A mmWave Special Cell in Open RAN Environment

NR RRC signaling messages exchanged for establishing a 5G radio connection, in particular the NR RRC Reconfiguration and NR RRC CG Config messages, contain a parameter called "SpCellID", which refers to the Special Cell ID. 

The concept of the Special Cell already exists in 3GPP LTE Advanced standards. Here a Special Cell is set of physical cells with same or different carrier frequency and physical cell ID (PCI) that overlap in a certain geographical area and thus, are combined for data transmission to/from UEs located in this area.

This concept now also gains high importance for 5G NR mmWave spectrum and here is why:

Many 5G mmWave radio transmitters can only handle a maximum bandwidth of 100 MHz, but the radio sector shall be covered with total bandwidth of e.g. 600 MHz. To achieve this six mmWave radio transmitters are installed in parallel at the same spot covering the same footprint. 

Each transmitter is identified on the radio interface by its own dedicated NR ARFCN (carrier frequency) and PCI. Thus, from UE point of view the sector is covered with 6 dedicated NR cells that all together form a Special Cell.

When a UE gets radio resources assigned in this 5G sector one of  the 6 cells is the Primary Cell, which NR CGI (Cell Global Identity) is then used as Special Cell ID in layer 3 signaling messages. All other cells act as Secondary Cells.

In an Open RAN environment the F1AP protocol allows perfect analysis of the SpCell resource allocation since it contains the SpCellID as well as all SCellIDs to be setup in the call. 

If the gNB-DU fails to allocated resources for a particular Secondary Cell this will also be signaled together with a failure cause value on F1AP as illustrated in the figure below. Also radio link failures occurring within the Special Cell will be signaled on F1AP including a cause value that provides deeper insight than  protocol causes seen on X2AP (in case of 5G NSA connections) or NGAP (in case of 5G SA connections). 

(click on image to enlarge)

Nokia veterans Harri Holma and Antti Toskala explain 5G Basics

An online conference on 5G is currently going on. 'Backed by 5G: Technology for Impact', is hosted by Start North as a part of the Aalto University Summer Course 5G Hack the Mall.

It is a two-week online conference which gathers the industry experts, entrepreneurs and policymakers together to discuss, present and question how 5G will affect our society, economy and everyday life. We want you to join the change by offering a chance to learn from the best, to start or strengthen your journey to expertise in 5G. With the support of our partners, you have the possibility to listen and get your questions answered by the global 5G leaders from the leading companies, academia, NGOs and public institutions, which all are daily involved with changing the world and enabling change with the latest technology.

Dr. Harri Holma from @nokia held a lecture yesterday on "What is Good to Know about 5G Technology Components". Thank you! If you're also interested, the lecture is to be revisited on our parallel event Backed by 5G's website, https://t.co/UfLsRcfgXy#5G #5GHacktheMall https://t.co/ClYy9gCl88

— Start North (@startnorth) June 9, 2021

The current conference features couple of Nokia experts who are well known in the industry for their books on the mobile technologies. Dr. Harri Holma, Fellow, Nokia Bell Labs, spoke on "What is Good to Know About 5G Technology Components". His talk is embedded below:

The second talk is by Dr. Antti Toskala, Fellow, Nokia Bell Labs, on Radio Access (5G Physical Layer). His talk is embedded below

Slides are shared to the 5G Summer School participants. If you are keen to get your hands on the slides, please email: hello@startnorth.com. You can watch all the videos from the event on the Start North YouTube channel here.

Related Posts: 

• The 3G4G Blog: Nokia Lectures in Collaboration with Bangalore University
• The 3G4G Blog: 5G Evolution with Matthew Baker, Nokia
• The 3G4G Blog: 5G Dynamic Spectrum Sharing (DSS)
• The 3G4G Blog: 5G Private and Non-Public Network (NPN) 

TSDSI's Low Mobility Large Cell (LMLC) Requirements in 5G

Back in November 2020, ITU completed the evaluation for global affirmation of IMT-2020 technologies. Three new technologies were successfully evaluated by ITU and were found to conform with the International Mobile Telecommunications 2020 (IMT-2020) vision and stringent performance requirements. The technologies are: 3GPP 5G-SRIT and 3GPP 5G-RIT submitted by the Third Generation Partnership Project (3GPP), and 5Gi submitted by Telecommunications Standards Development Society India (TSDSI). 

