Publications

Sensor networks have been used in various application areas (e.g., health, military, home). Sensing, data processing, and communicating are the main components of a typical sensor node that enable it to stay alive and function properly. This node is made up of four base components: a sensing unit, a processing unit, a transceiver unit, and most important of all a power unit. Additional components may be added like GPS, mobilizer, and power generator. The signal processing and transmitting activities are the main consumers of sensor's energy. Since the main power of a node is its battery, keeping the sensor in continues action will limit the battery’s lifetime leading to a quick node failure. Therefore, to get the best behavior out of a sensor node and keep the network functioning as long as possible is a crucial concern. In addition to efficient energy usage, a node must be able to accomplish its desired mission in an acceptable data quality. For this concern routing protocols have been an important field of study. Several routing protocols have been proposed depending on many factors including network structure, protocol operation, and path establishment all aiming to minimize the allover energy consumption of a sensor network. These factors are based on several limitations facing wireless sensor such as Energy Consumption, Scalability, Reliability, Adaptability, Fault tolerance, Connectivity, Network costs, Data aggregation, Quality of service, Mobility, Node deployment, Environmental conditions, Hardware constrains, Transmission media, Network topology, and Security. Moreover, we are going to classify the network protocols according to the network structure and operation. Routing protocols can be classified by three different ways either network structure, protocol operation, or path establishment. A. Network Structure Routing protocols can be categorized into 3 different protocols according to the network structure: flat, hierarchical, and location based. 1) Flat based routing Flat routing is a multi-hop routing where all nodes operate at the same time. Since the network is usually large all nodes are to be assigned the same sensing task. Therefore, since all nodes transmit data, redundancy is likely to occur, which leads to high energy consumption. 2) Hierarchical based routing Nodes are unable to communicate to a very large distance. Therefore cluster based, hierarchical routing becomes a good solution. In this routing scheme different clusters are created and cluster-heads are assigned. The importance of this routing protocol is implemented data aggregation causing decreasing energy consumption, where the packets are sent to the sink. 3) Location based routing protocols Here the location of nodes is known through a low power GPS on every node. So nodes are addresses by their location. Therefore, not all nodes are demanded to work together, some may go to sleep saving energy while others sense events. The distance between the nodes can be detected by the strength of the signal received from those nodes. B. Protocol Operations The function of a wireless sensor network specifies its application. Therefore, routing protocols can be categorized according to the operation used to satisfy a WSN function. 1) Multipath based 2) Query based 3) Negotiation 4) Qos (Quality of service) 5) Coherent and Noncoherent C. Path establishment Routing protocols can be also classified into three categories: proactive, reactive, and hybrid depending on how the source discovers a route to the destination. LEACH LEACH is a hierarchical protocol. The network is divided into cluster heads (CH), which act as a coordinator, and cluster members. Cluster head role rotates randomly between nodes where every node gets to be a cluster head at some point. After the CH receives data from its cluster members, it aggregates it and sends the aggregated data to the sink minimizing energy consumption. LEACH is separated into two phases:  Setup phase: some nodes are elected CH for the round, based on a certain formula.  Steady state phase: the sensor nodes start sensing data and forwarding it to the CH in its cluster When this round ends after a certain period of time and the next round starts, all nodes return to setup phase choosing new cluster head and so on. We used matlab to examine the behavior of LEACH protocol at each round. Starting with 100 nodes, we first pointed the round where the first node is dead reaching approximately round 2300, where all nodes are dead. We also showed the total number of packets send by all the nodes at each round. Moreover, we showed how the total energy of the whole network which started as 50J (0.5J per node) is decreasing at each round reaching zero after the death of all nodes.