Routing Protocols for Sensor Networks

1
Routing Protocols for Sensor Networks
An Application Specific Protocol Architecture for
Wireless Microsensor Networks by Anantha
Chandrakasan, Wendi Rabiner Heinzelman, and Hari
Balakrishnan
Presented by Reed Newman
2
Outline

• Introduction
• Background
• Architecture
• Operation
• Analysis and Simulation
• Results
• Comparisions
• Conclusion

3
Introduction

• Sensor Network Challenges
• Limited communication bandwidth
• Limited energy

• Parameters (Design goals)
• Ease of deployment
• System lifetime
• Latency
• Quality
• Neighboring nodes may have same data
• End user cares about a higher-level description
  of events

4
LEACH (Low-Energy Adaptive Clustering Hierarchy)

• Techniques (to achieve the design goals)
• Randomized, adaptive, self-configuring cluster
  formation.
• Localized control of data transfers
• Low energy media access control (MAC)
• Application specific data processing, such as
  data aggregation and compression.

5
Background

• Some application specific protocols developed for
  MSN
• Minimum Transmission Energy (MTE)
• For 3 nodes A, B and C, A would transmit to node
  C through B iff (ETX total transmit energy)
• ETX(ddAB) ETX(ddBC) lt ETX(ddAC)
• Only consider transmitter energy, neglects
  energy dissipation of the receivers
• Clustering
• Nodes send data to central cluster head
• Cluster head forwards data
• Cluster head has to be high energy node
• Fixed Infrastructure

6
LEACH Protocol Architecture

• Assumptions
• All nodes can transmit with enough power to reach
  the base station if needed
• Each node has computational power to support
  different MAC protocols
• Nodes always have data to send
• Nodes located to each other have correlated data

7
LEACH in brief

• All non-cluster head nodes transmit data to their
  cluster head
• Cluster head receives this data and performs
  signal processing functions on the data and
  transmits data to the remote BS
• Nodes organize themselves into local clusters,
  with one node as cluster head

8
Operation

• Divided into rounds
• Set-up phase
• Clusters are organized
• Steady phase
• Data transferred from nodes to cluster and on to
  BS

9
LEACH Step by Step

• Cluster Head Selection
• Each sensor elects itself to be cluster head at
  the beginning of a round
• Nodes that have not already been cluster heads
  recently, may become cluster heads
• Probability of becoming a cluster head is set as
  a function of nodes energy level relative to the
  aggregate energy remaining in the network
• Average energy of nodes in each cluster X Number
  of nodes in the network

10
LEACH Step by Step contd

• Cluster Formation
• Each cluster head node broadcasts an
  advertisement message (ADV) using CSMA MAC
  Protocol
• The message consists of the nodes ID and a
  header that distinguishes it as an ADV message
• Each non-cluster head node determines its
  cluster/cluster head that requires minimum
  communication energy
• Largest signal strength, minimum transmit energy
  for communication
• Each node transmits a join-request message (REQ)
  using CSMA MAC Protocol
• The message consists of nodes ID and cluster
  head ID
• Each cluster head node sets up a TDMA schedule
  and transmits it
• This ensures that there is no collision in data
  messages, radio components can be turned off at
  all times except during transmit time

Setup phase complete
11
Flowchart
12
LEACH step by step contd

• Steady State Phase
• Nodes send data during their allocated time slot

• Once the cluster head receives all data it
  performs data aggregation
• Resultant data is sent from cluster head to BS (a
  high energy transmission)
• Uses transmitter based code assignment to reduce
  inter-cluster interference
• Cluster head senses the channel before
  transmission

Steady phase complete
13
LEACH-CBS Cluster Formation

• Uses a central control algorithm to form clusters
• During setup phase each node sends its location
  and energy level to BS
• BS assigns cluster heads and clusters
• BS broadcasts this information

14
Analysis and Simulation

• Using ns
• Experiment setup
• 100-node network
• Nodes randomly distributed between (0,0) and
  (100,100)
• BS at location (50,175)
• Bandwidth of the channel 1Mbps
• Each data message 500 bytes long
• Packet header 25 bytes
• Simple radio model

15
ResultsLimited energy Simulations

• LEACH distributes more data per unit energy than
  MTE
• LEACH-C delivers 40 more data per unit energy
  than LEACH

16
Results contd

• LEACH can deliver 10 times the amount of
  effective data to BS as MTE for the same number
  of node deaths
• Benefits of rotating cluster heads is seen

17
Conclusions

• Advantages
• Outperforms conventional routing protocols
• LEACH is completely distributed, requiring no
  control information from the base station
• Nodes do not need global topology information
• Disadvantages
• Nodes must have data to send in the allotted time
• All nodes must be within range of the BS,
  limiting the scalability of the network
• Perfect correlation is assumed, which might not
  be true always

18
Comparisions
SPIN LEACH Directed Diffusion
Optimal Route No No Yes
Network Lifetime Good Very Good Good
Resource Awareness Yes Yes Yes
Use of Meta-data descriptors Yes No Yes
19
References

• An Application Specific Protocol Architecture for
  Wireless Microsensor Networks by Anantha
  Chandrakasan, Wendi Rabiner Heinzelman, and Hari
  Balakrishnan
• Energy-efficient Communication Protocol for
  Wireless Sensor Networks by Anantha Chandrakasan,
  Wendi Rabiner Heinzelman, and Hari Balakrishnan
  (IEEE Transactions on wireless communications,
  vol. 1, no. 4, Oct 2002)

20
Questions/Comments?
Thanks