Digital Revolution occurred with the sweeping changes brought about by digital computing and communication technology. This revolution resulted in dawning of digital age in which the use of digital technology became prevalent and of common use. One stepping-stone in the field of communication was the modernisation of mobile phones, which have now been transformed to smart-phones. As the number of smart phones is rapidly increasing and new smart devices are introduced continuously to meet user demands, the crowd of smart-devices is getting saturated. Increasing demand of internet-connected device and data application is burdensome for the currently deployed cellular wireless networks. When the number of users is small in a region the deployment of wireless networks becomes expensive and cumbersome. The infrastructure of a typical wireless network comprises a set of Base Stations (BS) that provides coverage to users in a given geographical expanse (called cell). The low population density of New Zealand limits the amount of investment in installing a large number of BSs. Consequently, many areas across the country do not receive network coverage and users remain disconnected from the central cellular service providers. The newly introduced concept of Device-to-Device (D2D) communication is ideal for New Zealand because it allows BS-free data exchange between users. In the D2D-based communication, relaying plays an important part and can be considered as a backbone for establishing D2D communication in multicellular environment. Realisation of relaying is possible with the help of a number of emerging cellular technologies. Currently, the Fourth Generation of mobile phone networks employs Orthogonal Multiple Access Scheme to access multiple users. However for the future generations, Non-Orthogonal Multiple Access (NOMA) scheme is a novel candidate scheme that can lay a foundation of relaying in future networks. This project examines robust relaying mechanisms in D2D communication with energy harvesting in cellular networks and aims to design an effective relaying strategy with scavenged energy and improved spectral efficiency in static and dynamic cellular environments based on NOMA.