Total Network Power Consumption Research Articles

Robust precoding design for inter-satellite cooperation-based low-earth orbit satellite Internet of Things

With the widespread application of the Internet of Things (IoT), a large demand for supporting massive access of IoT devices distributed over a large area urges researchers to focus on the low-earth orbit (LEO) satellite IoT (SIoT) network. Due to the high-speed movement of LEO satellites, SIoT is composed of dozens of satellites to thousands of LEO satellites covering the whole world, which inevitably causes inter-satellite interference. Hence, in this paper, we propose an inter-satellite cooperation framework for a SIoT network based on non-orthogonal multiple access(NOMA) and multiple-beam techniques, which can support massive access and reduce interference. However, the satellite cannot catch accurate channel state information(CSI), resulting in residual interference. In this context, we formulate a robust precoding optimization problem based on inter-satellite cooperation to minimize the total power consumption of the LEO SIoT network with outage probability constraints on the rates for the IoT devices. Because the original problem is intractable, we utilize some mathematical tools, e.g., second-order Taylor expression, Bernstein-type inequality, and penalty function, to obtain an approximate equivalent second-order cone program (SOCP) problem. Then, we propose a robust precoding algorithm to solve the SOCP problem. Finally, numerical results show the impacts of key system parameters and confirm the effectiveness and robustness of the proposed algorithm.

The Reinforcement Learning based Local Routing Optimization for Ad-hoc Network

A reinforcement learning based local routing optimization scheme with two different semiconductor chips – hub IC and node ICs is proposed for the ad-hoc network. The received signal strength indicator (RSSI) in IC generates voltage information for analyzing network quality between each node and collected RSSI data are used for input and reward function of the learning agent. The Qlearning method is utilized for reinforcement learning. The chip fabricated with a 0.18 μm CMOS process, which uses the standard supply voltage of 1.5 V, achieves the lowest power consumption of 274 μW at the supply voltage of 0.8 V. The proposed reinforcement learning based local routing optimization for the ad-hoc network reduce 64 % of total network power consumption compare to the conventional infrastructure based network.

Online power aware coordinated virtual network embedding with 5G delay constraint

Solving virtual network embedding problem with delay constraint is a key challenge to realize network virtualization for current and future 5G core networks. It is an NP-Hard problem, composed of two sub-problems, one for virtual node embedding, and another one for virtual edges embedding, usually solved separately or with a certain level of coordination, which in general could result on rejecting some virtualization requests. Therefore, the main contributions of this paper focused on introducing an online power aware algorithm to solve the virtual network embedding problem using less resources and less power consumption, while considering end-to-end delay as a main embedding constraint. The new algorithm minimizes the overall power of the physical network through efficiently maximizing the utilization of the active infrastructure resources and putting into sleeping mode all non-active ones. Evaluations of the proposed algorithm conducted against the state of art algorithms, and simulation results showed that, when end-to-end delay was not included the proposed online algorithm managed to reduce the total power consumption of the physical network by 23% lower than the online energy aware with dynamic demands VNE algorithm, EAD-VNE. However, when end-to-end delay was included, it significantly influenced the whole embedding process and resulted on reducing the average acceptance ratios by 16% compared to the cases without delay.

Energy-Efficient User Scheduling and Power Allocation for NOMA-Based Wireless Networks With Massive IoT Devices

Nonorthogonal multiple access (NOMA) exhibits superiority in spectrum efficiency and device connections in comparison with the traditional orthogonal multiple access technologies. However, the nonorthogonality of NOMA also introduces intracell interference that has become the bottleneck limiting the performance to be further improved. To coordinate the intracell interference, we investigate the dynamic user scheduling and power allocation problem in this paper. Specifically, we formulate this problem as a stochastic optimization problem with the objective to minimize the total power consumption of the whole network under the constraint of all users’ long-term rate requirements. To tackle this challenging problem, we first transform it into a series of static optimization problems based on the stochastic optimization theory. Afterward, we exploit the special structure of the reformulated problem and adopt the branch-and-bound technique to devise an efficient algorithm, which can obtain the optimal control policies with a low complexity. As a good feature, the proposed algorithm can make decisions only according to the instantaneous system state and can guarantee the long-term network performance. Simulation results demonstrate that the proposed algorithm has good performance in convergence and outperforms other schemes in terms of power consumption and user satisfaction.

