Friday 5 March 2021

How to Identify Network Slices in NG RAN

In my last post I described how NG RAN resources can be divided into network slices. 

Now I would like to show how these network slices and the traffic they carry can be identified. 

The key to this is a parameter from the NG Application Protocol (NGAP) called the Single Network Slice Selection Assistance Information (S-NSSAI). When configuring virtual network functions in NG RAN there are lists of S-NSSAI exchanged, e.g. between gNB-CU CP and AMF during NGAP Setup procedure, to negotiate which network slices have to be supported in general. 

When it comes to connection establishment starting with NGAP Initial Context Setup for each PDU session that is established its individual S-NSSAI is signaled. 

The S-NSSAI - as show in the figure below - consists of two parameters, the Slice/Service Type (SST - 8 bit) and the optional Slice Differentiator (SD - 24 bit). The exact format and numbering ranges are defined in 3GPP 23.003.

3GPP 23.501 defines a set of default values for SST as listed in the following table:

Slice/Service type

SST value

Characteristics

eMBB

 

1

Slice suitable for the handling of 5G enhanced Mobile Broadband.

URLLC

2

Slice suitable for the handling of ultra- reliable low latency communications.

MIoT

3

Slice suitable for the handling of massive IoT.

V2X

4

Slice suitable for the handling of V2X services.

So when looking back at the figure it emerges that for each subscriber represented by an IMSI the SST allows to identify which services are running. 

On the other hand allows to see if in which virtual network the subscriber is active. In my example I have defined that the resources are shared among a Public MNO that I consider the owner of the network hardware and two different private (campus) networks. While IMSI 1 and IMSI 2 are not allowed to use any other network slice the IMSI 3 is allowed to "roam" betweent the public slice and the two private network slices. This explains why a slice-specific authentication functionality as defined in Rel. 16 is necessary. 

Related Posts:

Thursday 4 March 2021

The Fifth Generation Fixed Network (F5G)


Back in Feb 2020, ETSI announced the launch of a new group dedicated to specifying the fifth generation of Fixed Network (ETSI ISG F5G). The press release said:

We are entering an exciting new era of communications, and fixed networks play an essential role in that evolution alongside and in cooperation with mobile networks. Building on previous generations of fixed networks, the 5th generation will address three main use cases, a full-fiber connection, enhanced fixed broadband and a guaranteed reliable experience.

For home scenarios, emerging services such as Cloud VR (virtual reality) and AR (augmented reality) video streaming or online gaming introduce the necessity for ultra-broadband, extremely low latency and zero packet loss. Business scenarios such as enterprise Cloudification, leased line, or POL (Passive Optical LAN) require high reliability and high security. Other industry sectors have specific requirements on the deployment of fiber infrastructures including environmental conditions such as humidity, temperature or electromagnetic interference.

The ETSI ISG F5G aims at studying the fixed-network evolution required to match and further enhance the benefits that 5G has brought to mobile networks and communications. It will define improvements with respect to previous solutions and the new characteristics of the fifth-generation fixed network. This opens up new opportunities by comprehensively applying fiber technology to various scenarios, turning the Fiber to the Home paradigm into Fiber to Everything Everywhere.

ISG F5G considers a wide range of technologies, and therefore seeks to actively cooperate with a number of relevant standardization groups as well as vertical industrial organizations. ISG F5G will address aspects relating to new ODN technologies (Optical Distribution Network), XG(S)-PON and Wi-Fi 6 enhancements, control plane and user plane separation, smart energy efficiency, end-to-end full-stack slicing, autonomous operation and management, synergy of Transport and Access Networks, and adaptation of the Transport Network, amongst others.

The five work items approved last week deal with:

  • F5G use cases: the use cases include services to consumers and enterprises and will be selected based on their impact in terms of new technical requirements identified.
  • Landscape of F5G technology and standards: this work will study technology requirements for F5G use cases, explore existing technologies, and perform the gap analysis.
  • Definition of fixed network generations: to evaluate the driving forces and the path of fixed network evolution, including transport, access and on-premises networks. It will also identify the principal characteristics demarcating different generations and define them.
  • Architecture of F5G: this will specify the end-to-end network architectures, features and related network devices/elements’ requirements for F5G, including on-premises, Access, IP and Transport Networks.
  • F5G quality of experience: to specify the end-to-end quality of experience (QoE) factors for new broadband services. It will analyze the general factors that impact service performance and identify the relevant QoE dimensions for each service.

