Improving the spectrum usage efficiency of personal area devices using cognitive radio technology
Personal Area Devices (PADs) typically access the wireless spectrum opportunistically. However, the wireless spectrum is inefficiently occupied by licensed or Primary Users (PUs). Cognitive Radio (CR) technology supports opportunistic and efficient spectrum usage by enabling devices to sense and dynamically allocate spectrum. In this dissertation, the goal is to improve spectrum usage efficiency in wireless PADs through the innovative use of CR technology. Overall energy efficiency can be achieved by minimizing the power output for each communication device. To this end, proposed is a novel energy saving adaptive transmit power control (TPC) algorithm based on bit error rate (BER) feedback that outperforms conventional approaches. It is a distributed algorithm that can be applied for various wireless network topologies and protocols and addresses the power efficiency of adaptive TPC in terms of reduced total transmit power of the network by smoothing transmit power transients during adaptive iterations. Also introduced, is a novel method of modulation called Cognitive Radio Stochastic Modulation (CRSM). This method is developed for use in channels with low Signal to Interference Noise Ratio (SINR) so that total data rate can be increased without increasing BER. CRSM uses signals, at the transmitter, which have measurable variance to manipulate second order moment statistics of the composite signal (signal plus interference and noise). Finally, promotion of energy efficiency in ad hoc networks is addressed by introducing a distributed, multiple capability, leader-election algorithm designed for heterogeneous wireless mobile ad hoc networks. The proposed formulation uses a generalized closed form solution used to select leaders that promote stable, energy efficient networks based on a global ranking defined as a linear combination of N weighted, normalized rankings.