Showing posts with label Network Architecture. Show all posts
Showing posts with label Network Architecture. Show all posts

Wednesday, 4 December 2019

Challenges of 5G Inter-Node Handovers

In all mobile communication networks handovers are the most complex signaling procedures, because multiple network elements (or network functions) are involved. Thus, it is logical that dual connectivity with two different base stations contributing to the radio connection simultaneously are even more complicated. And in EN-DC these two base stations are often covering different footprints using different carrier frequencies.This leads to a situation where we have more options for performing a handover in detail compared with plain LTE handover scenarios before.

The two signaling scenarios presented below illustrate in which different ways a change of the LTE master eNodeB can be performed during an ongoing EN-DC radio connection by using the X2 interface. In a very similar way it is also possible to perform S1 handover from old to new MeNB.

The pros and cons of these options have been discussed already by Martin Sauter in his Wireless Moves blog.

Inter-MeNB Handover without 5G Inter-Site Anchor

Figure 1 shows the easiest way of handing over the signaling connection from one MeNB to another one. Here it is up to the new MeNB to decide if and how the 5G part of the radio connection is continued.

Figure 1: X2 Handoverof EN-DC connection without 5G inter-site anchor


The handover is triggered when the UE sends a RRC Measurement Report (step 1) indicating that a stronger 4G cell than the currently used primary cell was measured. From its neighbor list the current MeNB detects that this better cell belongs to a neighbor eNB.

To provide both, the the Master Cell Group (MCG) and Secondary Cell Group (SCG) parameters to this neighbor eNB the old MeNB queries the SCG configuration parameters from the old SgNB by performing the X2AP SgNB Modification procedure (step 2+3).

Then it sends the X2AP Handover Request message to the target MeNB (step 4) including all information necessary to continue the 5G radio link in case the target MeNB decides to go for this option.

However, what comes back from the target MeNB is a plain LTE handover command (LTE RRC Connection Reconfiguration message [step 6]) embedded in the X2AP Handover Request Acknowledge message (step 5).

Due to this the old MeNB releases all 5G resources and the UE context in the SgNB (steps 7 + 10).

After the UE  successfully connected via radio interface with the target cell in the new MeNB the S1AP Path Switch procedure is executed to re-route the GTP/IP-Tunnels on S1-U (step 8) and releases the X2 UE context in the old MeNB (step 9)

The new MeNB then waits for a new inter-RAT measurement event B1 (step 11) before starting a new SgNB addition procedure (step 12).  Once the SgNB addition is successfully completed including all necessary reconfigurations/modifications on RRC and S1 the payload transmission over 5G resources is continued.

Inter-MeNB Handover with 5G Inter-Site Anchor

Now figure 2 shows what happens when the new MeNB decides to keep the existing UE context in the SgNB while the RRC measurement results and parameters are identical with what was presented above. 
Figure 2: X2 Handoverof EN-DC connection with 5G inter-site anchor

The difference in the call flow starts at step 5 when the new MeNB after receiving the X2AP Handover Request (step 4) starts the X2AP SgNB Addition procedure towards the SgNB (old = new!). The SgNB-UE-X2AP-ID earlier requested in step 2+3 acts as the reference number for the existing context that is going to be continued.

After adding the SgNB UE context successfully the new MeNB sends the X2AP Handover Request Acknowledge message including an UE Context Kept = "true" flag and the Handover Command (step 8).

After the UE successfully connected to the target cell of the new MeNB the S1AP Path Switch procedure is performed and the temporary X2 UE context between old and new MeNB is released (step 10).

The big advantage of handling the handover in this way: The duration of the interruption of the payload transmission over 5G radio resources is minimalized and subscriber experience is significantly better compared to the scenario in figure 1.

Monday, 2 December 2019

Guest Post: Exploring Network Convergence of Mobile, Broadband and Wi-Fi

This is a guest post by Ben Toner, Founder and Director, Numerous Networks


Are multiple networks better than one?

How many articles have you read with a title similar to "Which technology is better, 5G or Wi-Fi6?" If, like me, you regularly use Wi-Fi and cellular (I still use 4G though) then you might find it hard to take sides.

Enter Network Convergence - the concept of bringing multiple networks together to get the best of them all. Imagine, as an end user, not having to decide which network to use but instead feeling satisfied that your data was traversing the best combination of networks at that moment in time.

