In a video interview, Fujitsu’s Femi Adeyemi talks with 5G Technology world about the company’s 5G radios and the Telecom Infrastructure Project.
While most of the 5G talk surrounding Open RAN focuses on the digital baseband, those digital data streams come from and go to the radio. Fujitsu Network Communications has developed two 5G radios for Open RAN. These radios are now part of the Telecom Infra Project (TIP).
Found on the TIP Marketplace, the dual-band radio unit (RU) covers bands 66 and 70 while a triple-band radio covers bands 26, 29, and 71. These 5G frequency bands generally cover 5G low-band frequencies 600 MHz, 700 MHz, and mid-band frequencies around 2 GHz.
The Fujitsu radios use what’s called the 7.2 Functional Split (Figure 1), which places the RF circuits and the low-PHY (layer 1) functions at the radio. The high PHY functions reside in the RAN’s distribution unit (DU).
Figure 1. The 7.2 functional split places the high PHY functions in the distributed unit, leaving RF and low-PHY functions at the radio.
In the video, Fujitsu’s Femi Adeyemi explains how the functional split and the RAN disaggregation RAN lets operators choose where to locate a DU with respect to an RU. That provides a flexibility not available with aggregated baseband units (BBUs). For example, moving most BBU functions to the DU, as in the 7.2 split, minimizes the real estate needed at a tower site. The choice of RU-to-DU distance comes down to latency. Keeping the DU close minimizes latency but restricts the DU’s location options.
Adeyemi also how the radios are preconfigured with respect to RF beams. That is, they can support up to four beams, but the beams don’t move with the user. The radios can also drive omnidirectional antennas. Given the relatively low frequencies that the radio support, beam steering is generally not needed in the way it’s needed at higher frequencies, especially mmWave.
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