Adaptive Link Rate Research Articles

Hybrid Satellite-UAV-Terrestrial Networks for 6G Ubiquitous Coverage: A Maritime Communications Perspective

In the coming smart ocean era, reliable and efficient communications are crucial for promoting a variety of maritime activities. Current maritime communication networks (MCNs) mainly rely on marine satellites and on-shore base stations (BSs). The former generally provides limited transmission rate, while the latter lacks wide-area coverage capability. Due to these facts, the state-of-the-art MCN falls far behind terrestrial fifth-generation (5G) networks. To fill up the gap in the coming sixth-generation (6G) era, we explore the benefit of deployable BSs for maritime coverage enhancement. Both unmanned aerial vehicles (UAVs) and mobile vessels are used to configure deployable BSs. This leads to a hierarchical satellite-UAV-terrestrial network on the ocean. We address the joint link scheduling and rate adaptation problem for this hybrid network, to minimize the total energy consumption with quality of service (QoS) guarantees. Different from previous studies, we use only the large-scale channel state information (CSI), which is location-dependent and thus can be predicted through the position information of each UAV/vessel based on its specific trajectory/shipping lane. The problem is shown to be an NP-hard mixed integer nonlinear programming problem with a group of hidden non-linear equality constraints. We solve it suboptimally by using Min-Max transformation and iterative problem relaxation, leading to a process-oriented joint link scheduling and rate adaptation scheme. As observed by simulations, the scheme can provide agile on-demand coverage for all users with much reduced system overhead and a polynomial computation complexity. Moreover, it can achieve a prominent performance close to the optimal solution.

TEAP: Traffic Engineering and ALR policy based Power-aware solutions for green routing and planning problems in backbone networks

Enormous and ever-increasing energy consumption in the Internet and the burgeoning global GreenHouse Gas (GHG) emission that come with it have been crucial issues for the past few years due to an exponential traffic growth and a rapid expansion of communication infrastructures worldwide. In this paper, we target Routing and Planning problems of Green Networking with bundled links referred to as RPGN by leveraging Traffic Engineering (TE) and Adaptive Link Rate (ALR) policy jointly to investigate the power-saving potentialities and effective applicability in the backbone networks. We formulate RPGN as a non-linear multi-commodity flow model and develop green heuristics-TE and ALR policy based Power-aware heuristics (TEAP) to solve it. We have investigated and compared different characterizations of the solutions to RPGN by evaluating network power saving ratio, rate level duration distribution, mean rate switching times and mean running time, under different real backbone network topology scenarios. Our results indicate the different power-saving potential of these solutions once applied in the backbone network.

Implementation of a Fast Link Rate Adaptation Algorithm for WLAN Systems

With a target to maximize the throughput, a fast link rate adaptation algorithm for IEEE 802.11a/b/g/n/ac is proposed, which is basically preamble based and can adaptively compensate for the discrepancy between transmitter and receiver radio frequency performances by exploiting the acknowledgment signal. The target system is a 1 × 1 wireless local area network chip with no null data packet or sounding. The algorithm can be supplemented by automatic rate fallback at the initial phase to further expedite rate adaptation. The target system receives wireless channel coefficients and previous packet information, translates them to amended signal-to-noise ratios, and then, via the mean mutual information, selects the modulation and coding scheme with the maximum throughput. Extensive simulation and wireless tests are carried out to demonstrate the validity of the proposed adaptive preamble-based link adaptation in comparison with both the popular automatic rate fallback and ideal link adaptation. The throughput gain of the proposed link adaptation over automatic rate fallback is demonstrated over various packet transmission intervals and Doppler frequencies. The throughput gain of the proposed algorithm over ARF is 46% (15%) for a 1-tap (3-tap) channel over 10 m–250 m (16 m–160 m) normalized Doppler frequencies. Assuming a 3-tap channel and 30 m–50 m normalized Doppler frequencies, the throughput of the proposed algorithm is about 31 Mbps, nearly the same as that of ideal link adaptation, whereas the throughput of ARF is about 24 Mbps, leading to a 30% throughput gain of the proposed algorithm over ARF. The firmware is implemented in C and on Xilinx Zynq 7020 (Xilinx, San Jose, CA, USA) for wireless tests.

