Scientists Develop Mathematical Model for Future 5G Mobile Communications

A team of scientists from RUDN University have developed a mathematical model of reliable microwave communication for mobile phones and other devices. The results of the research that were published in the IEEE Journal on Selected Areas in Communications (JSAC) is expected to be presented at the "Enabling Technologies, Applications, and Methods for Emerging 5G Systems" international conference at the University Mediterranea of Reggio Calabria to be held from October 9 – 11.

The new 5G standard is under development and scheduled for release by the non-profit consortium 3GPP in 2020. 5G networks will provide extremely reliable communication with high data rates and transmission delays not exceeding one millisecond. This low latency will enable a number of applications which have soo far not been possible. For example, a surgeon can remotely perform an operation with an artificial hand and sense a feedback within a thousandth of a second.

Similar ultra-low delays are necessary for self-driving vehicles or virtual reality applications, for instance, in order to transmit a hologram of an interlocutor - a 3D image that accurately conveys emotions and gestures. The second feature of fifth-generation networks is the ability to support high user density: up to a million devices per square kilometer should be able to connect to each other and transfer about 100 megabits of data per second on average. Thirdly, the peak speed in 5G networks may reach tens of gigabits per second.

On the verge of the 5G era, research aimed at enabling gigabit-rate transmission via millimeter wave channels (mmWave) is of enormous interest. mmWave technology is already used in static environments with stationary devices, in particular indoors; however its implementation in mobile networks with moving transceiving devices and where the coordination of several moving devices is required, is problematic for a number of reasons.

The announcement of the JSAC special issue on mmWave provoked a staggering response from the scientific community: in less than four months JSAC received 96 papers, the majority of which came from the most prominent research groups in the field. After a rigorous selection, 38 papers were published in two issues of the journal in July and September of this year, including the study conducted by an international team of scientists from the Royal College, London (UK), Tampere University of Technology (Finland) and RUDN University (Moscow, Russia).

According to the scientists at RUDN University, in their JSAC published paper, they analyze the use of the microwave range in high-density urban mobile networks. This range allows providing both ultra-high speed and ultra-high throughput communication to devices in rapid motion and in high-density conditions, for example on a busy street or in a large shopping center. However, the use of millimeter waves in such environments faces serious problems related to the quality of wireless communication. These include signal attenuation at relatively small distances, up to hundreds of meters, and connection sensitivity to line-of-sight blocking. The ultrashort wave transmitter is directed toward the receiver, and the radio channel is like a narrow cone of light: whenever there is a foreign object on its way (a person, a car, even a lamp post) the communication is blocked. By means of a mathematical model the team seeks to find ways to use the microwave range despite its limitations while maintaining quality.

While one part of the international research team was working on structural issues and long-term prospects, the other was making simulators - software tools that technically model the system of the future. These were used by the scientists to solve the problem of communication reliability: how to maintain the communication between devices despite the discontinuous nature of the connection.

Besides signal loss, the researchers have been working on other problems that exist in 5G. One of them is effective radio resource (frequency range) allocation in the network. The LTE standard, which is the base of 5G networks, however today its allocated frequency range is close to saturation, meaning that there are not enough radio frequencies to meet the requirements of 5G networks. The second problem is related to power consumption: in order to operate efficiently, the network requires a huge amount of electricity. A shortage may result in servers, cloud systems, routers and network components running out of coal, so to speak.

Opening up the mmWave frequency bands to high-density mobile networks is an attempt to respond to one of these challenges. A solution to the aforementioned communication blocking problem in a heterogeneous mobile network has also been suggested: if an mmWave connection is blocked, then it can be transferred to a Wi-Fi network, or, if necessary, to an LTE network. This is a very simplified picture of the connection reliability measures in a 5G network. To analyze such a network, mathematicians solve optimization problems, for example, to minimize transceiver power consumption or to optimize the frequency range.

Ultramodern 5G communications and various communication scenarios based upon them may be implemented in the future. Whether they will be implemented or not is a matter of collaboration between the academic community and the industry. It is going to be a long way, and the work done by scientists should be reflected in the standards developed by international organizations.

Among other achievements of the team includes their participation in the IEEE Globecom, a major worldwide conference on telecommunications. The selection for this conference is just as tough as for publication in JSAC; nonetheless the scientists from RUDN University presented joint results with their European partners at IEEE Globecom for two years in a row.