Stochastic geometric analysis of asynchronous multi-carrier wireless networks

This thesis mainly focuses on the modelling and performance analysis of future cellular and asynchronous multicarrier random wireless networks. In particular, the impact of asynchronous interference, and spatial distribution of users on the performance of a system is investigated. Using tools from stochastic geometry, we develop realistic yet tractable and accurate frameworks for the system-level analysis, while incorporating the interference coming from timing misaligned users.

To meet the increasing demands of data traffic, deploying more base stations is one of the foremost vital solutions. Depending on the user population, base stations needs to be deployed in an aggressive manner which makes the overall spatial distribution of base stations random. In the first part of the thesis, we model locations of base stations in a cellular network with a β-Ginibre point process (β-GPP). Available results in the literature, for β-GPP, are complex, which makes them hard to give design insights. This shortcoming is addressed in this thesis, and an approximate expression for the coverage probability is derived. We use the horizontal-shift method, proposed in the literature, to compensate for the approximation errors.

In the context of asynchronous multicarrier wireless networks, we first study the impact of inter-carrier interference (ICI) in an orthogonal frequency division multiplexing (OFDM) based wireless network. We develop an analytical framework for the performance analysis in a frequency selective wireless channel as a function of maximum timing offset. Moreover, the position of a used subcarrier, within the available spectrum is taken into consideration. To make the analysis more practical, we use the social interaction based connectivity model and its effect on the overall coverage is addressed.

For spectrum sharing and mutual interference avoidance, carrier sense multiple access (CSMA) protocols are prevalent in random wireless networks. Recently, there has been an interest in using multi-channel operation of CSMA for short burst transmissions, as in the Internet of Things (IoT) networks. In this thesis, we derive a closed-form expression for estimating the intensity of users transmitting on different subchannels within the available bandwidth. Subsequently, an expression for approximating the coverage of a typical user for a particular subchannel is derived. For the same MC-CSMA based wireless network, we analyze the performance degradation due to asynchronous interference from the adjacent subchannels. To this end, we first provide a detailed link-level analysis for timing-misaligned cyclic-filter bank multicarrier (C-FBMC) waveform, and determine the coverage of a typical receiver in the network. Finally, a system-level comparison of OFDM and C-FBMC is provided.