Imagine a business traveler being connected to Wi-Fi which is slow or busy while trying to take that all important conference call while sitting in an airport. Because you are roaming you want to use that Wi-Fi but you do not want to compromise the video call quality. If your network and device could work together to use just enough cellular data to supplement the slow Wi-Fi so that you stayed within your daily roaming quota but never lost a moment in the video call - then you would probably be very happy with that service. Better still, as you start walking off, if the call transitioned from Wi-Fi to cellular with no dropouts or hangup then you might be delighted!

Earlier I underlined best because that in itself is somewhat complicated.  The example above is easy to desribe but quite hard for to achieve within a framework where all possible scenarios are handled that well, for every user. The common questions which need to be factored into any such choice are:
  • What do I as the end user want? 
  • What performance can each network deliver. 
  • How important is the transfer of content at that time and 
  • How much am I willing to pay for it (how many MB of my data plan am I willing to use?). 

This is one of the challenges that we cannot easily solve today, but technology is being developed to help in that process. The operators and device vendors are working within standardisation to develop technology which can provide such a converged service. However at this time there is still a rules mechanism behind it all which does not really describe how user input and preference is going to be captured.

In the last 10 years I have witnessed many battles within service providers when deciding what "one size fits all" service to offer everyone when deciding how to make service provider Wi-Fi available to their customers; all fuelled by my points above.

A lot of concepts are well designed and somewhat mature but deciding exactly what will be implemented in standards is currently ongoing.

In the following slides and video I introduce this whole concept of Network Convergence. The following content introduces the concept and then takes a detailed look at the ATSSS; technology being defined in 3GPP. I also have highlighted the technologoies you can get hold of today to try out network convergence.

I encourage you all to download the example technologies and try convergence for yourself. I'm eager to hear opinions of what technologies work best for each of you. And better still, what is not being provided which you think should be...

Looking forward to your feedback and answering your questions...





Ben Toner
Founder and Director, Numerous Networks


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Friday, 22 November 2019

5G Call Drops in EN-DC: A Thread for Service Quality?


As explained in the post about EN-DC setup the addition of 5G NR radio resources to an ongoing LTE connection provides additional bandwidth for user plane data transmission. And it seems to be fair to say that at least in social media today 5G speed test results, especially throughput measurements, are treated as the benchmark for EN-DC service performance. Hence, it is also logical that a loss of the physical 5G radio link (5G drop) could have a serious impact on user experience.

I write "could", because as a matter of fact many 5G drops will not be recognized by subscribers using non-realtime services including HTTP streaming.

Due to the dual connectivity of LTE Master eNodeB (MeNB) and Secondary gNodeB (SgNB) the signaling trigger points indicating a 5G drop are also a bit more complex compared to what we know from LTE. Indeed, both network nodes are able to release 5G radio resources abnormally using three different X2AP message flow scenarios as shown in figure 1.

Figure 1: Three Basic Signaling Flows for Abnormal Release of 5G Radio Resources

Which of these individual message flows will be found in the trace data depends on which of the two base stations is the first one that detects a problem on the 5G radio link.

A particular case that is seen quite often in live networks is illustrated in figure 2.

Figure 2: 5G Drop due to SGC Failure in UE



Here the trigger is a LTE RRC SCG Failure Information NR message sent by the UE to the MeNB. Thus, the MeNB requests the release of 5G radio resources, which is acknowledged and executed by the SgNB.

In addition (not show in the figures) also the GTP/IP-Tunnel for user plane transport between S-GW and gNB is released by the MeNB after successful completion of the X2AP SgNB Release procedure.

For the UE the 5G drop is not as serious as a drop of the LTE radio connection would be. It is just a fallback on plain LTE, so to say. And after the switching the GTP/IP-Tunnel back to a downlink endpoint at the eNB 4G payload transmission continues.

The longer the overall duration of the radio connection the higher is the risk that the 5G radio resources are lost during an EN-DC call. One of my favorite cases is a subscriber with a radio connection that last a bit more than two and a half hours - see figure 3.

Figure 3: Location Session Record of a Single Subscriber indicating a total number 340 SgNB Drops over 2:33 Hours

Thanks to the smart algorithms of NETSCOUT's TrueCall geolocation engine there is high confidence that she or he sits in an indoor environment, but is served by an outdoor 5G cell. Thus, the penetration loss of the 5G signal is significant. Due to the higher frequency the path loss has also higher impact on the 5G than on the 4G radio signal. This seems to be the main reason why the 5G radio link drops as often as 340 times, which leads to an overall 5G (SgNB) Drop Rate of 83% for this connection.

