7 research outputs found
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Interference Time Analysis for a Cognitive Radio on an Unmanned Aircraft
This thesis considers a model consisting of a cognitive radio (CR) on an unmanned aircraft (UA) and a network of licensed primary users on the ground. The cognitive radio uses the same frequency spectrum as the primary users for its operation and hence acts as an interferer. This work analyzes the duration of interference in such a model. It defines two important metrics -- the interference radius and the detection radius. The interference radius determines the boundary of the area within which a primary user might be subjected to harmful interference due to the operation of the CR. The detection radius determines the boundary of the area within which the presence of a primary user might be detected by the CR. The interference and detection radii might vary due to the dynamic nature of the radio environment. This thesis derives the dependence of these metrics on the radio propagation parameters like antenna gain, antenna height, path-loss exponents, etc. It uses these metrics and characterizes the model using an M/G/infinity queue to determine the statistics of the interference time for the entire excursion of the unmanned aircraft. The key statistics determined are the distribution of the duration of interference periods, the mean and the total interference time. Firstly, this work analyzes a 1D system model where the primary users are distributed randomly along a straight line. The results are then extended to a 2D system where the primary users are distributed randomly over an area. The analysis is carried out for both sparsely-dense and highly-dense primary user ground network. This work gives a new dimension to analyze the effects of interference in terms of duration of interference. It also shows how these interference effects can be minimized on enhancing the detection capability of the cognitive radio. The results from this work can be used to determine the optimum setting for the cognitive radio system such that it restrains the duration of interference below tolerable limits
Performance Analysis of a Wireless Backhaul in a Three-Tier Hybrid Network with Directional Antennas
Enhancements to the long term evolution (LTE) standard for facilitating the Internet of things (IoT)
The world is evolving towards an Internet of Things (IoT) where a large number of devices interact to realize different applications that constitute smart electricity grids, intelligent transportation systems, ubiquitous healthcare solutions, etc. Machine Type Communications (MTC) provide the substrate for the connectivity and service mechanisms of these devices. Many services associated with the MTC applications such as smart metering and location tracking require the cellular network as the backbone for communication and are instrumental in driving the growth of the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) / LTE-Advanced (LTE-A) standards. A substantial number of MTC User Equipment (UE) hosting IoT applications are expected to be low cost, low data rate devices requiring prolonged battery life. In the downlink, the current LTE/LTE-A standards adopt Discontinuous Reception (DRX) mechanism for power reduction, which requires the UE to wake up periodically to check for a paging message from the base station. The LTE/LTEA standardization activities have identified that intricate paging decode procedures increase the energy consumption for low complexity MTC UEs, necessitating enhancements to the current mechanisms. This encourages us to investigate novel energy efficient mechanisms for LTE MTC systems. Specifically, we develop DRX with Quick Sleeping Indication (QSI), which enables the MTC UEs to go back to sleep quickly and save power, when there is no impending page from the base station. We also design the enhanced Primary Synchronization Signal (ePSS) for faster timing resynchronization, which can be used as QSI for additional improvements in the downlink energy efficiency of MTC UEs in low coverage. Further, LTE/LTE-A standardization activities in the uplink are examining different procedures to reduce UE data retransmissions for improved energy efficiency. To this end, we develop a Maximum Likelihood (ML) based uplink Carrier Frequency Offset (CFO) estimation technique for the LTE/LTE-A base station, which is robust and accurate in low coverage, enhancing the uplink energy efficiency of MTC UEs. The MTC mechanisms described in this thesis are not only simple to implement, but also require minimal changes to the present LTE/LTE-A standardization framework, promoting smooth integration into the current LTE/LTE-A networks.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat