Cloud Ran Fronthaul.2015.02

www.mtigroup.com/mobile Public

Cloud RAN fronthaul

Options, benefits and challenges.

Aleksandra Checko, Industrial PhD student [email protected]

iJOIN Winter School "5G Cloud Technologies: Benefits and Challenges„ Bremen, 2015-02-23

www.fp7-harp.eu

www.mtigroup.com/mobile 2 Public

Outline of today’s presentation

Base station architecture evolution towards C-RAN – Traditional base station (past) – With RRH (present) – Cloud RAN (C-RAN) (present/future)

Fronthaul network – Bitrate, delay and sync requirements – Transport medium – Transport solutions

Fronthaul evolution

How? Why?


Traditional base station

Base station evolution

Telecom Italia Demo

Base station with RRH


Through base station with Remote Radio Head

Currently deployed

Power efficient

Easy cooling

For different standards

Interface: – Open Base Station Architecture Initiative (OBSAI) – Common Public Radio Interface (CPRI) (some parts are vendor-

specific) – Open Radio Equipment Interface (ETSI-ORI)

Fiber up to 20-40 km, usually p2p

Baseband Unit (BBU) a.k.a. Data Unit

Bas

eBan

d

Traditional Macro BS

Antenna

BScell

Tran

spor

t

Con

trol

Syn

ch

RF

PA

BS with RRH

Antenna

cell

RRHRF

BBU

Bas

eBan

d

Tran

spor

t

Con

trol

Syn

ch


To C-RAN architecture

Proposed by IBM in 2010 Cloud, Centralized processing, Cooperative radio, Clean

RF

RF

C-RAN with RRHs

Virtual BBU Pool

RRH

RRH

RRH

RF

Bas

eBan

d

Syn

ch

Con

trol

Tran

spor

t

Bas

eBan

d

Syn

ch

Con

trol

Tran

spor

t

Bas

eBan

d

Syn

ch

Con

trol

Tran

spor

t

Bas

eBan

d

Tran

spor

t

Con

trol

Syn

ch

Fiber – Digital BaseBand Coax cable – RF


Cloud RAN

Remote sites - RRH

FRO

NTH

AUL

Source: http://www.mti-mobile.com/

Source: http://krnet.or.kr/

Data center – BBU Pool


Fronthaul transport network

- “link” between RRH and BBU

P2P link for base station with RRH Fronthaul network based on

– WDM – Ethernet – OTN


Requirements on bitrate & timing

20 MHz LTE, 2x2 antennas (MIMO) – 150 Mbps for users, 2.5 Gbps on fronthaul link (CPRI)

Delay < 3 ms RRH-BBU-RRH (HARQ) ≈ 0.1- 0.2 ms on fronthaul (CMCC)

Jitter < 65 ns (MIMO, 36.104) Frequency error < 50 ppb (Macro BS, 36.104) BER < 10e-12 (CPRI, for specific application)


Which medium to choose?

Medium Bit rate Distance Remarks

Fiber 100Gbps + Tens km

Copper 10 Gbps 100 m

Microwave 1 Gbps (80GHz) 1.5 km LoS required

0123456789

10

2011 2012 2013 2014 2015 2016

Mill

ion

Mobile Backhaul Connections by Medium

Air

Fiber

Copper

Source: Infonetics Research, March 2012

Why to consider microwave, not fiber everywhere?


(Yes, people are working on compression)

Majority of algorithms – Remove redundancies in spectral domain, – Perform block scaling, – Use non-uniform quantizer – Up to 33% (3:1) compression ratio for 8% EVM – ALU, IDT

University of Texas at Austin – rescaling, – non-uniform quantization, – noise-shaping error feedback – Resampling – 5:1 ratio

One algorithm detects user activity – up to 7%! (14:1)

– Telefonica I+D


Transport solution

Technology is ready (capacity not necessarily)

CPRI / OBSAI

CPRI / OBSAI

WDM

CPRI / OBSAI

CPRI / OBSAI

Microvawe

Compression Compression

Eth/CPRI/ OBSAI

Eth/CPRI/ OBSAI

Ethernet

CPRI/ OBSAI

CPRI/ OBSAI

OTN

BBU Pool

RRH

CPRI / OBSAI Point to point

WDM-PON


Ethernet enables to maximize multiplexing gains

Among others to reduce cost of BBU pool

A. Checko, et al. ” Cloud RAN for Mobile Networks - a Technology Overview”, IEEE Communications Surveys & Tutorials

0,0

0,5

1,0

1,5

2,0

0 10 20 30 40 50 60 70 80 90 100

Mul

tiple

xing

gai

n

Office cells (%)

