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Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
The UMTS radiomobile system
Maria Stella Iacobucci
2 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
I’m grateful to TELECOMITALIA colleagues for havingprovided some of the slides of this presentation
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UMTS OVERVIEW Maria Stella Iacobucci
Divertissement
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UMTS OVERVIEW Maria Stella Iacobucci
Timeline
Standardization aspects
UTRAN: UMTS Terrestrial Radio Access Network
The Code Division Multiple Access
Handover
UMTS Radio Interface
Logical, Physical and Transport Channels
An Introduction to UMTS Radio Protocols
An Introduction to Radio Access Bearers Physical Level Procedures
UMTS Security
The UMTS Evolution: HSDPA
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UMTS OVERVIEW Maria Stella Iacobucci
Standardization Aspects
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UMTS OVERVIEW Maria Stella Iacobucci
“UMTS will be a mobile communications system that can offer
significant user benefits including high-quality wireless multimedia
services to a convergent network of fixed, cellular and satellite
components.
It will deliver information directly to users and provide them with
access to new and innovative services and applications.
It will offer mobile personalised communications to the mass market
regardless of location, network and terminal used”.
UMTS Forum 1997
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UMTS OVERVIEW Maria Stella Iacobucci
UMTS/IMT-2000 systems had to be truly innovative interms of performances and offered services
UMTS/IMT-2000 GOALS
Reflections on radio access and networks choices
8 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Standardization bodies
In 1995, ETSI starts the activity on 3G systemsIn January 1998, the radio interface was :
W-CDMA in the “paired bands” (FDD Mode)
TD-CDMA in the “unpaired bands” (TDD Mode)
In Decemberer 1998, the standardization bodies of Europe, Japan, Koreaand USA create the 3GPP (3rd Generation Partnership Project); later even thechinese CWTS reached the 3GPP
Inside the ITU, the 3G system is called IMT-2000; IMT-2000 includes MC-CDMA, EDGE and UMTS.
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UMTS OVERVIEW Maria Stella Iacobucci
3G Variants
PDC Advanced GSMNSS and packetcore
WCDMA 3G (Japan)
GSM 900/1800 Advanced GSMNSS and packetcore
WCDMA, GSM,EDGE
3G (Europe)
IS-95,GSM1900,TDMA
IS-41WCDMA, EDGE,WCDMA2000
3G (US)
2G basisSwitchingRadio Access
Variant
10 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
UMTS Frequency Allocation
The CEPT/ERC recommendation n° 07/1997 allocates to
terrestrial UMTS the bandwidths of 1900-1980 MHz, 2010-
2025 MHz and 2110-2170 MHz
Inside the ERC recommendation n° 25/1999, the usage of
each band is specified as follows:• FDD bandwidths: 1920-1980 MHz e 2110-2170 MHz
• TDD bandwidths: 1900-1920 MHz e 2010-2025 MHz
An “unlicensed” bandwidth for “Self provided applicationsoperating in a self-coordinating mode in shared spectrum” is
2010-2020 MHz
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UMTS OVERVIEW Maria Stella Iacobucci
1900 1980 2010 2025 2110 2170 22001920
T
D D
F
D D
S A T
F
D D
S A T
T
D D
UMTS bandwidths: European Situation
215 MHz assigned
• 155 MHz terrestrial component:
• FDD 60 + 60 MHz
• TDD 35 MHz
• 60 MHz satellite component
T D D
T D D (private usage)
FDD
SAT
12 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
The migration towards UMTS
GSMGSM
HSCSDHSCSD
GPRSGPRS
EDGEEDGE
UMTSUMTS
NONO
UMTSUMTS
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UMTS OVERVIEW Maria Stella Iacobucci
UMTS: general aspects
Iu
UTRAN
UE
Uu
UTRAN UMTS Terrestrial Radio
Access Network
CN Core Network
UE User Equipemet
CN
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UMTS OVERVIEW Maria Stella Iacobucci
UTRAN Architecture
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UMTS OVERVIEW Maria Stella Iacobucci
UTRAN: UMTS Terrestrial Radio Access Network
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UMTS OVERVIEW Maria Stella Iacobucci
Network Elements are grouped in:
• UTRAN, that controls radio interface functionalities
• Core Network (CN), that routes the traffic
• User Equipment (UE) is divided in:
• Mobile Equipment (ME), which principal functions are:
• UMTS Subscriber Identity Module, a smartcard that
•Contains the user identity and a copy of the service profile
•Stores the authentication algorithms, authentication and
encryption keys
UTRAN elements: User Equipment
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UMTS OVERVIEW Maria Stella Iacobucci
UTRAN elements: Node B
Node B (Radio Base Station) groups one or more Base Transceiver
Stations and plays the following functions:
• Radio Interface Processing (channel coding, interleaving,
spreading, mo-demodulation, transmission and reception)
• downlink parameters measurements (BER, received power) and
transmission to the node B
• Execution of access, authentication, hand-over procedures
18 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
UTRAN elements: RNC
Radio Network Controller (RNC) principal functionalities are:
• Node B Radio Resource Control
• Codes allocation and radio link setup
•Packet scheduling and retransmission
•Admission Control and congestion monitoring
•Signalling and user data processing
•Handover decision
•Outer loop power control
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19 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
UTRAN elements: Iub, Iur and Iu interfaces
• Iub is a proprietary interface and connects a node B to
an RNC
• Iur has special functions fo handover and macro-
diversity; is a standard interface
•Iu, which connects the RNC with the Core Network is an
“open multivendor” interface
•The protocols on such interfaces are ATM based
Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Code Division Multiple Access
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UMTS OVERVIEW Maria Stella Iacobucci
Radio Access Techniques
P Power
T TimeF Frequency
PP
TT
PP
TT
FF
PP
TT
FF
FDMA (TACS)FDMA (TACS)
TDMA (GSM, DECT)TDMA (GSM, DECT)
CDMA (UMTS)CDMA (UMTS)
FF
TDMA/CDMA (UMTS)TDMA/CDMA (UMTS)
22 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Code Division Multiple Access
The separation among different users that share the same radio resourceis based on the use of orthogonal codes
It is not a slotted access technique!
Three variants:
Direct Sequence (DS): is based on the direct modulation of datasthrough a given code sequence
Frequency Hopping (FH): is based on hops of the carrier which follows a
given hop sequence Time Hopping (TH): is based on hops of the pulses in time following a
given time hopping sequence
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UMTS OVERVIEW Maria Stella Iacobucci
A beautiful mind
Two pages from Lamarr and Antheil patent, 1942
24 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
The actress and composer invention
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25 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Code division multiple access
Λαλοι συ την
Ηλλενικην
γλωσσαν?
Esta es la tierra
nadàl de mi
hermano
Sagunto...
Je suis Ivorien…
est-ce que voi
connaissez mon
pays?
Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
frequency
code
time
DS-CDMADirect Sequence - Code Division Multiple Access
Wide spectral occupation
Complex receiver to recover the information
Stringent power control
No frequency planning (reuse factor = 1)
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UMTS OVERVIEW Maria Stella Iacobucci
Spreading and despreadingNarrowband interfering signal
f
f
f
f
f
S(f)
Information signal of Bnbandwidth
Information signal of expanded
bandwidth Bw
expanded information signalplus narrowband interferingsignal at the receiver input
Signals after the despreading
Signals at the receiver output
28 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Spreading and despreadingBroadband interfering signal
f
f
f
f
f
S(f)
Information signal of Bnbandwidth
Information signal of expanded
bandwidth Bw
expanded information signalplus broadband interferingsignal at the receiver input
Signals after the despreading
Signals at the receiver output
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29 UMTS OVERVIEW Maria Stella Iacobucci
Chip sequence
t
t
t
Informationsequence
Transmittedsequence
x
Single Transmission
b(t)
x(t)b(t)c(t)
c(t)
x(t)
30 UMTS OVERVIEW Maria Stella Iacobucci
Chip sequence
t
Receivedsequence
Decodedsequence
Single Reception
t
b(t)
c(t)c(t)x b(t)z(t)
c(t)
t
z(t)=x(t)
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UMTS OVERVIEW Maria Stella Iacobucci
Orthogonal Sequences
t
c1(t)
Chip sequence1
c1(t) ·c2(t)
t
c2(t)
Chip sequence2
t∑
chip N
chip N 1
1 = 0
Nchip=8
32 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
t
Multiple transmission
c1(t)
x1(t)
tb1(t)
t
x2(t)
tb2 (t)
c2(t)
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UMTS OVERVIEW Maria Stella Iacobucci
Multiple Access
t
x1(t)+x2(t)
x1(t)x2(t)
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UMTS OVERVIEW Maria Stella Iacobucci
Multiple reception
t
z(t)=x1(t)+x2(t)
t
c1(t)
z(t) ·c1(t)
t
b1(t)
t
∑chip
N
chip N 1
1
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UMTS OVERVIEW Maria Stella Iacobucci
In formulas
[ ] [ ]
[ ] [ ]
[ ] [ ]
[ ] [ ]
[ ] [ ] )()()()()()()(
)()()()()()()()(
)()()()()()()(
)()()()()()()()(
Decoding
)()()(
AccessMultiple
)()()(
)()()(
Coding
0)()(;1)()(
Property
2222211
2222112
1122111
1221111
21
222
111
21
t xt ct c E t xt ct c E t x
t ct ct xt ct ct x E t ct z E
t xt ct c E t xt ct c E t x
t ct ct xt ct ct x E t ct z E
t xt xt z
t ct bt x
t ct bt x
t ct c E t ct c E
bb
bb
bb
bb
bb
T T
T T
T T
T T
T T ii
=⋅⋅+⋅⋅=
=⋅⋅+⋅⋅=⋅
=⋅⋅+⋅⋅=
=⋅⋅+⋅⋅=⋅
+=
⋅=
⋅=
=⋅=⋅
36 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Spreading Sequences
The more used families for spreading sequences are:
• pseudo noise sequences, PN, with pseudo-noise caracteristics but notperfectly orhtogonality
• In UMTS Gold and Kasami codes are used, with good cross-correlation properties
• In UMTS are used for scrambling codes
• Perfect orthogonal sequences, with no good spectral and cross-correlationproperties, but with perfect orthogonality
• In UMTS are used for spreading codes
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UMTS OVERVIEW Maria Stella Iacobucci
Spreading codes
SF = 1 SF = 2 SF = 4
C2,1 = (1,1)
C2,2 = (1,-1)
C1,1 = (1)
C4,1 = (1,1,1,1)
C4,2 = (1,1,-1,-1)
C4,3 = (1,-1,1,-1)
C4,4 = (1,-1,-1,1)
38 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Spreading and Scrambling
In UMTS, a code assigned to a user is given by the product of a scramblingand a spreading code
Uplink Scrambling codes distinguish different users
Spreading codes distinguish different communications associated to the sameuser
Separation of data and control channels
No code planning: in uplink there are millions of available codes
Downlink Scrambling codes distinguish different cells
The number of downlink scrambling codes is 512
Spreading codes are associated to different users into the same cell
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UMTS OVERVIEW Maria Stella Iacobucci
Spreading and scrambling codes
No, do not increases the
bandwidth
Yes, increases the
bandwidthSpreading
Downlink: 512 codes of 10ms: Gold Codes
OVSFCode family
Downlink: 10ms=38400chips
Uplink: millions
Number of codes related toa scrambling code =spreading factor
Number of codes
Uplink: (1)10ms=38400chips o (2) 66.7µs=256chips
4-256 chips (1.0-66.7µs)for the downlink even 512chips
length
Scrambling codeSpreading code
40 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Principles of Wideband CDMA transmission
Spreading with a code of 256 chip (SF=256)
Spreading with a code of 256 chip
(SF=256)
Spreading with a code of
4 chip (SF=4)
38400 chip ogni 10 ms
38400 chip ogni 10 ms
38400 chip ogni 10 ms
Voice source
(8-13 kbit/s)
Packet data: WEB
Browsing and
streaming
(64-144 kbit/s)
High Speed data: videoconference,
videotelephony
(≥ 384 kbit/s)
80 bit
640 bit
3840 bit
Error
correction
coding
Error
correctioncoding
Error
correctioncoding
150 bit
2400 bit
9600 bit
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UMTS OVERVIEW Maria Stella Iacobucci
Example: data at 64 kbit/s
64+3,4=67,4 kbit/s
202 kbit/s
240 kbit/s
3,84 Mchip/s
User bit rate + associate signalling
Signal in input at the RF modulator
Convolutional codingRate = 1/3
Rate matching (Bit Stuffing)
Moltilication for the OVSF code of
length (Spreading Factor) = 16
42 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Multimedia in UMTS
38400 chip in 10 ms
(80 voice bits + coding)
38400 chip in 10 ms
(640 data bits + coding)
38400 chip in 10 ms
(3840 bit High Speed + cod.)
The input signals
are distinguished by
codes of different
length
3,840 Mchip/s
Multiple
Access
MultipleAccess
MultipleAccess
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UMTS OVERVIEW Maria Stella Iacobucci
CDMA Transmission and reception
DATA
0 f 0 0
BACKGROUNDNOISE
f 0
EXTERNALINTERFERENCE
f 0
OTHER CELL
INTERFERENCE
f 0
OTHER USER
INTERFERENCE
f 0
ENCODING &INTERLEAVINGDATA
CARRIER
PN SOURCE
CARRIER
DIGITALFILTER
PN SOURCE
CORRELATOR
DEINTERLEAVING& DECODING
DATA
WIDEBAND
SPECTRUM
f 0
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UMTS OVERVIEW Maria Stella Iacobucci
Propagation channel
The chip duration at 3.84 Mchip/s is 0.26 µs
The delay profile varies, in urban environment, from 1 to 2 µs, even if inhilly zones delays of 20 µs have been observed
If the multipath components do not overlap, the CDMA receiver is ableto coherently recombine the different echoes
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UMTS OVERVIEW Maria Stella Iacobucci
Propagation channel effects
In a narrowband system the pulses are long and multipathcomponents overlap
f
t t
τ2τ3τ1
τ1
τ2
τ3
46 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Propagation channel effects
In a broadband system the pulses are shortand multipath components do not overlap.
Because of that, they can be recombined.
f
tt
τ2τ3τ1
τ1
τ2
τ3
τ0
τ0 −τ1
τ0 −τ2
τ0 −τ3
+
t
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Spreadingcodes
Σ
Channelestimation
Receiver
Phaserecovery
Rake Receiver
Matchedfilter
Channelestimation
Phaserecovery
∆τ1
∆τnDespreading
Despreading
*baseband
To thedecodingcircuit
Identifies the
correlation
peack and
distributes the
timing
Radio channel
estimationthrough a pilot
sequence
Propagation
delay
compensation
Somma le
componenti
riallineate (MaximalRatio Combining)
Signal S2(t)*from RF
48 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Rake receiver
Rake receiver uses many basebandcorrelators to elaborate and recombinedifferent multipath signal components
Two possible algorithms:equal-gain combining, which assigns thesame weight to each rake finger
maximal-ratio combining, which elaboratesthe finger outputs to estimate the weights thatmaximize the SNR
It is possible to show that if the n multipaths are not correlated, then
Price and Green, 1958
( ) ( )1
i
i
n S S
N N output i =
= ∑
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UMTS OVERVIEW Maria Stella Iacobucci
Capacity
For N users, the signal to interference ratio is:
( )
( ) 1 / 1
/
1
1
1
0 −=
−=
−=
−=
N
G
f P N
f P
n
E
N P N
PSNR
c
bb
0 /
1
n E
G N
b
+=
50 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Near-far problem
In general:
If the power is the same for eachsignal, then:
When the user k power is higher,then:
∑=
=+++
= N
i
i N I
C
I I I
C
I
C
1
21 ...