I have explained in earlier videos that 5G-SRIT  and 5G-RIT corresponds to Non-Standalone and Standalone respectively. 5Gi on the other hand is an updated version of 5G-RIT designed mainly to improve rural coverage. 

ITU completes evaluation for global affirmation of IMT-2020 technologies - https://t.co/dmALByqXh1 - So the 2 3GPP (@3GPPLive) 5G technologies 5G-SRIT and 3GPP 5G-RIT, and 5Gi submitted by TSDSI (@TSDSI_India) conform with IMT-2020 vision and stringent performance requirement. https://t.co/lFhfugcLux

— Zahid Ghadialy (@zahidtg) November 27, 2020

TSDSI announced this as follows:

TSDSI’s 5G Radio Interface Technology named as “5Gi” has cleared the rigorous processes of  International Telecommunication Union (ITU) and has been approved by the SG5 of ITU as a part of Draft Recommendation M.[IMT-2020.SPECS] in its meeting held on 23rd November 2020.

5Gi, the first  ever Mobile Radio Interface Technology contribution from India to become part of ITU-R’s  IMT recommendation, went through a rigorous evaluation process of the ITU-R working groups over the past 3 years before getting the approval.

This standard is a major breakthrough for bridging the rural-urban digital divide in 5G deployment due to enhanced coverage. It enables connecting majority of India’s villages through towers located at gram panchayats in a cost effective manner. It has found support from several countries as it addresses their regional needs from a 5G standpoint.

The standard will now be circulated by ITU to member states for adoption and approval. Specifications are expected to be published by ITU in early February 2021.

TSDSI thanks its members, the Department of Telecommunications, Govt. of India and its partners for their support over the last four years in helping get this standard reach the final stage in ITU.

In a keynote address presented to the 2020 IEEE 5G World Forum plenary session, Radha Krishna Ganti from TSDSI discusses rural connectivity challenges in India, Low Mobility Large Cell requirements, benefits of implementing LMLC for rural coverage, and internet ecosystem updates. His talk is embedded as follows:

TSDSI explains their 5Gi technology as follows:

TSDSI standard fulfils the requirements of affordable connectivity in rural, remote and sparsely populated areas. Enhanced cell coverage enabled by this standard, will be of great value in countries and regions that rely heavily on mobile technologies for connectivity but cannot afford dense deployment of base stations due to lack of deep fibre penetration,  poor economics and challenges of geographical terrain. The International Telecommunication Union (ITU), a UN body that is setting requirements for IMT 2020 (aka 5G), had earlier adopted the Low-Mobility-Large-Cell (LMLC) use case proposed by TSDSI as a mandatory 5G requirement in 2017. This test case addresses the problem of rural coverage by mandating large cell sizes in a rural terrain and scattered areas in developing as well as developed countries. Several countries supported this as they saw a similar need in their jurisdictions as well. TSDSI successfully introduced an indigenously developed 5G candidate Radio Interface Technology, compatible with 3GPP Technology, at the International Telecommunications Union (ITU) in 2019 for IMT 2020 ratification. The RIT incorporates India-specific technology enhancements that can enable larger coverage for meeting the LMLC requirements. It exploits a new transmit waveform that increases cell range developed by research institutions in India (IIT Hyderabad, CEWiT and IIT Madras) and supported by several Indian companies. It enables low-cost rural coverage and has additional features which enable higher spectrum efficiency and improved latency.

While technically this sounds interesting and as discussed in the talk, would make sense due to a large market like India, there are other solutions that are already possible that probably may make this redundant.

As someone who worked with the rural communities to bring coverage in hard to reach areas, small cells and In-band backhaul was one such solution to improve coverage in not-spot areas. Examples of that here and here. Relays are other option that don't cost much but can bring coverage quickly, at a much lower price.

Typically, in practice, the cells easily reach 10km radius. In theory this distance can be as much as 100km. Last year, Australian operator Telstra and vendor Ericsson announced that they have successfully managed to increase the range of an LTE cell from 100 km to 200 km. So, we can already have large cells with existing 4G/5G cells. 

Facebook connectivity is working on SuperCell concept, a Wide-Area Coverage Solution for Increasing Mobile Connectivity in Rural Communities. Details here. NGMN published a paper on Extreme Long Range Communications for Deep Rural Coverage. Details here.

Finally, we also have 5G Integrated Access and Backhaul (IAB) that can be used for backhauling and solving backhaul issues. They will end up playing a role in rural areas as well as dense urban areas eventually.

Let me know what you think.

