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LTE Basics and Key Technologies
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Part I LTE Basics
Frame Structure & Physical Resource
Physical Channel and Signal
Part II LTE Key Technologies
Part I LTE Basics
Frame Structure & Physical Resource
Physical Channel and Signal
Part II LTE Key Technologies
Outline
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Evolutionary Process Evolutionary Path o !ireless Technology
LTE becomes the trend of mobile communication technology evolution, during which, multiple
technologies will coexist for a long period of time before they evolve into one single network.
"
#$ #%$ #%'$ "$ "%$ "%'$ "%($
$PRS E)$E eE)$E
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R
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R-
.$
C)/+ #000
12 E34)5
60#%1- e 60#%1- m
*S)P+
*SP+7
R' F))8
T))
.$
$S/
T)4
SC)/+
!C)/+
R((
60#%1- d
C)/+
IS(
C)/+
#000 19
LTE
E34)5
Rev% +
E34)5
Rev% B
*S,P+
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Type1 frame structure Each1! ms radio frame is divided into "! timeslots or 1! subfra
mes.
Each subframe has " timeslots, !.# ms for each timeslot.
The $L and %L transport is conducted at different fre&uencies.
LTE Radio Frame Structure
LTE supports two types of radio frame structures Type 1, applicable to '%%(Type ", applicable to T%%.
Frame Structure Ty:e1 4 F))
.
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LTE Radio Frame Structure
Frame structure Ty:e#
; T))
Type" frame structure
Each 1! ms wireless frame is divided into two half frameswith the duration of # ms each.
Each half frame is composed of ) timeslots with the duration
of !.# ms and * special +ones %wT-, , $pT-.
The total duration of %wT-, and $pT- is 1 ms, while
the duration of %wT- or $pT- is configurable.
Further
analysis
On the fre&uency domain, the subcarrier interval is 1#/0+. 'or instance, there are 1"!!
subcarriers in the case of "!0+ system bandwidth. On the time domain, each 1ms subframe is divided into several symbols, and there are
guard interval 2 between symbols( there are 13 symbols in 1 ms for regular 2 and 1"
symbols in 1ms for extended 2.
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,:liner
0 1 # " . - ' 6 (
! # ms % - $ $ $ % - $ $ $
1 # ms % - $ $ % % - $ $ %
" # ms % - $ % % % - $ % %
* 1! ms % - $ $ $ % % % % %
3 1! ms % - $ $ % % % % % %
# 1! ms % - $ % % % % % % %
4 1! ms % - $ $ $ % - $ $ %
Coniguration?ormal cyclic :rei9 E9tended cyclic :rei9
)=PTS $P ,:PTS )=PTS $P ,:PTS
! * 1!
1 O'%symbols
* )
1 O'%symbols
1 5 3 ) *
" 1! * 5 "
* 11 " 1! 1
3 1" 1 * 6
" O'%symbols
# * 5
" O'%symbols
) "
4 5 * 5 1
6 1! " 7 7 7
) 11 1 7 7 7
,:lin
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LTE Physical Resource +llocation 4 RE8RB
DLsymbN OFDM symbols
One downlink slot slotT
0=l 1DLsymb = Nl
subcarriers
subcarriers
RBsc
DLsymb NN
Resource block
resource elements
Resource element ),( lk
0=k
1RBscDLRB = NNk
-ubcarrierinterval
2 duration9umber ofsubcarriers
9umber ofsymbols
9umber of:Es
1# /0+
:egular 2 1" 6 )3
Extended2
1" 4 6"
:E ;:esource Element< is the minimum
resource unit( for each antenna port, it indicates
one O'% symbol on the time domain and one
subcarrier on the fre&uency domain.
:= ;:esource =lock< is the resource unit of
service channel resource allocation.
'
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LTE Physical Resource +llocation 4 RE8RB )iagram
6
subcarriers, 1)!k0+
symbols
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)o=nlin< su>rame ?um>er o 5F)/ sym>ols incontrol area
S:ecial su>ram 1@ #
$eneral Su>rame 1@ #@ "
LTE Physical Resource +llocation Control +rea and
)ata +rea
1. %ownlink subframe -ignals in the control area and in the data
area are distinguished by time, and the number of O'% symbols
in the control area can be allocated.
:egular subframe The regular subframe is composed of
two timeslots, including downlink and uplink regular
subframe.
-pecial subframe The special subframe is composed of
three special +ones, namely, %wT-, and $pT-.
". -ignals in the control area and in the data area in the uplink regular
subframeare distinguished by fre&uency.
(
2ontrol area %ata area
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Part I LTE Basics
Frame Structure & Physical Resource
Physical Channel and Signal
Part II LTE Key Technologies
Part I LTE Basics
Frame Structure & Physical Resource
Physical Channel and Signal
Part II LTE Key Technologies
Outline
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2hannel type 'unctions
$-20 ;hysical $plink -hared 2hannel< 2arrying uplink service data
$220 ;hysical $plink 2ontrol 2hannel< 2arrying 0>:? information
:>20 ;hysical :andom >ccess 2hannel< -ending preamble information for random access of the$E
2hannel type 'unctions
%-20 ;hysical %ownlink -hared 2hannel < 2arrying downlink service data
=20 ;hysical =roadcast 2hannel< 2arrying broadcasting information
2'@20 ;hysical 2ontrol 'ormat @ndicator 2hannel< @ndicating the number of symbols occupiedby %220 in the same subframe
%220 ;hysical %ownlink 2ontrol 2hannel< 2arrying the downlink scheduling information
0@20 ;hysical 0ybrid >:? @ndicator 2hannel< 2arrying 0>:? information
,:lin< :hysical channel
)o=nlin< :hysical channel
LTE Physical Channel
11
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LTE Physical Channel RE /a::ing o )o=nlin< Physical Channel
%-20 and =20 are mapped onto the data field of subframe.
%-20 and =20 can exist in the same subframe.
1#
O'% symbols
*4 sub7carriers
*4 sub7carriers
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reambleformat
%uration
-e&uence length
! 1ms )*5
1 "ms
)*5
" "ms )*5 ;transmitted
twicedaptive odulationmode
>daptive 2odingefficiency
/a2 more efficient and flexible.
#(
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*y>rid +utomatic Re:eat Reuest *+RD com>ines For=ard Error Correction FECD
and +utomatic Re:eat Reuest +RD% *+R@ =orle an
d accurate rate adGustment the LTE :rocess% FECsends an error correction code from transmitters to correct errors at receivers. +Rsend >2/ or 9>2/ message to feedback the decoding results
*+R
"0
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Fast Scheduling is $rou:ing Scheduling% The >asic aim is to serve ast%
Fast Scheduling
"1
Time4>ased round4ro>in
Flo=4>ased round4ro>in
/a9 C8I
PF Pro:ortional FairD
Each user@ served in order@ gets the same
allocated time in average% 5=ing to dierent
environments o users@ their lo=s dier%
)es:ite the environment dierence@ every user
is ensured to get the same lo= in a certain
order%
The system gives higher :riority to the users
=ho are served at the ma9 C8I%
The system can get the ma9imum Through:ut%
)o not air or users%
This method integrates the scheduling modes
a>ove@ considers the satisaction o most
users@ and ensures a relative high through:ut%
It is a :ractical scheduling mode%
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