Outline Background Classification of Routing Protocols Data Centric Protocols Flooding and Gossiping SPIN Directed Diffusion Rumor Routing Background Sensor nodes Small wireless battery ID: 297669
Download Presentation The PPT/PDF document "Routing Techniques in Wireless Sensor Ne..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Routing Techniques in Wireless Sensor Networks: A Survey
Slide2
Outline
Background
Classification of Routing Protocols
Data Centric Protocols
Flooding and Gossiping
SPIN
Directed Diffusion
Rumor RoutingSlide3
Background
Sensor
nodes
Small
, wireless, battery
powered
Energy
, bandwidth constrained
Data
sensing, relaying,
aggregating
No
global addressing scheme
Sink nodes
More
powerful nodes
Usually
gateway to wired networks
Data
collecting and processingSlide4
Goal
So at network layer, it is highly desirable to find methods for energy efficient route discovery and relaying of data from the sensor nodes to the BS so that the life time of the network is
maximized.Slide5
Routing ProtocolsSlide6
Data-centric Protocols
The ability to query a set of sensor nodes
Attribute-based
naming
Data
aggregation during relaying
For
example:
Flooding
& Gossiping
SPIN
Directed
Diffusion
Rumor RoutingSlide7
Flooding & Gossiping
In flooding, sensor broadcasts packets to all
its neighbors
till
dst
reached or packets'
ttl
== 0
In gossiping, sensor sends packets to
a randomly
selected neighbor which does
the sameSlide8
Flooding & Gossiping(cont.)
Pros
Simple
No
routing, no state maintenance
Cons
Implosion
Overlap
Resource blindness
Delay
in GossipingSlide9
SPIN – Sensor Protocols forInformation via Negotiation
Metadata negotiation done before transmitting the actual data.
3-way handshake: ADV, REQ, DATA
Event-drivenSlide10
SPIN(cont.)
Pros
Solve
the classic problems
Topological
changes are localized
Cons
No
guarantee on the delivery of dataSlide11
Directed Diffusion
Sink node floods named “interest” with
larger update
interval
Sensor
node sends back data via “gradients”
Sink
node then sends the same “interest”
with smaller
update interval
Query-drivenSlide12
Directed Diffusion (cont)
Pros
On
demand route setup
Each
node does aggregation and caching,
thus good
energy efficiency and low delay
Cons
Query-driven
, not a good choice for
continuous data
delivery
Extra
overhead for data matching and queriesSlide13
Rumor Routing
A trade-off between Query & Event flooding
An
agent, a long-lived packet, is
generated when
events happen
The
agent propagate the event to distant nodesSlide14
Rumor Routing (cont)
Pros
Avoid
query flooding
Cons
Performs
well only when # of events is small
Overhead
to maintain agents and event-tablesSlide15
Hierarchical Routing Protocols
When sensor density increases single tier networks cause
Gateway overloading
Increased latency
Large energy consumption
Clustered Network allow coverage of large area of interest and additional load without degrading the performanceSlide16
Hierarchical Routing Protocols
Idea
Partition the entire network into regions or clusters.
Select one or more nodes as the cluster head.
The routing is nodes -> cluster head A -> cluster head B -> cluster head C -> nodes
The routing between cluster heads and the routing within a cluster may follow different protocols (EGP-BGP and IGP-OSPF).
Issues resolved: Energy wasted in collision, collision avoidance, idle-listening
Achieves
Better scalability
Removes the load to less powerful nodesSlide17
The LEACH Protocol
L
ow-
E
nergy
A
daptive
C
lustering
H
ierarchy.
Distributed cluster formation technique that enables
self-organization
of large numbers of nodes.Slide18
LEACH - Setup
Set up phase
Cluster Head (CH) selection (random + rotating)
ADV
Join REQ
TDMA SCH prepared by CH (no collisions and reduced energy consumption)Slide19
LEACH - Steady State
Broken into frames, where nodes send their data to the cluster head at most once per frame during their allocated transmission slot.
Once the cluster head receives all the data, it performs data aggregation.Slide20
PEGASIS
P
ower-
E
fficient
GA
thering in
S
ensor
I
nformation
S
ystems.
The key idea in PEGASIS is to form a
chain
among the sensor nodes so that each node will
receive from and transmit to a close neighbor
.
Well, what was so bad in LEACH except for a bad name...Slide21
PEGASIS - Concept
Be
Greedy
!
Align with the one that has the max signal strength, form a near-optimal chain.
Communicate with
neighbors
only
.
But who takes care of communicating to BS?Slide22
PEGASIS - Leader
The main idea in PEGASIS is for each node to receive from and transmit to close neighbors and take turns being
the leader for transmission to the BS
.
Nodes take turns transmitting to the BS (
i
mod N
node in round
i
out of N nodes shall transmit to BS).Slide23
Passing the buck...
