Basic Priority scheduling scheme

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Taha, M. H. N., Improving QoS of Data Transmission over Wireless Sensor Networks, , Cairo, Cairo University, 2013. Abstractmnasrtaha_phd_thesis

Wireless Sensor Networks (WSNs) consist of sensor nodes that are spatially distributed. These sensor nodes are connected to each other through wireless technology. They are an important emerging technology that will revolutionize sensing for a wide range of military, scientific, industrial and civilian applications. In many WSN applications, the sensor nodes are deployed in an ad hoc style without careful any pre-planning and engineering. Once deployed, the sensor nodes must have the ability to autonomously organize themselves into a wireless communication network.

New packet scheduling schemes have been developed for real-time data communication. These schemes work on prioritizing packets according to their deadlines. Packet prioritizing cannot support real time applications or assure network lifetime. In extreme traffic environments, large queues may lead to packet delay and packet dropping. Packet dropping leads to energy loss, as a packet could have consumed high energy in order to be delivered to its destination.

The continuous decrease in the size and cost of sensors has motivated intensive research addressing the potential of collaboration among sensors in data. Current research on routing and scheduling in wireless sensor networks focused on energy aware protocols to maximize the lifetime of the network. These researches are scalable to accommodate a large number of sensor nodes. In addition, they are tolerant to sensor damage and battery exhaustion. Sensor networks are deployed to gather information for later analysis, monitoring or tracking of phenomena in real-time.
In WSNs, transmitted packets are queued at intermediate nodes. Each node schedules the queued packets by assigning priorities to each packet. Priorities are assigned to packets according to their deadlines. This method in packet prioritization does not take into consideration either the network life time or energy consumption. Besides, it may lead to dropping high energy valuable packets. In many applications, WSN lifetime is considered a very critical issue, while setting up the network.

In this thesis, a new scheduling scheme, named Energy Based Scheduling scheme is introduced. In this scheme, packets are not only prioritized according to their deadlines but also according to some energy measures related to the network, that are obtained from the network nodes and are used in packet prioritization. The proposed scheme is integrated with the AODV routing protocol. The unused bits in the AODV packets are used by the proposed scheme in assigning sending priorities to each packet in the network. Through this thesis, the proposed scheduling scheme is compared with the Basic Priority Scheduling scheme, using NS-2. Comparisons are done according the network life time, energy consumption and the fairness index measure. The results prove that the Energy Based scheduling scheme increase the network life time and decrease the energy consumption for the goodput packets. On the other hand, the fairness index was affected.