COMSATS Institute of Information Technology, Islamabad
Tuesday, February 07, 2012
Wireless Sensor Network Group
Wireless sensor network (WSN) Lab at CAST pursues research and development on system level aspects, focusing on the communication and communication principles of WSN. The main motivation is to address the following problems: how to efficiently form a communication network starting from scratch and then maintain that network under different scenarios especially in the presence of jamming and interference.

Currently the focus is on the MAC layer in WSN.In MAC layer the investigated topics are synchronization, frequency hopping (slow and fast) and co-existence.

There are many applications which require time synchronization for them to work correctly such as frequency hopping, localization of sensor nodes, coordination of senor nodes within a network, temporal message ordering, time division multiple access and the energy efficient operation of the network by scheduling the sleep time and wake time of the sensor nodes.

Frequency hopping is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. Frequency hopping is highly resistant to interference, jamming and frequency-selective fading. Advanced form of frequency hopping called dynamic frequency hopping will be studied as a basis of cognitive radio based WSN.

Co- existence tools are already part of IEEE 802.15.4, such as: clear channel assessment (CCA) for carrier sense multiple access with collision avoidance (CSMA-CA), dynamic channel selection, modulation, energy detection (ED) and link quality indication (LQI), low duty cycle, low transmit power, channel alignment and neighbor piconet capability.We are incorporating these methods to formulate energy efficient co-existence mechanisms.
Fault-Resilient Pseudo-Parenting Protocol for Energy Aware Hierarchical Data Aggregation in Wireless Sensor Networks
In sensor networks, communication cost is often several orders of magnitude higher than computation cost. Data generated from neighboring sensors is often redundant and highly correlated. In addition, the amount of data generated in large sensor networks is usually enormous for base stations to process. Hence, data aggregation is used which combine data into high-quality information at intermediate nodes. They can reduce the number of packets transmitted to the base stations which results in conservation of energy and bandwidth. Sensor networks are also subject to high failure rate: connectivity between nodes can be lost due to environmental noise and obstacles; nodes may die due to battery depletion, environmental changes or malicious destruction. In such environments, reliable and energy efficient data delivery is crucial because sensor nodes operate with limited battery power and error-prone wireless channels. In data aggregation protocols, reliable delivery is very necessary because when an aggregation node fails, all of the data below the tree will be lost. This motivates us to study how sinks will receive aggregated data reliably and how reliability and aggregation affect each other.

In previous approaches there is no local repair mechanism to handle network changes (due to link failure, node failure) and link recovery is so slow that it is hard to meet the requirement for time-sensitive traffic because nodes have to wait for the next interest propagation round.

Hierarchical Data Aggregation (HDA) is energy efficient but prone to node failure especially when it occurs in highly data aggregated node. We address this issue by extending hierarchical data aggregation (HDA) scheme. The proposed pseudo parenting methodology constructs a hierarchical structure in which every node has multiple parent nodes for data forwarding. The main idea behind our scheme is to approach healthy parent and find the alternate path when failure is detected i.e. if forwarding node fails, another node among parents is selected for data forwarding. Scheme is tested for significant power saving because power is not wasted in retransmitting to failed node and hop by hop data delivery is ensured.

Results are exposed for diverse environment parameter for example failure of high aggregation efficient node which essentially leads to increase in data transmissions and hence longer route path. Effects of failure on data aggregation are minimized by allowing aggregation performed at higher levels of hierarchy. To aid our study, the proposed protocol is tested for delivery ratio, node failure ratio, energy consumption, and network volume; that eventually measure the effectiveness and energy efficiency of our algorithm.

Simulation results show that our protocol achieves higher data delivery ratio while consuming less energy than conventional HDA.
Members
  1. Ms. Amna Irum
  2. Mr. Umer Javed
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