ROUTING TECHNIQUES IN

thoughtlessskytopNetworking and Communications

Oct 29, 2013 (3 years and 9 months ago)

69 views

ROUTING TECHNIQUES IN
WIRELESS SENSOR
NETWORKS: A SURVEY



Outline


Background


Classification of Routing Protocols


Data Centric Protocols


Flooding and Gossiping


SPIN


Directed Diffusion


Rumor Routing

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 processing

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
.


Routing Protocols

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 Routing

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 same

Flooding &
Gossiping(cont.)


Pros


Simple


No
routing, no state maintenance


Cons


Implosion


Overlap



Resource blindness


Delay
in Gossiping

SPIN


Sensor Protocols for

Information via Negotiation


Metadata negotiation done before transmitting the
actual data.


3
-
way handshake: ADV, REQ, DATA


Event
-
driven


SPIN(cont.)


Pros


Solve
the classic problems


Topological
changes are localized



Cons


No
guarantee on the delivery of data

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
-
driven


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 queries

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 nodes

Rumor Routing (
cont
)


Pros


Avoid
query flooding


Cons


Performs
well only when # of events is small


Overhead
to maintain agents and event
-
tables

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
performance

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 nodes



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.


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)


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.


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...


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?

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).

Passing the buck...


Token

passing approach


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.


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.


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)
.


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
.


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.


GPSR: GREEDY PERIMETER
STATELESS ROUTING FOR WIRELESS

NETWORKS

Presentation Overview


Introduction


Algorithm Key Ideas & Concepts


Examples


Evaluation Matrices & Results


Summary


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 changes



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,”


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 hop


Greedy Forwarding Example

Follows successive closer geographic hops, until the
destination is reached

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 situation

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 D

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 thereafter

Network Graphs

Full Graph

Greedy Forwarding

Planar Graph

Perimeter Forwarding

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.

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 decisions

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.

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 packet

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
packets

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
DSR

Pause 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.

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
overhead

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 DSR

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

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 routing





Thank you