Then in May, at Huawei Global Analyst Summit 2020 (#HAS2020), Huawei invited global optical industry leaders to discuss F5G Industry development and ecosystem construction, and launched the F5G global industry joint initiative to draw up a grand blueprint for the F5G era. The press conference video is as follows:

Then in September 2020, ETSI released a whitepaper, "The Fifth Generation Fixed Network: Bringing Fibre to Everywhere and Everything"

Now there are couple of standards available that provides more insights.

ETSI GR F5G 001 - Fifth Generation Fixed Network (F5G); F5G Generation Definition Release #1:

In the past, the lack of a clear fixed network generation definition has prevented a wider technology standards adoption and prevented the creation and use of global mass markets. The success of the mobile and cable networks deployments, supported by clear specifications related to particular technological generations, has shown how important this generation definition is.

The focus of the 5th generation fixed networks (F5G) specifications is on telecommunication networks which consist fully of optical fibre elements up to the connection serving locations (user, home, office, base station, etc.). That being said, the connection to some terminals can still be assisted with wireless technologies (for instance, Wi-Fi®).

The main assumption behind the present document foresees that, in the near future, all the fixed networks will adopt end-to-end fibre architectures: Fibre to Everywhere.

The present document addresses the history of fixed networks and summarizes their development paths and driving forces. The factors that influence the definition of fixed, cable and mobile network generations will be analysed. Based upon this, the business and technology characteristics of F5G will be considered.

This table comparing the different generations of fixed networks is interesting too


ETSI GR F5G 002 - Fifth Generation Fixed Network (F5G); F5G Use Cases Release #1:

The present document describes a first set of use cases to be enabled by the Fifth Generation Fixed Network (F5G). These use cases include services to consumers and enterprises as well as functionalities to optimize the management of the Fifth Generation Fixed Network. The use cases will be used as input to a gap analysis and a technology landscape study, aiming to extract technical requirements needed for their implementations. Fourteen use cases are selected based on their impact. The context and description of each use case are presented in the present document.


The use cases as described in the present document are driving the three dimensions of characteristics that are specified in the document on generation definitions [i.1], namely eFBB (enhanced Fixed BroadBand), FFC (Full-Fibre Connection), and GRE (Guaranteed Reliable Experience). Figure 2 shows that:

  • depending on the use case, one or more dimensions are particularly important, and
  • all dimensions of the F5G system architecture are needed to implement the use cases.

I will surely be adding more stuff as and when it is available.

Related Posts:

Friday 26 February 2021

Network Slicing in NG RAN

I have been asked to explain in a nutshell how network slicing works in NG RAN. The most important facts you will find in the infographic below.

A network slice is virtual part of a network that offers full end-to-end connectivity for particular services and - optionally - for tenants. A tenant is a 3rd-party company that rents a virtual part of a public mobile operator's network. This allows the tenant to run its own private nation-wide mobile network without owning any hardware.

The network slicing is enabled by virtualization and all network functions can be divided into different slices as well. Thus, you can find in the figure the User Plane Function (UPF), gNB Central Unit for User Plane (gNB-CU UP) and gNB Distributed Unit (gNB-DU) all sliced.

It is also possible that a network function is dedicated for a particular network slice as in case of (gNB-) CU UP 2. 

In general - and this is the benefit of the cloudification - the NG RAN is a highly dynamic environment in which additional NW functions can be added (and later released) whenever this is necessary. Mostly this will be triggered by the load on CPU and memory resources. Here comes the automation into the games that deals in large parts with load balancing. Ideally automation enables a zero-touch network management. 

(click to enlarge)

However, the most precious of all RAN resources, the radio resources, cannot be administrated so flexibly and easily. Indeed, there are several automation instances that deal with radio resource management. Open RAN Alliance has defined the RAN Intelligent Controller (RIC) that is split into the Near-Realtime-RIC (RT RIC) that shall operate with a latency between 10 and 500 ms while the Non-Realtime RIC (NRT RIC) deals with non-time critical task, e.g. typical SON functions like Automatic Neighbor Reporting (ANR).

While the RIC can deal with a lot of problems there is one thing it cannot do: adding physical layer radio resources on demand. The physical resources are limited by the number of remote radio heads/antennas and as long as we have only static beamforming the physical resources covering a geographical sector are also limited by hardware and their distribution must be carefully planned. Thus, I think it is fair to say that the RIC (or a similar proprietary automation function) has to deal with the most complex situations in the RAN.

Radio resources can also be sliced in different ways. My figure illustrates a kind of slicing on the physical layer where different physical resource blocks (PRB) are allocated to different network slices. 

However, this is not the only way how the resources of a cell or a beam can be sliced. Beside a split of PRBs it is also possible to slice on the MAC layer where logical channels (slice-specific radio bearers) are mapped onto transport channels or on PDPC layer as it was described and demonstrated by the 5G NORMA project (Chapter 2.1, page 17 ff.).

