TD-SCDMA Standards and Technology Evolution

safflowerpepperoniΚινητά – Ασύρματες Τεχνολογίες

24 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

156 εμφανίσεις

TD
-
SCDMA Standard
s

and Technology Evolution


TD
-
SCDMA Forum



ITU
-
R RA
-
2000 approved
the recommendations on
3G
mobile communication
techn
ology

specification
s
including those of TD
-
SCDMA

in May 2000. In March 2001,
3GPP

fulfilled

TD
-
SCADMA Low Chip Rate
(L
CR)

standardization

in Release 4.
T
he improve
d

R4 and R5
specifications ha
ve

newly added function points including HSDPA, air interface base station
synchronization, termina
l

location (AOA
-
aided location), etc. CCSA
is

to promote the integration
of R4 and
R5, including HSDPA extension on multi
-
carrier. In March 2005, R6
containing uplink
enhanced technology (still in study) and
MBMS (multimedia broadcasting/multicast)

was frozen.
However,
proposals can still be made
due to
the
instability

of R6
.
In t
he futu
re
,

TD LTE
should
study more the

MC
-
TD
-
SCDMA and OFDM
-
based TDD technology.


Figure 1 TD
-
SCDMA Evolution


CCSA

has
developed
industry standards
of

technical requirements for TD
-
SCDMA equipments
and test methods, completed research reports on IP
-
based RAN
, multi
-
antenna, and
HSDPA
, and
conducted pre
-
research on standards for test methods of
TD
-
SCDM
A Enhanced,
TD
-
SCDMA P2P
,
TD
-
SCDMA HSDPA

Multi
-
carriers, and
TD
-
SCDMA Iur
.
In terms of TD
-
SCDMA network
s,
8
standards of technical requirements and test methods
have been studied, of which 5 are for
equipment
, i.e.,
2GHz TD
-
SCDMA wireless access equipments

and
terminals (
V
olumes

I and II
),
and
3
for
interfaces

including Iub and Uu interface
s
.


On January 20
th
, 2006, the Ministry of Information Industry issued the

TD
-
SCDMA

Version 1
,
with
a total of
23 recommended communication industry standards, including
TD
-
SCDMA

terminals/test specifications, wireless access equipment/test specifications, and technical
specifications for wireless access interfaces. The
titles

a
nd number
s

of
the
standard
s

are as
follows:




No.
YD/T

1365
-
2006

Technical
R
equirements for
Wireless

Access Equipment of 2GHz
TD
-
SCDMA Digital Cellular Mobile Communication Network



No.
YD/T

1366
-
2006

Test Methods for
Wireless

Access Equipme
nt of 2GHz TD
-
S
CDMA
Digital Cellular Mobile Communication Network



No.
YD/T

1367
-
2006

Technical Requirements for User Equipment of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network



No.
YD/T

1368.1
-
2006

Test Methods for User Equipment of 2GHz TD
-
SCDMA Digital
Ce
llular Mobile Communication Network Part I: Tests of Basic Functions, Services and
Performance



No.
YD/T

1368.2
-
2006

Test Methods for User Equipment of 2GHz TD
-
SCDMA Digital
Cellular Mobile Communication Network Part II: Tests of Network Compatibility



No.
Y
D/T

1369.1
-
2006

Technical Requirements for
Iub

Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Part I: General Principles



No.
YD/T

1369.2
-
2006

Technical Requirements for
Iub

Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Commun
ication Network Part II: Layer 1



No.
YD/T

1369.3
-
2006

Technical Requirements for
Iub

Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Part III: Signaling Transport



No.
YD/T

1369.4
-
2006

Technical Requirements for
Iub

Interface of 2GH
z TD
-
SCDMA
Digital Cellular Mobile Communication Network Part IV:
NBAP

Signaling



No.
YD/T 1369.5
-
2006

Technical Requirements for
Iub

Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Part V:
Data Transport & Tr
ansport
Signaling for C
ommon Transport Channel
D
ata
S
treams