A. Checko, H. Holm, H. Christiansen, ” Optimizing small cell deployment by the use of C-RANs”, European Wireless 2014


Timing in fronthaul

Timing is really important Frequency of transmission Handover, coding

00 01 02

00 01

02

Device A Device B

Solution: timing distribution GPS PHY layer clock – SyncEth Packet-based timing

IEEE 1588v2 (PTP) Multiple

Requirements Phase error LTE-A with eICIC/CoMP:

± 1.5 - 5 μs, MIMO: 65 ns Frequency error LTE – A TDD/FDD:

±50 ppb


Shared Ethernet is even better for cost-saving

Access network - fronthaul

Aggregation network - backhaul

BBU Pool

CPRI / OBSAI

RemoteRadio Heads

CPRI / OBSAI

Aggregation network - fronthaul

Aggregation network - backhaulRemote

Radio Heads

IQ over Eth

CPRI2EthGateways

BBU Pool

GPS, 1588, ect

RRH

CPRI

GPS?, 1588?, new solution?

Variable delay

RRH++

BBU Pool++

Traditional fronthaul

Packet-based fronthaul

Sync delivered together with data (CPRI)

New Sync solution needed

BBU

Switching Multiplexing Widely deployed (reuse!) ! Fronthaul cost savings vs problems with delays ! Synchronous CPRI vs asynchronous Ethernet


HARP optimization

Looking when to use C-RAN Combining fiber and microwave Optimizing cell-BBU assignment


Deploying C-RANs

Trade off – Fiber length – Cells in the C-RAN – Multiplexing gain

TCO vs. capacity

A. Checko, H. Holm, H. Christiansen, ” Optimizing small cell deployment by the use of C-RANs”, European Wireless 2014


Optimization model

To maximize multiplexing gain and minimize fiber cost In multi C-RANs scenario

Aggregated Traffic (h)

Aggregated Traffic (h)

24 h

24 h


Partial C-RANs

Partial C-RAN – Some sites are excluded from the

C-RAN and are backhauled to the nearest C-RAN site by MWR

R. Al-obaidi; et. Al. ”C-RAN deployment scenarios”, DTU, 2014

Backhaul network

Base Stations

LTE

MWR

Fronthaul network Backhaul network

BBU Pool

CPRI

RemoteRadio Heads

MWR

FiberAggregated Traffic (h)

24 h

S1


Updates from industry

No more CPRI?! 4G towards 5G


It is time to rethink fronthaul towards 5G

New functional split between BBU and RRH

– To reduce fronthaul data rate – Decoupling user-processing and

cell-processing

No more CPRI? Need for interface supporting:

– Variable bit rate (traffic dependent to enjoy multiplexing gain)

• To increase scalability

– Packet-based • Synchronization is a challenge

– Multipoint to multipoint – Fully standardized

BBU Pool--

RRH

BBU Pool

Current C-RAN

Future C-RAN

10 Gbps

10 Gbps

2 Gbps

2 Gbps

2 Gbps

RRH++

BBU Pool--

2 Gbps

3 Gbps

3 Gbps

Vendor A

Vendor A

Vendor A

Vendor B

Vendor C


Timely topic

IEEE 1904.3 - encapsulation and mapping of IQ data over Ethernet IEEE 802.1 – CPRI fronthaul discussion with Time Sensitive Networking

task force CPRI CPRI2? 3GPP - proposal on a study item on variable rate multi-point to multi-

point packet-based fronthaul interface supporting load balancing


Wrap Up


Costs

– 2x2 MIMO, 20 MHz LTE,

15+1 CPRI 2.5 Gbps

– 3 sectors? 7.5 Gbps

– Tens of BS over long

distance? 100s Gbps

Costs vs savings

Fever BBUs? Fronthaul

cost?

Savings

– Equipment

– Energy

Re-define fronthaul


Base station architecture evolution

BaseBand RF

a) Traditional Macro BS

Antenna

RF

RF

c) C-RAN with RRHs

Virtual BBU Pool

BaseBandBaseBand

RRH

RRH

RRH

RF

Fiber – Digital BaseBand Coax cable – RF

BS

cell

BaseBand

RF

b) BS with RRH

Antenna

cell

RRH

BBU

RF

RF

d?) Possibly C-RAN with new function split between BBU and RRH

Virtual BBU Pool

BaseBandBaseBand--

RRH

RRH

RRH

RF

BB

BB

BB

FH network


Deployment scenarios

A. Checko, et al. „Cloud RAN for Mobile Networks - a Technology Overview”, IEEE Communications Surveys & Tutorials


Take away points

Fronthaul network capacity is a deal breaker for introducing C-RAN

Fronthaul solutions so far rely on legacy deployments

Industry is working on “redefining” fronthaul – towards switchable,

multipoint-to-multipoint connections, with a strong focus on Ethernet-

based solutions

Thank you for your attention

www.fp7-harp.eu

Cloud Ran Fronthaul.2015.02

Technology

Transcript of Cloud Ran Fronthaul.2015.02