Data Transmission Scheduling Research Articles

EcoPlan: energy-efficient downlink and uplink data transmission in mobile cloud computing

Mobile cloud computing (MC2) is emerging as a new computing paradigm that seeks to augment resource-constrained mobile devices for executing computing- and/or data-intensive mobile applications. Nonetheless, the energy-poverty nature of mobile devices has become a stumbling block that greatly impedes the practical application of MC2. Fortunately, for delay-tolerant mobile applications, energy conservation is achievable via two means: (1) dynamic selection of energy-efficient links (e.g., WiFi interface); and (2) deferring data transmission in bad connectivity. In this paper, we study the problem of energy-efficient downlink and uplink data transmission between mobile devices and clouds. In the presence of unpredictable data arrival, network availability and link quality, our objective is to minimize the time average energy consumption of a mobile device while ensuring the stability of both device-end and cloud-end queues. To achieve this goal, we propose an online control framework named EcoPlan under which mobile users can make flexible link selection and data transmission scheduling decisions to achieve arbitrary energy-delay tradeoffs. Real-world trace-driven simulations demonstrate the effectiveness of EcoPlan, along with its superior energy-efficiency over alternative WiFi-prioritized, minimum-delay and SALSA schemes.

Low-Latency SINR-Based Data Gathering in Wireless Sensor Networks

Data gathering is a fundamental operation in various applications of wireless sensor networks (WSNs), where sensor nodes sense information and forward data to a sink node via multi-hop wireless communications. Typically, data in a WSN is relayed over a tree topology to the sink for effective data gathering. A number of tree-based data gathering schemes have been proposed in the literature, most of which aim at maximizing network lifetime. However, the timeliness and reliability of gathered data are also of great importance to many applications in WSNs. To achieve low-latency, high-reliability data gathering in WSNs, in this paper, we construct a data gathering tree based on a reliability model, schedule data transmissions for the links on the tree and assign transmitting power to each link accordingly. Since the reliability of a link is highly related to its signal to interference plus noise ratio (SINR), the SINR of all the currently used links on the data gathering tree should be greater than a threshold to guarantee high reliability. We formulate the joint problem of tree construction, link scheduling and power assignment for data gathering into an optimization problem, with the objective of minimizing data gathering latency. We show the problem is NP-hard and divide the problem into two subproblems: Constructing a low-latency data gathering tree; Jointly link scheduling and power assignment for the data gathering tree. We then propose a polynomial heuristic algorithm for each subproblem and conduct extensive simulations to verify the effectiveness of the proposed algorithms. Our simulation results show that the proposed algorithms achieve much lower data gathering latency than existing data gathering strategies while guaranteeing high reliability. Moreover, the algorithms also have a comparable energy efficiency and network lifetime to other algorithms.

Energy-Efficient Link Selection and Transmission Scheduling in Mobile Cloud Computing

Mobile cloud computing (MCC) converges mobile computing and Cloud computing for augmenting resource-poor mobile devices to run ??heavier?? applications. With the increasing ubiquity of mobile devices, MCC exhibits vast application potential in various areas. Energy-efficient data transmission is a key issue in MCC due to energy-poverty of mobile devices. In this letter, we address the issue of energy-efficient link selection and data transmission scheduling for delay-tolerant and data-intensive applications in MCC. We first formulate the problem as a discrete-time stochastic dynamic program (SDP) that aims to optimize both system throughput and energy consumption. To solve the formulated SDP, we then propose a scalable approximate dynamic programming (ADP) algorithm that does not require the statistics of exogenous stochastic information (e.g., data arrival). Simulation studies show that the proposed ADP algorithm can reduce the average energy consumed for delivering a packet by a maximum of over 40 percent compared to alternative minimum-delay and SALSA policies.

A data transmission scheduling algorithm for rapid-response earth-observing operations

With the development of rapid-response Earth-observing techniques, the demand for reducing a requirements-tasking-effects cycle from 1day to hours grows rapidly. For instance, a satellite user always wants to receive requested data in near real-time to support their urgent missions, such as dealing with wildfires, volcanoes, flooding events, etc. In this paper, we try to reduce data transmission time for achieving this goal. The new feature of a responsive satellite is that users can receive signals from it directly. Therefore, the traditional satellite control and operational techniques need to be improved to accommodate these changes in user needs and technical upgrading. With that in mind, a data transmission topological model is constructed. Based on this model, we can deal with the satellite data transmission problem as a multi-constraint and multi-objective path-scheduling problem. However, there are many optional data transmission paths for each target based on this model, and the shortest path is preferred. In addition, satellites represent scarce resources that must be carefully scheduled in order to satisfy as many consumer requests as possible. To efficiently balance response time and resource utilization, a K-shortest path genetic algorithm is proposed for solving the data transmission problem. Simulations and analysis show the feasibility and the adaptability of the proposed approach.

