Mohamed Hauter CMPE 259 – Sensor Networks UCSC 1

* Introduction * Objectives * Proposals and approaches * Related Work * Simulations and Results * Strengths and weaknesses 2

* An energy-efficient sensor network * Minimal number of sensor nodes in active mode * Increase the lifetime of the sensor network * Prevent connection degradation 3

* Terminology: * DPM: Dynamic Power Management * OGDC: Optimal Geographical Density Control * ACPI: Advanced Configuration and Power Interface 4

* Approach: * Tackle energy efficiency on all levels of the entire network * Dynamic power management = shutting down nodes when not needed and wake them up when necessary * Consideration of the state of components ( microprocessor, A/D converter, memory, transceiver, etc.) when making a decision to turn off a node 5

* Approach (continue): * Density control while maintaining: a. Coverage b. Connectivity * Localized density control algorithm 6

* Approach (continue): * Consideration of battery status and energy wasted in the process of node-awakening * Incorporate OGDC in the control logic 7

* Verity of DPM techniques * Dynamic Voltage Scaling * Dynamic Voltage and Frequency Scaling * Sentry based power management (application driven) * Software and operating system power management 8

* Weaknesses of traditional predictive techniques: * Cannot provide an accurate tradeoff between energy saving and performance degradation * Does not deal with systems in which requests can be queued 9

* Power aware sensor node model: * Node components: processor, memory, AD converter, and transceiver (radio) * Components of each node can be in different states: active, idle, or sleep * Different combinations of component power modes 10

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* Sleep-state transition policy: * P = Power Consumption * t = Time of event * s = sleep state * Tau = transition mode 12

* System Parameters: 13

* 50x50 meters area of coverage * 100 nodes * Uniformly and randomly distributed * Nodes are capable of directly communicating with the host * Each nodes initial energy is 100 joules 14

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Strengths: * An energy-efficient sensor network * Minimal number of sensor nodes in active mode * Increase the lifetime of the sensor network * Prevent connection degradation Weaknesses: *Analysis did not take latency into account * Events missed during deepest-sleep state * OGDC requires knowledge of nodes location (extra processing and memory overhead) 16

* Utilize natural sources of energy (solar, motion, vibration, etc.) to recharge nodes batteries * Employ energy-saving mechanisms * Determine the sleep and wake up probabilities of nodes using a bargaining game 17

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1.Solar 2. Thermoelectric 3. Vibration Based 19

Two types of buffers: 1.Local buffer: gathers data collected locally (through sensors). 2. External buffer: gathers data from other nodes to be relayed. 20

To find the optimal path to deliver data packets while considering: 1. Energy level 2. Path length 3. Path reliability Avoid: 1. Idle listening 2. Overhearing 3. Packet collisions 21

Using Explicit Signaling: A node notifying the access point that it is going into power-saving (PS) mode Dual Channel MAC Protocols (Avoid Collisions): Signaling channel Data transmission channel 22

Lazy packet-scheduling scheme Determine beginning and duration of transmission Transmit at a low data rate Save energy Packet delay and reduced throughput Tradeoffs! 23

QoS vs. Energy Constrains Energy harvesting limitations Integration of energy harvesting techniques across layers 24

Radio modes: Active – 25mW Listen – 14mW Sleep – 0.01mW Channel and queue-aware strategy Radio - Listen when queue is empty Sensor – sleep when channel quality is bad 25

Players: Player 1: node Player 2: data receiving entity Strategy: Player 1: select wakeup probability when in sleep mode Player 2: select wakeup probability when in listen mode Payoff: Player 1: packet blocking probability Player 2: packet dropping probability 26

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Strengths: 1. Energy efficient 2. Incorporates the states of different components of the network Weaknesses: 1. battery energy level is not taken into consideration when making a sleep/wakeup decisions 2. Data transmission delay – low data transmission rates 3. The assumption of one-hop routing model in which all nodes can reach the sink is not practical 30

* Prolong the lifetime of the network * Minimizing the data processing and communication costs * Employ multi-hop communications effectively 31

* LEACH: dividing the sensor network into cluster heads (CH) which can communicate with sinks and amongst themselves. Cluster Heads are constantly changing (random selection) to prevent draining its energy. * SOP: a tree of cluster heads is built using fixed nodes. * EDETA: builds a hierarchal tree among cluster heads to avoid direct communication with sink. 32

* HARP can save more energy by forming intra- cluster hierarchal architectures in conjunction with inter-cluster trees. * Leverage node mobility to enhance network performance in terms of coverage, lifetime, energy efficiency, and latency. 33

* Two hierarchal tree structure: 1. Between CHs and the sinks 2. Within the cluster * HARP has a local reconfiguration scheme in case of a failure * Supports more than one sink - scalability 34

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* Causes of failure: * Battery depletion, node malfunction, multipath fading, low link quality, or node mobility. * Mechanisms; 1. The recovery slot 2. The substitute node 39

* Unlike the LEACH approach, HARP ensures that nodes all die at the same time * Solves the problem of the extra energy waste of CHs * CHs are randomly selected, unless new node has less energy than existing CH. 40

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* Strengths: * Very high level of energy efficiency * Scalable design * Efficient Local recovery capability * Optimizes routing of both upstream and downstream traffic flows * Weakness: * Increased complexity in terms of resource scheduling and network topology management * Increased memory overhead 44

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