However, the impact on the subscriber experience might not be a serious one as a different KPI, the 5G EN-DC Duration Rate indicates. According to the Duration Rate 99.99% of all the time 5G radio resources have been available for the subscriber. This is possible, because as also shown in figure 2 within a relatively short time new 5G radio resources are allocated again to this connection. Even if the subscriber is watching e.g. a Netflix video the buffering of already downloaded data on the end user device should be sufficient to conceal the short interruption of the data transfer over 5G resources.

With rising amount of EN-DC traffic it might be rather problematic for the network to handle the additional signaling load originating from the frequent 5G additions and releases. In extreme cases this may even lead to congestion due to CPU overload in RAN nodes or virtual network functions.

For realtime services like Voice over New Radio (VoNR) the entire situation changes. Here even short interruptions of the user plane radio transmission can be perceived by subscribers so that the above discussed 5G Duration Rate KPI will become insufficient to estimate the service quality. Hence, this will drive the demand for a fully integrated view of 5G RAN and Core KPIs covering both, signaling and application quality.




Thursday, 7 November 2019

Introduction to 5G ATSSS - Access Traffic Steering, Switching and Splitting


Last month we made a short tutorial on 5G and Fixed-Mobile Convergence (FMC). One of the features covered in that was ATSSS. It deserved a bit more detail so we made a short tutorial on this feature.

Access Traffic Steering, Switching and Splitting or ATSSS for short is being standardized as part of 3GPP Rel-16 and allows traffic steering across multiple accesses at a finer granularities than a PDU session.  It is an optional feature both on the UE and the 5GC network. ATSSS introduces the notion of Multi Access PDU session, a PDU session for which the data traffic can be served over one or more concurrent accesses (3GPP access, trusted non-3GPP access and untrusted non-3GPP access). The simplest way to visualize it is as shown below:


The presentation and video is embedded below:







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Tuesday, 22 October 2019

From traditional RAN to Open RAN - O-RAN: Goals and Challenges


My Open RAN tutorial has recently gained popularity with recent announcements from Altiostar, Mavenir, Parallel Wireless, Telefonica and Vodafone. With TIP Summit in few weeks time, I am hoping for a lot more curious people to discover that blog post and video.

Olivier Simon, Director, Radio Innovation, Orange spoke about "O-RAN: Goals and Challenges" at Open Networking Summit Europe 2019. In his presentation, he explained how O-RAN will trigger more intelligence and openness in the RAN domain. He talked about which use cases will require this new architecture and why O-RAN is coming at the right time. Major architectural change are necessary in the next years in order to improve E2E latency and benefit from the flexibility of virtualized network functions. O-RAN will provide the right framework in order to perform this transformation in an open manner and keeping at the same time economies of scale thanks to a global adoption.


The presentation also touches on O-RAN Software Community. The O-RAN Alliance recently partnered with the Linux Foundation to establish the O-RAN-Software Community (O-RAN-SC), to provide that open source software application layer to the RAN. O-RAN-SC will foster development of an open source infrastructure platform for running 5G RAN solutions.

The key aspects of ORAN-SC are:
  • New Open Community focused on RAN Software in collaboration with O-RAN Alliance
  • Set up for collaboration across OPNFV, ONAP, Akraino and other Open Source projects

Here is the video of the conference embedded below:



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Tuesday, 24 September 2019

When does your 5G NSA Device Show 5G Icon?


After I wrote about the 5G Icon Display back in February, I received lots of other useful and related materials, mostly from 3GPP standards delegates. Based on this updated information, I created a presentation and video called 'The 5G Icon Story'. Only recently did I realize that I didn't add it to the blog. So here it is.

And for people who are impatient and directly want to jump to the main point, it's UpperLayerIndication in SIB 2 as can be seen above.

The slides and video is embedded below.





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Sunday, 15 September 2019

Thursday, 12 September 2019

How the Addition of 5G Radio Resources Increases the Complexity of LTE Signaling Procedures


While everybody is excited about the growing number of 5G deployments and speed test results it is easy to forget that a highly reliable LTE core and radio access network is the prerequisite for 5G non-standalone (NSA) data transmission.