What in the end will be implemented by the RAN equipment manufacturers is a question I that cannot answer today. 

Monday 22 February 2021

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.

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:

Monday 15 February 2021

Open RAN Explanation, Videos, White papers and Other Resources


Couple of years back, just before MWC 2019, we made what I would like to think of as the first proper explanation of Open RAN. I posted it on this blog here and the video has been viewed nearly 45,000 times. At that time, the concept of Open RAN was still quite new and in my day job with Parallel Wireless*, I was spending quite some time explaining what it really means.

Anyway, I think it made the concept of Open RAN so easy to understand that I have seen tens, if not hundreds, of people copy it, but only a few kind people give credit. 

With the Telecom Infra Project (TIP) and O-RAN driving the ecosystem further, I along with my Parallel Wireless colleagues, created a series of videos to explain the concept a bit more in detail. As expected, the introductory videos have been extremely popular while the others have been reasonably popular as well. The concept from these videos have been copied even far and wider than the original one. 

Embedded below is the playlist of all the videos (6 currently but 1 more in works):

In addition to these, I maintain a list of Open RAN whitepapers (publicly available without registration), some good articles, etc. on the 3G4G website here. I try and update the site on a regular basis so feel free to put any resources in the comments of this post and I will add them on the site during the next update.

Related Posts:

*Full Disclosure: I work for Parallel Wireless as a Senior Director, Technology & Innovation Strategy. This blog is maintained in my personal capacity and expresses my own views, not the views of my employer or anyone else. Anyone who knows me well would know this. 

Tuesday 9 February 2021

Free 6G Training

Last year we announced the launch of Free 5G Training. It was successful beyond our imagination. While we have just over 1,300 Twitter followers, on LinkedIn, we have over 30,000. The 5G for Absolute Beginners Udemy course already has over 6,000 students. This was a good enough motivation for us to launch a 6G equivalent with world's first 6G training course.

Back in November, we soft-launched the Free 6G Training website/blog along with Twitter and LinkedIn. The initial engagement and following are already very encouraging. 

We also created 'An Introduction to 6G Training Course' here. 6G Candidate technologies, that require most details and is the main area of focus for 6G will be added as and when I find time and have enough material.

There is also a new 6G Wireless R&D LinkedIn group that has been started to share information and discuss doubts, etc. I am hoping many people will be able to join.

If you are a 6G expert or researcher or have ideas on how I can do better or want to contribute with articles, presentations, videos, etc., please feel free to get in touch on LinkedIn.

One final thing, along with all this, the 3G4G page has a section on '6G and Beyond-5G Wireless Technology'. I add links to all publicly available whitepapers and other good material out there. 

It may also be useful to know that the 3G4G page has a search box on top that searches across all our channels and can be helpful in finding information on any mobile technology related topic.

Tuesday 2 February 2021

NWDAF in 3GPP Release-16 and Release-17

We looked at Network Data Analytics Function, NWDAF, in detail here. While the 3GPP Release-16 work just starting back then, we have now completed Rel-16 and looking at Release 17. 

The 5G Core (5GC) supports the application of analytics to provide Intelligent Automation of the network, In Rel-16 the set of use cases that are proposed for the NWDAF has been widely expanded. 

In an earlier post, we looked at the ATIS webinar discussing Release-16 & forthcoming features in Rel-17. Puneet Jain, Director of Technical Standards at Intel and 3GPP SA2 Chairman talked briefly about NWDAF. The following is from his talk:

Release-16 provides support for Network Automation and Data Analytics.  Network Data Analytics Function (NWDAF) was defined to provide analytics to 5G Core Network Functions (NFs) and to O&M. It consists of several services that were defined in 3GPP Rel-16 and work is now going in Release 17 to further extend them. 

In release 16 Slice load level related network data analytics and observed service experience related network data analytics were defined. NF load analytics as well Network Performance analytics was also specified. NWDAF provides either statistics or prediction on the load communication and mobility performance in the area of interest. 

Other thing was about the UE related analytics which includes UE mobility analytics, UE communication analytics, Expected UE behavior parameter, Related network data analytics and abnormal behavior related network data analytics.

The NWDAF can also provide user data congestion related analytics. This can be done by one time reporting or continuous reporting in the form of statistics or prediction or both to any other network function. 

QoS sustainability analytics, this is where the consumer of QoS sustainability analytics may request NWDAF analytics information regarding the QoS change statistic for a specific period in the past in a certain area or the likelihood of QoS change for a specific period in future, in certain areas. 

