Routing

Mona mohamed ragheb
Routing protocols in WSN

Agenda
2
 Introduction
 Routing challenges in WSN
 Flat Routing
 Hierarchical Routing
 Location-based Routing
 Routing Protocols Based on Protocol Operation
 some Routing protocols
 Conclusion
 References

3
 Routing is a process of selecting paths in a
network along which to send data traffic
 First, it is not possible to build a global addressing
scheme for a large number of sensor nodes. Thus,
traditional IP-based protocols may not be applied to
WSNs. In WSNs, sometimes getting the data is more
important than knowing the IDs of which nodes sent the
data.
 Second, in contrast to typical communication networks,
almost all applications of sensor networks require the
flow of sensed data from multiple sources to a particular
Introduction

4
 Routing protocols in WSNs Differ depending on the
application and network architecture
 sensor nodes are tightly constrained in terms of energy,
processing, and storage capacities. Thus, they require carefully
resource management.
 position awareness of sensor nodes is important since data
collection is normally based on the location.
 data collected by many sensors in WSNs is typically based
on common phenomena, hence there is a high probability
that this data has some redundancy
 Trade-offs between energy and communication overhead
savings

Routing challenges and design
issues
5
 Node deployment
 Energy consumption without losing accuracy
 Data reporting method
 Node/link heterogeneity
 Scalability
 Data aggregation
 Quality of service

issues
6
 Node deployment
 Manual deployment
 Sensors are manually deployed
 Data is routed through predetermined path
 Random deployment
 Optimal clustering is necessary to allow connectivity &
energy-efficiency
 Multi-hop routing

issues
7
 Data reporting method
Application-specific:
• Time-driven: Periodic monitoring
• Event-driven: Respond to sudden changes
• Query-driven: Respond to queries
• Hybrid (combination of delivery models)

issues
8
 Node/link heterogeneity
 Depending on the application, a sensor node can
have a different role or capability such as relaying,
sensing and aggregation
 three functionalities at the same time on a node
might quickly drain the energy of that node.
 Combining these capabilities on one node raises a
challenge for routing protocols.
 For example, hierarchical protocols designate a
cluster head node

issues
9
 Fault tolerance
 The failure of sensor nodes should not affect the
overall task of the sensor network

issues
10
Network dynamics
 Routing messages from or to moving nodes is
more challenging since route and topology
stability become important issues
 Moreover, the phenomenon can be mobile
(e.g., a target detection/ tracking application).

issues
11
 Connectivity
High density  high connectivity
Some sensors may die after consuming their
battery power
Connectivity depends on possibly random
deployment

issues
12
 Coverage
 An individual sensor’s view is limited
 Area coverage is an important design factor
 Data aggregation Since sensor nodes may generate
significant redundant data, similar packets from
multiple nodes can be aggregated to reduce the
number of transmissions.
 Data aggregation is the combination of data from
different sources according to a certain
aggregation function.
 Quality of Service
 Bounded delay
 Energy efficiency for longer network lifetime

13
Routing Protocols in WSNs: A
taxonomy

14
 Proactive protocols :compute all the routes before they
are really needed and then store these routes in a
routing table in each node. When a route changes, the
change has to be propagated throughout the network.
Since a WSN could consist of thousands of nodes, the
routing table that each node would have to keep could
be huge and therefore proactive protocols are not suited
to WSNs.
 Reactive protocols compute routes only when they are
needed.
 Hybrid protocols use a combination of these two ideas.

Routing protocol survey
15
 Traditional technique
 Flooding
 Gossiping
 Current routing technique
 Flat-routing
 Hierarchical-routing
 Location-based routing
[1]Ian F. Akyildiz, Weilian Su, Yogesh Sankarasubramaniam, and Erdal Cayirci Georgia Institute of Technology” A Survey on Sensor Networks” IEEE
Communications Magazine • August 2002

Flooding(1/4)
16
• Flooding is the classic approach for dissemination
without the need for any routing algorithms and
topology maintenance
• Source node sends data to all neighbors
• Receiving node stores and sends data to all its
neighbors
• Disseminate data quickly
 drawbacks:
• Implosion
• Overlap
• Resource blindness

Implosion(2/4)
1
7
Node
The direction
of data sending
The connect
between nodes
A
CB
D
x
x x
x

Overlap(3/4)
1
8
q
r
s
(q, r) (s, r)
Node
The direction
of data sending
The connect
between nodes
The searching
range of the
node
A B
C

Resource blindness(4/4)
1
9
 In flooding, nodes do not modify their activities
based on the amount of energy available to them.
 A network of embedded sensors can be
resource-aware and adapt its communication
and computation to the state of its energy
resource.

