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Department Development Perspective

Optimal Position Of Base Station In Wireless Sensor NetworkGuided byMs Nandini Maninarayana

Ashlin Janifer LoboUSN:4S014LDS0112/13/2014Department of ECE, SJEC, Vamanjoor1St Joseph Engineering CollegeVamanjoor, MangaloreDepartment of Electronics and Communication EngineeringUG Program Accredited By National Accreditation Board New Delhi Energy in WSN12/13/2014Department of ECE, SJEC, Vamanjoor8

Fig.1 An energy model [4]Dept Of ECE, SJEC, Vamanjoor8AbstractLifetime maximization and overall energy consumption minimization are two different problems in a WSN.Sensor nodes dissipates energy during sensing and transmission ,but transmission energy dominatesTherefore the optimal location of the base station is required.12/13/2014Department of ECE, SJEC, Vamanjoor3Introduction12/13/2014Department of ECE, SJEC, Vamanjoor4

Wireless sensor networks consists of a. Sensor node b. Base station Sensor a. consumes energy for event sensing, coding, modulation, transmission, reception and aggregation of data.12/13/2014Department of ECE, SJEC, Vamanjoor5Introduction (contd) b. limited Energy, Computation, Storage ,Transmission range, Bandwidth.

Base station a. data gathering, processing entity and communication link to larger network.12/13/2014Department of ECE, SJEC, Vamanjoor6Introduction (contd)

Introduction (contd)

Minimizing average energy consumption

Minimizing maximum energy consumption

Minimizing relative energy consumption12/13/2014Department of ECE, SJEC, Vamanjoor7

Energy in WSN (contd)In the transmission amplifier a. n = 2 free space los b. n = 4 multi-path loss Consumed amplifier energy (1)

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Energy in WSN (contd)Threshold distance is calculated

(2) = free space loss constant J/bit/m^2 = multi-path loss constant J/bit/m^4

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Energy in WSN (contd)L=number of bits, the energy used in transmission will be

(3)

To receive L message bits, the radio spends (4)

= the energy in J/bit 12/13/2014Department of ECE, SJEC, Vamanjoor11

WSN topology12/13/2014Department of ECE, SJEC, Vamanjoor12

Energy in WSN (contd) n nodes uniformly distributed in an M M area k number of clusters in the topology. An average of (n/k) nodes per cluster. a. one cluster head node b.( ) non-cluster head nodes. 12/13/2014Department of ECE, SJEC, Vamanjoor13

Energy in WSN (contd) = sum of the energy consumed in a. reception of data b. data aggregation c. transmission of the aggregated data (7)

EDA = energy for data aggregation

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Energy in WSN (contd)The energy consumption in a cluster for one round of transmission (8)

The energy consumption in the network for one round (9)12/13/2014Department of ECE, SJEC, Vamanjoor16

Energy in WSN (contd)Case 1: When all the nodes in a sensor network are near the base station, (10)

dj = distance between the cluster head and the base station.12/13/2014Department of ECE, SJEC, Vamanjoor17

Energy in WSN (contd)After (n/k) rounds, when every node has become a cluster head once, the total energy spent is

(11) .

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.

Energy in WSN (contd)Case 2: When the base station is far away from all the nodes, (12)

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Energy in WSN (contd) Case 3: When some nodes are near and some nodes are far away from the base station then (14)

node i and node j are from different setsP = nearer nodes and q=farther nodes

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Energy in WSN (contd) case 1 (15) case 2 (16) case 3 (17)12/13/2014Department of ECE, SJEC, Vamanjoor21

Base station location

Let n sensor nodes be uniformly distributed in a rectangular field

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Fig 2. Rectangular field [1]Base station location (contd..)The Euclidean distances between the base station and the nodes are d1, d2, d3, . . . , and dn (18)

Case 1( ; i): (19)12/13/2014Department of ECE, SJEC, Vamanjoor23

Base station location (contd)Case 2 ( ; i): When all the nodes are far away from the base station (20)Case 3 (Some nodes with and remaining nodes with ): (21)where p + q = n and p, q 1.

