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... The energy of a node is mainly consumed in sensing and transmission/reception by radio [2][3][4]. The radio not only consumes power when transmitting and receiving, but also when listening. ...
... The radio not only consumes power when transmitting and receiving, but also when listening. Steam and Katz [2] show that the ratio of energy consumption during idle:receive:transmit operations is 1:1.05:1.4, while more recent studies show that the ratio is 1:2:2.5 [3] or 1:1.2:1.7 [4]. ...
In wireless sensor networks, nonuniform communication load across a network often leads to the problem of energy holes or hot spots, i.e. nodes nearer high activity regions deplete their energy much faster than nodes elsewhere. This may partition the network into unreachable segments and thus adversely affect network lifetime. The problem is more acute in random and sparsely deployed networks. Therefore, we propose a deployment strategy that, using the least possible nodes, prolongs network lifetime by avoiding energy holes and also ensures full sensing and communication coverage. The scheme handles the energy imbalance by selecting an appropriate set of communication and sensing ranges for each node based on effective load on that node. After adjusting these ranges, nodes are strategically placed at locations where their energy drains uniformly and thus network lifetime is prolonged. The approach is verified analytically and validated through ns-2 based simulation experiments. The results reveal significant improvements over existing schemes.
... Previous research shows that the idle:receive:send power ratios for a sensor can be typically 1:1.05:1.4 [2]. That means a receiving node may consume close to 95% of the energy needed to transmit. ...
... The idle-listening phenomenon occurs when the sensor nodes continue to listen although no data is expected to arrive[1]. Previous research shows that the idle:receive:send power ratios for a sensor can be typically 1:1.05:1.4[2]. That means a receiving node may consume close to 95% of the energy needed to transmit. ...
Wireless sensor networks (WSN) with a single data collection node or ‘sink’ play major role in data acquisition (DAQ) and control systems such as smart buildings. These ‘many-to-one’ networks have unique challenges in addition to regular energy concern issues. For example, nodes closer to the sink experience high traffic and drain faster. In this paper, a priority based, distributed, quasi-planned Medium Access Control (MAC) scheduling algorithm is suggested for such network architectures. The proposed Quorum-Pattern-Priority (QPP) MAC approach reduces energy wastage due to idle-listening, overhearing and transmission of unnecessary overhead. The algorithm is tested with multiple sensor classes each with a different data trans-mission pattern. The proposed protocol shows significantly low energy consumption while providing almost ideal throughput for steady traffic. The algorithm also better handles varying traffic compared to many conventional fixed scheduling algorithms.
... Lorch reported that the energy use of a typical laptop computer is dominated by the backlight of the display, the disk and the processor [12] . Stemm et al. concluded that the network interface consumes at least the same amount of energy as the rest of the system (i.e. a Newton PDA) [25] . If the computer is able to receive messages from the network even when it is 'off', the energy consumption increases dramatically. ...
... The wireless network interface of a mobile computer consumes a significant fraction of the total power [25] . Measurements show that on typical applications like a web-browser or email , the energy consumed when the interface is on and idle is more than the cost of receiving packets. ...
Portable products are being used increasingly. Because these systems are battery powered, reducing power consumption is vital. In this report we give the properties of low-power design and techniques to exploit them on the architecture of the system. We focus on: minimizing capacitance, avoiding unnecessary and wasteful activity, and reducing voltage and frequency. We review energy reduction techniques in the architecture and design of a hand-held computer and the wireless communication system including error control, system decomposition, communication and MAC protocols, and low-power short range networks.
... The last major source is idle listening i.e. listening to receive possible traffic that has not been sent. The idle:receive ratio is measured from 1:2 (Kasten, 2002)to 1:1.05 (Stemm and Katz, 1997). According to (Ye et al., 2002) idle listening alone can consume 50%-100% of the energy required to actually receiving the message. ...
... The hard disk state model provides both the quantitative data and insight necessary to design an efficient power management system. Stemm et al. [21] studied two types of optimization (namely, transport-level and application-level) of network interfaces to decrease their energy consumption. Li et al. [22] performed a quantitative analysis of the costs and benefits of spinning down a disk drive as a power management technique. ...
Context: Information Technology consumes up to 10\% of the world's electricity generation, contributing to CO2 emissions and high energy costs. Data centers, particularly databases, use up to 23% of this energy. Therefore, building an energy-efficient (green) database engine could reduce energy consumption and CO2 emissions. Goal: To understand the factors driving databases' energy consumption and execution time throughout their evolution. Method: We conducted an empirical case study of energy consumption by two MySQL database engines, InnoDB and MyISAM, across 40 releases. We examined the relationships of four software metrics to energy consumption and execution time to determine which metrics reflect the greenness and performance of a database. Results: Our analysis shows that database engines' energy consumption and execution time increase as databases evolve. Moreover, the Lines of Code metric is correlated moderately to strongly with energy consumption and execution time in 88% of cases. Conclusions: Our findings provide insights to both practitioners and researchers. Database administrators may use them to select a fast, green release of the MySQL database engine. MySQL database-engine developers may use the software metric to assess products' greenness and performance. Researchers may use our findings to further develop new hypotheses or build models to predict greenness and performance of databases.
