Intelligence Brief: Why are CA and DSS key to 5G? – Mobile World Live

Intelligence Brief: Why are CA and DSS key to 5G?

18 DEC 2019

The tricky relationship between operators and mobile spectrum is nothing new. For the past 20 years we’ve seen countless auctions and bandwidth assignments across the globe, often surrounded by much wailing and gnashing of teeth from the operators over the cost, division of the bands and any perceived advantage for the competition.

The spectrum issue typically comes to a head around the launch of a new generation of mobile network technology, as operators feel the pressure to secure fresh licences to maintain a competitive advantage. In the long term, a lot of 5G rollouts will ultimately rely on the availability of fresh spectrum, particularly in the low- and mid-bands. But, in the meantime, operators can also look to technologies including carrier aggregation (CA) and dynamic spectrum sharing (DSS) to manage their 5G network assets.

Auctions in 2020 will see 5G snowball
As with previous generations of mobile technology, the speed of 5G rollout will largely be dependent on the availability of suitable spectrum. It’s no surprise, then, that the next-generation forerunners such as South Korea and the US are those where 5G bandwidth has been available for over a year now. And a number of major auctions are expected within the next six months, with new spectrum specifically earmarked for the technology in 27 markets as of Q3 2019. There’s already considerable excitement about the recently launched sale of C band spectrum in the US, while China is poised for massive expansion in rollouts in 2020, aided by spectrum assigned without cost to the carriers.

In Europe, the case is less clear. We’ve seen been some unexpectedly high bidding in early 5G auctions, and operators in the region risk being squeezed if governments prioritise revenue over rollouts.

The bandwidth issue: coverage versus capacity
For perhaps the first time, the focus on 5G spectrum is shifting from network coverage capabilities to data capacity. The disparity between bands was a factor in 4G, but is set to become core to the 5G consumer experience. The mobile spectrum bands in use today can be divided into three tiers:

  • Low-band: <1GHz
  • Mid-band: 1GHz to 6GHz
  • High-band: >6 GHz

At the recent ITU WRC-19 conference, delegates identified more than 15GHz of fresh high-band mmWave frequency bands suitable for 5G use. These are needed because ultra-low latency and very high bit-rate applications will require larger contiguous blocks of spectrum than those available in lower frequency bands.

In the US, early 5G networks have been built using the 26GHz and 28GHz mmWave frequencies, offering very high capacity but poor coverage: acceptable for dense urban areas, but increasingly problematic as you move out into the suburbs. Increasingly, the speed of 5G rollout will be dependent on the availability of mid- and low-band spectrum.

The lower the frequency of a band, the better the coverage, but spectrum in the sub-1GHz bands is in scarce supply. In 4G, low-band frequencies have been used to cover huge areas, but many operators have gained an edge in urban areas using the mid-band. And this pattern is already emerging in the 5G world, with the majority of existing 5G networks using mid-band in initial urban deployments.

But even the mid-band frequencies may not be sufficient to bring 5G to the masses. Network propagation in these bands is limited, while in-building penetration is relatively weak. To complete 5G, operators will need to begin to utilise low-band spectrum, which will almost inevitably mean refarming.

Make do and mend: the importance of refarming
So why can’t operators simply re-use old spectrum from obsolete networks?

Operators face a fairly unique challenge in this technology generation, since the worlds of 3G and even 2G are far from dead. Huge volumes of connected devices, from industrial IoT to emergency services, are still using 2G networks.

Meanwhile, as 4G migration gathers pace a number of operators are already talking about switching off 3G, potentially freeing up valuable low-band spectrum for refarming to 5G.

GSMA Intelligence’s Network Transformation 2020 report found only a third of operators (31 per cent) identified spectrum refarming as a top-three RAN priority despite many of the same operators highlighting spectrum scarcity as a key barrier to 5G rollout. This low focus on refarming, particularly in Europe and the Americas, seems at odds with many operators’ future plans, given that half of those we surveyed said they plan to phase out their 2G networks by the end of 2020.

Managing spectrum assets to maximise the future of 5G
The widespread rollout of 5G using mmWave spectrum is not realistic: the very limited coverage of these frequencies demands enormous infrastructure investment. At the same time, there is simply not enough mid- and low-band spectrum currently available to provide the huge data capacity 5G will require. But there are some short-term solutions to these challenges which will allow operators to better manage their network assets.

The first is CA, a technology which allows operators to deploy 5G using two or more bands in tandem, integrated together as one big block. This will enable operators to deploy a high level blanket of 5G using mid-band, while adding capacity in dense urban areas using mmWave.

The second technology is DSS. This emerging technology allows 4G and 5G to exist simultaneously on the same band, while adjusting the bandwidth allocated to each generation dependent on demand. This is clearly ideal for low-band rollout, as it will allow operators to continue to use valuable spectrum for 4G, while adding 5G capacity as demand grows. But whether it will be enough to address the looming issue of massive data demand on 5G networks remains to be seen.

Operators can also look to existing models to speed up 5G rollout, such as tower, infrastructure and spectrum sharing. But in the longer term, only the harmonisation of spectrum in the low- and mid-bands will unlock the true potential of 5G. And with the majority of the hyped killer use cases including low latency gaming, VR/AR and automation reliant on standalone networks, there remains a big question over how soon operators can begin recouping the massive investment needed.

But it’s clear from the operators that a perceived scarcity of 5G-suitable radio waves is a barrier to 5G rollout, and governments and regulators must work with the industry to remove spectrum roadblocks if they are to make widespread 5G connectivity a reality.

– Peter Boyland – lead analyst, Ecosystem Research – GSMA Intelligence

The editorial views expressed in this article are solely those of the author and will not necessarily reflect the views of the GSMA, its Members or Associate Members.

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