5G’s Next Generation Heterogeneous Networks

Prof. Seiichi Sampei, Chairman, Technical Committee

A world is coming when wireless bottlenecks will come to an end thanks to fifth generation (5G) cellular systems. Additionally, requirements for latency will be more strictly determined, that is not a necessary transmission time from a server to a terminal, but an End-to-End round trip time between a controller and an equipment to be used for Industry 4.0 systems and IoT systems. Although latency of 1ms is not short enough for control systems, it would be definitely the starting point for 5G cellular systems.

Another point to be considered is that we have to evolve our services from best effort services to End-to-End quality guaranteed services. In other words, we need to develop wireless access and network technologies having flexibility that can cope with locally happened unexpected and extreme situations. Heterogeneous network would be a key technology to cope with it in 5G cellular network technology (it is called HetNet in 3GPP). Although HetNet is already introduced in 4G, it is used only to enlarge system capacity in high traffic density local areas.

Basic concept of HetNet is to introduce micro cells in a macro cell area to provide features the macro cell itself cannot cope with, such as extreme changes in the required user traffic and latency. Such a environment is different depending on places, and time. The main purpose of 5G HetNet is to provide wireless access links to any devices under extremely high traffic and low latency requirements.

In addition to support higher capacity in HetNet, when we need to cope with some other user requirements, a new Radio Access Technology (RAT) can be introduced in microcell of HetNet. In this case, millimeter wave transmission will be available in the near future because we can utilize extremely wide bandwidth in millimeter wave bands.

Of course, Hetnets are being discussed in the technical committee. But it is not only an issue for the technical committee; it is also dependent on networking. For example, although cloud network is useful for everybody because we can create a server-and-client system without knowledge of network configurations. However, it would also block necessary knowledge for latency expectation to each user. It would be the most important motivation why edge server/controller is necessary to reduce End-to-End latency in 5G cellular systems. Currently most of the discussion on edge server/controller is done in the Network Architecture Committee, and the Technical Committee is developing HeNet technologies in cooperation with the Network Architecture Committee.

Another interesting future technology is beamforming, in which massive MIMO and array antennas with more than 100 elements are developed. Using these technologies, we can suppress performance difference between terminals located closer to the base stations and located in the cell edge. Moreover, because transmit energy radiated from the base station to a terminal is efficiently directed to a terminal, it would work effectively to create ecosystems.

For industrial partners in the 5GMF, it is important to strategically consider standardization necessary issues and non-standardization issues. As for vendors and operators in Japan, such consideration has not been so sufficient. What I mean is that both cooperation (using standards) and competition (using technology/ideas without standards) would be necessary in the market driven era. If we lose new market abroad, new products will lose their market even in Japan.

Revenue structures need to change their focus from looking at the number of users to looking at the number of connected devices (in other words, the IoT). Even though the per unit price is going to decrease, the number of objects sold will be magnitudes different than before, meaning overall revenue will increase dramatically.

Additionally, critical differences in the future mobile business will be powered by user groups. In other words, new markets will come into existence due to what users requires. Although current user groups do not have so strong market controllable power in ICT, it will change in the future. With an understanding of these ideas, the 5GMF is working to lead the most advanced discussions on these issues, and we would like to hear more voices, especially from user groups which are considering to connect their systems to 5G networks in the future.