The National Institute of Information and Communications Technology (NICT) announced on July 24 that it developed an algorithm that integrates quantum and digital technologies for a new computing method that combines an annealing-type quantum computer with a conventional classical computer. NICT also announced that they succeeded in performing a communication experiment for simultaneous outdoor multiple connections, which are required for next-generation mobile communication systems such as 6G mobile communication systems.
In current fifth generation (5G) mobile communication systems, the base station communicates with one terminal station per base station antenna using the same frequency and time. Meanwhile, next-generation mobile communication systems are expected to increase the number of simultaneous connections to more than 10 times that of the current systems.
The non-orthogonal multiple connection technology is considered a candidate for such multiple connection technology. This technology used in wireless communications allocates time and frequency to avoid interference in communications between a base station and multiple terminal stations. By contrast, the non-orthogonal multiple connection technology increases the number of simultaneous connections instead of allowing interference between terminal stations. However, because, in this technology, signals transmitted from multiple terminal stations per base station antenna are received at the same time and frequency, it is necessary to separate and process the signals received at the base station to retrieve data transmitted from individual terminal stations. Moreover, because base stations receive superimposed signals transmitted from multiple terminal stations, signal separation processing is required at each terminal station. Furthermore, as the number of terminal stations increases, the number of received signal combinations increases exponentially, increasing the computational volume of signal separation processing and making it time-consuming.
Therefore, NICT decided to use a quantum annealing machine that can solve combinatorial optimization problems at a high speed. Note that signal processing in next-generation mobile communication systems requires not only combinatorial optimization for the signal separation of non-orthogonal multiple connections but also general-purpose computational processing. However, quantum annealing machines are not well-suited for general-purpose calculations. Hence, they decided to use a conventional classical computer. However, it is not simply a matter of connecting the two systems.
They developed a new practical quantum-digital hybrid algorithm designed to take advantage of the strengths of each computer and realized the integrated use of a quantum annealing machine and a classical computer, which are based on different principles. From this, NICT confirmed via simulation that at least seven terminal stations can be connected simultaneously to each base station antenna and demonstrated simultaneous connection with four terminal stations through an outdoor experiment.
This is the first time that a quantum annealing machine has been used for the online demonstration of non-orthogonal multi-connection technology in the field. In the future, NICT plans to improve and demonstrate its computing method (hybrid algorithm) to achieve 10 times the number of 5G connections. In addition, because the developed algorithm can be applied to applications beyond wireless communication signal processing, in the future, they expect to use it in fields where various types of combinatorial optimization are required.
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.