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TinyOS. Component Model Component has: –Frame (storage) –Tasks (computation) –Command and Event Interface Messaging Component Internal State Internal.

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Presentation on theme: "TinyOS. Component Model Component has: –Frame (storage) –Tasks (computation) –Command and Event Interface Messaging Component Internal State Internal."— Presentation transcript:

1 TinyOS

2 Component Model Component has: –Frame (storage) –Tasks (computation) –Command and Event Interface Messaging Component Internal State Internal Tasks CommandsEvents

3 TinyOS Application Component Graph RFM Radio byte Radio Packet i2c Temp photo Messaging Layer clocks bit byte packet Routing Layer sensing application application HW SW ADC messaging routing Thru-Route Message Application Originates Message

4 Related MAC mechanisms

5 CSMA Listening to the channel before transmission Pozitive or negative acknowledgments to signal collusion Lean toward a fundamental assumption that packet transmissions occur with a stochastic distribution, that is very different the correlated trafic found in sensor networks Aim to support many point-to-point flows

6 IEEE Aims to provide a wireless Ethernet illusion Design based on assumption of a single cell scenario, with mobile stations always in range of at least one base station –Hand off when migrating from one cell to another –No multihop scenario Assumes peer-to-peer communications rather than many-to-one data propogation

7 Bluetooth Model of creation a “wireless cable” illusion Primary MAC protocal is a centrialized TDMA protocal within piconet –Relatively static ad-hoc network supporting a small number of nodes within single cell No multihop scenario Inappropriate for sensor networks

8 Applicable Mechanisms Listening Mechanism Back off Mechanism Contention Based Mechanism Rate Control Mechanism

9 Self-Organization of a Wireless Sensor Network

10 Self-Organization A self-organized network is an independent collection of nodes in which enough information—or the ability to retrieve such information--is present in order to allow transfer of information between any two nodes in the network. Either at initialization or after a topology- modifying event Level can vary depending on the network considered.

11 Spectrum of Self-Organization

12 Protocols for Self-Organization of a Wireless Network Protocols must be able to enable network operation during: 1. start up : nodes are booted up, and network is formed. 2. steady state : energy reservoirs are full, can support all the sensing, signal processing and communication. Multihop network is formed in this mode. 3. failure : re-organization, MAC and routing algorithms for the formation of new links and routes to the sink nodes.

13 Multihop Network Can operate in both sensor-to-sink and sink- to-sensor. Bulk of the traffic will belong to the former. Significant strain on the energy resources of the nodes near the sink, that neighborhood will be more susceptible to energy depletion and failure.

14 Energy Conserving Techniques Sensor nodes will do local processing, as opposed to exchanging raw data over air Protocols must reduce messaging overhead. These two will lead to the requirement of highly localized and distributed algorithms for data processing and networking.

15 Protocols for Self-Organization of a Wireless Network(cont.) SMACS(Self-organizing Medium Access Control for Sensor Networks): for network start up and link layer organization EAR(Eavesdrop-And-Register)Algorithm: enables seamless interconnection of mobile nodes in the field of stationary nodes SAR(Sequential Assignment Routing): facilitates multihop routing SWE(Single Winner Election)- MWE(Multi-Winner Election): handle the necessary signalling and data transfer tasks in local cooperative information proccessing.

16 Link Layer Issues Channel Access Classes: Contention or explicit organization in time/freq. : not suitable for sensor networks since it requires monitoring channel at all times Organized channel access: - determines network radio connectivity to discover radio neighbors of each node - assign collision free channels to links * centalized channel assignment * distributed assignment

17 SMACS= Neighbor Recovery+Channel Assignmet Infrastructure building protocol that forms a flat topology A distributed protocol which enables nodes to discover their neighbors and establish transmission/reception schedules for communicating them without the need for any local or global master nodes

18

19 EAR(Eavesdrop-And- Register)Algorithm Offers continuous service to the mobile nodes under both mobile and stationary constraints. Primary constraint: battery power; mobile and stationary sensors must be established with as few messages transmitted by stationary sensors as possible. Hand off may not be required. Mobile nodes have the registry of the neighbors. Acks are avoided by timeouts, thresholds.

20 Routing Multihop Routing - objective: to provide priority service with robustness on a long term basis - more energy will spent on route setup and maintenance Cooperative Routing - reducing overhead in setup since data traffic is light

21 Multihop Routing Minimum energy per packet Minimum cost per packet Creation of multiple paths Parameters: - energy resources estimated by maximum number of packets - additive QoS metric(higher metric= lower Qos) (assumed low mobility)

22 SAR(Sequential Assignment Routing) Selection of a path among multipath by the node which generates the packet Objective: to minimize the average weighted QoS metric throuhout the lifetime of the network Criteria: - energy resource - QoS metric - Priority level of a packet

23 Cooperative Signal Processing Noncoherent - raw sensor data will be preprocessed to be forwarded to central node - central node selection algorithms: * SWE(Single Winner Election) * ST(Spanning Tree) Coherent -Limited number of sensor generating data - Explicit computation of minimum energy paths - MWE() is used to decrease energy cost. -Longer delay, higher overhead, lower scalability.

