Spin protocols ppt

Seminar Topic :

SPIN - Protocols for Wireless Sensor Networks

Motivation

• Dissemination is the process of distributing individual sensor observations to the whole network, treating all sensors as sink nodes

• Limited supply of energy

• Limited computational power

• Limited communication resources

Motivation-Classic Flooding

• Classic approach for dissemination• Source node sends data to all neighbors• Receiving node stores and sends data to all its

neighbors• Requires no protocol state• Disseminates data quickly• Deficiencies

– Implosion– Overlap– Resource blindness

Motivation – Classic Flooding • Implosion

– Always sends data to a neighbor, even it has already received the data from another node

– Function of topology

• Overlap– Nodes often cover overlapping

areas (e.g. temperature distr.)– Function of topology and

mapping of observed data

• Resource blindness– Amount of energy available

does not affect the communication activities

B C

D

Aa a

a a

A

B

C

r

s

q

q

Concept - Idea

• SPIN = Sensor Protocols for Information via Negotiation

• Negotiation-Before transmitting data, nodes negotiate with each other to overcome implosion and overlap

• Resource adaptation-Each sensor node has resource manager

• SPIN efficiently disseminates information among sensors in an energy-constrained wireless sensor network.

Concept - Assumptions

• Sensor applications need to communicate about data they have and data they need to obtain– Exchanging sensor data is expensive, whereas

exchanging meta-data is not

• Nodes must monitor and adapt to changes in their energy resources– Extend lifetime of the system

Architecture – Meta-Data

• Completely describe the data– Must be smaller than the actual data for SPIN to be

beneficial– If you need to distinguish pieces of data, their meta-

data should differ

• Meta-Data is application specific– Sensors may use their geographic location or unique

node ID– Camera sensor may use coordinate and orientation

• Application must be able to interpret and synthesize its own meta-data

Architecture – Messages

• ADV – data advertisement– Node that has data to share can advertise this by

transmitting an ADV with meta-data attached

• REQ – request for data– Node sends a request when it wishes to receive some

actual data

• DATA – data message– Contains actual sensor data with a meta-data header– Usually much bigger than ADV or REQ messages

SPIN-1 – Example

Has Data to

disseminate

SPIN-1 – Example - Advertise Stage

ADV

ADV

ADV

ADV

SPIN-1 – Example - Request Stage

REQ

REQ

REQ

REQ

SPIN-1 – Example - DATA Stage

DATA

DATA

DATA

DATA

SPIN-1 – a 3-Stage Handshake Protocol

• Needs knowledge about single-hop network neighbors

• Adaptation for lost networks– Compensate lost ADV messages by re-advertising

periodically– Compensate lost REQ/DATA by re-requesting after

fixed time• Adaptation for mobile networks

– Topology changes trigger updates to neighbor lists of nodes

– When a nodes neighbor list changed, re-advertise all its data

SPIN-2 – Energy-conservation• Adds simple energy-conservation heuristic to SPIN-1

• Incorporate low-energy-threshold

• Works as SPIN-1 when energy level is high

• Reduce participation of node when approaching low-energy-threshold

– When node receives data, it only initiates protocol if it can participate in all three stages with all neighbor nodes

– When node receives advertisement, it does not request the data

• Node still exhausts energy below threshold by receiving ADV or REQ messages

Implementation

Simulation• no physical implementation but

simulation with network simulator ns-2 – event-driven network simulator– extensive support for

simulation of: TCP, routing, multicast protocols

– functionality of ns was extended to implement SPIN family, node class extended to create a Resource-Adaptive Node, components

Implementation

Simulation test bed• 25-node wireless test network, fully

connected graph• edges signify communicating

neighbors

Evaluation

Other dissemination algorithms for comparison:

• Classic Flooding (explained on former slides)

• Gossiping

• Ideal dissemination

Evaluation

Gossiping• alternative to classic flooding,

use randomization to conserve energy

• only forward to one randomly selected neighbor, not to all

• no implosion: only one copy of the data travels the network

• slow distribution of data, slow dissipation of energy

• resume: avoids implosion, but overlap problem still exists

A B D

C

1 2

3

4

Evaluation

Ideal Dissemination

• explanation by an example: distribution in 2 steps

– ideal dissemination of observed data a and b

– B and C have common neighbor D, but no implosion

– A and C have overlapping initial data item c, but no overlapping problem

• simulate result of an ideal dissemination using a modified SPIN-1

– eliminate time and energy costs for ADV and REQ messages

– series of DATA messages in the network = ideal dissemination

A(a, c)

B C(c)

D

1: (a, c) 1: (a)

1: (c)2: (a)

Evaluation

Simulations• unlimited energy simulation

– data acquired over time– energy dissipated over time

• limited energy simulation (1.6 Joules total energy in the network)– data acquired over time– energy dissipated over time

• for unlimited energy scenario: SPIN-1 = SPIN-2, compared with flooding, gossiping and the ideal data distribution protocol

Simulation: unlimited energy• message profiles for the simulations

• only SPIN-1 uses meta-data

• SPIN-1 does not send any redundant data message

• average energy dissipated for each node depending on its degree

• high degree node

– lie upon a critical path in the network

– may die out before other nodes and partition the network

Simulation: unlimited energy

Simulation: limited energy• total energy in the system: 1.6 Joule

• flooding exhausts energy quickly

• if energy is very limited, gossiping can accomplish the most data distribution

• SPIN-2 distribute 10% more data than SPIN-1

Conclusion• SPIN is family of data dissemination protocols

• meta-data negotiation and resource adaptation– only transmit data when necessary, never waste energy on useless transmissions– when energy is low: node cuts back its activities

• solved implosion and overlap problem

• only local neighborhood information, thus well suited for mobile sensors

• time performance: comparable to classic flooding

• energy performance: 25% energy of classic flooding, SPIN-2 distributes 60% more data per unit energy than flooding

• gossiping outperformed in both disciplines

• close to ideal dissemination

References

(1) Heinzelmann, W. R.; Kulik, J.; and Balakrishnan, H.Adaptive Protocols for Information Dissemination in Wireless Sensor Networks. In Fifth ACM/IEEE MOBICOM Conference (August 1999).

(2) ns-2 Network Simulator, http://www.isi.edu/nsnam/ns/