Node Reclamation and Replacement for Long-lived Sensor Networks

Bin Tong, Wensheng Zhang, and Chuang WangDepartment of Computer Science, Iowa State University

Guiling WangDepartment of Computer Science, New Jersey Institute of Technology

IEEE SECON 2009

Outline Introduction Goal System Model Node reclamation and replacement The ARTS Scheme Performance Evaluation Conclusion

Introduction Wireless Sensor Network

Power by batteries

Introduction Wireless Sensor Network

Environmental sources Deployment Reclamation and Replacement

Introduction Motivation and Goal

Providing a guaranteed Quality of Service A sufficient number of sensor nodes being alive

Minimizing the overhead caused by the reclamation and replacement The travel distance of the MR is minimized in the long run

System Model System Architecture

The system consists of a mobile repairman (MR), an energy station (ES) A WSN composed of groups of sensors surrounding the posts The MR traverses the network periodically to reclaim sensors having low or no

energy and replace them with fully-charged sensors

group

Assumptions Time is divided into phases of a constant length. A certain number of phases co

mpose a round, the length of which is denoted as l. The MR visits each post at most once every round.

A sensor has two modes: active and sleep. At the beginning of each phase, all sensors in each group should wake up and p

articipate in the duty-cycle scheduling.

Node reclamation and replacement

Surveillance Number = 6

group

…phase1 phase2 phase i

Wait time

The ARTS Scheme Adaptive rendezvous-based two-tier scheduling scheme

Local-Tier Scheduling Global-Tier Scheduling

round j

round j+11. Visit time 2. Number of sensors to be reclaimed/replaced

residual energy

Collects information for the round j+2

phase 1phase 2

The ARTS Scheme Local-Tier Scheduling

Quality of Service is guaranteed ( ≧ Nmax)

Remaining energy in sensors to be reclaimed/replaced should be as small as possible

Initial phase j

Scheduling1. Nd

2. Surveillance number3. t

Scheduling phase j

Nd: the number of sensors in the groupt: the number of remaining phases before the next replacement/reclamation

Nmax × tδ

The ARTS Scheme Local-Tier Scheduling

Quality of Service is guaranteed ( ≧ Nmax)

Remaining energy in sensors to be reclaimed/replaced should be as small as possible

1

3

5

0

4

2

6

Nd : the number of sensors in the groupt : the number of remaining phases before the next replacement/reclamationei: the amount of sensor i remaining energyδ: be the amount of energy consumedby an active sensor per phase

Sorted

L1 = <u0, · · · , um−1>

ei ≧ tδ

L2 = <um, · · · , uNd-1>

ei ＜ tδ

Scheduling

check

remaining energy in L2

m × tδ

The ARTS Scheme Local-Tier Scheduling

Quality of Service is guaranteed ( ≧ Nmax)

Remaining energy in sensors to be reclaimed/replaced should be as small as possible

L1 L2 L1 L2 L2L1

δ=1, Nmax= 5

greedy scheduling policy:

Fail

6 (5-3)3*1=6≧ 2 ＜ (5-3)3*1=6

The ARTS Scheme Local-Tier Scheduling

Controlled-greedy Algorithm

δ=1, Nmax= 5

2 ＜ (5-3)3*1=6

x

The ARTS Scheme Global-Tier Scheduling

The total travel distance of the MR is minimized The remaining energy of sensors to be replaced is minimized

group i

round j

information of round j+1

visiting time and replacement number in round j +2 for group i

The ARTS Scheme Global-Tier Scheduling

The total travel distance of the MR is minimized The remaining energy of sensors to be replaced is minimized

Calculation of Replacement Numbers : Choose least energy sensors

l : the length of a roundτ : the lifetime of sensor if being active all the time

(l/τ) × Nmax= 3 × Nmax

Case: l >τ

Nmax

Case: l ≦τ

To guard against the worst case scenario when Nmax nodes are needed to be active all the time.

j j+1 j+2

time

j=1,2:

j >2:

The ARTS Scheme Global-Tier Scheduling

The total travel distance of the MR is minimized The remaining energy of sensors to be replaced is minimized

Calculation of the Travel Schedule for the MR Data Structure in round j+2

Table R

Deadline

e(i, p): the total residual energy in the sensors to be reclaimed/replaced in group gi at phase p

Data Structure in round j+2 G(V, E, W (V ), W (E), R)

V = {gi | 0 ≤ i ≤ n}

W (V) ={Nr(1, j+2), · · · , Nr(n, j+2)}

= (t1, t2, · · · , tn)︰ a visiting time vector

D = ︰ is the total traveling distance for the MR

= (2, 1 , 3, 4 )

g1

g2

g3g4

Nr(1, j+2)

Nr(2, j+2)

Nr(3, j+2)Nr(4, j+2)

g1

g2

g3g4

Nr(1, j+2)

Nr(2, j+2)

Nr(3, j+2)Nr(4, j+2)

The ARTS Scheme Global-Tier Scheduling

The total travel distance of the MR is minimized The remaining energy of sensors to be replaced is minimized

Calculation of the Travel Schedule for the MR How decide the vector to minimize the weight

g1

g2

g3g4

Nr(1, j+2)

Nr(2, j+2)

Nr(3, j+2)Nr(4, j+2)

Global-Tier Scheduling The total travel distance of the MR is minimized The remaining energy of sensors to be replaced is minimized

Calculation of the Travel Schedule for the MR

g1

g3

g7

g6

g2

g4

ES

Super Tour 1

Super Tour 2M

[10]

[10] T. Liebling, D. Naddef, and L. A. Wolsey, “On the capacitated vehicle routing problem,” Mathematical Programming, 2003

g5

Performance Evaluation Simulation Parameter

lifetime τ 4000 minutes

phase length 10 minutes

round l 4000 minutes

Nmax 8 sensors/group

1000 m

1000 m

36 groups

16 sensors40 sensors

Performance Evaluation Simulation ResultTradeoff between Residual Energy in Sensors to Be Reclaimed/Replaced and MR’s Travel Distance

Comparison with Optimal Solution

Performance Evaluation Simulation Result

Impact of MR’s Capacity

Impact of Round Length

Conclusion A node replacement and reclamation (NRR) strategy and an adaptive rende

zvous-based two-tier scheduling (ARTS) scheme to meet the challenges of designing an efficient WSN for long-term tasks

Extensive simulations have been conducted to verify the effectiveness and efficiency of the ARTS scheme.

Future Work Plan to explore other design choices for the NRR System, extend

the current design of the ARTS scheme, and set up real testbed to evaluate the design.

Thank you~