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VOL. 14 NO. 5 ISSUE 14

13 Evolution of Microwave Radio forModern Communication Networks 31 Saving OPEX with SophisticatEnd-to-End Service Manageme06 Perceived Quality: The Key toCustomer Satisfaction

OCT 2012

Special Topic: 100G WDM

100G WDM Herald

the Ultra-Broadband Era

VIP Voice

OMTGrowing up with Our Client

Gregory Burlincho

chief technical ofcer of OM

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CONTENTS

Outremer Telecom (OMT) is the leading alterative

telco in Frances overseas departments and

regions. It has been cooperating with ZTE since

2006 to provide fixed line, mobile, and Internet

services to residential and business customers in

these territories. The two companies have built

2G and 3G networks in the Caribbean and Indian

Ocean islands. In a recent interview, OMTs CTO

Gregory Burlinchon talked about the telecom

environment in France, challenges for OMT, and

his expectation for future cooperation between

OMT and ZTE.

03

06 Perceived Quality: The Key to Customer SatisfactionBy Hans-Jrgen Schrewe

09 400G DWDM: Technologies and PerspectivesBy Zhensheng Jia

13 E v o l u t i o n o f M i c r o w a v e R a d i o f o r M o d e r n

Communication NetworksBy Ying Shen, Andrey Kochetkov and Thanh Nguyen

Tech Forum

03 OMT: Growing up with Our ClientsReporter: Liu Yang

VIP Voice

0906

1 ZTE TECHNOLOGIES OCT 2012

16

16 100G WDM Heralds the Ultra-Broadband EraBy Teng Weicai

19 OTN and 100G: The Inevitable Choice for

Future Optical NetworksBy Pan Kai and Zhang Runmei

21 Ultra 100G TechnologiesBy Ren Zhiliang

23 A Brief Analysis of SD-FECBy Zhu Xiaoyu


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CONTENTS

27

25 OMT: The Leading Alternative Operator in the French

Overseas Departments and RegionsBy Cao Tianhua

27 Tcell Paves the Way for a 3G NetworkBy Xu Xiaomei

Success Stories

29 LTE-Oriented Microwave Bandwidth ManagementBy Guo Jinghui

31 Saving OPEX with Sophisticated End-to-End Service

ManagementBy Xu Changchun

34 IPv6 Evolution SolutionsBy Hu Longbin and Ye Zhining

Solutions

37 ZTE Partners with KPN Group Belgium to Deploy

Packet Switched Core Network

News Brief

ZTE TECHNOLOGIES

Editorial Board

Editor-in-Chief: Jiang Hua

Executive Deputy Editor-in-Chief: Huang

Xinming

Editorial Director: Liu Yang

Executive Editor: Yue Lihua

Editors: Paul Sleswick, Jin Ping

Circulation Manager: Wang Pingping

Subscription / Customer Services

Subscription to ZTE TECHNOLOGIES is free

of charge

Tel: +86-551-5533356

Fax: +86-551-5850139

Email: [email protected]

Website: wwwen.zte.com.cn/endata/magazine

Editorial Ofce

Address: NO. 55, Hi-Tech Road South, Shenzhen,

P.R.China

Postcode: 518057

Tel: +86-755-26775211

Fax: +86-755-26775217

Email: [email protected]

ZTE Prole

ZTE is a leading global provider of

telecommunications equipment and network

solutions. It has the widest and most complete

product range in the worldcovering virtually

every sector of the wireline, wireless, service

and terminals markets. The company delivers

innovative, custom-made products and

services to over 500 operators in more than

140 countries, helping them achieve continued

revenue growth and shape the future of the

worlds communications.

A technical magazinethat keeps up with thelatest industry trends,communicates leadingtechnologies and solutions,and shares stories of ourcustomer success

OCT 2012 ZTE TECHNOLOGIES 2

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OMTGrowing up withOur ClientsReporter: Liu Yang

Gregory Burlinchon,

chief technical ofcer of OMT


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Outremer Telecom (OMT) is

the leading alterative telco in

Frances overseas departments

and regions. I t has a presence in

Martinique, Guadeloupe, French Guiana,

Runion, and Mayotte. OMT has been

cooperating with ZTE since 2006 to

provide fixed line, mobile, and Internet

services to residential and business

customers in these territories. Together,

the two companies have built 2G and

3G networks in the Caribbean and on

islands in the Indian Ocean. In a recent

interview, Gregory Burlinchon, chief

technical officer of OMT, talked about

the telecommunications envi ronment

in France, challenges for OMT, and

his expectation for future cooperationbetween OMT and ZTE.

Q: Can you introduce your company

and its business?

A: Outremer Telecom was founded in

1986 and has since established itself in

the French overseas departments and

regions. We are the leading alterative

telecom operator in these regions and

can offer xed line, mobile and Internet

services for residential and business

customers.

Capitalizing on the success of our

offers in the French West Indies and

French Guiana, OMT introduced its

mobile activities to Mayotte at the end

of 2006. Fixed telephone and Internet

services were provided in February

2007, and mobile services were offered

in Runion in April 2007.

OMT seeks to reinforce its position

as the leading alternative operator in the

overseas departments by significantly

expanding its Internet and mobile

subscr iber base . We a lso p lan to

br ing together our offers and provide

innovative services by evolving our

networks.

Q: Could you tell us something about

the telecommunications environment

in France and in the French regions?

What are the challenges for OMT?

A: In France, telecommunication markets

are owned by groups such as Orange

and Vodafone with an international

dimension. National operators such as

Orange and SFR are also present in the

French regions. SFR provides servicesin La Runion, and Orange provides

services both in the Caribbean and

Indian Ocean islands. Local operators

mainly offer ADSL.

The challenge for OMT lies in its

ability to continuously propose offers

that are innovative and competitively

priced.

Q: In the face of fierce competition,

how does OMT differentiate itself

in the overseas regions of France?

What is the key to OMTs sustainable

growth and development?

A : OMT has deve loped i t s own

telecommunication and distribution

network and has a marketing strategy for

innovative communication. This allows

us to assume an aggressive challenger

position in markets with strong growth.

The company rel ies on i ts unique

ONLY brand, which is now well-

known in all overseas regions. The brand

conveys a modern image of quality and

proximity.

OMT continues to invest in the latest-

generation technologies. OMTs team

has depth. This allows us to adapt our

offers to subscriber needs much more

rapidly than our competitors can do.

Q: What is important in a successful

business model? Does OMT have an

innovative business model?

A: High reactivity and an attacking

spirit allow OMT to efciently compete

against other operators. We have recently

revised our commercial offers for mobile

and fixed lines. This change has onlyoccurred within the last three months

and has allowed us to offer innovative

services such as unlimited voice, SMS,

and data to our subscribers.

Q: OMT has been cooperating with

ZTE since 2006. OMT and ZTE have

jointly built 2G and 3G networks in

the Caribbean and on islands in the

Indian Ocean. Why did OMT choose

ZTE as a partner?

A: OMT has chosen ZTE for many

reasons. First, ZTE provides carrier-

grade technologies that are comparable

to solutions proposed by Alcatel-Lucent,

Huawei, and NSN. Second, ZTE can

provide solut ions that are well-su ited

to the size of our territories. Finally,

ZTE fits in with our high-reactivity

ph ilo so ph y and can rapidly de liver

pr oject s. ZT E ca n or ga nize and re -


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organize a project according to OMTs

constraints.

Q : A f t e r a l m o s t s i x y e a r s o f

cooperation, whats your view of ZTE

and its project team?

A: ZTE has been able to ll a gap with

its main competitors in the areas of radio

access and core network. Progress is

still expected in value-added services. Interms of after-sales support, ZTE is quite

reactive when it comes to fixing major

incidents on our networks, but progress

is still expected in documentation

and validation. This will enhance the

reliability of provided solutions.

Q: ZTE he lped OMT swap i t s

networks in Martinique, Guadeloupe

a n d G u i a n a . W h a t w e r e t h e

difficulties of swapping networks in

these locations? What impressed

you about the project? How are the

networks running now?

A: The ma in d i f f i cu l t y i n t he se

swapovers was to avoid affect ing

our subscribers and to complete the

swapovers in an ext remely shor t

timeframe (less than six months). This

challenge was successful for both project

teams. After the swapovers, the enhanced

service quality met our expectations.

OMT needs to keep working with ZTE

for better performance.

Q : W h a t d o y o u t h i n k a b o u t

t he upcoming LTE and FTTX

deployments in France?

A: In the short term, there are no obvious

pr oject s on the ho rizon in Franc es

overseas regions and departments.

Unlike metropolitan France, FTTH

projects in the overseas departments are

really in their early stages, mainly for

nancing reasons.

Q: Whats your expectation for future

cooperation between OMT and ZTE?