N
G
G
C N
C
I N
C
I
C
i
=
⋅
=⋅
=
( ) ( ) ( )
G
KC I
K N G
I G
C N
C I I N
C I C
k
k k
≡
+−=
+
⋅−
=+⋅−
=1
11
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0
5
10
15
20
25
30
35
40
45
50
55
60
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Mobile station power (W)
C a p a c i t y ( c h a n n e l s / M H z / s i t e )
ρ=0
ρ=1, 2
CDMA
ρ=0
ρ=1
ρ=2
GSM half rate (TCH/HS)
GSM full rate (TCH/FS)
ρ = power control errorstandard deviation
Power control effect on capacity
52 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Power Control algorithms
The outer Loop Power Control executes a “fine tuning” of the Inner Loop PowerControl
UE BTS RNC
OPEN LOOP POWER CONTROL
INNER LOOP (FAST) POWER CONTROL (SIR Target) 1.5 KHz
OUTER LOOP POWER CONTROL (BLER Target) 10-100 Hz
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UMTS OVERVIEW Maria Stella Iacobucci
Power Control algorithms
• The open loop power control establishes, during set-up, the mobiletransmission power from the path attenuation
• Because UMTS is an FDD system, then uplink and downlink fading processes arenot correlated and therefore the open loop power control is not able tocompensate the downlink fading
• Therefore a closed loop power control algorithm must be established betweenthe MS and the BTS, in order to determine, from the received SNR, the goodtransmission power
• The outer loop power control has the goal to adjust the SNR target value onwhich the closed loop power control is based by measuring the BLER at the RNC
54 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
“Closed Loop Power Control” gain
-2
-1
0
1
2
3
4
5
6
7
8
9
0 50 100 150 200 250 300
Mobile speed [km/h]
G a i n
E b
/ n 0
[ d B ]
Canale voce a 8kbps
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UMTS OVERVIEW Maria Stella Iacobucci
6 7 8
91011
1213141516 17
1 10 100 1000
velocità del mobile (km/h)
E b / N o [ d B ] @ B
E R = 0 . 1 % Outdoor to indoor A
Outdoor to indoor B
Vehicular A
Vehicular B
Link performances
W-CDMA: voice service (8 kbit/s) - downlink
The “outdoor to indoor” and “vehicular” (A o B) are referred to different
propagation models
56 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
1,E-06
1,E-05
1,E-04
1,E-03
1,E-02
1,E-01
1,E+00
4 4,5 5 5,5 6 6,5 7 7,5
Eb/No [dB]
B E R
it. #1
it. #2
it. #3
it. #4
it. #5
it. #6
it. #7
it. #8
TPC Hard
TPC Soft
BLER
Link PerformancesLCD data at 144 kbit/s with turbo code, function of the number of
iteration at the decoder side - Downlink (Vehicular A - 120 km/h)
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UMTS OVERVIEW Maria Stella Iacobucci
Cell breathing
C/I @ 1/N
Cell with radius R and N users
Increases the user density:
Cell with radius R and (N+X) users
(C/I)’@ 1/(N+X) < C/I
In the new situation the cell radius must be reduced
to come back to the new C/I
N
N
N+X
58 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Admission Control
During network planning, the target SIR is defined
Each UE that has an active communication consumes a part of the target SIR
The Admission Control decides if new communications can be setup without degrading the existing ones
Without varying the assigned resources
varying the assigned resources
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Handover
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Handover
GSM
SIST.
TYPE
HardHard
HandoverHandover
BEFORE DURING AFTER
DECT
SeamlessSeamless
HandoverHandover
UMTS
SoftSoft
HandoverHandover
MSC
RNC
F1
BS#1
RFP#1
CCFP
BSS#1
F2
F2
BS#2
RFP#2
BSS#2BSS#2
MSC
F1
BS#2
RNC
F1BS#1
BSS#1BSS#2
MSC
F1
BS#2
RNC
F1
BS#1
RFP#1 RFP#2
CCFP
F1
BSS#1
RFP#2
CCFP
F2
RFP#1
F1
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Soft Handover and macrodiversity
CELLA A CELLA B
CELL C
Signal margin
Soft Handover region
“ADD” threshold
Time margin
Ec/No
TIME
“DROP” threshold
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UMTS OVERVIEW Maria Stella Iacobucci
Macrodiversity
Macrodiversity consists in having more that one signal belonging to the
same connection, sent to and received from different cells
In uplink, macrodiversity can be handled:
in the node B (softer handover), where the Maximum Ratio Combining (MRC)
technique is used
In the RNC (soft handover), which makes a packet selection, that is packets from
different links carry link quality informations (i.e. C/I) and the RNC chooses each time
the best
In downlink, macrodiversity is always handled with the method of
Maximum Ratio Combining
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Spreadingcodes
Σ
Channelestimation
Receiver
Phaserecovery
Rake Receiver
Matchedfilter
Channelestimation
Phaserecovery
∆τ1
∆τnDespreading
Despreading
*baseband
To thedecodingcircuit
Identifies the
correlation
peack and
distributes the
timing
Radio channel
estimationthrough a pilot
sequence
Propagation
delay
compensation
Somma le
componenti
riallineate (MaximalRatio Combining)
Signal S2(t)*from RF
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Rake receiver in macrodiversity
In macrodiversity, the fingers must generate different codes, corresponding to different sectors
Spreadingcodes
Σ
Channelestimation
Receiver
Phaserecovery
Matchedfilter
Channelestimation
Phaserecovery
∆τ1
∆τnDespreading
Despreading
*baseband
To thedecodingcircuit
Identifies the
correlation
peack and
distributes the
timing
Radio channel
estimation
through a pilot
sequence
Propagation
delay
compensation
Somma le
componenti
riallineate (MaximalRatio Combining)
Signal S2(t)*from RF
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Different RNC roles
RNC takes different roles to support macrodiversity:
RNC Serving
RNC Controlling
RNC Drift
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RNC roles
RNSRNC Serving and
Controlling
for ARNC
RNS
RNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub IubIub Iub
A connection B connection
RNC Drift andControlling
for B
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Handover
The UMTS handover is “mobile assisted”, that is:
the MU periodically makes measurements on the downlink channel
Sends such measurements to the RNC, which handles the add-drop of BTSs
If the handover is inter-RNC, one is Serving, and handles the add-drop of BTSs
The serving RNC can change through the SRNS (Serving Radio Network System
Relocation) procedure
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RNCRNC
The mobile is connected totwo cells belonging todifferent BTSs
BTS 1BTS 1
BTS 2BTS 2
LC=X
LC=Y
LC = Long Code
Soft Handover
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The mobile is connected totwo cells belonging to thesame BTS
LC=X
Sector 1Sector 1
Sector 2Sector 2BTSBTS
LC=Y
LC = Long Code
Softer Handover
RNCRNC
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UMTS OVERVIEW Maria Stella Iacobucci
Totally, 10 users in SHOV
• Total number of calls (1 call/user): 30
• Busy channels for each cell: 20
• Total number busy channels : 40
• Percentage of soft handover calls: 10/30 = 33%
• Busy channels/call: 40/30 = 1.33
Cell 1: 10 active link
to Cell 1, plus 5 utenti
in Soft Handover
Cell 2: 10 active link
to Cell 1, plus 5 utenti
in Soft Handover
Soft Handover and channels occupation
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Macrodiversity and radio independence
Legacy GSM/GPRS: possibility to re-use the CORE NETWORK architecture
Access
Network
Core networkCore networkUMTSUMTS
Radio Protocols
Radio indipendence
Radio dipendence BTS BTS BTS
RNC RNC
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S-RNS Relocation
MSC
Before handover
RNS RNS BSC
MSC
During s-handover
RNS RNS
MSC
After S-RNS relocation
RNS RNSBSC
MSC
after s-handover
RNS RNS
the Serving Radio Network System Relocation procedure moves the Iu interface fromthe old RNS to the new RNS
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Handover
Handover types:
intra-system intra-frequency Handover (Soft handover)
intra-system inter-frequency Handover (Hard handover)
Inter-system Handover (i.e. GSM-UMTS)
GSM/GPRS GSM/GPRS GSM/GPRS GSM/GPRS
UMTSMacro F1
UMTSMicro F2
Soft HO
Soft HO
Hard HO
Inter-System HO
UMTSMacro F1
UMTSMacro F1
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Inter Radio Access Technology (RAT)Handover
Allows the user to continue a conversation from UMTS to GSM coverage and viceversa
The Handover procedure is handled at the network side on the basis of themeasurement reports sent from the mobile
In the GSM network, the measurement reports are sent every 480 ms
In UMTS is the l’RNC which communicates to the mobile – with a measurement control message – the type of measures and the cell list
In UMTS the reporting is event triggered , to reduce the signaling load
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Inter RAT Handover: events
2d event : measurement activation on the GSM/GPRS network
2f event : measurement disactivation on the GSM/GPRS network
3a event : handover evaluation algorithm activation
QualityMeasurement
Event 2d
CPICH A(Quality)
Event 3a Event 2f
GSM Carrier Power(Quality)
Start inter-frequencymeasurement
Handover is triggered Stop inter-frequencymeasurement
Time
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Inter-Frequency measurements
•The handover among iso-frequency signals is executed throughmacrodiversity
•In the CDMA transmission and reception are continuous, and there is notime to make measurements
•Therefore, silence must be introduced to make measurements
•Silences are introduced through the Compressed Mode technique
•Alternatively, two receivers at frequencies can be used
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Downlink compressed Transmission
Tf = 10 ms Tempo di silenzio per
misure
SF=SF0
SF=SF0/2
SF=SF0
The two “Threshold_2d” and “Threshold_2f” sign the start and the end of compressed mode
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Handover FDD → GSM: Compressed Mode
10 ms radio frame
SF = 128SF = 64 SF = 64
SF = 128
SF = 128
For an intersystem Handover, the Mobile Terminal must make measurements on the GSM(GSM carrier Received Signal Strength Indicator , RSSI, e Path Loss); moreover, the mobileacquires frame synchronization and BSIC on BCCH frequencies. Terminals with onereceiver need intervals on the DL radio frame to make measurements (Compressed Mode,CM).
