Low Latency Power Saving with Low Power-Wake Up Signal/Receiver (LP-WUS/LP-WUR)

Power-saving methodologies have been integral to all generations of 3GPP technologies, aimed at reducing the power consumption of user equipment (UEs) and other battery-dependent devices. Some of the stringent requirements of 5G, such as achieving a 10-year battery life for certain IoT devices, have necessitated further optimisation of power consumption. To address this, 3GPP Release 16 introduced the Wake-Up Signal (WUS) power-saving mechanism, designed to significantly reduce energy usage in UEs. For a detailed technical explanation, ShareTechnote provides an excellent overview.

The concept of wake-up radios has been explored for over a decade. In a 2017 blog post, Ericsson highlighted how researchers had been working on designing wake-up radios and receivers, initially aimed at IEEE 802.11 (Wi-Fi) technologies. This idea later gained traction in 3GPP discussions, culminating in a study conducted during Release 18. The findings are comprehensively documented in 3GPP TR 38.869: Study on low-power wake-up signal and receiver for NR (Release 18).

Quoting from the introduction of 3GPP 38.869:

5G systems are designed and developed targeting for both mobile telephony and vertical use cases. Besides latency, reliability, and availability, UE energy efficiency is also critical to 5G. Currently, 5G devices may have to be recharged per week or day, depending on individual's usage time. In general, 5G devices consume tens of milliwatts in RRC idle/inactive state and hundreds of milliwatts in RRC connected state. Designs to prolong battery life is a necessity for improving energy efficiency as well as for better user experience. 

Energy efficiency is even more critical for UEs without a continuous energy source, e.g., UEs using small rechargeable and single coin cell batteries. Among vertical use cases, sensors and actuators are deployed extensively for monitoring, measuring, charging, etc. Generally, their batteries are not rechargeable and expected to last at least few years as described in TR 38.875. Wearables include smart watches, rings, eHealth related devices, and medical monitoring devices. With typical battery capacity, it is challenging to sustain up to 1-2 weeks as required. 

The power consumption depends on the configured length of wake-up periods, e.g., paging cycle. To meet the battery life requirements above, eDRX cycle with large value is expected to be used, resulting in high latency, which is not suitable for such services with requirements of both long battery life and low latency. For example, in fire detection and extinguishment use case, fire shutters shall be closed and fire sprinklers shall be turned on by the actuators within 1 to 2 seconds from the time the fire is detected by sensors, long eDRX cycle cannot meet the delay requirements. eDRX is apparently not suitable for latency-critical use cases. Thus, the intention is to study ultra-low power mechanism that can support low latency in Rel-18, e.g. lower than eDRX latency.

Currently, UEs need to periodically wake up once per DRX cycle, which dominates the power consumption in periods with no signalling or data traffic. If UEs are able to wake up only when they are triggered, e.g., paging, power consumption could be dramatically reduced. This can be achieved by using a wake-up signal to trigger the main radio and a separate receiver which has the ability to monitor wake-up signal with ultra-low power consumption. Main radio works for data transmission and reception, which can be turned off or set to deep sleep unless it is turned on.

The power consumption for monitoring wake-up signal depends on the wake-up signal design and the hardware module of the wake-up receiver used for signal detecting and processing. 

The study should primarily target low-power WUS/WUR for power-sensitive, small form-factor devices including IoT use cases (such as industrial sensors, controllers) and wearables. Other use cases are not precluded, e.g.XR/smart glasses, smart phones. 

As opposed to the work on UE power savings in previous releases, this study will not require existing signals to be used as WUS. All WUS solutions identified shall be able to operate in a cell supporting legacy UEs. Solutions should target substantial gains compared to the existing Rel-15/16/17 UE power saving mechanisms. Other aspects such as detection performance, coverage, UE complexity, should be covered by the evaluation.

The Bridge Toward 6G: 5G-Advanced Evolution in 3GPP Release 19 by Xingqin Lin, @NVIDIA - https://t.co/O1d8jnB9MY#Free5Gtraining #3G4G5G #3GPP #5G #5GAdvanced #6G #AIML #NGRAN #XR #UAV #LPWUS #LPWUR #HighPerforming #LTM #SBFD #Femtocell #NTN #WAB #Relay pic.twitter.com/aSC9FuruC7

— Free 5G Training (@5Gtraining) January 2, 2024

Qualcomm's blog post looking at 'How will wireless innovations foster a greener, more sustainable future?' is also worth reading on this topic.

