Wednesday, 1 April 2020

A Look into 5G Virtual/Open RAN - Part 2


In the first blog post of this series the different virtual RAN functions, interfaces and protocols have been discussed. Now it is time to have a look at a set of procedures that are required for the establishment of an UE connection in virtual 5G RAN.

The Big Picture

In 5G standalone RAN the crucial elements for user plane payload transport of an UE connection are  GTP/IP transport tunnels and a dedicated radio bearer on the radio interface.

When looking at the 5G RAN there are two of such tunnels: one on NG-U (aka N3) that is controlled by NGAP, and one on F1-U that is controlled by F1AP - see figure 1.

On behalf  of these two tunnels payload data can be transported between the 5G core network User Plane Function (UPF) to the gNB Distributed Unit (gNB-DU) and vice versa. For the transport over the 5G RAN fronthaul (realized e.g. as eCPRI) and across the radio interface a dedicated radio bearer (DRB) for the user plane transport must be configured by the gNB Central Unit for the Control Plane (gNB-CU CP).

As in LTE it is the RRC protocol that establishes this DRB. However, due to the virtualization the different protocol layers for the air interface are also distributed and the gNB-DU is in charge of all the lower layer PHY/RLC/MAC parameters (e.g the c-RNTI), while the gNB-CU CP assigns higher layer parameters of PDCP and RRC like the DRB-ID. Since only the gNB-CU CP can send downlink RRC messages to the UE the lower layer parameters from the DU first need to be sent in uplink direction to the gNB-CU CP.

Beside this parameter exchange the F1AP is also responsible for the tunnel management of the F1-U Tunnel.

The downlink tunnel endpoint information is provided by the gNB-DU using F1AP, but the uplink tunnel endpoint terminates at the gNB-CU UP and thus, its endpoint parameters are received by the gNB-CU CP when it exchanges information with the gNB-CU UP on behalf of the E1AP protocol.

Figure 1: Network Functions, Protocols and Parameters involved in Setup of User Plane Data Transmission Resources
(click on the image to see full size)
A similar situation we see for the NG-U tunnel that is controlled by NGAP, the protocol for communication between gNB-CU CP and the Access and Mobility Management Function (AMF) in the 5G core. Neither the gNB-CU CP nor hte AMF have direct access to the NG-U tunnel endpoints. Hence, E1AP is used again to transmit the downlink tunnel parameters to the gNB-CU CP while the uplink tunnel endpoint parameters must be sent by the UPF to the Session Management Function (SMF) using the Packet Forwarding Control Protocol (PFCP) and later by the SMF to the AMF over the service-based interface where the tunnel endpoint parameters are embedded in a JavaScript Object Notation (JSON) container.

By the way, JSON is a quite generic format for exchanging and storing different kind of data. Between the AMF and the SMF JSON is used to transport Non-Access Stratum Session Management messages (defined in 3GPP 24.501).

The Ladder Diagram

Having the Big Picture in mind it is now easier to look at the ladder diagram with the individual RAN messages for UE connection setup - shown in Figure 2.

It looks complicated, because the F1AP messages carry RRC plus NAS messages in uplink and downlink direction, but when understanding the underlying logic it is easy.

Figure 2: 5G VRAN Successful UE Connection Setup
(click on the image to see full size)

The very first step (in the figure: step 0) is the random access procedure executed on the MAC layer involving the UE and the gNB-DU.

After successful random access the UE sends the NR RRC Setup Request message. This is the Initial UL RRC Message transported by the F1AP from the gNB-DU to the gNB-CU CP. Actually the F1AP carries PDCP transport blocks and inside the PDCP the NR RRC messages are found, but to keep it simple I do not show the PDCP header in the ladder diagram.

Beside RRC Setup Request there are also some other initial NR RRC messages and RRC response messages possible (see step 1 and 2).

More RRC messages are transported over F1AP until the RRC Connection establishment is complete.

The NR RRC Setup Complete message also transports the initial NAS message and the reception of this message by the gNB-CU CP triggers the setup of a F1AP UE context. The concept of UE context management in F1AP is the same as in NGAP or - when looking back into the E-UTRAN - in S1AP.

The GTP/IP transport tunnel on F1-U is established during F1AP UE Context Setup assisted by E1AP Bearer Context Setup procedure that provides the necessary tunnel endpoint parameters.

In the same manner the NG-U tunnel is established by the NGAP Initial UE Context Setup procedure.

Additional NAS messages (especially for session management) and NR RRC Reconfiguration are exchanged to establish the end-to-end UE connection through the core network. And that's it.

Sunday, 29 March 2020

Mobile Voice Communications is neither Dying, nor Dead!

If you have been following the mobile industry for a long time, you could be forgiven for thinking that voice communications is dead. This 2013 article for example talks about the impending death of voice and this 2018 article talks about how smartphones have killed the art of conversation. These are just examples and I have read many similar articles in the last 5-10 years.

The thing is that a lot of unnecessary calls became SMS and messages once the price of SMS and data went down. Similarly, voice ceased to be a differentiator in many markets so they started offering unlimited voice and/or SMS locally. This does not necessarily solve my requirements for international calling so I moved on to Viber, WeChat and WhatsApp.

The annual TeleGeography Report and Database update (just released) estimates that international over-the-top (OTT) voice traffic reached 1 trillion minutes in 2019, compared to just 432 billion minutes of international carrier traffic.