The CM implementation is based on SF reduction, always network initiated. TheCM is necessary even in UL for measurements on DCS 1800 MHz, in order to avoidinterferences from UMTS transmitter to DCS receiver
Gap for measurements
10 ms radio frame
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Measurements and Pattern in Compressed Mode
A typical Compressed Mode pattern shows 1 gap of 7 slot every 3
frames;
Six measurements on RRSI per each gap of 4,7 ms can be done
(approximately the duration of a GSM frame)
Three samples each measure on max. 32 declared adjacent cells = 96
samples
The duration of RSSI measurements is of 480 ms per 32 adjacent cells
frame10 ms
Gap4,7 ms
The BSIC identification of the three best adjacent cells can last up to 5s
with this pattern
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SF = 32 SF = 64 SF = 128
C64,2
C64,3
C32,1
C128,4
C128,5
C128,6
C128,7
SF = 256
Specifications indicate that the code assigned to the connection in
the frames in Compressed Mode is _in UL and in DL – the one with
SF/2 of the upper hierarchical level
Codes allocation in Compressed Mode
O
The voice call with AMR codec
uses, in Downlink, a code withSF 128 when CM is not used
X
Assigned to the voice call
Blocked from the call
O
X
XX
X
O
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n o d e
n o d e
n o d e
b t s
b t s
b t s
B S C B S C - - B B
C N R N
S
B S S
I U c s
A I U B
A B I S
Inter-MSC HO from UMTS to GSM
M S C M S C - - B B
UE
R N C R N C - - A A
3 G 3 G M S C M S C - - A A
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n o d e
n o d e
n o d e
b t s
b t s
b t s
3 G 3 G M S C M S C - - A A
R N C R N C - - A A C N
R N S
B S S
I U c s
A I U B
A B I S
Inter-MSC HO from UMTS to GSM
UE
M S C M S C - - B B
B S C B S C - - B B
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UE Node-B RNC CN 3G
83
Handover execution procedures
CN 2G BSS
HO evaluation
Relocation required
GSM: HO request
GSM: HO request ACK
HO from UTRAN command
GSM: HO access + HO complete
GSM: HO complete
Relocation command
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Inter RAT handover in the packet domain
Mobility procedures in the packet domain are :
Cell reselection:The mobile decides on the target cell and the reselection procedure: the network isonly informed of the cell change
Is used from the mobiles with an assigned packet service and that are sending datathrough common channels
Cell change:Is the network that, on the basis of the received measures, decides the target celland drives the cell change
Is used from the mobiles with an assigned packet service and that are sending datathrough dedicated channels
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UE Node-B RNC 3G PS CN
85
Cell reselection procedure
2G PS CN
PS RAB
Routing area update request
Context request
SRNS Context Request
SRNS Context Response
Context response
Context ack
Iu Release Command
Iu Release Complete
Deletion procedure
Routing area update accept
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UE Node-B RNC 3G PS CN
86
Cell change procedure2G PS CN
PS RAB
Routing area update request
Context request
SRNS Context Request
SRNS Context Response
Context response
Context ack
Iu Release Command
Iu Release Complete
Deletion procedure
Routing area update accept
UE state= Cell DCH
RRC Measurement Report
Cell change order from UTRAN
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UMTS Handover
The handover can be used even for:
Load balancing: the connections are distributed on more carriers or moresystems
Service Based Handover: is the possibility to optimally serve a connection,with the GSM or UMTS network on the service basis (i.e. voice on GSM,high speed on UMTS)
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UMTS radio interface
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Principal parameters
UTRA/FDD UTRA/TDD
Multiple access WCDMA Ibrido WCDMA+TDMA
Chip rate
Carrier spacing 5 MHz
3.84x2 Mcps (SF FDD:4-256, TDD 1-16)
Frame duration 10 ms
N. slot per frame 15
BTS synchronizationNot necessary Not necessary
but better
modulation DL: QPSKUL: Dual-code BPSK UL: QPSK
Coherent reception Uplink and downlink
Multi-rate Variabile SF + Multi-code + Multi-slot (TDD only)
DL: QPSK
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FDD and TDD
FDD
Has been standardized for public macro and micro cellular environmentwith data rates up to 384kbps and high mobility
TDD
Allows and efficient usage of the “unpaired” spectrum and supports datarates up to 2 Mbps
Is useful in environments with high traffic density and indoor coverage,where applications require high highly asymmetric data rates
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TDD (TD-CDMA) component
F r e q
u e n c
y
8 TCH
per time
slot
One Time Slot
3. 8 4
M c h
i p / s
0. 2 2
r 1 2 3 . . . 14 15
Codes
1-16
Energy
Time
frame with
15 time slots
WB-TDMA/CDMA
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TDD frame
3.84
Mchip/s
time
frequency
666 µs
10 ms
10 ms
10 ms
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Logical, physical and transport channels
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Logical Channels
Logical channels are services offered from the MAC (Medium Access Control ) tothe higher levels and are characterized from the Information Content :
Broadcast Control Common Channel (BCCH): brings the System Info and network configuration parameters
Common Control Channel (CCCH): carries bidirectional control information for themobiles that are not in Connected Mode*
Paging Common Channel (PCCH): used from the network to set up a connection withthe MT
Dedicated Control Channel (DCCH): carries control information for the MTs in “Connected Mode”
Dedicated Traffic Channel (DTCH): carries user information for the MTs in “Connected Mode” ( payload ).
*are in Idle Mode and there is no signalling connection between UTRAN and MT
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Transport channels
Transport channels are the resources offered from the physical layer to higherlevel protocol; the channels can be Common (l’UE* must be explicitlyaddressed through a MAC identifier) or Dedicated .
