Showing papers on "Transmission delay published in 2016"

Optimal Workload Allocation in Fog-Cloud Computing Toward Balanced Delay and Power Consumption

Abstract: Mobile users typically have high demand on localized and location-based information services. To always retrieve the localized data from the remote cloud, however, tends to be inefficient, which motivates fog computing. The fog computing, also known as edge computing, extends cloud computing by deploying localized computing facilities at the premise of users, which prestores cloud data and distributes to mobile users with fast-rate local connections. As such, fog computing introduces an intermediate fog layer between mobile users and cloud, and complements cloud computing toward low-latency high-rate services to mobile users. In this fundamental framework, it is important to study the interplay and cooperation between the edge (fog) and the core (cloud). In this paper, the tradeoff between power consumption and transmission delay in the fog-cloud computing system is investigated. We formulate a workload allocation problem which suggests the optimal workload allocations between fog and cloud toward the minimal power consumption with the constrained service delay. The problem is then tackled using an approximate approach by decomposing the primal problem into three subproblems of corresponding subsystems, which can be, respectively, solved. Finally, based on simulations and numerical results, we show that by sacrificing modest computation resources to save communication bandwidth and reduce transmission latency, fog computing can significantly improve the performance of cloud computing.

Platoon based Cooperative Driving Model with Consideration of Realistic Inter-vehicle Communication

Abstract: Recent developments of information and communication technologies (ICT) have enabled vehicles to timely communicate with each other through wireless technologies, which will form future (intelligent) traffic systems (ITS) consisting of so-called connected vehicles. Cooperative driving with the connected vehicles is regarded as a promising driving pattern to significantly improve transportation efficiency and traffic safety. Nevertheless, unreliable vehicular communications also introduce packet loss and transmission delay when vehicular kinetic information or control commands are disseminated among vehicles, which brings more challenges in the system modeling and optimization. Currently, no data has been yet available for the calibration and validation of a model for ITS, and most research has been only conducted for a theoretical point of view. Along this line, this paper focuses on the (theoretical) development of a more general (microscopic) traffic model which enables the cooperative driving behavior via a so-called inter-vehicle communication (IVC). To this end, the authors design a consensus-based controller for the cooperative driving system (CDS) considering (intelligent) traffic flow that consists of many platoons moving together. More specifically, the IEEE 802.11p, the de facto vehicular networking standard required to support ITS applications, is selected as the IVC protocols of the CDS, in order to investigate how the vehicular communications affect the features of intelligent traffic flow. This study essentially explores the relationship between IVC and cooperative driving, which can be exploited as the reference for the CDS optimization and design.

Enhanced cooperative car-following traffic model with the combination of V2V and V2I communication

Abstract: Vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication are emerging components of intelligent transport systems (ITS) based on which vehicles can drive in a cooperative way and, hence, significantly improve traffic flow efficiency. However, due to the high vehicle mobility, the unreliable vehicular communications such as packet loss and transmission delay can impair the performance of the cooperative driving system (CDS). In addition, the downstream traffic information collected by roadside sensors in the V2I communication may introduce measurement errors, which also affect the performance of the CDS. The goal of this paper is to bridge the gap between traffic flow modelling and communication approaches in order to build up better cooperative traffic systems. To this end, we aim to develop an enhanced cooperative microscopic (car-following) traffic model considering V2V and V2I communication (or V2X for short), and investigate how vehicular communications affect the vehicle cooperative driving, especially in traffic disturbance scenarios. For these purposes, we design a novel consensus-based vehicle control algorithm for the CDS, in which not only the local traffic flow stability is guaranteed, but also the shock waves are supposed to be smoothed. The IEEE 802.11p, the defacto vehicular networking standard, is selected as the communication protocols, and the roadside sensors are deployed to collect the average speed in the targeted area as the downstream traffic reference. Specifically, the imperfections of vehicular communication as well as the measured information noise are taken into account. Numerical results show the efficiency of the proposed scheme. This paper attempts to theoretically investigate the relationship between vehicular communications and cooperative driving, which is needed for the future deployment of both connected vehicles and infrastructure (i.e. V2X).