Related Posts:

• The 3G4G Blog: IMT-2020 (5G) Requirements
• 3G4G: 5G Terminology
• Free 6G Training: TSDSI's Vision for India to Leapfrog to 5.5G / 6G
• The 3G4G Blog: Reliance Jio and 5G Network Architecture Option 6
• The 3G4G Blog - Opinion: What is "Real 5G" or "True 5G" 

5G User Plane Redundancy

We looked at the 5G Enhanced URLLC (eURLLC) earlier. One of the ways to improve reliability is to have redundancy in the user plane. This can use different approaches like: 

• Duplicating N3
• Adding a secondary gNB using Dual connectivity
• Introducing another UPF
• Two anchor UPFs

In fact they are all built on top of each other so you can decide how critical are your user plane redundancy needs. 

I came across this short video from Mpirical embedded below that covers this topic nicely. In case you want to refresh your 5G Core Network architecture, jump to our old tutorial here.

Related Posts:

• The 3G4G Blog: 5G Enhanced URLLC (eURLLC)
• The 3G4G Blog - Ultra Reliability: 5x9s (99.999%) in 3GPP Release-15 vs 6x9s (99.9999%) in 3GPP Release-16 
• The 3G4G Blog - Tutorial: Service Based Architecture (SBA) for 5G Core (5GC)
• 3G4G: 3GPP 5G Specifications
• 3G4G: 5G (IMT-2020) Wireless 

ITU Standardization Bureau on Machine Learning for 5G

Last year I blogged about Global ITU AI/ML 5G Challenge on the theme “How to apply ITU's ML architecture in 5G networks".  The grand challenge finale happened in December. All the recording and presentations are available here.

Back in October, Bilel Jamoussi from ITU presented a keynote to the 2020 IEEE 5G World Forum plenary session where he addressed the challenges of applying machine learning in networks, ITU’s ML toolkit, and ITU’s AI/ML in 5G Competition. IEEE Tv shared the presentation only in April so the competition part is a bit outdated. It does nevertheless an interesting 20 minute talk.

ITU Recommendation Y.3174, Framework for data handling to enable machine learning in future networks including IMT-2020 is available here.

Related Posts: 

• The 3G4G Blog: Artificial Intelligence (AI) / Machine Learning (ML) in 5G Challenge by ITU
• The 3G4G Blog: IMT-2020 (5G) Requirements 

3GPP RAN Plenary Update and Evolution towards 5G-Advanced

(click on image to enlarge)

ETSI recently held a webinar to provide a 3GPP RAN Plenary update by Wanshi Chen, Senior director of technology at Qualcomm Technologies, who was appointed as the RAN Chair not too long back. The webinar video is embedded below. The following is from the 3GPP summary of the webinar:

Wanshi Chen acknowledged that Release 17 - the third release of 5G specifications - has been under pressure due to COVID-19 restrictions, but despite making the move to e-meetings, he reported that the group’s experts have managed to ensure positive progress towards the freeze of the RAN1 physical layer specifications on schedule, by December 2021.

This is to be followed by the Stage 3 freeze (RAN2, RAN3 and RAN4) by March 2022 and the ASN.1 freeze and the performance specifications completion by September 2022 – On the timeline agreed back in December 2019.

This staggered timeline has been made achievable with careful planning and management, demonstrated to the webinar viewers via a complex planning schedule, with a slide showing the array of Plenary & WG meetings and Release landmarks - Interspersed with a series of planned periods of inactivity, to allow delegates some relief from 3GPP discussions.

Wanshi Chen noted that the efficiency of e-meetings has not been comparable with physical meetings, in terms of getting everything done. To compensate for that, the companies involved have planned two RAN1 meetings in 4Q21 and two meetings for each of the RAN working groups in the 1Q22. He observed: “We will monitor Release 17 RAN progress closely and take the necessary actions to make sure we can get the release completed on time.”

Release 18 Planning

Looking forward to Release 18 and the start of work on 5G-Advanced, Chen outlined the schedule for an online RAN workshop from June 28 – July 2, to define what will be in the release. The workshop will set the scene for email discussions about the endorsed topics for consideration. The work will culminate with Release 18 Package Approval, at the December 2021 Plenary (RAN#94).

The high-level objective of the workshop will be to gather company proposals in three areas:

• eMBB driven work;
• Non-eMBB driven functionality;
• Cross-functionality for both.