Dedicated Channel (DCH), Downlink o Uplink; carries user plane or signaling planeinformation
Broadcast Channel (BCH), downlink transport channel which carries system or cellinformation
Forward Access Channel (FACH), DL, used to carry control or data packetinformation
Paging Channel (PCH), DL, used from the network to initiate a communication
Random Access Channel (RACH), used from the MS in UL to access the system orsending data packets
* UE= User Equipment
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Logical and transport channels mapping
CCCH DCCH/DTCH
RACH DCH
PCCH BCCH
PCH BCH
CCCH DCCH/DTCH
FACH DCH
Level 2
Level 1
Uplink Downlink
Logical
channels
Transport
channels
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Physical channels and indicators
Physical channels are the resources used for radio transmission: are defined bya spreading code , a carrier , a scrambling code
The correspondence between physical and transport channels is that level 2(MAC) protocols transfer elementary data units (Radio or Transport Blocks ) tothe physical layer that are elaborated (i.e. error correction coding) and sent tothe physical channels
All the physical channels (indicators, preambles, and synchronization channels )are sent in all Time Slots of the FDD frame
Indicators are signaling entities with Boolean value and are not connected totransport channels
An example of indicators are: AICH, Acquisition Indicator Channel , for the ack
to the PRACH preamble; PICH, Paging Indicator Channel, which indicates to theUE in Sleep Mode* to listen to the paging channel in a subsequent frame
* Discontinuous reception mode for energy saving
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Physical and transport channels mapping
RACH
DPCH (DPDCH)PRACH
DCH PCH FACH
S-CCPCH
BCH DCH
P-CCPCH
Uplink Downlink
Physical
channels
Transport
channels
DPCH (DPDCH)
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[CCCH:RACH] RRC CONNECTION REQUEST
UE UTRAN
On physical channel PRACH
[CCCH:FACH] RRC CONNECTION SETUP
On physical channel S-CCPCH
[DCCH:DCH] RRC CONNECTION SETUP COMPLETE
Example: connection establishment
On physical channel DPCH
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Livello RLC
RLC SDU 1(DTCH)
RLC SDU N(DTCH)
H H
Payload – data block (i.e. TCP/IPpacket)
Header RLC adding
Segmentation and user data transmission
Application
level*
* An intermediate level can exist (PDCP, Packet Data Convergence Protocol)
to compress TCP/IP headers
Segmentation in Ninformation units
SDU= Service Data Unit
RLC= Radio Link Control
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MAC PDU 1(Transport Block)
Transport
Channel (DCH)
MAC PDU N(Transport Block)
RLC Level
MAC Level
Elementary unit exchanged
between MAC and PHY
RLC SDU 1(DTCH)
RLC SDU N(DTCH)
H H
MAC SDU 1 MAC SDU NH H
Header MAC addition
RLC Blocks to send in a TTI (Transmission Time Interval)
which lasts one or more frames
PDU= Protocol Data Unit
Segmentation and user data transmission
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MAC PDU 1
(Transport Block)
Transport
channel (DCH)
MAC PDU N
(Transport Block)
Elementary unit
exchanged between MAC
and PHY Transport Format*
calculation
Radio BlocksMultiplation and
Coding
TFCIelaboration
MAC
PHY
To the physical channel
DPCH (DPDCH)To the physical DPCH
(DPCCH)
* Transport Format is calculated from the number and the dimension of the
Transport Block; the whole of possible Transport Format is the Transport
Format Set.
Segmentation and user data transmission
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A) In the simplest cases, like in the previous example, to a transportchannel corresponds one logical channel
B) In general, it is possible to multiply more than one logical channel on onetransport channel (MAC multiplation )
C) Finally, more transport channels can be multiplied on one physicalchannel
In this case, the whole of Transport Format is the Transport Format Combination
Follows an example of a bearer service incuded in the 3GPPspecifications
Segmentation and user data transmission
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Example: 144 kbps (DL) service
Rate Matching (RM) can reach NRM bit per repetition, or remove some bits (Code Puncturing) according to a
puncturing mask
Turbo code R=1/3
R ad io fr am e FN =4 N+ 1 R adi o f ra me FN= 4N +2 R ad io fr am e F N= 4N+ 3Radio frame FN=4N
Informationdata
(TransportBlock)
CRC Attachment
2nd interleaving
4320
4232 88 4232 88 4232 88 4232
#1 4232 #2 4232 #1 88 #2 88 #3 88 # 4 88
4320 4320 4320
8464
8688
2896
CRC16 bit2880
2880
88
352
360
100
CRC12 bit
Rate matching
1st interleaving
CRC Attachment
DTCH (Payload ) DCCH (signaling)
8464
#1 4232 #2 4232
352
100
Radio Frame
Segmentation
slot segmentation
240ksps DPCH(including DPCCH bits)
Rate matching
1st interleaving
0 1 14• • • •
288 2880 1
288• • • •
14
0 1 14• • • •
288 2880 1
288• • • •
14
0 1 14• • • •
288 2880 1
288• • • •
14
0 1 14• • • •
288 2880 1
288• • • •
14
Termination 12 bit112
Tail8 bit
Convol. Coding R=1/3
TTI is 4frames long
(40 ms)
Informationdata
(TransportBlock)2880
DCH #1 DCH #2
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480kbpsDPDCH
Turbo Coding R=1/3
Radio frame FN=4N+1 Radio frame FN=4N+2 Radio frame FN=4N+3Radio frame FN=4N
Informationdata
(Transport Block)
CRC attachment
2nd interleaving
4800
4702 98 4702 98 4702 98 4702
SMU#1 4702 SMU#2 4702 SMU#198
SMU#298
SMU#398
SMU#498
4800 4800 4800
4350
8688
2896Termination12 bit
2880
2880
98
360
360
112
Tail8 bit100
1st interleaving
CRC attachment
Tailbit attachment
Conv. Coding R=1/3
Rate matching
1st interleaving8700
4350
SMU#1 4702 SMU#2 4702
90 90 90 90
15kbpsDPCCH
Rate matching
Radio Frame Segmentation
100
CRC16 bit
CRC12 bit
TTI di 4trame (40ms)
Informationdata(Transport Block)
2880
DTCH (Payload )DCCH (signaling)
Example: 144 kbps (DL) service
CRC: Cyclic Redundancy Check DCH multiplation at physical level
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Transport channels coding and multiplation (DL)
Radio blocks are elaborated in a TTI interval; for example the output of the AMR
voice coder is of 20 ms (TTI) duration
Frame Segmentation
Multiplexing
2nd Interleaving
Mapping to
Physical channelsAdd CRC perTr. block
Add CRC perTr. block
Channelcoding
Channelcoding
TransportChannel 1
Rate Matching Rate Matching
1st Interleaving 1st Interleaving
TransportChannel N
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Il CRC (Cyclic Redundancy Check)
Logical circuitwith generatorpolinomial
Data Block(Transport
Block)
Error correction
coding (Rate 1/3)
Data block + CRC Coded
CRCData Block(Transport
Block)
Trasmission
CRC
Decoded
Data block
Reception Logical
circuit
CRC
CRCrecalculate
d
CRC decoded
Channel decoder
Block + CRC Revealed
Radio
channel
M a t c h
i n g ?
Typical lengths of CRC in UMTS are 12 or 16 bit
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DL dedicated channel: frame structure
Tslot = 2560 chip , 10x2k bit (k=0..7); SF = (512/2k)
Tframe = 10 ms
Slot #iSlot #0 Slot #1 Slot #14
Tslot =0,667 ms
Tframe = 10 ms
Powercontrol
NTPC bit Ndata2 bit
DPDCH
N TFCIbit
Pilot
Npilot bitNdata1 bit
DPDCH DPCCH DPCCH
Formatindicator
(DPCH, Dedicated Physical Channel) in DL:
-DPDCH (Dedicated Physical Data Channel)
-DPCCH (Dedicated Physical Control Channel)
Every TS of the frame isassigned to the samecommunication
Data channels carry payload andcontrol messages of higher levelprotocols
DataData
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Tslot = 2560 chip , 10x2k bit (k=0..7); SF = (512/2k)
Tframe = 10 ms
Slot #iSlot #0 Slot #1 Slot #14
Tslot =0,667 ms
Tframe = 10 ms
Powercontrol
NTPC bit Ndata2 bit
DPDCH
N TFCIbit
Pilot
Npilot bitNdata1 bit
DPDCH DPCCH DPCCH
Formatindicator
Indicates data blockstransmission format:
channels coding,discontinuous transmissionpresence, silencedescriptor, etc.