Related Posts: 

• The 3G4G Blog: 3GPP TSG RAN and TSG SA Release-19 Workshop Summary
• The 3G4G Blog: ETSI's Summit on Sustainability: ICT Standards for a Greener World
• The 3G4G Blog: Four Ways 5G Can Improve the Battery Life of User Equipment (UE)
• The 3G4G Blog: Energy Consumption in Mobile Networks and RAN Power Saving Schemes
• The 3G4G Blog: Reducing 5G Device Power Consumption Using Connected-mode Discontinuous Reception (C-DRX)
• The 3G4G Blog: Mobile Initiated Connection Only (MICO) mode in 5G System 

ETSI's Summit on Sustainability: ICT Standards for a Greener World

The ETSI Summit on Sustainability - How ICT developments and standards can enable sustainability and have a positive impact on society, took place on 30 March 2023 and focused on the key role of the ICT industry and related standardization activities to support Green initiatives. The event brought a large and global audience of over 220 stakeholders including operators, solution providers, policy makers and standards bodies or fora working on the topic.

A multitude of presentations including two interactive panel sessions, rhythmed the day and succeeded to make it a highly interactive Summit, pointing out challenges and how ICT can be both the problem and the solution.

The opening session examined the sustainability challenges and global green initiatives from numerous global standards bodies and fora. One of the suggested actions was to adopt ESG (Environmental Social Governance) goals as an integral part of the company’s objectives. Another highlight from the session was the need for standards work on the measuring and reporting of “avoided emissions,” that is being covered by ongoing work in ETSI. Feedback from the audience pointed out that it would be beneficial to further investigate the balance of ICT deployments vs real needs. Do we really need to endlessly deploy new technologies, when exiting ones serve the need?

The following are presentations from the welcome address and session 1:

• Welcome Address by Luis Jorge Romero, Director General, ETSI
• SESSION 01 - The Sustainability Challenge and Global Green Initiatives chaired by Bettina Funk, ETSI GA Chair: The session examines several regional and global initiatives working on sustainability and seeks to identify synergies and areas of cooperation.
• Some Standardization Needs for Green Digital Twin Transition by Emilio Davila Gonzalez, European Commission
• ITU Sustainability & Working with ETSI by Dominique Wurges, ITU-T SG5  
• IEC Sustainability & Working with ETSI by Alfonso Sturchio, IEC TC111 
• ISO/IEC/JTC1 Sustainability & Working with ETSI by Thomas Wegmann, Liaison officer ISO/IEC JTC 1/SC 39
• The work of GeSI toward Energy Efficiency (and other sustainable technologies) by Luis Neves, GeSi
• Green Future Networks by Anita Doehler, NGMN Alliance

The second session focused on the role of ICT in sustainability and was animated by two panels. The first one addressed the operators’ objectives and their plans for sustainability. The second one dealt with various initiatives being taken by solutions providers to meet the needs expressed by the operators and society as a whole. Suggested actions emerging from the debate included putting sustainability criteria in the procurement phase towards the vendors and enhance collaboration between operators, to share their common requirements and provide them to the supply chain ecosystem. In an animated exchange between the Panellists and the audience it was highlighted that there is an urgent need to reduce energy consumption, extend the lifecycles of ICT equipment and systematically recycle and repurpose in order to reduce ICT waste.

The following are presentations from session 2:

• Session 02 - The Role of ICT in Sustainability: The session comprises two interactive panel sessions examining 1) Operators objectives and plans for Sustainability and 2) several initiatives being taken by solutions providers to meet those objectives. Session Chaired by David Boswarthick, ETSI
• Operators Panel Moderated by Anita Dohler, NGMN Alliance e.V.: The purpose of this panel is to examine what are the sustainability plans, challenges & priorities for Operators
• Saima Ansari, Deutsche Telekom
• P. Balaji, Vodafone Idea
• Marc Grant, AT&T
• Luca Pesando, TIM
• Solution Providers Panel Moderated by Joe Barrett, GSA, Global Mobile Suppliers Association - The purpose is to examine what the current solutions and remaining challenges on Sustainability are.
• Howard Benn, Samsung
• Raffaele Bolla, 6Green Project
• Ralf Bucksch, IBM
• Susanna Kallio, Nokia

The afternoon opened with an  overview of ETSI, 3GPP and oneM2M activities supporting technologies for sustainability. One of the presentations highlighted that ICT should initially focus its own environmental impacts and consider digital sobriety as it is recognized that the cleanest energy is the one that is not consumed.