A: OMT and ZTE teams have to work

closely for permanently enhancing

the quality of service delivered to our

subscribers. Quality of the network

also needs to be greatly improved. In

the coming years, programs for 3G

diversification are going to continue

and will require strong reactivity from

ZTE so that ZTE delivers services in the

shortest possible time. We are seeking

reinforced cooperation to develop

innovative services based on the latest

ZSmart and PCRF platforms that have

been acquired by OMT. We also expect

ZTEs product lines to play a prominent

role in allowing OMT to become a leader

in value-added services.


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KPN Is a Mobile Challenger

KPN is an integrated market

leader wi th fu l ly f ledged

services covering wireless,

wireline, broadband, VoIP and TV.

KPNs home market is the Netherlands.

We have our own networks in Germany

and Belgium.

E-Plus Challenger Strategy

Since 2005, the E-Plus Group has

positioned itself as a challenger in the

German mobile market, and we take a

regional approach to marketing. In some

cities, we have a market share of 40%, but

there are other cities where our market

share is small. So we gure out where the

opportunities are to regionalize ourselves

and how to address market challenges.

In certain areas, if there are at rate tariff

plans, the customer base start to increase

by itself. You need to overcome a certain

threshold. In markets where we havent

overcome the threshold, we use other

mechanisms.

As a result of innovative business

models, modern structures and strong

partnerships, the E-Plus Group was able

to significantly strengthen its market

position and show a more dynamic and

profitable development than the market.

We have outsourced network operations

to Alcatel-Lucent, and in the IT domain,

we have outsourced operations and even

some development work to Atos Origin.

W e c l o s e l y f o l l o w c u s t o m e r

demands. We look really closely at where

customers are using our network and

respond exactly in these areas. We need

to be sure that, especially in the regular

tariff framework, there is fair competition

with market leaders in areas such as

frequency and interconnection charges.

We are looking at new market

channels. We implemented models such

as MVNO, INMVNO that are designed

to bring partners to our network. We have

at least several big brands within our

network. The flat-rate brand BASE and

the mobile discounters Simyo and Blau

are market leader in their segments, while

the original E-Plus brand offers a range

of services to its existing customers. The

brand AY YILDIZ addresses the Turkish

Perceived Quality

The Key to Customer

SatisfactionBy Hans-Jrgen Schrewe

Dr. Hans-Jrgen Schrewe, head of SIT

technology, KPN Group

On 29 February 2012, ZTE convened a forum on smart pipes at the Mobile World

Conference. Dr. Hans-Jrgen Schrewe, head of SIT technology, KPN Group,

discussed how E-Plus Germany is improving quality for customers as it sees a

tremendous increase in data trafc. Dr. Schrewe spent 18 years with E-Plus (KPNs

daughter company in Germany) prior to moving to KPN. In his presentation, he

focused on the German market.


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little bit of an IT challenge, but we have

managed it. We dont charge subscribers

any connection or network fees, and

as we have seen elsewhere, this leads

to a tremendous increase in traffic. We

already know that flat rates in the voice

domain stimulate traffic. We have to be

able to cope with a tremendous increase

in data trafc.

Perceived Network Quality

In the past, the network operator had

nearly everything under its control. That

has completely changed. The customer

is surrounded by different clouds. Even

the perceived network quality can be

judged as a cloud. If I have MVNO, even

the network can be considered to be in

the cloud, and then individual brands

come into play. The Turkish community,

for example, has completely different

demands and feelings, and these come

into play in customer support. Theoperating system of a device itself and

the OTTs also need to be considered. To

really control the customer experience,

we have to go completely outside our own

areas of control, and we need automatic

mechanism to tell us what users expect.

We do customer interviews to

determine what customers expect and

their mobile phone usage habits. Voice

and SMS still dominate in the German

market, followed by data services, which

now are creating a dynamic market.

Network app

Together with another small company

we have developed a kind of network

app where we ask end-users about their

experience. We start by asking our own

employees about certain mechanisms

and how they experience the network. It

does not need to be complicated; we use

community in Germany. Our M2M brand

is used for machine-to-machine business,

and it is our rst foray into the OTT world.

We have a lot of brand partners,

and we only use their brands to resell

our products. There are famous football

teams, for example, that have their own

brand on our network. One of our prepaid

services is sold by one of the biggest

retailers in Germany. Our philosophy is

to intently follow customer needs and

offer very attractive prices. In Germany,

our focus is on mobile communications.

We try to introduce a wide range of

services with very simple tariffs. We are

cooperating very closely with ZTE and

other handset brands to provide attractive

devices to our customers.

Our most popular tariff plan is a at-

rate ten euro per month plan. You get a

at rate for voice calls within the BASE

community and a flat rate for SMS to

anyone. Users can also select from a

portfolio of other flat-rate services. We

even have a combination that includes

500 MB highspeed data usage per month

to any terminal. We bundle this plan

with a terminal to encourage people to

use our data services. In the past E-Plus

mainly concentrated on voice services,

and it is really paying off to have this

Internet at-rate tariff outside the bundle.

The at rates I mentioned earlier can be

changed on a monthly basis, so it is a


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communications is not only taking place

within the technical domain. We are

moving into 4G, and this entails change

within the organizations. We have to

become a customer-centered organization

and encourage our employees to change

their way of thinking. Those activities

that are not really about customers can

be done by third parties and outsourcing

partners. We have to take on board our

outsourcing partners, vendors, and OTTs

to form an ecosystem that produces

services that are smoothly perceived by

our customers.

ZTE Supporting the E-Plus Move

into 4G

How is ZTE supporting our move

to 4G? Within the KPN Group, E-Plus

Germany has a very strong relationship

with ZTE. We decided to bring ZTE

in the radio access domain. ZTE is

deploying HSPA+base stations, and it isa vendor with increasing market share. In

2011, we introduced ZTE to our packet

core network. We have PCRF up and

running, and we have a fair-use tariff

policy outside.

ZTEs behavior analysis system

would potentially allow us to get a better

grip on automatic processes. Together

with the university, we hope we can use

purely technical KPIs to influence real

user perceptions. We want technical KPIs

to contribute pragmatically to a better

network look and feel; we dont want them

to be purely technical indicators. ZTEs

evolved packet core will be introduced

over the course of the year, and ZTE

supports us with attractive terminals. The

company provides not only smart phones

but also tablets. ZTE is also helping us by

bringing in devices that we can associate

with our BASE brand.

simple pictures like smileys for feedback.

The customer can add measurements. We

are aware of every point in the network,

and what we are basically measuring is

signal strength. In this app, we have also

taken privacy into account, and the user

is not obliged to send their information

or measurements to the network operator.

However, to encourage users to share

this information with us, we have a

small ranking function built into the

app, so we say OK, you have sent 100

measurements, you are ranked No. 1 out

of all the users. At the moment, we

are trialing it with our own employees,

but we intend to roll it out to interested

customers as well. We may even roll

it out to certain brands running on our

networks.

Continuous dialog

We try to stay in a continuous

dialogue with our customers. We usesocial networks, but we need to be

careful using these as well. You cannot

use social networks only during the week

and neglect them over the weekend.

If you have a serious outage, and you

announce it using social media, you have

to be careful of the process. If you are not

there on Saturday or Sunday and there is

an outage, then the fallout will be great,

and you have no control anymore. So

social media requires 24/7 attention. This

is something new weve learned already,

but we can also use social media for

customer care. There are some experts

within our customer bases who are keen

to support other customers. So we have a

blog, for example, in Facebook. Our users

help other users cope with challenges that

come from their phones or somewhere

else. This is a background customer care

process.

On a regular basis, we invite some

customers to round table discussions

to get feedback on what they expect,

whether they are confident with the

network, and what they are missing.

Concentration on real needs

We can offer the ful l range of

broadband services, but at the end of the

day, we have to look at our customer

bases, which are predominately German.

These customers buy their phones at the

retailer. What are their real demands? We

typically dont win out on speed tests;

thats usually Vodafone and T-mobile in

the German market. But we have other

questionnaires where customers weigh

up what they get in speed and what

they have to pay for voice. You do not

necessarily need to be the fastest, but the

total package you offer has to be above

all relevant.

We concentrate more on smartphonesthan dongles because business customers

are typically not our customer base.

Smar tphone use r s migh t have a

completely different set of needs in terms

of speed and volume than the dongle

users.

Customer experience lab

Last but not least, we decided to

cooperate with the Technical University

of Chemni tz to bui ld a cus tomer

experience lab where we want to

trial a small LTE network. We want

to determine the experience from an

end-user perspective in terms of data

compression and video streams. We want

to determine levels and what is acceptable

from the customer perspective. We have

not only technicians involved but also

psychologists in these trials.

T h e e v o l u t i o n o f m o b i l e


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Introduction

Network carr iers are facing

c o n t i n u e d d e m a n d f o r

bandwidth and capacit y in

metro, regional, and long-haul networks.