... There exist several causes of unwanted energy consumption in cognitive radio networks either by the cognitive radio user's behavior or unwanted energy consumed by the system itself. If a transceiver is idle during low traffic period, measurements show that when applications are turned on during that period, the energy consumption when the interface is turned while in idle mode is more than the energy expended when receiving packets [26]. Also, the inactive mode of the cognitive radio which is the period immediately before a transceiver goes into or out of the standby state after an inactive period can cause the transceiver to be in a high energy consuming mode unnecessarily for a substantial amount of time. ...
Energy efficiency in cognitive radio networks has
received lots of research attention lately due to the impact low
energy efficiency has on the design, implementation and
performance of the network. In this research, cognitive radio
network as regards to energy efficiency has been analyzed. The
importance of energy efficiency in cognitive radio networks and
sources of unnecessary energy consumption in the network is also
investigated. Ways in which higher energy efficiency in cognitive
radio networks can be achieved is also addressed by employing
suitable protocols, mechanisms and algorithm analyzed in the
article. These measures can bring about low energy consumption
amongst components in the network, improved sensing reliability
and better energy efficiency which in turn enhances the overall
network throughput
... 2) Energy per Packet: The energy consumed by a sensor node consists of two parts: energy spent on running the circuits P c and the transmission energy P t spent on communications. Since the circuit power consumption is independent of whether a node is transmitting or not[20], we only consider the transmission energy for evaluating the energy cost of a packet. The energy consumption for each transmission can be divided into two parts: the energy spent on channel reservation and recruiting, and the energy spent on data transmission, which also depends on the chosen threshold i (or ϕ(i)). ...
In wireless networks without nodes equipped with multiple antennas, cooperative Multiple Input Multiple Output (MIMO) transmissions may be used to harness diversity gains. In general, diversity gains are larger if more nodes are involved in the transmission. However, a transmission policy that maximizes the diversity gain or throughput need not maximize the stability region, since queues at the nodes may grow while waiting for a sufficient number of nodes to become available. To address this issue, this paper develops a mechanism for maximizing the throughput while reducing the energy consumption and maintaining queue stability. We develop a sufficient condition that ensures the throughput optimality of a stable transmission policy and then use it to design a distributed, dynamic threshold based Medium Access Control (MAC) protocol for cooperative MIMO transmissions. The MAC protocol requires only limited local information for its operation. Simulation results are provided to evaluate the performance of the proposed protocol and compare it against regular point-to-point and existing cooperative MIMO MAC protocols. The results show that the proposed scheme can provide considerable gains in the throughput and energy savings compared to cooperative MIMO based on fixed number of cooperating nodes.
... Now we use the data from[3]to compute the communication cost on Mica motes. (Similar results can be found for other devices considered in[9,10].) According to[3], the charge required by a ...
We present a protocol for partial (but high) coverage in sensor networks. We demonstrate that it is feasible to maintain a high coverage (>90%) while significantly increasing coverage duration when compared with protocols that provide full coverage. In particular, we show that our protocol maintains 94% coverage for a duration that is 2.3-7 times the duration for which existing protocols maintain full coverage. Through simulations, we show that our protocol provides load balancing and that the desired level of coverage is maintained (almost) until the point where all sensors deplete their batteries.
... Now we use the data from[13]to compute the communication cost on Mica motes. (Similar results can be found for other devices considered in[17,18].) According to[13], the charge required by a Mica mote to transmit a packet is 20 nAh, to receive a packet is 8 nAh, and to idly listen for 1 millisecond is 1.25 nAh. Based on this data, the total communication cost (including transmissions and receptions) in the above simulation is equivalent to the cost that a node stays in idle mode for 4.66 minutes, which is only 0.1% of the network lifetime (4541 minutes). ...
We present a simple, local protocol, pCover, which provides partial (but high) coverage in sensor networks. Through pCover, we demonstrate that it is feasible to maintain a high coverage (~90%) while significantly increasing coverage duration when compared with protocols that provide full coverage. In particular, we show that we are able to maintain 94% coverage for a duration that is 2.3-7 times the duration for which existing protocols maintain full coverage. Through simulations, we show that our protocol provides load balancing, i.e., the desired level of coverage is maintained (almost) until the point where all sensors deplete their batteries
... To the best of our knowledge this is the first academic work that provides detailed measurements and comparative analysis detailing the power consumption and tradeoffs in modern 1G and 10G network interface cards over a range of design, manufacturer and physical media types. Previous work, however, has studied the power consumption of server, desktop and portable devices in various contexts as outlined below: Stemm and Katz carried out one of the earliest studies on characterizing energy consumption in wireless NICs in hand-helds[14]. Like this work they measured the voltage and current drop across a small resistor for the purposes of determining power consumption. They show that the wireless interface accounts for a large proportion of the total power used in the hand-helds, and, similar to this work, the idle state dominates power consumption. ...
