The Graduate School of Engineering, the University of Tokyo (located in Bunkyo-ku, Tokyo; Dean Yasuhiro Kato, Professor Akihiro Nakao, Nakao Laboratory, hereinafter "The University of Tokyo") and Murata Manufacturing Co., Ltd. (Headquarters: Nagaokakyo City, Kyoto Prefecture; President and CEO Norio Nakajima, hereinafter "Murata Manufacturing"), based on a joint research agreement between the two parties, have developed a local 5G mmWave base station (Figure 1) by integrating software-defined radio (SDR) technology (Note 1) with a mmWave communication module (Note 2). This system successfully established communication with commercially available local 5G mmWave-compatible terminals on May 22, 2025.
In an evaluation of this system, a throughput performance of 300 Mbps in the downlink and 70 Mbps in the uplink was confirmed using band n257 (bandwidth 100 MHz). In addition, a practical throughput performance was confirmed when changing the beam angle using the beamforming function (Note 3), which is essential for mmWave communication. In the future, this research plan to introduce software that will dynamically control the beam angle, with the aim of realizing a small, inexpensive mmWave compatible base station.
Announcement contents：
5G mmWave communication has been in service since 2020, but its actual usage rate in communication remains low at 0.2% (Note 4). The reasons for its slow spread include the insufficient number of base stations installed, the small available area, and the fact that there are still few 5G terminals that support mmWaves.
Due to the inherent propagation limitations of mmWaves, their practical use has remained limited despite the growing availability of compatible terminals, largely due to insufficient base station deployment.
In addition, conventional 5G mmWave compatible base stations are large and expensive, and there were cost issues in terms of deploying a large number of them.
The Nakao Laboratory at the University of Tokyo has previously developed small local 5G base stations using SDR, but the frequency band was previously limited to Sub6 and did not include mmWave support. On the other hand, Murata Manufacturing has developed a communication module that supports the mmWave band, but performance evaluation as a base station has not been conducted. Therefore, the two companies have signed a joint research agreement and are promoting joint evaluation to realize mmWave base stations. (Figure 2)
〈Results〉
・Successful development of a local 5G mmWave base station integrating SDR with a mmWave module.
In an evaluation using band n257 (100MHz bandwidth), good throughput performance of 300Mbps downlink and 70Mbps uplink was confirmed. The SDR used this time can support up to 100MHz bandwidth, but Future upgrades to equipment supporting 400MHz bandwidth are expected to achieve downlink throughput performance up to 1.2Gbps.
Figure 2: Actual communication evaluation in the anechoic chamber (8.6m x 4.3m) at the Tokyo Metropolitan Industrial Technology Research Center
・Confirmed connection with commercially available local 5G mmWave-compatible terminals (UE)
This reserch verified mmWave connections with multiple local 5G mmWave-compatible UEs (confirmed with Samsung Galaxy S22, Kyocera K5G-C-100A, NETGEAR MR6550) and confirmed that good throughput performance could be achieved with all terminals.
・Demonstration evaluation using beamforming function
Using beamforming technology, which is essential for mmWave communication, this reserch evaluated beam adjustments horizontally and vertically, collecting key performance indicators (RSRP, SINR, RSRQ, CQI, MCS, BLER, and throughput).(Figure 3)
Figure 3: Changes in communication index data when beam angles are changed horizontally and vertically (heat map display)
・Evaluation of horizontal and vertical beam switching
As a result of the beamforming evaluation, it was confirmed that if the beam angle is changed within ±20 degrees, even at the beam boundary, the throughput characteristic is kept approximately 100Mbps.This result confirmed that a simple beam switching setting with less frequent beam control can be used practically.
・Demonstration of TDD (Time Division Duplex) operation
Two mmWave modules were used in the beamforming evaluation, and good performance was also confirmed with TDD operation using one mmWave module. In the TDD evaluation, a throughput performance of 270Mbps downstream and 30Mbps upstream was confirmed in band n257 (100MHz bandwidth).
〈Future plans〉
The current evaluations have utilized static beam adjustments for mmWave communication. Future work will focus on implementing dynamic beam angle control between base stations and terminals.
In addition, this research group aim to integrate the knowledge of beamforming settings obtained from the evaluation in this study into the control software on the base station side and realize a practical local 5G mmWave base station that enables dynamic beam angle control. This is expected to lead to the spread of small, inexpensive local 5G mmWave-compatible base stations.
Terminology：
(Note 1) Software-defined radio technology: Technology that allows the functionality of wireless communication systems to be flexibly customized using software, without changing the hardware.
(Note 2) Millimeter-wave communication module: A small electronic component that provides communication functionality at frequencies generally above 24 GHz.
(Note 3) Beamforming function: Technology that changes the beam direction of a signal by controlling the signal phase.
(Note 4) See the handout from the Ministry of Internal Affairs and Communications' 5G Business Design Working Group (3rd meeting).