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Mobile Network Architecture for 5G Era - New C-RAN Architecture and Distributed 5G Core
October 06, 2015 | By Dr. Harrison J. Son and Dr. Michelle M. Do (tech@netmanias.com)
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Page 1 of 2


It's been only a year and a half since we excitedly introduced the Evolution of Mobile RAN Architecture in LTE/LTE-A Era (C-RAN) last April. And today we are discussing the same for 5G era already.


Key transitions from 3G to 4G included i) network architecture change from coverage-based to capacity-based, and ii) introduction of new 4G element, X2 interface. Specifically, cells became smaller for enhanced user throughput and network capacity, C-RAN was brought in for more efficient interference coordination between those smaller cells, and point-to-point backhaul was transformed into IP routing network to achieve minimal delay in X2 interfaces where interference coordination data between cells are exchanged.


While commercialized 5G is expected to arrive in 2020 globally, Korean operators are planning to launch 5G trial service in 2018.


Many predict 5G, compared to 4G, will give:

  • Ultra-high radio speed (20Gbps/UE) - New RAT, mmWave, massive MIMO, massive Aggregation
  • Ultra-low latency (E2E few msec) - Tectile Internet, autonomous driving, remote controlled machine
  • Massive connectivity (hundreds of millions of IoT devices)

Among the most talked about use cases of 5G selected by ITU-R and 3GPP are enhanced mobile broadband (mobile speeds up to 20Gbps), massive IoT (5G access by billions of IoT devices like sensor), and mission-critical IoT (Ultra-reliable and low latency communications).


How 5G, with higher technological requirements and distinguished use cases compared to those of 4G, will affect the current mobile network architecture? What changes will it bring?


1. Ultra-High Radio Speed ⇒  Enormous traffic at fronthaul ⇒ New C-RAN/Fronthaul
2. Ultra-High Radio Speed ⇒ Enormous traffic converging into the Core ⇒ Distributed 5G Core
3. Ultra-low latency ⇒ Distributed 5G Core



1. Ultra-High Radio Speed ⇒  Enormous traffic at fronthaul ⇒ New C-RAN/Fronthaul


Currently, all Korean operators use the same 4G RAN architecture, C-RAN (Centralized/Cloud RAN). In C-RAN, BBUs and RRHs are separated from each other, and BBUs are located at central offices (CO) or master cell sites while RRHs are located at cell sites. These separately located units are connected via CRPI interface (i.e. BBU - CPRI port - RRH), with one CPRI port connecting to each RRH. Each RRH has two antennas (2T2R) and has LTE channel bandwidth (BW) of 20MHz. So, the capacity of CPRI interface is 2.45Gbps.


Once massive MIMO is applied, CPRI capacity between BBU and each RRH has to be enhanced drastically. For example, if BW is 20MHz and an RRH has 16 antennas, then 19.66Gbps of CPRI capacity is required between BBU and the RRH. Moreover, if new RAT is used, BW is no longer 20MHz as in 4G LTE, but it will even further extend beyond 100MHz, 400MHz, and so on, eventually requiring tens or hundreds of Gbps of CPRI capacity per RRH.


Figure 1. CRPI fronthaul explosion due to untra-high radio speed


The C-RAN/Fronthaul architecture of today will no longer be able to handle such increasing capacity requirement in 5G era (Currently, the maximum transmission capacity per CPRI port is 10Gbps). To overcome this issue, a solution is proposed and is under review. This solution would re-define the functions of BBU and RRH, differently from the way they are defined now (i.e. pulling PHY, at least, down to RRH, thereby significantly reducing transmission capacity), and change the interface between BBU and RRH from Circuit fronthaul (CPRI) to Packet fronthaul (Ethernet).