A Joint Time Synchronization and Localization Design for Mobile Underwater Sensor Networks

Abstract: Time synchronization and localization are basic services in a sensor network system. Although they often depend on each other, they are usually tackled independently. In this work, we investigate the time synchronization and localization problems in underwater sensor networks, where more challenges are introduced because of the unique characteristics of the water environment. These challenges include long propagation delay and transmission delay, low bandwidth, energy constraint, mobility, etc. We propose a joint solution for localization and time synchronization, in which the stratification effect of underwater medium is considered, so that the bias in the range estimates caused by assuming sound waves travel in straight lines in water environments is compensated. By combining time synchronization and localization, the accuracy of both are improved jointly. Additionally, an advanced tracking algorithm interactive multiple model (IMM) is adopted to improve the accuracy of localization in the mobile case. Furthermore, by combining both services, the number of required exchanged messages is significantly reduced, which saves on energy consumption. Simulation results show that both services are improved and benefit from this scheme.

Data-Based Predictive Control for Networked Nonlinear Systems With Network-Induced Delay and Packet Dropout

Abstract: This paper addresses the data-based networked control problem for a class of nonlinear systems. Network communication constraints, such as network-induced delay, packet disorder, and packet dropout in both the feedback and forward channels, are considered and further treated as the round-trip time (RTT) delay that is redefined. By using the packet-based transmission mechanism and the model-free adaptive control algorithm, a data-based networked predictive control method is proposed to actively compensate for the random RTT delay. The proposed method does not require any information on the plant model and depends only on the input and output data of the plant. A simple and explicit sufficient condition, which is related to the upper bound of the RTT delays, is derived for the stability of the closed-loop system. Additionally, a zero steady-state output tracking error can be achieved for a step reference input. The effectiveness of the proposed method is demonstrated via simulation and experimental results.

Immune Multipath Reliable Transmission with Fault Tolerance in Wireless Sensor Networks

Abstract: Transmission reliability is one of the most important metrics to evaluate the performance of wireless sensor networks. For the fault of nodes or links affecting the stability and reliability of network, Immune based multipath transmission algorithm is proposed. For giving the consideration to the factors of transmission delay and energy consumption beside the hops/distance, immune based multiple paths can be quickly established from the source node to the destination node. Metrics of data receiving rate are adopted to evaluate the performance of multipath transmission. The result shows good performance of fault tolerance, stability and reliability of data transmission.

Energy-Efficient Packet Scheduling with Finite Blocklength Codes: Convexity Analysis and Efficient Algorithms

Abstract: This paper considers an energy-efficient packet scheduling problem over quasi-static block fading channels. The goal is to minimize the total energy for transmitting a sequence of data packets under the first-in-first-out rule and strict delay constraints. Conventionally, such design problem is studied under the assumption that the packet transmission rate can be characterized by the classical Shannon capacity formula, which, however, may provide inaccurate energy consumption estimation, especially when the code blocklength is finite. In this paper, we formulate a new energy-efficient packet scheduling problem by adopting a recently developed channel capacity formula for finite blocklength codes. The newly formulated problem is fundamentally more challenging to solve than the traditional one because the transmission energy function under the new channel capacity formula neither can be expressed in closed form nor possesses desirable monotonicity and convexity in general. We analyze conditions on the code blocklength for which the transmission energy function is monotonic and convex. Based on these properties, we develop efficient offline packet scheduling algorithms as well as a rolling-window based online algorithm for real-time packet scheduling. Simulation results demonstrate not only the efficacy of the proposed algorithms but also the fact that the traditional design using the Shannon capacity formula can considerably underestimate the transmission energy for reliable communications.

