Multi-radio Proactive Control Technology (Cradio^®): A Natural Communication Environment where Users Do Not Need to Be Aware of the Wireless Network

1.1 Increasing communication volume and diversifying communication requirements

The concept of the Innovative Optical and Wireless Network (IOWN) has been proposed by NTT as a model for future implementation of networks [1]. The role of wireless communication is increasing dramatically in all aspects of our lives due to the growing volume of smartphone traffic and the development of Internet of Things (IoT) technology used to connect a variety of diverse objects to the Internet. It is therefore predicted that the volume of wireless communication will continue to increase. According to ITU-R^*1 Report M.2370, mobile data traffic will reach 5016 EB/month in 2030, about 80 times higher than in 2020 [2]. In particular, the volume of machine-to-machine communication, which correlates with IoT, is expected to increase by about 124 times (622 EB/month). This shows that in addition to the increase in communication volume, there will also be greater diversity in the types of wireless terminals and usage patterns of wireless communication. Mobile communication will not just be used for smartphones but also for remotely controlling automated vehicles and drones and exchanging ultra-high definition video. This diversification of wireless terminals and usage patterns means that it is important to provide wireless network coverage not only in urban areas where the population is concentrated but also in suburban and rural areas. Therefore, we must respond to the increasingly diverse requirements for wireless communication quality suitable for various forms of use.

1.2 Diversification and increased frequency of wireless networks

To address these needs, studies are underway to develop various wireless communication standards. For mobile cellular communication, commercial fifth-generation mobile communication system (5G) services were launched in 2020, and progress is now being made in the research and development of 6G technology [3]. In addition to high-speed and large-capacity communications, low-latency and highly reliable communications, and multiple connections that exceed those of 5G, 6G includes new requirements that were not considered in 5G. There are also growing expectations for the use of private 5G, which enables the flexible deployment of private 5G systems within the buildings and premises of diverse entities such as businesses and local government bodies according to the needs of individual regions and industries [4]. In wireless local area networks (LANs), IEEE^*2 802.11be is being standardized as the successor to the IEEE 802.11ax wireless communication standard, which is the technology behind Wi-Fi 6. When it finally comes out, IEEE 802.11be will support not only high-speed transmission with a maximum communication rate of 46 Gbit/s but also additional features such as multiple access points [5]. Development of the IEEE 802.11ay standard for WiGig (Wireless Gigabit) networks is also underway as a successor to IEEE 802.11ad, which uses the 60-GHz band [6]. For low-power wide-area (LPWA) networks, various demonstration experiments are being conducted with the aim of implementing Wi-Fi HaLow^TM (IEEE 802.11ah), which is a wireless communication standard for IoT applications that also supports video transmission [7].

With developments such as these, the use of diverse wireless communication standards such as public cellular, private cellular, wireless LAN, and LPWA networks is going to become more widespread. These wireless communication standards use a variety of frequency bands ranging from 1 GHz to several tens of GHz, and studies related to 6G are even considering the use of frequencies above the 100-GHz band and into the THz band [3]. Although these high-frequency bands support higher communication bandwidths, their coverage areas are smaller due to increased radio-wave propagation losses. Therefore, to properly handle user requirements that change from time to time, from location to location, and from one application to the next, it is essential to properly use complex wireless networks that support a mixture of different wireless communication standards across a wide range of frequency bands with different propagation characteristics.

NTT aims to provide a natural communication environment where users do not need to be aware of how they are using wireless networks because they are always provided with the best possible communication environment to suit their ever-changing needs and radio-wave conditions in their current location. As a constituent part of IOWN [1], we are working on the research and development of Cradio^®, a set of multi-radio proactive control technologies.

(1) Understanding (wireless sensing/visualization): Visualization of real-world conditions by wireless state measurement/visualization, wireless sensing, etc.

(2) Prediction (wireless-network-quality prediction and estimation): Prediction and estimation of constantly changing wireless communication quality

(3) Control (wireless-network dynamic design/control): Design of physical layouts in accordance with the local environment and requirements, derivation of optimum wireless parameters, dynamic control of network parameters and resources, etc.

