Monday, 6 July 2020

A Technical Introduction to 5G NR RRC Inactive State


I looked at the RRC Inactive state back in 2017, but the standards were not completely defined. In the meantime standards have evolved and commercial 5G networks are rolling out left, right and centre. I made a short technical introduction to the RRC_INACTIVE state, comparing it with the 4G states in RRC and NAS. I also looked at some basic signalling examples and there are lots of relevant references at the end. Video and slides embedded below.






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Saturday, 4 July 2020

An Introduction to Vehicle to Everything (V2X) and Cellular V2X (C-V2X)


We made an introductory tutorial explaining vehicle to everything. There are 2 different favours of V2X as shown in this tweet below


One is based on IEEE 802.11p (802.11bd in future). It is known by different names, DSRC, ITS-G5, etc. The other is the cellular V2X or C-V2X. It started as basic D2D but has evolved over the time. The slides and video are embedded below but this topic will need revisiting with more details.







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Tuesday, 30 June 2020

A Look into 5G Virtual/Open RAN - Part 6: Inter-gNB CU Handover involving Xn

In previous blog posts I have discussed intra-gNB-DU handover and inter-gNB-DU handover scenarios.Now it is time to look at inter-gNB-CU handover that uses the Xn interface.

At the RRC protocol layer there will be the measurement setups and measurement reports as in the intra-gNB handover cases. And F1AP UE Context Setup and Release Procedures are identical with the ones discussed for inter-gNB-DU handover. Only the cause values are expected to be different, e.g. "successful handover".

Thus, I do not want to  focus here on la adder diagram call flow (that is by the way very well described in 3GPP 38.401, chapter 8.9.4), but invite you to have a look at a "big picture" that you see below.

(click image to enlarge)

What characterizes the inter-gNB handover is the transfer of the UE RRC/NGAP context form the source gNB-CU to the target gNB-CU. When the Xn interface is available to connect two neighbor gNBs this context transfer is executed using the XnAP Handover Preparation procedure. The Initiating Message of this procedure transfers the UE context parameters to the target gNB-CU. Then embedded in the Successful Outcome message the handover command is sent in return to the source gNB-CU that forwards it to the UE. In addition a temporary user plane transport tunnel for the purpose of data forwarding is established and later on released on the Xn user plane interface.

Once the UE performed the handover on the radio interface all the transport tunnels for the payload transmission need to be switched from the old gNB to the new one. This includes the tunnel to the UPF that is managed by the NGAP. Thus, the target gNB-CU starts the NGAP Path Switch procedure. 

In the target gNB environment it is necessary to establish a new F1AP UE context, new E1AP Bearer Context and new F1-U payload transport tunnel. All this happens BEFORE the Handover Command is sent to the source gNB/UE. And once there is an indication that the handover is completed all the radio and transport resources controlled by the source gNB will be released.

So the figure above looks complicated, but actually the underlying logic of context/data forwarding, radio resource allocation and transport tunnel switching is quite simple.

Special note: In case there is no Xn interface available the UE context/handover information can be transmitted using NGAP Handover Preparation procedure on the source side of the connection and NGAP Handover Resource Allocation procedure on the target side of the connection.

Tuesday, 23 June 2020

Comparison Layer 2 Measurements LTE vs. 5G NR


Yesterday (2020-06-22) 3GPP uploaded the version 1.0 of TS 38.314 "Layer 2 Measurements" for 5G New Radio Rel. 16.

I was wondering about the difference compared to the same LTE standard defined in 3GPP TS 36.314.

The initial look at the table of contents shows significantly less measurements in the NR spec, but a new counter for the number of stored inactive UE contexts. This is due to the introduction of RRC Inactive state in NR RRC specified in 3GPP TS 38.331)

All other differences in the NR standard are related to chapter number 4.2.1.6 "Other measurements defined in TS 28.552".

Here one finds the references to Data Volume, Average Throughput Measurement per UE and DRB as well as PRB usage measurements.

Adding these additional measurements to the list we see in the table of contents it emerges that indeed the number of stored inactive UE contexts is the only major difference in comparison with the LTE standard. 

Monday, 22 June 2020

Carrier Aggregation (CA) and Dual Connectivity (DC)


This topic keeps coming up every few months with either someone asking me for clarifications or someone asking us to make a video. While I don't think I will mange to get round to making a video sometime soon, there are some excellent resources available that should help a new starter. Here they are in an order I think works best



The first resource that I think also works best is this webinar / training from Award Solutions. It covers this topic well and the image at the top of the post is a god summary for someone who already understands the technology.


It may also help to understand that in the 5G NSA can have 4G carrier aggregation as well as 5G carrier aggregation in addition to dual connectivity.


If you saw the video earlier, you noticed that DC actually came as part of LTE in Release-12. We covered it in our Telecom Infrastructure blog here. NTT Docomo Technical journal had a detailed article on 'Carrier Aggregation Enhancement and Dual Connectivity Promising Higher Throughput and Capacity' that covered DC in a lot more technical detail, albeit from LTE point of view only. The article is available here. A WWRF whitepaper from the same era can also provide more details on LTE Small Cell Enhancement by Dual Connectivity. An archived copy of the paper is available here.