Scheduling data transmissions in wireless sensor networks used for position tracking

In wireless sensor networks developed for ambient assisted living (AAL) applications, power supply is one of the most challenging problems. In the case when measurements have low cost; a method is proposed for decreasing the time of communication by handling the measured data locally. In AAL applications the position tracking of a person is an essential task. Position tracking with motion sensors requires high number of messages and most of them are caused by local movements. Our suggestion is to eliminate these messages. The method is based on Hidden Markov Model of the motions of an observed person. The model provides information based on the estimated global state of the system, which is the position of the person in the space of interest. This state can be forwarded to the nodes so they locally perform the filtering to save valuable energy by not transmitting messages which are not relevant.

Performance improvements of HCCA scheduling in V2R environments

SummaryThis paper addresses the issue of real‐time data transmission in vehicles to roadside environment by the hybrid coordination function controlled channel access (HCCA) scheme with Institute of Electrical and Electronics Engineers 802.11p protocol. The HCCA is one of the medium access protocols specified in 802.11p standard, which uses a polling scheme similar to the point coordination function to provide a reliable QoS. In this paper, we improve the HCCA polling scheme and design a new data transmission scheduling method. We also prepared a mathematical model to systematically evaluate the performance of the HCCA in terms of average delay. Moreover, we analyze the factors that could impact the average delay, throughput, and packet loss rate as well. The simulation results are compared with the original scheme specified in the standard. The simulation results demonstrate that the proposed delay model could estimate the average delay of the HCCA with a high precision, whereas the proposal of the enhancement of the HCCA has lower delay, lower loss rate, and higher throughput than the one specified in the standard. Copyright © 2013 John Wiley & Sons, Ltd.

Improvement of polling and scheduling scheme for real-time transmission with HCCA of IEEE 802.11p protocol

This paper addresses the issue of real-time data transmission in vehicles to roadside (V2R) environment by the hybrid coordination function (HCF) of controlled channel access (HCCA) specified by the IEEE 802.11p standard. HCCA is one of the medium access mechanisms in the IEEE 802.11 standard, and uses the polling scheme similar to the point coordination function (PCF) to provide reliable quality of service (QoS), which may cause resource overshooting and high time consuming. This paper tries to improve the performance of the HCCA polling scheme and designs new data transmission scheduling scheme. The simulation results of the proposal are compared with those of the standard strategy. Simulation results demonstrate that the improved HCCA has lower delay, loss rate, and higher throughput than those of the standard one.

A token circulation scheme for code assignment and cooperative transmission scheduling in CDMA-based UAV ad hoc networks

Code division multiple access (CDMA) ad hoc networks have been considered a promising multiple-channel networking architecture for connecting tactical platforms in battle fields. In this paper we consider a network of a swarm of unmanned aerial vehicles (UAVs) that are used in a tactical surveillance mission. The UAVs are assumed to have multiuser detection capability and form a CDMA-based ad hoc network. A token circulation scheme is proposed to conduct functions required at the medium access control layer including detection of hidden/lost neighbors, code assignment and schedule-based cooperative transmission scheduling. In the proposed scheme, a token continuously circulates around the network based on the "receive-forward" module. Through circulation of the token, each UAV can detect its hidden and/or lost neighbors in near real-time, assign codes enabling the spatial reuse of code channels without incurring code collision, and schedule data transmissions in a cooperative and distributed manner. In addition, the proposed scheme is able to take advantage of multiuser detection functionality and allows for simultaneous transmissions from multiple transmitters to a same receiver. The performance of the proposed token circulation scheme is evaluated, both analytically and through simulations. It is shown that the latency of the token is at most linearly proportional to the network size, and the average delay of a data packet increases with either the packet generation rate or the network size. The results also show that the proposed token circulation scheme is suitable for large-scale CDMA-based UAV ad hoc networks with even heavy network traffic load.