DPDCH e il DPCCH are sentwith the same SF, variablefrom 4 and 512
DL dedicated channel: frame structure
(DPCH, Dedicated Physical Channel) in DL:-DPDCH (Dedicated Physical Data Channel)
-DPCCH (Dedicated Physical Control Channel)
DataData
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Tslot = 2560 chip , 10x2k bit (k=0..7); SF = (512/2k)
Tframe = 10 ms
Slot #iSlot #0 Slot #1 Slot #14
Tslot =0,667 ms
Tframe = 10 ms
Powercontrol
NTPC bit Ndata2 bit
DPDCH
N TFCIbit
Pilot
Npilot bitNdata1 bit
DPDCH DPCCH DPCCH
Formatindicator Data
Carries a command to
indicate to increase ordecrease the transmittedpower (es. 1 dB)
Carries a known sequenceused from the receiver forchannel estimation
DL dedicated channel: frame structure(DPCH, Dedicated Physical Channel) in DL:
-DPDCH (Dedicated Physical Data Channel)
-DPCCH (Dedicated Physical Control Channel)
Data
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Radio interface: modulations
QPSK: 2 bit per symbol, 4 symbols in
the constellation, DPDCH and DPCCHare time multiplied
FDD DL e TDD: QPSK
Q-Branch
I-Branch
Each symbol carries DPCCH or
DPDCH
BPSK= Binary Phase Shift Keying, QPSK= Quad Phase Shift Keying
Dual BPSK: 2 symbols perconstellation, 1 bit per symbol perDPDCH e DPCCH
FDD UL: Dual BPSK
Q-Branch
I-Branch
DPDCH
DPCCH
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Example: DPCH DL structure (Spec. 3GPP)
DPDCHBits/Slot
DPCCHBits/Slot
Slot Format#i
Channel BitRate (kbps)
Channel SymbolRate (ksps)
SF Bits/ Slot
NData1 NData2 NTPC NTFCI NPilot
0 15 7.5 512 10 0 4 2 0 41 15 7.5 512 10 0 2 2 2 42 30 15 256 20 2 14 2 0 23 30 15 256 20 2 12 2 2 2
4 30 15 256 20 2 12 2 0 45 30 15 256 20 2 10 2 2 46 30 15 256 20 2 8 2 0 87 30 15 256 20 2 6 2 2 8
8 60 30 128 40 6 28 2 0 4
9 60 30 128 40 6 26 2 2 410 60 30 128 40 6 24 2 0 811 60 30 128 40 6 22 2 2 8
12 120 60 64 80 12 48 4 8 813 240 120 32 160 28 112 4 8 8
14 480 240 16 320 56 232 8 8 1615 960 480 8 640 120 488 8 8 16
16 1920 960 4 1280 248 1000 8 8 16
Useful for data transmission at 384
kbit/s (coding rate 1/3: ∼950 kbit/s)Useful for voice coding
at 12,2 kbit/s (coding
rate 1/3: ∼40 kbit/s)
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SF = 32 SF = 64 SF = 128
C64,0
C64,1
C32,0
C128,0
C128,1
C128,2
C128,3
SF = 256
XX
XX
X
The code CSF,0 is always blocked for common channels In each cell no more than (128-4) codes with SF 128 for voice and (8-1)
codes with SF 8 for data connections at 384 kbit/s.
OVSF code allocation
XX
X Used for common channel
signaling (BCCH, Pilot,
Paging, FACH, PICH, AICH)
X
X
Assigned to common channels
X
XX
XX
X
X
Blocked from common channels
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cos(ωωωωt)
I
Q
c scrambS P cch sin(ωωωωt)DPCHDownlink
cCh : Spreading code
c scramb: Scrambling code
Downlink modulation (Single Signal)
DPDCH and DPCCH use the same OVSF code, different for each user; it is
possible the multicode transmission with DPDCH assigned to the UE (howeveronly one DPCCH per UE is transmitted)
Scrambling codes are pseudonoise sequences interrupted at 38400 chip,
extracted from a whole of (218-1) codes and grouped in 512 subset including 1
primary and 15 secondary codes; each cell uses a different subset univocally
identified from the primary scrambling code
Filter with Roll-off = 0,22
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cos(ωωωωt)
I
Q
C scrambS P C spread1
sin(ωωωωt)
DPCH n°1
Downlink Modulation (all the DPCH)
I
Q
C scrambS P C spreadNDPCH n°N GN
G1
ΣΣΣΣ
ΣΣΣΣ
Gi: amplitude signal which definesthe transmitted power
adder: baseband signalscombining
Filter with Roll-off 0,22
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(Tx OFF)
256 chip
CPICH (20 bits, SF=256)
P-CCPCH (18 bit, SF = 256)
Tslot = 2560 chip (0,667 ms)
Ttrama = 10 ms
Slot #iSlot #0 Slot #1 Slot #14
Campo DatiNdata bit
NTFCI bit NPilot bit
Tslot = 2560 chip , 20x2k bit (k=0..6); SF = (256/2k)
S-CCPCHDL common channels: frame structure
P-CCPCH (Primary Common Control Physical Channel): broadcasts system infos. In the initial gapprimary and secondary SCH are sent
S-CCPCH (Secondary CCPCH ): is of variable SF. Carries the paging, signaling channels or small traffic
volumes (max 32 kbit/s). More than one S-CCPCH per cell can be configures (es. 1 S-CCPCH perpaging, 1 per dati e segnalazione)
CPICH (Common Pilot Channel): used for channel estimation and cell scrambling code research
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Data fieldNdatabit
Tslot = 2560 chip , 10x2k bit (k=0..6); SF = (256/2k)
Tframe = 10 ms
DPDCH(modulator branch I)
Slot #iSlot #0 Slot #1 Slot #14
Pilot
Npilot
bit NTPC bitNFBI bit
Format indicator
N TFCI bit
Tslot = 2560 chip, 10 bit (SF=256)
0,667 ms
Feedbackinformation
Power controlDPCCH(modulator branch Q)
DPCH UL: frame structure
Feedback field carries physical layer signaling, used for antenna diversitytechniques
DPCCH control field has fixed SF and equal to 256, while the SF of data
field DPDCH is variable (4-256).
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Data fieldNdata bit
Tslot = 2560 chip , 10x2k bit (k=0..3); SF = (256/2k)
Ttrama = 10 ms
Message Part
Slot #iSlot #0 Slot #1 Slot #14
Pilot
Npilot bit
FormatoIndicatorNTFCI bit
0,667 ms
Control Part
Tslot = 2560 chips, 10 bits (SF=256)
PRACH channel in UL: frame structure
PRACH (Physical Random Access Channel) is a common channel with contentionaccess, anticipated by preambles transmitted with increasing power*
Is used both for network access, and for signaling messages and traffic data (up to32 kbit/s).
* PRACH transmission is done only if preamble is network acknowledged
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Uplink modulation
OVSF codes are the same for each UE and depend on the used SF
The network sends to the UE the eventual power offset (βC and βD factors)
DPCCH is sent even during inactivity data periods
Scrambling codes are complex pseudonoise sequences different per each UE, chosen in awhole of 224 Gold codes of length 225-2 and interrupted at 38400 chip
Spreading codes (OVSF)
cD, cC : Spreading Codes
c’ scramb: Scrambling Codes
DPDCH
cD
DPCCH
cC
Q∗∗∗∗ j
I+jQ
c’scramb
cos(ωωωωt)
Real
Imag
sin(ωωωωt)
βD
I
βC
Filter with Roll-off 0,22
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Uplink Variable Rate
1-rate
Rate variabile
1/2-rate
1/4-rate
0-rate
10 ms
: DPCCH (Pilot+TPC+RI)
: DPDCH (Data)
R = 1 R = 1/2 R = 0 R = 0 R = 1/2
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Example: DPCH UL (Spec. 3GPP) structure
Useful for voice codingat12,2 kbit/s (coding rate1/3: ∼40 kbit/s)
Useful for data transmissionat a 64 kbit/s (coding rate
1/3: ∼200 kbit/s)DPDCH Uplink
Slot Format #i Channel Bit Rate(kbps)
Channel SymbolRate (ksps)
SF Bits/Frame
Bits/Slot
Ndata
0 15 15 256 150 10 10
1 30 30 128 300 20 20
2 60 60 64 600 40 40
3 120 120 32 1200 80 80
4 240 240 16 2400 160 160
5 480 480 8 4800 320 320
6 960 960 4 9600 640 640
DPCCH Uplink
SlotFormat #i
ChannelBit Rate(kbps)
Channel SymbolRate (ksps)
SF Bits/Frame
Bits/Slot
Npilot NTPC NTFCI NFBI
0 15 15 256 150 10 6 2 2 01 15 15 256 150 10 8 2 0 02 15 15 256 150 10 5 2 2 13 15 15 256 150 10 7 2 0 1
4 15 15 256 150 10 6 2 0 2
5 15 15 256 150 10 5 1 2 2
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Example: 144 kbit/s data service
144+15=159 kbit/s
477 kbit/s
480 kbit/s
3,84 Mchip/s
User bit rate + associated signaling
Signal in input at RF modulator
Rate Matching (Bit Repetition)
Multiplication for OVSF
Code of length (Spreading Factor) = 8
Error correction coding,
Rate = 1/3
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Variable Bit Rate on DPCH
The transmission at variable bit rate in Uplink uses variable SF for the DPDCH; thecontrol field (and therefore the TFCI) is sent at fixed SF
In Downlink the SF of data and control fields is the same; the variable bit ratetransmission is obtained using DTX
It is possible to change transmission speed with channel reconfigurationprocedures
R = 1
R = 1/4
R = 0
Downlink DPCCH (Pilot+TPC+TFCI) Downlink DPDCH (Data)
0.667 ms
variableBit Rate (R)
Uplink DPCCH (Pilot+TPC+TFCI)
R = 1 R = 1/2 R = 0 R = 0 R = 1/2
Uplink DPDCH (Data)
10 ms
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An introduction to UMTS radio protocols
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UMTS network architecture
Packet domain
RNCRNC
RNC areacell
RNCRNC
Iub
Circuit domain
RNCRNC
MSCMSC
VLR
MSCMSC
HLRHLRPLMN, ISDN, PSTN...