Another fantastic resource is this presentation by Rapeepat Ratasuk and Amitava Ghosh from Mobile Radio Research Lab, Nokia Bell Labs. The presentation is available here and details the MCG (Master Cell Group) Split Bearer and SCG (Secondary Cell Group) Split Bearer, etc. This article from Ericsson also provides more detail on this topic while ShareTechNote takes it one level even deeper with technical details and signalling here and here.

So hopefully this is a good detailed starting point on this topic, until we manage to make a simple video someday.

Friday, 12 June 2020

A Look into 5G Virtual/Open RAN - Part 5: Inter-gNB DU Handover

My last blog post discussed the intra-gNB-DU handover. Now it is time to look at inter-gNB-DU handover. This means: the target cell is located in the same gNB, but connected to a different gNB Distributed Unit (gNB-DU) than the source cell.

The figure below shows the message flow:

(Click on the image to enlarge)

As you can see it was not so easy to show all the messages in one flow chart and again I have simplified things a little bit. So it is not shown that NR RRC messages are transparently forwarded by the gNB-DU when sent to or received from the UE.

It should also be noted that between step 8 and 9 the UE performs a random access procedure on the radio interface that is also not shown.

Beside this the RRC measurement configuration and measurement report is identical with the same procedure in the intra-gNB-DU handover case (step 1+2)

However, due to the fact the target cell is connected to a different gNB-DU a new F1AP UE context must be established on the incoming F1-C leg (step 3+4). As in a new connection setup scenario the target gNB-DU provides all necessary lower layer parameters for the target cell radio link including a new c-RNTI.

Since we need also a new user plane transport tunnel to exchange payload on the F1-U interface between the target gNB-DU and the gNB-CU UP an E1AP Bearer Context Modification procedure is performed in step 5+6.

The following F1AP UE Context Modification Request is used to transmit the handover command (NR RRC Reconfiguration message with target cell parameters) towards the UE (step 7). In step 8 the F1AP UE Context Modification Response confirms that the handover command was forwarded to the UE.

After successful random access the UE sends NR RRC Reconfiguration Complete message on the new radio link (step 9) and this triggers the F1AP UE Context Release procedure on the outgoing F1-C leg.

Tuesday, 9 June 2020

5G Roaming with SEPP (Security Edge Protection Proxy)

SEPP (Security Edge Protection Proxy) is part of the roaming security architecture as shown in the figure above. Ericsson's article, "An overview of the 3GPP 5G security standard" describes the use of SEPP as follows:

The use of SBA has also pushed for protection at higher protocol layers (i.e. transport and application), in addition to protection of the communication between core network entities at the internet protocol (IP) layer (typically by IPsec). Therefore, the 5G core network functions support state-of-the-art security protocols like TLS 1.2 and 1.3 to protect the communication at the transport layer and the OAuth 2.0 framework at the application layer to ensure that only authorized network functions are granted access to a service offered by another function.

The improvement provided by 3GPP SA3 to the interconnect security (i.e. security between different operator networks) consists of three building blocks:

  • Firstly, a new network function called security edge protection proxy (SEPP) was introduced in the 5G architecture (as shown in figure 2). All signaling traffic across operator networks is expected to transit through these security proxies
  • Secondly, authentication between SEPPs is required. This enables effective filtering of traffic coming from the interconnect
  • Thirdly, a new application layer security solution on the N32 interface between the SEPPs was designed to provide protection of sensitive data attributes while still allowing mediation services throughout the interconnect

The main components of SBA security are authentication and transport protection between network functions using TLS, authorization framework using OAuth2, and improved interconnect security using a new security protocol designed by 3GPP.

NG.113 5G Roaming Guidelines v2.0 clarifies:

4.2 Inter PLMN (N32) Interface

The Inter-PLMN specification 3GPP TS 29.573 has been produced by 3GPP to specify the protocol definitions and message flows, and also the APIs for the procedures on the PLMN (Public Land Mobile Network) interconnection interface (i.e. N32)

As stated in 3GPP TS 29.573 the N32 interface is used between the SEPPs of a VPLMN and a HPLMN in roaming scenarios. Furthermore, 3GPP has specified N32 to be considered as two separate interfaces: N32-c and N32-f.

N32-c is the Control Plane interface between the SEPPs for performing the initial handshake and negotiating the parameters to be applied for the actual N32 message forwarding. See section 4.2.2 of 3GPP TS 29.573.

Once the initial HTTP/2 handshake is completed the N32-c connection is torn down. This connection is End-to-End between SEPPs and does not involve IPX to intercept the HTTP/2 connection; although the IPX may be involved for IP level routing.

N32-f is the Forwarding interface between the SEPPs, that is used for forwarding the communication between the Network Function (NF) service consumer and the NF service producer after applying the application level security protection. See section 4.2.3 of 3GPP TS 29.573.