No.
YD/T 1369.6
-
2006

Technical Requirements for
Iub

Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Part VI: User Plane Protocol for C
ommon
Transport Channel
D
ata
S
treams



No.
YD/T

1369.7
-
2006

Te
chnical Requirements for
Iub

Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Part VII: Data Transport & Transport
Signaling for DCH Data Streams



No.
YD/T 1369.8
-
2006

Technical Requirements for
Iub

Interface of 2GHz TD
-
SCDMA
Digital

Cellular Mobile Communication Network Part VIII: User Plane Protocol for DCH
Data Streams



No.
YD/T 1370
-
2006

Test Methods for
Iub

Interface of 2GHz TD
-
SCDMA Digital Cellular
Mobile Communication Network



No.
YD/T 1371.1
-
2006

Technical Requirements for Uu I
nterface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Physical Layer Technical Specification
-
1:
G
eneral Principles



No.
YD/T 1371.2
-
2006

Technical Requirements for Uu Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network

Physical Layer Technical Specification
-
2:
Physical Channels and Mapping of Transport Channels onto Physical Channels



No.
YD/T 1371.3
-
2006

Technical Requirements for Uu Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Physical Layer

Technical Specification
-
3:
Multiplex and Channel Coding



No.
YD/T 1371.4
-
2006

Technical Requirements for Uu Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Physical Layer Technical Specification
-
4:
Spread Spectrum and Modulation



No.
YD/T 1371.5
-
2006

Technical Requirements for Uu Interface of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Physical Layer Technical Specification
-
4:
Physical Layer Procedures



No.
YD/T 1371.6
-
2006

Technical Requirements for Uu Interface of

2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Physical Layer Technical Specification
-
4:
Physical Layer
Measurements



No.
YD/T 1372.1
-
2006

Technical Requirements for Uu Interface L2 of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Networ
k Part 1: MAC



No.
YD/T 1372.2
-
2006

Technical Requirements for Uu Interface L2 of 2GHz TD
-
SCDMA
Digital Cellular Mobile Communication Network Part 2: RLC



No.
YD/T 1373
-
2006

Technical Requirements for Uu Interface RRC of 2GHz TD
-
SCDMA
Digital Cellular Mobile

Communication Network


The following industry

standards
are being drafted:




Technical Requirements for UICC
-
Term
inal (Cu) Interface

of 2GHz TD
-
SCDMA/WCDMA
Digital Cellular Mobile Communication Network



Test Methods for UICC
-
Term
inal (Cu) Interface

of 2GHz

TD
-
SCDMA/WCDMA Digital
Cellular Mobile Communication Network


The draft project of
TD
-
SCDMA
V
2
HSDPA

standard was started in August 2005 and is
expected
to be completed
by August 2006. CCSA is considering
the
develop
ment of test system in
compliance
with
the

TD
-
SCDMA
standard
.


I
.

Rational for

TD
-
SCDMA Evolution

T
he direction of
WCDMA

and
CDMA2000

evolution appears to be evident
.

TD
-
SCDMA will
soon be put into commercial use, and will inevitably

develop toward higher rate transmission
technology.
It is
an urgent task for us to research and develop the enhanced technology
standards
and

evolution
. The rapid development of 3G market
s

last year
accelerated

the evolution pace of
WCDMA and CDMA2000. HSDPA, regarded as “E3G”
,

was commercialized at

the end of 20
05.
China Mobile

would go to

HSDPA

directly if it
were

deploying 3G network
.

TD
-
SCDMA

faces
the challenge from HSDPA. The

s
ustainab
ility of TD
-
SCDMA

has become an important factor for
the
operators (especially the

new entrants
) when they

choose among the s
tandards to deploy their
3G networks. In addition, some problems related to
TD
-
SCDMA

technologies have to be settled
during evolution, like those concerning coverage, high
-
speed mo
bility
, and interference among
UE
s

and base stations.