Energy-Saving in IP Over WDM Networks by Putting Protection Router Cards to Sleep

Energy saving is of great interest in current information and communications technology applications. In this paper, we consider energy saving for an IP over wavelength division multiplexed (WDM) optical network by putting protection router cards to sleep when the network is operating normally. Doing this requires that we must jointly consider several aspects. These are multi-layer traffic grooming, network protection, and the assignment of router ports/cards for working and protection optical channels. By employing different network protection techniques and the multi-hop traffic grooming strategy, we develop mixed integer linear programming (MILP) models for the optimization problem by considering five different router port assignment schemes. These aim to minimize the total power consumption of the whole network. Subsequently, to tackle the computational difficulty of the MILP models, we propose an efficient heuristic algorithm to handle large networks. This heuristic algorithm consists of two steps, i.e., survivable traffic grooming and router port assignment. Results show that the proposed energy-saving strategy is efficient and can significantly reduce the total power consumption of an IP over WDM network, where the assignment strategy for router cards is of primary importance for energy-saving efficiency. We also observe that the proposed heuristic algorithm performs almost as well as the MILP models in terms of the energy efficiency of the system.

RF Wireless Power Transfer: Regreening Future Networks

Over the past few years, green radio communication has drawn much attention from the research community, and it has a strong impact on various aspects, such as telecom businesses, wireless technologies, and natural environments. Specifically, the cost of electricity and CO2 emissions have been increasing due to wireless network operation. For instance, the number of base stations (BSs) is more than 4 million, and each BS consumes an average of 25 MWh/year (an estimated approximate of 80% of the total network's power consumption). Bearing in mind the environmental perspective, generating sufficient power to supply the networks causes a significant CO2 footprint. Particularly, the overall footprint of information and communication technology (ICT) services (e.g., computer, cell phone, and satellite networks) is predicted to triple by 2020.

Merit of hybrid EDFA/Raman amplification in fixed‐grid all‐optical network exploiting multirate transponders

SummaryThe constant need to improve network capacity and reduce power consumption in current fixed‐grid WDM networks motivates researchers to find alternative solutions other than replacing the deployed equipment. One of the possible solutions is the use of hybrid EDFA/Raman amplifier, which improves signal‐to‐noise‐ratio in a point‐to‐point link. This work aims at quantifying, by means of a detailed power model, the effect of these novel ideas on the power consumption of the network, which is key to build a future green Internet. In particular, we consider the use of a randomly generated topology of 20 nodes to study the effect of hybrid amplification, fiber type, fiber span length, and sensitivity to average link length and average traffic per node. Results show that hybrid amplification in moderate pumping regime minimizes total network power consumption for networks made up of all 3 fiber types in particular for nonzero dispersion‐shifted fiber.

Joint User Selection and Energy Minimization for Ultra-Dense Multi-channel C-RAN With Incomplete CSI

This paper provides a unified framework to deal with the challenges arising in dense cloud radio access networks (C-RAN), which include huge power consumption, limited fronthaul capacity, heavy computational complexity, unavailability of full channel state information (CSI), and so on. Specifically, we aim to jointly optimize the remote radio head (RRH) selection, user equipment (UE)-RRH associations and beam-vectors to minimize the total network power consumption (NPC) for dense multi-channel downlink C-RAN with incomplete CSI subject to per-RRH power constraints, each UE's total rate requirement, and fronthaul link capacity constraints. This optimization problem is NP-hard. In addition, due to the incomplete CSI, the exact expression of UEs' rate expression is intractable. We first conservatively replace UEs' rate expression with its lower bound. Then, based on the successive convex approximation technique and the relationship between the data rate and the mean square error, we propose a single-layer iterative algorithm to solve the NPC minimization problem with convergence guarantee. In each iteration of the algorithm, the Lagrange dual decomposition method is used to derive the structure of the optimal beam-vectors, which facilitates the parallel computations at the baseband unit pool. Furthermore, a bisection UE selection algorithm is proposed to guarantee the feasibility of the problem. Simulation results show the benefits of the proposed algorithms and the fact that a limited amount of CSI is sufficient to achieve performance close to that obtained when perfect CSI is possessed.