In Release 17, studies are ongoing for network automation phase 2. This includes some leftover from Release 16 such as UE driven analytics, how to ensure that slice SLA is guaranteed and then also new functionality is being discussed that includes things like support for multiple NWDAF instance in one PLMN including hierarchies, how to enable real-time or near-real-time NWDAF communications, how to enable NWDAF assisted user pane optimization and last which is very interesting is about interaction between NWDAF and AI model and training service owned by the operator.

This article on TM Forum talks about NWDAF deployment challenges and recommendations:

To deploy NWDAF, CSPs may encounter these challenges:

  • Some network function vendors may not be standards compliant or have interfaces to provide data or receive analytics services.
  • Integrating NWDAF with existing analytics applications until a 4G network is deployed is crucial as aggregated network data is needed to make decisions for centralized analytics use cases.
  • Many CSPs have different analytics nodes deployed for various use cases like revenue assurance, subscriber/marketing analytics and subscriber experience/network management. Making these all integrated into one analytics node also serving NWDAF use cases is key to deriving better insights and value out of network data.
  • Ensuring the analytics function deployed is integrated to derive value (e.g., with orchestrator for network automation, BI tools/any UI/email/notification apps for reporting).

Here are some ways you can overcome these challenges and deploy efficient next-generation analytics with NWDAF:

  • Mandate a distributed architecture for analytics too, this reduces network bandwidth overhead due to analytics and helps real-time use cases by design.
  • Ensure RFPs and your chosen vendors for network functions have, or plan to have, NWDAF support for collecting and receiving analytics services.
  • Look for carrier-grade analytics solutions with five nines SLAs.
  • Choose modular analytics systems that can accommodate multiple use cases including NWDAF as apps and support quick development.
  • Resource-efficient solutions are critical for on-premise or cloud as they can decrease expenses considerably.
  • Storage comes with a cost, store more processed smart data and not more raw big data unless mandated by law.
  • In designing an analytics use case, get opinions from both telco and analytics experts, or ideally an expert in both, as they are viewed from different worlds and are evolving a lot.

This is such an important topic that you will hear more about it on this blog and elsewhere.

Related Posts:

Tuesday 26 January 2021

Banana and Egg gets 5G Telesurgery


Last year I wrote a detailed post on '5G Remote Surgery and Telehealth Solutions' here. Since then many people with little or no understanding of how the technology works have got in touch with me to educate me about all the 5G remote surgeries taking place. 

I am always prepared to learn new things and looked at both of these surgeries (detailed below) with open mind. I was still unable to see the 5G angle here. In fact in the case of banana, I don't even know if 5G was used.

Back in 2014, a BBC article detailed how a surgeon in Canada has performed over 20 remote surgeries with the help of a robot including colon operations and hernia repairs. The article goes on to ask, "The technology behind long-distance surgery is now mature enough to be used more widely, allowing people to access world-leading expertise and better healthcare without having to travel. Could it become the norm in hospitals?"

The first case is from Aug 2020 as shown in the video above where Doctor Liu Rong from a hospital in Beijing takes on the challenge of remotely controlling a medical robot in distant Qingdao City via the 5G network to finish an egg membrane suture surgery in 90 minutes.

The question here is that where exactly was 5G used and why? Did both the ends have 5G or just one end? Etc. I was unable to find a schematic to show the end-to-end details that would provide credibility to such a scenario.

To explain what I mean, when Vodafone UK launched 5G, they demonstrated low latency by giving an example of Haptic tackle using TeslaSuit. You can read the details and watch the video here

As you can see, the end-to-end solution architecture is nicely explained as shown in this picture. I would expect a similar kind of schematic for the surgery scenario. While I can clearly understand the use case for sports outdoor, I am not able to understand the use case for the surgery indoors. Where was the access point? What frequency was used? Was this Standalone or Non-Standalone network? And many other questions like these. 

The second case was a more recent one. The video is embedded below.

Even though the video mentions 5G and many other sites (see this LinkedIn post with nearly 2.5 million views) that have picked this up mention 5G, the original Instagram video does not mention 5G. In all likelihood there is no 5G connection with this one.

Surely there will be a real life 5G remote surgery use case someday that will capture our imagination but not today.

Related Posts:

Thursday 21 January 2021

Some Cool Gadgets from CES 2021

 


With all the disruption on events and conferences due to Covid-19 pandemic, it wasn't a surprise that CES 2021 was completely digital. It was also moved by a week so it did disrupt a few smaller events here and there. I thought it may be worth sharing a few quick videos to give you an idea about the big announcements out there. BBC has a nice detailed coverage of the whole event here.