N32-f can provide Application Level Security (ALS) as specified in 3GPP TS 33.501 between SEPPs, if negotiated using N32-c. ALS provides the following protection functionalities: -

  • Message protection of the information exchanged between NF service consumer and producer
  • Forwarding of the application layer protected message from a SEPP in one PLMN to another PLMN by way of using IPX providers on the path. The IPX providers on the path may involve the insertion of content modification instructions which the receiving SEPP applies after verifying the integrity of such modification instructions.

The HTTP/2 connection used on N32-f is long lived; and when a SEPP establishes a connection towards another PLMN via IPX, the HTTP/2 connection from a SEPP terminates at the next hop IPX.

N32-f makes use of the HTTP/2 connection management requirements specified in 3GPP TS 29.500. Confidentiality protection shall apply to all IE’s for the JOSE protected message forwarding procedure, such that hop-by-hop security between SEPP and the IPXs should be established using an IPSec or TLS VPN.

If an IPX is not in the path between SEPPs, then an IPSec of Transport Layer Security, TLS VPN will be established directly.

Note: N32-f shall use “http” connections generated by a SEPP, and not “https”

The SEPP will act as a non-transparent Proxy for the NF’s when service based interfaces are used across PLMNs, however inside IPX service providers, an HTTP proxy may also be used to modify information elements (IE’s) inside the HTTP/2 request and response messages.

Acting in a similar manner to the IPX Diameter Proxy used in EPC roaming, the HTTP/2 Proxy can be used for inspection of messages, and modification of parameters. 


The picture in the tweet above shows how SEPP will play a role in Local Break Out (LBO) roaming as well as Home Routed (HR) roaming.

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Tuesday, 2 June 2020

Embedded SIM (eSIM) and Integrated SIM (iSIM)

It's been a while since I wrote detailed posts explaining UICC and SIM cards. Since then the SIM cards have evolved from Mini SIM to Micro SIM and Nano SIM. They are evolving even further, especially for M2M / IoT devices as embedded SIM (eSIM or eUICC) and integrated SIM (iSIM).


Embedded SIMs (eSIMs) or embedded Universal Integrated Circuit Cards (eUICCs) are physical SIMs that are soldered into the device and enable storage and remote management of multiple network operator profiles (remote SIM provisioning). The form factor of eSIM is known as MFF2.

The integrated SIMs (iSIMs) moves the SIM from a separate chip into a secure enclave alongside the application processor and cellular radio on a purpose-built system on a chip (SoC).

We made a short tutorial explaining UICC & SIM and then looking at eSIM, iSIM and how remote SIM provisioning works. The video and slides are embedded below. The slides contain a lot of useful links for further reading.







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Friday, 29 May 2020

Visualisation of Intra-gNB Handover in an End-to-End Monitoring Tool


In my last blog post I described the message flow of an intra-gNB-DU handover.

Today I want show how such a handover can be visualized using a ladder diagram in an end-to-end passive monitoring tool. The tool shown in the figure below is the NETSCOUT nGenious Session Analyzer (nSA).

The data source is a cell trace feed according to 3GPP 32.421/32.423. Unfortunately F1AP and E1AP messages are missing in the trace so that we cannot distinguish if this is an intra- or inter-gNB DU handover.

(click to enlarge)

Nevertheless the tool offers the great advantage to find the handover procedure quickly within all the other messages of the trace. It also links the outgoing (source) and incoming (target) side in case that different feeds from different cells need to be combined.

For the NR RRC messages are send/received by the UE, but there is a good reason to show the icon "Cell" on top the ladder diagram. With this approach it is possible to spot immediately the changing cell location of the UE and NR RRC Reconfiguration procedure that is used to execute the handover. So the icon does not represent a cell, but an UE within a cell - and with a bit imagination you can recognize this in the icon graphic itself.

Selecting the handover message it is possible to open the Inline Decode tab and browse through the bits and bytes of NR RRC. As expected beside many other parameters the new UE Identity (new C-RNTI) to be used by the UE after arriving in the target cell is one of the most important information elements and confirms that this particular NR RRC Reconfiguration message is indeed the command for executing the intra-gNB handover.

Tuesday, 26 May 2020

The Journey from Communications Service Provider (CSP) to Digital Service Provider (DSP)

Reliance Jio has recently been called as India's first digital service provider (DSP), but what exactly is a DSP and how does an existing mobile network transform from the traditional communications service provider (CSP) to a DSP?

Service Providers are also known as Telecommunications Service Provider (TSP) or Communications Service Provider (CSP). Basically, they refer to someone who provides services.

Mobile Network Operators (MNOs) are also referred to as Mobile Service Providers (MSPs) or Wireless Service Providers (WSPs). Even though CSP is a generic term, it generally always refers to MSP.

The term “Digital Service Provider" applies to any company that distributes media online. In the case of telcos, it's an organization that has moved on from offering core, traditional telecom services, to providing mobile broadband access, services, content and apps, all sold directly from the device.

Analysys Mason provides this simple equation to explain how a CSP can transform into DSP


Another way of representing this is to compare CSP & DSP as shown in the table below

We made a tutorial on this topic, the slides and video is embedded below. If you want to jump directly to the DSP part, move to 2:35 in the video.