Anyway, with the lockdown in many countries because of coronavirus COVID-19, people have re-discovered the use of voice communications again. While I prefer having meetings on the internet, sometimes it's just simpler to call using your phone. A friend discovered that while she has some 40 GB data allowance that was generally more than enough, working from home means that she is having to use her device as a hotspot that is using up all her data. Switching from OTT calling to unlimited voice calling in her package means that she doesn't have to worry about voice calls eating her data package.

She is not alone. Operators all over are reporting the rise in voice communications:

  • 27 Mar 2020 - O2 UK reported, "Since March 16th we have seen approximately 57% more voice traffic at the busiest point of the day. Typically voice traffic increases 5% year on year, and in a week we have experienced an increase of voice traffic comparable to nine years of regular demand." (link)
  • 26 Mar 2020 - Official numbers reported by CTIA from Verizon, AT&T, T-Mobile, Sprint and U.S. Cellular stated that mobile voice traffic was up 24.3% while mobile data traffic was up 9.2% (see photo above - link)
  • 24 Mar 2020 - Telenor Norwar tweeted, "Traffic has increased sharply since the coronary smith was seriously registered in this country. 50% increase in mobile voice, 25% increase in mobile data and 30-40% increase in fixed broadband"
  • 24 Mar 2020 - T-Mobile USA released some interesting stats including gaming, etc. With regards to voice, their announcement said, "People are talking and texting more. Messaging is up dramatically, with a 26% increase in SMS (texting) and a 77% increase in MMS (pictures, multi-party texts, etc.). And, the amount of time people spend on calls has increased 17% nationwide." (link)
  • 20 Mar 2020 - Telia in Denmark reported, "Thursday, March 12, the volume of speech in the network thus increased by 24% compared to the day before. Over the weekend 50% more was spoken - obviously due to a need to gain status on family and friends in the new situation. In the past working week, about 60% more has been spoken on the phone than on a normal week in March." (translated from original)
Is voice important for an operator? Probably not very much in the developed markets where users pay a good amount for data packages. In developing countries, voice is still a good source of revenue. At the TIP summit last year, Malaysian telecom giant Axiata said that ""every gigabyte costs about $1.40 to manufacture...generates only 80 cents in revenue...The 2G voice business currently funds any losses". This is not a long term sustainable model for these operators.


Funnily I just remembered that in a survey of over 1000 people in the USA regarding what they want from 5G, the third most important thing was "clearer voice quality". If you want to understand how voice quality is measured that see this tweet below


We may keep on seeing a boom in voice traffic as more lockdowns occur and they are even stricter. We will have to wait and see of this habit of talking sticks or it's just for this unusual situation.

Related Posts:

Friday, 20 March 2020

Real-life 5G Use Cases for Verticals from China

GSMA have recently published a series of reports related to China. This includes the 'The Mobile Economy China' report as well as reports on ‘Impacts of mmWave 5G in China’, ‘5G use cases for verticals China 2020’ and ‘Powered by SA case studies’. They are all available here.

China currently has 1.65bn subscribers (Excluding licensed cellular IoT) which is expected to grow to 1.73bn in 2025. The report quotes 1.20bn unique mobile subscribers that is expected to grow to 1.26bn by 2025. With a population of 1.44 billion, this would be assuming everyone over 10 years has a smartphone. 2G and 3G is being phased out so only 4G and 5G will be around in 2025. This would be different for IoT.

The 5G Use Cases for Verticals China 2020 report is comprised of 15 outstanding examples of 5G-empowered applications for verticals, ranging from industrial manufacturing, transportation, electric power, healthcare, education, to content creation, and zooms into the practical scenarios, technical features, and development opportunities for the next generation technology. Every use case represents the relentless efforts of 5G pioneers who are open, cooperative, and innovative.

  1. Flexible Smart Manufacturing with 5G Edge Computing (RoboTechnik, China Mobile, Ericsson)
  2. 5G Smart Campus in Haier Tianjin Washing Machine Factory (China Mobile, Haier)
  3. Aircraft Surface Inspection with 5G and 8K at Commercial Aircraft Corporation of China (Comac, China Unicom, Huawei)
  4. Xinfengming Group’s Smart Factory Based on MEC Technology (Xinfengming, China Mobile, ZTE)
  5. SANY Heavy Industry 5G and Smart Manufacturing (Sany, China Mobile, China Telecom, ZTE)
  6. Xiangtan Iron & Steel's 5G Smart Plant (Xisc, China Mobile, Huawei)
  7. The Tianjin 5G Smart Port (Tianjin, China Unicom, ZTE, Trunk)
  8. 5G Intelligent Connected Vehicle Pilot in Wuhan (China Mobile, Huawei, et al.)
  9. 5G BRT Connected Vehicle-Infrastructure Cooperative System (China Unicom, DTmobile, et al.)
  10. 5G for Smart Grid (China Mobile, Huawei, et al.)
  11. Migu's "Quick Gaming" Platform (China Mobile, et al.)
  12. 5G Cloud VR Demonstration Zone in Honggutan, Nanchang, Jiangxi Province (Besttone, China Telecom, Huawei)
  13. 5G Cloud VR Education Application Based on AI QoE (China Telecom, Nokia, et al.)
  14. China MOOC Conference: 5G + Remote Virtual Simulation Experiment (China Unicom, Vive HTC, Dell Technologies, et al.)
  15. 5G-empowered Hospital Network Architecture Standard (CAICT, China Mobile, China Telecom, China Unicom, Huawei, et al.)