The following are presentations from session 3:

• Session 03 - ETSI Activities Supporting Technologies for Sustainability Chaired by Nick Sampson, ETSI OCG Chair: This session will present the sustainability standards work that is ongoing in ETSI and our Partnership Projects oneM2M and 3GPP.
• TC EE’s Approach to Sustainability by Benjamino Gorini, TC EE Chair 
• The Work of TC ATTM and OEU for Green and Sustainable Networks and Cities by Lynn Reiner. TC ATTM TM6 Chair
• 3GPP’s Approach to Energy Efficiency by Jean-Michel Cornily, Rapporteur for 3GPP EE work items
• oneM2M Work on IoT for Sustainability by Dale Seed, Chair oneM2M SSC 

The summit concluded with a dynamic exchange around what more telecoms can do to move forward in the right direction. ICT and specifically data centres create a significant carbon footprint, and there was a call to use the ISO Net Zero guidelines in order to develop sustainable strategies. The industry should adopt an eco-design (sustainability by design) approach and seek to have products that are energy efficient, with longer life cycles, recyclable and repairable.

The following are presentations from session 4:

• Session 04 - What More Can Telecoms Do to Ensure Global Sustainability Targets are Reached? Chaired by Dirk Weiler, ETSI Board Chair: This session will address alternative perspectives on the principle challenges and gaps that need to be urgently addressed. What more can be done, both in ETSI and beyond, and what could be future directions/actions for the industry?
• Environmental Impact of ICT – Data Centers by Bruno Lafitte, ADEME
• ISO Net Zero Guidelines – a Global Basis for Net Zero Action by Emily Faint, BSI
• ECOS: Driving Environmentally Friendly Standards, Policies and Laws by Mathieu Rama, ECOS

As a conclusion it was agreed that ICT is part of the sustainability problem and must seek to reduce its own emissions, whilst at the same time ICT is certainly part of the solution and should be applied to other domains in order to help them reach their own sustainability goals. As a first step, making ICT more sustainable should be the #01 priority for the industry today and ETSI groups TC EE (environmental engineering), TC ATTM (access, terminal and multiplexing) and ISG OEU (operational energy efficiency for users) are currently providing the standards to enable this transition to greener digital technologies.

Event Wrap-Up / Conclusions is available here.

Should you wish to learn more about the summit, all of the presentations including the conclusion slides are available here.

Related Posts: 

• The 3G4G Blog: Energy Consumption in Mobile Networks and RAN Power Saving Schemes
• Free 6G Training: Technology Enablers for Spectrum & Energy Efficient 6G Wireless Access
• The 3G4G Blog: Reducing 5G Device Power Consumption Using Connected-mode Discontinuous Reception (C-DRX)
• Free 6G Training: Sustainability as an Integral Part of 6G System Architecture Design
• Free 6G Training: 6G Flagship Webinar on 'Green Networking in B5G'
• Free 6G Training: AT&T Wants a Sustainable and Affordable 6G 

Four Ways 5G Can Improve the Battery Life of User Equipment (UE)

We have looked at different approaches in this blog and the 3G4G website on reducing the power consumption (see related posts below). In a blog post some months back, Huawei highlighted how 5G can improve the battery life of UE. The blog post mentioned four approaches, we have looked at three of them on various blogs. 

The following is from the blog post:

RRC_INACTIVE State

A UE can access network services only if it establishes a radio resource control (RRC) connection with the base station. In legacy RATs, a UE is either in the RRC_CONNECTED state (it has an RRC connection) or the RRC_IDLE state (it does not have an RRC connection). However, transitioning from the RRC_IDLE state to the RRC_CONNECTED state takes a long time, so it cannot meet the low latency requirement of some 5G services. But a UE cannot just stay in the RRC_CONNECTED state because this will consume much more UE power.

To solve this problem, 5G introduces the RRC_INACTIVE state, where the RRC connection is released but the UE context is retained (called RRC Release with Suspend), so an RRC connection can be quickly resumed when needed. This way, a UE in the RRC_INACTIVE state can access low-latency services whenever needed but consume the same amount of power as it does in the RRC_IDLE state.