In the approaching 5G era, BBU and RRH should be re-defined, and fronthaul should be re-built as packet fronthaul. To make these changes, many functional split options have been proposed, each offering trade-offs such as reduced fronthaul capacity, CoMP effect, RAN virtualization gain, etc. These new network solutions are currently being tested by many operators including the Korean big 3, NTT, AT&T, etc., by using equipment by RAN vendors like Nokia. (See Brief Survey - Operator’s View on 5G C-RAN/Fronthaul Redefinition)  



Figure 2. Functional split between BBU and RRH





Page 1 of 2
SATISH BABU 2015-10-10 00:10:15

This is perfectly captured. So true. Though most of them know some one have not put it for publishing. It is nice that Netmanias have done it.

Netmanias 2015-10-15 13:12:10

Thank you for your feedback. We appreciated it. 

falam 2015-10-12 04:29:47

Very well written and excellent article highlighting the issue of back-haul explosion. MEC will surely free the backhaul from Operator's Intranet, but the 5th generation of traffic, which would be Internet of Many-Many-Things, would also mean that other parties need to run their applications on virtualised servers. For example, even if the Operator manages to terminate the 'Smart Power' traffic at RAN, it still needs to be routed to a remote server located in the grid's premises, unless the utility company decides to go cloud.


This boils down to a very fundamental question - what would motivate others to match the fast moving wireless evolution? For a utility company, it would bring efficiency in energy distribution, but does such incentive exists for all? Or, will the telco define a common cloud architecture to facilitate every partner’s application? Much to think and much more to be standardised in this fast developing space…..

Junaid (Huawei) via LinkedIn 2015-10-13 14:49:19

Good summary

Kosala (Vodafone) via LinkedIn 2015-10-13 16:39:33

Have to agree, well written article

Bhavin (Idea Cellular) via LinkedIn 2015-10-14 11:38:02

Fronthaul and backhaul explosions requirements for 5g makes current 4g just a small begining of a larger global connected world....

onlyashu19 2015-10-15 02:28:35

Very well explained , it's a delight to read such a document . I always love reading Netmania's stuff as these guys are so good in presenting and explaining the things and most importantly are doing a Great and good job of spreading knowledge with timely latest updates and in an authentic way.

Really Appreciate it !!

Netmanias 2015-10-15 13:11:16

Thank you for your compliment. We are glad you liked it. 

Mohammad (Syriatel) via LinkedIn 2015-10-15 13:05:57

Very Interesting and updated blog on 5G networks architecture. Thank you for sharing.

Abdallah (SOFCON) via LinkedIn 2015-10-15 13:07:19

Migration from current networks infrastructures to 5G needs to be carefully studied and detail the migration plans in taking into consideration minimization of major hardware replacement and impacting network serviceability.

dhurgudevishal@gmail.com 2015-10-15 13:35:30

Nice Article!!! Very Much informative for engineers who want to excell in Telecommunciation field!!!

Netmanias 2015-10-15 15:56:33

Thank you for your comment. Visit us again for more. 

Obinna (AT&T) via LinkedIn 2015-10-15 15:51:25

Nice ! Successfull commercial implementation hurdle will hinge on fronthaul and backhaul advancement and if the C-RAN is going to be distributed or centralized. Distributed C-RAN with NFV will be the way forward.

Castello 2015-10-16 06:06:24

Excellent article! This explosion will certainly be more critical in wide area countries like Brazil!

Thanks for sharing! 

Akash (Ericsson) via LinkedIn 2015-10-16 11:52:04

Really Most of my basic concepts cleared by Netmanias .. Thanks for that . Really wonderful content.

Brian Lavallee 2016-02-27 09:43:24

Great document indeed. Can you please show the calculations as to how you arrived at the following two statements? (1) "Each RRH has two antennas (2T2R) and has LTE channel bandwidth (BW) of 20MHz. So, the capacity of CPRI interface is 2.45Gbps.", and (2) "For example, if BW is 20MHz and an RRH has 16 antennas, then 19.66Gbps of CPRI capacity is required between BBU and the RRH."?



Chinmaya Samal 2016-03-29 21:53:03

Very good topic. Really helps.

Edmund 2016-09-25 18:04:03

Great job Netmanias!! The site to visit for Next-Gen mobile technology. Keep up the great work.

Thank you for visiting Netmanias! Please leave your comment if you have a question or suggestion.

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