Gossiping
20
 A slightly enhanced version of flooding where
the receiving node sends the packet to a
randomly selected neighbor which picks
another neighbor to forward the packet to and
so on.
Advantage: avoid the implosion
Drawback: Transmission delay

Router protocol survey
21
 Traditional routing technique
Flooding
Gossiping
 Current routing technique[1]
Flat-routing
Hierarchical-routing
Location-based routing
[1]JAMAL N. AL-KARAKI, AHMED E. KAMAL,” ROUTING TECHNIQUES IN WIRELESS SENSOR NETWORKS: A SURVEY”,
IEEE Wireless Communications • December 2004

22
 Each node plays the same role (Each node needs to
know only its neighbors)
 Data-centric routing
In data-centric routing, the sink sends queries to certain
regions and waits for data from the sensors located in
the selected regions.
 Save energy through data negotiation and elimination of
redundant data
 Protocols
 SPIN (Sensor Protocols for Information via Negotiation)
 DD (Directed diffusion)
 Rumor routing
Flat-routing (Data centric )

Sensor protocols for information via
negotiation (SPIN)
23
 Features
 Negotiation
 Before transmitting data, nodes negotiate with each other to
overcome implosion and overlap
 Only useful information will be transferred
 Observed data must be described using a meta-data
 Resource adaptation
 Each sensor node has resource manager
 monitoring their own energy resources may reduce certain
activities when energy is low
To extend the operating lifetime of the system
 SPIN Message
 ADV – new data advertisement
 REQ – request for ADV data
 DATA – actual data message Contain actual sensor data with a
meta-data header
 ADV, REQ messages contain only meta-data

negotiation (SPIN)
24
• Operation process
Step1
ADV
Step3
DATA
Step2
REQ
Step4
ADV
Step5
REQ
Step6
DATA

negotiation (SPIN)
25
 Resource adaptive algorithm
 When energy is plentiful
 Communicate using the 3-stage handshake protocol
 When energy is approaching a low-energy threshold
 If a node receives ADV, it does not send out REQ
 Energy is reserved to sensing the event
 Advantage
 Each node only needs to know its one-hop neighbors
 Significantly reduce energy consumption compared to flooding
 Drawback
- If the node interested in the data are far from the source, data will not
be delivered
- Large overhead
 Data broadcasting
-cannot guarantee delivery of data.

Flat-routing
26
 SPIN (Sensor Protocols for Information via
Negotiation)
 DD (Directed diffusion)
 Rumor routing

Directed Diffusion (DD) Feature
 Data-centric routing protocol
 A path is established between sink node and source
node
 Localized interactions
 The propagation and aggregation procedures are
all based on local information
 Four elements
 Interest
 A task description which is named by a list of
attribute-value pairs that describe a task
 Gradient
 Path direction, data transmission rate
 Data message
 Reinforcement
 To select a single path from multiple paths
27

Directed Diffusion (DD)
28
 Basic scheme
SinkSource
Step 1 : Interest propagation
Interests
Event
SinkSource
Step 2 : Initial gradients setup
Gradients
Event
Low rate
SinkSource
Step 3 : Data delivery along reinforced path
Event
High rate

Directed Diffusion (DD)
29
 Advantage
 Small delay
 Always transmit the data through shortest path
 Robust to failed path
 Drawback
 Imbalance of node lifetime
 The energy of node on shortest path is drained faster than
another
 Time synchronization technique
 To implement data aggregation
 Matching data to queries might require some extra overhead

Rumor Routing
Variation of directed diffusion
 Don’t flood interests (or queries)
 Flood events when the number of events is small
but the number of queries large
 Route the query to the nodes that have observed
a particular event
 Long-lived packets, called agents(Set up path by
random walk, Aggregate paths), flood events
through the network
 When a node detects an event, it adds the event
to its events table, and generates an agent
 Agents travel the network to propagate info about
local events
 An agent is associated with TTL (Time-To-Live) 30

