Research On Energy Optimization Techniques In D2D Communication

In recent years, mobile communication technologies are developing rapidly, with the demands of high-speed, low energy consuming, and supporting more personal services, which accelerate the study of emerging communication technologies. Device-to-Device (D2D) communication is a promising technology, which has been listed as one of the longitudinal subjects in the future mobile communication system by the Europe METIS2020(Mobile and wireless communications Enablers for the Twenty-twenty Information Society) group. D2D communication can establish a direct communication link between two terminals close to each other using licensed spectrum, therefore it could reduce the Base Station load and improve the spectrum efficiency. Meanwhile, as a short-range communication technology, D2D communication could achieve high data rate with low transmission power, which is conducive to the effective use of energy, and brings convenience for users by extend the endurance of terminals. This thesis focuses on the energy techniques of D2D communication.The research background and motivation are introduced first. The study on the energy techniques in D2D communication is limited, so the research in this thesis could benefit the development and application of D2D communication technology. Secondly, the stochastic geometry theory is introduced, which provides a convenient method for the interference analysis in multi-cell heterogeneous network, leading to closed-form expressions for outage probability and rate, and acts as an important theoretical tool throughout this article.To study the multi-cell scenario in which D2D communication reuses the cellular uplink channels, we proposes an interference coordination scheme based on the Exclusion Region, in other words, the locations of D2D communication are constrained in order to reduce the interference to cellular uplink signals. This scheme guarantees the quality of cellular link while developing the advantages of D2D communication, and improves the overall energy efficiency. The co-channel interference is analyzed using the theory of Poisson Point Process, and the closed-form expressions of outage probability and energy efficiency is provided. According to the simulation results, the proposed scheme could reduce the outage probability of cellular link efficiently, and the size of the Exclusion Region need not be too large, avoiding suppressing the occurrence of D2D communication. Moreover, with appropriate system parameters, such as the size of Exclusion Regions, the number of D2D communication pairs in a channel, the maximum energy efficiency can be achieved.In addition, the energy harvesting strategies in D2D cooperative communication system are explored. In this model, the cellular user locates in the blind spot of the Base Station, thus one of the idle D2D users in the relay region is selected to decode and transmit the Base Station signal to the cellular user. To compensate the energy consumption of the relay node, three energy harvesting schemes are proposed. The relay node could use part of the signal from the Base Station for information decoding, and the others for energy harvesting, or the cellular user would transmit energy to the relay in an extra period after it receives the cellular signal successfully, or the cellular user and the Base Station could transmit to the relay together in the first hop. The thesis compares these schemes in the simulation results with different location of relay region and energy harvesting parameters, and users could choose the appropriate scheme with the needed outage probability according to the result.