Finally, another term that gets thrown around often confuses people is Telco & Netco


Telco stands for Telecommunications Company, which basically means Mobile Network Operator.

NetCo or Network cooperation is the practice of a Mobile Network Operator (MNO) sharing part of its Radio Access Network (RAN) with another MNO.

There are other terms like Towerco & Infraco that probably deserve their own post.


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Tuesday, 19 May 2020

5G Dynamic Spectrum Sharing (DSS)

5G Dynamic Spectrum Sharing is a hot topic. I have already been asked about multiple people for links on good resources / whitepapers. So here is what we liked, feel free to add anything else you found useful as part of comments.


Nokia has a nice high level overview of this topic which is available here. I really liked the decision tree as shown in the tweet above. I am going to quote a section here that is a great summary to decide if you want to dive deeper.

DSS in the physical layer
DSS allows CSPs to share resources dynamically between 4G and 5G in time and/or frequency domains, as shown on the left of Figure 3. It’s a simple idea in principle, but we also need to consider the detailed structure at the level of the resource block in order to understand the resource allocations for the control channels and reference signals. A single resource block is shown on the right side of Figure 3.

The 5G physical layer is designed to be so similar to 4G in 3GPP that DSS becomes feasible with the same subcarrier spacing and similar time domain structure. DSS is designed to be backwards compatible with all existing LTE devices. CSPs therefore need to maintain LTE cell reference signal (CRS) transmission. 5G transmission is designed around LTE CRS in an approach called CRS rate matching.

5G uses demodulation reference signals (DMRS), which are only transmitted together with 5G data and so minimize any impact on LTE capacity. If all LTE devices support Transmission Mode 9 (TM9), then the shared carrier has lower overheads because less CRS transmission is required. The control channel transmission and the data transmission can be selected dynamically between LTE and 5G, depending on the instantaneous capacity requirements.


The second resource is this Rohde & Schwarz webinar here. As can be seen in the tweet above, it provides nice detailed explanation.

Finally, we have a Comprehensive Deployment Guide to Dynamic Spectrum Sharing for 5G NR and 4G LTE Coexistence, which is a nice and detailed whitepaper from Mediatek. Quoting a small section from the WP for anyone not wanting to go too much in deep:

The DSS concept is based on the flexible design of NR physical layer. It uses the idea that NR signals are transmitted over unused LTE resources. With LTE, all the channels are statically assigned in the time-frequency domain, whereas the NR physical layer is extremely flexible for reference signals, data and control channels, thus allowing dynamic configurations that will minimize a chance of collision between the two technologies. 

One of the main concepts of DSS is that only 5G users are made aware of it, while the functionalities of the existing LTE devices remain unaffected (i.e. LTE protocols in connected or idle mode). Therefore, fitting the flexible physical layer design of NR around that of LTE is needed in order to deploy DSS on a shared spectrum. This paper discusses the various options of DSS implementation, including deployment challenges, possible impacts to data rates, and areas of possible improvements.

NR offers a scalable and flexible physical layer design depicted by various numerologies. There are different subcarrier spacing (SCS) for data channels and synchronization channels based on the band assigned. This flexibility brings even more complexity because it overlays the NR signals over LTE, which requires very tight coordination between gNB and eNB in order to provide reliable synchronization in radio scheduling.

The main foundation of DSS is to schedule NR users in the LTE subframes while ensuring no respective impact on LTE users in terms of essential channels, such as reference signals used for synchronization and downlink measurements. LTE Cell Reference Signals (CRS) is typically the main concept where DSS options are designated, as CRS have a fixed time-frequency resource assignment. The CRS resources layout can vary depending on the number of antenna ports. More CRS antenna ports leads to increased usage of Resource Elements (REs). CRS generates from 4.76% (1 antenna port) up to 14.29% (4 antenna ports) overhead in LTE resources. As CRS is the channel used for downlink measurements, avoiding possible collision with CRS is one of the foundations of the DSS options shown in figure 1. The other aspect of DSS design is to fit the 5G NR reference signals within the subframes in a way to avoid affecting NR downlink measurements and synchronization. For that, DSS considers the options shown in figure 1 to ensure NR reference signals such as Synchronization Signal Block (SSB) or Demodulation Reference Signal (DMRS) are placed in time-frequencies away from any collision with LTE signals.

MBSFN, option 1 in figure 1, stands for Multi-Broadcast Single-Frequency Network and is used in LTE for point-to-multipoint transmission such as eMBMS (Evolved Multimedia Broadcast Multicast Services). The general idea of MBSFN is that specific subframes within an LTE frame reserve the last 12 OFDM symbols of such subframe to be free from other LTE channel transmission. These symbols were originally intended to be used for broadcast services and are “muted” for data transmission in other LTE UE. Now this idea has been adjusted for use in a DSS concept, so that these reserved symbols are used for NR signals instead of eMBMS. While in general LTE PDCCH can occupy from 1 to 3 symbols (based on cell load), the first two OFDM symbols of such MBSFN subframe are used for LTE PDCCH, and DSS NR UE can use the third symbol. Using MBSFN is completely transparent to legacy LTE-only devices from 3GPP Release 9 onwards, as such LTE UE knows that these subframes are used for other purposes. In this sense this is the simplest way of deploying DSS. This method has disadvantages though. The main one is that if MBSFN subframes are used very frequently and it takes away resources from LTE users, heavily reducing LTE-only user throughput. Note that option 1 shown in figure 1 does not require LTE MBSFN Reference Signals to be used, because the MBSFN subframe is used to mute the subframe for DSS operation only, and LTE CRS shall only be transmitted in the non-MBSFN region (within the first two symbols) of the MBSFN subframe.