GatewayMSC
GatewayMSC
HLR
Iu (CS)
Iu (CS)
Node B
UE
SGSNSGSNGGSNGGSN
Public packet
network
Iu (PS)Gn
Gi
Uu
Iur
Iu (CS)
Iur
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Control and user plane
MAC
RRC
Control Plane User Plane
RLCRLC
RLC
PDCPPDCP
PDCP
Signaling
messages
handling and
transportation
over control
channels
Control and traffic channels are logical channels, defined on the basis of carried
information
Logical channels
Physical layer (Transmission) L1 (PHY)
L2/RLC
L2/MAC
L3
payload handling
and transportation
over control
channels
Transport channels
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Functionalities of UMTS radio protocols
MAC
RRC
Control Plane User Plane
RLCRLC
RLC
PDCPPDCP
PDCP
Canali logici
Physical layer (Transmission) L1 (PHY)
L2/RLC
L2/MAC
L3
Canali di trasporto
Radio Resource ControlRadio resources
assignment and release,
admission and congestion
control, handover
Radio Link Control
Flow control,
segmentation, error
and sequence control,retransmissions
Medium Access Control
Packet queuing , users
priority handling Physical Layer: Power Control, modulation, channel
coding, synchronization, multiplexing, measurements
Packet Data ConvergenceProtocol: IP header
compression for radio
transmission
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UMTS Protocols termination
UTRAN
Iu
Iur
Iub
VLR HLR
GSN+
MSC+
UMTS Core Network
PCM
Packet Switched
Circuit Switched
Uu
Node B
Node B RNC
Node B
Node B
RNC
RRC RRC
MAC MAC
RLC RLC
PHY
PHY
IP/GTP
ATM/AAL2
CMM
CC
CCMM CMM
SM
SMPMM
Level 2 e 3 ( AccessStratum) protocols are
terminated ar the RNC
The radio physical levelis node B terminated
Session protocols are (Non- Access Stratum) terminated inCore Network
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Utran: access procedures
UE
RRC connection request
UE capabilities
CNRAB assignment
QoS RAB parameters
RAB parameters
UE capabilities
RRM strategies
Iu parameters
RB parameters
UTRAN
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RRC Protocol States Idle mode:
No dedicated radio resource isallocated
the UE has to perform neighborcell monitoring, cell reselection,paging channel observation,broadcast message receptionand decoding
Connected mode: A duplex radio connection exists
A differentiation has to be madewith respect to dedicated andshared connections
Idle
Mode
Connected
mode
Established dedicated connection
Release connection
Established
shared connection
Release logical connection
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An introduction to Radio Access Bearer (RAB)
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Is the transport service offered from UTRAN to the ent-to-end
architecure of UMTS system
TE MT UTRAN CNIuEDGENODE
CNGateway
TE
End-to-End Service
TE/MT LocalBearer Service
UMTS Bearer Service External BearerService
UMTS Bearer Service
Radio Access Bearer Service CN BearerService
Backbone
Bearer Service
Iu Bearer
Service
Radio Bearer
Service
UTRAFDD/TDD
Service
PhysicalBearer Service
For each RAB aredefined: traffic class(i.e. conversational or
interactive), maximumbit rate , tolerated
delay, CS or PS domain,supported service or
application (i.e. voice)
RAB is mapped on a Radio Bearer
by configuring parameters of
radio (PHY) and layer 2 protocols
(MAC and RLC)
Radio Access Bearer (RAB)
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Radio Access Bearer (RAB)
* High Speed DL Shared Channel, used only with HSDPA (High Speed Downlink Packet Access) introduced with UMTS Release 5
RAB is the bearer service offered from UTRAN; RAB are distinguished from peak bit rate,allowed delay, residual error rate, and are grouped into four service classes
PacketHS-DCHModerately sensitive todelay
10-41200-14400Interactive orbackground
PacketDCHSensitivity to jitter10-464Streaming
CircuitDCHSensitivity to jitter10-457,6Streaming
CircuitDCHSensitivity to delay and jitter
10-664;128;384Conversational(ISDN,videocall)
PacketDCHModerately sensitive todelay
10-464-384Interactive orbackground
CircuitDCHSensitivity to delay and jitter
10-34,75-12,2Conversational (voicewith adaptivecoding)
domainTransportchannel
Delay sensitivityResidualBER
Peak bit rate(kb/s)
Service class
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RAB and Signaling Radio BearerFor some services more RAB subflows are identified, for example the ones
that carry least significant bits of the voice coder. Different subflows can be
treated differently from level 2 protocols (i.e. channel coding and CRC can
be different)
Signaling Radio Bearer (SRB) are bearers of the control plane; they
autonomously subsist if no payload is exchanged (i.e. paging or call setup)
or they are associated to a (look at the table) Radio Bearer and with it
multiplied. SRB bring signaling of the radio RRC protocol or of the Non
Access Stratum (CM, MM) protocols.
