Friday, 23 September 2016

5G New Radio (NR), Architecture options and migration from LTE

You have probably read about the demanding requirements for 5G in many of my blog posts. To meet these demanding requirements a 'next-generation radio' or 'new radio' (NR) will be introduced in time for 5G. We dont know as of yet what air interface, modulation technology, number of antennas, etc. for this NR but this slide above from Qualcomm gives an idea of what technologies will be required for this 5G NR.
The slide above gives a list of design innovations that will be required across diverse services as envisioned by 5G proponents.

It should be mentioned that Rel-10/11/12 version of LTE is referred to as LTE-Advanced and Rel-13/14 is being referred to as LTE-A Pro. Rel-15 will probably have a new name but in various discussions its being referred to as eLTE.

When first phase of 5G arrives in Rel-15, eLTE would be used for access network and EPC will still be used for core network. 5G will use NR and eventually get a new core network, probably in time for phase 2. This is often referred to as next generation core network (NGCN).

The slides below from Deutsche Telekom show their vision of how operators should migrate from eLTE to 5G.

The slides below from AT&T show their vision of LTE to 5G migration.

Eiko Seidel posted the following in 3GPP 5G standards group (i recommend you join if you want to follow technical discussions)

Summary RAN1#86 on New Radio (5G) Gothenburg, Sweden

At this meeting RAN1 delegates presented and discussed numerous evaluation results mainly in the areas of waveforms and channel coding.

Nonetheless RAN1 was not yet prepared to take many technical decisions. Most agreements are still rather general. 

First NR terminology has been defined. For describing time structures mini-slots have been introduced: a mini-slot is the smallest possible scheduling unit and smaller than a slot or a subframe.

Discussions on waveforms favored filtered and windowed OFDM. Channel coding discussions were in favor of LDPC and Turbo codes. But no decisions have been made yet.

Not having taken many decisions at this meeting, RAN1 now is behind its schedule for New Radio.
Hopefully the lag can be made up at two additional NR specific ad hoc meetings that have been scheduled for January and June 2017.

(thanks to my colleague and friend Dr. Frank Kowalewski for writing this short summary!)

Yet another post from Eiko on 3GPP RAN 3 on related topic.

The RAN3 schedule is that in February 2017 recommendations can be made for a protocol architecture.  In the meeting arguments came up by some parties that the work plan is mainly addressing U-Plane architecture and that split of C- and U-plane is not considered sufficiently. The background is that the first step will be dual connectivity with LTE using LTE RRC as control plane and some companies would like to concentrate on this initially. It looks like that a prioritization of features might happen in November timeframe. Beside UP and CP split, also the functional split between the central RAN node and the distributed RAN node is taking place for the cloud RAN fronthaul interface. Besides this, also discussion on the fronthaul interface takes place and it will be interesting to see if RAN3 will take the initiative to standardize a CPRI like interface for 5G. Basically on each of the three interfaces controversial discussion is ongoing.

Yet another basic question is, what is actually considered as a “New 5G RAN”? Is this term limited to a 5G eNB connected to the NG core? Or can it also be also an eLTE eNB with Dual Connectivity to 5G? Must this eLTE eNB be connected to the 5G core or is it already a 5G RAN when connected to the EPC? 

Finally, a slide from Qualcomm on 5G NR standardization & launch.


David Starks said...

An excellent article. Thanks.
Late last evening at RAN1#87 we experienced an exciting way forward for channel coding. Flexible LDPC for UL and DL eMBB data and Polar for control channel UL and DL. Three companies presented Polar two with ASIC results and one SDR using DSP on today's HyperX chip from Coherent Logix. Still work to do in this part of the standard SI but it's moving along now.

David Starks said...

At RAN1#87 last evening's session on channel coding concluded with a way forward agreement on flexible LDPC for eMBB DL and UL data with Polar for control channel on DL and UL. Still due process to take place but nice progress.