1 Neighbor Table Message Pool Contains Contains Reference to - PDF document

Tow ards a Sensor Netw ork Architecture: Low ering the Waistline Unifying Link • Lack of sensor net architecture Abstraction for • Monolithic protocols Wireless Sensor • No abstraction Netw orks • No modularity • No code reuse Chris Wilson Internet Architecture Sensor Net Architecture Network Network Network Protocol A Protocol B Protocol C Application HTTP, DNS, TFTP, POP3, SMTP… Transport TCP, UDP, DCCP… SP Network IP Link A Link B Link Ethernet, Wi-Fi, PPP, SLIP, FDDI… Challenges SP • Efficiency • Neighbor Management • Power Management • Cooperation between Link & Net • Handle Packets 1

Neighbor Table Message Pool • Contains • Contains – Reference to the next packet – Neighbor Address – Number of packets left – Schedule information – Next packet notification – Link quality • Network sets urgency and • Extensible reliability bits • Allows cooperation between • Link set congestion and phase Network and Link layers shift bits Implementation Link Protocols • Slotted protocol – IEEE 802.15.4 • Channel sampling protocol – B-MAC 802.15.4 B-MAC • Added synchronization and source • Inserts neighbors with schedule info information to header • Checks for messages or listen bit on • Extracts sync on long preambles neighbor frame • Use short preamble with sync • Beacons use broadcast neighbor or • Use long preamble with unknown unicasts round robin destinations or broadcasts or urgent • LQI metric for link quality • Use Acks for reliability bit • Uses Acks for reliability bit • RSSI and packet-error-rate estimate for link quality 2

B-MAC “Piggybacking” B-MAC “Piggybacking” Long B B A A short C C Netw ork Protocols MintRoute • Collection Routing • Broadcasts route updates and sends data – MintRoute • Data Dissemination • Use “find” for parent selection – Trickle • Data sent w/Reliability bit • Data Aggregation • Chooses neighbor with best EXT and hop count as parent – Synopsis Diffusion Trickle Synopsis Diffusion • Spreads new data to the entire • Uses order and duplicate network insensitive aggregates • Motes occasionally transmit • Robust to changing topology data description • Sends aggregates to collection • When something new is heard point take it and send descriptions • Requires a gradient to collection more aggressively point 3

B-MAC Comparison 15.4 Comparison MintRoute results Trickle Results • Stable • Lower Duty Cycle than w/o SP • Benefits from piggybacking MintRoute + SD Tenet • Architecture for multi-tier WSN • Abstracts away application specific code on motes • Not incompatible with SP Batching common messages together resulted in 35% power savings 4

Critique • Assumes fair play • What’s a Network Service Manager? • Timestamps • Security 5