They are all detailed in the report here.

I have written about 5G Use Cases in a blog post earlier, which also contains a video playlist of use cases from around the world. Not many from China in there at the moment but should be added as and when they are available and I discover them.


Related Posts:

Sunday, 15 March 2020

How Cellular IoT and AI Can Help to Overcome Extreme Poverty in a Climate-resilient Way

The Democratic Republic ofthe Congo (DRC) is the second largest country in Africa and it has a significant potential for agricultural development as the country has more land (235 million hectares) than Kenya, Malawi, Tanzania, and Zambia, combined, of which only 3.4% is cultivated.

Despite this, around 13 millions of Congolese live in extreme food insecurity, among them 5 millions acutely malnourished children. Current assessments show the trend is increasing.

In the southern provinces formerly known as "Katanga" the needs in maize for human consumption sum up to 700,000 tons per year, while the local production barely amounts to 120,000 tons per year. This means the provinces have to resort to importing food from neighboring countries, which represents a huge burden on the region's economy.

Another aspect of the problem is that 80% of the local production is made by women farmers, and the biggest challenge they face is the lack of daily agronomic monitoring and guidance. There is only a limited amount of agriculture experts in the region and without assistance, the farmersaverage output is at best one ton per hectare. However, field trials have proven that by using smart farming technology they can easily produce up to 6 tons per hectare year over year with the right sustainable approach and support. Artificial intelligence (AI), the Internet of Things (IoT) and big data analytics underpinned by mobile connectivity can even do more. They bring significant potential for capturing carbon, optimizing water, pesticide and fertilizer usage, and reducing soil erosion. Thus, African women can not only provide the solution to the local food gap/insecurity but also become the primary protectors of their environment.

The basic technical concept is not new. Back in 2016 Ooredoo Myanmar launched Site Pyo, a mobile agriculture information service for smallholder farmers. At its core Site Pyo is a weather forecast app that was enhanced with weather-dependent advice for ten crops, from seed selection to harvesting and storage. In addition the app displays the actual market prices for these crops. GSMA as a co-funder of the project celebrates Site Pyo as a big success, but it seems to be limited to Myanmar. Why?

„A lot of customization needs to be done to adapt the application functionality for a particular region“, says Dieu-Donn├ę Okalas Ossami, CEO of „e-tumba“, a French Start-up specialized in smart farming solutions for Sub-Sahara Africa. His company partners with iTK, a spin-off from CIRAD, the French Institute for tropical agronomy. The iTK crop-specific predictive models are based on years of agronomic data, but have originally been designed for big farmers. To meet the demands of women in Katanga requires more granular data for both, input and output.

As in case of Site Pyo weather predictions are important, but in addition there are data feeds from sensors on the spot. Weather stations measure constantly temperature and rainfall while sensors in the soil report its saturation with water, nitrogen and potassium.

„A typical real-time advice that our software provides is to delay the harvest for some additional days to maximize the yield“, explains Okalas Ossami. „However, even for two neighboring fields the particular advices are often different.“ 

Also the communication channels need to be taylored. Many women farmers are illiterate. For them the advice must be translated into the local language they speak and transmitted to their phones as a voice message. Those who can read and write will receive the notifications through short message service.

The mobile connectivity that links all elements of the system is realized by the mobile network operators present in the region.


Infographic: The Technical Environment Behind the Project
„Actually NB-IoT would fit to our use case“, says Okalas Ossami, „but it is not available. And there is neither LoRa nor SigFox.“ Hence, the sensors are using data connections of 3G and 4G radio access technology. In case of network outage or missing coverage a local field technician must collect the sensor data manually and transfer it to the data center through alternative channels.

It is the same field technician who installs the sensors. The woman farmers receive a basic training to understand how the system works, but they do not need to care about technical components - except keeping their mobile phones charged.

Here comes another important aspect into the game: How can the women trust this technical environment?

In case of Site Pyo the operator Ooredoo observed a quickly increasing user community measured by the number of app downloads. However, there was no indication to which extend the Myanmar farmers really used the app. The e-tumba solution addresses this gap by partnering with the non-government organization „Anzafrika“.

Anzafrika is present in the villages where the people live. One of its major targets is to overcome the extreme poverty by developing the regional economy. A key factor for this is that the smallholder farmers do not just see the market prices for their crops, but get real access to large, stable and long-term markets where these prices are paid. Anzafrika is brokering contracts between the woman farmers and large multinational corporations committed to the Economics of Mutuality, growing human, social and natural capital. The business model behind this concept was outlined by Bruno Roche and Jay Jakub in their book „Completing Capitalism:Heal Business to Heal the World“. Instead of focusing on greenhouse gas emissions (output) they insist that climate-resilient business models must measure the input needed for manufacturing goods. As an example: For one hot cup of coffee the greenhouse gas emissions are extremely low, but 3.4 liters of water are needed (most for packaging, processing and drinking) and 12 gram of top soil will be eroded. These are (among others) the expenses paid by the planet that are not taken into account by a carbon tax.

