Book Description

Sensor nodes are deployed over sensing fields for the purpose of monitoring certainphenomena of interest. The sensor nodes perform specific measurements, process thesensed data, and send the data to a base station over a wireless channel. The base stationcollects data from the sensor nodes, analyses this data, and reports it to the users. Wireless sensor networks are different from traditional networks, because of thefollowing constraints. Typically, a large number of sensor nodes need to be randomlydeployed and, in most cases, they are deployed in unreachable environments; however, the sensor nodes may fail, and they are subject to power constraints. Energy is one of the most important design constraints of wireless sensor networks. Energy consumption, in a sensor node, occurs due to many factors, such as: sensing theenvironment, transmitting and receiving data, processing data, and communicationoverheads. Since the sensor nodes behave as router nodes for data propagation, of theother sensor nodes to the base station, network connectivity decreases gradually. Thismay result in disconnected sub networks of sensor nodes. In order to prolong thenetwork?s lifetime, energy efficient protocols should be designed for the characteristicsof the wireless sensor network. Sensor nodes in different regions of the sensing field cancollaborate to aggregate the data that they gathered. Data aggregation is defined as the process of aggregating the data from sensor nodes toreduce redundant transmissions. It reduces a large amount of the data traffic on thenetwork, it requires less energy, and it avoids information overheads by not sending allof the unprocessed data throughout the sensor network. Grouping sensor nodes intoclusters is useful because it reduces the energy consumption. The clustering techniquecan be used to perform data aggregation. The clustering procedure involves the selectionof cluster heads in each of the cluster, in order to coordinate the member nodes. Thecluster head is responsible for: gathering the sensed data from its cluster?s nodes, aggregating the data, and then sending the aggregated data to the base station. An adaptive clustering protocol was introduced to select the heads in the wireless sensornetwork. The proposed clustering protocol will dynamically change the cluster heads toobtain the best possible performance, based on the remaining energy level of sensornodes and the average energy of clusters. The OMNET simulator will be used to presentthe design and implementation of the adaptive clustering protocol and then to evaluateit. This research has conducted extensive simulation experiments, in order to fully studyand analyse the proposed energy efficient clustering protocol. It is necessary for all ofthe sensor nodes to remain alive for as long as possible, since network quality decreasesas soon as a set of sensor nodes die. The goal of the energy efficient clustering protocolis to increase the lifetime and stability period of the sensor network. This research also introduces a new bidirectional data gathering protocol. This protocolaims to form a bidirectional ring structure among the sensor nodes, within the cluster, inorder to reduce the overall energy consumption and enhance the network?s lifetime. A bidirectional data gathering protocol uses a source node to transmit data to the basestation, via one or more multiple intermediate cluster heads. It sends data throughenergy efficient paths to ensure the total energy, needed to route the data, is kept to aminimum. Performance results reveal that the proposed protocol is better in terms of: itsnetwork lifetime, energy dissipation, and communication overheads.