Content Caching and Distribution in Smart Grid Enabled Wireless Networks

To facilitate wireless transmission of multimedia content to mobile users, we propose a content caching and distribution framework for smart grid enabled OFDM networks, where each popular multimedia file is coded and distributively stored in multiple energy harvesting enabled serving nodes (SNs), and the green energy distributively harvested by SNs can be shared with each other through the smart grid. The distributive caching, green energy sharing and the on-grid energy backup have improved the reliability and performance of the wireless multimedia downloading process. To minimize the total on-grid power consumption of the whole network, while guaranteeing that each user can retrieve the whole content, the user association scheme is jointly designed with consideration of resource allocation, including subchannel assignment, power allocation and power flow among nodes, where the user association scheme decides which SN serves which user. First, the optimal power allocated to each subchannel and the power flows among nodes are derived analytically. Then, the user association problem is decoupled from the subchannel assignment problem, and the proposed user association scheme has leveraged the multicasting nature of the content download process. To decide which subchannel is assigned to which node, the number of subchannels assigned to each node is first determined, according to the green energy generating rate and the associated traffic offload, and then the corresponding subchannels are selected from the total assigned system spectrum. Simulation results demonstrate that bringing content, green energy and serving node closer to the end user can notably reduce the on-grid energy consumption.

Topology Control for Guaranteed Connectivity Provisioning in Heterogeneous Sensor Networks

Topology control is important for heterogeneous sensor networks in order to minimize the total network power consumption under the constraint that all sensor nodes’ connectivity requirements are satisfied. To address this issue, an optimization problem is first formulated, which is formally proved to be NP-hard. For practical applications, an effective solution, named topology adaptation algorithm (TAA), is proposed. TAA adopts both graph theory and maximum flow theory to find prespecified node disjoint paths with low time complexity and high network power efficiency. In order to further save the network power consumption, a judgment theory is proposed to remove any unnecessary long edges at the beginning without affecting network connectivity. Both theoretical and numeric results show that the proposed topology control algorithm can outperform counterparts in terms of the total network power consumption, the percentage of supernodes achieving $k$ -connectivity, the average degree of nodes, and the average length of paths.

Power Efficient Resource Allocation for Full-Duplex Radio Distributed Antenna Networks

In this paper, we study the resource allocation algorithm design for distributed antenna multiuser networks with full-duplex (FD) radio base stations (BSs), which enable simultaneous uplink and downlink communications. The considered resource allocation algorithm design is formulated as an optimization problem taking into account the antenna circuit power consumption of the BSs and the quality of service (QoS) requirements of both uplink and downlink users. We minimize the total network power consumption by jointly optimizing the downlink beamformer, the uplink transmit power, and the antenna selection. To overcome the intractability of the resulting problem, we reformulate it as an optimization problem with decoupled binary selection variables and nonconvex constraints. The reformulated problem facilitates the design of an iterative resource allocation algorithm, which obtains an optimal solution based on the generalized Bender’s decomposition (GBD). For this algorithm, we also propose a simple technique to improve the speed of convergence. Furthermore, to strike a balance between computational complexity and system performance, a suboptimal resource allocation algorithm with polynomial time complexity is proposed. Simulation results illustrate that the proposed GBD-based iterative algorithm converges to the globally optimal solution and the suboptimal algorithm achieves a close-to-optimal performance. Our results also demonstrate the tradeoff between power efficiency and the number of active transmit antennas when the circuit power consumption is taken into account. In particular, activating an exceedingly large number of antennas may not be an efficient approach for reducing the total system power consumption. In addition, our results reveal that FD systems facilitate significant power savings compared to traditional half-duplex systems, despite the nonnegligible self-interference.