Rumor Routing
31
 Basic scheme
 Each node maintain
 A lists of neighbors
 An event table
 When a node detects an event
 Generate an agent
 Let it travel on a random path
 The visited node form a gradient to the
event
 When a sink needs an event
 Transmit a query
 a node knowing the route to a
corresponding event can respond by
looking up its events table
When a node receives query  checks
its table and returns source –
destination path

Rumor Routing
32
 No need for query flooding 
 Only one path between the source and sink  
 Rumor routing works well only when the number of events is
small 
 Cost of maintaining a large number of agents and large event
tables will be prohibitive 
 Heuristic for defining the route of an event agent highly affects
the performance of next-hop selection 

33
 Flooding
 Gossiping
 Flat-routing
 Hierarchical-routing
 Location-based routing

Hierarchical-routing
34
 LEACH (Low Energy Adaptive Clustering
Hierarchy)
 PEGASIS (Power-Efficient Gathering in Sensor
Information Systems)
 TEEN(APTEEN) (Threshold-Sensitive Energy
Efficient Protocols)

LEACH (Low Energy Clustering Hierarchy)
35
 Cluster-based protocol
 Each node randomly decides to become a cluster heads (CH)
 CH chooses the code to be used in its cluster
 CDMA between clusters
 CH broadcasts Adv; Each node decides to which cluster it belongs
based on the received signal strength of Adv
 Nodes can sleep when its not their turn to xmit
 CH compresses data received from the nodes in the cluster and
sends the aggregated data to BS
 CH is rotated randomly

LEACH
36
 Advantages
 Increases the lifetime of the network
 Even drain of energy
 Energy saving due to aggregation by CHs
 Disadvantages
 LEACH assumes all nodes can transmit with enough power
to reach BS if necessary (e.g., elected as CHs)
 Each node should support both TDMA & CDMA
 Need to do time synchronization
 Nodes use single-hop communication

Comparison between SPIN, LEACH &
Directed Diffusion
SPIN LEACH Directed
Diffusion
Optimal
Route
No No Yes
Network
Lifetime
Good Very good Good
Resource
Awareness
Yes Yes Yes
Use of
meta-data
Yes No Yes
37

Power-Efficient Gathering in Sensor
Information Systems (PEGASIS)
38
 Only one node transmits to BS
 When a node dies, the chain is reconstructed in the same
manner to bypass the dead node.
• Data aggregation in the chain  one node sends the data to
the base station
 Performance
 PEGASIS Outperforms LEACH
 By eliminating the overhead of dynamic cluster formation
 By minimizing the total sum of transmission distances
 Decrease the delay for the packets during transmission to the base
station
 Problem
 the single leader can become a bottleneck.
 Scalability problem
 Excessive delay for distant nodes in the chain

The TEEN Protocol
39
 Threshold sensitive Energy Efficient sensor Network
protocol.
 Proactive Protocols (LEACH)
 The nodes in this network periodically switch on their sensors
and transmitters, sense the environment and transmit the data
of interest.
 Reactive Protocols (TEEN)
 The nodes react immediately to sudden and drastic changes
in the value of a sensed attribute.

Multi-level hierarchical clustering in TEEN
& APTEEN
40

TEEN - Functioning
41
 the cluster-head broadcasts two thresholds to
its members:
 Hard Threshold (HT)
 This is a threshold value for the sensed attribute.
 It is the absolute value of the attribute beyond which, the
node sensing this value must switch on its transmitter and
report to its cluster head.
 Soft Threshold (ST)
 This is a small change in the value of the sensed attribute
which triggers the node to switch on its transmitter and
transmit.

TEEN - Hard Threshold
42
 The first time a parameter from the attribute set
reaches its hard threshold value, the node
switches on its transmitter and sends the sensed
data.
 The sensed value is stored in an internal variable
in the node, called the sensed value (SV).

TEEN - Soft Threshold
43
 The nodes will next transmit data in the current
cluster period, only when both the following
conditions are true:
 The current value of the sensed attribute is greater
than the hard threshold.
 The current value of the sensed attribute differs
from SV by an amount equal to or greater than the
soft threshold.

TEEN
44
Good for time-critical applications 
If the thresholds are not reached, the user will
not get any data from the network at all and
will not come to know even if all the nodes die.