The two other options illustrated in figure 1 are dealing with non-MBSFN subframes that contain LTE reference signals. Option 2 is ‘mini-slot’ based; mini-slot scheduling is available in NR for URLLC applications that require extremely low latency. The symbols can be placed anywhere inside the NR slot. In respect to DSS, mini-slot operation just eliminates the usage of the symbols that contain LTE CRS and schedule only free ones for NR transmission. The basic limitation of this method comes from the concept itself. It is not very suitable for eMBB applications as too many resources are outside of NR scheduling. However it still can be utilized in some special cases like 30 kHz SSB insertion which will be described later in this paper.

Option 3 is based on CRS rate matching in non-MBSFN subframes, and it is expected to be the one most commonly used for NR data channels. In this option, the UE performs puncturing of REs used by LTE CRS so that the NR scheduler knows which REs are not available for NR data scheduling on PDSCH (Physical Downlink Shared Channel). The implementation of this option can be either Resource Block (RB)-level when the whole RB containing LTE CRS is taken out of NR scheduling, or RE-level where NR PDSCH scheduling avoids particular REs only. The end result of this method is that the scheduler will reduce the NR PDSCH transport block size as the number of REs available for scheduling become less in a slot.


Personally, I am not a big fan of DSS mainly because I think it is only useful in a very few scenarios. Also, it helps operators show a 5G logo but doesn't provide a 5G experience by itself. Nevertheless, it can come in handy for the coverage layer of 5G.


In one of the LinkedIn discussions (that I try and avoid mostly) somebody shared this above picture of Keysight Nemo DSS lab test results. As you can see there is quite a bit of overhead with DSS.

Thursday, 14 May 2020

A Look into 5G Virtual/Open RAN - Part 4: Intra-gNB DU Handover


In the previous posts of this series I described O-RAN interfaces and protocols, connection establishment and connection release procedures. Now it is time to look at handovers.

As mentioned in one of the earlier posts the gNB-CU CP will be in charge of controlling hundreds of gNB-DUs in a similar way like the 3G RNC was in charge of controlling hundreds of UMTS NodeBs. As a result the most common 5G SA intra-system handovers will be intra-gNB handovers. These handovers can further be classified into intra-gNB-DU handovers (inter- as well as intra-frequency) and inter-gNB-DU handovers.

Due to the virtualization of RAN network functions we will also find another form of switching transmission path, which is a change of the gNB-CU UP during the call without mobility of the UE. This scenario I will discuss later in a separate blog post.

Today I want to focus on the intra-gNB DU handover. Here the UE moves from one cell to another one within the same distributed unit as shown in the figure below.



A prerequisite is the successful establishment of a NR RRC connection and a F1AP UE Context between the gNB-DU and the gNB-CU CP.

The F1AP transports all RRC messages between these two entities. Indeed, it transports the PDCP blocks and the gNB-DU is not aware that these PDCP blocks contain RRC messages. However, for better illustration I have not shown the PDPC part in the ladder diagram.

What we see in step 1 is a NR RRC Reconfiguration message that contains RRC measurement configurations to be enabled on the UE side. A typical trigger event for intra-frequency handovers is the A3 event that is already known from LTE RRC.

Once the UE detects a better neighbor cell meeting the A3 criteria it sends a RRC Measurement Report to the gNB-CU CP (step 2).

In step 3 the gNB-CU CP orders the gNB-DU to perform a F1AP UE Context Modification. The purpose is to allocate radio resources for the UE in the target cell and to prepare the cell change.

The gNB-DU replies with F1AP UE Context Modification Response. This messages contains the new C-RNTI and a large block of lower layer configuration parameters (e.g. for RLC and MAC layer) that need to be sent to the UE and thus, need to be transported to the gNB-CU CP before, because it is the only RAN function capable to communicate with the UE using the RRC protocol.

Hence, in step 5 we see another downlink RRC message transfer. This time it is used to transport the handover command towards the UE. The handover command is a NR RRC Reconfiguration message and it contains the new C-RNTI (new UE identity within the cell) as well as the physical cell ID of the target cell and the full set of lower layer configuration parameters previously provided by the gNB-DU.

When the gNB-CU CP receives the RRC Reconfiguration Complete message sent by the UE in step 6 the handover is successfully completed and the UE is now served by the cell with NR PCI 2.

As mentioned before there is neither XnAP (communication between two neighbor gNBs) nor NGAP (communication between gNB and AMF) involved in this handover procedure.

