Centralized Transmission Power Scheduling inWireless Sensor Networks

Qin WangComputer Depart., U. of Science & Technology BeijingEdward Y. HuaWireless Network Laboratory, Cornell University

OPLAB @IM.NTU 2

Outline

Introduction Assumptions RGOPC Evaluation Conclusion

OPLAB @IM.NTU 3

Introduction - DTX

Sink

kdkEdkE:(DTX) ioncommunicat Direct ampelecTT2),(

d1 d2

OPLAB @IM.NTU 4

Introduction - MTX

Sink

Minimum transmission energy (MTE)

OPLAB @IM.NTU 5

Assumptions

Network lifetime more than a fraction, e.g., 90%, of the nodes alive

Network Assumptions uniformly deployed sending data to the sink either directly or through

multiple hops transmit: sending packets generated by itself,

forward: sending packets generated by others energy-constrained

power-control mechanism (transmission power is adjustable)

Radio Model Assumptions:

kEkE

kdkEdkE

elecRR

ampelecTT

)(

),( 2

OPLAB @IM.NTU 6

RGOPC - Issues

To find the global optimized power criteria (GOPC) in a squared network case and a circular network case

To integrate the GOPC into the routing protocol (RGOPC) without extra cost

OPLAB @IM.NTU 7

GOPC - Squared

OPLAB @IM.NTU 8

GOPC - LP of Squared

>

ETi0

ZX ij

kddikEE nampelecTi02

0 ))1((

OPLAB @IM.NTU 9

GOPC - Circular

OPLAB @IM.NTU 10

GOPC - LP of Circular

OPLAB @IM.NTU 11

Transmission Power-based Locating/Addressing

Addressing scheme <number of hops, ID> <nh, xxxx> Measured by “Power Level 1”

Power criterion configuration file Addressing: From sink to Z1j, Z1j to Z2j, … Sink generates the GOPC by solving LP

sub-GOPC: nodes with the same nh Elow, Eup to (sink, n1, …,nh-1)

OPLAB @IM.NTU 12

sub-GOPC

By Xij?!

OPLAB @IM.NTU 13

RGOPC

Setup phase protocol location information acquisition and GOPC generation

Communication phase protocol look up power criterion configuration file to find nh2

remaining energy level ( Ec) between Elow, Eup of nh2 transmitting RTS to subGOPC (< nhnext, xxxx >) with power level Pc = nh_cur – nh_next replying CTS with address and remaining energy node with maximum remaining energy is chosen transmitting data packet

OPLAB @IM.NTU 14

sub-GOPC

How to select?

OPLAB @IM.NTU 15

Evaluation - Simulation Setting

Squared 100m×100m, sink is 40m away from the nearest node, basic hop distance dh is 10m, 100-500 sensor nodes are distributed uniformly, ERelec=0

Circular radius 100m, sink at the center, basic hop distance dh is 10m, 400-1000 nodes are distributed uniformly, ERelec=50nJ/bit

Every node generates 2000 bits of data ETelec= 50nJ/bit, εamp = 100 pJ / bit /m2 40000nJ is the expired threshold

OPLAB @IM.NTU 16

Simulation Result - Lifetime

OPLAB @IM.NTU 17

Simulation Result - Lifetime (cont’d)

OPLAB @IM.NTU 18

Simulation Result - Lifetime (cont’d)

OPLAB @IM.NTU 19

Simulation Result - Network Density

OPLAB @IM.NTU 20

Simulation Result - Network Density (cont’d)

OPLAB @IM.NTU 21

Simulation Result - Distribution of Nodes

* : alive (blue)

+: expired (green)

OPLAB @IM.NTU 22

Conclusion

Propose an energy-efficient scheme (RGOPC) that the lifetime of every node is almost the same

Simulation shows performance of RGOPC is superior density of network has no significant impact

No more overhead cost comparing with a location-based routing protocol