This scheme practical implementation would
have to ensure that there are no collisions in
the cluster. 

APTEEN (Adaptive Threshold sensitive
Energy Efficient Network protocol)
45
 APTEEN has been proposed just as an improvement
to TEEN in order to overcome its limitations and
shortcomings.
 APTEEN guarantees lower energy dissipation and a
helps in ensuring a larger number of sensors alive.
 Compared to LEACH, TEEN & APTEEN consumes
less energy (TEEN consumes the least)
 Network lifetime: TEEN ≥ APTEEN ≥ LEACH

46
Flooding
Gossiping
Flat-routing
Hierarchical-routing
Location-based routing

Location-based routing
47
 GEAR (Geographic and Energy Aware Routing)

Geographic and Energy Aware Routing
48
Geographic and Energy Aware Routing
 Routing based on a cost function depending on the
distance to the target and the remaining energy.
 A node N receive from a neighbor Ni its cost function
and then updates its own cost function:
H(N,T) = H( Ni , T) + C(N , Ni)
 If no cost function received from the node, then
compute a default cost function:C(N,T)= αd(N,T) + (1- α) Er

Geographic and Energy Aware
Routing
49
 Suppose α = 1
 S is sending a packet to T
 C is the closer neighbor to
T
 S receive new learned cost
function from C.
 Now, B’s cost function is
less than C
T
B C
S
S Sends the packet
through C
 Next packet will be sent
through B

Routing Protocols Based on Protocol
Operation
50
 Multipath Routing Protocols
 Query-Based Routing
 Negotiation-Based Routing Protocols
 QoS-based Routing
 Coherent and Noncoherent Processing

Multipath Routing Protocols
51
 Use multiple paths in order to enhance network
performance
Fault tolerance
Balance energy consumption
Energy-efficient
Reliability

Query-Based Routing
52
Destination nodes propagate a query for data
Usually theses queries are described in
natural language or high-level query language
E.g.
Directed diffusion
Rumor routing protocol

Negotiation-Based Routing Protocols
53
Use high-level data descriptors in order to
eliminate redundant data transmissions
through negotiation
Communication decisions are also made
based on the resources available to them
 E.g.
 SPIN

QoS-based Routing
54
 Has to balance between energy consumption and
data quality
 E.g.
 SPEED (congestion avoidance)

Conclusion
55
 based on the network structure divide three
categories: flat, hierarchical, and location-based
routing protocols.
 The advantages and disadvantages of each
routing technique
 In general hierarchical routing are outperform
than flat routing

reference
56
 I. Akyildiz et al., “A Survey on Sensor Networks,” IEEE Commun.
Mag., vol. 40, no. 8, Aug. 2002, pp. 102–14.
 W. Heinzelman, A. Chandrakasan and H. Balakrishnan,“Energy-
Efficient Communication Protocol for Wireless Microsensor
Networks,” Proc. 33rd Hawaii Int’l. Conf. Sys. Sci., Jan. 2000.
 F. Ye et al., “A Two-Tier Data Dissemination Model for Large-
Scale Wireless S. Hedetniemi and A. Liestman, “A Survey of
Gossiping and broadcasting in Communication Networks,” IEEE
Network, vol. 18, no. 4, 1988, pp. 319–49.

reference
57
 C. Intanagonwiwat, R. Govindan, and D. Estrin, “Directed
Diffusion: a Scalable and Robust Communication Paradigm
for Sensor Networks,” Proc. ACM Mobi- Com 2000, Boston,
MA, 2000, pp. 56–67.
 D. Braginsky and D. Estrin, “Rumor Routing Algorithm for
Sensor Networks,” Proc. 1st Wksp. Sensor Networks and
Apps., Atlanta, GA, Oct. 2002.
 C. Schurgers and M.B. Srivastava, “Energy Efficient Routing
in Wireless Sensor Networks,” MILCOM Proc. Commun. for
Network-Centric Ops.: Creating the Info. Force, McLean, VA,
2001.
 M. Chu, H. Haussecker, and F. Zhao, “Scalable Information
Driven Sensor Querying and Routing for Ad Hoc
Heterogeneous Sensor Networks,” Int’l. J. High Perf. Comp.
Apps., vol. 16, no. 3, Aug. 2002.

Routing

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