Traffic Management for Emergency Vehicle Priority Based on Visual Sensing

Abstract: Vehicular traffic is endlessly increasing everywhere in the world and can cause terrible traffic congestion at intersections. Most of the traffic lights today feature a fixed green light sequence, therefore the green light sequence is determined without taking the presence of the emergency vehicles into account. Therefore, emergency vehicles such as ambulances, police cars, fire engines, etc. stuck in a traffic jam and delayed in reaching their destination can lead to loss of property and valuable lives. This paper presents an approach to schedule emergency vehicles in traffic. The approach combines the measurement of the distance between the emergency vehicle and an intersection using visual sensing methods, vehicle counting and time sensitive alert transmission within the sensor network. The distance between the emergency vehicle and the intersection is calculated for comparison using Euclidean distance, Manhattan distance and Canberra distance techniques. The experimental results have shown that the Euclidean distance outperforms other distance measurement techniques. Along with visual sensing techniques to collect emergency vehicle information, it is very important to have a Medium Access Control (MAC) protocol to deliver the emergency vehicle information to the Traffic Management Center (TMC) with less delay. Then only the emergency vehicle is quickly served and can reach the destination in time. In this paper, we have also investigated the MAC layer in WSNs to prioritize the emergency vehicle data and to reduce the transmission delay for emergency messages. We have modified the medium access procedure used in standard IEEE 802.11p with PE-MAC protocol, which is a new back off selection and contention window adjustment scheme to achieve low broadcast delay for emergency messages. A VANET model for the UTMS is developed and simulated in NS-2. The performance of the standard IEEE 802.11p and the proposed PE-MAC is analysed in detail. The NS-2 simulation results have shown that the PE-MAC outperforms the IEEE 802.11p in terms of average end-to-end delay, throughput and energy consumption. The performance evaluation results have proven that the proposed PE-MAC prioritizes the emergency vehicle data and delivers the emergency messages to the TMC with less delay compared to the IEEE 802.11p. The transmission delay of the proposed PE-MAC is also compared with the standard IEEE 802.15.4, and Enhanced Back-off Selection scheme for IEEE 802.15.4 protocol [EBSS, an existing protocol to ensure fast transmission of the detected events on the road towards the TMC] and the comparative results have proven the effectiveness of the PE-MAC over them. Furthermore, this research work will provide an insight into the design of an intelligent urban traffic management system for the effective management of emergency vehicles and will help to save lives and property.

Cross-layer scheduler for video streaming over MPTCP

Abstract: Transport protocols that can exploit multiple paths, especially MPTCP, do not match the requirements of video streaming: high average transmission delay, too strict reliability, and frequent head-of-line phenomenons resulting in abrupt throughput drops. In this paper, we address this mismatch by introducing a cross-layer scheduler, which leverages information from both application and transport layers to re-order the transmission of data and prioritize the most significant parts of the video. Our objective is to maximize the amount of video data that is received in time at the client. We show that current technologies enable the implementation of this cross-layer scheduler without much overhead. We then demonstrate the validity of our approach by studying the performance of an optimal cross-layer scheduler. The gap between the performance of the traditional scheduler versus the optimal scheduler justifies our motivation to implement a cross-layer scheduler in practice. We propose one implementation with basic cross-layer awareness. To evaluate the performance of our proposal, we aggregate a dataset of real MPTCP sessions and we use video stream encoded with HEVC. Our results show that our cross-layer proposal outperforms the traditional scheduler. Viewers not only benefit from the inherent advantages of using MPTCP (such as a better resilience to path failure) but also get a better QoE compared to the traditional scheduler.

Hypergraph-Based Wireless Distributed Storage Optimization for Cellular D2D Underlays

Abstract: Distributed storage that leverages cellular device-to-device (D2D) underlay has attracted rising research interest due to its potential to offload cellular traffic, improve spectral efficiency and energy efficiency, and reduce transmission delay. This paper investigates the overall transmission cost minimization problem based on a content encoding strategy to download a new content item or repair a lost content item in D2D-based distributed storage systems while guaranteeing users’ quality of service. In addition to the optimization of the coding parameters, the cost minimization problem also considers the distribution of content items, the selection of content helpers for each content requester, and the spectrum reuse for establishing D2D links in between. Formulating a hypergraph-based three-dimensional matching problem among content helpers, requesters, and cellular user resources, we present a local search based algorithm with low complexity for optimization. Numerical results demonstrate the performance and the effectiveness of our proposed approach.

