1. Variable Bandwidth Allocation Scheme for Energy Efficient Wireless Sensor Network SeongHwan Cho, Kee-Eung Kim Korea Advanced Institute of Science and Technology (KAIST), Samsung Advanced Institute of Technology ICC 2005 Speaker ： Shih-Yun, Hsu

2. Outline  Introduction  Goal  Assumption  Energy consumption vs Bandwidth  Variable Bandwidth Allocation (VBA)  Bandwidth Allocation Algorithm  Simulation Results  Conclusions

3. Introduction  The characteristics of the sensor network  Small packets (hundreds of bits)  Short transmission range (< 10m)  Low mobility  Years of lifetime with small energy resource  Distributed redundantly  Cluster

4. Introduction  An Application-Specific Protocol Architecture for Wireless Microsensor Networks  IEEE Trans. on wireless communications, 2002  TDMA scheme with DSSS in a cluster  Avoiding inter-cluster interference  Advantage  Energy efficient  Disadvantage  Increases the packet size  Aggravates time synchronization problems

5. Introduction  [5][6][7] are aimed at a general sensor network with multi-hop routing  Do not consider  Bandwidth utilization to minimize energy consumption

6. Goal  Proposes a mechanism  Clustering  Variable bandwidth allocation  Time-frequency slot assignment

7. Assumption  There are many frequency bands available  The network environment bases on cluster structure

8. Energy consumption vs Bandwidth  6 sensors  100 bits packet  100 bps  Using hybrid FDM-TDM method  Frame time = 10ms

9. Energy consumption vs Bandwidth

10.  R E ： event rate  N sync ： the number of synchronizations per second  ρ ： the error in the reference crystal oscillator

11. Energy consumption vs Bandwidth  M ： the number of channels available  N ： the total number of sensors  R max ： the maximum event rate of the sensors

12. Energy consumption vs Bandwidth

14. Variable Bandwidth Allocation (VBA)  Constant bandwidth allocation (CBA)  Allocates equal amount of frequency bands to the clusters regardless of its node density

15. Variable Bandwidth Allocation (VBA)

17. Bandwidth Time

18. Variable Bandwidth Allocation (VBA)

19. Bandwidth Allocation Algorithm  Single macrocluster slot assignment  Pairwise joint macrocluster slot assignment  Global network slot allocation

20. Bandwidth Allocation Algorithm  Single macrocluster slot assignment

21. Bandwidth Allocation Algorithm  Pairwise joint macrocluster slot assignment

22. Bandwidth Allocation Algorithm ABC Θ1Θ1 Θ2Θ2

23. ABC Θ1Θ1 Θ2Θ2 Θ j = Θ 2, n j =3 Θ i = Θ 1, n i =2 n i < n j B T frame

24. Bandwidth Allocation Algorithm ABC Θ1Θ1 Θ2Θ2 Θ j = Θ 1, n j =2 Θ i = Θ 2, n i =3 n i > n j T frame B

25. Bandwidth Allocation Algorithm  Global network slot allocation

26. Bandwidth Allocation Algorithm

27. Simulation Results  25 clusters and 750 sensor nodes  Averaging 100 different simulations for each standard deviation

28. Simulation Results

30. Conclusions  A variable fine-grain bandwidth allocation scheme is proposed for a collaborative sensor network with multiple clusters  This scheme reduces the power consumption of the network by exploiting the fact that power consumption from synchronization can be reduced if more bandwidth is available

31. Thank You!!