Coffee plantations are monocultures with all the known disadvantages resulting form this kind of farming. In the past the Congolese women farmers have grown maize as a monoculture. Now, with advice from Anzafrika and e-tumba they transitioned from an „all-maize“ sustenance crop to a semi-industrial „maize-sorghum“ production. This helps to minimize the top soil erosion and thus, to remunerate the natural capital involved in the process.  

Regarding the human and social capital Anzafrika monitors how the overall situation in the villages  is improving. The focus is on progress in well-beeing, satisfaction and health not just for the women farmers, but for their entire communities.

In 2019 smart farming technology have been tested and deployed with a group of 150 women in the province of Lualaba. Now, in 2020, their number is expected to rise to 500 and after 6 years the stunning target of 100,000 participants shall be met. A look at the download numbers of Site Pyo (206,000 in the course of one year) shows that these numbers are not over-optimistic.

The partnership between Anzafrika, e-tumba and iTK is now considered as a best international practice, as indicated by Patrick Gilabert, UNIDO Representative to the European Union in Brussels. It fully aligns with the development of new comprehensive strategies for Africa that aim at creating a partnership of equals and mutual interest through agriculture, trade and investment partnerships.

UNIDO, as the UN convener for the implementation of the Industrial Decade for Development of Africa” (IDDA 3) is always ready to join forces with innovative partners.

Monday, 9 March 2020

How LTE RRC (4G) and NR RRC (5G) Protocols are used in Parallel in EN-DC (5G NSA)

Last week I had a fruitful discussion with a fellow blogger on the web, Martin Sauter (@mobilesociety) regarding a post in which he compared features of LTE RRC (3GPP 36.331) and NR RRC (3GPP 38.331).

It was Martin's impression that the NR RRC protocol is primarily designed to be used in the 5G standalone mode. However, as I wrote in a comment to his post the NR RRC protocol is already used in EN-DC radio connections.

The reason is that the UE must be informed about Hundreds of lower layer 5G parameters (physical, MAC, RLC) that are needed for the payload transmission over 5G frequencies. Indeed, when it comes to user plane data transmission the gNB works almost independently and the UE must handle LTE and NR radio links in parallel.So it has two different radio units (even if combined into a single radio chip set). This double-functionality is also one important reason why 5G smartphones are quite expensive. It is a lot of software and know-how that sits inside these chips.

How much surplus code is really necessary to enable 5G technology becomes visible when looking at trace data using a state-of-the-art protocol test and monitoring tool.

When reading the 3GPP 36.331 (LTE RRC) standard document one might have the impression that just a few 5G parameters have been incorporated into this protocol to support EN-DC connections.

However, when looking into the details of e.g. the nr-SecondaryCellGroupConfig-r15 it turns out that some this single information element is indeed a huge block of NR information (total size: 1111 Byte)

It is an entire 5G RRC message (rRCReconfiguration) that is piggybacked by the LTE rrcConnectionReconfiguration message, because in 5G non-standalone mode this is the only way to transmit 5G signaling information to the UE. And as highlighted in the upper part of the screenshot there are a couple of NR RRC messages transported in so-called NR-RRCContainers* during the EN-DC Establishment Procedure.

And what about 5G standalone mode? For this radio access technology the 3GPP 38.331 Rel. 15 protocol is suitable as well. Hence, some parameters mentioned in the standard paper will never be seen in EN-DC. A perfect example is S-NSSAI (Single Network Slice Selection Assistance Information), because network slicing requires the connection with a 5G core network as a prerequisite. 


(click on image for larger version)

* This is not an 3GPP term, but coined by the developers of the decoding engine.

Wednesday, 4 March 2020

A Look into 5G Virtual/Open RAN - Part 1

Although it is understood in general that virtualization and increasing complexity are inherent characteristics of 5G networks many people are surprised when they realize the significant differences of 5G RAN architecture and signaling procedures compared to what they know from LTE or UTRAN.

In this blog post series I want to highlight some details that are not immediately visible when reading the 3GPP specs.

Figure 1 shows a virtualized gNB and the protocols it uses to communicate with its internal entities as well as with the UE and peer entities in neighbor network elements/functions.

Figure 1: Virtual Network Functions and Protocols in 5G RAN
(click on the image to see full size)

The core of the whole thing is the gNB-Central Unit for the Control Plane (gNB-CU CP). This function communicates directly with the UE using the NR RRC protocol. It also "talks" to the 5G Core Network represented by the AMF using the NGAP, a protocol very similar to the S1AP known from E-UTRAN. Neighboring 5G base stations are contacted using the XnAP, neighboring eNBs can be reached by using X2AP.

The other virtual functions of the gNB are the Central Units for User Plane (gNB-CU UP) and the Distributed Units (gNB-DU). While the gNB-CU UP is responsible for handling the transport of payload the gNB-DUs deal with all the allocation of radio resources, especially the scheduling. As a result the lower layer radio interface protocols, especially RLC and MAC terminate in the gNB-DUs.

For the RAN monitoring tools and the 3GPP Minimization of Drive Test (MDT) feature this means that RRC and Logged Measurement Reports sent by UEs will be available at gN-CU CP while all uplink radio quality measurements and call-related user plane metrics is only available at the gNB-DU - see figure 3.

Figure 2: Distribution of un-correlated RAN measurement tasks among different gNB virtual functions
(click on the image to see full size) 

And today, there is no 3GPP-standardized procedure to correlate this measurement information collected by different virtual gNB functions.