Secure Transmission Design for Cognitive Radio Networks With Poisson Distributed Eavesdroppers

Abstract: In this paper, we study physical layer security in an underlay cognitive radio (CR) network. We consider the problem of secure communication between a secondary transmitter–receiver pair in the presence of randomly distributed eavesdroppers under an interference constraint set by the primary user. For different channel knowledge assumptions at the transmitter, we design four transmission protocols to achieve the secure transmission in the CR network. We give a comprehensive performance analysis for each protocol in terms of transmission delay, security, reliability, and the overall secrecy throughput. Furthermore, we determine the optimal design parameter for each transmission protocol by solving the optimization problem of maximizing the secrecy throughput subject to both security and reliability constraints. Numerical results illustrate the performance comparison between different transmission protocols.

Synchronization of hybrid-coupled delayed dynamical networks via aperiodically intermittent pinning control

Abstract: In this paper, we concern the exponential synchronization problem for hybrid-coupled delayed dynamical networks via pinning aperiodically intermittent control. Different from previous works, the delayed coupling term considered here contains the transmission delay and self-feedback delay, and the intermittent control can be aperiodic. By establishing a new differential inequality and constructing Lyapunov function, several useful criteria are derived analytically to realise exponential synchronization for both free time delay (there is no restriction imposed on the delay and the control (and/or rest) width) and small time delay (the delay is smaller than the minimum of control width). Moreover, the detail of pinning and aperiodically intermittent control strategy are provided. Finally, a numerical example is given to demonstrate the validness of the proposed scheme.

QoS Differential Scheduling in Cognitive-Radio-Based Smart Grid Networks: An Adaptive Dynamic Programming Approach

Abstract: As the next-generation power grid, smart grid will be integrated with a variety of novel communication technologies to support the explosive data traffic and the diverse requirements of quality of service (QoS). Cognitive radio (CR), which has the favorable ability to improve the spectrum utilization, provides an efficient and reliable solution for smart grid communications networks. In this paper, we study the QoS differential scheduling problem in the CR-based smart grid communications networks. The scheduler is responsible for managing the spectrum resources and arranging the data transmissions of smart grid users (SGUs). To guarantee the differential QoS, the SGUs are assigned to have different priorities according to their roles and their current situations in the smart grid. Based on the QoS-aware priority policy, the scheduler adjusts the channels allocation to minimize the transmission delay of SGUs. The entire transmission scheduling problem is formulated as a semi-Markov decision process and solved by the methodology of adaptive dynamic programming. A heuristic dynamic programming (HDP) architecture is established for the scheduling problem. By the online network training, the HDP can learn from the activities of primary users and SGUs, and adjust the scheduling decision to achieve the purpose of transmission delay minimization. Simulation results illustrate that the proposed priority policy ensures the low transmission delay of high priority SGUs. In addition, the emergency data transmission delay is also reduced to a significantly low level, guaranteeing the differential QoS in smart grid.

Historical Spectrum Sensing Data Mining for Cognitive Radio Enabled Vehicular Ad-Hoc Networks

Abstract: In vehicular ad-hoc network (VANET), the reliability of communication is associated with driving safety. However, research shows that the safety-message transmission in VANET may be congested under some urgent communication cases. More spectrum resource is an effective way to solve transmission congestion. Hence, we introduce cognitive radio (CR) enabled VANET (CR-VANET), where CR device can detect possible idle spectrum for VANET communications and assist to timely broadcast safety-message. Given high-speed mobility of vehicles and dynamically-changing availability of channels, a novel prediction algorithm is proposed to pick out the channel with the greatest probability of availability, which can meet the quality of service (QoS) requirement of urgent communications and effectively avoid conflict with licensed users. Specifically, the spatiotemporal correlations among historical spectrum sensing data are exploited to form prior knowledge of channel availability probability, and Bayesian inference is used to derive posterior probability of channel availability. Comparing with other spectrum detection methods, the proposed algorithm has more than 8 percent detection performance improvement at false alarm probability 0.2, and thus can avoid access conflict with licensed users dramatically. Furthermore, the proposed algorithm always has larger packet reception probability (PRP) and lower transmission delay compared with conventional VANET broadcasting. Hence, the proposed algorithm can improve reliability of safety-message transmission and enhance driving safety significantly.

