The wireless networks of the future are likely to be tiered, i.e., a heterogeneous mixture of overlaid networks that have different power, spectrum, hardware, coverage, mobility, complexity, and technology requirements. The focus of this dissertation is to improve the performance and increase the throughput of tiered networks with resource/interference management methods, node densification schemes, and transceiver designs; with their applications to advanced tiered network structures such as heterogeneous networks (i.e., picocells, femtocells, relay nodes, and distributed antenna systems), device-to-device (D2D) networks, and aeronautical communication networks (ACN). Over the last few decades, there has been an incredible increase in the demand for wireless services in various applications in the entire world. This increase leads to the emergence of a number of advanced wireless systems and networks whose common goal is to provide a very high data rate to countless users and applications. With the traditional macrocellular network architectures, it will be extremely challenging to meet such demand for high data rates in the upcoming years. Therefore, a mixture of different capability networks has started being built in a tiered manner. While the number and capabilities of networks are increasing to satisfy higher requirements; Modeling, managing, and maintaining the entire structure has become more challenging. The capacity of wireless networks has increased with various different advanced technologies/methodologies between 1950-2000 which can be summarized under three main titles: spectrum increase (x25), spectrum efficiency increase (x25), and network density (spectrum reuse) increase (x1600). It is vital to note that among different schemes, the most important gain is explored with increasing the reuse and adding more nodes/cells into the system, which will be the focus of this dissertation. Increasing the reuse by adding nodes into the network in an uncoordinated (irregular in terms of power, spectrum, hardware, coverage, mobility, complexity, and technology) manner brought up heterogeneity to the traditional wireless networks: multi-tier resource management problems in uncoordinated interference environments. In this study, we present novel resource/interference management methods, node densification schemes, and transceiver designs to improve the performance of tiered networks; and apply our methodologies to heterogeneous networks, D2D networks, and ACN. The focus and the contributions of this research involve the following perspectives: 1. Resource Management in Tiered Networks: Providing a fairness metric for tiered networks and developing spectrum allocation models for heterogeneous network structures. 2. Network Densification in Tiered Networks: Providing the signal to interference plus noise ratio (SINR) and transmit power distributions of D2D networks for network density selection criteria, and developing gateway scheduling algorithms for dense tiered networks. 3. Mobility in Tiered Networks: Investigation of mobility in a two-tier ACN, and providing novel transceiver structures for high data rate, high mobility ACN to mitigate the effect of Doppler.

Device-to-device (D2D) networking enables direct discovery and communication between cellular subscribers that are in proximity, thus bypassing the base stations (BSs). In principle, exploiting direct communication between nearby mobile devices will improve spectrum utilization, overall throughput, and energy consumption, while enabling new peer-to-peer and location-based applications and services. D2D-enabled broadband communication technology is also required by public safety networks that must function when cellular networks are not available. Integrating D2D into cellular networks, however, poses many challenges and risks to the long-standing cellular architecture, which is centered around the BSs. This dissertation identifies outstanding technical challenges in D2D-enabled cellular networks and addresses them with novel models and fundamental analysis. First, this dissertation develops a baseline hybrid network model consisting of both ad hoc nodes and cellular infrastructure. This model uses Poisson point processes to model the random and unpredictable locations of mobile users. It also captures key features of multicast D2D including multicast receiver heterogeneity and retransmissions while being tractable for analytical purpose. Several important multicast D2D metrics including coverage probability, mean number of covered receivers per multicast session, and multicast throughput are analytically characterized under the proposed model. Second, D2D mode selection which means that a potential D2D pair can switch between direct and cellular modes is incorporated into the hybrid network model. The extended model is applied to study spectrum sharing between cellular and D2D communications. Two spectrum sharing models, overlay and underlay, are investigated under a unified analytical framework. Analytical rate expressions are derived and applied to optimize the design of spectrum sharing. It is found that, from an overall mean-rate perspective, both overlay and underlay bring performance improvements (vs. pure cellular). Third, the single-antenna hybrid network model is extended to multi-antenna transmission to study the interplay between massive MIMO (multi-input multiple-output) and underlaid D2D networking. The spectral efficiency of such multi-antenna hybrid networks is investigated under both perfect and imperfect channel state information (CSI) assumptions. Compared to the case without D2D, there is a loss in cellular spectral efficiency due to D2D underlay. With perfect CSI, the loss can be completely overcome if the number of canceled D2D interfering signals is scaled appropriately. With imperfect CSI, in addition to pilot contamination, a new asymptotic underlay contamination effect arises. Finally, motivated by the fact that transmissions in D2D discovery are usually not or imperfectly synchronized, this dissertation studies the effect of asynchronous multicarrier transmission and proposes a tractable signal-to-interference-plus-noise ratio (SINR) model. The proposed model is used to analytically characterize system-level performance of asynchronous wireless networks. The loss from lack of synchronization is quantified, and several solutions are proposed and compared to mitigate the loss. / text