Mobile-Assisted Localization by Stitching in Wireless Sensor Networks IEEE ICC 2011 Han Wang, Wangdong Qi, Kun Wang, Peng Liu, Li Wei and Yasong Zhu PLA Univ.of Sci.& Tech, Nanjing Univ. of Posts and Telecom Speaker: Wun-Cheng Li

Outline Introduction Goal Major Procedures in MALS ▫Subset Partitioning ▫Trajectory Design Simulation Conclusion 2

Introduction Localization is a crucial issue in wireless sensor networks as it provides support for different types of location-aware applications ▫ Position-based routing ▫ Monitoring ▫ Target tracking One way to acquire location information is to equip each sensor with a global positioning system (GPS). ▫ Cost effective Only a limited proportion of sensors, which are called anchors, are equipped with GPS 3

Introduction Traditional anchors are static, they will not move once deployed. In recent years, mobile assisted localization has been actively pursued. 4 Anchor Nodes Anchor Nodes

Problem A major problem with mobile assisted localization algorithms is the movement path design of the mobile anchors. This paper propose mobile assisted localization by stitching to accommodate non-uniform and irregular deployment scenarios. 5

Goals To propose an efficient localization algorithm ▫ Trajectory design for mobile anchor ▫ Less communication expense ▫ Less power cost 6

Assumptions Sensor nodes can find their neighbors and measure distances between them. 7

Overview 8 S1S1 S2S2 S3S3 Anchor Nodes V1V1 V4V4 orphan node trilateration subnet

Major Procedures in MALS Subset Partitioning ▫ When the anchor is placed in target terrain, it will broadcast “start” message all over the network. ▫ Sensor nodes initiate neighbor discovery after receiving “start” message and report neighborhood information back to the anchor. 9

Major Procedures in MALS Subset Partitioning 10 Anchor Nodes

Major Procedures in MALS Subset Partitioning 11

Major Procedures in MALS Subset Partitioning 12 Anchor Nodes

Major Procedures in MALS Subset Partitioning 13 Anchor Nodes orphan node trilateration subnet

SiSi SjSj ViVi VjVj Major Procedures in MALS Trajectory Design ▫ Moving between Localization Units 14 Anchor Nodes

Major Procedures in MALS Trajectory Design ▫ Moving Inside a Localization Unit 15 Anchor Nodes

Major Procedures in MALS Trajectory Design ▫ Moving Inside a Localization Unit 16 Anchor Nodes

Simulation Matlab 17 Parameter Settings Environmental scenarios100m x100m Anchors communication radius20m Nodes radius5~15m

Simulation Parameter Setup in SCAN 18 Scan resolution

Simulation Number of Anchor Positions Needed in Localization 19

Simulation Path Length Comparison 20

Conclusions This paper proposed a novel trajectory design scheme to accommodate practical environments by taking full advantage of network topology. Simulations demonstrate that our trajectory design outperforms previous approaches under various non- uniform and irregular deployment scenarios. 21

Thank you! 22