This paper quantifies the energy consumption in six 10 Gbps and four 1 Gbps interconnects at a fine-grained level, introducing two metrics for calculating the energy efficiency of a network interface from the perspective of network throughput and host CPU usage. It further compares the energy efficiency of multiport 1 Gbps to 10 Gbps interconnects.
Neighbour discovery plays a crucial role for communication in sparsely dense mobile networks, especially in delay tolerant networks, where neighbour discovery latency is generally much higher than the node contact duration. Hence, energy efficient neighbour discovery is an essential aspect of this type of network. Synchronous wake-up scheduling of the nodes can be used to decrease the neighbour discovery latency, but such scheduling cannot be applied to delay tolerant networks where the essence of the communication lies in it’s decentralization. Additionally, the synchronous process needs a global clock for node synchronization. Using a global clock is an energy hungry process. Hence, to avoid this energy hungriness, over the years, many asynchronous protocols based on wake-up scheduling have been developed in order to timely wake-up the nodes to ease the neighbour discovery process in an energy efficient manner. However, asynchronous protocols have reduced message delivery and are not fine-grained enough to support high delivery ratio. In this paper, we have used a binary Galois field based technique for designing asynchronous wake-up scheduling. A thorough analysis has been performed to demonstrate the performance of this asynchronous protocol when compared to the current state of the art in the adaptive and the non-adaptive mode. Results show that the proposed protocol in non-adaptive mode increases message delivery probability by 10% and reduces message delivery latency approximately by 7% while keeping the energy consumption constant when compared to the other existing asynchronous protocols.
Routing strategies need to strike a balance between responsiveness and energy efficiency. Achieving this balance poses new challenges that do not coalesce either with infrastructure or ad hoc wireless networks performance requirements. Multiple strategies have emerged as a workable solution to the routing problem. Either of these solutions however cater to but one of the many constraints posed by the networks. To address this issue we propose a delay sensitive energy efficient reliable routing (DSERR) algorithm which achieves application specified soft delays with energy scavenging being the foremost concern. We try to provide soft end-to-end (e2e) delay guarantee that is proportional to the distance between the source and destination. Our algorithm uses the per hop greedy selection for soft real-time guarantees as it is impossible to provide hard guarantees in a dynamic network. DSERR presents a stateless architecture providing hop by hop reliability of data delivery to support desired delivery reliability across the sensor network.
In recent years, a lot of studies have been devoted to make communications possible between the nodes in the disconnected network scenarios, such as delay-/disruption-tolerant network (DTN). However, many DTN scenarios rely on mobile devices with restricted energy capacity which would directly affect the lifetime and performance of the network composed by these devices. So we pay attention to the energy-saving mechanisms of DTN in this paper and introduce the architecture, theoretical basis, evaluation metrics, classification, and challenges of the energy-saving mechanism. Next, the main energy-saving mechanisms are compared; the research on the energy management for DTN is summarized and analyzed in this paper, and the open issues for future research are also pointed out to motivate new research and development in the energy management field of DTN.
Recent advances in wireless networking technology and the exponential development of semiconductor technology have engendered a new paradigm of computing, called personal mobile computing or ubiquitous computing. These systems have the potential to make a major impact on science education over the next decade. This paradigm offers a vision of the future with a much richer and more exciting set of architecture research challenges than extrapolations of the current desktop architectures. In particular, these devices will have limited energy resources, will handle diverse data types, and will operate in environments that are insecure, dynamic and which vary significantly in time and location. This chapter is about designing such a mobile multimedia system.
A prime goal of wireless sensor networks (WSNs) is to minimize energy consumption than high channel efficiency and low channel access delay. Existing MAC protocols for WSNs reduce energy consumptions by introducing variation in an active/sleep mechanism, but they cannot save energy during the execution of backoff algorithm. In this chapter, we study and compare the different backoff algorithms for wireless sensor networks. We also use the concept of a geometrically increasing probability distribution for contention process. This allows us to introduce improved backoff (IB) algorithm for energy efficient MAC protocol in WSNs, where binary exponential backoff (BEB) based algorithm is widely used. With the help of numerical results we show that the IB gives edge over BEB in throughput, channel access delay, and energy efficiency under varying traffic conditions.
