The growing complexity of System-on-Chip (SoC) designs motivates both academic and industrial researchers to find better solutions for the complexity of the chip-interconnect. For SoC designs that have hundreds of Processing Elements (PEs), a single shared bus can no longer be accepted as an efficient communication scheme. To address this problem, the Networks-on-Chip (NoC) concept is proposed as a new paradigm, which provides an integrated solution for achieving efficient interconnection scheme for complex SoC applications. NoC-based designs are composed of computational resources in the form of PE cores, and switching nodes (routers) that allow PEs to communicate with each other. For different applications, this research work: 1) proposes new analytical models for various NoC design parameters, 2) performs comparative analyses of the commonly used network architectures, and 3) presents novel methodologies for efficiently designing the NoC-topology. The proposed methodologies are developed to help NoC-designers better achieve minimum power consumption and delay, and maximum performability for their applications. Graph-theoretic concepts are adopted to study the topological architecture of NoCs and propose a new topology-based models for network power, performability, and delay. The proposed models take into consideration important design parameters, which significantly affect the power, performability, and delay of a NoC-based system; such as network topology architecture, traffic distribution, noise power, voltage swing, probability of edge failure, router design and number of ports, clock frequency, and target technology. In this dissertation, we show how the proposed models could be used to optimally design the network topology so that it achieves the target design requirement for a given application. After studying each design metric individually, a joint consideration of NoC power, performability, and delay is carried out simultaneously. We use Particle Swarm Optimization (PSO) to find the optimum network topology, that achieves minimum delay, maximum performability, and minimum power consumption, for a given NoC application. Real case studies are presented to validate the proposed theoretical concepts. This validation is carried out through experimental work, targeting various real NoC applications. Experimental results show that using the proposed design methodologies, designers can improve the overall system efficiency in terms of power, delay, and performability, by choosing the design parameters (i.e., network topology architecture, PEs’ mapping, etc.) efficiently at early design phases. This improvement is measured in some cases by an order of magnitude, compared to the worst case scenario of choosing wrong design parameters for the target application. / Graduate