Wanshi Chen concluded that during the Release 18 planning process, some capacity must be kept in hand; keeping around 10% of WG effort in reserve, for workload management and to meet late, emerging critical needs from commercial deployments.

The following Q&A topics were covered, along with the time stamps:

• The effect of the pandemic and eMeeting management schedules and tools (19.25).
• Balance between commercial needs and societal needs, emergency services, energy efficiency, sustainability (21.20).
• The importance of the verticals in the second phase of 5G – With 5G-Advanced. How will this Rel-18 workshop compare in scale with the 5G Phoenix workshop in 2015? (23.00)
• The job of the Chair is to be impartial…but Wanshi guesses that Antennas, MiMo enh., Sidelink, Positioning, xR, AI machine learning…. could come up in Rel-18! (26.15)
• Will 5G-Advanced have a strong identity & support? (30.05)
• The potential for hybrid meetings – No clear answers yet, but we have learnt a lot in the past year.(34.35)
• The link between gathering new requirements and use cases in SA1 and RAN work and RAN1’s role in focusing these needs for radio work. (40.10)
• Software-ization of the RAN. Do you see more open RAN work coming to 3GPP? (44.18)
• Machine type communications and IoT – Where is IoT going in 3GPP RAN? (47.01)
• Some thoughts on Spectrum usage from a 3GPP point of view, is that difficult to fathom for non-experts? (52.00)
• Can Standards writing become more agile, less linear? (54.00)

If you want to get hold of the slides, you will have to register on BrightTALK here and then download from attachments.

Signals Research Group has a short summary of 3GPP RAN #91 electronic plenary held in late March. It is available to download after registration from here.

xoxoxoxoxoxo Updated later, 07 June 2021 oxoxoxoxoxoxox 

5G-Advanced logo is now available as shown above. Guidelines on how to use the logo is available on 3GPP here.

Related Posts:

• The 3G4G Blog: Initiative to Remove Non-inclusive terms from 3GPP Specifications
• The 3G4G Blog: ATIS Webinar on '5G Standards Developments in 3GPP Release 16 and Beyond'
• The 3G4G Blog: Anritsu Webinar on 'Evolution of 5G from 3GPP Rel-15 to Rel-17 and Testing Challenges'
• The 3G4G Blog: Spectrum for 5G NR beyond 52.6 GHz 

Anomaly Detection and other AI Algorithms in RAN Optimization

Yesterday I watched this very inspiring live chat that I would like to recommend to anyone who is interested in how machine learning techniques (aka "AI") can help to optimize and troubleshoot the Radio Access Network.

 [The real contents of in the video starts at approx. 42:00 min] 

My key takeaways from this fireside chat are: 

Verizon Wireless has enough data (100… 500 time series KPIs per cell) that they use to feed anomaly detection ML algorithms and this generates a huge number of alarms, but only a few actionable outputs. 

The “big elephant” (Nick Feamster) is to identify if these alarms indicating real problems that can and have to be fixed or if they just indicate a new behavior of e.g. a new handset or a SW version that was not present in the training phase of the ML algorithm and hence, its pattern is detected as a new “anomaly”. 

For Bryan Larish (Director Wireless AI Innovation, Verizon) the “big open problem” is “that it is not clear what the labels are” and “no standard training sets exist”. 

[For more details watch the video section between 52.00 min and 57:32 min and listen to Bryan’s experience!] 

In most cases Verizon seems to need subject matter experts to classify and label these anomaly alarms due to “the huge diversity” in data pattern. 

According to Bryan only for very few selected use cases it is possible to build an automated loop to fix the issue. Especially the root causes of radio interference are often mechanical or cabling issues that need manual work to get fixed. 

All in all it is my personal impression at the end of the session that anomaly detection is currently a bit overhyped and that the real challenges and problems to be resolved start after anomalies are detected.

Nevertheless, as Bryan summarizes: “ML is a very, very powerful tool.” 

However, strategically he seems not to see a lot of value in anomaly detection by itself, but rather: “Can we use machine learning (results) to change how we build networks in the future?”

Positioning in 5G networks

I have written about the 5G positioning techniques not that long back on this blog here and on connectivity technology blog here. With Release-16 now ready for deployment, Huawei has already announced world's first in 5G Indoor Positioning. Their announcement said:

China Mobile Suzhou and Huawei reached a new milestone with the verification of the 5G indoor positioning capability in metro transport scenarios in Suzhou — a major city located along the southeastern edge of Jiangsu Province in eastern China. The verification showed that, even with pRRUs being hidden, a positioning precision of 3 to 5 m can be achieved in 90% of the platform and hall areas. This is the first time that 5G indoor positioning has been verified on live networks in the world, providing valuable experience for the commercial growth of 5G positioning in vertical industries.