Token
passing approachSlide24
The TEEN Protocol
T
hreshold sensitive
E
nergy
E
fficient sensor
N
etwork 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.Slide25
TEEN - Functioning
At every cluster change time, the cluster-head broadcasts 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.Slide26
TEEN - Hard Threshold
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)
.Slide27
TEEN - Soft Threshold
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
.Slide28
TEEN - Drawback
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
-
A
daptive
P
eriodic TEEN
This scheme practical implementation would have to ensure that there are no
collisions
in the cluster.Slide29
GPSR: Greedy Perimeter Stateless Routing for Wireless
NetworksSlide30
Presentation Overview
Introduction
Algorithm Key Ideas & Concepts
Examples
Evaluation
Matrices &
Results
Summary Slide31
GPSR Overview
Routing Protocol that
uses positions
of routers and a packet’s destination to make packet forwarding decisions
GPSR keeps state only about the local
topology (for only a single hop)
The word “
Stateless
” is not meant literally but refers to small, purely local state
GPSR
scales better
in per-router state than shortest-path and ad-hoc routing protocols
GPSR
finds correct new route quickly
under frequent topology changesSlide32
Algorithm’s Key Ideas
“The position of a packet’s destination and positions of the candidate next hops are sufficient to make correct forwarding decisions, without any other topological information.”
“Routing protocol that rely on end-to-end state concerning the path, face scaling challenge with increasing
number of
routers & rate of change of topology (mobility).”
“GPSR
generates routing protocol traffic independent of the length of the routes through the network, therefore generates a constant, low volume protocol messages as mobility
increases,”Slide33
GPSR Modes
Modes
Nominal:
Greedy
Forwarding
Special :
Perimeter Forwarding
Greedy
Forwarding
Uses only information about router’s immediate
neighbors
Forwarding node makes
locally optimal greedy choice
of the packet’s next hopSlide34
Greedy Forwarding Example
Follows successive closer geographic hops, until the destination is reached Slide35
Perimeter Forwarding
Used in the region where Greedy forwarding fails.
There are topologies in which the only route to a destination requires a packet move
temporarily farther
in geometric distance from the destination
Special mechanism (right hand rule) is used in such special situationSlide36
Perimeter Forwarding Example
Right Hand Rule
: x receives a packet from y, and forwards it to its first neighbor counterclockwise about itself , z
When Greedy Forwarding Fails.
x is a local maximum in geographic proximity to D
w and y are farther from DSlide37
Perimeter Forwarding Example
D is the destination
; x
is the node where the packet enters perimeter mode; forwarding hops are solid arrows; the line
xD
is dashed.
GPSR forwards packets along the face intersected by the line
xD
x
forwards the packet to the first edge counterclockwise about x form the line
xD
, follows right hand rule thereafterSlide38
Network Graphs
Full Graph
Greedy Forwarding
Planar Graph
Perimeter Forwarding Slide39
Planarized Graphs
The RNG graph.
For
edge(u; v) to be included,
the shaded
lune
must contain no witness w.
The GG graph.
For
edge(u; v) to be included,
the shaded
circle must contain no witness w.Slide40
GPSR Operation
GPSR combines greedy forwarding on full network graph and perimeter forwarding in
planarized
network graphs
All nodes maintain neighbor table, which stores the address and location of their single-hop radio neighbors
The table provides all states required for forwarding decisionsSlide41
GPSR Operation
All packets are marked initially as greedy mode
Upon receiving a greedy-mode packet, a node searches its neighbor table geographically closest to the packet’s destination.
If the neighbor is closer to the destination, it forwards the packet to the neighbor.
If no neighbor is closer, the packet is marked into perimeter mode.Slide42
GPSR Operation
In perimeter mode, the packet is forwarded using a simple planner graph
The packet is forwarded to progressively closer faces of the planner graph using the right hand rule
In perimeter node, the GPSR records the location where greedy failed, and the first edge a packet crosses on a new face
When the destination is not reachable, the packet will tour unsuccessfully around the entire face as no intersection with
xD
is detected
Upon traversing on the face second time, the repetition is detected to correctly drop the packetSlide43
Algorithm Evaluation Matrices
Packet
delivery success
rate
Fraction of applications’ packets delivered successfully by the routing algorithm
R
outing
protocol
overhead
Per-node state: storage required at each node
Protocol message cost: number of protocol packets sent by the routing algorithm
O
ptimality
of
path lengths
taken by data
packetsSlide44
Packet Delivery Success Rate
GPSR
with
varying
beacon
intervals
, B,
compared
with
Dynamic
Source
Routing (DSR). 50 nodes
GPSR delivers a slightly greater fraction of packets successfully than DSRPause time
is the time duration for which all nodes hold the same positions at waypoints. The mobility model used is the random way point model which generates waypoints at random. Slide45
Routing Protocol Overhead
Total routing
protocol
packets sent network-wide during the simulation for
GP
R
with varying
beacon intervals, B, compared
with
DSR. 50
nodes
.
GPSR offers greater savings in routing protocol overheadSlide46
Packet Delivery Success Rate
Packet Delivery
Success Ra t e . F o r G P S R
with
B =
1.5 compared with
DSR. 50, 112, a n d 200 node s .
GPSR delivers 97% of its packets along optimal-length paths vs. 84.9% for DSRSlide47
Routing Protocol Overhead
Total routing
protocol
packets sent network-wide during the simulation for GPSR
with
B = 1.5 compared with DSR. y axis log-scaled. 50, 112,
and
200 nodes.
GPSR generates drastically less routing protocol traffic
w.r.t
. to DSR Slide48
Summary
GPSR routing algorithm uses geography to achieve small per-node route state, small routing protocol message complexity, and extremely robust packet delivery
GPSR generates routing protocol traffic independent of the length of the routes through the network, therefore generates a constant, low volume protocol messages as mobility increases
GPSR performs better than
DSR. GPSR keeps states proportional to no. of neighbors; DSR keeps sates proportional to product of no of routes learned and route length in hops.
Besides Hierarchy and Caching, Geography is leverages for scaling routingSlide49
Thank you