Network Kernel Architectures and Implementation (01204423) Network Architecture Chaiporn Jaikaeo...

Network Kernel Architectures

and Implementation(01204423)

Network Architecture

Chaiporn Jaikaeochaiporn.j@ku.ac.th

Department of Computer EngineeringKasetsart University

Materials taken from lecture slides by Karl and Willig

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Outline Network scenarios Optimization goals Design principles Gateway concepts

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Typical Views of WSN Self-organizing mobile ad hoc

networks (MANETs) Peer-to-peer networks Multi/mobile agent systems and

swarm intellegence

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Sensor Network Scenarios Sources: Any entity that provides

data/measurements Sinks: Nodes where information is

required

Source

SinkInternet

Sink

Source

Sink

Source

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Single-Hop vs. Multi-hop Multi-hop networks

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 E.g.,

collaborative networking, network coding

Source

Sink

Obstacle

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Multi-hopping Always Efficient? Obvious idea: Multi-hopping is more

energy-efficient than direct communication Suppose we put a relay at distance d/2 Energy for distance d is reduced from cd

to 2c(d/2)

c - some constant - path loss coefficient ( 2)

Usually wrong, or over-simplified Need to take constant offsets for

powering transmitter, receiver into account

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Multiple Sinks, Multiple sources

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Outline Network scenarios Optimization goals Design principles Gateway concepts

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Goal: Quality of Service QoS in WSN is more complicated

(compared to MANET) 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 Network should withstand failure of some

nodes

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Goal: Energy efficiency Many definitions

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

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Sharpening the Drop Sacrifice long lifetimes in return for

an improvement in short lifetimes

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Outline Network scenarios Optimization goals Design principles Gateway concepts

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Distributed Organization WSN participants should cooperate

in organizing the network Centralized approach usually not

feasible Potential shortcomings

Not clear whether distributed or centralized organization achieves better energy efficiency

Option: “limited centralized” solution Elect nodes for local

coordination/control Perhaps rotate this function over time

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In-Network Processing WSNs are expected to provide

information Gives additional options E.g., manipulate or process the data

in the network Main example: aggregation

Apply aggregation functions to a collection tree in a network

Typical functions: minimum, maximum, average, sum, …

Not amenable functions: median

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Aggregation Example

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Signal Processing Another form of in-network

processing E.g.,

Edge detection Tracking/angle detection of signal

source Exploit temporal and spatial

correlation Observed signals might vary only

slowly in time Signals of neighboring nodes are often

quite similar Compressive sensing

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Adaptive Fidelity Adapt data processing effort based

on required accuracy/fidelity E.g., event detection

When event occurs, increase rate of message exchanges

E.g., temperature When temperature is in acceptable

range, only send temperature values at low resolution

When temperature becomes high, increase resolution and thus message length

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Data Centric Networking Interactions in typical networks are

addressed to the identities of nodes Known as node-centric or address-

centric networking paradigm In WSN, specific source of events

might not be important Several nodes can observe the same

area Focus on data/results instead

Data-centric networking Principal design change

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Implementation Options Publish/subscribe (NDN – Named

Data Networking) 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 SQL-based request

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Outline Network scenarios Optimization goals Design principles Gateway concepts

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Gateways in WSN/MANET Allow remote access to/from the WSN Bridge the gap between different

interaction semantics E.g., data vs. address-centric networking

Need support for different radios/protocols

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Gatewaynodes

Internet

Gateway

WSN tunneling Use the Internet to “tunnel” WSN

packets between two remote WSNs

6LoWPAN IPv6 over Low-power Wireless

Personal Area Networks Nodes communicate using IPv6

packets An IPv6 packet is carried in the

payload of IEEE 802.15.4 data frames

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Example 6LoWPAN Systems

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Summary Network architectures for WSNs look quite

different from typical networks in many aspects

Data-centric paradigm opens new possibilities for protocol design