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Base station location (contd)Minimizing acoording to the domination in the energy expenditure a, p q, then the centroid of p nodes will be the optimal position. b. If q p, then the farther nodes will decide the optimal location for the base station12/13/2014Department of ECE, SJEC, Vamanjoor25

Base station location (contd..)When both types of nodes are equally dominating12/13/2014Department of ECE, SJEC, Vamanjoor26Step 1: Find centroid (Cx, Cy) of the nodes distributed in the field This is the point, where is minimized (22) (23)

Step 2:Find nodes less than distance from the centroid.12/13/2014Department of ECE, SJEC, Vamanjoor27

Algorithm for base station location

Algorithm (contd..)Step 3: Weights are calculated using centroid for all the nodes as

(24)

= distance between the ith node and the centroid.12/13/2014Department of ECE, SJEC, Vamanjoor28

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Algorithm (contd..)Fig.3 Square field [1]Algorithm (contd..)Let us consider a square field with length of side a. Let Only free space loss will be suffered by the transmission from all the nodes inside the fieldtwo nodes at , are taken in the field12/13/2014Department of ECE, SJEC, Vamanjoor30

base station location P(Px,Py) is given by (25)

(26)When Let nodes suffer free space loss and suffer multi-path loss.If the weight to is w

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Algorithm (contd..)Algorithm (contd..)P(Px, Py) is given by

(27)

(28)

w = , then Px = x2 and Py = y2. w = 0, then Px = x1 and Py = y1 12/13/2014Department of ECE, SJEC, Vamanjoor32

w = (29)

weighted average of node positions to the optimal position (xp, yp) for the base station

(30)

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Algorithm (contd..) (31) 12/13/2014Department of ECE, SJEC, Vamanjoor34

Algorithm (contd..) The optimal location of the base station can be obtained by using the algorithm and energy consumption of the nodes can be minimized 12/13/201435Department of ECE, SJEC, VamanjoorConclusionReferences[1]Two-tiered wireless sensor networks base station optimal positioning case study,R.K. Tripathi Y.N. Singh N.K. Verma, Department of Electrical Engineering, Indian Institute of Technology, Kanpur, Kanpur 208 016, India [2] Positioning of base stations in wireless sensor networks, Akkaya, K., Younis, M., Youssef, W, IEEE Commun. Mag., 2007, 45, (4), pp. 96102.[3] Optimal base-station locations in two-tiered wireless sensor networks, Pan, J., Cai, L., Hou, T., Shi, Y., Shen, S.X, IEEE Trans. Mob. Comput., 2005, 4, (5), pp. 458473..12/13/2014Department of ECE, SJEC, Vamanjoor36[4] An application specific protocol architecture for wireless microsensor networks, Heinzelman,W.R., Chandrakasan, A., Balakrishnan, H, IEEE Trans. Wirel. Commun., 2002, 1, (4), pp. 660670.[5] Energy efficient communication protocol for wireless microsensor networks, Heinzelman, W.R., Chandrakasan, A., Balakrishnan, H, Proc. Int. Conf. on System Sciences, , pp. 30053014.[6] Wireless communications: principles practice ,Rappaport, T, Prentice- Hall, Englewood Cliffs, NJ, 1996.

12/13/2014Department of ECE, SJEC, Vamanjoor37Wireless sensor networks are enabled by three trends Cheaper computation (Moores Law)Compact sensing (MEMS sensors)Wireless networking (low-power radios)

ApplicationsEnvironmental sensingHabitat monitoringPrecision agricultureMilitary operationsCondition-based maintenanceHealth care12/13/2014Department of ECE, SJEC, Vamanjoor38Range of Sensor Nodes Large Medium Small TinyComputation/memory Microprocessor8-bit microcontrollers Xscale processors Digital signal processors Memory Flash for non-volatile logging of sensor data Store and forward data from other nodes12/13/2014Department of ECE, SJEC, Vamanjoor39CommunicationRadio communication (some infrared) Power tradeoff with bandwidth More power, more range, more interference Less power, less range, may disconnect Protocol stack Reliability Routing Naming Broadcast, multicast, unicast12/13/2014Department of ECE, SJEC, Vamanjoor40BatteryRechargeable Li-ion, fuel cell, etc. Harvest from environment Solar, piezo (vibration), RF energy, etc.

