Abstract
The ubiquity and convergence of wireless communication services have resulted in an unprecedented popularity of mobile communications. As a result, wireless communication is in constant evolution with the latest development being the massive deployment of base stations to support ever-growing user demands for efficient and reliable communication services. Given that wireless communication systems operate on radiofrequency waves, the electromagnetic (EM) emissions they generate could have adverse health effects on humans, as it has been recently suggested by the World Health Organisation. Moreover, given the current densification of base stations and extensive usage of mobile devices, exposure due to EM emissions is foreseen to greatly increase in the near future. Hence, the aim of this thesis is to propose novel techniques for minimizing EM emission from wireless communication systems. In order to achieve this, an extensive survey of EM exposure in mobile communication systems has been carried out at first, and promising solutions have been identified. The first part of thesis provides a comprehensive survey of existing literature as well as a tutorial on dosimetry. It also includes metrics, guidelines and limits on the exposure from EM emission in mobile communication systems. Furthermore, potential techniques to minimize EM emission in wireless systems are discussed. Based on the review of these techniques, the second part of this thesis proposes novel three-dimensional resource allocation techniques (frequency, power and time) to minimize EM emission in the uplink of single cell system with orthogonal frequency division multiple access (OFDMA). Two EM emission-aware schedulers are proposed by taking into account the signalling power, quality of service target as well as the data transmission power of each user in the network, such that a detailed analysis of EM emission minimization in the uplink of OFDMA is provided. Simulation results show that the novel schemes developed in this thesis significantly outperform existing energy-efficiency and spectral efficiency based scheduling schemes in terms of EM emission reduction. The third part of this thesis combines the single cell three-dimensional resource allocation with base station coordination to minimize EM emission in the uplink of multicell systems with OFDMA. A novel EM emission-aware resource allocation scheme is proposed for the multicell scenario whereby a central scheduler performs user grouping and subcarrier allocation. Two power allocation algorithms are proposed for the scheme to minimize EM emission. The first power allocation algorithm is iterative by design and it involves multicell iterative optimization to obtain the transmit powers of each user to minimize EM emission in the system. The second power allocation algorithm, on the other hand, uses the average channel gain of the users in each group to obtain the approximate transmit power of each user to minimize the EM emission over a transmission window without the need for multicell iterative optimization. Simulation results show the effectiveness of the proposed scheme that also significantly outperforms existing scheduling schemes in terms of EM emission reduction.