Monday, 11 May 2020

5G Remote Surgery and Telehealth Solutions


One of the most controversial 5G use cases is the remote surgery. In this post I want to quickly look at the history and what is possible. Before I go to that, here is a short summary video that I am embedding upfront.



As far as I can recall, Ericsson was the first vendor that started talking about remote surgery. This is a tweet from back in 2017.


Huawei didn't want to be far behind so they did one at MWC Shanghai in 2018. Their tweet with video is embedded below.


In January 2019, South China Morning Post (SCMP) showed a video of a remote surgery on an animal. While the video and the article didn't provide many details, I am assuming this was done by Huawei as detailed here. The video of the surgery below.



This was followed by Mobile World Congress 2019 demo where a doctor used 5G to direct surgery live from a stage at MWC to Hospital Clinic Barcelona over 3 miles away. The team of doctors was removing a cancerous tumor from a patient's colon. This video from that is embedded below.



Vodafone New Zealand had a silly remote surgery of a dog video but looks like they have removed it.  Nothing can beat this Telecom Italia ad embedded below.



There are some realistic use cases. One of them being that with 5G the number of cables / wires in a hospital can be reduced saving on the disinfection.
NTT Docomo showcased 5G Mobile SCOT (Smart Cyber Operating Theater) which is an Innovative solution to enable advanced medical treatment in diverse environments. You can read more details here.

There are lots of other things going on. Here is a short list:
  • April 2020: Because of Coronavirus COVID-19, NT Times has an article on Telemedicine Arrives in the U.K.: ‘10 Years of Change in One Week’ - even though this does not involve 5G, it just shows that we are moving in that direction.
  • February 2020: 5G-aided remote CT scans used to diagnose COVID-19 patients in China (link)
  • February 2020: Verizon teamed with Emory Healthcare to test new 5G use cases for the medical industry at the latter’s Innovation Hub in Atlanta, in a bid to discover how the technology can be used to improve patient care. The collaboration will explore applications including connected ambulances; remote physical therapy; medical imaging; and use of AR and VR for training. (link)
  • February 2020: Vodafone 5G Healthcare – Conference & Experience Day (link)
  • November 2019: TIM enables first live remote-surgery consultation using 5G immersive reality (link)
  • October 2019: Along with a hospital in Malaga, Telefónica has presented what it claims is the first expert assistance system for medical interventions that runs on 5G. (link and video)
  • September 2019: Mobile Future Forward 2019 - World's First Remote VR Surgery Demo conducted on Sept 4th, 2019 in Seattle by Chetan Sharma, James Youngquist, Evie Powell, Nissim Hadar, David Colmenares, and Gabe Jones. (link)

Finally, a nice video on Benefits of 5G for Healthcare Technology by T-Mobile



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Thursday, 7 May 2020

How the A6 Measurement Event triggers Secondary Cell Change in LTE Carrier Aggregation Calls


Last week I read in Martin Sauter's blog about the LTE RRC A6 measurement event.

Although I am quite interested in RRC measurements I have never seen the A6 event in action. Rather the eNB vendors have implemented carrier aggregation in a way that the UE provides its capabilities and according to the this the maximum possible numbers of component carriers is added to the connection. There is no RRC measurement report before adding secondary LTE cells to the connection. So what is the A6 event good for and is it used at all?

Surprisingly I needed only 2 attempts to find an example of using the A6 event in a live network configuration. It is used when more component carriers are available than the UE can simultaneously handle. E.g. if there are 4 or more cells with different carrier frequencies available in the same antenna sector the A6 event ensures after the initial CA configuration that the cells with the best radio conditions are selected as secondary cells.

Let's have a look at this scenario in detail. Figure 1 shows the report configuration for the A6 event. Keep the reportConfigId = 3 in mind.


Figure 1: Report Configuration for Event A6

The next step is the configuration of the Measurement ID as shown in figure 2. Here the reportConfigId is combined with a measObjectId that represents the carrier frequency of the potential SCell.

Figure 2: Measurement ID for Event A6
Now, if the event A6 is triggered in the UE a RRC Measurement Report with this measId = 3 is sent to the eNB as shown in Figure 3.

Figure 3: RRC Measurement Report for Event A6
There we see the RSRP and RSRQ of the primary cell (PCell) and of the currently serving secondary cells (SCells). By the way the servFreqId stands for the sCellIndex value that was linked to the physical cell ID (PCI) when this SCell was added in a previous RRC Connection Reconfiguration procedure. 

And as one can see the neighbor cell with PCI = 470 has significantly better RSRP and RSRQ to offer than both currently used SCell. 

Consequently the eNB decides to replace the SCell with sCellIndex value 1 with the better cell (PCI 470). This is again done with a RRC Connection Reconfiguration procedure as shown in figure 4. And this is the way how the A6 event is used.


Figure 4: Change of SCell
  

Wednesday, 6 May 2020

Virve 2.0 - Finland's 4G/5G Public Safety Network

State Security Networks Group Finland (Erillisverkot) safeguards the Finnish society by offering authorities and critical operators engaged in critical infrastructure and services secure and reliable ICT services. Much like in the civilian world, communication between authorities includes transferring images and video material to an increasing degree, which results in ever-growing data transfer volumes and, subsequently, new kinds of demands for all communication networks. 