Indeed, the 5G radio resources are just added to the ongoing LTE connection to provide higher bandwidth that enables in turn higher throughput. In other words: the current 5G deployments are designed for and limited to the needs of enhanced Mobile Broadband (eMBB) traffic.

To boost the user experience a 4G and a 5G base station cooperate and bundle there joint resources in one radio connection. The whole scenario is known as E-UTRA-NR Dual Connectivity (EN-DC) and as a matter of fact this dual connectivity increases the complexity of the RAN signaling tremendously.

The figure below shows the two base stations involved in the radio connection. On the left side is the Master eNodeB (MeNB) that controls the entire signaling connection. On the right side sits the en-gNB, also called Secondary gNodeB (SgNB). The inconsistency of acronyms originates from 3GPP specs. 3GPP 37.340 "E-UTRA and NR Multi-connectivity" can be seen as an umbrella document that originally coined "MeNB" and "SgNB". However, when standarizing more details these acronyms have been replaced with Master Node (MN) and Secondary Node (SN) and the latter is named "en-gNB" when used in EN-DC scenarios. (Sure this spec has a lot more terms to offer an is a must-read for every acroynm enthusiast.)

However, these naming conventions defined in 3GPP 37.340 have not made it into the protocol specs, especially not into 3GPP 36.423 "X2 Application Part" that names its message set for enabling EN-DC consequently "SgNB ...." - as also shown in the figure.

By the way the SgNB should also not be imagined as a single network element. On the 5G side often a virtual RAN architecture is already deployed. In such a VRAN a gNB central unit (CU) controls several gNB distributed units (DUs) and multiple remote radio heads (RRHs) including the 5G antennas can be connected to each DU.



5G Radio Resource Addition in EN-DC Mode

Before 5G radio resources can be added to the connection a LTE RRC connection and at least a default bearer for the user plane including its GTP/IP-Tunnel between S-GW and eNB must have been successfully established.

The trigger for adding 5G resources to this call is mostly an inter-RAT measurement event B1 (not shown in the figure). However, also blind addition of a 5G cells have been observed in some cases where the 5G cell coverage is expected to overlap exactly the footprint of the LTE master cell. 

All in all, there can be a 1:1 mappig between 4G and 5G cells when antennas are mounted very close to each other and pointing into the same direction. However, it is also possible that several 5G small cells (especially when using FR2 frequency bands) are deployed to cover the footprint of a 4G macro cell. 

The end-to-end signaling that adds 5G resources to the connection starts with the X2AP SgNB Addition Request message (1). It contains information about the active E-RABs of the connection, UE NR capabilities and often the singal strenght of the 5G cell as measured before is included as well. The message triggers allocation of 5G radio resources in the SgNB.

Similar to a X2 handover procedure the X2AP SgNB Addition Request Acknowledge message (2) is used to transport a NR RRC CG-Config message (3) back to the MeNB where it is "translated" into NR RRC Connection Reconfiguration and NR RRC Radio Bearer Config messages that are sent to the UE enclosed in a LTE RRC Connection Reconfiguration message. In these messages beside the Cell Group ID the 5G PCI and the absolute SSB frequency (a synonym for NR ARFCN) are found. Both, 5G PCI and SSB frequency in combination represent the identity of a 5G cell "visible" for the UE on the physical 5G radio interface. 

To keep the figure more simple I have spared the "translation" process in MeNB and show instead as next step the combined LTE/NR RRC Connection Reconfiguration Complete (4) that is send by the UE back to the MeNB to confim activation of the 5G radio link. 

After this the UE and the SgNB are ready to the 5G resources for radio transmission. However, one important component is still missing: a new GTP/IP-Tunnel for transporting the payload from the core network's serving gateway (S-GW) to the SgNB. 

The gNB downlink transport layer address (gNB DL TLA) and its appropriate GTP Tunnel Endpoint Identifier (TEID) have been already to the MeNB in step (2). Indeed, there are some more TLAs and TEIDs found in this X2AP message, especially for data forwarding across the X2 user plane interface (not shown in figure).

The MeNB forwards the gNB DL TLA/TEID to the MME (6) where it is forwarded to the S-GW using GTP-C signaling in case the two core network elements are connected over S11 reference point. The uplink TLA/TEID on the S-GW side remain the same as assigned before during establishement of the E-RAB (not shown in figure). So the new tunnel is now ready to be used (7) and transmission of payload packet starts immediately. 

