Network Kernel Architectures and Implementation 01204423 Network Architecture

Network Kernel Architectures and Implementation (01204423) Network Architecture Chaiporn Jaikaeo chaiporn. j@ku. ac. th Department of Computer Engineering Kasetsart University Materials taken from lecture slides by Karl and Willig

Outline l l Network scenarios Optimization goals Design principles Gateway concepts 2

Typical Views of WSN l l l Self-organizing mobile ad hoc networks (MANETs) Peer-to-peer networks Multi/mobile agent systems and swarm intellegence 3

Sensor Network Scenarios l l Sources: Any entity that provides data/measurements Sinks: Nodes where information is required Source Sink Internet 4

Single-Hop vs. Multi-hop l Multi-hop networks Ø Ø Ø l Send packets to an intermediate node Intermediate node forwards packet to its destination Store-and-forward multi-hop network Store & forward multi-hopping NOT the only possible solution Ø E. g. , collaborative networking, network coding Sink Source Obstacle 5

Multi-hopping Always Efficient? l Obvious idea: Multi-hopping is more energyefficient than direct communication Ø Ø Suppose we put a relay at distance d/2 Energy for distance d is reduced from cd to 2 c(d/2) § § l c - some constant - path loss coefficient ( 2) Usually wrong, or over-simplified Ø Need to take constant offsets for powering transmitter, receiver into account 6

Multiple Sinks, Multiple sources 7

Outline l l Network scenarios Optimization goals Design principles Gateway concepts 8

Goal: Quality of Service l Qo. S in WSN is more complicated (compared to MANET) Ø Ø Ø l Event detection/reporting probability Event classification error, detection delay Probability of missing a periodic report Approximation accuracy (e. g, when WSN constructs a temperature map) Tracking accuracy (e. g. , difference between true and conjectured position of the pink elephant) Related goal: robustness Ø Network should withstand failure of some nodes 9

Goal: Energy efficiency l Many definitions Ø Ø Energy per correctly received bit Energy per reported (unique) event Delay/energy tradeoffs Network lifetime § § § Time to first node failure Network half-life (how long until 50% of the nodes died? ) Time to partition Time to loss of coverage Time to failure of first event notification 10

Sharpening the Drop l Sacrifice long lifetimes in return for an improvement in short lifetimes 11

Outline l l Network scenarios Optimization goals Design principles Gateway concepts 12

Distributed Organization l WSN participants should cooperate in organizing the network Ø l Potential shortcomings Ø l Centralized approach usually not feasible Not clear whether distributed or centralized organization achieves better energy efficiency Option: “limited centralized” solution Ø Ø Elect nodes for local coordination/control Perhaps rotate this function over time 13

In-Network Processing l WSNs are expected to provide information Ø Ø l Gives additional options E. g. , manipulate or process the data in the network Main example: aggregation Ø Ø Ø Apply aggregation functions to a collection tree in a network Typical functions: minimum, maximum, average, sum, … Not amenable functions: median 14

Aggregation Example 1 1 3 1 1 6 1 1 15

Signal Processing l l Another form of in-network processing E. g. , Ø Ø l Exploit temporal and spatial correlation Ø Ø l Edge detection Tracking/angle detection of signal source Observed signals might vary only slowly in time Signals of neighboring nodes are often quite similar Compressive sensing 16

Adaptive Fidelity l l Adapt data processing effort based on required accuracy/fidelity E. g. , event detection Ø l When event occurs, increase rate of message exchanges E. g. , temperature Ø Ø When temperature is in acceptable range, only send temperature values at low resolution When temperature becomes high, increase resolution and thus message length 17

Data Centric Networking l Interactions in typical networks are addressed to the identities of nodes Ø l In WSN, specific source of events might not be important Ø l Known as node-centric or address-centric networking paradigm Several nodes can observe the same area Focus on data/results instead Data-centric networking Ø Principal design change 18

Implementation Options l Publish/subscribe (NDN – Named Data Networking) Ø Ø l Nodes can publish data, can subscribe to any particular kind of data Once data of a certain type has been published, it is delivered to all subscribers Databases Ø SQL-based request 19

Outline l l Network scenarios Optimization goals Design principles Gateway concepts 20

Gateways in WSN/MANET l l Allow remote access to/from the WSN Bridge the gap between different interaction semantics Ø l E. g. , data vs. address-centric networking Need support for different radios/protocols 21

WSN tunneling l Use the Internet to “tunnel” WSN packets between two remote WSNs Internet Gateway nodes Gateway 22

6 Lo. WPAN l l l IPv 6 over Low-power Wireless Personal Area Networks Nodes communicate using IPv 6 packets An IPv 6 packet is carried in the payload of IEEE 802. 15. 4 data frames 23

Example 6 Lo. WPAN Systems 24

Summary l l Network architectures for WSNs look quite different from typical networks in many aspects Data-centric paradigm opens new possibilities for protocol design 25