Issue of coverage:
The coverage radius of
TD
-
SCDMA

system rests mainly with two factors: one
is emission level and Rx sensitivity
,

the other is up/downlink guard time slot length. As for the
emission level and Rx sensitivity of the system, compared with
FDD
, the requirement
of
TD
-
SCDMA

for Rx sensitivity is much lower thanks to the new technologies like S
mart
A
ntenna
.
However, due to the duplex mode of TDD, guard time slot is required between up
links

and
downlinks to guarantee non
-
interference between up and downlink synchron
ous time slots.
Therefore, the coverage radius of
TD
-
SCDMA

system is restricted by the guard interval length
between up
link

and downlink synchronous time slots. Theoretically, the maximum coverage it
supports is approximately
11.25

km. Larger cell radius w
ill cost certain system capacity.


Issue of high
-
speed mo
bility
: Currently ITU requires
a
TDD
rate of 120km/h and
that of FDD
500km/h
, because of the continuous control of FDD system and discontinuous transmission of
TDD system. Since fast fading has more

effects on TDD system,
TD
-
SCDMA

faces challenges in
supporting terminals of high mobility.


In addition, there are several requirements for TDD long
-
term evolution:



Enhanced services: to achieve lower latency, high

data
-
rate

in real sense
, like peak ra
te
of 100Mbps for downlink and 50Mbps for uplink (
the
bandwidth
of
20MHz), better
mobility, lower costs, higher spectrum efficiency

and capacity
, larger coverage, and
lower terminal complexity and costs;




Flexible spectrum and reconfigurable bandwidth: Ban
dwidth can be configured
based
on traffic

requirement, from 1.25 MHz at least to 20 MHz;



Reach of

all 3G environment
s
: including wide
-
area

coverage,
such as

downtown,
suburb
an

and rural areas
;

indoor and outdoor
environment

and low and high
-
speed
mo
bility
environment

as well;



Distributed networking structure and smooth system layout;



Requirements for terminals: low cost, low power consumption, and multi
-
antenna;



The
evolution
path of
TD
-
SCDMA
is

staged as such
, namely single
-
carrier HSDPA/HSUPA,
multi
-
carrier TD
-
SCDMA and LTE TDD.



Figure 2 TD
-
SCDMA Enhanced and Evolution Scenarios


II TD
-
SCDMA HSDPA/HSUPA Enhanced

The

enhanced technology of TD
-
SCDMA not only improve
s

the data
-
rate, but lower
the

operation

cost
s

f
or

each users

due to better

spectrum

efficiency and expand network coverage and capacity.
M
eanwhile
it
guarantee
s

the backward compatibility of the system. Undoubtedly, all th
ese features

are
extremely essential

that operators
have to consider

when
looking at

the performance
-
price
ratio f
or

3G network
deployment
. 3GPP introduces two important enhanced technologies in R5
and R6 respectively, namely HSDPA and HSUPA.


HSDPA

is applicable to both FDD and TDD

system with

much

similar
ity in the way of
deployment.

T
he basic bottom
-
layer
key technol
ogies
used

includ
e

AMC

(Adaptive Modulation
and
Enc
oding),
HARQ

(Hybrid Automatic Repeat Request), fast scheduling algorithm

and
etc.
The theoretical peak rate can reach
2.8Mbps

when the ratio of up
stream

and down
stream

time
slots of
TD
-
SCDMA

single
-
carrie
r (
1.6MHz
)
HSDPA

is 1:5.


