COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED. Thomas Pfeiffer, Frank Schaich -...

COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.

Thomas Pfeiffer, Frank Schaich - Alcatel-Lucent Bell Labs StuttgartOFC/NFOEC wireless backhauling workshop - Los Angeles, 5.3.2012

OPTICAL ARCHITECTURES FORMOBILE BACK- AND FRONTHAULING

2


Backhauling or fronthauling ? EPC : Evolved Packet CoreBBU : Baseband UnitRAN : Radio Access Network

IP backhaul or CPRI fronthaul ?=

conventional RAN or cloud RAN ?

… most likely both of them

core network

metro cellmetro cell(200 m diam.)(200 m diam.)

EPC

centralizedBBU

IP backhaul

CPRIfronthaul

macro cellmacro cell(1 km diam.)(1 km diam.)

IP backhaul

conventional RAN

cloud RAN

3


Fiber transmission systems

• protocol : IP, CPRI, others (digital; RoF not considered here) direct or over PON, Ethernet, …

• multiplexing : TDM, WDM, TWDM, …

• topology : ptp, ptmp, ring

• architecture: dedicated ? overlay ? shared with FTTx ?

Metrics

• technical metrics :

bandwidth (scaleability, user statistics), latency, jitter

environmental factors : temperature, humidity, mechanical

location factors : availability of local powering, footprint, accesseability

• economic metrics :

infrastructure : ownership, availability of dark fibers, digging cost, leasing cost, opportunity for sharing

location factors : power supply and power consumption, rights of way

Choice of transmission technology : optical only

4


Backhauling and fronthauling bandwidth in LTE

IP backhauling = variable bitrate- antennas may be grouped (e.g. beamforming) : each group counts as one single element

- user traffic statistics apply : - shown above are achievable peak rates on air i/f - avged. values may be less by an order of mag

IP backhauling = variable bitrate- antennas may be grouped (e.g. beamforming) : each group counts as one single element

- user traffic statistics apply : - shown above are achievable peak rates on air i/f - avged. values may be less by an order of mag

CPRI fronthauling = constant bitrate

- each antenna counts separately (individual streams)

- 8B/10B can be removed for transport over Ethernet

- compression can be applied to reduce to 1:3

CPRI fronthauling = constant bitrate

- each antenna counts separately (individual streams)

- 8B/10B can be removed for transport over Ethernet

- compression can be applied to reduce to 1:3

IP peak bandwidth per site

100

1000

10000

100000

1 10

100

40

20

10

totalMbps

# antennas / sector

MHz3 sectors

typ. for macro cell

CPRI bandwidth per site

0,1

1

10

100

1000

1 10

100

40

20

10

totalGbps

# antennas / sector

MHz3 sectors

* 8/15 in case ofWCDMA

typ. for macro cell

5


Backhaul and fronthaul network dimensions and architecture shall account for traffic statistics

• traffic statistics per cell statistical multiplex gain on IP backhaul

• variations of total cell traffic over the day load sharing (pooling gain) in cloud RAN

Impact from traffic statistics

taken from Alcatel-Lucent Technology lightRadioTM White Paper „Economic analysis“ (2011)

6


Latency in LTE : limited by synchronous UL HARQ

n Orig. TX

n+4

n+8

NACK

1 st RTX

UE eNB

t [ms]

3 msec fixed delay defined by LTE standard

eNB processing1. PHY: UL frame decoding2. MAC: ACK/NACK creation3. PHY: DL frame creation

t [ms]

n Orig. TX

n+4

n+8

NACK

1 st RTX

UE eNB

reduced time for eNB processing

t [ms] t [ms]

RRH

round trip time (10 µsec / km)+ transport systemprocessing time

t [ms]

The allowed RRH eNB transmission time is limited to <<1 msecIt comes at the expense of a reduced processing time in the eNB

The allowed RRH eNB transmission time is limited to <<1 msecIt comes at the expense of a reduced processing time in the eNB

7


Serving area around traditional CO

• 32 macro cells, backhauled by single dedicated 10G-PON

- peak rate = 10Gbps per site; sufficient even for extreme loads

- average rate = 320 Mbps per site can be increased by using multiple 10G-PONs, WDM-

stacked

- link length = 20 km reaches any site within the area over realistic cable routes

Possible migration towards serving from consolidated Super-CO

• via WDM stacking : hybrid WDM/TDM long reach 10G-PONs

(cf. PIEMAN, MUSE, SARDANA for example architectures + upcoming NGPON2 standardisation for specs (tbd) )

IP backhaul by 10G-PON : urban area, macro cells

max. 20 km

powersplitte

r

Central Office

powersplitter

eNBs

1

4Route

r

12

8

OLT ONT

CO

serving area:diam. 6 km

macro cell:diam. 1 km

8


Scenario: serving area around CO with

- 32 macro cells: 10G peak / 320M avge. 10G-PON, 1:32 split(3 sectors * 8 antennas * 100 MHz) (XGPON1 or XGPON2)

- 16 metros per macro : 1.7G peak / 26M avge. 8 x GPON, 1:64 split each(1 sector * 4 antennas * 100 MHz) (stacking via low cost WDM)

low cost WDM-PON by cyclic wavelength allocation within 40 nm band cf. Pöhlmann, Pfeiffer: ECOC 2011, paper We.9.C.1

IP backhaul (ct‘d) : urban area, macro + metro cells

CO

serving area:diam. 6 km

macro cell:diam. 1 km

metrocells

max. 20 km

hybrid splitter:10G - power splitter

GPON - cyclic AWG

Central Office eNBs

12

8 metro (8 x 64)

macro (32 x)10G-PON

GPON

macro area

12

16

diplexer

powersplitter

10G +j GPON

powersplitter

1

4

Route

r

WDM1r(diplexer)

