Summary Bullets:
• Operators want 6G migration to be more software-centric and require less expensive radio installation than 5G.
• Stakeholders developing industry standards for 6G are making progress toward such goals.
Mobile operators want 6G networks to be much more software-centric than 5G, capable of being upgraded via software downloads as much as possible. There are a few problems with that notion. One is that 6G will likely require new spectrum to expand network capacity, and another is that much of the research and development already being directed at 6G is hardware-related. A third is that achieving a much more software-centric mobile network would probably require operators to significantly overhaul their networks, migrating toward virtual radio access network (vRAN) architectures and thus incurring the kind of costly, sweeping rollouts they would rather avoid.
However, progress is being made in this area. Industry members working on 6G standards, including chipmaker Qualcomm, say they are working hard to prioritize enhancing the use of existing frequency bands in 6G to reduce the importance of new spectrum. Qualcomm says it expects 6G to be able to deliver 50-70% coverage/capacity gains without the need to replace cell-site radios. The gains will be higher in frequency-division (FDD) spectrum than in time-division (TDD) spectrum (50-70% for the former, which is typically used for wide coverage using low frequencies; 40-60% for the latter, which is typically used for high capacity using higher frequencies).
It will be achieved, according to Qualcomm, using a combination of software-based technologies, including:
• Spectrum confinement & numerology alignment, including tighter coordination between FDD and TDD spectrum use.
• Downlink MIMO, with advanced channel state feedback to improve beamforming performance.
• Uplink antenna/transceiver power management, accounting for uplink/downlink asymmetry and using maximum permission exposure (MPE) features.
• Modulation, coding and MIMO mapping, with low-density parity checking and constellation shaping.
• Uplink waveform designs using discrete Fourier transform spread (DFT-S) with MIMO to achieve gains over 5G single-layer DFT-S uplink.
• Reference signal and hybrid ARQ designs combining the best aspects of LTE cell-specific reference signals and 5G demodulation reference signals.
These technologies, just a small subset of 6G capabilities now in development, are expected to be implemented mainly via distributed units, the more latency-sensitive, cell-site version of a virtualized baseband unit – which again brings to mind the need for operators to significantly deploy vRAN – which many operators have been reluctant to do at scale and which some major RAN vendors have been reluctant to enable.
Operators likely won’t be able to meaningfully roll out 6G without replacing or upgrading radios. But the technological advancements being made today and in the near term may help significantly reduce the pain and expense that operators experienced while delivering 5G.