Traffic is growing at around 2 dB per

year, and this growth is driven by more

and more video streaming as well as

the proliferation of cloud computing,

data centers, social media, and mobile

data delivery. Currently, 100 Gb/s

optical systems are based on a single-

carrier polarization division multiplexed

quadrature phase shift keying (PDM-

QPSK) modulat ion format that is

associated with coherent detection and

digital signal processing (DSP). Such

systems have become commercially

available and are expected to be widely

deployed over the next few years. Optical

transport with a per-channel bit rate

beyond 100 Gb/s is now in the R&D

stage and is designed to sustain traffic

growth, improve spectral efciency, and

lower cost per bit in fiber transmission.

A data rate of 400 Gb/s per channel is

a natural and promising step when we

consider both the evolution of datacom

and transport interface speed and

implementation complexity. Among the

many proposed approaches to scaling

channel capacity to 400G, there are three

Zhensheng Jia received his B.E. and M.S.E degrees from Tsinghua University, China.

He received his Ph.D. degree from Georgia Institute of Technology, USA. Prior

to joining Optical Labs, ZTE USA, he was a senior research scientist at Telcordia

Technologies (formerly Bellcore). There, he worked on architecture design of core

optical networks and photonic signal processing. Dr. Jia has authored or co-authored

more than 100 peer-reviewed journal articles and conference papers. He was a

recipient of the IEEE/LEOS Graduate Students Fellowship Award and PSC Bor-UeiChen Memorial Scholarship Award. He was also a recipient of the Telcordia CEO

Award in 2011.

By Zhensheng Jia

400G DWDM

Technologies and Perspectives


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Figure 1. Scaling channel capacity to 400 Gb/s, OSNR = 0.1 nm.

main approaches (Fig. 1). The first of

these approaches is to continue increasing

the signal baud rate from 28 Gbaud to

112 Gbaud by using the same QPSK

format. The second of these approaches

i s t o u s e q u a d r a t u r e a m p l i t u d e

modulation (QAM) formats because they

can achieve higher spectral efciency than

PDM-QPSK formats. However, this higher

spectral efciency comes at the expense of

greatly reduced transmission distance. To

take advantage of existing optoelectronic

components and the low optical signal-

to-noise ratio (OSNR) requirement of

QPSK, multiple optical carrier techniques

such as two-subcarrier 16QAM, optical

frequency division multiplexing (OFDM),

and Nyquist WDM have been proposed

for transporting at data rates beyond 100 Gb/s.

Here, we review progress on spectrally efficient

long-haul optical transmission systems at

400 Gb/s. Taking spect ral eff iciency

and transmission reach as the main

benchmarks for optical transmission, we

discuss the potential of single and multiple

optical-carrier techniques.

Increasing the Baud Rate

Todays 100 Gb/s commercial systems

or 400 Gb/s dual-carrier prototypes

are limited to around 30 Gbaud when

transporting QPSK signals in coherent

detection. To further explore the benefit

of QPSK on both transmission distance

and spectral efficiency in the system,

we generated 40 433.6 Gb/s WDM

channels at an unprecedented symbol

ra te of 108.4 Gbaud (which was

achieved by OTDM). We successfully

transmitted signals over 2800 km SMF-

28 with 80 km per span and EDFA-only

amplification. Each channel occupies

100 GHz, and this yields a spectral

efciency of 4.05 b/s/Hz. Fig. 2 shows the

experimental setup for the generation and

transmission of 40 433.6 Gb/s OTDM

PDM-QPSK signals. The I/Q modulators

have 3 dB bandwidth of 32 GHz. They

are driven by 54.2 Gb/s PRBS binary

signals and are used to simultaneously

modulate 54.2 Gbaud QPSK signals on

optical carriers. Two cascaded intensity

modulators with 3 dB bandwidth of

38 GHz are driven by synchronized

27.1 GHz sinusoidal clock signals.

These modulators are used to carve the

QPSK signal in order to generate anRZ-QPSK signal with the 3 dB pulse

width of approximately 3.5 ps (Fig. 2,

inset a). After optical multiplexing and

polarization multiplexing, the signals are

spectrally filtered, combined, and sent

to the transmission link, which consists

of five 80 km spans of SMF-28. In the

coherent receiver, after 50 GHz balanced

detection and polarization/phase diverse

hybrid, sampling and digitization (A/D)

is performed in the Lecroy commercial

digi tal scope. The scope has four

electrical ports of super bandwidth,

and each port has a sampling rate of

up to 120 GSa/s and 45 GHz electrical

bandwidth. As well as the conventional

DSP (for channel equalization, timing

recovery, and carrier recovery), a

post one-bit delay-a nd-add fil te r and

simplified Viterbi-based maxi mum

likelihood sequence estimation (MLSE)


Line rate Baud rate Sampling rate Mod. format Bits/symbol Spectralefciency

OSNR@BER=1E-3

112 Gb/s 28 Gbaud 56 GSas/s DP-QPSK 2 2 b/s/Hz 12.6 dB

224 Gb/s 28 Gbaud 56 GSas/s DP-16QAM 4 4 b/s/Hz 17.4 dB

448 Gb/s 112 Gbaud 224 GSas/s DP-QPSK 2 4 b/s/Hz 19.3 dB




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are used to suppress noise and linear

crosstalk and to decode the symbols.

The measured optical spectra of

1 nm resolution are shown in Fig. 2 (inset

b). The corresponding constellations before

and after postfiltering are also shown

in Fig. 2 (inset b). The measured BER

results are shown in Fig. 2 (inset c). After

transmission, the BER for all channels

is less than 3.8 10 -3, which is the hard-

decision pre-FEC th reshold. These

results show the feasibility of creating

400 Gb/s single-carrier channels with

PDM-QPSK modulation but without

sacricing transmission distance.

Increasing the Number of Bits per

Symbol

Higher-level QAM formats can be

used to achieve spectral efficiency that

is greater than that of PDM-QPSK, but

this comes at the expense of greater

implementation complexity, a higher

requirement for receiver sensitivity, and

reduced optical reach. A dual-carrier

approach using 16QAM on 75100 GHz

grid is an attractive solution considering

performance requirements and the limitations

of existing technology. Here, we investigate

37.5 GHz spacing and 50 GHz spacing,

which corresponds 75 GHz and 100 GHz

optical occupancy. Three independent

lasers with 75 or 100 GHz wavelength

spacing are used as the light sources.

The generated 4-PAM electrical eye

diagram is shown in Fig. 3 (inset a).

The optical sources are combined and

then IQ-modulated to generate optical

16QAM signals at 112 Gb/s. After being

boosted by a PM-EDFA, the signals are

divided into two copies by a 50:50 OC.

The signals at the lower arm pass through

a polarization multiplexer (PMUX) to

emulate 224 Gb/s Dp-16QAM optical

signals, and those at the upper arm are

optically modulated by a 37.5 GHz or

50 GHz clock to generate double optical

sidebands with central optical carrier

suppression (OCS). After transmission,

a fully integrated optical front-end is

used to transform the optical field into

an electrical field, and then an ADC

with digital bandwidth of 20 GHz and

sampling rate of 80 GSa/s is used. After

DSP, the measured BER is as shown in

Fig. 3 (inset b) for given transmission

distances of 760, 940, and 1120 km and

37.5 and 50 GHz channel spacing. Below

the limit of 3.8 10-3, 37.5 GHz WDM is

potentially capable of 950 km transmission.

The 50 GHz WDM performs better and is

capable of 1130 km transmission.

Increasing the Number of Carriers

Using Nyquist WDM or OFDM topack together a number of est ablished

PM-QPSK channels is another practical

way of achieving 400G transmission.

T h e o r e t i c a l a n d e x p e r i m e n t a l

comparisons show that Nyquist WDM

is much more tolerant of intercarrier

i n t e r f e r e n c e ( I C I ) a n d h a s l e s s

implementation constraints. In Nyquist

WDM, the subcarriers are spectrally

shaped so that their occupancy is close

to or equal to the Nyquist limit. In this

implementation, the optical multiplexer

with narrowband filtering performs

aggress ive spec t rum shaping and

multiplexing to obtain Nyquist spacing.

However, in the intra- and interchannels,

crosstalk induced by spectral shaping

greatly limits transmission performance.

The idea previously proposed for the

digital filter and simplified MLSE

algorithm can also be employed in a

Figure 2. 40 433.6 Gb/s OTDM PDM-QPSK signal generation,

transmission, and coherent detection.

IM: Intensity Modulator

DL: Delay Line

PM-OC: Polarization Maintaining Optical Coupler


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Tech Forum

multicarrier scheme for 400G channels.

