Optimising base station settings improves data transmission

SoftBank has conducted a proof-of-concept experiment in Tokyo using an Ising machine, a type of quantum computing technology, to optimise radio base station settings. As a result, in 5G communications using carrier aggregation (CA), the company successfully improved downlink data speed by approximately 10% and increased data transmission capacity by up to 50% compared to conventional settings.

SoftBank aimed to expand the coverage area of CA by optimising base station settings using quantum computing technology. CA is a technology that enables high-speed, stable communication by simultaneously utilising multiple frequency bands. To function, it requires predefined associations between base stations, referred to as ‘CA links’. However, 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 (2⁴⁵). 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 maximises CA-enabled area coverage.

In SoftBank’s experiment, an area of Tokyo with multiple 5G base stations was divided 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. To perform this computation, the problem was formulated as a mathematical optimisation problem and solved using an Ising machine, which is specifically designed to perform computations specialised for combinatorial optimisation.

Figure 1: Optimisation of CA link configuration to maximise the number of CA-capable meshes.

Based on the results of the optimisation, a CA link configuration was generated and used to simulate the CA-capable coverage area. The simulation confirmed that CA could be made available over a broader area compared to conventional configurations.

Figure 2: Example of CA-capable coverage before and after optimisation (blue mesh cells indicate CA-capable areas).

When this configuration was applied to 5G base stations operating in a specific area of Tokyo, the CA coverage area expanded and the average downlink data speed improved by approximately 10%. In addition, both the CA utilisation ratio (the proportion of connections utilising CA) and the amount of data transmitted via secondary cells increased by up to 50%.

Figure 3: Average downlink data speed improved by approximately 10%.

Figure 4: Data volume increase in secondary cells (total data volume for secondary cells before and after applying the optimised CA configuration).

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.

Going forward, SoftBank 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 and deliver even more seamless and high-quality services.

Top image credit: iStock.com/Vertigo3d