The full impact of the 5G RAN virtualization becomes even more evident when looking at Figure 3. It shows a single gNB-CU CP in charge of controlling several gNB-CU UPs and gNB-DUs.

In a live network deployment a single gNB-CU CP will control hundreds of gNB-DUs and maybe several gNB-CU UPs. This is why it is misleading to compare the connectivity of a gNB-CU CP with that of a LTE eNB. Rather it could be compared with a UTRAN RNC controlling a similar number of 3G base stations.


Figure 3: 5G RAN Connectivity
(click on the image to see full size)

Looking back into figure 1 we see that the F1AP is used for communication between gNB-CU CP and its gNB-DUs while the E1AP is the protocol that connects the gNB-CU CP with surrounding gNB-CU UPs.

Call-related control plane procedures of F1AP and E1AP are very similar to what is known from NGAP. There is a UE context established between the gNB-CU CP and the gNB-DU. On F1-U a GTP tunnel is established for user plane transport. At the same time an E1 Bearer Context in gNB-CU CP and gNB-CU UP keeps track of the most relevant user plane transport parameters.

All in all for setting up a single subscriber connection in the virtualized 5G RAN there are significantly more signaling transactions necessary than in E-UTRAN. Figure 4 shows a practical example.

Figure 4: 5G RAN Call Trace in NETSCOUT Session Analyzer
(click on the image to see full size)
The volume and complexity of signaling information is increasing when the UE moves or is redirected to virtual functions within one gNB e.g. due to load balancing.

The next blog post of this series will dive deeper into details of such call scenarios.

Stay tuned...

Sunday, 1 March 2020

5G Private and Non-Public Network (NPN)


Private Networks have been around for a while and really took off after 4G was launched. This is due to the fact that the architecture was simplified due to the removal of CS core and also the advancements in silicon, storage, computation, etc. allowed creation of smaller and more efficient equipment that simplified private networks.

While private networks imply an isolated network for selected devices that are allowed to connect on to the network, Non-Public Networks are much broader in scope. Chief among them is the ability of certain devices to be capable of working on Private as well as Public Network or roaming between them.

I recently ran a workshop on 'Introduction to Private 4G & 5G Networks' with a well known Industry analyst Dean Bubley. One of the sections looked at the Network Architecture based on the 3GPP standards. This tutorial is a part of that particular section. Slides and video embedded below. There are also some interesting videos on YouTube that show how and why Private Networks are needed and some use cases. The playlist is embedded in the end.






Playlist of Private Networks Use Cases.



Related Posts:

Thursday, 27 February 2020

5G and Industry 4.0


Telef├│nica published an infographic on 'Benefits of 5G in Industry 4.0' last week. You can download it on their website here. This reminded me that we have now completed the third video in our series of IoT.

  1. The beginners guide to M2M, MTC & IoT is discussed here and video is available here.
  2. Industrial IoT (IIoT) vs IoT is discussed here.
  3. This blog post with with embedded video / slide looks at Industrie 4.0 (a.k.a. I4.0 or I4)



Slides and Video is embedded below, let us know what you think.






Related Posts and Links:

Friday, 21 February 2020

EPS Fallback in 5G Standalone Deployments

It can be expected that later this year some mobile network operators will launch their initial 5G standalone (5G SA) deployments.

Nevertheless there will remain areas with temporary or permanently weak 5G NR coverage. One possible reason might be that even when 5G and LTE antennas are co-located, which means: mounted at the same remote radio head, the footprint of the 5G NR cell is significantly smaller when it uses a higher frequency band than LTE - see figure 1.

Figure 1: Smaller footprint of co-located 5G NR cell with higher frequency
Especially UEs making Voice over New Radio (VoNR) calls from the 5G cell edge have a high risk of experiencing bad call quality, in worst case a call drop. To prevent this the UE is forced  during the voice call setup towards 5G core network (5GC) to switch to a LTE/EPS connection where the radio conditions are better for the voice service.

The same procedure for which the term "EPS Fallback" was coined by 3GPP also applies when the UE is served by a 5G cell that is not configured/not optimized for VoNR calls or when the UE does not have all needed VoNR capabilities.

Figure 2: Two options for EPS fallback

When looking at the RAN there are two options for executing the EPS Fallback as shown in figure 2.

In option A the 5G radio connection is released after the initial call attempt is successfully finished and with the 5G RRC Release the UE is ordered to reselect to a 4G cell where a new radio connection is started for the VoLTE call. In this case the UE context is transferred from the AMF to the MME over the N26 interface. 3GPP seems to use also the term "RAT fallback" for this option.

Option B is to perform a 5G-4G inter-RAT handover. Here the session management and user plane tunnels in the core network are handed over from SMF/UPF to MME/S-GW in addition. This is realized with the GTPv2 Forward Relocation procedure on N26 interface.

All in all the EPS fallback is expected to cause an additional call setup delay of approximately 2 seconds.

For the inter-RAT handover case it is easy to detect from signaling information that an EPS fallback was triggered. In the source-eNodeB-to-target-eNodeB-transparent-container sent by the gNB to the eNB a boolean "IMS voice EPS fallback from 5G" indicator will be found that is set to "true". This container is named according to the receiving entity and will be carried by the NGAP Handover Preparation, GTPv2 Forward Relocation Request and the S1AP Handover Request messages.