Here, we experimentally demonstrate

a 400G generation and transmission

solution based on quad-carrier PM-

QPSK at a total channel line rate of

512 Gb/s. The channel-spacing-to-

symbol-rate ratio can be brought down

to only 0.78, which yields a net SE of

4 b/s/Hz. Fig. 4 shows the experimental

setup for 400G transmission based on

quad-carrier PM-QPSK at 4 b/s/Hz. This

contains a 100 GHz inline wavelength-

selective switch (WSS) in recirculating

loop in order to determine the maximum

transmission distance and the highest

number of ROADMs tha t can be

potentially achieved and passed. We use

8 external cavity lasers (ECLs) as a CW

light source array and group them into

even and odd channels spaced at 25 GHz.

Assuming there is soft-decision FEC and

protocol overheads, all the PM-QPSK

channels at 128 Gb/s are agg res sively

shaped in the spectrum domain and

simultaneously combined using a 25 GHz

WSS. In the end, there were 8 128 Gb/s

channels generated on a 25 GHz grid. This

can be viewed as two independent 400G

(512 Gb/s quad-carrier PM-QPSK)

channels (Fig. 4, inset a).

Fig. 4 (inset b) shows the received

op t i ca l spec t rum a f t e r 2400 km

transmission with 20.4 dB delivered

OSNR. The results show that 400G

transmission using quad-carrier PM-

QPSK is possible over at least 2400 km

on a 100 GHz grid, and the net spectral

efciency of 4 b/s/Hz.

Summary

1 0 0 G p e r c h a n n e l i s a l r e a d y

established in the transport market, and

400G is the next logical step to handle

an ever-increasing amount of data

traffic. ZTE is leading the industry in

400G R&D and has explored a number

of schemes for potential use at 400G

per chan nel transmission link. There

are multiple approaches for scaling

channel capacity beyond 100G over

metro and long-haul distances. Dual

carrier DP-16QAM, which is currently

favored by the optical industry, has

a meaningful t ransmiss ion reach

for regional and metro applications.

Howeve r , f u r the r i nves t i ga t i ons

are needed to fully understand thepotential for long-haul DWDM systems.

Solutions based on DP-QPSK can

improve spectral efficiency without

sacricing transmission distance, which

means that long-haul distances are still

reachable at the expense of either higher

bandwidth requirement for transmit ter

and receiver components or increased

density of parallel integration. Any

adop ted app roach mus t no t on ly

have high SE and receiver sensitivity

but a l so be i mplement able u s ing

c o s t - e f f i c i e n t t e c h n o l o g i e s a n d

components. As the whole industry

m o v e s t o w a r d s n e x t - g e n e r a t i o n

t r a n s m i s s i o n s p e e d s , s t a n d a r d s

organizations must work together,

as was the case with 100G optical

interfaces. We should learn from 40G

mistakes in order to avoid falling into

the same traps.

Figure 4. Quad-carrier PM-QPSK 400G transmission setup.

Figure 3. PM-16QAM transmission setup.


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Tech Forum

By Ying Shen, Andrey Kochetkov and Thanh Nguyen

Evolution of Microwave Radio forModern Communication Networks

Mobile Data Explosion

Demand for mobi le da ta i s

soaring worldwide and this

b o o m i s j u s t b e g i n n i n g .

The mobile industry predicts a ten to

eighteen-fold increase in mobile data

traffic between 2011 and 2016. Huge

growth, driven largely by smart phones

and tablets, will funnel through mobile

wireless networks.

These predictions are overwhelming

for any service provider looking toprepar e it s cellul ar networks for the

demands of users addicted to mobile

data. Small cells, carr ier WiFi, backhaul,

and backbone f iber ne tworks are

solutions to meeting increased demand.

The following equation is used to

determine network capacity:

Network capacity (bps) = quantity of

spectrum (Hz) cell spectrum efciency

(bps/Hz) number of cells

The easiest way to cope with data

traffic is to increase the number of

cells by having more small cells. Fig. 1

shows cell sizes over the past 70 years

as demand for capacity has increased.

4G LTE and small cells will inevitably

follow the trend of shrinking cell size.

Microwave Radio for Small Cells

A heterogeneous ne twork i s a

combination of small and macro-cell

layers. Small cell base stations aretypically deployed in addition to the

existing macro layer.

The key features of a small-cell

backhaul are low capex and opex, fast

deployment, and ubiquitous reach. Small

cell base stations can be deployed in

small trafc hotspots, line of sight (LOS)

and non line-of-sight (NLOS) locations,

and over short and long distances.

Backhaul is a key challenge. Fig. 2

shows all available frequency bands formicrowave radio applications.

The top three small-cell backhaulcandidates are:

ber

NLOS sub-6 GHz MIMO

millimeter-wave point-to-point LOS

radios at 60 GHz or E-bands.

There is no single solution, and the

combination of these three technologies

is determined according to cell location,

coverage size, and capacity requirements.

Fiber is selected whenever it is

available because it has extremely largecapacity.


Figure 1. The trend of shrinking cells.

100,000

10,000

1,000

100

100Watts

10Watts

1Watts

100mW

10mW

1950 1960 1970 1980 1990 2000 2010 2020

Cell

Radius

(Feet)

Maritime MobileHF Radio Service

(~300mi)

WWAN(~0.6-2mi)

WLAN

WPAN

PCSMicrocells(~0.5-2mi)

2.5GMicrocells

(~2mi)

MetrolinerTrain

Telephone(~15mi)

MJ-MK Mobile

Telephone(~60mi)

2GCellular

ExpandedService(~4mi)

1GMacrocellularSystems(~8mi)

280,000mi2

10,000mi2

700mi2

200mi2

50mi2

12mi2

0.75mi2The 2G

"Sweet Spot"

3G/WimaxSweet Spot

4G/LTESweet Spot

Small CellSweet Spot

Mobile/PortableMaximumPowerOutput

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Tech Forum

NLOS sub-6 GH z MIMO ca n be

selected in 2.4 GHz, 2.6 GHz, 3.5 GHz,

5.4 GHz, and 5.8 GHz bands. Because

it does not require LOS, it allows for

easier planning and installation, and it

has ubiquitous reach. However, it also

has narrow channel bandwidth at 10, 20,

or 40 MHz, co-channel interference, and

strong shadow fading.

Millimeter-wave point-to-point

radios at 60 GHz or E-band at 7086 GHz

provide wide channel bandwidths of 250

MHz and 500 MHz and can support high

traffic capacity of more than 2.5 Gbps.

Radios in the unlicensed 60 GHz band and

in the loosely licensed E-band have high

frequency reuse and minimum frequency

planning because of their fast attenuation

and high oxygen absorption. These

millimeter-wave radios are also highly

immune to interference and have almost

no selective fading and fog attenuation.

They are quick to deploy and require low

capex and opex. On the other hand, they

are line-of-sight only and are not veryscalable.

Sma l l - ce l l backhau l has t he

following features:

can be mounted on a light pole,

utility pole, wall and roof top instead

of traditional pole and tower

environment friendly, no parabolic

antenna

can be quickly and easily installed in

less than 20 minutes

low power consumption, PoE is

preferred, less than 25.5 W

one box solution, high integration

with small cells

can be integrated with a GPS receiver

for future unit tracking, service and

replacement

LOS: 1 Gbps typical, full duplex,

one-way latency less than 50 s per

hop

NLOS: 15 0 M bps t y pica l , f u l l

duplex, one-way latency less than 1

ms per hop

support links of up to 400 m with

99.99% availability

low cost.

Microwave Radio Transition to Full IPPacket based IP/Ethernet transport

has many advantages over traditional

TDM:

unified platform to consolidate

disparate transport networks for

different trafc types

lower cost to deploy and maintain

more efcient bandwidth use

easily scalable to accommodate

growing capacity demands.

Over the past decade, microwave

radios have transitioned from TDM

only to TDM and IP/Ethernet hybrid

and f inal ly to ful l IP/Ethernet . A

sophisticated network processor became

a mandatory part of the radio that

provides comprehensive layer 2, layer

3, and multiprotocol label switching

(MPLS).

MPLS brings the best of TDM

networks to packet IP/Ethernet networks.

It ensures connection between two

endpoints, and QoS is guaranteed by a

service-level agreement.

Synchron iza t i on d i s t r i bu t ion ,

which was a common function in TDM

radios, is a big challenge in IP/Ethernet

networks. Two solutions are widelyadopted:

synchronous Ethernet . T his i s

designed to distribute a reference

frequency on the physical layer of the

Ethernet network.

IEEE 1588v2 precision time protocol.

This distr ibutes both t ime and

reference frequencies.

Mic rowave r ad io has t o mee t

strict synchronization distribution

requirements of ITU-T G.8262 to satisfy

the demands of 4G LTE networks.