Energy consumption is a prime concern in the design of most protocols used in wireless sensor networks(WSNs). Modelling energy consumption in the network is therefore of high importance for protocol design. Most protocols are built on the basic power consumption model of a wireless communication system. It simply uses the output power of the transmitter's amplifier, the sensitivity level of the low noise amplifier of the receiving node; without so much focus on how the randomness of the wireless channel environment affects the energy consumption of the network. This paper presents a stochastic modelling approach of the energy consumption in a WSN. The model is stochastic because it considers the effects of the randomness of the wireless environment, the random change of modes of operation and the randomness of the time duration in each mode of operation (Active, Idle or sleep). The model uses a multi-hop Energy-Aware Gradient Based Routing(GBR) protocol.The prime focus lies on modelling in details the energy consumption of the WSN for a single hop transmission level as well as providing a theoretical total energy consumption model taking into account not only the data message but also the different overhead control messages. This energy consumption model can be used to guide design choices at the different layers including the network topology designs, node placement, energy efficient routing and power management schemes. The developed energy consumption model of the EA-GBR is then compared to the one of the generic GBR as well as the Competing GBR in [1].
We explore the use of cooperative multi-input multi-output (MIMO) communications to prolong the lifetime of a wireless sensor network (WSN). Single-antenna sensor nodes are clustered into virtual antenna arrays that can act as virtualMIMO (VMIMO) nodes.We design a distributed cooperative clustering protocol (CCP), which exploits VMIMO's diversity gain by optimally selecting the cooperating nodes (CNs) within each cluster and balancing their energy consumption. The problem of optimal CN selection at the transmit and receive clusters is formulated as a nonlinear binary program. Aiming at minimizing the imbalance in the residual energy at various nodes, we decompose this problem into two subproblems: finding the optimal number of CNs (ONC) in a cluster and the CN assignment problem. For the ONC problem, we first analyze the energy efficiency of two widely used VMIMO methods: distributed Space Time Block Code (DSTBC) and distributed Vertical-Bell Laboratories-Layered-Space-Time (DVBLAST). Our analysis provides an upper bound on the optimal number of CN nodes, which greatly reduces the computational complexity of the ONC problem. The second subproblem is addressed by assigning CNs based on the residual battery energy. To make CCP scalable to large WSNs, we propose a multihop energy-balanced routing mechanism for clustered WSNs (C-EBR) with a novel cost metric. Finally, we derive sufficient conditions on the intra- and intercluster ranges, under which CCP guarantees connectivity of the intercluster topology. Extensive simulations show that the proposed approach dramatically improves the network lifetime.
Available energy becomes a critical design issue for the increasingly complex real-time embedded systems. Phase Change Memory (PCM), with high density and low idle power, has recently been extensively studied as a promising alternative of DRAM. Hybrid PCM-DRAM main memory architecture has been proposed to leverage the low power of PCM and high speed of DRAM. In this paper, we propose energy-aware real-time task scheduling strategies for hybrid PCM-DRAM based embedded systems. Given the execution time variation when a task is loaded into PCM or DRAM, we re-design the static table-driven scheduling for a set of fixed tasks, as well as the Rate-Monotonic (RM) and Earliest Deadline First (EDF) scheduling policies for periodic task sets. Furthermore, since the actual execution time can be much shorter than the worst-case execution time in the actual execution, we propose online schedulers which migrates the tasks between PCM and DRAM to optimize the energy consumption by utilizing the slack time resulted from the completed tasks. All the proposed algorithms minimize the number of task migrations from PCM to DRAM by ensuring that aperiodic tasks are not migrated while each periodic task instance can be migrated at most once. Experimental results show our proposed scheduling algorithms satisfy the real-time constraints and significantly reduce the energy consumption.
Wireless Sensor network consists of large number of sensor nodes, which are deployed densely. A key challenge of wireless sensor network is that their sensor nodes contain less amount of battery power. Consequently, efficient utilization of battery power inside the network is a main design consideration. In the querying or monitoring application like critical condition in a particular region, we need the network that respond in few seconds. For the purpose of response in less time, we require energy efficient routing of information inside the network. In this paper, we are proposing an energy efficient clearance routing method to collect/route the query towards a particular region inside the network.
In this paper, we propose and analyze the optimized sleep mode for a mobile node (MN) in IEEE 802.16e wireless metropolitan area networks. Because a MN in a sleep mode specified in 802.16e specification should maintain state information with the base station currently attached, it must renew sleep state with a new base station after handover which leads to unnecessary waste of battery power. Noting that the mobility pattern of a MN is independent of call arrival patterns, we propose an optimized sleep mode to eliminate unnecessary standby period of a MN in sleep state after handover. We also propose an analytical model for the proposed scheme in terms of power consumption and the initial call response time. Simulation studies that compare the performance between the sleep mode and the optimized sleep mode show that our scheme marginally increases initial call response delay with the huge reduction in power consumption.
As the growth of multimedia communication in mobile ad hoc networks MANETs, every node needs to conserve its power since most nodes are powered by a battery source. Mobile ad hoc networking is a challenging task due to the lack of resources in the network as well as the frequent changes in network topology. Although lots of research has been done on supporting QoS in the internet and other networks, but they are not suitable for mobile ad hoc networks and still QoS support for such networks remains an open problem. In this paper, we propose that the enhanced ad hoc on-demand distance vector AODV routing protocol which is modified to improve the networks lifetime in mobile ad hoc network MANET. The new scheme has been proposed for achieving QoS in terms of packet delivery, better power management and stable routes. The proposed scheme has been incorporated using AODV protocol.