Indoor location-based services are in high demand of vertical applications, such as indoor navigation, asset tracking, geofencing, logistics management, and personnel management, which reflects the huge market space of indoor positioning. Currently, indoor positioning technologies are of great variety and most of them need to be deployed and maintained individually, resulting in high end-to-end costs. As a part of the continuous evolution of 5G, positioning has been added to 3GPP Release 16 finalized in mid 2020 to realize indoor positioning by leveraging the ultra-high signal resolution empowered by 5G's high bandwidth, multi-point measurements, and multi-access edge computing (MEC) deployment.

The verification was based on Huawei's 5G digital indoor solution LampSite and leading MEC solution. The LampSite units measure the radio signals of 5G devices and work with MEC to analyze the signal characteristics. Based on the results of the analysis, leading algorithms are used to precisely locate 5G devices.

We wrote about Huawei's Lampsite on Telecoms Infrastructure blog last year here.

A group of Ericsson engineers have written a research paper on 5G positioning recently. It's available on arXiv here. Here is the abstract:

In this paper we describe the recent 3GPP Release 16 specification for positioning in 5G networks. It specifies positioning signals, measurements, procedures, and architecture to meet requirements from a plethora of regulatory, commercial and industrial use cases. 5G thereby significantly extends positioning capabilities compared to what was possible with LTE. The indicative positioning performance is evaluated in agreed representative 3GPP simulation scenarios, showing a 90 percentile accuracy of a few meters down to a few decimeters depending on scenarios and assumptions.

Definitely worth a read if you like hardcore technical papers.

Related Posts:

• The 3G4G Blog: Positioning Techniques for 5G NR in 3GPP Release-16
• Connectivity Technology Blog: 5G Indoor Precise Positioning
• Telecoms Infrastructure Blog: Huawei 5G Lampsite wins awards and speed tests 

A look at 5G Applications, Application Functions & Application Servers

We often get questions about 5G Service Based Architecture. Luckily, we have a tutorial that we can redirect people to. It's available here and the video just crossed 50K views. One of the questions that people often want to understand, is about the Application Function (AF) and how does it fit in the Applications Architecture.

To explain this, we made a tutorial. The slides and videos are embedded below. In that we have used the examples from our XR, V2X and Private Networks tutorials. All links are available at the bottom of this post.

Video:

Slides:

Intermediate: 5G Applications Architecture - A look at Application Functions & Application Servers from 3G4G

Related Posts:

• 3G4G: 5G Service Based Architecture (SBA)
• The 3G4G Blog: 5G eXtended Reality (5G-XR) in 5G System (5GS)
• The 3G4G Blog: An Introduction to Vehicle to Everything (V2X) and Cellular V2X (C-V2X)
• The 3G4G Blog: 5G Private and Non-Public Network (NPN)
• 3G4G: 3GPP 5G Specifications 

5G RAN Functional Splits

I have been meaning to write a post on RAN functional splits and even make a video. Recently I came across multiple of these things so I am taking a shortcut by posting them here. 

The first is this basic introductory video from Parallel Wireless where they explain why you need RAN splits providing examples of various functional splits for 4G and 5G mobile networks. It is embedded below:

The next one is slightly detailed video from the book "5G Radio Access Network Architecture: The Dark Side of 5G" by Sasha Sirotkin (Editor). I wrote a review of the book here and Sasha kindly made a video for our channel which is embedded below:

Finally, RCR Wireless published an article looking at the 5G functional splits in detail, by Ankur Sharma, Associate Vice President, Product Management and Strategy, Radisys. The article 'Exploring functional splits in 5G RAN: Tradeoffs and use cases' is available here.

Feel free to suggest other videos, articles, etc. in comments.

Related Posts:

• 3G4G: Book review - 5G Radio Access Network Architecture: The Dark Side of 5G by Sasha Sirotkin (Editor)
• The 3G4G Blog: The Status of 5G Standalone (5G SA) Networks - March 2021
• The 3G4G Blog: Initiative to Remove Non-inclusive terms from 3GPP Specifications
• The 3G4G Blog: Everything you need to know about 5G Security
• The 3G4G Blog: Open RAN Explanation, Videos, White papers and Other Resources
• The 3G4G Blog: Free 6G Training