Energy Efficiency of Downlink Transmission Strategies for Cloud Radio Access Networks

This paper studies the energy efficiency of the cloud radio access network (C-RAN), specifically focusing on two fundamental and different downlink transmission strategies, namely the data-sharing strategy and the compression strategy. In the data-sharing strategy, the backhaul links connecting the central processor (CP) and the base-stations (BSs) are used to carry user messages—each user’s messages are sent to multiple BSs; the BSs locally form the beamforming vectors then cooperatively transmit the messages to the user. In the compression strategy, the user messages are precoded centrally at the CP, which forwards a compressed version of the analog beamformed signals to the BSs for cooperative transmission. This paper compares the energy efficiencies of the two strategies by formulating an optimization problem of minimizing the total network power consumption subject to user target rate constraints, where the total network power includes the BS transmission power, BS activation power, and load-dependent backhaul power. To tackle the discrete and nonconvex nature of the optimization problems, we utilize the techniques of reweighted $\ell_1$ minimization and successive convex approximation to devise provably convergent algorithms. Our main finding is that both the optimized data-sharing and compression strategies in C-RAN achieve much higher energy efficiency as compared to the nonoptimized coordinated multipoint transmission, but their comparative effectiveness in energy saving depends on the user target rate. At low user target rate, data-sharing consumes less total power than compression; however, as the user target rate increases, the backhaul power consumption for data-sharing increases significantly leading to better energy efficiency of compression at the high user rate regime.

Joint Link Scheduling and Brightness Control for Greening VLC-Based Indoor Access Networks

Demands for broadband wireless access services are expected to outstrip the capacity in the near-term spectrum crunch. Deploying additional femtocells to address this challenge is cost-inefficient due to the backhaul challenge and the exorbitant system maintenance. According to an Alcatel-Lucent report, most mobile Internet access traffic happens indoors. Leveraging power line communication and the available indoor infrastructure, visible light communication (VLC) can be utilized with a small one-time cost. VLC also facilitates the great advantage of being able to jointly perform illumination and communications, and little extra power beyond illumination is required to empower communications, thus rendering wireless access with small power consumption. In this study, we investigate the problem of minimizing total power consumption of a general multiuser VLC indoor network while satisfying users' traffic demands and maintaining an acceptable level of illumination. We utilize the column-generation method to obtain an e-bounded solution. Several practical implementation issues are integrated with the proposed algorithm, including different configurations of light source and ways of resolving the interference among VLC links. Through extensive simulations, we show that our approach reduces the power consumption of the state-of-the-art VLC-based scheduling algorithms by more than 60% while maintaining the required illumination.

Alternate solutions for mine ventilation network to keep a pre-assigned fixed quantity in a working place

In underground constructions, a good ventilation design not only delivers fresh air to establish good working environment, but also provides a scientific and reliable basis to prevent disasters. In emergency cases, unexpected closure of the main airways may occur, providing the workers with alternative airways is substantial. This is important not only to sustain personnel lives, but also to prevent the mine ventilation system from damage. In this research, alternate solutions were introduced in case of failure in the underground construction to keep a pre-assigned fixed quantity in a working place for mine ventilation network. Eight different collapse scenarios were proposed to study their effect on the air quantity distribution among the branches in the ventilation circuit. From these scenarios, it is found that providing a sufficient air quantity in the working places could be achieved through modification of the network topology and adjusting the values of the regulators pressure. It is also indicated that the distance between the collapse and working places has a great effect on the amount of air delivered to it. A reduction in the power consumption could be done by re-arrange the installed regulators and decreasing the number of nodes and branches inside the network. A relationship representing the effect of changing the network topology on the total network power consumption was deduced through regression analysis. It is found that the total network power is quadratic dependent on the number of regulators and number of branches while it is directly dependent on the regulator power.