In step (8) the MME confirms the successful tunnel establishment to the MeNB.

To total duration of the entire procedure from step (1) to (8) sums up to slightly more than 100 ms under lab conditions and typically around 300 ms in the live network. 

This delay does not have a direct impact on user plane latency in the initial 5G setup phase. However, the subscriber experience might be different when it comes to inter-MeNB handover, because there is no direct handover between 5G neighbor cells. 

Changing the MeNB due to subscriber mobility means: release all 5G resources on the source (M)eNB side, perform intra-LTE handover to the target (M)eNB and add new 5G resources after handover is successfully completed. 

Monday, 5 August 2019

An Introduction to Non-Terrestrial Networks (NTN)


I made a short introductory tutorial explaining what is meant by Non-Terrestrial Networks. There is is lot of work on this that is planned for Release-17. Slides and video below.






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Thursday, 7 March 2019

Updated 5G Terminology Presentation (Feb 2019)


I made this video before MWC with the intention to educate the attendees about the various architecture options and 5G terminologies being discussed. As always, happy to get feedback on what can be done better. Slides followed by video below.







Complete list of our training resources are available on 3G4G page here.

Tuesday, 12 February 2019

Prof. Andy Sutton: 5G Radio Access Network Architecture Evolution - Jan 2019


Prof. Andy Sutton delivered his annual IET talk last month which was held the 6th Annual 5G conference. You can watch the videos for that event here (not all have been uploaded at the time of writing this post). His talks have always been very popular on this blog with the last year talk being 2nd most popular while the one in 2017 was the most popular one. Thanks also to IET for hosting this annual event and IET Tv for making this videos available for free.

The slides and video is embedded below but for new starters, before jumping to this, you may want to check out about 5G Network Architecture options in our tutorial here.




As always, this is full of useful information with insight into how BT/EE is thinking about deploying 5G in UK.

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Thursday, 3 January 2019

Nice short articles on 5G in 25th Anniversary Special NTT Docomo Technical Journal

5G has dominated the 3G4G blog for last few years. Top 10 posts for 2018 featured 6 posts on 5G while top 10 posts for 2017 featured 7. In makes sense to start 2019 posting with a 5G post.

A special 25th Anniversary edition of NTT Docomo Technical Journal features some nice short articles on 5G covering RAN, Core, Devices & Use cases. Here is some more details for anyone interested.

Radio Access Network in 5G Era introduces NTT Docomo's view of world regarding 5G, scenarios for the deployment of 5G and also prospects for further development of 5G in the future. The article looks at the main features in 5G RAN that will enable eMBB (Massive MIMO), URLLC (short TTI) and mMTC (eDRX).

Interested readers should also check out:

Core network for Social Infrastructure in 5G Era describes the principal 5G technologies required in the core network to realise new services and applications that will work through collaboration between various industries and businesses. It also introduces initiatives for more advanced operations, required for efficient operation of this increasingly complex network.

This article also goes in detail of the Services Based Architecture (SBA). In case you were wondering what UL CL and SSC above stands for; UpLink CLassifiers (UL CL) is a technology that identifies packets sent by a terminal to a specific IP address and routes them differently (Local Breakout) as can be seen above. It is generally to be used to connect to a MEC server. Session and Service Continuity (SSC) is used to decide if the IP address would be retained when the UE moves to a new area from the old one.

Interested readers should also check out:
Evolution of devices for the 5G Era discusses prospects for the high-speed, high-capacity, low-latency, and many-terminal connectivity features introduced with 5G, as well as advances in the network expected in the future, technologies that will be required for various types of terminal devices and the services, and a vision for devices in 2020 and thereafter.

According to the article, the medium term strategy of R&D division of NTT Docomo has three main themes: 5G, AI and Devices. In simple terms, devices will collect a lot of data which will become big data, 5G will be used to transport this data and the AI will process all the collected Big Data.

NTT Docomo has also redefined the devices as connecting through various technologies including cellular, Wi-Fi, Bluetooth & Fixed communications.

Interested readers should also check out:

The final article on 5G, Views of the Future Pioneered by 5G: A World Converging the Strengths of Partners looks at field trials, partnerships, etc. In fact here the embedded video playlist below shows some of these use cases described in the article



In addition there are other articles too, but in this post I have focused on 5G only.

