node density control the adjustable‐grid model prolongs the entire network lifetime by a factor of 4.2 compared with the equal‐grid model. Furthermore, the adjustable‐grid model with node density control is able to prolong the entire network lifetime by a factor of 6 compared with the equal‐grid model. Copyright © 2010 John Wiley & Sons, Ltd.     

A distributed adaptive landmark clustering algorithm based on mOverlay and learning automata for topology mismatch problem in unstructured peer‐to‐peer networks

Peer‐to‐peer networks are overlay networks that are built on top of communication networks that are called underlay networks. In these networks, peers are unaware of the underlying networks, so the peers choose their neighbors without considering the underlay positions, and therefore, the resultant overlay network may have mismatches with its underlying network, causing redundant end‐to‐end delay. Landmark clustering algorithms, such as mOverlay , are used to solve topology mismatch problem. In the mOverlay algorithm, the overlay network is formed by clusters in which each cluster has a landmark peer. One of the drawbacks of mOverlay is that the selected landmark peer for each cluster is fixed during the operation of the network. Because of the dynamic nature of peer‐to‐peer networks, using a non‐adaptive landmark selection algorithm may not be appropriate. In this paper, an adaptive landmark clustering algorithm obtained from the combination of mOverlay and learning automata is proposed. Learning automata are used to adaptively select appropriate landmark peers for the clusters in such a way that the total communication delay will be minimized. Simulation results have shown that the proposed algorithm outperforms the existing algorithms with respect to communication delay and average round‐trip time between peers within clusters. Copyright © 2015 John Wiley & Sons, Ltd.     

On the eNB‐based energy‐saving cooperation techniques for LTE access networks

Energy efficiency is one of the top priorities for future cellular networks, which could be accomplished by implementing cooperative mechanisms. In this paper, we propose three evolved node B (eNB)‐centric energy‐saving cooperation techniques for long‐term evolution (LTE) systems. These techniques, named as intra‐network, inter‐network, and joint cooperation, involve traffic‐aware intelligent cooperation among eNBs belonging to the same or different networks. Our proposed techniques dynamically reconfigure LTE access networks in real time utilizing less number of active eNBs and thus, achieve energy savings. In addition, these techniques are distributed and self‐organizing in nature. Analytical models for evaluating switching dynamics of eNBs under these cooperation mechanisms are also formulated. We thoroughly investigate the proposed system under different numbers of cooperating networks, traffic scenarios, eNB power profiles, and their switching thresholds. Optimal energy savings while maintaining quality of service is also evaluated. Results indicate a significant reduction in network energy consumption. System performance in terms of network capacity utilization, switching statistics, additional transmit power, and eNB sleeping patterns is also investigated. Finally, a comprehensive comparison with other works is provided for further validation. Copyright © 2013 John Wiley & Sons, Ltd.     

RECA: Referenced energy‐based CDS algorithm in wireless sensor networks

Connected dominating sets (CDS) can be used to form virtual backbones for the hierarchical routing to save energy in the wireless sensor networks. The existing algorithms for CDS can only be used to the topologies that have larger vertex connective degrees. Besides, most of them do not consider the energy characteristics of the virtual backbones constructed by the dominating sets. In this paper, a referenced energy‐based CDS algorithm (RECA) is proposed, which can generate smaller CDS in random topologies without the limitation of vertex connective degrees. At the same time, the algorithm introduces Referenced Energy as a parameter for nodes when making the decision whether they are chosen to be the dominators or not. Therefore, as the experimental results show, the energy characteristic of the dominating set is improved and routing in the virtual backbones constructed by such CDSs will have a better performance. Copyright © 2009 John Wiley & Sons, Ltd.     

Energy‐efficient outage‐constrained power allocation based on statistical channel knowledge for dual‐hop cognitive relay networks

This paper investigates the power allocation problem in decode‐and‐forward cognitive dual‐hop systems over Rayleigh fading channels. In order to optimize the performance of the secondary network in terms of power consumption, an outage‐constrained power allocation scheme is proposed. The secondary nodes adjust their transmit power subject to an average interference constraint at the primary receiver and an outage probability constraint for the secondary receivers while having only statistical channel knowledge with respect to the primary nodes. We compare this approach with a power allocation scheme based on instantaneous channel state information under a peak interference constraint. Analytical and numerical results show that the proposed approach, without requiring the constant interchange of channel state information, can achieve a similar performance in terms of outage probability as that of power allocation based on instantaneous channel knowledge. Moreover, the transmit power allocated by the proposed approach is considerably smaller than the power allocated by the method based on instantaneous channel knowledge in more than 50% of the time. Copyright © 2015 John Wiley & Sons, Ltd.     

A prediction‐based and power‐aware virtual machine allocation algorithm in three‐tier cloud data centers

With the increasing popularity of cloud computing services, the more number of cloud data centers are constructed over the globe. This makes the power consumption of cloud data center elements as a big challenge. Hereby, several software and hardware approaches have been proposed to handle this issue. However, this problem has not been optimally solved yet. In this paper, we propose an online cloud resource management with live migration of virtual machines (VMs) to reduce power consumption. To do so, a prediction‐based and power‐aware virtual machine allocation algorithm is proposed. Also, we present a three‐tier framework for energy‐efficient resource management in cloud data centers. Experimental results indicate that the proposed solution reduces the power consumption; at the same time, service‐level agreement violation (SLAV) is also improved.