DRX + WUS

Discontinuous reception (DRX) enables a UE in the RRC_CONNECTED state to periodically, instead of constantly, monitor the physical downlink control channel (PDCCH) to save power. To meet the requirements of different UE services, both short and long DRX cycles can be configured for a UE. However, when to wake up is determined by the predefined cycle, so the UE might wake up unnecessarily when there is no data scheduled.

Is there a way for a UE to wake up only when it needs to? Wake-up Signal (WUS) proposed in Release 16 is the answer. This signal can be sent before the next On Duration period (during which the UE monitors the PDCCH) so that the UE wakes up only when it receives this signal from the network. Because the length of a WUS is shorter than the On Duration Timer, using WUS to wake up a UE saves more power than using only DRX.

BWP Adaptation

In theory, working on a larger bandwidth consumes more UE power. 5G provides large bandwidths, but it is unnecessary for a UE to always work on large bandwidth. For example, if you play online mobile games on a UE, only 10 MHz of bandwidth is needed for 87% of the data transmission time. As such, Bandwidth Part (BWP) is proposed in 5G to enable UEs to work on narrower bandwidths without sacrificing user experience.

BWP adaptation enables the base station to dynamically switch between BWPs based on the UE’s traffic volume. When the traffic volume is large, a UE can work on a wide BWP, and when the traffic volume is small, the UE can work on a narrow one. BWP switching can be performed based on the downlink control information (DCI) and RRC reconfiguration messages. This ensures that a UE always works on a bandwidth that supports the traffic volume but does not consume too much power.

Maximum MIMO Layers Reduction

According to 3GPP specifications, the number of receive and transmit antennas used by a UE cannot be fewer than the maximum number of MIMO layers in the downlink and uplink, respectively. For example, when a maximum of four downlink MIMO layers are configured for a UE, the UE must enable at least four receive antennas to receive data. Therefore, if the maximum number of MIMO layers can be reduced, the UE does not have to activate as many antennas, reducing power consumption.

This can be achieved in 5G because the number of MIMO layers can be re-configured based on assistance information from UEs. After receiving a request to reduce the number of MIMO layers from a UE, the base station configures fewer MIMO layers for the UE through an RRC reconfiguration message. In this way, the UE can deactivate some antennas to save power.

T-Mobile added more cell sleep profiles (or this is just the first time i noticed it). L2100 is now turned off at night when the cell load is low. After 6am it's back on everywhere. When you load the cell it will also come back online.

Pretty significant reduction of power use. pic.twitter.com/oDYhyLeQLw

— Jeffrey | Antennekaart.nl (@antennekaart) September 26, 2022

Power consumption in the networks and the devices is a real challenge. While the battery capacity and charging speeds are increasing, it is also important to find ways to optimise the signalling parameters, etc. One such approach can be seen in the tweet above regarding regarding T-Mobile in The Netherlands, selectively switching off a carrier in the night and switching it back when the cell starts loading or in the morning.

We will see lot more innovations and optimisations to dynamically update the technologies, parameters, optimisations to ensure power savings wherever possible.

Related Posts: 

• 3G4G: What is a User Equipment (UE)?
• The 3G4G Blog: A Technical Introduction to 5G NR RRC Inactive State
• Connectivity Technology Blog: InterDigital’s 6G Vision of “Zero-energy” (ZE) air-interface designs
• The 3G4G Blog: Bandwidth Part (BWP) in 5G New Radio (NR)
• Telecoms Infrastructure Blog: Huawei Explains Antennas and Radomes
• The 3G4G Blog: What is RF Front-End (RFFE) and why is it so Important?
• The 3G4G Blog: Reducing 5G Device Power Consumption Using Connected-mode Discontinuous Reception (C-DRX)
• The 3G4G Blog: Energy Consumption in Mobile Networks and RAN Power Saving Schemes
• The 3G4G Blog: Smartphone Batteries Round-up: Technology, Charging & Recycling
• The 3G4G Blog: The Futuristic Concept of 'Smart & Intelligent' Batteries 

What is RF Front-End (RFFE) and why is it so Important?