If a redirection for Voice EPS Fallback is possible or not is indicated in the NGAP Initial Context Setup Request, Handover Request (during 5G intra-system handover) and Path Switch Request Acknowledge (after Xn handover) messages, all sent by the AMF to the gNB.

Further the NGAP protocol provides the cause value "IMS voice EPS fallback or RAT fallback triggered" in the PDU Session Resource Modify Response message indicating that a requested VoNR session cannot be established.  





Wednesday, 12 February 2020

AI your Slice to 5G Perfection


Back in November, The Enhanced Mobile Broadband Group in CW (Cambridge Wireless) held an event on 'Is automation essential in 5G?'. There were some thought provoking presentations and discussions but the one that stood out for me was by Dan Warren from Samsung


The slides are embedded below but I want to highlight these points:
  • Some Network Functions will be per slice whereas others will be multi-slice, the split may not be the same for every slice
  • Two slices that have the same 'per slice vs multi-slice' functional split may be different network hardware topologies
  • Enterprise customers will likely want a 'service' contract that has to be manifested as multiple slices of different types. 
  • Physical infrastructure is common to all slices
The last point is very important as people forget that there is a physical infrastructure that will generally be common across all slices.

Again, when you apply Artificial Intelligence (AI) to optimize the network functions, does it do it individually first and then end-to-end and if this is applied across all slices, each of which may have a different functionality, requirement, etc. How would it work in practice?




As Dan says in his tweet, "It is hard to implement AI to optimise a point solution without potentially degrading the things around it.  Constantly being pushed to a bigger picture view => more data => more complexity"

Let me know what you think.

Related Posts:

Friday, 31 January 2020

Prof. Andy Sutton: Backhauling the 5G Experience - Jan 2020


Prof. Andy Sutton has shared quite a few presentations and talks on this blog. His presentations from the annual 'The IET 5G Seminar' has made it to the top 10 for the last 3 years in a row. His talk from 2019, 2018 & 2017 is available for anyone interested.

The title of this year's conference was '5G 2020 - Unleashed'. The details are available here and the video of all the talks are here. As always, the slides and video is embedded below.

Slides



Video


There are a lot of bands that keep on getting mentioned, especially in relation to backhaul. Here is a summary of these bands that would come handy.



Related Posts:

Sunday, 26 January 2020

NTT Docomo's Vision on 5G Evolution and 6G


NTT Docomo released a whitepaper on 5G Evolution and 6G. In a press release they announced:

NTT DOCOMO has released a white paper on the topic of 6G, the sixth-generation mobile communications system that the company aims to launch on a commercial basis by 2030. It incorporates DOCOMO's views in the field of 5G evolution and 6G communications technology, areas that the company has been researching since 2018. The white paper summarizes the related technical concepts and the expected diverse use cases of evolving 5G and new 6G communication technologies, as well as the technology components and performance targets.

Mobile communication systems typically evolve into the next generation over a period of roughly ten years; DOCOMO commenced its research into the commercial launch of 5G in 2010. In 2018, the company conducted successful radio wave propagation experiments at frequencies of up to 150 GHz, levels which are expected to enable the much faster and larger-capacity communications that 6G will require.

DOCOMO will continue to enhance the ultra-high-speed, large-capacity, ultra-reliable, low-latency and massive device-connectivity capabilities of 5G technology. It will continue its research into and development of 5G evolution and 6G technology, aiming to realize technological advances including:

  • the achievement of a combination of advances in connectivity, including ultra-high speed, large capacity and low latency
  • the pioneering of new frequency bands, including terahertz frequencies
  • the expansion of communication coverage in the sky, at sea and in space
  • the provision of ultra-low-energy and ultra-low-cost communications
  • the ensuring of highly reliable communications
  • the capability of massive device-connectivity and sensing

Visitors to DOCOMO Open House 2020 will be able to view conceptual displays incorporating DOCOMO's vision of the evolution of 5G technologies into 6G. The event will take place in the Tokyo Big Sight exhibition complex in Tokyo on January 23 and 24. DOCOMO also plans to hold a panel session entitled "5G Evolution and 6G" on January 24.

Videos from Docomo Open House are embedded below, along with a previous talk by Takehiro Nakamura from 6G Summit.


6G has become a hot topic, especially after China announced back in November that they are working on 6G. We have some interesting tweets on 6G as well.

This one from Stefan Pongratz, Dell'Oro group shows the timeline for 5G, Pre-6G and 6G



This one provides a timeline all the way from Release 99 up till 21



Finally, here is a tweet highlighting the 6G research



Finally, the paper acknowledges the 5G challenges and focus areas for 5G evolution, before focusing on 6G.
The mmWave coverage and mobility needs improvement, while the downlink is able to provide very high data rates, the uplink is struggling to be better than 4G. Also, there are some very extreme requirements for industrial use cases, 5G has yet to prove that it can meet them.

Finally, here is another view from iDate Digiworld comparing 5G vs 6G in terms of performance, spectrum and network.



Related Posts:

Tuesday, 21 January 2020

How MOCN RAN-Sharing Works


Shared RAN deployment scenarios are an excellent opportunity for mobile network operators to lower their investments on both, network hardware and operational costs by sharing resources.