FFSC: An Energy Efficiency Communications Approach for Delay Minimizing in Internet of Things

Abstract: It is desirable for alarm packets to be forwarded to the sink as quickly as possible in wireless sensor networks. In this paper, we initially analyze the theory of the relationships between network configurations and network lifetime as well as transmission delay. Then, we propose an approximate optimization approach to minimize the end-to-end delay with a reduced complexity of configuration under the condition that the network lifetime remains greater than the specified target value. A local forwarding approach named Fast data collection for nodes Far away from the sink and slow data collection for nodes Close to the Sink (FFSC) is proposed. This approach is energy efficient. Moreover, it can further reduce the end-to-end delay. Both the comprehensive theoretical analysis and the experimental results indicate that the performance of FFSC is better than the methods proposed by previous studies. Relative to the direct forwarding strategy, the FFSC approach can reduce the delay by 7.56%–23.16% and increase the lifetime by more than 25%. It can also increase the energy efficiency as much as 18.99%. Relative to the single fixed threshold strategy, the FFSC approach can reduce the delay by 4.16%–9.79% and increase the energy efficiency by 19.28% while still guaranteeing the same lifetime as those previous methods.

NDN-GSM-R: a novel high-speed railway communication system via Named Data Networking

Abstract: To keep up with the rapid development of railway and meet the high demand for communication business in China, Global System for Mobile Communications-Railway (GSM-R) based on General Packet Radio Service (GPRS) ahead of Europe has been developed. However, the current data communication mode of GPRS using TCP/IP has some disadvantages, such as poor mobility, lack of security etc. For this reason, there are some problems for GSM-R, like handover, which makes communication service quality undesirable. Named Data Networking focuses on named data, adopts data-facing communication mode, and does not care where the contents are stored but the contents themselves. It can effectively solve the problems caused by TCP/IP. In this paper, a new high-speed railway communication system with Named Data Networking (NDN) named NDN-GSM-R is proposed. Two simulations, called transmission interference time and end-to-end transmission delay of NDN-GSM-R, have been conducted. The simulation results show that NDN-GSM-R has better performance in high-speed mobile communication environment and can make up the insufficiency of the current GSM-R based on TCP/IP framework.

A review on high-resolution CMOS delay lines: towards sub-picosecond jitter performance.

Abstract: A review on CMOS delay lines with a focus on the most frequently used techniques for high-resolution delay step is presented. The primary types, specifications, delay circuits, and operating principles are presented. The delay circuits reported in this paper are used for delaying digital inputs and clock signals. The most common analog and digitally-controlled delay elements topologies are presented, focusing on the main delay-tuning strategies. IC variables, namely, process, supply voltage, temperature, and noise sources that affect delay resolution through timing jitter are discussed. The design specifications of these delay elements are also discussed and compared for the common delay line circuits. As a result, the main findings of this paper are highlighting and discussing the followings: the most efficient high-resolution delay line techniques, the trade-off challenge found between CMOS delay lines designed using either analog or digitally-controlled delay elements, the trade-off challenge between delay resolution and delay range and the proposed solutions for this challenge, and how CMOS technology scaling can affect the performance of CMOS delay lines. Moreover, the current trends and efforts used in order to generate output delayed signal with low jitter in the sub-picosecond range are presented.