Energy efficiency is a major issue of concern in wireless ad hoc networks as mobile nodes rely on batteries, which are limited sources of energy, and, in many environments, it is quite a cumbersome task to replace or recharge them. Despite the progress made in battery technology, the lifetime of battery powered devices continues to be a key challenge, requiring additional research on efficient design of platforms, protocols, and systems. Many tangible efforts are made by many researchers to reduce the power consumption at protocol level by designing an energy efficient protocol to prolong the lifetime of the networks. The main focus of this chapter is to present a comprehensive analysis of energy efficient techniques in wireless ad hoc networks, integrating various issues and challenges to provide a big picture in this area. This chapter addresses energy management techniques in wireless ad hoc networks, especially in decentralized ad hoc environments.
Minimization of power consumption is a critical design goal for wireless-relay networks comprised of battery-powered sensor devices. Traditionally, wireless communication is optimized to minimize the total transmission power. In the paper, we further include the detection power and the reception power in order to minimize the overall network power consumption for information exchange in wireless-relay sensor networks (WSNs). Specifically, after the physical attributes of relay nodes are given, we wish to maximize the network lifetime by a proper selection of the transmission range, the sleep period, and the participation density. We propose a random gossip network (RGN) as a framework for our analysis. We find simple rules govern the optimal settings of these three parameters for all-to-all broadcast in the RGN. One key relationship is that the optimal number of nodes broadcasting messages in a time epoch within the transmission range depends only on the path loss exponent and the network dimensionality. This optimal value does not depend on factors such as the physical network size, the reception cost, and the message origination rate. Moreover, it is shown that neither increasing nor decreasing the physical network size will affect the optimal value of these design parameters. The optimal setting for power consumption minimization is a scalable solution. Finally, we demonstrate that our results can be well applied to predict the optimal value of operational parameters for information exchange as well as information dissemination in actual WSNs.
Based on LEACH algorithm, we propose an improved HMR-LEACH algorithm (Hierarchical Multi-path Routing-LEACH), which improves election of cluster head and adopts multi-hop algorithm instead of one hop to transmission data. When chooses transmission path, HMR-LEACH algorithm takes energy and distance into account and assigns a probability to each transmitting path by weight. Simulation result indicates that HMR-LEACH outperforms the LEACH algorithm and prolongs the life of the network dramatically.
A schedule-based approach, such as time division multiple access, is more efficient than a contention-based approach in terms of energy saving by switching sensors into sleeping mode. However, it does not use the transmission media effectively as each time slot is dedicated to a sensor and therefore cannot be used by others should it be idle. Moreover, a schedule-based approach requires a central node to manage and broadcast the schedule to other members, causing high delay and unscalability. On the other hand, contention-based protocols can be used in a distributed fashion. However, contention-based protocols such as IEEE 802.11 waste a lot of energy in idle listening. In this paper, we propose a hybrid approach between contention- and schedule-based protocols. The preliminary results using simulation and a test bed show that our proposed approach uses transmission media more efficiently, leading to lower delay while preserving energy for wireless sensor networks.
With the proliferation of mobile streaming multimedia, available battery
capacity constrains the end-user experience. Since streaming
applications tend to be long running, wireless network interface card's
(WNIC) energy consumption is particularly an acute problem. In this
work, we explore the WNIC energy consumption implications of popular
multimedia streaming formats from Microsoft (Windows media), Real (Real
media) and Apple (Quick Time). We investigate the energy consumption
under varying stream bandwidth and network loss rates. We also explore
history-based client-side strategies to reduce the energy consumed by
transitioning the WNICs to a lower power consuming sleep state. We show
that Microsoft media tends to transmit packets at regular intervals;
streams optimized for 28.8 Kbps can save over 80% in energy consumption
with 2% data loss. A high bandwidth stream (768 Kbps) can still save 57%
in energy consumption with less than 0.3% data loss. For high bandwidth
streams, Microsoft media exploits network-level packet fragmentation,
which can lead to excessive packet loss (and wasted energy) in a lossy
network. Real stream packets tend to be sent closer to each other,
especially at higher bandwidths. Quicktime packets sometimes arrive in
quick succession; most likely an application level fragmentation
mechanism. Such packets are harder to predict at the network level
without understanding the packet semantics.
