Optus and Nokia run a 25 MHz downlink with a 20 MHz uplink in 900 MHz 5G

Optus and Nokia have run a 5G NR carrier in Optus’s 900 MHz spectrum with a 25 MHz downlink and a 20 MHz uplink. The companies call it a world first on a live network. The test took place in the Australian Capital Territory with a commercial OPPO Find X10 Pro Max phone using a new MediaTek chipset. According to Optus, download speeds rose by up to 91% outdoors and 51% indoors compared with the existing network configuration, because the phone could use the full 25 MHz downlink channel. The release gives relative gains only, and no date for commercial use.

The 900 MHz spectrum is NR band n8, with uplink at 880 to 915 MHz and downlink at 925 to 960 MHz in 3GPP TS 38.101-1. That specification also defines asymmetric uplink and downlink channel bandwidths for some FDD bands, and requires the narrower carrier to sit within the frequency range of the wider one. In the Release 19 version (V19.7.0), a 20 MHz uplink with a 25 MHz downlink on n8 appears in bandwidth combination sets 1 and 2. The specification makes only set 0 mandatory for phones where a band defines it, so this pairing depends on the handset declaring support. That fits the need for a new chipset.

Optus says about 15% of its urban connections and 35% of its rural connections rely mainly on low-band spectrum.

Why it matters

Low-band carriers are narrow, and most traffic is downlink, so an extra 5 MHz of downlink on a 20 MHz uplink is a meaningful gain where 900 MHz is the only signal reaching a user. Two cautions apply. The uplink stays at 20 MHz, so the cell-edge uplink budget is unchanged, and uplink is often the limiting direction at the edge of a low-band cell. The release does not describe the baseline configuration, so the reported gains cannot be split between the wider channel and other changes. Only phones that support the combination benefit.