The 25th Anniversary Special Edition of NTT Docomo Technical Journal is available here.

Friday, 19 October 2018

5G Network Architecture Options (Updated)


ICYMI, we created an updated video on 5G Network Architecture options. The videos and slides are embedded below.



This updated presentation/video looks at 5G Network Architecture options that have been proposed by 3GPP for deployment of 5G. It covers the Standalone (SA) and Non-Standalone (NSA) architecture. In the NSA architecture, EN-DC (E-UTRA-NR Dual Connectivity), NGEN-DC (NG-RAN E-UTRA-NR Dual Connectivity) and NE-DC (NR-E-UTRA Dual Connectivity) has been looked at. Finally, migration strategies proposed by vendors and operators (MNOs / SPs) have been discussed.


Nokia has also released a whitepaper on this topic that I only became aware of after my slides / video were done. More details in the tweet below.


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Friday, 14 September 2018

End-to-end Network Slicing in 5G

I recently realised that I have never written a post just on Network slicing. So here is one on the topic. So the first question asked is, why do we even need Network Slicing? Alan Carlton from Interdigital wrote a good article on this topic. Below is what I think is interesting:

Network slicing is a specific form of virtualization that allows multiple logical networks to run on top of a shared physical network infrastructure. The key benefit of the network slicing concept is that it provides an end-to-end virtual network encompassing not just networking but compute and storage functions too. The objective is to allow a physical mobile network operator to partition its network resources to allow for very different users, so-called tenants, to multiplex over a single physical infrastructure. The most commonly cited example in 5G discussions is sharing of a given physical network to simultaneously run Internet of Things (IoT), Mobile Broadband (MBB), and very low-latency (e.g. vehicular communications) applications. These applications obviously have very different transmission characteristics. For example, IoT will typically have a very large number of devices, but each device may have very low throughput. MBB has nearly the opposite properties since it will have a much smaller number of devices, but each one will be transmitting or receiving very high bandwidth content. The intent of network slicing is to be able to partition the physical network at an end-to-end level to allow optimum grouping of traffic, isolation from other tenants, and configuring of resources at a macro level.

Source: ITU presentation, see below

The key differentiator of the network slicing approach is that it provides a holistic end-to-end virtual network for a given tenant. No existing QoS-based solution can offer anything like this. For example, DiffServ, which is the most widely deployed QoS solution, can discriminate VoIP traffic from other types of traffic such as HD video and web browsing. However, DiffServ cannot discriminate and differentially treat the same type of traffic (e.g. VoIP traffic) coming from different tenants.

Also, DiffServ does not have the ability to perform traffic isolation at all. For example, IoT traffic from a health monitoring network (e.g. connecting hospitals and outpatients) typically have strict privacy and security requirements including where the data can be stored and who can access it. This cannot be accomplished by DiffServ as it does not have any features dealing with the compute and storage aspects of the network. All these identified shortfalls of DiffServ will be handled by the features being developed for network slicing.

I came across this presentation by Peter Ashwood-Smith from Huawei Technologies who presented '5G End to-end network slicing Demo' at ITU-T Focus Group IMT-2020 Workshop and Demo Day on 7 December 2016. Its a great presentation, I wish a video of this was available as well. Anyway, the presentation is embedded below and the PPT can be downloaded from here.



The European Telecommunications Standards Institute (ETSI) has established a new Industry Specification Group (ISG) on Zero touch network and Service Management (ZSM) that is working to produce a set of technical specifications on fully automated network and service management with, ideally, zero human intervention. ZSM is targeted for 5G, particularly in network slice deployment. NTT Technical review article on this is available here.

Finally, here is a presentation by Sridhar Bhaskaran of Cellular Insights blog on this topic. Unfortunately, not available for download.


