• Japanese operator is testing the potential of quantum computing to improve radio access network (RAN) performance
• SoftBank says a Tokyo proof of concept shows that significant speed and capacity gains can be achieved in 5G networks where carrier aggregation is being applied
• The operator is exploring other ways to use quantum computing in its operations

SoftBank Corp. is exploring the potential of quantum computing to improve radio access network (RAN) performance by conducting a proof-of-concept (PoC) experiment in Tokyo that has had very positive results. 

The Japanese telco has applied an ‘Ising machine’ – a dedicated computing system that can undertake quantum as well as classical computing tasks and which is designed to solve “combinational optimisation problems” – to cellular base station settings in a 5G network where carrier aggregation (CA) is being applied, it noted in this announcement. 

The PoC showed that downlink data speeds can be improved by about 10% when the Ising machine computation is applied, while data transmission capacity can be increased by up to 50%. 

SoftBank noted that carrier aggregation – the simultaneous use of multiple spectrum bands (or ‘carriers’) – requires pre-defined associations, known as ‘CA links’, between base stations. The telco noted that “as the number of base stations increases, determining the optimal CA link configuration becomes exponentially more complex. For instance, selecting pairs from 10 base stations yields 45 combinations. Since each pair can either be linked or not, the total number of possible CA link patterns reaches 35 trillion... Moreover, constraints such as the maximum number of CA links assignable to each base station further complicate the task, making it extremely difficult to identify the optimal combination that maximizes CA-enabled area coverage.”

So you can see why classical computing might struggle to optimise the CA settings to optimise mobile connectivity in near real time. 

In the PoC, SoftBank divided an area of Tokyo with multiple 5G base stations into “a fine-grained mesh. Meshes that could simultaneously receive signals at different frequencies from multiple base stations were identified as location candidates for CA deployment. Based on this mesh information, the optimal combination of CA links to maximise the number of CA-capable meshes was computed using quantum computing technology (see SoftBank’s Figure 1 diagram below).” The required computation was formulated as a mathematical optimisation problem and solved using an Ising machine.

The results were then used to generate a CA link configuration and simulate the potential CA coverage area: “The simulation confirmed that CA could be made available over a broader area compared to conventional configurations,” as seen in Figure 2 (below), noted the operator. When the configuration was applied the CA coverage area expanded and SoftBank registered an average downlink data speed enhancement of 10%. 

In addition, both the CA utilisation ratio (the proportion of connections making use of CA) and the amount of data transmitted via secondary cells (supplementary channels connected in parallel with the primary cell) increased by up to 50%, according to SoftBank. 

The telco concluded: “These results demonstrate that optimising base station settings using an Ising machine enables more efficient utilisation of the radio spectrum and leads to improved communication performance. This technology contributes to delivering a more seamless user experience, such as smoother high-resolution video streaming and online gaming.” 

Quite when such techniques will be used in the operator’s production network on a permanent basis, or exactly what resources would be needed to apply such optimisation techniques to (for example) an entire urban 5G network, is unclear, but what is clear is that significant gains are possible using quantum computing processes.

SoftBank also noted that it will “consider applying quantum computing technologies not only to network architecture optimisation, but also to operational enhancements, aiming to expand these initiatives across a broader range of services.”

This isn’t SoftBank’s first foray into the quantum tech sector. In February this year it entered into a “wide-ranging” partnership with Cambridge, UK-based Quantinuum that will involve the duo demonstrating the practical application of quantum computing, developing a model for a ‘quantum datacentre’, and driving the commercial value of quantum computing via practical use cases – see SoftBank and Quantinuum team up for quantum computing R&D.

And in March this year it provided an update on its developments related to the  “practical implementation of a hybrid network that integrates conventional internet technologies with quantum internet technologies, aiming to establish the infrastructure for a future quantum society”. The operator has been exploring the potential of connecting quantum computers using commercial telco optical fibre infrastructure in partnership with Tokyo-based startup LQUOM, which is developing quantum communication systems and related technologies for “the realisation of a quantum internet”. 

For more on the use of quantum technology in the telecom sector, check out TelecomTV’s dedicated quantum technology section. And to find out which companies are regarded as the current leaders in the development and application of quantum-safe networking technologies and services, check out the latest free-to-download DSP Leaders publication, the 14-page Quantum-Safe Networking Market Perception Report. 

- Ray Le Maistre, Editorial Director, TelecomTV