Two Highs and Two Lows

Microwave radios continue to be

the key deployment solution for mobile

back haul netwo rks and t radit io nal

private networks. Microwave radios are

moving towards high throughput, high

output power, low power consumption,

and low cost.


Figure 2. Frequency bands for microwave radios.

10 20 30 40 50 60 70 80 90

Sub 6GHzBands

6-42GHz Licensed Bands Unlicensed 60GHz and Light Licensed E-Band

60GHz42GHz

42GHz

32GHz

28GHz

26GHz

23GHz

18GHz

15GHz

13GHz

10/11GHz

7/8GHz

5.8

GHz

5.4

GHz

3.5

GHz

2.6

GHz

2.4

GHz

6GHz

70/80GHz

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Tech Forum

H i g h t h r o u g h p u t i s t h e m o s t

impor t an t r equ i r emen t fo r nex t -

generation wireless data networks. Thefollowing techniques are used to achieve

high throughput:

high bandwidth and high frequency

bands

ETSI: 3.5/7/14/28/56 MHz and

moving to 112 MHz

FCC: 5/10/20/30/40/50 MHz

60 GHz/E-band: 250 MHz and 500 MHz

high modulation

QPSK/16/32/64/128/256 QAM and

moving to 512/1024 QAM

2048 QAM and 4096 QAM coming

cross-polarizat ion interference

cancellation (XPIC)

header and packet compression

up to 30% L2 compression is possible

for 64 byte packets

compression ratio is statistical (on

large packets becomes negligible)

combined L2+L3 (IPv4+UDP) can

provide up to 100% gain for 64 byte

packets

IF/RF combining

MIMO: multiple input/multipleoutput and spatial combining.

High ou tpu t power con t inues

to be an impor tant parameter for

microwave radios. Output power is

directly linked to system gain. For

the same system gain, higher output

powe r can be accommodated with

smaller antennas and towers and with

lower installation cost. High output

pow er and dynamic range are the

main competitive features. Common

techniques for achieving high output

power are

high P1dB/IM3 power ampliers

high efficiency GaN devices with

pre-distortion techniques

Doherty amplier

various pre-distortion techniques

power combining.

Low power consumption is a new

trend and key to green branding.

Ecological solar base stations will

become more and more popular. Power

over Ethernet (POE) and longer-lasting

solar batteries are rm requirements formicrowave radios to have low power

consumption. Modern techniques for

reducing power consumption include

pre-distortion

adaptive analog pre-distortion

adaptive digital pre-distortion

open loop digital pre-distortion

remote adaptive digital pre-distortion

bias

class AB, class B/C, and class F

adaptive bias per envelop detecting

xed bias per output power level

common rail devices

C M O S a n d S i G e l o w p o w e r

consumption devices

high efciency DC/DC converters

optimized system designs

alternative energy, integrated with

solar power generating devices.

Low cost is always the ultimate goal,

not for devices but also in overall system

design, mass production processes,

installation and manufacturing. Low costinvolves:

highly integrated system on chips

using either CMOS or SiGe processes

design for various applications

design for installation

design for test and manufacturing

design for system integration with

base station.

Summary

Microwave radios are transitioning

from split, outdoor radios to one or

two boxes integrated with a small-

cell base station and WiFi (Fig. 3).

With the wireless data network, full IP

with standard multi-gigabit Ethernet

connection is mandatory. The mobile

and wireless industries have succeeded

beyond expectation. Microwave radios

will continue to be a critical part of growing

wireless data networks.


Figure 3. Microwave radio trend for wireless data networks.

SplitRadio

AllOutdoor

Radio

AllOutdoor

Radio

SolarStation

60G/E-bandRadio

IntegratedBBT withBackhaul

Radio and WiFi

Mini BBT

Mini BBT

Two Box Macro CellStation

One Box Small CellStation

Two Box Small CellStationAll Outdoor RadioSplit Radio

Generator GeneratorBaseStation

BaseStation

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Key 100G Technologies

A 100G WDM system needs to

be applicable to a long-haul backbone

network with a radio repeater

transmission distance of more than

1500 km

be applicable to a metro core network

with a radio repeater transmission

distance of up to 300 or 400 km

support a wavelength spacing of

50 GHz

be compatible with existing WDM

systems so that it does not affectthem or put them at risk

have chromatic dispersion (CD)

tolerance and polarization mode

d i s p e r s i o n ( P M D ) t o l e r a n c e

equivalent to or superior to 10G

WDM

support cascading of mult iple

reconfigurable optical add-drop

mul t i p l exe r s (ROA DMs) , f o r

example, more than ten ROADMs

r educe cos t f o r a l a rge - sca l e

application. The price of one 100G

WDM system is less than that of ten

10G WDM systems.

To meet these requirements, 100G

WDM must have a cutting-edge optical

modulation scheme and forward error

correction (FEC) with high coding gain

on the line side, CFP transceiver modules

on the cl ient s ide, and integrated

optoelectronic chips.

Driving Force

The rapid growth of mobile

Internet and HD video services

has increased the need for

network high bandwidth. To meet this

need, operators have introduced 100G

WDM into their transport networks.

The bandwidth of China Telecomsbackbone IP networks will increase 40 to

50 percent year on year for the next ve

years, which represents a real increase

from 64 Tbit/s to 128 to 160 Tbit/s

over the next ve years. With explosive

growth in the number of data services,

especially P2P and web video services,

the pressure on telecom networks has

extended from the access layer to the

backbone layer. This often means the

backbone needs to be overhauled.

A 100G high-speed core router is

60 percent more efficient than a 10G

router. The 100G router simplifies

management, consumes less power, and

is highly integrated. 100G routers and

data services are the driving force behind

the growth of 100G WDM. Today,

100G transport has become the focus of

attention for leading telecom operators

and vendors worldwide.

100G WDMHeralds the Ultra-Broadband EraBy Teng Weicai



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used, a 100G WDM system requires 10 dB

higher OSNR tolerance than a 10G system.

The PMD and CD tolerances in a 100G

system are one tenth and one hundredth

that of 10G, respectively. Therefore,

advanced technologies must be used to

ensure the feasibility of a 100G system.

Optical coherent detection and balanced

optical receiving can improve OSNR

tolerance by approximately 6 dB.

Polarization of PM-QPSK signals

var ies randomly af te r long-haul

transmission, and the local optical

oscillator at the receiver receives optical

signals with frequency and phase

differences. Therefore, high-speed digital

signal processing (DSP) is the best

solution to address these issues. High-

speed DSP technology is also central to

100G transmission.

After DSP, a 100G WDM system

has significantly improved tolerance

to CD and PMD. CD tolerance ismore than 40,000 ps/nm, and PMD

tolerance is more than 30 ps. Dispersion

compensation fibers are therefore

unnecessary for the transmission links.

This not only mitigates non-linear effects

but also improves line OSNR.

It is difcult to develop ASIC chips

for high-speed ADC (above 50 GSs/s)

and for high-speed DSP. It is also difcult

to integrate optical components and

reduce power consumption. These are

the most difficult issues in developing

and commercializing 100G equipment.

ZTE 100G WDM Solution

Through the joint efforts of the IEEE,

ITU-T, and OIF, 100G standards have

been drafted. Mature 100G standards

pa ve the wa y fo r wide sp re ad 10 0G

deployment. ZTE has rolled out an

industry-leading 100G WDM solution to

each with a baud rate of 28 to 32 Gbit/s. Each

two of the four subsignals are modulated

with differential QPSK and two output

QPSK signals are modulated again with

PM-QPSK. In this way 100G PM-QPSK

optical signals are generated.

Because subsignals with baud rates

of 28 to 32 Gbit/s have a narrow optical

spectrum, they can support 50 GHz

wavelength spacing and transmission

through multiple OADMs.

When the same modulation format is

The optical modulation scheme on

the line side is key to the performance

of a 100G WDM system. 100G optical

modulat ion is currently based on

quadrature phase-shift keying (QPSK). A

combination of QPSK, FDM, PM-QPSK,

and OFDM is necessary for 100G optical

modulation. The Optical Internetworking

Forum (OIF) has recommended using

polarization mode QPSK (PM-QPSK) in

long-haul 100G transmission. An OTU4

signal is divided into four subsignals,

Figure 1. PM-QPSK transmitter.

Driver 3

*Optional RZ Carver

RZ* BS

Modulator 4

Modulator 3

Modulator 2

Modulator 1

Pol Rot

X-pol

V-pol

BC

Driver 2

Driver 1

Driver 4

Laser

Figure 2. PM-QPSK coherent receiver.

