Monday, 27 July 2020

Key Technology Aspects of 5G Security by Rohde & Schwarz

The 3G4G page contains a lot of useful papers and links to security here but we have also looked at evolution of security from 4G to 5G here. Rohde & Schwarz has a short 8-minute video in which wireless technology manager, Reiner Stuhlfauth, explains the key technology aspects ensuring 5G security. The video is embedded below.

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Sunday, 19 July 2020

Mobile Initiated Connection Only (MICO) mode in 5G System

Mobile Initiated Connection Only (MICO) mode is designed for IoT devices that send small amounts of data and do not need to be paged. An example of this could be a smart bin that sends a message to the waste collection company saying it is 50% full, etc. This way the bin emptying lorry can plan to empty it in the next collection round. Here there is no reason to page the bin as there is no mobile terminated data that would be required.

MICO mode has to be negotiated between the device and AMF in 5GC. A device in MICO mode cannot be paged as it would not listen to paging to conserve battery power. This extreme power saving mode can ensure that the battery can last for very long time, ideally years thereby making this vision of billions of connected IoT devices a reality.

In an earlier post on RRC Inactive state, we looked at NAS states, along with RRC states. When the UE is in MICO mode, the AMF in 5GC will consider the UE to be unreachable when it is in CM-IDLE state. In addition, a periodic registration timer is also allocated to the MICO mode UEs. The UE has to confirm the MICO mode again during registration update.

The video and presentation are embedded below:

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Friday, 17 July 2020

A Look into 5G Virtual/Open RAN - Part 7: Change of gNB-CU-UP without Handover

This will be the last part of my series about Virtual/Open RAN signaling procedures. In this final post (although not the last one on this blog) I would like to present a very unique procedure that emerges from the facts of virtualization and automation of the RAN. And again I would like to present the big picture overview of the scenario that is called "Change of gNB-CU UP" (without handover). The full message flow (ladder diagram) can be found in 3GPP 38.401, chapter 8.9.5.

In the same chapter one can read that the trigger point for starting a change of the gNB-CU UP is quite vague. 3GPP writes: "e.g. a measurement report". However, which particular measurement event should trigger such a procedure? Even when looking into the Rel. 16 versions of 3GPP 38.331 (NR RRC) it becomes evident that all measurement events that are not dealing with NR sidelink or V2X connectivity are triggered by changing reference signal strength or rising interference. 

However, in case of a gNB-CU UP change without handover the UE does not move to a different cell. This makes me think - correct me if I am wrong - the true trigger points for this procedures come form a different entity, e.g. from the AI-driven policies and algorithms of the RAN Intelligence Controller (RIC) that is a fundamental element of the Open RAN architecture.

So what is necessary from a signaling perspective to change the gNB-CU UP during an ongoing connection?

There are new transport network resources aka GTP/IP-Tunnels required to steer the user plane traffic to and through the RAN. A new F1-U tunnel is necessary as well a a new NG-U tunnel, because also the user plane traffic between RAN and the UPF in the 5G core network must be exchange using a new route.

When it is clear which new UP transport tunnels need to be established (and which old ones need to be deleted) it is really simple to understand the overall scenario.

A F1AP UE Context Modification procedure is performed to switch the F1-U tunnel. NGAP Path Switch procedure is performed to switch the NG-U tunnel. And an E1AP Bearer Context Modification procedure is the prerequisite, because it delivers the new UL GTP-TEID for the F1-U tunnel as well as the new DL GTP-TEID for the NG-U tunnel.

Unfortunately the authors of 3GPP 38.401 are not very precise when mentioning protocol procedures defined in other specs. Thus, they speak about "bearer modification" when looking at F1AP and "Path Update" for NGAP.

It is not a big deal, but something you just need to know if you want to analyze real-world message flows of this scenario.

Sunday, 12 July 2020

Anritsu Webinar on 'Evolution of 5G from 3GPP Rel-15 to Rel-17 and Testing Challenges'

At the TSG#88e Plenary meetings that ended on 03 July 2020, Release 16 was completed with both the Stage 3 freeze and the ASN.1 and OpenAPI specification freeze being approved. The 3GPP Release-16 page has more details on timelines but they may shift. See at the bottom of this post.

Anritsu have uploaded a short presentation on their channel that I am embedding below. I have skipped the beginning part but of you feel like you want to listen, jump to the beginning.

Meanwhile in the recently concluded TSG#88e Plenary meetings, there is a discussion on some of the timelines for Release-17 and Rel-18 moving. This graph below is from SP-200606.

In another piece of 3GPP news, RAN Working Group 6 (WG6 or RAN6) – responsible for the GERAN and UTRAN radio and protocol work - was formally closed.  No new features but specs will be maintained as necessary, of course.

Finally, here is a short video interview by 3GPP in which Balazs Bertenyi looks back at the recent TSG RAN Plenary e-meeting. He talks about the challenges, about IMT-2020, Rel-16 being just on time & the prospects for Rel-17.

Release 16 - RAN progress from 3GPPlive on Vimeo.

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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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