Power-Efficient Software-Defined Data Center Network

The energy consumed by data centers has been growing rapidly in recent years. Among all the major contributors to the power consumption of entire data centers, data center network (DCN) can account for up to 20% of the total power consumption. In this article, we first devise a power-efficient software-defined DCN (PESD-DCN) framework, which can achieve desirable power efficiency, avoid potential link congestion, and reduce frequent device state transition. Then, we formulate the optimization problem of maximizing the radio full-utilized devices to all devices. To solve it, we propose correlation-aware flow routing (CFR) algorithm, which leverages correlation-aware flow consolidation (CFC) technique to improve energy efficiency, avoid the potential link congestion, and reduce frequent device state transition. Moreover, to further improve the DCN energy efficiency, we propose flow rerouting, link rate adaptation, and device sleeping (FLD) algorithm. Finally, simulation results demonstrate that PESD-DCN can achieve a good performance. More specifically, in comparison to the other baseline algorithms, PESD-DCN can achieve up to 79.19% energy efficiency, 67.1% decrease in switch state transition (SST), and 55.4% decrease in link state transition (LST).

Emulation of burst-based adaptive link rates in NetFPGA towards green networking

In recent times, energy consumption in communication media has been increasing drastically. In the literature, energy-saving techniques that enable network devices to enter sleep state or limit the data rate have been proposed to reduce energy costs. In our earlier work, we proposed an energy-saving technique called burst-based adaptive link rate BBALR , the simulation of which assures increased energy savings. In this paper, we have emulated the hardware implementation of BBALR and compared its performance with the outputs of other prominent energy-saving policies based on dynamic link rate adaption. The energy savings are mapped from the measured sleep time and reference power values. We have used NetFPGA as the testbed, which is a research platform for building real-time network hardware prototypes.

Correlation-Aware Traffic Consolidation for Power Optimization of Data Center Networks

Power optimization has become a key challenge in the design of large-scale enterprise data centers. Existing research efforts focus mainly on computer servers to lower their energy consumption, while only few studies have tried to address data center networks (DCNs), which can account for 10-20 percent of the total energy consumption of a data center. In this paper, we propose CARPO, a correlation-aware power optimization algorithm that dynamically consolidates traffic flows onto a small set of links and switches in a DCN and then shuts down unused network devices for energy savings. In sharp contrast to existing work, CARPO is designed based on a key observation from the analysis of real DCN traces that the bandwidth demands of different flows do not peak at exactly the same time. As a result, if the correlations among flows are considered in consolidation, more energy savings can be achieved. In addition, CARPO integrates traffic consolidation with link rate adaptation for maximized energy savings. We implement CARPO on a hardware testbed composed of 10 virtual switches configured with a production 48-port OpenFlow switch and 8 servers. Our empirical results with traces from Wikipedia and Yahoo! data centers demonstrate that CARPO can save up to 50 percent of network energy for a DCN, while having only negligible delay increases. CARPO also outperforms two state-of-the-art baselines by 19.6 and 95 percent on energy savings, respectively. Our simulation results with a large-scale DCN also show that CARPO can achieve more energy savings than the baselines for typical DCN topologies, such as fat tree and BCube.

Flow-Based Management For Energy Efficient Campus Networks

Recent studies have shown that the energy consumption of wireless access networks is a threat to the sustainability of mobile cloud services. Consequently, energy efficient solutions are becoming crucial for both local and wireless access networks. In this paper, we propose a flow-based management framework to achieve energy efficiency in campus networks. We address the problem from the dynamic perspective, where users come and leave the system in an unpredictable way. Specifically, we propose an online flow-based routing approach that allows dynamic reconfiguration of existing flows as well as dynamic link rate adaptation, while taking into account users’ demands and mobility. Our approach is compliant with the emerging software defined networking (SDN) paradigm since it can be integrated as an application on top of an SDN controller. To achieve this, we first formulate the flow-based routing problem as an integer linear program (ILP). As this problem is known to be $\mathcal{NP}$ -hard, we then propose a simple yet efficient ant colony-based approach to solve the formulated ILP. Through extensive simulations, we show that our proposed approach is able to achieve significant gains in terms of energy consumption, compared to heuristic solutions and conventional routing solutions such as the shortest path (SP) routing, the minimum link residual capacity routing metric (MRC), and the load balancing (LB) scheme. In particular, we show that the energy consumption can be reduced by up to 7%, 35%, 44%, and 49% compared to Greedy-OFER, MRC, SP, and LB, respectively, while ensuring the required quality of service (QoS).

