Scientists from RUDN University have created a mathematical model of reliable microwave communication for cell phones and other devices.
5G is the newest, fifth generation of mobile communication technologies, with international standards that are under development and scheduled for release by the non-profit consortium 3GPP in 2020. 5G networks will provide reliable communication and transmission delays that are no longer than one millisecond. These are requirements of a tactile Internet, where data and haptic sensations are transmitted over the network. A use of 5G could be a surgeon remotely performing an operation with an artificial hand and sense feedback within a thousandth of a second.
This is a city of the future scheme with the 5G networks. (Konstantin Samuylov)
Similar ultra-low delays are required for self-driving vehicles or virtual reality applications in order to transmit a hologram of an interlocutor—a 3D image that accurately conveys motions and gestures. The second feature of 5G networks is the ability to support high user density. Up to a million devices per square kilometer can connect to each other at an average speed of about 100 megabits per second. The peak speed on 5G networks may reach tens of gigabits per second.
Because we are on the verge of the 5G era, research aimed at enabling gigabit-rate transmission via millimeter wave channels (mmWave) is growing in interest. mmWave technology is currently used in static environments with stationary devices, usually indoor.
The implementation of mmWave in mobile networks with moving transceiving devices and where the coordination of several moving devices is required is problematic for a few reasons.
"JSAC is one of the most reputable journals on telecommunications; in its field, it is comparable to journal Nature. The impact factor of JSAC is over eight. JSAC accepts only cutting-edge research and does not publish anything that deals with accomplished projects. The editors are interested in what will be implemented in the future, and even in what might not be implemented, might not happen, that is, as a matter of fact, negative results," said one of the co-authors, Konstantin Samuylov, head of the Institute of Applied Mathematics & Communications Technology of RUDN University.
"In our paper, we 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 we seek to find ways to use the microwave range despite its limitations while maintaining quality," Samuylov said.
One part of the international research team was working on structural issues and long-term prospects, and the other part was making simulators—software tools that technically model the system of the future. These were used by the scientists to solve the communication reliability problem -- how to maintain the communication between devices even though the connection has a discontinuous nature.
"It is said that by means of their model's mathematicians get a glimpse of the future, but I would put it another way: we, mathematicians, rather provide support to those who try to do so," said Professor Samuylov. "First, a system is developed; second, it is studied from the technical point of view, and only then comes a mathematical research. These three components must be present in a paper for a high-ranking journal, and all three must be strong and cutting-edge. For example, at every step during the review period we had to prove that our work meets the ultramodern criteria."
Other than the signal loss, the research team has been working on other problems that exist in 5G. One of the problems is effective radio resource allocation in the network. LTE (Long-Term Evolution) has been on our smartphone screens for a long time. The LTE standard is the base of 5G networks, but today its frequency range is close to saturation. This means 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.
"Here are the challenges humanity faces: the first one is that the capacity of mobile communication frequencies will soon be exhausted, the second is that network equipment will face electricity deficit," Samuylov said.
Opening a new frequency range, mmWave, to a high-density mobile network is an attempt to respond to one of these challenges. A solution to the communication blocking problem in a heterogeneous mobile network has also been suggested. If a mmWave connection is blocked, then it can be transferred to a Wi-Fi or LTE network. This is a simplified picture of connection reliability measures a 5G network. To analyze this network, mathematicians solve optimization problems to minimize transceiver power consumption or to optimize 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," Samuylov added.
A paper on this research was published in a special issue of the IEEE Journal on Selected Areas in Communications (JSAC) and will be presented at the “Enabling Technologies, Application and Methods for Emerging 5G Systems” at the University Mediterranea of Reggio Calabria from October 9-11, 2017.