Numerical and Analytical Methods for Variational Inequalities and Related Problems 2013

The study of variational inequalities and related problems with applications constituted a rich topic of intensive research efforts within the latest 50 years. Variational inequalities problems have been found with an explosive growth in theoretical advances, algorithmic development, and applications across all the disciplines of pure and applied sciences. Analysis of these problems requires a blend of techniques from convex analysis, nonlinear functional analysis, and numerical analysis. As a result of interaction between different branches of mathematical and engineering sciences, we now have a variety of techniques to suggest and analyze various algorithms for solving variational inequalities and related optimization problems with applications. We received 12 research papers in the research fields.This special issue includes 7 high-quality peer-reviewed papers, where five papers are related to variational inequalities and the other two papers are regarding Fourier transform and satellite data transmission scheduling problems. The aim of this special issue has been to present the newest and generalized coverage of the fundamental and constructive ideas, concepts, and important issues in the accepted original research articles as well as comprehensive review articles stimulating the continuing efforts to numerical analysis for variational inequality problems. In the paper by Z. B. Liu et al. a system of generalized variational inequalities has been set up for set-valued mappings by using surjectivity theorem of pseudomonotone and coercive operators. Convergence results for total asymptotically nonexpansive mappings are given by L. C. Zhao et al. in the set of hyperbolic spaces. Equilibrium problems andmonotone inclusion problems are studied by H. C. Wu and C. Z. Cheng. Moreover, generalized mixed equilibrium problems and fixed point problems are studied by P. Phuangphoo and P. Kumam. Provided by L. Xie et al. methods for variational inequalities are even applied to solve order-optimization problems in Banach spaces. Satellite data transmission scheduling problems are given by H. Xu et al. Fast Fourier transform is also studied by J. Huang et al.

An Energy-Efficient Self-Adaptive Duty Cycle MAC Protocol for Traffic-Dynamic Wireless Sensor Networks

A plenty of Medium Access Control (MAC) protocols deal with static traffics with low traffic load. The performance of these protocols drops significantly when network traffic become dynamic or in high traffic load. In this paper, we propose a new MAC protocol called Self-Adaptive Duty Cycle MAC (SEA-MAC) by introducing dual adaptive mechanisms: (1) An Adaptive Scheduling (AS) mechanism which makes the nodes’ active duration adaptive to variable traffic load, thus enabling SEA-MAC to resiliently schedule data transmission for the Sleep period. The algorithm is designated to schedule more data transmission in bursty and high traffic load, thus enabling rapid dissemination of data and reduction of latency. While under the light traffic load, nodes enter the Sleep mode timely, mitigating idle listening and saving energy. (2) A Self-Adaptive duty cycle mechanism which further adjusts the duty cycle and makes SEA-MAC adaptive to the dynamic traffic loads. When network experience with very low or very high traffic load, the protocol further adjusts duty cycle dynamically based on the traffic load, thus reducing inefficient duty cycle or reduce end-to-end delay. Experiment results show that the SEA-MAC is a great advancement compared with AS-MAC and RI-MAC protocols on the performance for unicast scenarios, especially under heavy unicast traffic load. SEA-MAC can reduce average and max end-to-end delay up to 50.90 and 68.20% respectively, lower energy consumption up to about 16.28%, and increase PDR up to about 16% compared with AS-MAC. SEA-MAC superiors to RI-MAC in average end-to-end delay by up to 80% and in maximum end-to-end delay up to 90% for all the traffic load in question. SEA-MAC outperforms RI-MAC significantly in average duty cycle under medium and heavy traffic load.

MAC2: A Multi-Hop Adaptive MAC Protocol with Packet Concatenation for Wireless Sensor Networks

Wireless sensor network MAC protocols switch radios off periodically, employing the so-called duty cycle mechanism, in order to conserve battery power that would otherwise be wasted by energy-costly idle listening. In order to minimize the various negative side-effects of the original scheme, especially on latency and throughput, various improvements have been proposed. In this paper, we introduce a new MAC protocol called MAC2(Multi-hop Adaptive with packet Concatenation-MAC) which combines three promising techniques into one protocol. Firstly, the idea to forward packets over multiple hops within one operational cycle as initially introduced in RMAC. Secondly, an adaptive method that adjusts the listening period according to traffic load minimizing idle listening. Thirdly, a packet concatenation scheme that not only increases throughput but also reduces power consumption that would otherwise be incurred by additional control packets. Furthermore, MAC2 incorporates the idea of scheduling data transmissions with minimum latency, thereby performing packet concatenation together with the multi-hop transmission mechanism in a most efficient way. We evaluated MAC2 using the prominent network simulator ns-2 and the results show that our protocol can outperform DW-MAC — a state of the art protocol both in terms of energy efficiency and throughput.

