Is your RF ready for 5G?

Telecoms.com periodically invites third parties to share their views on the industry’s most pressing issues. In this piece Alexis Mariani, Marketing Specialist at Qorvo, looks at some RF challenges on the road to 5G.

Mobile operators are now able to advance their plans for 5G rollouts thanks to accelerated 5G standards development. Once these rollouts begin, 5G handsets are predicted to become the fastest growing sector of the smartphone industry for the next decade. While 5G is sure to support an extraordinarily broad range of applications, smartphone manufacturers are pressured to add 5G New Radio (NR) support to their handset designs.

RF Challenges on the Road to 5G

As with any major advance in communications technology, the road to 5G is paved with a whole new set of technical RF challenges, including:

  • 5G non-standalone (NSA) adds significant RF complexity because it requires dual 4G LTE and 5G connectivity.
  • Massive MIMO and beam steering will be required in base stations to deliver multi-gigabit data rates.
  • Massive bandwidth and new waveforms will generate very high peak-to-average ratios and a need for high linearity.

5G NSA Dual Connectivity Multiplies RF Interference Challenges

Initial implementation will focus on enhanced mobile broadband (eMBB), which is expected to deliver data rates of up to 20x today’s 4G speeds. This requires new hardware in smartphones and infrastructure in the form of 5G NR. Unlike the previous technology transition from 3G to 4G, it won’t simply be making 4G faster and rebranding it as 5G.

Most initial eMBB deployments in the U.S., and some other countries, will use 5G NSA. This adds significant complexity because it requires dual 4G LTE and 5G connectivity. NSA will continue to present challenges for handset RF design for at least the next decade, until all mobile operators convert to standalone (SA) 5G.

In many cases, operators will be expected to combine 4G bands with a 5G band. The NSA specification allows the handset to simultaneously transmit on one or more LTE bands while receiving on a 5G band.

Higher Bandwidth, New Waveform 

The new 5G waveform, CP-OFDM, provides very high spectral packing efficiency and good MIMO support. However, the higher peak-to-average power ratios (PAR), together with massive bandwidth, require greater PA output backoff to stay within regulatory limits and maintain linearity. This potentially reduces the efficiency of the transmit (Tx) chain and creates a challenging high linear power requirement for PA design.

The first phase of 3GPP Release 15, delivered in December 2017, included the initial set of 5G NR specifications. They focus on mobile broadband deployment using the NSA 5G NR—the technology that will be used initially for early 5G network rollouts. By using an LTE anchor band for control with a 5G NR band for faster data rates, operators will be able to deliver 5G speeds sooner.

The 5G SA specifications, which remove the need for an LTE anchor, are still in progress. Although Release 15 will be completed later this year, 5G specifications will continue to evolve for years to come, further complicating things.

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