People are increasingly adopting smartphones and other electronic devices to interact with the global network of interconnected computers, people, and infrastructure. So much so that it is not unusually to have indoor spaces such as restaurants or classrooms or offices with hundreds of interconnecting devices that share space with computers that control the space. These can be household items such as TVs or music players, but also building control device such as thermostats, heating systems, lighting control, security cameras and the like.  Cisco estimates that by 2023 there will be almost 30 billion devices connected to the internet.  A critical challenge is how to keep up with the wireless capacity serving this burgeoning growth and especially in spaces where many humans congregate: the aforementioned restaurants, classrooms, offices, and the like, where there is a high density of connected wireless devices.

Multiple strategies are in play to keep up with the demands in this setting. This involves finding new radio frequency spectrum to allocate to the devices, or developing higher parts of the spectrum including “millimeter wave,” and “optical” bands. But these higher frequencies have different properties; mainly, they transmit in the direction that you steer them.  Because they can provide huge increases in wireless capacity, it is worthwhile to work around their nuances to be able to bring them into the mix. And this is where the project research comes in: to find a way for existing radio frequency communications to complement the characteristics and limitations of very high speed “directional media” such as millimeter wave and optical.

The project focuses on the four main topics of: (1) How existing radio frequency spectrum can be used to successfully offload data traffic under conditions where the directional communications performs poorly, such as when devices move away from overhead access points or is blocked. (2) How the new directional media can vastly increase available capacity for wireless devices without introducing the interference that would be caused by densely located radio frequency access points. (3) Creating a way to design the best performance in a system with pre-existing wireless and the addition of new directional media.  (4) And demonstrating that these new models and control mechanisms work in practice, using a testbed equipped with RF access points and a dense grid of overhead optical sources.

The most significant results from the grant include:

• Development of new ways to control the field of view of an optical receiver when used in conjunction with a radio frequency access point. By controlling the field of view and the direction that the receiver points, a substantial gain in system performance is realized even under conditions of device movement or change in orientation.
• The analysis of the throughput enhancement of the hybrid radio frequency/optical system and the study of the impact of the medium access control protocol and random access on the enhancement.
• For the case of mobile users transiting through multiple access points, we demonstrated a machine-learning method that combines deep learning and model-free reinforcement to realize performance predicted in analytical studies. This method is important to extract the best performance out of hybrid radio frequency and optical wireless networks.
• The design and analysis of a modulating signal that is compatible with both optical and radio transmissions and its integration in a hybrid radio-optical wireless network. The novel signal adds a security level in the physical layer and uses the OFDM digital modulation scheme used in current “Fifth Generation” telecommunications and is considered in future generations. The communication chain is implemented based on classical building blocks and artificial Intelligence-based machine-learning techniques. In the presence of an eavesdropper, the analysis show that the eavesdropper becomes oblivious to the transmitted information, which is equivalent to random guessing.
• Demonstration of using mixed directional media (radio frequency and optical) in a real wireless testbed scenario, showing the performance gains achievable for existing WiFi access points and overhead optical access points also used for lighting.

The work demonstrates the potential for exploiting coexisting wireless media types that complement each other and greatly increases combined wireless performance. It also lays the foundation for the analysis and design of future co-existing media designs especially as new areas of the spectrum are enabled, such as the emerging THz band which is important as humanity’s appetite for wireless connectivity continues to grow without bound.

Last Modified: 11/01/2020
Modified by: Abdallah Khreishah