Network-level modelling and optimization of energy neutral ultra-dense heterogeneous networks based on simultaneous wireless information, power transfer and renewables
Résumé
The availability and reliability of the power grid is set to become a major bottleneck in providing connectivity in future generations of wireless networks. In developing countries, the booming of mobile networks cannot be accommodated due to the limited power grid infrastructure. For example, in Africa only 10% of individuals have access to the electrical grid, and cellular coverage is only at 15%, as the ICT development cannot keep up with the fast market growth using conventional electricity-hungry BSs. In the developed world similar requirements arise in emergency network deployment for rapid connectivity provisioning in disaster areas, as well as in broadband provisioning in massive-scale social events such as sports events and concerts, with limited access to the power grid. Furthermore, even developed countries contain several regions that have low broadband penetration, such as in remote areas or areas with poor wireline infrastructure for backhauling. At the same time, natural disasters, excessive power demand (such as during unexpected heat waves or cold fronts that reflect the climate change) or even malicious attacks on the power grid, often result in blackouts that can jeopardize ICT-critical applications and the safety of the public. To the existing spectrum-crunch in wireless networks, a looming power-crunch is then added. This is further aggravated by the requirement for future cellular communication systems to cut their CO2 emissions by at least 40% by 2020 compared to 1990.
A paradigm shift from energy-efficient (EE) networks to energy-neutral (EN) networks is hence vital, towards enabling self-powered networks that are unplugged from any fixed infrastructure (“infrastructure-less”). The importance of having grid-independent base stations (BSs) cannot be overstated. Self-powered communication networks provide a critical solution to the above, and some aspects of this research area have recently attracted the attention of major ICT players. Significant market opportunities have been identified for this technology and an annual deployment rate exceeding 84,000 standalone BSs worldwide, using a combination of renewable energy and diesel generators, is expected for 2020.
The above is evidence that the demand for wireless networks is stretching beyond the reach of the power grid infrastructure. Self-powered BSs are an essential technological step in making the above a reality. They will rely on renewable energy such as wind, solar, kinetic, radiated power as well as high-efficiency high-capacity batteries. Renewable-Energy powered BSs (REBs) could also be incorporated into conventional networks to reduce energy bills and hence the cost per megabyte seen by the users. Such energy-neutral operation can be achieved through a combination of cost-effective recharging of the batteries, e.g. by using excess self-generated power or recharging during low-traffic time, as well as by using green energy as an alternative / complement to the electrical grid.
Looking forward, we envision a grid-independent network of small, portable, and flexibly deployable BSs with the potential to replace the power-grid restricted pico and femto BS topologies, towards infrastructure-less communication networks. It also aims for a dramatic improvement in the network coverage of problematic / remote / developing areas, to the coverage levels of urban networks in the developed world. This coverage will not be based on a wasteful static network, but instead on a flexible, green and “on demand” provision of ICT services.
The Ph.D. thesis addresses different problems of realizing this long-term vision. More precisely, it has two technical objectives.
•Objective 1: To develop a comprehensive mathematical theory for analyzing ultra-dense cellular networks whose low-energy mobile devices and base stations can be powered via conventional power generators, radio frequency energy (e.g., power beacons) and renewable energy sources.
•Objective 2: To develop a new approach based on the theory of point processes will be developed that accounts for practical deployment constraints, such as the actual location of all network elements, the network traffics, and practical propagation conditions at low (sub 6 GHz) and high (millimeter-wave) frequencies.
The expected results of the Ph.D. thesis can be summarized as follows:
•Expected result 1: A new mathematical methodology for system-level analysis based on inhomogeneous point processes.
•Expected result 2: Design insight for network planning and system level.
•Expected result 3: Quantification of the actual potential of emerging power (green) sources for cellular / portable network applications.
The Ph.D. thesis will be developed in the Laboratory of Signals and Systems, CentraleSupelec, Gif-sur-Yvette, France.