Using Mobile Relays to Prolong the Lifetime of Wireless Sensor Networks. Wang Wei Vikram Srinivasan Chua Kee-Chaing

Transcription

1 Using Mobile Relays to Prolong the Lifetime of Wireless Sensor Networks Wang Wei Vikram Srinivasan Chua Kee-Chaing

2 Overview The motivation of mobile relay The performance analysis for mobile relay in the ideal case Simulation and comparisons

3 The motivation of mobile relay Homogeneous Network Simple and cheap sensors Achieve performance requirements through over-provisioning Heterogeneous Network Use a small number of resource rich sensors to improve the performance Use controlled mobility to dynamically allot the resources Adding one resource rich nodes may save many simple sensors

4 Our approach and main results Use rechargeable mobile sensors to add more energy to the network Theoretically one mobile relay can improve lifetime four times in large networks Simulation shows more than two times improvement

5 How to add more energy? Identify the energy bottlenecks where nodes die quickly Use mobile relays to take over the task of those critical sensors Prevent the network from partitioning

6 A example of bottleneck points Network component I Mobile Sensor Relay A Mobile Sensor Relay B Sensor Mobile relay A and stand B can sustain on the point for time of T sensor A, B, Sensor A B work for time T Network component II Total lifetime is 2T with one mobile relay

7 General Bottleneck in Sensor Network Sink r Sensors around the sink dies faster than others! 3r 5r

8 Lifetime bounds Network of static sensors Depends on the immediate neighbors of the sink The neighbors need to carry data 2 for all the sensors in the network R T E 2 Re

9 Lifetime bounds Network with one mobile relay Static node Mobile Relay Sink r 3r

10 Lifetime bounds Network with one mobile relay Depends on the sensors within two hops range of the sink Four times longer than the static network T 4E 2 Re

11 Can we achieve the bounds? Basic approach -- Use only one static node with the mobile relay to build a bridge to deliver the packet over the bottleneck area -- Aggregate the traffic to that bridge so that all other critical nodes can rest Problem to solve -- How to move the mobile relays and build the bridge? -- Will other sensors die faster due to the longer route taken?

12 Building bridges to the sink r We can build 4r bridges in total 3r

13 Aggregating the packets n a Method 1 (ARA) All static sensors help to deliver the packets to the bridge O

14 Aggregating the packets r D n a Method 2 (ARALN) Only nodes near the sink need to know the position of the mobile relay f k O

15 Achievable network lifetime with one mobile relay T = 4E 16E 2 Re 4 Re Asymptotically four times the static network lifetime when R is large

16 Network with more than one mobile relays Mobile 1 Mobile 2 Extend lifetime through 2 mobile relays With m mobile relays the network lifetime can be extended by 4m times r 3r 5r 7r 9r

17 Simulations on finite networks Compare with energy conserving routing For mobile relay, solve an optimization problem Maximize t k k k st.. x x = s t i, k j k i ij ji i k j x 0 ( i, j), k k ij j x e E i k ij 0

18 Improvements under different networks Lifetime Improvement 180% 170% 160% 150% 140% 130% 120% 110% 100% 90% 80% 70% Circular network ( =4) Circular network ( =5) Square network ( =4) 60% R (Network Radius)

19 Comparing with other methods Minimal hop Routing Energy conserve Routing Limit With one Mobile Relay Mobile Sink Normalized Lifetime

20 Mobile relay or Mobile sink? Mobile Sink Better improvement on lifetime Robust improvement is O (R) Mobile Relay the network can operate without the mobile relay The ability to heal topology defects Small moving areas mobile relay only need to move in a small area Fewer impacted static nodes

21 Conclusion Resource rich nodes can significantly improve the network performance With one mobile relay, we can gain four times lifetime Controlled mobility is an important issue for dynamic assignment of resources

22 Future Works Distributed routing and mobility algorithms for mobile relay approach Mobile relays with longer transmission range Dynamically adjust to time varying traffic flows Collaboration of multiple mobile relays

23 Thank you!