Communication time delay estimation for load frequency control in two-area power system

Abstract: Due to increased size and complexity of power system network, the stability and load frequency control (LFC) is of serious concern in a wide area monitoring system (WAMS) having obtained signals from phasor measurement unit (PMU). The quality of services (QoS) for communication infrastructure in terms of signal delay, packet loss probability, queue length, throughput is very important and must be considered carefully in the WAMS based thermal power system. However, very few studies have been presented that includes QoS for communication infrastructure in load frequency control (LFC) of power system. So this paper presents LFC for two area thermal power system based on estimated time delay and packet loss probability using the Markovian approach. The delay and packet loss probability are modeled by different math functions. Normally, frequency deviation signal is transmitted from remote terminal unit (RTU) to control center and from control center to individual control unit of plants. The delay incurred is located in the forward loop of PSO based PI/PID controller in the form of transport delay. To verify the efficacy of controller performance, the estimated constant delay and time varying delay are applied to the controller in the two area thermal-thermal power system with and without governor dead band (GDB) and generation rate constraints (GRC) for various loads conditions. The study is further demonstrated for time delay, being compensated by 2nd order Pade approximation. The results show that frequency deviation is minimum in terms of stability and transient response.

Delay and Reliability Tradeoffs in Heterogeneous Cellular Networks

Abstract: Network densification is one of the dominant evolutions to increase network capacity toward future cellular networks. However, the complex and random interference in the resultant interference-limited heterogeneous cellular networks (HCN) may deteriorate packet transmission reliability and increase transmission delay, which are essential performance metrics for system design in HCN. By modeling the locations of base stations (BSs) as superimposed of independent Poisson point process, we propose an analytical framework to investigate delay and reliability tradeoffs in HCN in terms of timely throughput and local delay. In our analysis, we take the BS activity and temporal correlation of transmissions into consideration, both having significant effects on the performances. The effects of mobility, BS density, and association bias factor are evaluated through numerical results.

Coalition Formation for Cooperative Service-Based Message Sharing in Vehicular Ad Hoc Networks

Abstract: Reliable message delivery is a challenging task in Vehicular Ad Hoc Networks (VANETs). Current literature on VANETs generalize all messages and use the same strategy to transmit them. In this paper, we model the cooperative service-based message sharing problem in VANETs as a coalition formation game among nodes. Nodes associate with a coalition based on the type of service-message they process. In the proposed model, service-messages are distinguished from one another by their types. Nodes process different types of service-messages and form a coalition based on the type of messages they process at that time. Some nodes within a coalition can work as a relay, which is modeled as a network formation game to select exactly one relay among a group of potential relay nodes to improve efficiency of the network in terms of improved packet reception rate and reducing transmission delay. The nodes form independent disjoint coalitions and tree structure is formed with the relay nodes within a coalition by using the proposed algorithm, COMES. Simulation results show that COMES, which allows nodes to form independent coalitions among themselves, improves the network performance in terms of incentive received by players by at least $40$ percent compared to a non-cooperative function.

Trading Delay for Distortion in One-Way Video Communication Over the Internet

Abstract: We study the problem of one-way video communication in a single-source, multiple-destination scenario over the lossy Internet. Forward error correction (FEC) coding is commonly adopted for data protection in implementing loss-resilient video transmission systems. However, the burst packet losses over the Internet frequently degrade FEC performance and induce video quality deteriorations. To address the challenging problem, we propose a novel transmission scheme dubbed trading delay for distortion (TELFORD) that includes three components: 1) adaptive multidestination status estimation; 2) delay-constrained transmission rate assignment; and 3) differentiated FEC packet spreading. We analytically formulate and solve the problem of FEC packet allocation and scheduling to minimize the end-to-end video distortion. The proposed TELFORD is able to cope with multiple-destination scheduling separately. We conduct performance evaluation through semiphysical emulations in Exata using real-time H.264 video streaming. Experimental results show that TELFORD outperforms existing error control transmission schemes in improving the video peak signal-to-noise ratio and mitigating packet transmission impairments.