The integration of
HSDPA

and multi
-
carrier (i.e. multi
-
carrier
HSDPA
)
, that is to use
multi
-
carrier
technology and high
-
order modulation, can
notably increase

the
peak rate and spectrum efficiency
of
HSDPA

and then further
promot
e the capability of

TD
-
SCDMA

in its support
of

high
-
rate

data
services. For instance, the theoretical peak data rate of
a
three
-
carrier

TD
-
SCDMA

architecture

u
sing 16QAM

is up to

8.4Mbps
. Furthermore, in the multi
-
carrier
HSDPA

solution,
TS0

on

the
complem
entary carrier can also be used
to transmit
data, and the peak rate may be further
increased
.
A
quantitative analysis
indicates
that t
hree
-
carrier
HSDPA

can support
a

peak rate up to
10Mbps

if

data transmi
tted

over
TS0 on the
complementary carrier.


Multi
-
carrier
HSDPA

is a feasible solution
to address effectively the
high
-
capacity
and
high
-
speed
transmission,
while

ensuring

the
maximum backward compatibility with the
legacy

TD
-
SCDMA

network. Currently, two mature technologies

higher order modulation and m
ore efficient
scheduling

algorithm

become the

most possible choices. When
the environment is deemed
appropriate
, the high
-
order modulation of
64QAM

may be adopted.
T
heoretically,
64QAM

can
improve
performance

by

a factor of

1.5 compared with

the

current
16
QAM
, with single
-
carrier
peak rate reaching
4.2Mbps

and
three
-
carrier peak rate up to
12.6Mbps
.


Based on the

simulation results,
a remarkable

performance gain can only be
acquired

when
the
s
ignal to noise ratio

is above
25dB

if
64QAM

is used
in

HSDPA
.
T
he
refore,
64QAM

mainly

work
s

in
the environment of adequate

channel conditions, low
-
speed mobility

or static status.
I
n
addition,
a
good scheduling algorithm

may well

enhanc
e

the
strength

inherent to

the
multi
-
carrier
HSDPA

technology.
C
urrently, the most fr
equently used scheduling algorithms include Max C/I,
polling scheduling, and proportional fair scheduling.
The research of
fast scheduling algorithm is
going deeper

and

m
any algorithms taking into account
of
both maxi
mum

throughput and fairness
have been p
ut forward, such as feedback
-
control scheduling algorithm
deriv
ed from
the improved
proportional fair scheduling, rate
-
restricted Max
C/I

algorithm and etc. A good scheduling
algorithm not only has to guarantee a desirable data throughput, but also takes i
nto account the
restriction of fairness. The larger the throughput is, the higher the
performance

ratio will be

for a
carrier
. However, the satisfaction
degree
will be
damaged

if customers have no access to the
service
s

for a long time
.
A
good scheduling a
lgorithm should take into account the priority

level
of
the
services
that
different customers
need to transmit
. Those of higher
priority level

should
be sent
earlier than

others
that are
not
so
sensitive to latency. Scheduling algorithm must be integrated
with
HSDPA

channel features so as to optimizing
HSDPA

performance
giving a full play to the
unique characteristics of

HSDPA

transmission.


When

CCSA formulates
TD
-
SCDMA

multi
-
carrier
HSDPA

specifications
, it bears in mind the
goal
to achieve
single
-
user

peak rate N times that of
3GPP HSDPA

through carrier bundling and
minimized adaptation,

based on the industrial standards for
1
st

Edition

of
N frequency and
3GPP
R5 HSDPA

specifications, so as to better support packet services and meet the demands of
oper
ators for high
-
speed packet data services. The basic principle for formulating
TD
-
SCDMA

multi
-
carrier
HSDPA

specifications: compatible with the industr
ial

standards for
TD
-
SCDMA

1st
Edition
of N

frequency

in air interface
, and
also

compatible with
3GPP R5
HSDPA

standards.