Signal

LO

Laser

X-Pol

Y-Pol

90 deg

Hybrid

Mixer

90 deg

Hybrid

Mixer

I

I

Q

Q

XIP

XIN

XQP

XQN

YIP

YQP

YIN

YQN

Pol Rot

BS

PBS

TIA

TIA

TIA

TIA



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optical networks. According to data

released by OVUM, the 100G WDM

market was launched in 2012 and is

gradually entering a stage of large-scale

commercialization. 100G WDM will

almost certainly replace existing 10G

WDM and edge out 40G WDM. ZTE

is poised to offer industry-leading

100G solutions for the ultra-

broadband era.

meet the need for large-scale commercial

100G. ZTEs 100G WDM system

supports 80 channels in the C-band, and

the same 50 GHz channel spacing is used

in both 10G and 40G WDM systems.

The transmission capacity of ZTEs

solution is up to 8 Tbit/s, ten times the

capacity of a 10G WDM system. This

meets the increasing demand for data

services and ensures a longer equipment

lifecycle.

ZTEs 100G WDM system uses

PM-QPSK modula t ion , coherent

d e m o d u l a t i o n , a n d e l e c t r o n i c

equalization and compensation. An

optical receiver can tolerate CD of up

to 50,000 ps/nm and PMD greater than

30 ns. This means that CD and PMD

do not need to be considered in 100G

deployment, and CD compensation

modules (DCMs) for fiber links do not

need to be used. The engineering and

OAM for 100G WDM equipment issimplied.

ZTE has developed its own 100G

ASIC chips for coherent opt ica l

detection. The 100G ASIC chips are

manufactured using a cutting-edge 40 nm

CMOS process. This process allows the

system to be highly integrated, consume

less power, and have better signal

processing capability tha t a 90 nm or

65 nm CMOS process. Operators can

reduce power supply in the equipment

room, become environmentally friendly,

and save on OAM costs.

Z T E s 1 0 0 G W D M s y s t e m

uses industry-leading soft decision

forward-error correction (SD-FEC) to

lower OSNR tolerance and improve

transmission capability and distance.

SD-FEC with an overhead of 18 to 20

percent recommended by OIF allows

for a net coding gain of up to 10.5 dB.

High-speed DSP technology is also

used to enhance transmission capacity

for low cost. A 100G WDM system

can transmit over more than 1500 km

without electronic regeneration. Such

transmission capacity is close to that of a

40G WDM system.

ZTE has been preparing for 100G

commercialization by cooperating

with operators to test its 100G WDM

products. Good results have been

achieved. With the worlds best high-

pe rf or ma nc e 100G WD M pr od uc ts ,

ZTE offers the most competi t ive

100G solution. ZTEs 100G solution

features

96-channel ultralarge capacity

to help operators eliminate the

bandwidth bottleneck

1500+ km long-haul transmission

without electronic regeneration

advanced DSP technology for

improving tolerance to CD andPMD. The transmission distance

can extend to 2500 km without

CD and PMD compensation.

This saves investment and

makes the system easier to

maintain.

large-capacity electrical

cross-connect at ODU0,

ODU1, ODU2, ODU3 and

ODU4. This can provide

network convergence

nodes with exible trafc

grooming.

hybrid 10G/40G/100G

t r a n s m i s s i o n a n d

smooth upgrade from

10G to 40G and 100G.

The ultra-broadband

era is approaching fast,

and operators worldwide

are overhauling their


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OTN and 100GThe Inevitable Choice for Future

Optical NetworksBy Pan Kai and Zhang Runmei

Optical network data transmission

has entered a new era of large-

granularity service. Business

growth and mature optical transport

networks (OTNs) have triggered this

revolution in data transmission. As

the number of fixed broadband users

increases, IPTV networks are being

deployed on a large scale, and a variety

of broadband applications are emerging.

The requirement for bandwidth in thebackbone transport network is growing

rapidly.

According to data released by the

Optical Internetworking Forum (OIF),

average annual growth in operator trafc

is much higher than the annual growth

in operator revenue. The cost per unit

of traffic has to be reduced to relieve

pressure on revenue. The most effective

means of lowering TCO is to improve

transmission capacity. Through the

joint effort s of the IEEE, ITU-T, and

OIF, 100G standards have been drafted.

Vendors worldwide have released or

will soon release 100G products, and the

100G era is just around the corner.

OTN Status Quo and Trends

OTN is an important transport-

layer technology designed for next-

gene ra t i on h igh - speed t r anspor t

MSTP network on core and backbone

layers of an incumbent MAN is suitable

for transporting TDM services, but the

demand for data services is skyrocketing.

Therefore, the WDM network needs to

be built and expanded to accommodate

fast-growing data trafc.

IP-based services are uploaded to the

incumbent WDM network over the POS

or Ethernet interface. This may cause

problems in ne tworking, protec tion ,

and OAM. When conditions permit,

the WDM network can be upgraded to

support G.709 OAM functions. A newly

built WDM system that has no MSTP

network must support the G.709 OAM

functions and protection switching based

networks. It leverages the advantages of

traditional SDH/SONET and WDM and

is compatible with them. In 1998, the

ITU-T put forward the OTN concept and

dened its architecture. With broadband

data services and increasingly mature

optical transport technologies, it is

inevitable that OTN will be used to build

more efficient and reliable transport

networks.

On the optical layer, OTN can

process large-granularity services, similar

to a WDM system. On the electrical

layer, OTN uses asynchronous mapping

and multiplexing so that the most cost-

effective space division technology can

be used for key cross connections. The

Core Layer

Service Access Control Layer

Convergence Layer

Access Layer

IP-based Private

NetworkCore Network

CR CR

BMSG

OTN

OLTSwitch

HSIHSI

Splitter

ONU

Splitter

BTS NodeB

ONU

xDSL

IPTV

MSTP/

Packet

Network

MSTP/

Packet

Network

Convergence

Switch

VIP Customer

Service

OTN

MGW SGSNMSC

BSC RNC

Figure 1. OTN deployment in a MAN.



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on the optical layer. In other words, OTN

takes over corresponding functions of

the MSTP network. Leveraging MSTP

technical advantages, OTN can better

meet the need for growth of broadband

business.

OTN Deployment in MAN

100M acces s wi l l be a bas i c

requirement for broadband networks

in the future. To accommodate high-speed service growth, an optical network

is required to provide the necessary

bandwidth and to also allow for fast and

flexible traffic grooming and complete

OAM.

In the IP era, traditional network

architecture can no longer meet the

explos ive growth in demand for

data services. In current MANs, IP

services have gradually become the

largest service type, and there is alsogrowing demand for some la rge-

granularity services. These changes

call for intelligent, IP-based, large-

capacity, and highly integrated MANs.

Operators also have a pressing need

for OTN deployment in MANs. OTN

is deployed in the convergence layer

and can be extended to the access layer

(Fig. 1). OTN is a basic plane that can

carry optical line terminals (OLTs),

convergence switches, MSTP, and packet

networks. However, there is still a clear

boundary between the OTN deployed

at the convergence or access layer and

the MSTP/packet network. OTN is only

suitable for carrying GE trafc or above,

and small-granularity services are carried

over the MSTP/packet network.

40G vs. 100G

Operators are not optimistic about

their current 40G deployments and

application prospects, so 100G has

become their focus of attention.

Standardization

The deferral of 40G standards

has resulted in the emergence of

multiple 100G solutions that are not

compatible with each other. Moreover,

40G deployments need additional

components that are complex and cannot

be widely deployed. The related 100G

standards, however, have basically

matured as a result of the joint efforts

of the IEEE, ITU-T, and OIF. These

standards lay a solid foundation for

widespread 100G deployment.

Service application

40G POS encapsulation is currently

used for 40G links of backbone routers

in China. Although 40GE systems arewell-developed, OTN devices supplied

by mainstream vendors have limited

cross-connect capacity. This means a

40GE system cannot be applied to the

40G link side. 40G can be only used for

grooming subwavelength traffic rather

than grooming full services. Problems

associated with system integration,

p o w e r c o n s u m p t i o n , a n d h e a t

dissipation have to be solved for 40G.

Because IP services have moved from

10GE to 100GE, and the related 100G

technologies have matured, the demand

for 40G is shrinking dramatically. 100G

will edge out 40G sooner or later and

become an evolution trend of OTN at

the link side.

Industry chain

The focus of leading opt ica l

component suppliers has shifted to

100G, which means less investment in

40G R&D. A shortage of 40G suppliers

has led to an increase in the prices of

optical components and has restricted the

healthy growth of the 40G market. 100G

has therefore been highly recognized

and supported by technical experts,

equipment suppliers, and chip vendors.

Because of the long return on investment

(ROI) period that stems a more than ten-

year window for 100G applications, allparties in the industry chain are investing

in 100G. This helps reduce 100G

equipment cost. Some operators believe

that the price of one 100G system is less

than that of two 40G systems. With the

growth of the industry chain, the cost

of 100G equipment will sharply reduce

over the next ten years.