2.1 Understanding: Wireless sensing/visualization

Wireless sensing/visualization technology (Fig. 3) collects and analyzes information from various wireless devices in various wireless communication systems to ascertain and visualize the status of wireless communication systems with regard to multiple dimensions, including frequency, method, location, and time. This makes it possible to clarify the communication quality of wireless systems, find hidden margins, and ultimately improve the efficiency of radio-wave utilization.

Fig. 3. Understanding − Wireless sensing/visualization.

By using radio-communication technologies, such as wireless sensing and wireless positioning, it is possible to ascertain and visualize the real-world conditions around wireless devices. Therefore, it should be possible to quantify the position and state of everything that affects a wireless network. These technologies create an image of the real world that is important for ensuring the quality of wireless communication. This makes it possible to understand and visualize diverse environmental factors that affect wireless communication quality, including non-communication areas in wireless communication systems. It can also be expected to create added value as a new social infrastructure.

With the technology that we have used for ascertaining and visualizing the state of wireless LANs, it became possible to check the quality of a wireless LAN in real time [8]. In addition, wireless-LAN sensing technology [9] makes it possible to ascertain the impact of the surrounding environment on wireless-communication quality and create added value for wireless communication systems. We are currently working to expand the range of target wireless systems on the basis of these technologies and make further enhancements to these technologies.

2.2 Prediction: Wireless-network-quality prediction and estimation

Wireless-network-quality prediction and estimation technology executes deep learning on the basis of information obtained from wireless sensing and visualization technology to predict and estimate the quality of wireless communication, which changes from moment to moment in accordance with the surrounding environment and terminal position [10], thereby facilitating proactive optimization on the basis of future conditions (Fig. 4). The quality of wireless communication is affected by the radio-propagation environment between transmitters and receivers and varies in accordance with the usage conditions (resource availability) of the wireless communication system. Since these conditions change from time to time, this prediction and estimation of wireless communication quality is not easy to do. With the above-mentioned wireless sensing and visualization technology, it is possible to ascertain and visualize the status of wireless communication in multiple dimensions on the basis of information collected from various devices and ascertain and visualize the real-world conditions surrounding wireless devices that affect the quality of radio communication. As a result, it should be possible to predict and estimate communication-quality parameters for each location, time period, and radio communication method with unprecedented accuracy. This will make it possible to make advance network-environment preparations in accordance with application requirements, avoid deterioration of communication quality and breaks in communication, and automatically select networks to connect to. Our aim is to provide proactive communication services that always deliver high quality of experience and quality of service.

Fig. 4. Prediction − Wireless-network-quality prediction and estimation.

We have conducted demonstration trials to predict the quality of communication between a cellular system and broadband wireless access in the control of self-driving agricultural machinery, which was able to execute network switching control to connect to a suitable network while continuing to provide the required communication quality [10]. We are currently investigating the enhancement of techniques for predicting and estimating the quality of general-purpose wireless networks by combining the various types of information mentioned above.

2.3 Control: Wireless-network dynamic design/control

In wireless-network dynamic design/control technology, on the basis of communication quality information obtained from wireless-network-quality prediction and estimation, we are carrying out switching/cooperation control of wireless-network dynamic configuration and switching/cooperation control of multiple wireless networks and control/optimization for the wireless connection of terminals (Fig. 5). As well as the optimization of various wireless parameters, this consists of comprehensive wireless-network design optimization and control measures such as the dynamic configuration of multi-radio networks with white-box wireless base stations that support multiple wireless communication standards, modification of the physical location and antenna direction of wireless base stations, and dynamic configuration of wide area network (WAN) entrances to adapt to these changes. Dynamic control can be considered not only for wireless networks but also for radio-propagation environments using equipment such as intelligent reflectors. This will make it possible to provide a world where wireless networks can be dynamically prepared wherever and whenever they are needed, facilitating a departure from the presumption of pre-prepared communication environments using conventional fixed wireless base-station locations and specified wireless communication standards. Using these technologies, our aim is to proactively and automatically configure optimal wireless networks to accommodate ever-changing user requirements and radio-wave conditions. This will lead to wireless networks that operate more efficiently and consume less power.

Fig. 5. Control − Wireless-network dynamic design/control.

On the basis of wireless-resource dynamic control technology for wireless LANs that we have previously studied [11], we are working on practical technologies for the expansion and technical enhancement of target wireless systems, dynamic control of base-station placement (which have hitherto been fixed) [12], and implementation of distributed intelligent reflectors [13].