Sensor networks are deployed in numerous military and civil applications, such as remote target detection, weather monitoring, weather forecast, natural resource exploration and disaster management. Despite having many potential applications, wireless sensor networks still face a number of challenges due to their particular characteristics that other wireless networks, like cellular networks or mobile ad hoc networks do not have. The most difficult challenge of the design of wireless sensor networks is the limited energy resource of the battery of the sensors. This limited resource restricts the operational time that wireless sensor networks can function in their applications. Routing protocols play a major part in the energy efficiency of wireless sensor networks because data communication dissipates most of the energy resource of the networks. This paper studies the importance of considering neighboring nodes in the energy efficiency routing problem. After showing that the routing problem that considers the remaining energy of all sensor nodes is NP-complete, heuristics are proposed for the problem. Simulation results show that the routing algorithm that considers the remaining energy of all sensor nodes improves the system lifetime significantly compared to that of minimum transmission energy algorithms. Also, the energy dissipation of neighboring nodes accounts for a considerable amount of the total energy dissipation. Therefore, a method that reduces the energy dissipation by notifying the neighboring nodes to turn off their radio when not necessary is proposed. By reducing the unnecessary energy dissipation of the neighbors, the lifetime is increased significantly.
This chapter reviews medium access control (MAC), an enabling technology in wireless sensor networks. MAC protocols control how sensors access a shared radio channel to communicate with neighbors. Battery-powered wireless sensor networks with many nearby nodes challenge traditional MAC design. This chapter discusses design trade-offs with an emphasis on energy efficiency. It classifies existing MAC protocols and compares their advantages and disadvantages in the context of sensor networks. Finally, it presents S-MAC as an example of a MAC protocol designed specifically for a sensor network, illustrating one combination of design trade-offs.
In a wireless sensor network (WSN), the sensors closest to the sink tend to deplete their energies faster than the other sensors, which is known as an energy hole around the sink. To avoid this, a new scheme for placing nodes, via adjusting surface densities and initial energies in each ring in a ring model, is proposed in this paper. A new definition of network efficiency, including the consideration of energy cost, is also introduced and applied. The simulation results demonstrate that this scheme can significantly increase the network efficiency compared with the uniform placement algorithm, especially when the size of the network is relatively large
Motivated by the recent and rapidly increasing interest in energy-saving schemes, this paper presents a novel PHY/MAC layer design for wireless sensor networks (WSNs). Capitalizing on the observed rare-event feature of most WSNs, we first design an energy-efficient ternary modulation scheme wherein the modulated symbols can classify (or color) the state of the underlying phenomenon as green, yellow or red. Introducing this new notion of a yellow message (that lies between the binary values represented by green and red) results in great flexibility and energy savings when designing a MAC sleeping scheduler (turning nodes on-and-off). The proposed sleeping protocol enjoys low energy consumption and respects a latency constraint by efficiently using the time-division-multiple-access technique along with the ternary modulation scheme. Numerical results illuminate the energy savings provided by the proposed schemes and quantify the energy-latency tradeoffs
We consider a distributed detection problem where nodes in a wireless sensor network (WSN) report their local decisions to a fusion center that can in turn describe the phenomenon under observation. For such networks, energy- efficient and minimum delay designs are well motivated for a number of applications including surveillance and monitoring in tactical and environmental scenarios. We aim at designing a distributed detection scheme that achieves minimum reporting delay of events and respects constraints on battery life time (or power consumption) and probability of erroneous detection. Our design exploits the interaction between both physical and medium access control (MAC) layers. It attains energy efficiency by using a sleeping protocol whereby monitoring nodes can deterministically switch between awake and sleeping modes to utilize efficiently their power resources. This novel protocol capitalizes on an energy-efficient ternary modulation scheme we devised recently and exploits characteristics of the phenomenon under observation. The resultant cross-layer design is flexible to trade-off latency for energy consumption (and thus life time). Furthermore, it provides the designer with a suite of tuning parameters that can be adjusted to best fit the underlying application. Simulated experiments corroborate our analytical results.
A promising application for RFID tags is to trace valuable assets in an inventory. In such systems, the key challenge is to achieve reliable and energy-efficient tag reads. This paper proposes a novel tag reading protocol, Relay-MAC, which aims at reducing the information sent over the network and the energy spent in collision detection and handling by introducing deliberate sequencing at runtime. This paper provides an in-depth study of the design issues one may face in implementing such a protocol on RFID tags, and validates its feasibility using simulation studies. These studies clearly demonstrate that Relay- MAC can yield much better throughput and energy conservation when compared to a conventional select-and-read protocol.
Sensor networks are being increasingly deployed for diverse monitoring applications. Event data are collected at various sensors and sent to selected storage nodes for further in-network processing. Since sensor nodes have strong constraints on their energy usage, this data transfer needs to be energy-efficient to maximize network lifetime. In this article, we propose a novel methodology for trading energy versus latency in sensor database systems. We propose a new protocol that carefully schedules message transmissions so as to avoid collisions at the MAC layer. Since all nodes adhere to the schedule, their radios can be off most of the time and only wake up during well-defined time intervals. We show how routing protocols can be optimized to interact symbiotically with scheduling decisions, resulting in significant energy savings at the cost of higher latency. We demonstrate the effectiveness of our approach by means of a thorough simulation study, using synthetic data as well as real-world traffic workloads.