The MORAN approach where each operator continues to have its dedicated spectrum (= radio network cells) is easy to understand.

However, the Multi-Operator Core Network (MOCN) is a bit more complex, especially if one of the involved operators asks for service assurance KPIs that apply to its - and only its - subscribers. In this case it is a prerequisite to find out which "call" belongs to which core network operator to enable further KPI correlation and aggregation.

The figure below illustrates how this works:

(click on picture for larger version)

In the System Information Block (SIB) 1 of the cell a list of PLMN-IDs is broadcasted followed by a single Tracking Area Code (which can be combined each of the PLMN-IDs to get multiple TAIs) and a single Cell Identity.

Encoding is specified in 3GPP 36.331 (RRC) as follows:

SystemInformationBlockType1 ::=     SEQUENCE {
    cellAccessRelatedInfo              SEQUENCE {
       plmn-IdentityList                 PLMN-IdentityList,
       trackingAreaCode                  TrackingAreaCode,
       cellIdentity                      CellIdentity,

The spec further defines that the ECGI is the CellIdentiy combined with the first (!!!) PLMN-ID from the PLMN-ID List:

CellGlobalIdEUTRA field descriptions
cellIdentity
Identity of the cell within the context of the PLMN.
plmn-Identity
Identifies the PLMN of the cell as given by the first PLMN entry in the plmn-IdentityList in SystemInformationBlockType1.

So there is one and only 1 ECGI per radio cell in the network, but multiple PLMN-IDs and hence, multiple TAI, one fore each core network operator, are broadcasted.

During RRC establishement a particular UE signals on behalf on the selected PLMN-ID information element in the RRC Connection Setup Complete message to which core network operator shall be used.

This information is "translated" by the eNB into ECGI and TAI with different PLMN-IDs. While the ECGI displays the PLMN-ID of the operator that owns the RAN equipment the TAI shows the selected PLMN-ID of the UE's core network operator. 

Sunday, 19 January 2020

2-step RACH Enhancement for 5G New Radio (NR)

5G Americas recently published a white paper titled, "The 5G Evolution: 3GPP Releases 16-17" highlighting new features in 5G that will define the next phase of 5G network deployments across the globe. It's available here. One of the sections in that details the 2-step RACH enhancement that is being discussed for a while in 3GPP. The 2-step process would supercede the 4-step process today and would reduce the lartency and optimise the signalling.


Here are the details from the 5G Americas whitepaper:

RACH stands for Random Access Channel, which is the first message from UE to eNB when it is powered on. In terms of Radio Access Network implementation, handling RACH design can be one of the most important / critical portions.
The contention-based random-access procedure from Release 15 is a four-step procedure, as shown in Figure 3.12. The UE transmits a contention-based PRACH preamble, also known as Msg1. After detecting the preamble, the gNB responds with a random-access response (RAR), also known as Msg2. The RAR includes the detected preamble ID, a time-advance command, a temporary C-RNTI (TC-RNTI), and an uplink grant for scheduling a PUSCH transmission from the UE known as Msg3. The UE transmits Msg3 in response to the RAR including an ID for contention resolution. Upon receiving Msg3, the network transmits the contention resolution message, also known as Msg4, with the contention resolution ID. The UE receives Msg4, and if it finds its contention-resolution ID it sends an acknowledgement on a PUCCH, which completes the 4-step random access procedure.

The four-step random-access procedure requires two round-trip cycles between the UE and the base station, which not only increases the latency but also incurs additional control-signaling overhead. The motivation of two-step RACH is to reduce latency and control-signaling overhead by having a single round trip cycle between the UE and the base station. This is achieved by combining the preamble (Msg1) and the scheduled PUSCH transmission (Msg3) into a single message (MsgA) from the UE, known as MsgA. Then by combining the random-access respond (Msg2) and the contention resolution message (Msg4) into a single message (MsgB) from the gNB to UE, see Figure 3.13. Furthermore, for unlicensed spectrum, reducing the number of messages transmitted from the UE and the gNB, reduces the number of LBT (Listen Before Talk) attempts.

Design targets for two-step RACH:

  • A common design for the three main uses of 5G, i.e. eMBB, URLLC and mMTC in licensed and unlicensed spectrum.
  • Operation in any cell size supported in Release 15, and with or without a valid uplink time alignment (TA).
  • Applicable to different RRC states, i.e. RRC_INACTIVE, RRC_CONNECTED and RRC_IDLE states.
  • All triggers for four-step RACH apply to two-step RACH including, Msg3-based SI request and contention-based beam failure recovery (CB BFR).

As described earlier, MsgA consists of a PRACH preamble and a PUSCH transmission, known as MsgA PRACH and MsgA PUSCH respectively. The MsgA PRACH preambles are separate from the four-step RACH preambles, but can be transmitted in the same PRACH Occasions (ROs) as the preambles of fourstep RACH, or in separate ROs. The PUSCH transmissions are organized into PUSCH Occasions (POs) which span multiple symbols and PRBs with optional guard periods and guard bands between consecutive POs. Each PO consists of multiple DMRS ports and DMRS sequences, with each DMRS port/DMRS sequence pair known as PUSCH resource unit (PRU). two-step RACH supports at least one-to-one and multiple-to-one mapping between the preambles and PRUs.

