Routing Protocols for Sensor Networks Presented by Siva Desaraju Computer Science WMU An Application Specific Protocol Architecture for Wireless Microsensor Networks by Anantha Chandrakasan, Wendi Rabiner Heinzelman, and Hari Balakrishnan

 LEACH

Outline   Introduction   Background   Architecture   Operation   Analysis and Simulation   Results   Comparisions   Conclusion

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

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.

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(d=dAB) + ETX(d=dBC) < ETX(d=dAC) – 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

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

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

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

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

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 node’s 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

Flowchart

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

LEACH-C:BS 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

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

Results:Limited energy Simulations  LEACH distributes more data per unit energy than MTE  LEACH-C delivers 40% more data per unit energy than LEACH

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

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 – –Perfect correlation is assumed, which might not be true always

Comparisions SPINLEACH Directed Diffusion Optimal Route No Yes Network Lifetime GoodVery GoodGood Resource Awareness Yes Use of Meta-data descriptors YesNoYes

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)

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