Integration of scheduling and network coding in multi-rate wireless mesh networks: Optimization models and algorithms

In order to fully utilize spectrum resource in wireless mesh networks (WMNs), we propose a combination of some popular communication techniques, including link scheduling, spatial reuse, power and rate adaptation and network coding (NC), to activate as many transmission links as possible during one scheduling period, so that the total scheduling length can be minimized and network throughput can be maximized. Different from previous studies, we consider the interplay among these techniques and present an optimal NC-aware link scheduling mechanism in multi-rate WMNs, which relies on the enumeration of all possible schedules. Due to the high computational complexity of our proposed model, we utilize a column generation (CG)-based method to resolve the optimization problem and decompose it into a master problem (MP) and a pricing problem (PP). Furthermore, we present a distributed power control algorithm for PP, by which the computational complexity of the CG-based scheme can be largely reduced. Simulation results demonstrate the superiority of our method under various network situations.

Optimizing the throughput‐lifetime tradeoff in wireless sensor networks with link scheduling, rate adaptation, and power control

AbstractThroughput and lifetime are usually conflicting objectives in designing wireless sensor networks; hence, the right balance needs to be found. With this aim in view, we address in this paper the problem of minimizing the frame length defined within a time division multiple access scheme and the problem of maximizing network lifetime subject to a maximum frame length. The pursued solution in either case leverages a wide range of parameters related to coverage, routing, transmission power, and data rate. Furthermore, it is consistent with the physical interference model. To this end, we rely on column generation technique to derive near‐optimal solutions even when the integrality constraints on coverage and flow variables are enforced. Moreover, we propose a polynomial‐time heuristic algorithm to solve efficiently the underlying NP‐hard problem of concurrent link selection with discrete power control and rate adaptation. Simulation results show that our heuristic algorithm leads to solutions within 3% of optimality while saving around 99% of computation time. Besides, the results illustrate the significant impact of power control and rate adaptation on throughput and lifetime improvement. Interestingly, we found that network lifetime can be significantly prolonged when traffic demands are sufficiently low at the affordable cost of small decrease in throughput. Copyright © 2015 John Wiley & Sons, Ltd.

Celerity: A Low-Delay Multi-Party Conferencing Solution

In this paper, we revisit the problem of multi-party conferencing from a practical perspective, and to rethink the design space involved in this problem. We believe that an emphasis on low end-to-end delays between any two parties in the conference is a must, and the source sending rate in a session should adapt to bandwidth availability and congestion. We present Celerity, a multi-party conferencing solution specifically designed to achieve our objectives. It is entirely Peer-to-Peer (P2P), and as such eliminating the cost of maintaining centrally administered servers. It is designed to deliver video with low end-to-end delays, at quality levels commensurate with available network resources over arbitrary network topologies where bottlenecks can be anywhere in the network. This is in contrast to commonly assumed P2P scenarios where bandwidth bottlenecks reside only at the edge of the network. The highlight in our design is a distributed and adaptive rate control protocol, that can discover and adapt to arbitrary topologies and network conditions quickly, converging to efficient link rate allocations allowed by the underlying network. In accordance with adaptive link rate control, source video encoding rates are also dynamically controlled to optimize video quality in arbitrary and unpredictable network conditions. We have implemented Celerity in a prototype system, and demonstrate its superior performance over existing solutions in a local experimental testbed and over the Internet.

Traffic-Aware Link Rate Adaptation for Multi-rate 802.11 Networks

802.11 networks provide multi-rate capability to offer rate adaptability against the time-varying wireless channel. However, how to switch between the available rates has not been standardized. Existing rate adaptation (RA) solutions assume common transmission power and can only passively tune link rate to match the inferred channel condition via different methods. This simple attitude is neither flexible in traffic-aware link rate selection nor effective in energy conservation and spatial reuse since transmission power may be either too low to sustain the link rate or too high that results in unnecessary energy consumption and worse spatial reuse. Different from existing solutions, we think that link rate switch should be driven by traffic load and power control should be considered with rate adaptation together to conserve energy and increase spatial reuse. To this end, we propose a traffic-aware link rate adaptation scheme (TARA) via power control for multi-rate 802.11 networks. Its basic idea consists of a two-step procedure. Firstly, traffic load is sensed in the MAC layer to decide whether link rate should be increased or decreased for the next transmission. Afterwards, power control is carried out in the PHY layer to guarantee that the new link rate can be sustained while minimizing the transmission power. Extensive simulation results show that TARA outperforms typical existing schemes in terms of energy efficiency and throughput.