Virve is a means of ensuring communication and cooperation between authorities and other partners across organisational borders into the future. It also entails the introduction of a higher service standard, as the transfer to broadband, estimated to take place in 2022, will make it possible to transfer video material, images and data. This will mean that it will be possible to send video material in a reliable and secure way in the case of accidents, for example. The radio network Virve, based on Tetra technology, will reach the end of its lifecycle by the end of the 2020s. The current Virve network will be used simultaneously with the new Virve 2.0 network until, at least, 2025.


Erillisverkot will acquire the broadband Virve 2.0 radio access network as a service from Elisa and the core systems from Ericsson. Separate networks will ensure the continuity of critical communications and operational capability of public safety in all situations in the future.

I would assume this would be MOCN, similar to the UK deployment of ESN networks as shown here.

Virve 2.0 subcribers will use Elisa’s public radio network, which the operator is expanding to become Finland’s largest data and voice network.

About 80 million messages pass through the Virve system every week. Elisa is committed to increasing the coverage, capacity and verification of its mobile network to meet the requirements of Virve 2.0.

The new online services will provide support for critical communication between public authorities and other parties.

The addition of image, video, and other wireless broadband services alongside existing Virve services will enable a better and more up-to-date view of the day-to-day operations of authorities and other actors.

The IoT enables automatic monitoring of rescue personnel and mobile use of surveillance cameras and drones.

The Virve 2.0 radio network service will be in use from 2021 and will include the 4G and 5G technologies and the internet of things. The contract is for ten years.

Finally, a recent advert of Elisa explaining 5G to outside world



Further Study:
  • Erillisverkot: Obstacles for MCX Broadband and how to overcome them [PDF]
  • Erillisverkot: Virve Broadband Plans for the Future - Critical Communications Europe 2019 [PDF]
  • 5G-XCast Whitepaper: Rapidly Deployable Network System for Critical Communications in Remote Locations [PDF]
  • Erillisverkot: White paper - Virve 2.0 RFI Summary of responses [PDF]
  • Erillisverkot: Factsheet - What is Virve 2.0? [PDF]

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Friday, 1 May 2020

The Futuristic Concept of 'Smart & Intelligent' Batteries


I did a presentation back in 2013 on the concept of smart batteries. Even though there has been a lot of progress in wireless charging since back then, it hasn't reached even close to the vision that I have. As a result, I converted it into a video to start a discussion on if and when this would be possible. The slides and video are embedded below and I welcome any discussion in comments below.






Tuesday, 28 April 2020

Comparing S1AP and NGAP UE Context Release


As an addition to my blog post about the 5G RAN Release procedure I would like to have an in-depth view at the details of NGAP UE Context Release Complete message.

Indeed, the S1AP (known from E-UTRAN) and the NGAP are very similar protocols and when reading the 3GPP specs it is obvious that many message names are identical and the procedures fulfill the same purpose when looking at call scenarios.

However, the difference is visible in the details as one can see when looking at the figure below.

While the S1AP UE Context Release Complete message does not contain any additional information we find in the NGAP UE Context Release Complete the identity of the last serving 5G cell, represented by the NR-CGI, the last visited Tracking Area Identity (TAI) and a list with the IDs of the PDU sessions (E-RABs) that have been terminated when the UE context was released.

This additional information in very valuable for network troubleshooting, since in LTE (S1AP) only the ID (ECGI) of the initial serving cell or a new serving cell ID at inter-node handover was signaled. And if you wanted to know how many E-RABs have been terminated with a S1AP UE Context Release procedure it was necessary to look back into the full sequence of call-related S1AP messages starting with the messages for Initial Context Setup.

All in all, with 5G NGAP trace analysis and the life of RAN engineers becomes easier. Thank you, 3GPP! 

Comparision of S1AP and NGAP UE Context Release Complete Messages

Friday, 24 April 2020

A Look into 5G Virtual/Open RAN - Part 3: Connection Release and Suspend


The 3rd post of this series introduces the details of connection release in the 5G RAN.

Indeed, we find most of the release causes known from E-UTRAN in the 5G specs and it is clear that all protocols that have been involved in the connection setup need to be perform a release procedure at the end of the connection.

However, again the split into different virtual functions brings the demand for some addition messages.

This is illustrated in figure 1 for the a release due to "user inactivity", which means: the gNB-CU UP detected that for a define time (typical settings for the user inactivity timer are expected to be between 10 and 20 seconds) no downlink payload packets have been arrived from the UPF to be transmitted.

So the gNB-CU UP sends an E1AP Bearer Context Inactivity Notification message to the gNB-CU CP that triggers the release procedures on NGAP, F1AP, RRC and E1AP. The RRC Releases message is transported over the F1 interface to the gNB-DU where is forwarded across the radio interface to the UE.


Figure 1: Connection Release due to "user inacativity"
An alternative to the connection release is the RRC Suspend procedure shown in figure 2. Here the UE is ordered to switch to the RRC Inactive state, which allows a very quick resume of the RRC connection when necessary.