L
ittle alteration has been made to
HSDPA

in
TD
-
SCDMA
, except for a new media access control
sub
-
layer (
MAC
-
hs
) added to Node B for high
-
speed data transmission control, and
newly

added
definitions of several new transmission channels an
d physical channels for forward comp
atibility.
I
t is easy for
TD
-
SCDMA

network to acquire the functions of
HSDPA

by
equipments

upgrading
and
replacement
.
The reason is that

many physical layer technologies of
TD
-
SCDMA

are
brought
to bear

via software radio
,
so
it is the
strength inherent to

TD
-
SCDMA architecture

to adopt
HSDPA

physical layer technologies through upgrad
ing software
,
rendering the
hardware
replacement
unnecessary
.

As up to now we have

n
o
t see
n

any TD
-
SCDMA

network

of large scale deployed, th
ere is no
track record

regarding how to build such a network
has been proved.
A
ccording to the
characteristics of
TD
-
SCDMA
, there are two possible solutions in the initial stage of network
deployment, namely, cell
-
shared deployment between
HSDPA

and
TD
-
SCD
MA
, and non
cell
-
shared deployment in separate layers.




Cell
-
sharing between

HSDPA

and
TD
-
SCDMA

can be done through separate carrier
frequency or common carrier frequency mode. The two systems share the resources like Node B
power, carrier frequency, time
slot and channelization code (CC) and give a play to their
respective strengths under the unified control.



The non cell
-
shared deployment between
HSDPA

and
TD
-
SCDMA
, where HSDPA alone
forms a separate layer of the network architecture.
TD
-
SCDMA

network pr
ovides CS and
low
-
speed R4 data services, while
HSDPA

network mainly provides high
-
speed data services.
T
he
two systems will be complementary to each other in service bearing capability by a handover.

Now it is a fruit
-
yielding time for many companies invo
lved into the R&D of TD
-
SCDMA
enhance. Datang and TD Tech are engaged in the research on
HSUPA

(uplink enhanced
technology) based on
3GPP

R6 and
R7
, and on MBMS (multimedia broadcasting/multicast). In
October 2005, Datang Mobile launched, for the first tim
e, TD
-
SCDMA HSDPA equipment, with
the single
-
carrier data rate in air interface reaching 2
.
8 Mbit/s, and demonstrated some typical 3G
services, like VoD and high
-
speed FTP downloading. It is expected that Datang will be the first to
make TD
-
SCDMA

HSDPA sys
tem available for commercial use in mid 2006.


Figure 3 TD
-
SCDMA Evolution of Datang Mobile


III TD
-
SCDMA LTE Solution

In recent years, along with the rapid development of traditional cellular mobile communication
technologies, some broadband wireless

access technologies (e.g. mobile
WiMAX
-
802.16e
) have
taken to provide part of mobility, trying to seize a portion of mobile market share. In this context,
a new market demand arises from the mobile communication industry, which is to further improve
3G te
chnologies to provide a stronger data service capacity, so as to serve users better and
compete with other technologies. Accordingly,
3GPP

and
3GPP2

initiate the research on
LTE

Long Term Evolution

with a view of keeping the competitive edge and the domina
nce of 3G
technologies in the market of mobile communications. 3GPP kicked off the LTE program in
November 2004, and later LTE Demand Report was approved on 3GPP Conference in June 2005,
where the rese
arch on StudyItem is scheduled to be complete in mid 20
06 and a standard frozen in
mid 2007, waiting its commercial use in 2009 as expected.

All the indexes required to be met as specified by LTE program are as follow:



Support the broadband of 1.25MHz
-
20MHz, like 1.25MHz, 1.6MHz, 5MHz, 10MHz, and
20MHz;



Peak
data rate: 50Mbps for uplink, 100Mbps for downlink;



Support future enhanced IMS and core network;



Support symmetrical and asymmetrical spectrum allocation;



Packet Service is the main objective;



Lower latency of wireless network: U
-
plan < 10 ms, C
-
plan
< 100ms;



Spectrum efficiency up to 2
-
4 times that of 3GPP Release 6: 5 bps/Hz for downlink ( 3
-
4
times that of Release 6 HSDPA), 2.5 bps/Hz for uplink (2
-
3 times that of Release 6 HSUPA);



