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Network Kernel Architectures
and Implementation(01204423)
Network Architecture
Chaiporn [email protected]
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