Figure 2: RRC Connection Suspend

In case of suspending the RRC connection the RRC Release message contains a set of suspend configuration parameters. The probably most important one is the I-RNTI, the (RRC) Inactive Radio Network Temporary Identity.

If the RRC connection is suspended, F1AP and E1AP Contexts are released, but the NGAP UE Context remains active. Just NGAP RRC Inactivity Transition Report is sent to the AMF.

Monday, 20 April 2020

A Look at the same RRC Message in LTE and 5G Stand-alone Call Scenarios


Some weeks ago the differences in 4G LTE RRC (3GPP 36.331) and 5G NR RRC (3GPP 38.331) and how both protocols interact in EN-DC call scenarios have been discussed in another blog post.

Now I would like to share a visual comparison of the RRC (Connection) Setup Complete message as it is seen in LTE (including EN-DC) and 5G stand-alone (SA) radio connections.

From the figure below one can see that although this message fulfills the same purpose in both radio access technologies its particular contents may look quite differently.

Different variants of RRC (Connection) Setup Complete message in LTE and 5G stand-alone call scenarios

Sunday, 19 April 2020

SCF Releases 5G Functional API to Enable Open Small Cells Ecosystem


The Small Cell Forum (SCF) announced the publication of documents focused on stimulating a competitive ecosystem for vendors of 5G-era small cell hardware, software and equipment. The expanded set of specifications contained in these documents are:
According to the press release:

Expanding upon the 5G Physical Layer API specification, published in July 2019, the new specifications enable small cells to be constructed piece-by-piece using components from different vendors, in order to address the diverse mixture of 5G use cases relatively easily, a common goal to all of the specifications made by Small Cell Forum.

The new release also includes two completely new specifications, SCF223: 5G NR FAPI P19 FrontEnd Interface Specification and SCF224: Network Monitor Mode API for Small Cells.


According to Dr. Prabhakar Chitrapu, Chair of SCF, “FAPI helps Equipment Vendors to mix PHY & MAC Software from different suppliers via this open FAPI interface. So, FAPI is an 'internal' interface.”

“5G-nFAPI (network FAPI) is a 'network' interface and is between a Distributed Unit and Centralised Unit  of a Split RAN/Small Cell network solution. An open specification of this interface (nFAPI) will help network architects by allowing them to mix distributed and central units from different vendors.”

SCF nFAPI is enabling Open RAN ecosystem in its own way by allowing any small cell CU/DU (S-CU / S-DU) to connect to any small cell radio unit (S-RU)

Here is a video playlist from SCF that explains the new API's



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Tuesday, 14 April 2020

Mobility Analysis: Austrians Stay at Home

The Austrian company Invenium Data Insights GmbH has partnered with the mobile network operator A1 to analyze and visualize subscriber mobility pattern on a public dashboard to illustrate the impact of the severe restrictions on people’s mobility (and its expected reversal) due to the COVID-19 pandemic.

Screenshot of the public dashboard (click picture to enlarge)

In a side note (in the screenshot highlighted in yellow) and in their blog the partners guarantee that the underlying data is fully anonymous and not derived from customer data. This was certified by TüV, an independent Technical Inspection Association.

Although I have no insight into this particular project I assume that the underlying raw data is provided by eNBs using the 3GPP-defined maximum detail level cell trace according to 3GPP 32.423.

This means that the trace collection entity gets the full ASN.1 contents of all RRC, S1AP and X2AP messages, but NAS messages - if provided at all - are encrypted. Also the eNB has not insight into any user plane applications since it has no means to decode the IP payload. This guarantees that neither IMSI, IMEI, web addresses nor phone numbers are found in the raw data.

The key for a meaningful mobility analysis using this data might be the fact that the S-TMSI value in E-UTRAN rarely changes and due to user inactivity settings each subscriber generates multiple RRC connections per hour. Within these RRC connections we find RRC Measurement Reports and typically also some vendor-specific events providing other important radio parameters from the radio interface lower layers including uplink radio quality measurements like PUSCH SINR.

By looking at multiple RRC connections of the same S-TMSI and the reported air interface measurements it is possible to determine if the subscriber remains at the same place or moves around. It it also possible to determine if a subscriber is located indoor or outdoor.

The trace collection entity writes the analysis results into a comprehensive data set that can be used to mask and scramble even S-TMSI values for additional data privacy. The raw data is deleted.

At the end this methodology allows a highly reliable mobility analysis while simultaneously protecting the data privacy of subscribers. The key difference in comparison to statistics based on crowd-sourced data as published e.g. by umlaut is the fact that the 3GPP cell trace provides data for all RRC connections in the network while crowd-sourced data collection requires the installation of certain apps (in case of umlaut only Android apps are supported) and the subscriber's confirmation to collect the data.

However, it must be mentioned that the 3GPP cell trace cannot be used as a data source for the widely discussed Corona contact tracking apps that allow to identify subscribers that have been in close proximity with someone who has been tested positive for COVID-19. For this purpose cell trace data lacks the necessary accuracy to determine the subscriber's and its neighbor's positions.