LEACH & LEACH-C & V-LEACH

Overview Introduction Existing Protocols – Direct Transmission – Minimum Transmission Energy LEACH Stochastic Threshold Algorithm LEACH +/- Energy model LEACH-C Deterministic Threshold Algorithm Comparison (leach vs leach-c) V-LEACH Conclusions

Introduction LEACH (Low-Energy Adaptive Clustering Hierarchy) is a routing protocol for wireless sensor networks in which: – The base station (sink) is fixed – Sensor nodes are homogenous LEACH conserves energy through: – Aggregation – Adaptive Clustering

Existing Routing Protocols LEACH is compared against three other routing protocols: – Direct-Transmission Single-hop – Minimum-Transmission Energy Multi-hop – Static Clustering Multi-hop

 Direct-Transmission Each sensor node (CH) transmits directly to the sink, regardless of distance Most efficient when there is a small coverage area (small network) and/or high receive cost?

 Minimum Transmission Energy (MTE) Traffic is routed through intermediate nodes – Node chosen by transmit amplifier cost – Receive cost often ignored Most efficient when the average transmission distance is large and E elec is low

Energy Analysis of DT and MTE direct communication energy equations MTE communication energy equation Simple linear network model

Performance: System Lifetime Setup costs ignored !! 0.5J of energy/node LEACH more than doubles network lifetime

Performance: Coverage LEACH – Energy distributed evenly – All nodes serve as cluster heads eventually – Deaths randomly distributed MTE – Nodes near the sink die first Direct Transmission – Nodes on the edge die first

LEACH: Operation The LEACH network has two phases: the set- up phase and the steady-state – The Set-Up Phase Where cluster-heads are chosen – The Steady-State The cluster-head is maintained When data is transmitted between nodes

Stochastic Threshold Algorithm  Cluster-heads can be chosen stochastically (randomly based) on this algorithm:  If random < T(n), then that node becomes a cluster-head  The algorithm is designed so that each node becomes a cluster-head at least once

LEACH + / - Advantages Any node that served as a CH in certain round cannot be selected as the CH again Because of TDMA schedule it prevents CHs from unnecessary collisions Data aggregation at cluster head Cluster head communicate directly with sink Disadvantages Clusters and CHs formation is in each round ! Not applicable to large-region networks No real load balancing because CHs are elected in terms of probabilities without energy considerations dynamic clustering brings extra overhead

LEACH-C LEACH offers no guarantee about the placement and/or number of cluster heads. LEACH-C, uses a centralized clustering algorithm and the same steady-state phase as LEACH. LEACH-C protocol can produce better performance by dispersing the cluster heads throughout the network. During the set-up phase, each node sends information about its current location (possibly determined using GPS) and

LEACH-C Once the cluster heads and associated clusters are found, the sink broadcasts a message that obtains the cluster head ID for each node. If a cluster head ID matches its own ID, the node is a cluster head; otherwise the node determines its TDMA slot for data transmission and goes sleep until its time to transmit data

Deterministic Threshold Algorithm LEACH-C takes into account the amount of energy in the node …and/or whether or not the node was recently a cluster-head

What’s the Difference? The goal of these protocol is to increase the life of the network The changes between the LEACH stochastic algorithm and the LEACH-C deterministic algorithm alone is proven to increase the FND (First Node Dies) lifetime by 30% and the HND (Half Node Dies) lifetime by 20%. The overall performance of LEACH-C is better than LEACH by dispersing the cluster heads throughout the network

An Example of a LEACH Network While neither of these diagrams is the optimum scenario, the second is better because the cluster- heads are spaced out and the network is more properly sectioned

V-LEACH The cluster contains: CH (responsible only for sending data that is received from the cluster members to the BS), vice-CH (the node that will become a CH of the cluster in case of CH dies), cluster nodes (gathering data from environment and send it to the CH).

V-LEACH In the original LEACH, the CH is always on receiving data from cluster members, aggregate these data and then send it to the BS that might be located far away from it. The CH will die earlier than the other nodes in the cluster because of its operation of receiving, sending and overhearing. When the CH die, the cluster will become useless because the data gathered by cluster nodes will never reach the base station. In our V-LEACH protocol, besides having a CH in the cluster, there is a vice-CH that takes the role of the CH when the CH dies because the reasons we mentioned above.

V-LEACH

Conclusions