GP

ON

#1

… #

81

0G

PO

N

cyclicAWG

OLTs

9


• BBU clustering : move BBU hardware from BTS into common central space

simplified hardware at antenna sites (footprint, electrical power) and in BBU (indoor specs)

„zero latency“ links between BBUs allow for implementing CoMP and ICIC algorithms

• BBU pooling : share hardware elements between multiple colocated BBUs

additional benefit : ease of load-sharing between clusters

• Either variant requires CPRI links to remote antenna sites

transmission bandwidths easily reach levels that render TDM-PON unattractive

small split factors (1:2 or 1:4)

constant bitrate, i.e. no statistical multiplex gain

strict latency limits (<<1 msec) require zero framing/buffering etc. delays

most viable solutions employ ptp-links via

fiber, if available …

wavelength : ptp-WDM overlay on TDM-PON or „pure“ WDM-PON

Centralized processing : variants and benefits


CPRI fronthaul via WDM overlay on LR-PON(ACCORDANCE project)

SMCO

MCO 2

L2RN

R-,B-ONUs

32...64 subs

10-20km

R-,B-ONUs

10-20km

L3RN

MCO 4 MCO 3

MCO 1

OLT

L1RN

L1RN

fixed/mobile coupler

eNB

R-,B-ONUs

L1RN

L1RN

metro mux street level coupler Macro Cell TRX (DWDM)Metro Cell TRX (CWDM)

SMCO

MCO 2

L2RN

R-,B-ONUs

32...64 subs

10-20km10-20km

R-,B-ONUs

10-20km10-20km

L3RN

MCO 4 MCO 3

MCO 1

OLT

L1RN

L1RNL1RN

fixed/mobile coupler

eNB

R-,B-ONUs

L1RN

L1RN

metro muxmetro mux street level coupler Macro Cell TRX (DWDM)Metro Cell TRX (CWDM)

MCO … Metro Central OfficeRN … remote node

macro BS fronthauling

metro BS fronthauling

guar

d

guar

d

US

FH

-DW

DM

1260 1300 1350 1400 1450 1550 1600

DS

XG

PO

N1

GP

ON

GP

ON

XG

PO

N1

X/G

PO

N o

verla

y

/nm(to scale)

*

* ... being stripped beforefixed-services ONUs

waterpeak

EDFA

DWDM Tunsbles

FH

-DW

DM

1500

macro BS fronthauling

metro BS fronthauling

guar

d

guar

d

US

FH

-DW

DM

1260 1300 1350 1400 1450 1550 1600

DS

XG

PO

N1

GP

ON

GP

ON

XG

PO

N1

X/G

PO

N o

verla

y

/nm(to scale)

*

* ... being stripped beforefixed-services ONUs

waterpeak

EDFA

DWDM Tunsbles

FH

-DW

DM

1500

11


Enable BBU pooling, but not via CPRI : alternatives

incre

ased

op

tical lin

k

ban

dw

idth

- simp

ler re

mote

un

it- p

ossib

le p

oolin

g g

ain

s - sim

ple

r rem

ote

un

it- p

ossib

le p

oolin

g g

ain

s

EPC

EPC

classical eNBclassical eNB

PDCP

RLC

PDCP

RLCRFRFMA

CMAC PHYPHY

BIP

variable

EPC

EPC

central unit (cluster)central unit (cluster)

PDCP

RLC

PDCP

RLC

MAC

MAC

slim eNBslim eNB

RFRFMAC

MAC PHYPHY

≥ BIP

variable

EPC

EPC


PDCP

RLC

PDCP

RLC

MAC

MAC

PHY

PHY

extended RRHextended RRH

RFRFPHYPHY

e.g. 0.2 * BCPRI fixed

EPC

EPC


PDCP

RLC

PDCP

RLC

MAC

MAC

PHY

PHY

CPRI

CPRI

RRHRRH

RFRFCPRI

CPRI

BCPRI

fixed

IP backhaulingIP backhauling

split within L1split within L1

CPRI fronthaulingCPRI fronthauling

split within L2split within L2



Back-Up

14


Conventional Approach Example XG-PON1 upstream, 4 Wavelength Subbands SB1 – SB4

DFB laser wavelength can be tuned by heating or cooling by ≈ 0.08nm/K. Tuning range up to 3nm.

SB2SB1 SB3 SB4

1260nm 1265nm 1270nm 1275nm 1280nm

1260nm 1265nm 1270nm 1275nm 1280nm

Wavelength band is separated in four subbands for wavelength stacking

Randomly distributed DFB laser wavelengths in the 20nm band

15


TWDM 40/10G with ultra-low cost WDM upstream(ALU proposal, ECOC 2011)

CO feeder RN

OLT 1

OLT 3

OLT 2

OLT 4

CyclicWDM

wavelength sets

wavelength set

ONU 1

ONU 2

…

…

…

ONU n

I1

WS2

WS3

WS4

WS1

heating

50 GHz

wav

elen

gth

sets

Downstream : 4 x 10G TDM DWDM channels, 100GHz spacing, 1575-1580nm band

- OLT : -stabilised DFB transmitter- ONU : FP based tunable filter

Upstream : 4 x 2.5G TDMA wavelength sets, 50GHz grid, 1260-1280nm band

- OLT : filtered with cylical AWG- ONU : partially tunable DFB with integrated heater

WSDM (wavelength set division multiplexing)

Operational principle:- cyclic optical filter at Rx, 50 or 100 GHz grid- narrow range Tx tuneability instead of full band- accomplished by integrated heater stripe (no TEC)- otherwise conventional transmitter technology

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COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED. Thomas Pfeiffer, Frank Schaich -...

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