Tackling the looming spectrum crisis in Wireless Communication

The advent of the first mobile phones in the 1980s marked the beginning of mobile communications for commercial purposes. Now, thirty years later, wireless connectivity has become a fundamental part of our everyday lives and is increasingly being regarded as an essential commodity like electricity, gas and water. This unparalleled success means that we are today facing the imminent shortage of radio frequency (RF) spectrum: It is predicted that the amount of data sent through wireless networks will increase by a factor of 10 during the next five years. Moreover, data from Qualcomm demonstrates that the spectrum efficiency (number of bits transmitted per Hertz bandwidth) is saturating. Therefore, the US Federal Communications Commission has warned that a "spectrum crisis" is looming.

The proposed work in this EPSRC Fellowship is aimed at providing radical new solutions to this fundamental and far reaching challenge. A key pillar of the proposed work is the extension of the RF spectrum to include the infrared as well as the visible light spectra. The recent advancements in light emitting diode (LED) device technology now seems to let the vision of using light for high speed wireless communications become a reality.

Using light has many key advantages as compared with RF. The available spectrum is vast, the visible light spectrum is 10,000 times larger than the RF spectrum; it is free as it is not subject to government regulations; it is more secure than the radio frequency spectrum the signals of which can be intercepted outside a premise; it can achieve three orders of magnitude higher data density per unit area. Compared to the infrared spectrum, the visible light spectrum has additional advantages. First, it is not power-limited due to eye-safety concerns. Second, it can serve two purposes at the same time: illumination and high speed data transmission, resulting in a better use of energy. However, while several hundred megabit per second (Mbps) have been demonstrated for a single link using an off-the-shelf white LED, 1 gigabit per second (Gbps) and room coverage is still an open issue. In addition, there is little research for multi-user networked OWC systems. Also, the effects of dimming on the achievable data rates are not well understood. In addition, there are environments and scenarios where the use of light is difficult or not possible such as when there is heavy blockage between transmitters and receivers, or when terminals move with high speeds. In those situations, it will still be more appropriate to use the RF spectrum. To sum up, there are potential large overall performance improvements when wireless systems can select their transmission medium autonomously and in a dynamic as well as self-organising fashion.

A second essential pillar of the proposed research is to overcome the RF spectrum efficiency saturation of current cellular systems while at the same time reducing the energy consumption. A key to solving this issue is to successfully tackle interference in wireless networks which occurs when multiple communication links in close vicinity use (or reuse) the same bandwidth or frequency. On the one hand frequency reuse is beneficial since the more often transmission resources are used per unit area, the higher the spectrum efficiency. On the other hand, intensive frequency reuse results in the aforementioned interference issues. Radically new approaches will be followed that include interference already in the design of a new wireless air-interface. In the past, wireless air-interfaces were optimised for single transmission links, and performance degradations due to interference in a system deployment were mended subsequently, but existing solutions are either impractical or sub-optimum. We will investigate a new air-interface that is based on the recent successful demonstrations of and world-wide research on the concept of spatial modulation which was originally proposed by the applicant.

Industry: The applicant and his team will create intellectual property rights (IPR) in the course of the Fellowship programme. The IPR will be used to either create new spin-out companies, or to license the technology to industry. A recent example for the first is pureVLC Ltd which the applicant spun-out from a university project. There is a general opportunity to establish a new UK industry that sits between the traditional lighting industry and wireless communication industry and is world-leading. We will also work with industrial partners such as Bell Labs / Alcatel Lucent (Ireland) on combining their RF femtocell work with our OWC technology, and we will use their existing testbed to demonstrate the world's first optical femtocell.

Academia: The applicant will publish the research in the most respected journals and top conferences in the area. Visits to and from leading international research teams will be organised as a means of sharing and discussing latest research findings and to further advance the field.

Society: Through the transfer of knowledge into industry, there will be new products that will enable safe, green and secure wireless communications. The World Health Organisation issued the following statement on 31 May 2011: "The World Health Organization's International Agency for Research on Cancer (IARC) today classified mobile phone use and other radiofrequency electromagnetic fields as a possible carcinogen (group 2B)". While clearly there is no evidence of any health risks stemming from RF communication, the statement suggests that research has not fully eliminated health concerns. The visible light spectrum, on the other hand, is not subject to any health concerns, and in particular schools and hospitals could benefit from the technology. Moreover, the work in both OWC and RF communication targets energy reductions of cellular communication systems of at least an order of magnitude which will lead to substantial reductions in CO2 emission. Smart-home environments enabled through low complex OWC systems will further contribute to the reductions in CO2 emission.

Economy: There are a number of sectors and industries that could benefit from this work:
- Oil and gas industry: Wireless communications in hazardous environments such as oil platforms and petrochemical plants (no danger of electric spark discharges)
- Transportation:
* Aircraft: In-cabin wireless communication to save weight and enhance passengers services (no interference with sensitive RF communication systems)
* Cars: Intra- and inter-vehicle communications (exploiting existing lights and their directional radiation)
* Traffic and street lights that broadcast local information (exploiting existing signalling and illumination units for smart cities)
- Businesses:
* Corporate and organisation security (exploiting directional radiation of LEDs as well as the fact that light does not propagate through walls)
- Communication industry:
* WiFi and cellular spectrum relief (OWC provides significant additional and free wireless transmission resources)
* Energy efficient wireless communication systems (saving energy through illumination AND wireless data transmission at the same time)
- Defence and military (OWC for secure wireless communications by exploiting directional radiation of LEDs as well as walls and other objects that will block light)
- Museums (lights that illuminate objects and at the same time broadcast information about them)
- Toy Industry (cheap transceiver modules for toy-to-toy communication)
- Retail:
* Large shopping malls, airports and large public buildings (exploiting the localised illumination of lights bulbs that broadcast a unique identifier for indoor positioning and navigation systems)
* Shops (local information broadcast through lights)
- Underwater communication (high data rate wireless communication to enable communication between divers and between remote operated vehicles)