In todays booming 3G and LTE

markets, OTN has played an important

role in the full-service bearer sectorbecause it has high cross-connection

capacity and is capable of exible trafc

grooming. At present, 10G OTN remains

the mainstream technology for optical

bearer networks , and 40G OTN is a

technology for transitioning from 10G to

100G.

Operators worldwide are trialing

commercial 100G networks. This lays a

sound foundation for 100G applications.

To meet the growing need for IP bearer

networks, and to keep pace with the

rapid development of transport network

technologies, the Chinese telecom

industry plans to increase investment

in OTN and 100G and speed up R&D,

standardization, and applications of

OTN and 100G equipment. OTN and

100G will be the inevitable choice for

backbone and metro core networks in

coming years.



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capacity, transmission rate, and optical

transmission distance.

There are three main methods of

increasing the channel bit rate in an ultra

100G system.

The rst method involves increasing

t he s igna l baud r a t e . Howeve r ,

transmission distance is greatly reduced

when the baud rate of polarization-

multiplexed quadrature phase-shift

keying (QPSK) or 16-QAM (used in

current 100G commercial systems

or 400G dual-carrier prototypes) is

multiplied.

The second me thod invo lves

using higher-order QAM codes. This

prod uces high er spec tr al ef fi ci en cy

than PDM-QPSK but leads to higher

imp lemen ta t i on cos t and h ighe r

requirements on reception sensitivity.

transmitted over 640 km standard single-

mode fiber. At the Optoelectronics

and Communications Conference

(OECC) 2011, ZTE unvei led the

w o r l d s f i r s t 1 T b i t / s D W D M

pr otot ype syst em and prov ided te st

results.

These achievements demonstrate

ZTEs technical strength and give a clear

direction to the development of optical

communications. ZTE believes that ultra

100G technologies will develop on the

basis of existing 100G technologies.

100G coherent detection reception, soft-

decision forward error correction (SD-

FEC), polarization multiplexing, and

phase coding format can all be applied to

ultra 100G systems.

Research on ultra 100G technologies

is underway to seek a balance between

With the emergence of HDTV,

3DTV, cloud computing,

Internet of things and other

high-bandwidth applications, demand

for network transmission bandwidth

has increased. To meet the 30 to 50

percent annual increase in bandwidth

demand, Verizon, Deutsche Telekom,

BT, Telefonica, and other large operators

are looking past 100G to ultra 100G

solutions.

ZTE estimates that 400G systems

will be commercialized by 2015 and

1T services will be commercialized

after 2018. ZTE has been committed to

researching 400G and 1T technologies

for years. At the Optical Fiber Conference

2011, ZTE announced it had transmitted a

signal with a single-channel transmission

rate of 11.2 Tbit/s. The signal was

Ultra100GTechnologiesBy Ren Zhiliang


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Transmission distance is also reduced.

16-QAM signals require an optical

signal-to-noise ratio (OSNR) that is 6 dB

higher than QPSK. This ratio increases

exponentially with the increase of

constellation points. On existing networks,

a 512 Gbit/s dual-carrier 16-QAM signal

can be transmitted about 700 km. This

implies there are many challenges in

using 16-QAM or 64-QAM to improve

spectral efciency.

The third method involves usingmultisubcarrier multiplexing super

channels. High-integration 100G/200G

channels overcome the speed and

bandwidth limitation of optoelectronic

devices. Coherent optical orthogonal

frequency division multiplexing (CO-

OFDM) and Nyquist WDM are the best-

known multicarrier techniques.

At present, the 100G technology

based on single-carrier PDM-DQPSK

modulation is capable of spectralefficiency of 2 bit/s/Hz with traditional

50 GHz spacing. Mult isubcarrier

multiplexing is capable of a spectral

efficiency of about 4 bit/s/Hz, and the

transmission distance is not signicantly

reduced.

In February 2012, ZTE joined

with DT to trial 400G/1T prototypes

based on multisubcarrier multiplexing

technology. Nyquist-WDM was used to

generate a 400 Gbit/s superchannel using

four 112 Gbit/s PDM-QPSK signals

that were multiplexed after filtering.

A 1 Tbit/s channel with 13 subchannels

was created using CO-OFDM. Each

subchannel occupied 25 GHz, and the

total signal bandwidth was 325 GHz.

With these two superchannels and ZTEs

two commercial 100G line cards, hybrid

transmission was possible. After the

signals were transmitted over 1750 km,

the bit error ratios (BERs) of all signals

were less than 2 10-3.

The trial proved that Nyquist-WDM

is an optimal solution for ultralong-haul

transmission. In addition, ZTEs 400G

and 1T technologies are compatible with

original commercial 100G technologies.Multisubcarrier multiplexing can also

work alongside the other two methods.

In the Deutsche Telekom laboratory, ZTE

tested an 8 216.8 Gbit/s PDM-CSRZ-

QPSK system on the existing network.

ZTE used Nyquist-WDM and increased

the baud rate to 54.2 Gbaud. The signals

had spectral efficiency of 4 bit/s/Hz.

After they were transmitted over 1750 km,

the BER of all signals was lower than the

forward error correction threshold. This

proved that baud rate and channel capacity

can be doubled, and ultralong-haul

transmission can be achieved using QPSK

with 50 GHz spacing.

Sub-subcarrier multiplexing and 16-

QAM modulation can be combined to

further boost spectral efciency, but there

is a lot of work to be done before they

can be used for long-haul transmission.

Channel bit rate can be enhanced

after in-depth study of these technologies,

but it is difcult to continuously improve

spectral efficiency because of the limit

defined by Shannons law. Customers

care more about the maximum product

when transmission distance multiplies

spectral efciency. Therefore, ZTE plansto launch optical modules that can use

the digital signal processing technology

of the transmitting end to dynamically

change the modulation format and baud

rate. These modules can also support

self-adaptation of line rates. The optical

modules can be used in conjunction with

a flexible electrical-layer encapsulation

and adaptation technique, and dynamic

spectrum resource allocation to create a

exible self-adaptive optical transmission

network. This will ensure ber resources

are optimally used.

ZTE will concentrate on high-speed

transmission technologies and will

research all kinds of ultra 100G devices

and network technologies. ZTE helps

network carriers address the exponential

increase in backbone network trafc that

has arisen as a result of the boom in data

services.

Figure 1. Ultra 100G research and development direction.


Number of Electrical

Subcarrier (s)

Number of ElectricalSubcarrier (s)

Number of Bits Per SymbolNumber of Optical Mode (s)

OTDM Symbol Rate (Gbaud)

Number of Optical Mode (s) Number of Polarization (s)

1

11

1

1

220 40 60

4

4

10

256

512

4

3

3

5

7

73

2

2

1

1

QPSK

30 to 50 Gbaud

16 QAM

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chromatic dispersion, polarization mode

dispersion, and nonlinear effects are

seriously affecting smooth evolution.

High-performance FEC codes are

therefore being developed so that higher

net coding gain (NCG) and better error

correction can be achieved.

An Efcient FEC TechniqueThe OSNR tolerance for 10G NRZ

is less than 12 dB when the pre-FEC

BER is 2 10-3

. However, the OSNR

tolerance for 100G PM-QPSK is around

15.5 dB when pre-FEC BER is 2

10-3

. When the same FEC is used, the

transmission distance of 100G is less

than half that of 10G. It is therefore

necessary to introduce a highly efcient

FEC technique.

Adaptive forward-error correction

(AFEC) has been widely used in 10G

and 40G DWDM systems and an NCG

of about 8.5 dB can be achieved. The

Optical Internetworking Forum (OIF)

suggests that soft-decision forward-

error correction (SD-FEC) with a

redundancy of 1820% be used in a 100G

DWDM system. The NCG can reach up to

10.5 dB, and the line rate is approximately

126 Gbit/s. With efficient SD-FEC, the

Forward error correction (FEC)

i s w i d e l y u s e d i n o p t i c a l

communications to improve error

correction, enhance system reliability,

and extend opt ica l t ransmiss ion

distance. It is also used to reduce

optical transmitter power and system

costs. In response to the rapid growth

of optical communications, the ITU-T

has started researching FEC coding

and has recommended ITU-T G.707,

G.975, G.709, and G.975.1. As optical

transmission systems evolve towards

longer transmission distance, greater

capacity, and speeds of 100G or beyond,

By Zhu Xiaoyu

A Brief Analysis ofSD-FEC

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OSNR tolerance for 100G PM-QPSK is

around 13 dB. This ensures that 100G

transmission systems cover almost the

same distance as 10G systems.

FEC Classication

FEC codes can have b lock or

convo lu t iona l s t ruc tu re s . B lock

c o d e s i n c l u d e h a m m i n g , r e e d -

solomon (RS), and BCH codes and

have been extensively used in optical

communications. Most block codes are

constructed in the Galois field and thus

have a strict algebraic structure. An

algebra-based hard-decision decoding

algorithm is used for block codes.