24 References Katayoun Sohrabi, Jay Gao, Vishal Ailawadhi, and Gregory J.Pottie, “Protocols for Self organization of a Wireless Sensor network,” IEEE Pers Commun., Oct. 2000, pp Christopher A. St. Jean, “Self-Organization in Ad Hoc and Multihop Wireless Communication Networks,” Symposium on Multi-hop/Ad-hoc Wireless Networks, June 2002, France. J. Jamont and M. Occello, “Using Self-Organization for Functional Integrity Maintenance of Wireless Sensor Networks,” IEEE Proc., France, R.E. Van Dyck, “Detection Performance in Self-Organized Wireless Sensor Networks,” National Institute of Standards and Technology Gaithersburg, Maryland, USA

25 ROUTING Flooding Gossiping Spin Directed Diffusion Clustering

26 Flooding & Gossiping Flooding: –Diffuse copies of message to all neighbors –Problems: Implosion Overlap Resource Blindness Gossiping: –Diffuse one copy to random neighbors –Solves implosion problem –Problems: Overlap

27 SPIN Overcome the problems of flooding Negotiation and Resource-adaptation –Negotiation: helps ensure only useful information will be transferred –Resource manager: keeps track of resource consumption Disseminate information with low latency and conserve energy at the same time.

28 SPIN ADV, REQ, DATA Spin1: do not consider energy consumption Spin2: if energy is low level, reduce its participation in terms of energy, –Spin1 uses 25% as much energy than flooding –Spin2: 60% meta-data per unit energy than flooding.

29 Directed Diffusion Data centric Attribute-naming interest including timestamp, gradient, data rate, duration(lifetime) Reactive routing Neighbor-to-neighbor Can be efficient in highly dynamic networks(changes in topology is not important) trade off some energy efficiency for increased robustness and scale.

30 LEACH Clustering based Min. Energy dissipation Randomly select nodes as clusterheads Setup & steady phases Clusterhead advertise that they are clusterheads Based on signal strength(cluster members determined)

31 References C. Intanagonwiwat, R. Govindan, D. Estrin and J. Heidemann, “Directed Diffusion for Wireless Sensor Networking”, in IEEE/ACM Transactions on Networking, v.11, no. 1, February J. Kulik, W. Rabiner, and H. Balakrishnan, “Adaptive protocols for information dissemination in wireless sensor networks,” in Proc. 5th Annu. ACM/IEEE Int. Conf. Mobile Computing and Networking(MobiCom’99), Seattle, WA, 1999, pp. 174–185.

32 Dynamic Power Management in Wireless Sensor Networks A.Sinha and A.Chandrakasan, IEEE Design Test Comp.,Mar./Apr.2001 Massachusetts Institute of Technology

33 Description Energy savings via 5 power saving modes Intermode transition policies investigated

34 Sensor Network & Node Architecture CkCk Node k SensorA/DMicro-OS StrongARM Memory Radio Battery and DC/DC converter R

35 Communication Models 1) Direct Transmission 2) Multihop 3) Clustering

36 Useful Sleep States for the Sensor Nodes Sleep StateStrongARMMemorySensor, A-to-D converter Radio s0s0 Active OnTx,Rx s1s1 IdleSleepOnRx s2s2 Sleep OnRx s3s3 Sleep OnOff s4s4 Sleep Off Tx: Transmit Rx:Receive

37 Event Generation Model R: Temporal event behavior over the entire sensing region=> Poisson process with an average event rate lambda-tot Spatial distribution of events: independent probability distribution P XY (x,y) p ek =prob. that an event is detected by node k, given the fact that it occurred in R. =………. P k (t,n)= prob.that “n” events occur in time “t” at node k. P k (T th,0)= prob. of no events occurring in C k over threshold interval T th =…………… P th,k (t)= prob.that at least one event occurs in time t at node k =1- P k (T th,0)

38 State Transition Latency & Power Power t i ActiveIdleActive s 0 P 0 P k s k P k+1 s k+1 t 1 t 2 tau d,k tau u,k tau d,k+1 tau u,k+1

39 Steady State Shutdown Algorithm If(eventOccurred()=true){ processEvent(); ++eventCount; lambda_k=eventCount/getTimeElapsed(); for (k=4;k>0;k--){ if(computePth(Tth(k)) < pth0) sleepState(k); }

40 Missed Events p s4 =prob.that no events occur in t s4,k t s4 =time duration in s 4 mode =- ln(p s4 )/lamda k Transition Algorithm to almost-off state: No ComputePth(Tth(4))0 s 3 Yes Prob.(1-p s4 ) Sleep? S 3 Prob. p s4 Compute t s4,k s 4


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