EARC: Enhanced Adaptation of Link Rate and Contention Window for IEEE 802.11 Multi-Rate Wireless Networks

IEEE 802.11 wireless network supports multiple link rates at the physical layer. Each link rate is associated with a certain required Signal-to-Interference-and-Noise Ratio (SINR) threshold for successfully decoding received packets. On transmission failures, the 802.11 DCF performs a binary exponential backoff mechanism to discourage channel access attempts, hoping to reduce congestion. When traditional link adaptation is applied, both rate reduction and binary backoff represent double penalties for this wireless link, which may cause overly conservative transmission attempts. On the other hand, once transmission succeeds, 802.11 DCF resets the backoff contention window to the minimum value to encourage channel access attempts. At the same time, traditional link adaptation may also decide to increase the data rate, which leads to overly aggressive transmission attempts. We observe this improper interaction of link rate and backoff mechanism that harms the 802.11 system performance, due to separate consideration of those two parameters. In this paper, we propose to jointly adapt the rate and backoff parameters. Specifically, an Enhanced Adaptation of link Rate and Contention window, abbreviated as EARC, is devised. EARC is a closed-loop (receiver-assisted) link rate adaptation protocol that jointly considers the backoff mechanism. With only one extra byte carried by the DATA packet, EARC incurs little controlling overhead despite its receiver-assisted nature. Moreover, since SINR information commonly utilized by receiver-assisted protocols is not precisely supported in real devices, we introduce a rate selection reference (RSR) table empirically derived by constantly monitoring the environmental energy level and reception behavior. The RSR table then guides the receiver to select the best sustainable rate for the transmitter. Simulation results demonstrate the RSR table is a practical option for making the rate decision, and the proposed EARC approach is effective in maintaining high system throughput, compared to other link adaptation algorithms.

A survey on Green communications using Adaptive Link Rate

The Information and Communication Technology sector is considered to be a major consumer of energy and has become an active participant in Green House Gas emissions. Lots of efforts have been devoted to make network infrastructure and network protocols power-aware and green. Among these efforts, Adaptive Link Rate (ALR) is one of the most widely discussed approaches. This survey highlights the most recent ALR approaches with a brief taxonomy and the state of the art.

Study of the potential energy savings in Ethernet by combining Energy Efficient Ethernet and Adaptive Link Rate

ABSTRACTThe Energy Efficient Ethernet (EEE) standard (IEEE 802.3az) has introduced some modifications to existing Ethernet standards with the aim of improving energy efficiency in the transmission of data frames. The adopted mechanism is to use different power modes of operation such that a device can be put into a low‐power mode when there is no data to transmit and awake it very quickly upon frame arrival. This is expected to reduce energy consumption significantly, especially on low‐loaded links. An alternative to EEE, known as Adaptive Link Rate (ALR), was also proposed to improve energy efficiency in Ethernet by dynamically changing the link speed at different traffic loads. ALR reduces the energy consumption because the lower the link speed, the less energy is consumed. However, this option is no longer considered in the EEE standard process.In this work, the potential energy savings of combining both EEE and ALR are explored. The results show that such a combination can further improve the already efficient EEE standard given the different power overheads associated with transitions between the active and idle power modes at different link speeds. This conclusion provides a clear motivation to investigate the combination of EEE and ALR more in detail in further developments. Copyright © 2011 John Wiley & Sons, Ltd.

A Survey of Green Networking Research

Reduction of unnecessary energy consumption is becoming a major concern in wired because of the potential economical benefits and of its expected environmental impact. These issues, usually referred to as networking, relate to embedding energy-awareness in the design, in the devices and in the protocols of networks. In this work, we first formulate a more precise definition of the attribute. We furthermore identify a few paradigms that are the key enablers of energy-aware networking research. We then overview the current state of the art and provide a taxonomy of the relevant work, with a special focus on wired networking. At a high level, we identify four branches of green networking research that stem from different observations on the root causes of energy waste, namely (i) adaptive link rate, (ii) interface proxying, (iii) energy-aware infrastructure and (iv) energy-aware applications. In this work, we not only explore specific proposals pertaining to each of the above branches, but also offer a perspective for research.