Convolutional codes have a dynamic

structure that can be described by a nite

state machine. A soft-decision decoding

algorithm is used for convolutionalcodes. Because convolutional codes

do not support paral lel decoding

architecture, they have a long decoding

delay. Convolutional codes are therefore

seldom used in optical communications.

FEC coding can be done using hard

decision and soft decision. Hard-decision

decoding is based on traditional error

correcting. A demodulator makes the best

hard-decision on the channel outputs,

and the demodulator sends the decision

results to a hard-decision decoder. The

decoder receives code streams, typically

0 or 1 in a binary code, and corrects

errors by using the algebraic structure.

Soft-decision decoding uses the

waveform information that is output by

channels. A real number is output by

a matched filter, and the demodulator

sends this to a soft-decision decoder.

The decoder needs not only 0 or 1 code

streams but also soft information to

indicate the reliability of these input

code streams. The further the code value

is from the decision threshold, the more

reliable the signal is, and vice versa.

Because a soft-decision decoder

has more channel information than a

hard-decision decoder, it can use the

information through probability decoding

and obtain higher coding gains than a

hard-decision decoder.

FEC Evolution

First generation

First generation FEC uses hard-

decision block codes. The typical

representative is the RS (255, 239) code

with a 6.69% overhead. When an output

BER is 1E-13, the RS code yields a net

coding gain of about 6 dB. RS (255, 239)codes have been recommended for long-

haul optical transmission as defined by

ITU-T G.709 and G.975.

Second generation

Second generation FEC uses hard-

decision concatenated codes combined

with interleaving and iterative decoding

techniques to improve FEC capability.

The ITU-T G.975.1 standard has dened

eight second-generation FEC algorithms

with 6.69% overhead. When an output

BER is 1E-15, most FEC algorithms yield

a net coding gain of more than 8 dB and

support 10G and even 40G long-haul

transmission systems.

Third generation

Third generation FEC uses soft-

decision. As the single-channel rate

evolves from 40G to 100G, a coherent

receiver is the necessary to develop

100G long-haul transmission equipment.

Coherent receiving technology in optical

communication systems and the rapid

growth in integrated circuit technology

make the application of soft-decision

FEC possible. When an output BER is

1E-15, a soft-decision FEC scheme with

1520% overhead yields a net coding

gain of about 11 dB. This is enough to

support long-haul 100G and beyond

transmission. Soft-decision FEC often

uses turbo product codes and low density

parity check codes.

ZTE 100G SD-FEC

ZTEs 100G SD-FEC scheme has the

following features:

an innovative, full soft-decision FEC

algorithm that achieves higher gains,higher integration and lower power

consumption

br an d-new, op timize d algo rit hm

and architecture. The FEC scheme

with 15% overhead now has strong

error correction performance, allows

an input BER threshold of between

1.8E-2 and 2E-2, and effectively

prevents line errors.

100% soft-decision decoding. No

concatenated hard-decision FEC

codes are necessary, and this greatly

reduces decoding delay.

innovative, optimized codeword

structure and decoding algorithm

that provides ultralow error oor

soft-decision FEC scheme with 15%

overhead that offers higher transmission

efficiency and better wave filtering

performance than an FEC scheme with

20% overhead.

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Success Stories

Outremer Telecom (OMT) offers a

full range of xed line, mobile, and

Internet services to residential and

business customers in the French overseas

departments and regions. The company

is seeking to increase its market share in

the French West Indies, which includes

Guadeloupe, Martinique, and French

Guiana, and in the Indian Ocean, which

includes Reunion and Mayotte.

O M T h a s d e v e l o p e d i t s o w n

telecommunications network in order to

lead the growing telecom market in these

regions. The companys brand Only

is well-known in all the French overseas

departments and regions.

In June 2006, ZTE began supplying

2G mobile infrastructure equipment to

OMT and helped OMT extend its network

in Reunion and Mayotte. This paved the

way for further cooperation between OMT

and ZTE. Today, ZTE has become the most

important partner of OMT. The fruitful

collaboration between both sides is driving

OMT's fast development, and OMT is now

the most competitive operator in the French

overseas departments and regions.

ZTE: A Valuable Partner for OMT

Prior to 2005, Alvarion was OMTs

main mobile network equipment vendor. It

had constructed mobile networks for OMT

in French Martinique, French Guyana,

and Guadeloupe. However, because the

capacity of the equipment was limited, each

network could cover no more than 50,000

subscribers. Alvarion could not upgrade

its network equipment or expand capacity

to meet the demands of OMT and its

subscribers.

In 2006, OMT thoroughly evaluated

alternative suppliers to replace Alvarion.

ZTE was selected as the new supplier for

new GSM projects on Reunion and Mayotte.

ZTEs leading solutions and fast delivery

By Cao Tianhua

OMTThe Leading Alternative Operatorin the French Overseas Departments and Regions


Success Stories

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Success Stories


customized solution to its new 2G projects

in Reunion and Mayotte. Commercial trials

showed that ZTEs solution was perfect.

In 2008, ZTE helped OMT replace its

2G equipment and build 3G networks in

Guadeloupe, Martinique, and French Guiana.

ZTE optimized its cabinet reuse solution

by al low ing 3G ove rl ay base d on SDR

technology. In 2011, ZTE added deep-packet

inspection and a policy and charging rules

function, both of which can help OMT developdata services and enhance the protability of

its 2G and 3G mobile networks.

3G services are essential to our

broadband s t r a tegy i n ou r ov er seas

departments and regions. We are responding

directly to the needs of our customers,

who want to benefit from unlimited voice

and data. They also want other innovative

services at attractive prices. After the

network deployment in Reunion, we

partnered with ZTE again because of ZTEs

professiona lism and great service, said

Jean-Michel Hegesippe, chairman and

managing director of OMT.

Unied OCS Solution

The five French overseas departments

and regions are located in different

t ime zones, and this makes unifying

management, service deployment, and

billing across the ve networks difcult.

ZTEs unified OCS solution is tailored

for OMT. The OCS online charging system

allows OMT to flexibly define packages

and bring together the charging functions

of OMTs xed and mobile networks. This

greatly enhances the billing capability of

OMT and allows OMT to quickly realize

unied operational support (pricing policy,

billing, and charging), unied roaming, and

unied user experience. Users can recharge

their accounts at any time when roaming inthe ve overseas departments and regions.

Today, OMTs unied network operation

center in Mauritius manages the networks

in the ve departments and regions.

Win-Win Cooperation

After five years of upgrading their

networks, OMT now has the greatest

coverage and delivers the best services

in the French overseas departments and

regions. In 2011, a third-party consulting

company tested the networks of all operators

in the French departments and regions. The

results showed that OMTs networks had

improved greatly and outperformed many

other operators.

At the end of 2011, OMT had 620,000

subscribers and a turnover of 194.3 million

euros. Its earnings before interest, taxes,

depreciation, and amortization (EBITDA)

were 58.2 million euros.

allowed OMT to commercialize the network

in early 2007. This initial cooperation

enhanced mutual trust between the two

companies. Over the following three years,

ZTE helped OMT swap over its 2G networks

and deploy 3G networks in Guadeloupe,

Martinique, and French Guiana.

Throughout the cooperation, ZTEs

products performed very well. ZTEs fast

deployment and forward-thinking services

were recognized by OMT. At the end of

2010, OMT and ZTE signed a four-year

strategic cooperation framework agreement

on mobile networks, intelligent networks,

service platform, transmission, power

systems, unified network management

systems, and terminals.

Now, ZT E pr oduc ts ac coun t for 95

pe rce nt of OM Ts pu rch ase s of RAN,

core network, VAS, and power system

equipment. Without doubt, ZTE is OMTs

most valuable strategic partner.

Customized and Cost-effective

Cabinet Reuse

The populat ions of Frances fiveoverseas departments and regions are small,

and it is difcult for OMT to grow a large

subscriber base. Therefore, reducing opex

and improving protability of data services

are top priorities when upgrading networks.

When planning the new network

deployment, OMT specified that they

wanted to make full use of existing base

station cabinets; they wanted enough room

reserved to deploy future 3G services; and

they wanted to allow for smooth evolution

to LTE. OMT also wanted the network to be

completed as soon as possible.

ZTE put together a special R&D team

to work on the issue of cabinet reuse. ZTE

took into account the structure of existing

2G cabinets and came up with a highly

integrated modular design so that the 2G

cabinets could accom modate 3G SDR

technology.

In early 2007, OMT applied this

Milestones

June 2006. ZTE won the contract for OMTs two new GSM projects on French Reunionand Mayotte. The network was commercialized in early 2007.

July 2007. ZTE won the contract for OMTs 2G swap-over on Mar tinique. This involvedreplacing the 2G equipment of Alvarion and deploying 3G networ

Documents

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