Green HetNet CoMP: Energy Efficiency Analysis and Optimization

This paper investigates advanced energy-efficient wireless systems in orthogonal frequency-division multiple access (OFDMA) downlink networks using coordinated multipoint (CoMP) transmissions between the base stations (BSs) in a heterogeneous network (HetNet), which is adopted by Third-Generation Partnership Project (3GPP) Long-Term Evolution (LTE)-Advanced to meet International Mobile Telecommunications-Advanced targets. HetNet CoMP has received significant attention as a way of achieving spectral efficiency (SE) and energy efficiency (EE). Usually, in the literature, the total network power consumption is restricted to the sum of the power consumption of all BSs. The significance of the power consumption of the backhaul links in wireless networks is normally omitted for its trivial effect with respect to that of the radio BSs. For SE and EE analysis of HetNet CoMP, the energy and bandwidth consumption of the backhaul is considered, without which, the investigation remains incomplete. However, SE and EE are design criteria in conflict with each other, and a careful study of their tradeoff is mandatory for designing future wireless communication systems. The EE is measured as “throughput (bits) per joule,” whereas the power consumption model includes RF transmit (radiated), circuit, and backhaul power. Furthermore, a nonideal backhaul model such as a microwave link is also investigated within intra-HetNet-CoMP (inside one cell), where an implementing fiber is not feasible. An intercell interference (ICI) coordination method is also studied to mitigate ICI. At the end, a novel resource allocation algorithm is proposed—modeled as an optimization problem—which takes into account the total power consumption, including radiated, circuit, and backhaul power, and the minimum required data rate to maximize EE. Given an SE requirement, the EE optimization problem is formulated as a constrained optimization problem. The considered optimization problem is transformed into a convex optimization problem by redefining the constraint using cubic inequality, which results in an efficient iterative resource allocation algorithm. In each iteration, the transformed problem is solved by using dual decomposition with a projected gradient method. Simulations results demonstrate how backhaul has a significant impact on total power consumption and the effectiveness of the studied schemes. In addition, the results demonstrate that the proposed iterative resource allocation algorithm converges within a small number of iterations and illustrate the fundamental tradeoffs between SE and EE. Our analytical results shed light on future “green” network planning in advanced OFDMA wireless systems like those envisioned for a fifth-generation (5G) system.

The 40 Gbps cascaded bit-interleaving PON

In this paper, a 40Gbps cascaded bit-interleaving passive optical network (CBI-PON) is proposed to achieve power reduction in the network. The massive number of devices in the access network makes that power consumption reduction in this part of the network has a major impact on the total network power consumption. Starting from the proven BiPON technology, an extension to this concept is proposed to introduce multiple levels of bit-interleaving. The paper discusses the CBI protocol in detail, as well as an ASIC implementation of the required custom CBI Repeater and End-ONT. From the measurements of this first 40Gbps ASIC prototype, power consumption reduction estimates are presented.

Wireless network power optimisation using relay stations blossoming and withering technique

AbstractPower consumption of wireless network is increasing as the demands in wireless data rates are escalating in modern life. Base stations are the major power consumption component in the wireless network. Therefore, the main challenge is to reduce the total power consumed in the network while maintaining the network coverage and its capacity. In this paper, a new relay switching perspective is introduced for relay blossoming and withering algorithm. First, relay switching is considered as a function of time representing the rate of active relays. The effect of the rate of active relays, arrival rate and average load factor of relays on the total network power consumption is modelled. It is found that the rate of active relay function that optimises the network power consumption obeys linear first‐order ordinary differential equation. The effect of different synthesised arrival rate profiles on the rate of active relay is presented. Moreover, relative relay to base station capacity parameter is defined, and its effect on the power optimisation is investigated. Based on the solutions of the ordinary differential equation, an approximate fuzzy‐based relay sleeping mode is introduced. The fuzzy logic sleeping mode utilises the arrival rate and its derivative as inputs. The solution of the differential equations shows that power saving up to 45 and 30 per cent can be achieved in sleeping and idling modes, respectively, in contrast to 42 per cent achieved from the fuzzy sleeping mode. The increasing slope of the arrival rate results in less power saving. Copyright © 2015 John Wiley & Sons, Ltd.