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Sunday, 29 July 2018

Automating the 5G Core using Machine Learning and Data Analytics

One of the new entities introduced by 3GPP in the 5G Core SBA (see tutorial here) is Network Data Analytics Function, NWDAF.
3GPP TR 23.791: Study of Enablers for Network Automation for 5G (Release 16) describes the following 5G Network Architecture Assumptions:

1 The NWDAF (Network Data Analytics Function) as defined in TS 23.503 is used for data collection and data analytics in centralized manner. An NWDAF may be used for analytics for one or more Network Slice.
2 For instances where certain analytics can be performed by a 5GS NF independently, a NWDAF instance specific to that analytic maybe collocated with the 5GS NF. The data utilized by the 5GS NF as input to analytics in this case should also be made available to allow for the centralized NWDAF deployment option.
3 5GS Network Functions and OAM decide how to use the data analytics provided by NWDAF to improve the network performance.
4 NWDAF utilizes the existing service based interfaces to communicate with other 5GC Network Functions and OAM.
5 A 5GC NF may expose the result of the data analytics to any consumer NF utilizing a service based interface.
6 The interactions between NF(s) and the NWDAF take place in the local PLMN (the reporting NF and the NWDAF belong to the same PLMN).
7 Solutions shall neither assume NWDAF knowledge about NF application logic. The NWDAF may use subscription data but only for statistical purpose.

Picture SourceApplication of Data Mining in the 5G Network Architecture by Alexandros Kaloxylos

Continuing from 3GPP TR 23.791:

The NWDAF may serve use cases belonging to one or several domains, e.g. QoS, traffic steering, dimensioning, security.
The input data of the NWDAF may come from multiple sources, and the resulting actions undertaken by the consuming NF or AF may concern several domains (e.g. Mobility management, Session Management, QoS management, Application layer, Security management, NF life cycle management).
Use case descriptions should include the following aspects:
1. General characteristics (domain: performance, QoS, resilience, security; time scale).
2. Nature of input data (e.g. logs, KPI, events).
3. Types of NF consuming the NWDAF output data, how data is conveyed and nature of consumed analytics.
4. Output data.
5. Possible examples of actions undertaken by the consuming NF or AF, resulting from these analytics.
6. Benefits, e.g. revenue, resource saving, QoE, service assurance, reputation.

Picture SourceApplication of Data Mining in the 5G Network Architecture by Alexandros Kaloxylos

3GPP TS 23.501 V15.2.0 (2018-06) Section 6.2.18 says:

NWDAF represents operator managed network analytics logical function. NWDAF provides slice specific network data analytics to a NF. NWDAF provides network analytics information (i.e., load level information) to a NF on a network slice instance level and the NWDAF is not required to be aware of the current subscribers using the slice. NWDAF notifies slice specific network status analytic information to the NFs that are subscribed to it. NF may collect directly slice specific network status analytic information from NWDAF. This information is not subscriber specific.

In this Release of the specification, both PCF and NSSF are consumers of network analytics. The PCF may use that data in its policy decisions. NSSF may use the load level information provided by NWDAF for slice selection.

NOTE 1: NWDAF functionality beyond its support for Nnwdaf is out of scope of 3GPP.
NOTE 2: NWDAF functionality for non-slice-specific analytics information is not supported in this Release of the specification.

3GPP Release-16 is focusing on 5G Expansion and 5G Efficiency, SON and Big Data are part of 5G Efficiency.
Light Reading Artificial Intelligence and Machine Learning section has a news item on this topic from Layer123's Zero Touch & Carrier Automation Congress:

The 3GPP standards group is developing a machine learning function that could allow 5G operators to monitor the status of a network slice or third-party application performance.

The network data analytics function (NWDAF) forms a part of the 3GPP's 5G standardization efforts and could become a central point for analytics in the 5G core network, said Serge Manning, a senior technology strategist at Sprint Corp.

Speaking here in Madrid, Manning said the NWDAF was still in the "early stages" of standardization but could become "an interesting place for innovation."

The 3rd Generation Partnership Project (3GPP) froze the specifications for a 5G new radio standard at the end of 2017 and is due to freeze another set of 5G specifications, covering some of the core network and non-radio features, in June this year as part of its "Release 15" update.

Manning says that Release 15 considers the network slice selection function (NSSF) and the policy control function (PCF) as potential "consumers" of the NWDAF. "Anything else is open to being a consumer," he says. "We have things like monitoring the status of the load of a network slice, or looking at the behavior of mobile devices if you wanted to make adjustments. You could also look at application performance."

In principle, the NWDAF would be able to make use of any data in the core network. The 3GPP does not plan on standardizing the algorithms that will be used but rather the types of raw information the NWDAF will examine. The format of the analytics information that it produces might also be standardized, says Manning.

Such technical developments might help operators to provide network slices more dynamically on their future 5G networks.