As power efficiency is one of the most severe constraints in wireless sensor networks, we propose a scheduling protocol for reducing power dissipation. The protocol (DB-TDMA) is a hybrid of depth based scheduling and TDMA, which is applicable to clustering topology. Depth based scheduling is adopted for cluster heads scheduling, and TDMA is for member nodes scheduling in a cluster. DB-TDMA supports fluctuated demand in the network. It reduces the energy required for listening and receiving. Simulation results show that DB-TDMA outperforms two existing scheduling protocols both in schedule construction efficiency and schedule quality.
Sensors are deployed in a sensor network for the purpose of providing data about environmental phenomena to the sink node(s).
As not all sensors may be able to transmit their data directly to the sink(s), sensors must also route other sensors’ data.
Therefore, sensors must assume roles of both data provider and router. However, there are often many more sensors in the network
than are needed at a given time to accomplish these tasks. Sensor management is needed to assign roles to each sensor, so
that nodes that are not needed at a given time can enter a sleep state to save energy until they are needed, thereby extending
network lifetime. The area of sensor management, as defined here, includes topology control--choosing which nodes should be
routers to ensure a connected network—and sensing mode selection—choosing which nodes should sense data to meet application
requirements (application QoS). It is possible to maximize network lifetime by finding optimal schedules of when each node
should perform each function. However, these optimizations are computationally intensive, require global knowledge, and are
not robust to changes in network topology. Therefore, there is a need for distributed, robust, and computationally efficient
sensor management protocols that extend network lifetime while ensuring that application goals are met. In this chapter, protocols
for both topology control and sensing mode selection are described and a qualitative comparison of these protocols is given.
Wireless sensor networks (WSN) are designed for data gathering and processing, with particular requirements: low hardware
complexity, low energy consumption, special traffic pattern support, scalability, and in some cases, real-time operation.
In this paper we present the virtual TDMA for sensors (VTS) MAC protocol, which intends to support the previous features,
focusing particularly on real-time operation. VTS adaptively creates a TDMA arrangement with a number of timeslots equal to
the actual number of nodes in range. Thus, VTS achieves an optimal throughput performance compared to TDMA protocols with
fixed size of frame. The frame is set up and maintained by a distributed procedure, which allows sensors to asynchronously
join and leave the frame. In addition, duty cycle is increased or decreased in order to keep latency constant below a given
deadline. Therefore, a major advantage of VTS is that it guarantees a bounded latency, which allows soft real-time applications.
The aim of this paper is to evaluate the performance of an energy aware routing protocol, called ECB-AODV (Energy Constraint protocol Based on AODV) which derives from the AODV protocol and which is based on the local decisions of intermediate stations to maintain the connectivity of the network as long as possible. The results obtained using the network Simulator NS-2 demonstrate how small changes in the principle of the AODV protocol can efficiently balance the energy consumption between nodes, which increases the network lifetime.
While the computing requirements of mobile battery-powered systems in general are increasing, it is clear that advances in battery technology have not kept pace with the ever increasing energy demands of these devices. Researchers are exploring architectural, hardware, software and system level optimization techniques to minimize the overall energy consumption of these computers. An analysis of the power consumption behavior of these devices when running representative workloads will provide a critical and a needed insight that will assist designers in developing low power future generations devices. In this work, and in order to get a better understanding of the factors that affect power consumption in pocket PCs, a series of experiments were performed on pocket computers while being subjected to a variety of operational scenarios. Based on the analysis and observations made from these measurements we were able to relate the consumption behavior of the computer to some of its operational parameters
Low power consumption is important for static sensor nodes and handheld nodes where no power source other than a battery is available. This paper presents the results of an investigation into the power consumption performance of two contrasting ad hoc routing protocols from the IETF MANET working group, namely the proactive protocol OLSR and the reactive protocol DSR. A model of the communications stack, including the routing protocols and air interface is described. The power consumption performance of the routing protocols is compared across a range of simulated network scenarios. Power consumption scaling trends with increasing network size, density and user traffic are reported and hotspots arising from topological causes and/or characteristics of the routing protocols are identified
In the traditional medium access control (MAC) protocols for wireless sensor networks (WSNs), energy consumption is traded for throughput and delay. However, in future WSNs, throughput and delay performance had better not be sacrificed for energy conservation. Here first, an incompletely cooperative game-theoretic heuristic-based constraint optimisation framework is introduced to achieve the goals of throughput, delay and energy conservation simultaneously. Then a simplified game-theoretic MAC (G-MAC) protocol is presented, which can be easily implemented in WSNs. Simulation results show that compared with two typical MAC protocols for WSNs, sensor MAC and timeout MAC, G-MAC can increase system throughput, and decrease delay and packet-loss-rate, while maintaining relatively low energy consumption.