Let's start with this short 4 mins video from CNET that quickly shows all the best devices from CES 2021.

The next is this slightly longer 12 minute video that has 20 awesome gadgets for smart homes.

Finally, there is this 11 minute plus video that is a summary of all new mobile phone technology. It's not as polished as the ones before but still good enough.

In addition, here are some links for you to watch the keynotes from relevant to our industry:

Samsung gets full marks for making a short event highlights video here. In addition, they have a press conference video and a detailed keynote video. All details are on their CES microsite here.

TCL's rollable phone and tablet is nicely captured by CNET here. Their CES microsite is here.

LG Electronics may want to learn a few tricks from Samsung as far as making microsites and videos are concerned. They CES micro site is here. The full press conference is here while Engadget summarises the keynote in just over 9 mins here. LG Wing video here makes an interesting viewing.

Finally, here are 3 links that have summarised the best/weird gadgets from CES and yes there are overlaps in their choices

If you want to share something, feel free to comment.

Related Posts:

Friday 15 January 2021

UE Radio Capability Signaling Optimization (RACS) in Rel. 16

The data volume of UE Radio Capability Information defined in 3GPP 38.306 is already high and will further increase starting with Rel. 16 due to additional supported bands and other features.

Due to this 3GPP has standardized in Release 16 what is called UE Radio Capability Signaling Optimization (RACS) for both, E-UTRAN/EPS and NG RAN/NGC networks. 

Release 16 RACS does not apply to NB-IoT.

The first key element of this feature set is the introduction of a new UE Radio Capability ID that is structured as defined in 3GPP 23.003 and shown in figure 1 below:

UE Radio Capability ID
Figure 1: UE Radio Capability ID according to 3GPP 23.003

The components of this new ID are:

  •    TF - Type Field (TF): identifies the type of UE radio capability ID.
            Type = 0 -> manufacturer-assigned UE radio capability ID
            Type = 1 -> network-assigned UE radio capability ID

  •  The Version ID configured by the UE Capability Management Function (UCMF) that is part of the EPS/5GC. The Version ID value makes it possible to detect whether a UE Radio Capability ID is current or outdated.

·      The Radio Configuration Identifier (RCI) identifies the UE radio configuration.

The PLMN-assigned UE Radio Capability ID is assigned to the UE using the Non-Access Stratum UE Configuration Update Command or Registration Accept message (figure 2).

Figure 2: PLMN-assigned UE Radio Capability Update according to 3GPP 23.743

The new UCMF (UE radio Capability Management Function) stores All UE Radio Capability ID mappings in a PLMN and is responsible for assigning every PLMN-assigned UE Radio Capability ID.

Due to introduction of the UMCM in the core networks the new Nucmf service-based interface is defined for the 5GC and new S17 reference point is defined for the EPS as shown in figure 3.

Figure 3: Network Architecture with UCMF according to 3GPP 21.916

Each UE Radio Capability ID stored in the UCMF can be associated to one or both UE radio capabilities formats specified in 3GPP TS 36.331 [LTE RRC] and 3GPP TS 38.331 [NR RRC]. The AMF must only be able ot handle the NR RRC format while the MME uses the LTE RRC format. Which format is required by the UCMF is configurable.

If at any time the AMF/MME has neither a valid UE Radio Capability ID nor any stored UE radio capabilities for the UE, the AMF/MME may trigger the RAN to provide the UE Radio Capability information and subsequently request the UCMF to allocate a UE Radio Capability ID.

In NG RAN the UE Capability Request can be requested by the AMF as a flag in any NGAP Downlink NAS Transport message or by sending a NGAP UE Radio Capability Check Request (for checking compatibility of IMS voice capabilities). This triggers a NR RRC UE Capability Transfer procedure and subsequently NGAP UE Radio Capability Info Indication or NGAP UE Radio Capability Check Response (for IMS voice support parameters).

Using the NGAP UE Capability ID Mapping procedure the NG RAN node is able to request the most recent UE Capability ID mapping information from the core network functions AMF/UCMF. The same functionality is implemented in S1AP for signaling between eNB and MME/UCMF.

If the volume of the LTE/NR RRC UE Capability to be sent by the UE is larger than the maximum supported size of a PDCP SDU (specified in 3GPP 38.323) then the UE Capability Info can be transported in LTE/NR RRC using a chain of UL Dedicated Message Segment messages.

Figure 4: RRC UL Dedicated Segment Message transporting UE Radio Capability Information according to 3GPP 36.331 and 38.331

Each of these message will have a dedicated segment number and the last one has the rrc-MessageSegmentType =  “lastSegment”, which triggers reassembly of the orignal UE Capabability information in the receiving entity.