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




Network scenarios
Optimization goals
Design principles
Gateway concepts
2
Typical Views of WSN



Self-organizing mobile ad hoc networks
(MANETs)
Peer-to-peer networks
Multi/mobile agent systems and swarm
intellegence
3
Sensor Network Scenarios


Sources: Any entity that provides
data/measurements
Sinks: Nodes where information is required
Source
Source
Sink
Sink
Source
Sink
Internet
4
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
Sink
Source
Obstacle
5
Multi-hopping Always Efficient?

Obvious idea: Multi-hopping is more energyefficient 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
6
Multiple Sinks, Multiple sources
7
Outline




Network scenarios
Optimization goals
Design principles
Gateway concepts
8
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
9
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
10
Sharpening the Drop

Sacrifice long lifetimes in return for an
improvement in short lifetimes
11
Outline




Network scenarios
Optimization goals
Design principles
Gateway concepts
12
Distributed Organization

WSN participants should cooperate in
organizing the network


Potential shortcomings


Centralized approach usually not feasible
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
13
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
14
Aggregation Example
1
1
1
1
3
1
1
6
1
1
1
1
15
Signal Processing


Another form of in-network processing
E.g.,



Exploit temporal and spatial correlation



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


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
17
Data Centric Networking

Interactions in typical networks are
addressed to the identities of nodes


In WSN, specific source of events might not
be important


Known as node-centric or address-centric
networking paradigm
Several nodes can observe the same area
Focus on data/results instead
 Data-centric networking
 Principal design change
18
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
19
Outline




Network scenarios
Optimization goals
Design principles
Gateway concepts
20
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
21
WSN tunneling

Use the Internet to “tunnel” WSN packets
between two remote WSNs
Internet
Gateway
nodes
Gateway
22
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
23
Example 6LoWPAN Systems
24
Summary


Network architectures for WSNs look quite
different from typical networks in many aspects
Data-centric paradigm opens new possibilities for
protocol design
25