In this paper we present results of experiments with RFID system using active tags and DS-CDMA transmission. The performance of the system has been compared with the standard RFID system defined in ISO 18000-7 that occupy the same transmission bandwidth. The obtained results show that the system with DS-CDMA transmission is about 15 dB more tolerant to narrowband interferences, which can be essential in many practical scenarios.
In this paper, we present two practical algorithms for selecting a subset of channels in virtual multiple-input-multiple-output (MIMO) wireless sensor networks (WSNs) to balance the MIMO advantage consumption of sensor cooperation. If intracluster node-to-node multihop needs be taken into account, the maximum spanning tree searching (MASTS) algorithm, with respect to the cross-layer design, always provides a path connecting all sensors. When the WSN is organized in a manner of cluster-to-cluster multihop, the singular-value decomposition-QR with threshold (SVD-QR-T) approach selects the best subset of transmitters while keeping all receivers active. The threshold is adaptive by means of fuzzy c-means (FCM). These two approaches are compared by simulation against the case without channel selection in terms of capacity, bit error rate (BER), and multiplexing gain with water filling or equal transmission power allocation. Despite less multiplexing gain, when water filling is applied, MASTS achieves higher capacity and lower BER than virtual MIMO without channel selection at moderate-to-high signal-to-noise ratio (SNR), whereas SVD-QR-T by FCM provides the lowest BER at high SNR; in the case of no water filling and equal transmission power allocation, MASTS still offers the highest capacity at moderate-to-high SNR, but SVD-QR-T by FCM achieves the lowest BER. Both algorithms provide satisfying performances with reduced resource consumption.
One of the most compelling and immediate applications of pervasive computing would be to use RF technology to support low-cost, long-lived and continual tracking of assets. Unfortunately, initial solutions have not yet led to widespread deployment. We believe that meeting the economic and system requirements of this application requires a redesign of the tag, the transmission protocol, and the algorithms used by basestations to identify tags, all with the underlying goal of reducing cost and power consumption through simplification. In this paper, we propose a new inventory tracking system, called RollCall, in which a transmit-only RFID tag will be attached to every item, and these tags will report their presence to the readers periodically by broadcasting the tag IDs so that a missing tag/item can be quickly identified. The power conservation obtained from short transmissions on a very simple MAC layer combined with the hardware cost and size reduction from having a simple radio stack on the tag provides considerable economic, dimensional and tag lifetime benefits. In this paper, we present the design and architecture of the RollCall system, and conduct preliminary studies to examine the feasibility of building such a system by tweaking off-the-shelf signal processing algorithms. Initial studies and simulation results suggest that it is possible to monitor about 5000 tags in a store with networked basestations at a low error rate with an extended tag life time of at least a year based on conservative estimates with non-custom tag radio and micro-controllers.
The residual power levels of the nodes in a wireless sensor network determine its important performance metrics like the network lifetime, coverage, and connectivity. In this paper, we present a general framework to model the availability of power at sensor nodes as a function of time, based on models for population dynamics in biological studies. Models are developed for sensors with and without battery recharging and expressions are derived for the network lifetime as well as the distribution and moments of random variables describing the number of sensors with different levels of residual energy as a function of time. The model is also extended to the case where new sensors are periodically added to the network to substitute older sensors that have expended their energy. Finally, the effect of the packet arrival rates and a sensor's geographical location are modeled. Simulation results to verify the accuracy of the proposed models are presented.
A non-uniform grid-based coordinated routing design in wireless sensor networks is presented. The conditions leading to network partition and analysis of energy consumption that prolongs the network lifetime are studied. We implement routing in heavily populated sensor networks. By maintaining constant values for parameters such as path loss exponent, receiver sensitivity and transmit power, and varying between uniform and non-uniform grids, we observe energy consumption patterns for each of the grid structures, and infer from the network lifetime the better suited grids for uniformly and randomly deployed sensor nodes.
We present a simple, local protocol, pCover, which provides partial (but high) coverage in sensor networks. Through pCover, we demonstrate that it is feasible to maintain a high coverage (∼90%) while significantly increasing coverage duration when compared with protocols that provide full coverage. In particular, we show that we are able to maintain 94% coverage for a duration that is 2.3–7 times the duration for which existing protocols maintain full coverage. Through simulations, we show that our protocol provides load balancing, i.e., the desired level of coverage is maintained (almost) until the point where all sensors deplete their batteries. We also show that pCover handles failure of sensors, different coverage areas, different node densities, and different topologies, and can be used for dynamically changing the level of coverage.
Low-power integration of sensing, communication, and computation requires a new approach to wireless design. Flexible interfaces and primitive accelerators enable aggressive system-level optimizations. Mica's flexible design serves as a building block for creating efficient application-specific protocols. Instead of defining narrow, standardized application interfaces, Mica provides a set of richly interconnected primitives (such as data serializers and timing extractors) to facilitate cross-layer optimizations. To explore novel systems approaches, researchers can develop customized protocols tailored to their application; Mica does not require use of predefined protocols.
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