Browsing by Author "Shabani, Hikma"

Smart distribution grid involves overlaying real-time wireless communication technologies from advanced metering infrastructure (AMI) gateways at the consumer premises to the distribution points with a built up of beacon mode wireless sensor multi-hop mesh network for large coverage data exchanges. Zigbee/IEEE802.15.4 is one of the prominent standards for Wireless Sensor Networks (WSNs) due to its low bandwidth requirements, low cost of deployment, easy network implementation and low-power embedded systems. However, IEEE802.15.4 standard does not specify any mechanism to enable beacon mode for multi-hop mesh networks. Furthermore, with the usage of IEEE802.15.4 guaranteed time slot (GTS), the real-time data is sent at the end of the super_frame after experiencing a slotted Carrier Sensor Multiple Access with Collision Avoidance (CSMA-CA) which may not ensure an immediate access to medium. Despite a reserved GTS, a node contends for channel access during Contention Access Period (CAP) which decreases the network performance. Finally, the scheduling of Contention Free Period (CFP) at the end of the active portion of the super_frame gives the normal data a faster channel access than the real-time data which may wait until the end of the CAP to get a deterministic channel access. Therefore, this thesis modifies IEEE802.15.4 MAC architecture by swapping the CAP with the CFP to improve the channel access time and the Reserved Broadcast Duration Slot (RBDS) is placed at the beginning of the CFP for critical real-time data delivery. All simulations are conducted on Network Simulator version 2 (NS-2) while for network analytical examinations, a 2*D Markov_Chain model is developed from the Modified IEEE802.15.4 MAC protocol. For the sake of energy efficiency no acknowledgement (ACK) is implemented and the routing protocol is not used since this approach is evaluated without the influence of the network layer. With its scalability up to 51 nodes and compared to IEEE802.15.4 MAC standard, the new model improves the network performance such as time_delivery_delay, reliability, goodput, power consumption and throughput as well as SCADA round_trip_time transactions.

Maxwell’s equations are implemented using Finite Difference Time Domain (FDTD) method to investigate the radiation effects in human body. Flat Phantom Model for human body is proposed using incident electric fields and Perfect Matched Layers (PML) boundary conditions. The proposed model has been implemented in Matlab Codes. The electric field distribution and Specific Absorption Rate (SAR) are calculated for all possible human organs using the measured electric field intensity at 900MHz, 1800MHz and 2.4GHz at International Islamic University Malaysia (IIUM), Gombak Campus. The values predicted by proposed method are found close to those calculated by the commercial Remcom Inc Software, XFDTD6.4. The effect of SAR has been predicted for different organs using proposed model. It is observed that the effect is higher in higher frequencies and the organ affects worse is brain. The SAR predicted by the proposed model for measured radiated fields at aforementioned frequencies are compared with safety guidelines given by the recognized body such as ANSI/IEEE, ICNIRP and Malaysia Communication and Multimedia Commission (MCMC).The predicted SAR is found 0.083W/Kg at 900MHz, 0.751W/Kg at 1800MHz and 1.434W/Kg at 2.4GHz which are 4.2%, 37.6% and 71.7% respectively of safety limits proposed by ICNIRP. The preliminary results show that the campus is safer for its inhabitants.