Energy-Aware Service Function Placement for Service Function Chaining in Data Centers

Abstract: Nowadays, data centers deploy a large number of servers and network devices to provide various service functions (e.g. firewalls, deep packet inspection, content caches, WAN optimizers, etc.) and sufficient network connection. Most traffic in data centers is subject to treatment by multiple service functions (SFs) which form an ordered service function chain (SFC). In this paper, we study the energy-aware service function placement problem for SFC in data centers. By considering the computing, bandwidth resources constrains and the power models both in servers and switches, a new service function placement algorithm Merge-RD is proposed to save the energy consumption in data centers. The simulation results indicate that the Merge-RD can effectively reduce the energy consumption and average transmission delay in data center compared with some existing service function placement algorithms while guaranteeing the packet delivery ratio at a high level.

QoS-Constrained Energy Efficiency of Cooperative ARQ in Multiple DF Relay Systems

Abstract: In this paper, we study the higher layer performance as well as the “throughput, delay, energy consumption” tradeoff problem for multirelay-assisted cooperative automatic repeat request (C-ARQ) protocols. We study a practical scenario where only the average channel state information (CSI) is available at the source and relays. We consider four multirelay C-ARQ protocols and derive closed-form expressions for the transmission delay distribution, the energy consumption, and the higher layer queuing performance. Furthermore, we analyze the quality of service (QoS)-constrained energy efficiency performances of the protocols. Our analysis is validated by simulations. In addition, we evaluate the system performance under these C-ARQ protocols and for different topologies. We conclude several guidelines for the design of efficient C-ARQ protocols. Finally, a simple extension of the studied C-ARQ protocols is proposed, which improves the QoS-constrained energy efficiency by 4%.

A Residual Energy Aware Schedule Scheme for WSNs Employing Adjustable Awake/Sleep Duty Cycle

Abstract: In this paper, we systematically analyze the relationship among expected energy expenditure, packet loss ratio, end to end delay and lifetime of wireless sensor networks. Firstly, we demonstrate that optimized duty cycle schemes can achieve a trade-off among the lifetime of network, transmission delay and packet loss ratio. Then, a residual energy aware with adjustable duty cycle scheme (READC) is proposed based on the fact that energy consumption is higher in the region near sink, while it is lower in the area far away from the sink. In READC scheme, sensor nodes near sink adopt appropriate duty cycles to meet with the requirement of forwarding data, while the higher duty cycles are needed in far-sink area. In this way, the residual energy of the nodes can be fully used. Meanwhile, transmission delay and packet loss ratio can also be reduced. Through our extensive theoretical analysis and simulation study, we demonstrate that compared with fixed duty cycle schemes, the READC scheme can reduce the transmission delay from 10.1 to 40.35 % and the packet loss ratio from 7.7 to 71.63 % without impacting the lifetime of network.

Joint Optimization of Transmission Power Level and Packet Size for WSN Lifetime Maximization

Abstract: In pursuit of better energy efficiency and enhanced network lifetime in wireless sensor networks (WSNs), two crucial factors are data packet size and transmission power level. On one hand, smaller packet size reduces the overall impact of bit error rates on packet loss. However, the consequence of smaller packet size is fragmentation into more data packets and thereby dissipation of increased energy. Hence, there emerges a delicate engineering tradeoff in deciding the data packet size, where both low and high data packet size decisions lead to certain energy inefficiency issues. On the other hand, increasing transmission power level decreases packet loss probability, which is another decision variable to optimize for maximizing network lifetime. Joint consideration of these two factors exacerbates the complexity of the optimization problem for the objective of the network lifetime maximization. In this paper, we develop a realistic WSN link layer model built on top of the empirically verified energy dissipation characteristics of Mica2 motes and WSN channel models. We make use of the aforementioned link layer model to design a novel mixed integer programming (MIP) framework for the joint optimization of transmission power level and data packet size to take up the challenge introduced above. Numerical evaluations of the MIP framework with the analysis of the results over a large parameter space are performed to characterize the effects of joint optimization of packet size and power level on WSN lifetime.