As more technologies, frequency bands, antennas, etc., are crammed in our smartphones and tablets, it becomes essential for these devices to keep performing despite what technologies and spectrum are in use at any instant of time. This requires specialist design of the RF front end in our devices. Wikipedia explains it as:

In a radio receiver circuit, the RF front end, short for radio frequency front end, is a generic term for all the circuitry between a receiver's antenna input up to and including the mixer stage. It consists of all the components in the receiver that process the signal at the original incoming radio frequency (RF), before it is converted to a lower intermediate frequency (IF). In microwave and satellite receivers it is often called the low-noise block downconverter (LNB) and is often located at the antenna, so that the signal from the antenna can be transferred to the rest of the receiver at the more easily handled intermediate frequency.

🔸RFFE revenues should also grow at a rapid clip with proliferation of 5G & 5G mmWave in coming years
🔸 The RF Semi $ content per device will rise and drive the RFFE segment.
🔸 Will be interesting to see if Qualcomm can get more design wins at Apple over next two yr window. pic.twitter.com/9hKrQYpwI4

— Neil Shah (@neiltwitz) July 29, 2021

Qualcomm is very active in this area as can be seen from the chart in the Tweet above. Back in October, Qualcomm announced ultraBAW, their new generation of micro acoustic filter technology that expands their RF front-end (RFFE) portfolio and opens up new 5G services and applications. They have a short intro video explaining RFFE:

Apple bought ~$14 billion worth of baseband, RF front-end (RFFE) and connectivity chips from Broadcom, Qorvo, Qualcomm and Skyworks in 2021.

That means ~$55 worth of baseband + RFFE + connectivity content per iPhone.$AVGO $QCOM $QRVO $SWKS

— Sravan Kundojjala (@SKundojjala) December 18, 2021

It is also interesting to see from the Tweet above that on an average baseband + RFFE + connectivity chips cost Apple nearly $55 per device.

The analyst firm CCS Insight have also done some good work explaining RFFE and their analyst Wayne Lam has written a few detailed articles on this topic. Here are the links if you want to read further:

• Advances in RF Front-Ends Made 5G Phones Possible (link)
• Advances in 5G RF Front-Ends Lead to Longer Battery Life (link)

Their RFFE videos playlist is embedded below.

Also worth noting that a good modem and RF front-end, especially with 5G, can make a lot of difference in what speeds and coverage you can get

Sometimes I forget the value of having a good modem and RF front-end having an S21 Ultra and then I compare my mid-band coverage on @TMobile to people next to me with an iPhone 13 and Pixel 5 and they don't get remotely the same speeds or coverage.

— Anshel Sag (@anshelsag) December 26, 2021

Related Posts:

• Telecoms Infrastructure Blog: Open RAN (O-RAN) RRU (O-RU) and DU (O-DU) Design
• The 3G4G Blog - Radio Design Webinar: Optimising Your 700 MHz Deployments
• The 3G4G Blog: Envelope Tracking for improving PA efficiency of mobile devices 

Energy Consumption in Mobile Networks and RAN Power Saving Schemes

We just made a tutorial on this topic looking at where most of the power consumption in the mobile network occurs and some of the ways this power consumption can be reduced. 

Nice chart from Huawei presentation (no link) that shows 89% of a network spend is Opex vs 11% Capex. Also, energy costs are roughly 5.5-6 % of the total network opex which translates into many millions, if not billions.#Free5Gtraining #5G #4G #GreenFuture #Green5G #TechForGood pic.twitter.com/9hTqMapjKM

— Free 5G Training (@5Gtraining) August 13, 2020

The chart in the Tweet above (also in the presentation) clearly shows that the energy costs for operators run in many millions. Small power saving schemes can still have a big impact on the total energy reduction, thereby saving huge amounts of energy and costs.

ZTE Communications Magazine back in March discussed Energy Consumption Challenges and Prospects on B5G Communication Systems - https://t.co/vfAynT4eGZ#Free5Gtraining #ZTE #5G #5GNR #NGRAN #5GRAN #5GNetwork #5GTechnology #EnergyEfficiency #GreenEnergy #SON #AIML #5GSignaling pic.twitter.com/kLgdPuko6I

— Free 5G Training (@5Gtraining) October 31, 2021

The March issue of ZTE Communications Magazine contains some good articles looking at how to tackle the energy challenges in the network going forward. This recent article by Ericsson is also a good source of information on this topic.

