The sub-3GHz spectrum bands are rising in prominence as the whole industry advances in its 5G journey. Innovative upgrades to the network featuring multi-antennas MIMO, ultra-wideband and multi-RAT coordination will be the key to successful 5G evolution.
At the recent Huawei Analyst Summit 2022 held in Shenzhen, Huawei and industry members urged maximal use of ultra-broadband and multi-antenna technologies to accelerate the sub-3GHz to 5G and deliver on user experiences.
Huawei VP of Wireless Network Product Line, Cao Ming, opened the sub 3GHz analyst roundtable. “Sub 3GHz is an important task from resources for 5G, by which more than 650,000 base stations have been deployed worldwide. Sub-3GHz products are commercially used in more than 100 countries. At MWC this year, Huawei was recognized for its creation of a mobile network last year in FDD which became an industry-leading example. It showed the industry recognition of Huawei's leading products and Huawei can't have achieved this without your recognition and support."
“Multi-band, multi-RAT and multi-channel demands more power, however, it is not the right way to increase the power. We think we have to combine the radio capability of hardware, software and AI to get the best performance and energy efficiency. This is the strategic direction for future sub-3GHz evolution.”
Global Mobile Suppliers Association (GSA) president Joe Barrett started the forum, showcasing the pivotal role lower band spectrum is to operators for augmenting the high speed and low bandwidth we associate with 5G.
He highlighted mid and low band frequencies will account for 40% of 5G traffic which is why the industry needs to focus on freeing up spectrum in the lower bands, which will come to a head at the World Radio Communication Conference 2023 (WRC-23).
“That's a key area that we need to focus on. The high bands also need to be producing traffic for the ultra-experiences. But the coverage and capacity layer in the mid-band is also very important, as is a low band for coverage,” said Barrett.
According to GSA data, 92 operators have launched 5G in sub-3GHz bandwidths. Europe is currently the leader in tapping into sub-3GHz airwaves, as 17 operators rolled out on 2.1GHz, 15 in 700MHz, and five at 1.8GHz.
The sub-3GHz ecosystem is also expanding with a “rapid increase” in devices that support all 5G frequencies. Between 1990 and the present there have been 979 devices unveiled and commercialised. Currently, there are 852 devices supporting low bands from 121 vendors, most vitally, 5G devices are becoming more affordable as they dip into the sub $US200 range.
“That really will start to drive the take up of 5G, its services, and the experiences that users are now coming to expect,” said Barrett. “We've got a lot of growth happening in the industry, through bringing devices and networks to market”.
Spotlight is on Sub-3GHz
Huawei’s 3GPP standard senior expert and vice-chair at 3GPP RAN1 David Mazzarese noted key technologies that tap into the use of sub-3GHz spectrum was being standardised in each 3GPP release since 15.
After release 15, “we started approving individual projects and announcements, targeted at specific features in 3GPP”, said Mazzarese, many of which were advocated by Huawei.
This showcases how the industry is starting to recognise the importance of sub-3GHz for 5G evolution, said Mazzarese.
In release 16, we saw technologies pushed such as MIMO (enhanced type 2 codebook), DSS Enhancement and spectrum evolution (RAN4). That continues in release 17 where there were more MIMO announcements for FDD bands, DSS/MR-DC and more spectrum evolution.
Looking ahead to release 18, MIMO will be advanced through multi-cell coherent joint transmission (MC-CJT), multi-carrier enhancements and specific announcements to enable 700 800 900MHz band combinations on smartphones as well as infrastructure gear.
Needed innovation
Huawei is one of the world’s key suppliers of infrastructure equipment which was illustrated at MWC earlier this year, when Huawei won the GLOMO award for best mobile network infrastructure for the second year running, with its New FDD Giga Band MIMO Modules that support low and mid-band Sub-3GHz frequencies in one radio box while implementing 4T4R, 8T8R, and Massive MIMO.
Great technology is supported by great technology and that is certainly the case in the infrastructure space, where when new resources such as spectrum become available, new challenges arise for operators.
This was pointed out by Huawei VP of 5G and LTE FDD Domain Qiu Zheng, who highlighted operators face the usual pressures of providing high download/upload speeds with sufficient coverage. But this is being compounded with much needed carbon neutrality target.
A way through for operators is to expand transceivers and antennas, but this adds weight and space challenges, as well as an increase in energy use which contradicts carbon neutrality targets.
“For Sub-3GHz, the characteristic obviously is a lot of bands, rich bands, for both legacy bands and new bands, but they are fragmented, our ambition is to solve those challenges and problems. I think our whole industry should be together to find the best way to optimise that cost per gigabit.
“The answer for those headaches, comes in two key parts; one is the use of ultra-wideband and the other is multiple antennas,” said Qiu.
Ultra-wideband is a radio technology which uses low energy for short-range but high bandwidth communications over large sections of spectrum. “Power can be shared in between different sub-bands” through the use of this technology, noted Qiu.
The use of multiple antennas enables efficient use of spectrum which brings a host of advantages to operators.
“Multiple antennae can significantly increase spectrum efficiency, it can produce good network performance for example multiplexing, suppress interferences and encourage transceiver diversity,” said Qiu.
“The starting point is 4T4R, especially in lower bands, which is the ubiquitous coverage layer. You then progress to 8T8R or massive MIMO in the mid-band, which is the universal capacity layer. Massive MIMO is the only viable option at higher bands as it combines capacity with great customer experience. We call it the extreme experience layer.”
Success stories
Utilising the right innovative technologies can quickly overturn an operator’s standing which was the case for a Netherlands-based operator who tapped Huawei for solutions.
The unnamed operator possessed less infrastructure footprint and bandwidth compared to rivals, which was evident in testing from industry benchmarkers P3.
To improve on its disadvantage, the operator with Huawei then upgraded its 1T2R dual-band radio units to 4T4R triple-band for sub-1GHz and 2T2R to 8T8R in mid-band. Then through tower upgrades, the operator was able to tap into seven bands using its usual four boxes and coverage was also boosted.
As a result, the company received its best ever P3 network results, not only nationally but also ranked globally, improving from a score of 954 to 962. Its NPS scores also increased by 6% as a result.
Another example is an operator in Finland, which had a similar problem as its Netherlands-based counterpart.
This operator modernised its towers with more advanced boxes, which cut its use of three boxes to two, freeing up space for a massive MIMO to upgrade to 4G and 5G.
Even though there was an upgrade, there was no change to the operator’s energy consumption, Qiu pointed out, despite now tapping into seven bands instead of four.
“The commercial feedback from the market was amazing for this operator because its performance and accountabilities significantly increased. From this upgrade, the operator gained the capability to increase prices and upsell. The average revenue per user then increased 10% year by year.”
One of Germany’s major operator players was also in a less fortunate position with fewer spectrum holdings, huge distances between base stations, and a lower budget.
This operator deployed 8T8R and Blade AAU with C-bands. From these upgrades, this operator saved 30% on the total cost of ownership on its mobile sites, boosted coverage by 40% and user throughput by 30% to 70%.
Overall, this operator bested rivals in customer data performance according to P3 network testing.
In closing the roundtable, Qiu again highlighted how vital it is for the industry to pay close attention to innovations within the sub3-GHz space. Operators who recognise this can take a true evolutionary step into the 5G NR era and push the full potential of their networks, which will, in turn, deliver ubiquitous coverage and high levels of performance.