After the UE transmits MsgA, it waits for the MsgB response from the gNB. There are three possible outcomes:

  1. gNB doesn’t detect the MsgA PRACH ➡ No response is sent back to the UE ➡ The UE retransmits MsgA or falls back to four-step RACH starting with a Msg1 transmission.
  2. gNB detects MsgA preamble but fails to successful decode MsgA PUSCH ➡ gNB sends back a fallbackRAR to the UE with the RAPID (random-access preamble ID) and an uplink grant for the MsgA PUSCH retransmission ➡ The UE upon receiving the fallbackRAR, falls back to four-step RACH with a transmission of Msg3 (retransmission of the MsgA PUSCH).
  3. gNB detects MsgA and successfully decodes MsgA PUSCH ➡ gNB sends back a successRAR to the UE with the contention resolution ID of MsgA ➡ The reception of the successRAR successfully completes the two-step RACH procedure.

As described earlier, MsgB consists of the random-access response and the contention-resolution message. The random-access response is sent when the gNB detects a preamble but cannot successfully decode the corresponding PUSCH transmission. The contention resolution message is sent after the gNB successfully decodes the PUSCH transmission. MsgB can contain backoff indication, fallbackRAR and/or successRAR. A single MsgB can contain the successRAR of one or more UEs. The fallbackRAR consists of the RAPID: an uplink grant to retransmit the MsgA PUSCH payload and time-advance command. The successRAR consists of at least the contention resolution ID, the C-RNTI and the TA command.

For more details on this feature, see 3GPP RP-190711, “2-step RACH for NR” (Work-item description)

Tuesday, 14 January 2020

EN-DC SRB3 Demystified


3GPP 37.340 says that it is up the secondary node to establish "SRB3", but what exactly does this mean and how is it done?

Simple answer: The establishment of a signaling radio bearer (SRB) 3 in EN-DC mode means that RRC Measurement Reports for NR quality can be sent directly to the SgNB. This enables the 5G node to make intra-SgNB handover decisions and start the handover execution without involving the master eNodeB of the connection.

To prevent confusion the figure below shows a simplified scenario in which the Complete/Acknowledgement messages are not mentioned although they will be seen in the message flow.

A prerequisite is the successful addition of 5G radio resources as described in an earlier blog post. After this is completed the UE in the example transmits user plane information over the NR cell with the physical cell ID (PCI) = 12. In the transport network this cell is identified by NR CGI = xxxx52 (where „xxxx“ stands for a valid PLMN-ID and gNodeB-ID).

In the figure below the SgNB sends a X2AP SgNB Modification Required message that carries an embedded NR RRC cG-Config message. This cG-Config message is transparently forwarded by the MeNB to the UE. When arriving at the UE it activates CSI reference signal measurements on the 5G frequency including the serving 5G cell as well as its neighbors. It shall be noticed that here the concept of the Special Cell (SpCell) applies as it was defined for LTE-A CoMP scenarios. 

Instead of the X2AP SgNB Modification Required message the information for activating the CSI reference signal measurements can alternatively transported using the X2AP SgNB Addition Request Acknowledge or X2AP SgNB Change Required message.

In step 2 the UE sends a NR RRC (3GPP 38.331) Measurement Report that indicates a stronger 5G cell (the neighbor cell with PCI = 11) was measured. It might be a vendor-specific implementation to send this NR RRC Measurement Report simultaneously over uplink channels of the LTE radio link where it is carried by the LTE RRC Uplink Information Transfer MRDC (Multi-RAT Dual Connectivity) as well as over NR radio links where it is forwarded by the SgNB to the MeNB embedded in a X2AP RRC Transfer message.

Indeed, it is the SgNB that makes the handover decision, but since the MeNB is in charge of the signaling connection the handover command (here: another NR RRC cG-Config message that orders to switch the 5G radio link to the cell with PCI = 11) must be transmitted to the MeNB by using another X2AP SgNB Modification Required message.

After the UE received the NR CC cG-Config message sent by the SgNB the HO is executed and the 5G cell with PCI = 11 becomes the new primary secondary cell of the EN-DC connection.


Figure: Measurement Configuration, Reporting and Execution for intra-SgNB  Handover 

Sunday, 5 January 2020

Free 5G Training


Many readers of this blog would be aware that I run 5G 'An Advanced Introduction to 5G Technology' training course for Cambridge Wireless at regular intervals. The next one is on 10th March 2020, in Cambridge. In fact I am also running a 'Introduction to Private 4G & 5G Networks' workshop on 4th Feb 2020 in London.

Many people ask me if they I have an online course available. While I haven't, I have quite a few videos on 3G4G YouTube channel and also have a 3G4G training page. People (mainly students or newbies) still ask me what sequence of videos they should go through, etc. So to make everyone's life simple, I created 2 YouTube playlists. Both are embedded below for ease.

Part 1. This is for people who know basic telecommunications theory and don't know much about mobile technology in general




Part 2. This is for people who understand 2G/3G/4G basics and want to learn about 5G.


I will add/remove/update videos when we add new videos on our channel. Feel free to skip videos if you already know a topic. There is quite a lot of other information on the 3G4G YouTube channel if you want to explore more

Where do you go after you have watched these videos? Go to the 3GPP homepage and start looking at specifications, news, etc. You can also start looking at the specifications on 3G4G page here.

Hopefully this is a good starting point.

SEE ALSOhttps://www.free5gtraining.com/