Seminar OnLow Energy Efficient Wireless Sensor Network PRESENTED BY-DEEPAK KUMAR DHAL REGD. NO-0901304038 ELECTRONICS AND COMMUNICATION ENGINEERING GANDHI INSTITUTE OF TECHNOLOGY AND MANAGEMENT NOVEMBER 2012 1
CONTENT 2 What is WSN? Power consumption in WSN Sources of energy waste General approaches to energy saving MAC protocol for WSN Conclusion Reference
What is WSN? 3A wireless sensor network is a collection of nodes“sensors” organized into a cooperative network.Wireless sensor network consists of sensor nodesdeployed over a geographical area for monitoringphysical phenomena like temperature, humidity,vibrations, seismic events, and so on. SENSOR NODES COMPONENTS •Sensing Subsystem •Processing Subsystem •Wireless communication subsystem •Power source
Power consumption in WSNs 4 The power issue in the wireless sensor network is one of the biggest challenges, because the sensor has a limited source of power which is also hard to replace or recharge “e.g. sensors in the battle field, sensors in a large forest … etc”. Why limited source of power? Inexpensive nature. Limited size and weight. Redundant nature.
Major Sources of Energy Waste in WSNs 51. Useful power consumption: Transmitting or receiving data. Processing query requests. Forwarding queries and data to the neighbors.2. Wasteful power consumption: Idle listening to the channel “waiting for possible traffic”. Retransmitting because of collisions “e.g. two packets arrived at the same time at the same sensor”. Overhearing “when a sensor received a packet doesn’t belong to it”. Generating and handling control packets. Over-emitting “when a sensor received a packet while it is not rea
GENERAL APPROACHES TO ENERGY SAVING 6 Duty Cycling Data DrivenDuty cycle Duty cycle is defined as the fraction of time nodes which are active during their lifetime.Data Driven Data driven approaches can be used to improve the energy efficiency even more.
DUTY CYCLING 7It can be achieved through two different approaches: it is possible to exploit node redundancy which is typical in sensor networks and adaptively select only a minimum subset of nodes to remain active for maintaining connectivity. Nodes that are not currently needed for ensuring connectivity can go to sleep and save energy. SENSOR MODES TRANSMISSION RECEPTION IDLE SLEEP WAKE SLEEP UP Goal: reduce the time where the sensor is being idle. Drawback: Additional delay because of waiting for the next-hop node to wake up
8ON-DEMAND PROTOCOL The basic idea is that a node should wake up only when another node wants to communicate with it. The main problem associated with on-demand schemes is how to inform the sleeping node that some other nodes are willing to communicate with it.SCHEDULED RENDEZVOUS APPROACH The basic idea behind scheduled rendezvous schemes is that each node should wake up at the same time as its neighbours. Typically, nodes wake up according to a wakeup schedule and remain active for a short time interval to communicate with their neighbours. Then, they go to sleep until the next rendezvous time.
MAC PROTOCOL FOR WSN 9 MAC ( medium access control) Contension Hybrid TDMA based based S(sensor)- MAC T(time out)- MAC μ (energy- DEE(dynami c)-MAC Z(zebra)- MAC A(advertisem ent)-MAC efficient)-MACU(utilization SPARE-MAC )-MAC
S-MAC 10Stand for:Sensors Medium Access Control.Strategy:All node follow a periodic sleep/wake cycle, When a node is idle, it is more likely tobe asleep instead of continuously listening to the channel. S-MAC reduces the listentime by letting the node go into periodic sleep mode.Advantages: Periodic Listen. Collision Avoidance. Overhearing Avoidance. Message passing.Disadvantages:S-MAC fixed duty cycle i.e. active time is fixed• if message rate is less energy is still wasted in idle-listening.
T-MAC 11Stand for:Timeout Medium Access Control.Strategy:It adaptively adjusts the sleep and wake periods based on the estimatedtraffic flow.AdvantageTimes out on hearing nothing.DisadvantageEarly sleeping problemi.e. node goes to sleep when aneighbor still has messagefor it.
U-MAC 12Stand forUtilization Medium Access ControlStrategy U-MAC is based on the S-MAC protocol and provides three main improvements on SMAC: various duty cycles, utilization based tuning of duty-cycle, and selective sleeping after transmission.
μ- MAC 13Stand forEnergy-Efficient Medium Access ControlStrategy μ-MAC assumes a single time slotted channel as shown in Figure. Protocol operation alternates between a contention and a contention- free period. The contention period is used to build a network topology and to initialize transmission sub channels.
DEE-MAC 14Stand forDynamic Energy Efficient Medium Access ControlStrategy DEE-MAC is an approach to reduce energy consumption, which lets the idle listening nodes go into sleep using synchronization performed at the cluster head DEE-MAC operation comprise of two phase:1) Cluster formation phase2) Transmission phase
SPARE-MAC 15Stand forSlot Periodic Assignment for Reception Medium Access ControlStrategy save energy through limiting the impact of idle listening and traffic overhearing. It utilizes a distributed scheduling solution, which assigns specific time slots to each sensor node for reception.
Z-MAC 16Stand forZebra Medium Access ControlStrategy guaranteed access to its owner slot (TDMA style) a contention-based access to other slots (CSMA style)Advantage• collisions and energy consumptions are reduced.
A-MAC 17Stands forAdvertisement-based Medium Access ControlStrategynode is active only when it is the sender or the receiver, during other time itjust goes to sleep.Advantageenergy waste is avoided on overhearing and idle listening.
Data Driven Approach 18 Data-driven approaches can be used to improve the energy efficiency even more. Data-driven approaches can be divided to data reduction schemes address the case of unneeded samples, while energy-efficient data acquisition schemes are mainly aimed at reducing the energy spent by the sensing subsystem. Data reduction can be divided two parts1) in-network processing2) Dataprediction In-network processing consists in performing data aggregation (e.g., computing average of some values) at intermediate nodes between the sources and the sink. In this way, the amount of data is reduced while traversing the network towards the sink. Data prediction consists in building an abstraction of a sensed phenomenon
CONCLUSION 19 Energy is one of the most critical resources for WSNs. Extensive research has been conducted to address these limitations by developing schemes that can improve resource efficiency. In this paper, we have summarized some research results which have been presented in the literature on energy saving methods in sensor networks. Although many of these energy saving techniques look promising, there are still many challenges that need to be solved in the sensor networks.
REFERENCE 20 Energy Saving in Wireless Sensor Networks, Zahra Rezaei, Shima Mobininejad, Department of Computer Engineering Islamic Azad University, Arak Branch , Arak , Iran. I.Demirkol,C.Ersoy,F.Alagöz, "MAC Protocols for Wireless Sensor Networks: A Survey", IEEE Communications Magazine. A.Bachir, Mischa Dohler,T.Watteyne,K.Leung, "MAC Essentials for Wireless Sensor Networks", IEEE COMMUNICATIONS SURVEYS & TUTORIALS.