Generally seen as one of the most game-changing aspects of 5G, the technique of network slicing would essentially allow an operator to provide a number of virtual network services over the same physical infrastructure.

For example, an operator could provide very high-speed connectivity for mobile gaming over one slice and a low-latency service for factory automation on another -- both reliant on the same underlying hardware.

However, there is concern that without greater automation operators will have less freedom to innovate through network slicing. "If operators don't automate they will be providing capacity-based slices that are relatively large and static and undifferentiated and certainly not on a per-customer basis," says Caroline Chappell, an analyst with Analysys Mason .

In a Madrid presentation, Chappell said that more granular slicing would require "highly agile end-to-end automation" that takes advantage of progress on software-defined networking and network functions virtualization.

"Slices could be very dynamic and perhaps last for only five minutes," she says. "In the very long term, applications could create their own slices."

Despite the talk of standardization, and signs of good progress within the 3GPP, concern emerged this week in Madrid that standards bodies are not moving quickly enough to address operators' needs.

Caroline Chappell's talk is available here whereas Serge Manning's talk is embedded below:



I am helping CW organise the annual CW TEC conference on the topic The inevitable automation of Next Generation Networks
Communications networks are perhaps the most complex machines on the planet. They use vast amounts of hardware, rely on complex software, and are physically distributed over land, underwater, and in orbit. They increasingly provide essential services that underpin almost every aspect of life. Managing networks and optimising their performance is a vast challenge, and will become many times harder with the advent of 5G. The 4th Annual CW Technology Conference will explore this challenge and how Machine Learning and AI may be applied to build more reliable, secure and better performing networks.

Is the AI community aware of the challenges facing network providers? Are the network operators and providers aware of how the very latest developments in AI may provide solutions? The conference will aim to bridge the gap between AI/ML and communications network communities, making each more aware of the nature and scale of the problems and the potential solutions.

I am hoping to see some of this blog readers at the conference. Looking forward to learning more on this topic amongst others for network automation.

Related Post:

Thursday, 12 July 2018

Minimum Bandwidth Requirement for 5G Non-Standalone (NSA) Deployment

I was attending the IEEE 5G World Forum live-stream, courtesy of IEEE Tv and happen to hear Egil Gronstad, Senior Director of Technology Development and Strategy at T-Mobile USA. He said that they will be building a nationwide 5G network that will initially be based on 600 MHz band.


During the Q&A, Egil mentioned that because of the way the USA has different markets, on average they have 31 MHz of 600 MHz (Band 71). The minimum is 20 MHz and the maximum is 50 MHz.

So I started wondering how would they launch 4G & 5G in the same band for nationwide coverage? They have a good video on their 5G vision but that is of course probably going to come few years down the line.

In simple terms, they will first deploy what is known as Option 3 or EN-DC. If you want a quick refresher on different options, you may want to jump to my tutorial on this topic at 3G4G here.

The Master Node (recall dual connectivity for LTE, Release-12. See here) is an eNodeB. As with any LTE node, it can take bandwidths from 1.4 MHz to 20 MHz. So the minimum bandwidth for LTE node is 1.4 MHz.

The Secondary Node is a gNodeB. Looking at 3GPP TS 38.101-1, Table 5.3.5-1 Channel bandwidths for each NR band, I can see that for band 71


NR band / SCS / UE Channel bandwidth
NR Band
SCS
kHz
5 MHz
101,2 MHz
152 MHz
202 MHz
252 MHz
30 MHz
40 MHz
50 MHz
60 MHz
80 MHz
90 MHz
100 MHz
n71
15
Yes
Yes
Yes
Yes








30

Yes
Yes
Yes








60













The minimum bandwidth is 5MHz. Of course this is paired spectrum for FDD band but the point I am making here is that you need just 6.4 MHz minimum to be able to support the Non-Standalone 5G option.

I am sure you can guess that the speeds will not really be 5G speeds with this amount of bandwidth but I am looking forward to all these kind of complaints in the initial phase of 5G network rollout.

I dont know what bandwidths T-Mobile will be using but we will see at least 10MHz of NR in case where the total spectrum is 20 MHz and 20 MHz of NR where the total spectrum is 50 MHz.

If you look at the earlier requirements list, the number being thrown about for bandwidth was 100 MHz for below 6 GHz and up to 1 GHz bandwidth for spectrum above 6 GHz. Don't think there was a hard and fast requirement though.

Happy to hear your thoughts.