Anyway, the slides and the video of the tutorial is embedded below:

Beginners: Energy Consumption in Mobile Networks - RAN Power Saving Schemes from 3G4G

Related Posts:

• The 3G4G Blog: Reducing 5G Device Power Consumption Using Connected-mode Discontinuous Reception (C-DRX)
• The 3G4G Blog: Huawei's Power Digitalization 2025 Summit
• Free 6G Training: Will 6G Just a better 5G? 

Reducing 5G Device Power Consumption Using Connected-mode Discontinuous Reception (C-DRX)

Back in 2019, when we were still participating in physical event, I heard Sang-Hoon Park, ESVP, Head of Regional Network O&M Headquarter, KT talk about 'KT’s journey to large-scale 5G rollout' at Total Telecom Congress.

Interesting nugget from KT about battery life. 63% of users care about battery life but only 19% about design. Also the battery capacity has evolved significantly over generations. Finally C-DRX will play a big role in 5G battery saving @totaltelecom #TTCongress pic.twitter.com/665sokRH0T

— 3G4G (@3g4gUK) October 30, 2019

South Korea is blessed with three highly competitive MNOs and due to this, the government asked them to launch their 5G networks at the same time in 2018. I have also blogged about how KT is working on reducing the latency of their network here.

Anyway, as you can see in the picture above, using Connected-mode Discontinuous Reception (C-DRX), KT was able to show huge power saving in the 5G Samsung smartphone. They also made a video embedded below:

KT has some more details from their blog post back in 2019 here. Also some more details on RayCat here. Both the sites are in Korean but you can use Google translate to get more details.

What is KT battery saving technology (C-DRX)?

KT's'battery saving technology' is shortened to'Connected Mode Discontinuous Reception' and is called C-DRX. In simple terms, it is one of the technologies that reduces battery usage by periodically switching the communication function of a smartphone to a low power mode while data is connected.

In CDRX technology, the base station and the terminal share CDRX information through RRC setting and reconfiguration, so when there is no packet transmission/reception by the terminal, the terminal transmission/reception terminal can be turned off to reduce battery consumption, and the CDRX setting is optimized to reduce the user's battery consumption. It is possible to increase the available time for related applications.

In order to reduce the battery consumption of the terminal, it is a technology that controls the PDCCH monitoring activity, which is a downlink control channel related to the terminal identifier, through RRC. The base station controls the CDRX through RRC, and how the communication company optimizes and applies this was a big task. Is the first in Korea to optimize this technology and apply it to the national network.

In simple terms, the smartphone is not using communication, but it turns off the power completely and enters the standby state to reduce power consumption. When not in use, it completely turns off the power wasted in transmitting and receiving even during the standby time, thus extending the user's smartphone usage time.

As can be seen from the picture above, battery saving technology saves battery by completely turning off the communication function when there is no data or voice call. If the network does not have the battery saving technology applied, it is always connected to the communication network and waits even when not in use. Then, the battery is always connected to the communication function and the battery saving technology overcomes this part.

When Qualcomm announced their Industry’s First Mobile Platform with Integrated 5G back in 2019, the press release said:

The new integrated Snapdragon 5G mobile platform features Qualcomm® 5G PowerSave technology to enable smartphones with the battery life users expect today. Qualcomm 5G PowerSave builds on connected-mode discontinuous reception (C-DRX, a feature in 3GPP specifications) along with additional techniques from Qualcomm Technologies to enhance battery life in 5G mobile devices – making it comparable to that of Gigabit LTE devices today. Qualcomm 5G PowerSave is also supported in the Snapdragon X50 and X55 5G modems, which are expected to power the first waves of 5G mobile devices introduced this year.

The picture is from the slide deck here. See links in further reading below to learn more about this feature.

Further Reading:

• All about Wired and Wireless Technology: LTE Connected Mode DRX (link)
• Netmanias: Future LTE Designed by SK Telecom: ​(2) Application of C-DRX, July 2017 (link)
• Ericsson: A technical look at 5G mobile device energy efficiency, Feb 2020 (link)
• ZTE via IEEE Access: Power Saving Techniques for 5G and Beyond, July 2020 (link)

Related Posts:

• Operator Watch Blog: All three mobile network operators in South Korea launched 5G on Dec 1, 2018
• Operator Watch Blog: How is KT Reducing the Latency of their 5G Network