Centralized Transmission Power Scheduling in Wireless Sensor Networks Qin Wang Computer Depart., U. of Science & Technology Beijing Edward Y. Hua Wireless Network Laboratory, Cornell University
Outline Introduction Assumptions RGOPC Evaluation Conclusion
Introduction - DTX Sink d1 d2
Introduction - MTX Sink Minimum transmission energy (MTE)
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:
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
GOPC - Squared
GOPC - LP of Squared > E Ti0
GOPC - Circular
GOPC - LP of Circular
Transmission Power-based Locating/Addressing Addressing scheme Measured by “ Power Level 1 ” Power criterion configuration file Addressing: From sink to Z 1j, Z 1j to Z 2j, … Sink generates the GOPC by solving LP sub-GOPC: nodes with the same n h E low, E up to (sink, n 1, …,n h-1 )
sub-GOPC By X ij ?!
RGOPC Setup phase protocol location information acquisition and GOPC generation Communication phase protocol look up power criterion configuration file to find n h2 remaining energy level ( E c ) between E low, E up of n h2 transmitting RTS to subGOPC ( ) with power level P c = n h_cur – n h_next replying CTS with address and remaining energy node with maximum remaining energy is chosen transmitting data packet
sub-GOPC How to select?
Evaluation - Simulation Setting Squared 100m×100m, sink is 40m away from the nearest node, basic hop distance d h is 10m, sensor nodes are distributed uniformly, E Relec =0 Circular radius 100m, sink at the center, basic hop distance d h is 10m, nodes are distributed uniformly, E Relec =50nJ/bit Every node generates 2000 bits of data E Telec = 50nJ/bit, ε amp = 100 pJ / bit /m 2 40000nJ is the expired threshold
Simulation Result - Lifetime
Simulation Result - Lifetime (cont’d)
Simulation Result - Lifetime (cont’d)
Simulation Result - Network Density
Simulation Result - Network Density (cont’d)
Simulation Result - Distribution of Nodes * : alive (blue) +: expired (green)
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