Emphasizing backward compatibility, while taking into account of t
he system performance;



Improvement of throughput at the edge of cell;



Lower costs (estimated to resemble WiMAX);

LTE program of China is undertaken by E3G Technology Group, including ZET, Huawei, Datang
and the 5th Working Group of 863 Future (including B
eijing University of Post and
Telecommunications (BPTU), Tsinghua University, Southeast University, RITT, and Shanghai
Research Center for Wireless Communications). BPTU takes charge of TDD evolution research,
and the Research Institute of Communication St
andards (former RITT) of China Academy of
Telecommunication Research (CATR) acts as a coordinator.



3GPP LTE

technical solution is still divided into FDD and TDD scenarios. Comparatively
speaking, TDD allows flexible spectrum allocation, while FDD require
s not only paired spectrum,
but sufficient duplex intervals. LTE requires even larger bandwidth, however it has become more
and more difficult for operators to obtain broadband paired spectrum that meets the requirement. It
is more likely that spectrum sui
table for broadband wireless communication is not in pair. In fact
only unpaired spectrum can be applied in some circumstances. TDD provides the most possible
and even the only candidate solution for unpaired spectrum.


In addition, TDD supports flexible
asymmetrical services, such as changing the proportion of
uplink and downlink in a frame. Many new services are asymmetrical, for which TDD is the most
feasible one. TDD has another advantage that the symmetrical channels can improve system
performance sub
stantially. This advantage can be leveraged in many leading
-
edge technologies to
increase spectrum or power efficiency, such as link adaptation (LA), multi
-
input
-
multi
-
output
(MIMO), pre
-
equalization and etc. With symmetrical channels, TDD also boasts the
following
features: it can minimize latency of the system with open
-
loop adaptation and control; signaling
and control information can be simplified to a large extent; and the implementation of some
advanced technologies (e.g.
MIMO
) can also be simplified.



The long
-
term evolution (LTE) of TD
-
SCDMA standard has commenced. The two TD
-
SCDMA
Standard LTE Solutions that China submitted to
3GPP

namely Multi
-
carrier TD
-
SCDMA
(
MC
-
TDSCDMA) and TDD
-
based
OFDM

(
TDD
-
OFDM
)

have been accepted. Key parameters
of these

two alternatives have been defined primarily, with relevant performance simulation been
carried out.


As a release featuring compatibility and smooth evolution, multi
-
carrier TD
-
SCDMA solution
helps existing TD
-
SCDMA system improve performance; as a br
and new release stressing
performance improvement, TDD
-
OFDM solution aims toward a longer
-
term evolution.


Multi
-
carrier TD
-
SCDMA could incorporate with HSDPA technology to achieve a multi
-
carrier
coverage in the same sector/cell, an important method for

TD
-
SCDMA system to expand its
capacity. And system gains will be acquired by organizing these frequencies into a cell. It is a
feasible way to improve the throughput for a single user that UE simultaneously transmits and
receives data using multiple carri
er resources. The combination of multi
-
carrier and HSDPA will
further increase the downlink throughput. Supposing the same spectrum efficiency, its theoretical
peak rate is on a par with that of WCDMA.


OFDM is among the multi
-
carrier modulation technolog
ies and can improve its peak rate with
high spectrum efficiency. Since each link can be modulated separately, this system allows multiple
hybrid modulation modes easily on both uplink and downlink at the same time.


There is another problem concerning the

integration of FDD and TDD: TDD shall be designed to
give a play to the advantages and features of itself, and at the same time remain consistent with
FDD in the perspective

of basic technology. The evolution of (TDD LCR) TD
-
SCDMA requires
the coherence w
ith the legacy to a certain extent. It can be deeply converged with FDD on MAC
layer, but hardly be consistent with it completely on the physical layer due to the inherent
discrepancies between them.