IP Over WDM Networks Employing Renewable Energy Sources

With network expansion, the energy consumption and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emissions associated with networks are increasing rapidly. In this paper we propose an approach for energy minimization in IP over WDM networks and furthermore propose the use of renewable energy to further reduce the CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emissions at a given energy consumption level. We develop a Linear Programming (LP) model for energy minimization in the network when renewable energy is used and propose a novel heuristic for improving renewable energy utilization. Compared with routing in the electronic layer, routing in the optical layer coupled with renewable energy nodes significantly reduces the CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emission of the IP over WDM network considered by 47% to 52%, and the new heuristic introduced hardly affects the QoS. In order to identify the impact of the number and the location of nodes that employ renewable energy on the non-renewable energy consumption of whole network, we also constructed another LP model. The results show that the nodes at the center of the network have more impact than other nodes if they use renewable energy sources. We have also investigated the additional energy savings that can be gained through Adaptive Link Rate (ALR) techniques where different load dependent energy consumption profiles are considered. Our optimized REO-hop routing algorithm with renewable energy and ALR results in a maximum energy saving of 85% (average of 65%) compared to a current network design where all nodes are statically dimensioned for the maximum traffic in terms of IP ports and optical layer and hence consume power accordingly. Furthermore, when all the nodes have access to typical levels of renewable power we show that the associated reduction in non-renewable energy consumption reduces the network's CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emissions by 97% peak, 78% average.

Study and Demonstration of Sleep and Adaptive Link Rate Control Mechanisms for Energy Efficient 10G-EPON

This paper describes sleep and adaptive link rate (ALR) control functions to reduce the power consumption of optical network units (ONUs) in 10 Gb∕s Ethernet passive optical network (10G-EPON) systems. A hybrid mechanism that includes both sleep and ALR control functions is proposed with a view to further improving the power-saving performance. The sleep control function switches the ONU mode, i.e., active or sleep, depending on the presence or absence of traffic. The ALR control function switches the downlink rates between an optical line terminal (OLT) and an ONU, i.e., 1 Gb∕s or 10 Gb∕s, depending on the quantity of traffic. The proposed hybrid mechanism offers effective power management of ONUs on the basis of the traffic conditions. The proposed hybrid mechanism is validated by a numerical simulation and an experiment.

Hybrid power-saving mechanism with cyclic sleep and adaptive link rate functions for 10G-EPON systems

An advanced power-saving mechanism based on a combination of a cyclic sleep function and an adaptive link rate (ALR) function for 10 Gbit/s Ethernet passive optical network (10G-EPON) systems is proposed. The cyclic sleep function varies the sleep period to optimise power-saving performance according to frame inter-arrival time. The ALR function has dual-threshold policy to prevent the frequent switching of link rates. The proposed hybrid mechanism provides effective power-saving performance on the basis of traffic conditions.

Interview

Dr Ryogo Kubo from NTT Corporation in Japan tells us more about the motivations for his research in the Letter ‘Hybrid power-saving mechanism with cyclic sleep and adaptive link rate functions for 10G-EPON systems’ on page 934.

Reducing the Energy Consumption of Ethernet with Adaptive Link Rate (ALR)

The rapidly increasing energy consumption by computing and communications equipment is a significant economic and environmental problem that needs to be addressed. Ethernet network interface controllers (NICs) in the US alone consume hundreds of millions of US dollars in electricity per year. Most Ethernet links are underutilized and link energy consumption can be reduced by operating at a lower data rate. In this paper, we investigate adaptive link rate (ALR) as a means of reducing the energy consumption of a typical Ethernet link by adaptively varying the link data rate in response to utilization. Policies to determine when to change the link data rate are studied. Simple policies that use output buffer queue length thresholds and fine-grain utilization monitoring are shown to be effective. A Markov model of a state-dependent service rate queue with rate transitions only at service completion is used to evaluate the performance of ALR with respect to the mean packet delay, the time spent in an energy-saving low link data rate, and the oscillation of link data rates. Simulation experiments using actual and synthetic traffic traces show that an Ethernet link with ALR can operate at a lower data rate for over 80 percent of the time, yielding significant energy savings with only a very small increase in packet delay.