Energy and cost implications of a traffic aware and quality-of-service constrained sleep mode mechanism

This study considers the theoretical and realistic performance of a traffic aware sleep mode mechanism in the cellular network. The study devises a sleep mode mechanism that maximises the energy saving of the network, while maintaining both the user throughput and reliability performance. The analysis combines recent developments in stochastic geometry and packet data modelling, as well as a simulation of a real cellular network. The main contribution is to show that accurate theoretical modelling of realistic network data can allow deterministic sleep mode triggers to be devised. This is shown to be highly applicable to a real network, reducing energy consumption by 15-60% throughout a day and the annual operational expenditure by 4%

Device-to-device communication in cellular networks : multi-hop path selection and performance.

Over the past decade, the proliferation of internet equipment and an increasing number of people moving into cities have significantly influenced mobile data demand density and intensity. To accommodate the increasing demands, the fifth generation (5G) wireless systems standards emerged in 2014. Device-to-device communications (D2D) is one of the three primary technologies to address the key performance indicators of the 5G network. D2D communications enable devices to communicate data information directly with each other without access to a fixed wireless infrastructure. The potential advantages of D2D communications include throughput enhancement, device energy saving and coverage expansion. The economic attraction to mobile operators is that significant capacity and coverage gains can be achieved without having to invest in network-side hardware upgrades or new cell deployments. However, there are technical challenges related to D2D and conventional cellular communication (CC) in co-existence, especially their mutual interference due to spectrum sharing. A novel interference-aware-routing for multi-hop D2D is introduced for reducing the mutual interference. The first verification scenario of interference-aware-routing is that in a real urban environment. D2D is used for relaying data across the urban terrain, in the presence of CC communications. Different wireless routing algorithms are considered, namely: shortest-path-routing, interference-aware-routing, and broadcast-routing. In general, the interference-aware-routing achieves a better performance of reliability and there is a fundamental trade-off between D2D and CC outage performances, due to their mutual interference relationship. Then an analytical stochastic geometry framework is developed to compare the performance of shortest-path-routing and interference-aware-routing. Based on the results, the spatial operational envelopes for different D2D routing algorithms and CC transmissions based on the user equipment (UEs) physical locations are defined. There is a forbidden area of D2D because of the interference from the base stations (BSs), so the collision probability of the D2D multi-hop path hitting the defined D2D forbidden area is analysed. Depend on the result of the collision probability, a dynamic switching strategy between D2D and CC communications in order to minimise mutual interference is proposed. A blind gradient-based transmission switching strategy is developed to avoid collision within the collision area and only requires knowledge of the distances to the serving base station of the current user and the final destination user. In the final part of my research, the concept of LTE-U (Long term evolution for Unlicensed Spectrum), which suggests that LTE can operate in the unlicensed spectrum with significant modifications to its transmission protocols, is investigated. How the envisaged D2D networks can efficiently scale their capacity by utilising the unlicensed spectrum with appropriately designed LTE-Unlicensed protocols is examined

Energy aware management of 5G networks

Doctor of PhilosophyDepartment of Electrical and Computer EngineeringBalasubramaniam NatarajanThe number of wireless devices is predicted to skyrocket from about 5 billion in 2015 to 25 billion by 2020. Therefore, traffic volume demand is envisioned to explode in the very near future. The proposed fifth generation (5G) of mobile networks is expected to be a mixture of network components with different sizes, transmit powers, back-haul connections and radio access technologies. While there are many interesting problems within the 5G framework, we address the challenges of energy-related management in a heterogeneous 5G networks. Based on the 5G architecture, in this dissertation, we present some fundamental methodologies to analyze and improve the energy efficiency of 5G network components using mathematical tools from optimization, control theory and stochastic geometry. Specifically, the main contributions of this research include: • We design power-saving modes in small cells to maximize energy efficiency. We first derive performance metrics for heterogeneous cellular networks with sleep modes based on stochastic geometry. Then we quantify the energy efficiency and maximize it with quality-of-service constraint based on an analytical model. We also develop a simple sleep strategy to further improve the energy efficiency according to traffic conditions. • We conduct a techno-economic analysis of heterogeneous cellular networks powered by both on-grid electricity and renewable energy. We propose a scheme to minimize the electricity cost based on a real-time pricing model. • We provide a framework to uncover desirable system design parameters that offer the best gains in terms of ergodic capacity and average achievable throughput for device-to-device underlay cellular networks. We also suggest a two-phase scheme to optimize the ergodic capacity while minimizing the total power consumption. • We investigate the modeling and analysis of simultaneous information and energy transfer in Internet of things and evaluate both transmission outage probability and power outage probability. Then we try to balance the trade-off between the outage performances by careful design of the power splitting ratio. This research provides valuable insights related to the trade-offs between energy-conservation and system performance in 5G networks. Theoretical and simulation results help verify the performance of the proposed algorithms