A Survey on Sensor Networks Rick Han CSCI 7143 Secure Sensor Networks Fall 2004

Introduction Overall architecture Sensor node components Sensor nets vs. traditional ad hoc nets Design factors Protocol stack Physical layer Data link layer Network layer Transport layer Application layer Conclusion

Differences Between Sensor Nets and Ad Hoc Nets Greater number of sensor nodes Sensor nodes are densely deployed Sensor nodes are failure-prone Topology of sensor net changes frequently Broadcast, not point-to-point Sensor node limitations: power, computational capabilities, memory Potentially, no global identification for sensor nodes

Sensor Network Overview

Sensor Node Components

Design Factors Fault Tolerance Scalability Production Costs Hardware Constraints Sensor Network Topology Transmission Media Power Consumption

Protocol Stack

Protocol Stack: Physical Layer Frequency selection Carrier frequency generation Signal detection Modulation Encryption Responsible for:

Protocol Stack: Physical Layer Hardware cost How do we get down to $1/node? Radio Ultrawideband? Zigbee/IEEE Issues:

Protocol Stack: Data Link Layer The multiplexing of data streams Data frame detection Medium access * Error control * Responsible for:

Data Link Layer: Medium Access Control Creation of the network infrastructure Fair and efficient sharing of of communication resources between sensor nodes Goals:

Data Link Layer: Medium Access Control Cellular system - single hop network is impractical for sensor networks Power conservation is not stressed Security is not considered! WEP for is broken Do we care about link layer security? Problems with existing MAC protocols:

Data Link Layer: Medium Access Control Bluetooth and Mobile Ad Hoc Network (MANET) Both technologies are designed for smaller numbers of nodes Power consumption is still an issue Current technology:

Data Link Layer: Medium Access Control MAC for sensor networks Self-Organizing Medium Access Control for Sensor Networks (SMACS) and the Eavesdrop-And-Register (EAR) Algorithm CSMA-Based Medium Access Hybrid TDMA/FDMA-Based Alternative MAC schemes:

Data Link Layer: Medium Access Control Basic strategy: turn off radio transmitter when idle This can be ineffective due to startup costs Dynamic power management schemes may provide an answer Power Savings:

Data Link Layer: Medium Access Control MAC for mobile sensor networks Power saving modes Link-layer ARQ and FEC Issues:

Protocol Stack: Network Layer Power efficiency Data-centric nodes Data aggregation is not always desirable Attribute-based addressing and location awareness Design principles:

Minimum Energy Routing Maximum PA route Minimum energy route Minimum hop (MH) route Maximum minimum PA node route

Directed Diffusion Route based on attributes and interests

Protocol Stack: Network Layer Maximum PA route Minimum energy route Minimum hop (MH) route Maximum minimum PA node route Approaches:

Protocol Stack: Network Layer Data-centric routing Directed Diffusion Data Aggregation Small minimum energy communication network (SMECN) Flooding Gossiping Sensor protocols for information via negotiation (SPIN) Sequential assignment routing (SAR) Low-Energy Adaptive Clustering Hierarchy (LEACH) Schemes:

Protocol Stack: Transport Layer End-to-end Reliability Multi-hop retransmission Congestion End-to-end security Like SSL: authentication, encryption, data integrity

Protocol Stack: Application Layer Sensor network management Database queries Time synchronization/calibration? Other?

Omissions Operating system discussion is missing TinyOS MANTIS OS Smart Card OS Security Encryption Authentication Data Integrity Availability – DOS attacks Also, Non-repudiation and Authorization

Conclusion Overall architecture Sensor node components Sensor nets vs. traditional ad hoc nets Design factors Protocol stack