.12/13/2014Department of ECE, SJEC, Vamanjoor41Leach12/13/2014Department of ECE, SJEC, Vamanjoor42

p = desired percentage of cluster heads, r = current round and G =number, which decides eligibility to become cluster head and form a set of nodes that have not been cluster heads. A node becomes a cluster head for the current round if the chosen random number is less than the following threshold.12/13/2014Department of ECE, SJEC, Vamanjoor43

SensorsEnabled by recentadvances in MEMSTechnologyIntegrated WirelessTransceiverLimited inEnergyComputationStorageTransmission rangeBandwidthWireless sensor networks may be considered a subset of Mobile Ad-hoc NETworks (MANET). Sensor networks are mainly used to collect information while MANETS are designed for distributed computing rather than information gathering. Sensor nodes mainly use broadcast communication paradigm whereas most MANETS are based on point-to-point communications. The number of nodes in sensor networks can be several orders of magnitude higher than that in MANETS . Sensor nodes may not have global identification (ID) because of the large amount of overhead and large number of sensors. 12/13/2014Department of ECE, SJEC, Vamanjoor44 Sensor nodes are much cheaper than nodes in a MANET and are usually deployed in thousands. Sensor nodes are limited in power, computational capacities, and memory where as nodes in a MANET can be recharged somehow. Usually, sensors are deployed once in their lifetime, while nodes in MANET move really in an Ad-hoc manner. Sensor nodes are much more limited in their computation and communication capabilities than their MANET counterparts due to their low cost.12/13/2014Department of ECE, SJEC, Vamanjoor45 Heuristic SearchAheuristicis a method that might not always find the best solutionbutis guaranteed to find a good solution in reasonable time. By sacrificing completeness it increases efficiency.Useful in solving tough problems whichcould not be solved any other way.solutions take an infinite time or very long time to compute.

12/13/2014Department of ECE, SJEC, Vamanjoor46Layered structure12/13/2014Department of ECE, SJEC, Vamanjoor47

Pegasis Greedy Chain Algorithm Start with node furthest away from BS Add to chain closest neighbor to this node that has not been visited Repeat until all nodes have been added to chain Constructed before 1st round of communication and then reconstructed when nodes di Data fusion at each node (except end nodes) Only one message is passed at every node Delay calculation: N units for an N-node network Sequential transmission is assumed12/13/2014Department of ECE, SJEC, Vamanjoor4812/13/2014Department of ECE, SJEC, Vamanjoor49

reflection, diffraction, and scattering.Due to multiple reflections from various objects, the electromagnetic waves travel along different paths of varying lengths. The interaction between these waves causes multipath fading at a specific location, and the strengths of the waves decrease as the distance between the transmitter and receiver increases.Propagation models have traditionally focused on predicting the average received signal strength at a given distance from the transmitter, as well as the variability of the signal strength in close spatial proximity to a particular loca12/13/2014Department of ECE, SJEC, Vamanjoor50phases are random, the sum of the contributions varies widely; for example, obeys a Rayleigh fading distribution.The free space propagation model is used to predict received signal strength when the transmitter and receiver have a clear, unobstructed line-of-sight path between themthe free space model predicts that received power decays as a function of the T-R separation distance raised to some power (i.e. a power law function). The free space power received by a receiver antenna which is separated from a radiating transmitter antenna by a distance d, is given by the Friis free space equation.12/13/2014Department of ECE, SJEC, Vamanjoor5112/13/2014Department of ECE, SJEC, Vamanjoor52

The Friis free space equation of shows that the received power falls offas the square of the T-R separation distance. This implies that the receivedpower decays with distance at a rate of 20 dB/decade.An isotropic radiator is an ideal antenna which radiates power with unitgain uniformly in all directions, and is often used to reference antenna gains inwireless systems.

SPIN : Sensor Protocols for Information via Negotiation. DD: Directed Diffusion RR.: Rumor Routing GBR : Gradient Based Routing. CADR : Constrained Anisotropic Diffusion Routing12/13/2014Department of ECE, SJEC, Vamanjoor53