On methodologies to estimate optical-layer power consumption and cost for long-haul WDM networks with optical reach constraint

This paper deals with the methodologies to obtain the estimates of optical-layer power consumption and cost for long-haul optical networks using wavelength-division multiplexing (WDM) with IP-over-WDM and IP-over-MPLS-over-WDM network settings. Such optical networks generally employ wavelength routing at intermediate nodes and are known as wavelength-routed optical networks (WRONs). In WRON-based long-haul networks, optical reach (OR) of a transponder represents the maximum distance over which its optical signal can travel without any optical/electrical/optical regeneration and plays a significant role in deciding the power consumption and cost of the optical layer. In IP-over-WDM network setting, IP routers are directly interfaced with WRON and bandwidth requests are equal to the lightpath capacity. In IP-over-MPLS-over-WDM network setting, IP routers are interfaced with WRON via MPLS routers and bandwidth requests arrive as label-switched paths, which are generally lower than the lightpath capacity. We examine the above networks with mixed-OR nodes (transponders in each WRON node having different OR values but all transmitting at 10 Gbps) and fixed-OR nodes (transponders in each WRON node having same OR value and 10 Gbps transmission rate). In this investigation, two types of control planes are considered, namely unified control plane and isolated control plane. The network with unified control plane supports automated and dynamic resource provisioning for both short-term and long-term bandwidth requests. The study on nonautomated network using isolated control plane considers resource provisioning only for long-term bandwidth requests. Simulation-based network provisioning is carried out using C++, considering appropriate traffic models, OR constraints, node configurations and network architectures. The results of our simulations indicate in general how OR of the transponders can influence the total network cost and power consumption in optical layer. Overall, the nonautomated networks with mixed-OR configuration are found to save power and offer lower cost with respect to fixed-OR configuration, while the automated networks with mixed-OR configuration can save power while the cost increases with respect to fixed-OR option.

Green optical orthogonal frequency‐division multiplexing networks

Orthogonal frequency-division multiplexing (OFDM) has been proposed as an enabling technique for elastic optical networks to support heterogeneous traffic demands by enabling rate and modulation adaptive bandwidth allocation. The authors investigate the energy efficiency of optical OFDM-based networks. A mixed integer linear programming model is developed to minimise the total power consumption of rate and modulation adaptive optical OFDM networks. Considering a symmetric traffic, the results show that optical OFDM-based networks can save up to 31% of the total network power consumption compared to conventional Internet protocol over wavelength division multiplexing (WDM) networks. Considering the power consumption of the optical layer, the optical OFDM-based network saves up to 55% of the optical layer power consumption. The results also show that under an asymmetric traffic scenario, where more traffic is destined to or originates from popular nodes, for example data centres, the power savings achieved by the optical OFDM-based networks are limited as the higher traffic demands to and from data centres reduce the bandwidth wastage associated with conventional WDM networks. Furthermore, the achievable power savings through data compression have been investigated, considering an optical OFDM-based network.

Quadrant Based DIR in CWin Adaptation Mechanism for Multihop Wireless Network

In Multihop Wireless Networks, traffic forwarding capability of each node varies according to its level of contention. Each node can yield its channel access opportunity to its neighbouring nodes, so that all the nodes can evenly share the channel and have similar forwarding capability. In this manner the wireless channel is utilize d effectively, which is achieved using Contention Window Adaptation Mechanism (CWAM). This mechanism achieves a higher end to - end throughout but consumes the network power to a higher level. So, a newly proposed algorithm Quadrant Based Directional Routing Protocol (Q-DIR) is implemented as a cross - layer with CWAM, to reduce the total network power consumption through limited flooding and also reduce the routing overheads, which eventually increases overall network throughput. This algorithm limits the broadcast region to a quadrant where the source node and the destination nodes are located. Implementation of the algorithm is done in Linux based NS-2 simulator.