Approximation algorithms for minimum latency data aggregation in wireless sensor networks with directional antenna

Real-time data aggregation is one of the most important issues in wireless sensor networks. Using directional antenna to transmit data can save energy and reduce interference. In this paper, we study the minimum latency data aggregation problem with the given two directional antenna models (the steering beam and the switch beam) under protocol interference model. We propose an approximation directional data aggregation algorithm to schedule data transmissions under two directional antenna models, respectively. At last, we evaluate the proposed schedule algorithms through simulations, and simulation results show that the proposed schedule’s latency is close to the depth of BFS tree, which is the lower bound of schedule latency, and the proposed schedules achieve extremely good performance.

On max–min fair flow optimization in wireless mesh networks

The paper is devoted to modeling wireless mesh networks (WMN) through mixed-integer programming (MIP) formulations that allow to precisely characterize the link data rate capacity and transmission scheduling using the notion of time slots. Such MIP models are formulated for several cases of the modulation and coding schemes (MCS) assignment. We present a general way of solving the max–min fairness (MMF) traffic objective for WMN using the formulated capacity models. Thus the paper combines WMN radio link modeling with a non-standard way of dealing with uncertain traffic, a combination that has not, to our knowledge, been treated so far by exact optimization models. We discuss several ways, including a method based on the so called compatible or independent sets, of solving the arising MIP problems. We also present an extensive numerical study that illustrates the running time efficiency of different solution approaches, and the influence of the MCS selection options and the number of time slots on traffic performance of a WMN. Exact joint optimization modeling of the WMN capacity and the MMF traffic objectives forms the main contribution of the paper.

Throughput Optimization in High Speed Downlink Packet Access (HSDPA)

In this paper, we investigate single user throughput optimization in High Speed Downlink Packet Access (HSDPA). Specifically, we propose offline and online optimization algorithms which adjust the Channel Quality Indicator (CQI) used by the network for scheduling of data transmission. In the offline algorithm, a given target block error rate (BLER) is achieved by adjusting CQI based on ACK/NAK history. By sweeping through different target BLERs, we can find the throughput optimal BLER offline. This algorithm could be used not only to optimize throughput but also to enable fair resource allocation among multiple users in HSDPA. In the online algorithm, the CQI offset is adapted using an estimated short term throughput gradient without the need for a target BLER. An adaptive stepsize mechanism is proposed to track temporal variation of the environment. Convergence behavior of both algorithms is analyzed. The part of the analysis that deals with constant step size gradient algorithm may be applied to other stochastic optimization techniques. The convergence analysis is confirmed by our simulations. Simulation results also yield valuable insights on the value of optimal BLER target. Both offline and online algorithms are shown to yield up to 25% of throughput improvement over the conventional approach of targeting 10% BLER.

Crosstalk-Preventing Scheduling in Single- and Two-Stage AWG-Based Cell Switches

Array waveguide grating (AWG)-based optical switching fabrics are receiving increasing attention due to their simplicity and good performance. However, AWGs are affected by coherent crosstalk that can significantly impair system operation when the same wavelength is used simultaneously on several input ports. To permit large port counts in a N × N AWG, a possible solution is to schedule data transmissions across the AWG preventing switch configurations that generate large crosstalk. We study the properties and the existence conditions of switch configurations able to control coherent crosstalk. The presented results show that, by running a properly constrained scheduling algorithm to avoid or minimize crosstalk, it is possible to operate an AWG-based switch with large port counts without significant performance degradation.

Downlink data transmission scheduling algorithms in wireless networks

The problem of downlink data transmission scheduling in wireless networks is studied. It is pointed out that every downlink data transmission scheduling algorithm must have two components to solve the two subproblems of power assignment and transmission scheduling. Two types of downlink data transmission scheduling algorithms are proposed. In the first type, power assignment is performed before transmission scheduling. In the second type, power assignment is performed after transmission scheduling. The performance of two algorithms of the first type which use the equal power allocation method are analyzed. It is shown that both algorithms exhibit excellent worst-case performance and asymptotically optimal average-case performance under the condition that the total transmission power is equally allocated to the channels. In general, both algorithms exhibit excellent average-case performance. It is demonstrated that two algorithms of the second type perform better than the two algorithms of the first type due to the equal time power allocation method. Furthermore, the performance of our algorithms are very close to the optimal and the room for further performance improvement is very limited. It is shown that all the above algorithms can be extended to schedule downlink data transmissions with parallel channels. It is also shown that the simple sequential scheduling algorithm is optimal if the total transmission power is equally allocated to the channels. As an extra contribution, an M/G/1 queueing model for the FCFS queueing discipline is established, and it is observed that increasing the number of channels has more impact on the reduction of the average response time than increasing the total transmission power.

