CS541 Advanced Networking 1 A Real-Time Communication Architecture for Wireless Sensor Networks Neil Tang 4/22/2009

CS541 Advanced Networking 2 2 Please complete the online course survey at:

CS541 Advanced Networking 3 3 Outline  Reference  System Model  Design Goals  RAP  Simulation Results

CS541 Advanced Networking 4 Reference C. Lu, B. Blum, T. F. Abdelzaher, J. A Stankovic and T. He, RAP: a real- time communication architecture for large size wireless sensor networks IEEE RTAS’2002, pp

CS541 Advanced Networking 5 System Model  Large scale and high density network  Very limited energy  Queries are usually associated with timing requirements  Data aggregation  Multihop communication  Addressing based on locations  Congestion in “hot regions”

CS541 Advanced Networking 6 Design Goals  Provide general service APIs.  Maximize the number of packets meeting their end-to-end deadlines.  Scale well with a large number of nodes and hops.  Introduce minimum communication and processing overhead.

CS541 Advanced Networking 7 RAP Architecture

CS541 Advanced Networking 8 Query/Event Service API  query(attribute_list, area, timing_constraints, querier_loc)  register_event(event, area, query)

CS541 Advanced Networking 9 Location-Addressed Protocol  Similar to UDP except that messages are addressed by location instead of IP address.  Support three kinds of communications: unicast, area multicast and area anycast.

CS541 Advanced Networking 10 Geographic Forwarding (GF)  GF makes a greedy decision to forward a packet to a neighbor if 1) it has the shortest geographic distance to the packet’s destination among all immediate neighbors; and 2) it is closer to the destination than the forwarding node.  When such nodes do not exist, the GPSR protocol [16] can be used to route packets around the perimeter of the void region.

CS541 Advanced Networking 11 Velocity Monotonic Scheduling  Deadline-aware  Distance-aware

CS541 Advanced Networking 12 Velocity Monotonic Scheduling  Static Velocity Monotonic:  Dynamic Velocity Monotonic:  No synchronization is needed to determine the elapsed time.

CS541 Advanced Networking 13 Priority Queue  Single FCFS Queue: Packets need to be inserted in the order of their priorities.  Multiple FIFO Queues: Each queue corresponds to a fixed priority level. Each priority level corresponds to a range of requested velocities.  Time complexities?

CS541 Advanced Networking 14 MAC Layer Prioritization  Enhanced DCF (EDCF)  DIFS: DIFS = BASE_DIFS * PRIORITY  Backoff increase function: CW=CW*(2+(PRIORITY-1)/MAX_PRIORITY)

CS541 Advanced Networking 15 Summary  RAP provides general query and event service APIs.  RAP increases the number of packets meeting their end-to-end deadlines by prioritizing the transmission of contending packets based on their requested velocities.  RAP scales well in large-scale sensor networks since every algorithm/protocol only needs local information.

CS541 Advanced Networking 16 Simulation Settings  Radio transmission range: 30.5m  Packet size: B  Link bandwidth: 200kbps

CS541 Advanced Networking 17 Simulation Results

CS541 Advanced Networking 18 Simulation Results