Performance Analysis of Coordinated Random Beamforming Technique in Multi-cell Environments

For multi-cell environments, coordinated random beamforming technique in multiuser MIMO(multiple-input multiple-output) broadcast channel is considered. In order to mitigate severe interference at receivers, the multi-cell environments might require complex transmitter and receiver design because the scheduler decision based on full channel state information (CSI) in one cell must be intertwined with decision made by other cells' CSI. With limited CSI, however, this paper considers a scheme of randomizing transmitters' beamforming but being coordinated with other cell transmitters. The transmitters in each cell share random beamforming patterns and schedule data transmission within coherent scheduling period. The corandomized beams allow the users to be selected with the highest SINRs even in multi-cell environments. We analyze the performance of the proposed scheme. And numerical results show that the scheme achieves better performance than the conventional random beamforming when applying to multi-cell environments.

Radio resources allocation for decentrally controlled relay stations

To enhance throughput and to extend coverage of wireless networks based on IEEE 802.16 standards, relay stations can be implemented. The crucial point influencing the overall system performance is allocation of appropriate amount of resources to individual relay stations depending on their current needs. If resources are not allocated properly, relay stations can experience congestion situations resulting in system throughput decrease and packet delays increase. If the base station is enhanced purely by centrally controlled relay stations, the base station itself is able to dynamically schedule data transmissions of its relays. Nevertheless, decentrally controlled relays schedule data for its users on its own and the base station is no longer capable to allocate the right amount of radio resources for them. The decentrally controlled relays have to ask for radio resources by means of existing scheduling services defined in IEEE 802.16 standard. While utilization of the conventional unsolicited grant service decreases the system capacity, the use of real-time polling or extended real-time polling services results in higher signaling overhead and longer packet delays. In order to maximize system throughput and to minimize packet delays and signaling overhead, we suggest a mechanism that pre-allocates to decentrally controlled relay stations a certain amount of default radio resources while the remaining resources are dynamically shared. The obtained results show that for low traffic load, overhead and packet delays are significantly smaller as relays do not have to ask base stations for resources. On the other hand, at heavy traffic load the system throughput slightly decreases whereas packet delays and signaling overhead are still significantly smaller.

An energy-efficient and low-latency MAC protocol with Adaptive Scheduling for multi-hop wireless sensor networks

Medium access control (MAC) protocols play a crucial role in energy efficiency, latency reduction for sensor networks. Although some existing MAC protocols have achieved certain performance improvements, there are great potentials for further performance enhancement. In this paper, we propose a new MAC protocol called AS-MAC by introducing an Adaptive Scheduling (AS) period into the operational cycle within which the nodes’ active duration is made adaptive to variable traffic load thus enabling AS-MAC to resiliently schedule data transmission in the sleep period. The algorithm is designated to schedule more data transmission in bursty and high traffic load, thus enabling rapid dissemination of data and reduction of latency. While under the light traffic load, nodes enter the sleep mode timely, mitigating idle listening and saving energy. Experiment results show that the proposed protocol is a great advancement of some existing protocols on the performance for both unicast and broadcast scenarios. Especially, under heavy unicast traffic load, AS-MAC can reduce end-to-end delay by about 65% and lowers energy consumption by about 40% compared to DW-MAC, while keeping nearly 100% packet delivery ratio.

Control-based scheduling with QoS support for vehicle to infrastructure communications

This article is focused on data transmission scheduling in V2I communications, where a central station, the roadside beacon, decides how to allocate system resources among the vehicles under coverage. We consider non-safety applications whose commercial appeal is expected to accelerate the deployment of VANETs. In this case the main objective is to deliver as much information as possible during the connection lifetime of the vehicles, which is limited by their speed and the length of the road sections under coverage. In this environment the contention free poll-based access mechanism of the 802.11e standard included in current VANET specifications is especially suitable. The design of a scheduling mechanism is addressed in this article from a control theory point of view with the additional novelty of using an optimal control formulation comprising resource constraints. This design strategy allows QoS differentiation, assuring a fixed amount of bandwidth for each QoS class. The resulting algorithm not only maximizes the amount of data delivered, but also reduces performance differences between users traveling along different roads.