Service Class Peak Bit Rate (kbit/s) SRB Bit Rate (kbit/s) domain
Conversational(voice AMR)
12,2 UL/DL 3,4 UL/DL Circuit
Conversational(ISDN, Videoconference)
64 UL/DL 3,4 UL/DL Circuit
Interactive or Background 64 UL/ 384 DL 3,4 UL/DL Packet
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TTI: Transmission Time Interval
TTI is the minimum interval for transmission resourcesassignment, and can be one or more frames
Typically TTI is equal to 20ms for the voice call like in the GSM system
In the case of data transmission, TTI can be extended up to 40ms
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Layer RAB/Signalling RB RAB subflow #1 RAB subflow #2 RAB subflow #3
Logical channel type DTCH
RLC mode TM TM TMPayload sizes, bit 39, 81 103 60
RLC
Max data rate, bps 12200
MAC header, bit 0MAC
MAC multiplexing N/A
TrCH type DCH DCH DCHTB sizes, bit 39, 81 103 60
TF0, bits 0 0 0TF1, bits 39 103 60
TFS
TF2, bits 81 - -TTI, ms 20 20 20
Coding type CC 1/3 CC 1/3 CC 1/2
Layer 1
CRC, bit 12 N/A N/A
The DTCH is mapped on three DCH (DTCH:DCH ) corresponding to three
subflows
Transport channel Logical channelTransport
Block
dimension
Information unit
Payload
Transmission Interval
Example: voice RAB at 12,2 kbit/s+SRB at 3,4 kbit/s
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For each DCH three transmission format exist: per DTX (inactive source), perSID (Silence Descriptor of background noise), per voice frame
Example: voice RAB at 12,2 kbit/s+SRB at 3,4 kbit/s
Layer RAB/Signalling RB RAB subflow #1 RAB subflow #2 RAB subflow #3
Logical channel type DTCH
RLC mode TM TM TMPayload sizes, bit 39, 81 103 60
RLC
Max data rate, bps 12200
MAC header, bit 0MAC
MAC multiplexing N/A
TrCH type DCH DCH DCHTB sizes, bit 39, 81 103 60
TF0, bits 0 0 0TF1, bits 39 103 60
TFS
TF2, bits 81 - -TTI, ms 20 20 20
Coding type CC 1/3 CC 1/3 CC 1/2
Layer 1
CRC, bit 12 N/A N/A
Posible Transport FormatTransport Format (TFS)
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RAB/signalling RB SRB#1 SRB#2 SRB#3 SRB#4Layer
User of Radio Bearer RRC RRC NASHigh prio
NASLow prio
Logical channel type DCCH DCCH DCCH DCCH
RLC mode UM AM AM AMPayload sizes, bit 136 128 128 128
Max data rate, bps 3400 3200 3200 3200
RLC
AMD/UMD PDU header, bit 8 16 16 16
MAC header, bit 4 4 4 4MAC
MAC multiplexing 4 logical channel multiplexing
TrCH type DCH
TB sizes, bit 0, 148 (alt 0, 148)TF0, bits 0TFS
TF1, bits 148TTI, ms 40Coding type CC 1/3
Layer 1
CRC, bit 16
Transport channel Logical channelSignaling type
Possible Transport Format
Example: voice RAB at 12,2 kbit/s+SRB at 3,4 kbit/sControl plane SRB; DCCH are 4, and are MAC multiplexed on a DCH (DCCH:DCH )
NAS = Non Access Stratum (protocols terminated out of the UTRAN, i.e. in CN)
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TFCS size 6TFCS (RAB subflow#1, RAB subflow#2, RAB subflow#3,DCCH)=
(TF0, TF0, TF0, TF0), (TF1, TF0, TF0, TF0), (TF2, TF1, TF1, TF0),(TF0, TF0, TF0, TF1), (TF1, TF0, TF0, TF1), (TF2, TF1, TF1, TF1)
All possible Transport Format combinations
for voice and signaling
The whole of 6 combinations (TFC, Transport Format Combination) is the
TFCS (Transport Format Combination Set)
the TFC is coded each TTI in the Transport Format Combination Indicator (TFCI), send on the DPCCH
At different Transport Format correspond different instantaneous bit rate
because the Transport Blocks have different dimensions
Example: voice RAB at 12,2 kbit/s+SRB at 3,4 kbit/s
Six possible Transport Format combinations for the RAB: DTX, SID and
voice frame, with or without associated SRB (DCCH)
DTX SID Voice
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RAB differences: Examples (1)Characteristics of a Conversational RAB CS, 64 kbit/s
Layer RAB/Signalling RB RAB
Logical channel type DTCH
RLC mode TMPayload sizes, bit 640
Max data rate, bps 64000
RLC
TrD PDU header, bit 0
MAC header, bit 0MAC
MAC multiplexing N/A
TrCH type DCH
TB sizes, bit 640TF0, bits 0x640TFS
TF1, bits 2x640
TTI, ms 20
Coding type TC
CRC, bit 16
Layer 1
Max number of bits/TTI after channel coding 3948
Requirements of a Conversational RAB :
Limited delay and jitter
CBR source or of “On-Off” type
No acknowledged transmission
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Layer RAB/Signalling RB RAB
Logical channel type DTCH
RLC mode TMPayload sizes, bit 640
Max data rate, bps 64000
RLC
TrD PDU header, bit 0
MAC header, bit 0MAC
MAC multiplexing N/A
TrCH type DCH
TB sizes, bit 640TF0, bits 0x640TFS
TF1, bits 2x640
TTI, ms 20
Coding type TCCRC, bit 16
Layer 1
Max number of bits/TTI after channel coding 3948
RLC in Transparent Mode: RLCdata units are notacknowledged
TTI of 20 ms
Transport Formats correspond toistantaneous bit rates 0 and 64
kbit/s
RAB differences: Examples (2)
Characteristics of a Conversational RAB CS, 64 kbit/s
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RAB Streaming CS, 57,6 kbit/s
RAB Streaming requirements:
Limited Jitter
No acknowledgment/retransmission of received data units
VBR souces
Layer RAB/Signalling RB RAB
Logical channel type DTCH
RLC mode TM
Payload sizes, bit 576
Max data rate, bps 57600
RLC
TrD PDU header, bit 0
MAC header, bit 0MACMAC multiplexing N/A
TrCH type DCH
TB sizes, bit 576
TF0, bits 0x576TF1, bits 1x576TF2, bits 2x576TF3, bits 3x576
TFS
TF4, bits 4x576TTI, ms 40
Coding type TCCRC, bit 16
Layer 1
Max number of bits/TTI after channel coding 7116
RAB differences: Examples (3)
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RAB Streaming CS, 57,6 kbit/sLayer RAB/Signalling RB RAB
Logical channel type DTCH
RLC mode TM
Payload sizes, bit 576
Max data rate, bps 57600
RLC
TrD PDU header, bit 0
MAC header, bit 0MACMAC multiplexing N/A
TrCH type DCH
TB sizes, bit 576
TF0, bits 0x576TF1, bits 1x576TF2, bits 2x576
TF3, bits 3x576
TFS
TF4, bits 4x576TTI, ms 40
Coding type TC
CRC, bit 16
Layer 1
Max number of bits/TTI after channel coding 7116
Transparent RLC : RLC dataunits are not acknowledged
TTI of 40 ms
Transport Formats correspond toinstantaneous bit rate 0; 14,4;28,8; 43,2 e 57,6 kbit/s
RAB differences: Examples (4)
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Interactive/Background PS RAB, 64 kbit/s
Layer RAB/Signalling RB RAB
Logical channel type DTCHRLC mode AM
Payload sizes, bit 320Max data rate, bps 64000
RLC
AMD PDU header, bit 16
MAC header, bit 0MAC
MAC multiplexing N/A
TrCH type DCH
TB sizes, bit 336TF0, bits 0x336
TF1, bits 1x336
TF2, bits 2x336TF3, bits 3x336
TFS
TF4, bits 4x336
TTI, ms 20
Coding type TCCRC, bit 16
Layer 1
Max number of bits/TTI after channel coding 4236
RLC operates in Acknowledged ModeTransport Formats correspond toinstantaneous bit rates 0, 16, 32, 48 and64 kbit/s
RAB differences: Examples (5)
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Physical Level Procedures
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Open Loop Power Control on PRACHThe mobile sends the PRACH with the minimum power necessary ho
have at the receiver side an adequate C/I
Node B
RNC
Configurationparameters: power ofl
CPICH, P-CCPCH and S-
CCPCH, offset tocommunicate to the
mobiles
Iub
UE is informed on the BCCH
System Info del BCCH of CPICH power, on the
interference at Node B side
and on the offset* to apply
UE measures the power received onCPICH and calculates path
attenuation; the power on PRACH
preamble [dB] is: P_Tx_UE=Path_Att+Inteference+offset_PRACH
C/I at Node B [dB] = P_Tx_UE − Path_Att − Interference
* offset [dB] can have
a positive or
negative value
depending on therequired C/I
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Instantaneously controls the UE transmission power to maintain the required
C/I (SIR in 3GPP terminology).
Node B
RNC
Configuration parameters: step
∆TPC of Power Control (es. 1 dB),C/I target for the DCH
Iub
L’UE, according to the
command received in the
previous Time Slot, increases
or decreases the transmission
power of ±∆TPC
Measures thel C/I on the DPCCH UL
(campo pilota): if C/I_DPCCH<C/I_Target,
is sent the “UP” (1) command on DPCCH
DL. If C/I_DPCCH>C/I_Target, the sentcommand is “DOWN”(-1)
Closed Loop Power Control on DPCH: Uplink
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Instantaneously controls the node B transmission power to limit the
interference and maintaining the connection quality requirements in term of
Block Error Rate
Node B
RNC
Configuration parameters:
step ∆TPC of Power Control(i.e. 1 dB), BLER target forRAB, initial power on DPCH DL
Iub
L’UE is informedthrough the
Information Element
“Quality Target” of the
BLER Target
Closed Loop Power Control on DPCH: Downlink
The UE, through an internal table
terminal dependent, maps a
C/I_Target to the BLER_Target
network indicated
* The algorithm allows the UE to operate at lower C/I
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Node B
RNC
Iub
The node B, according with
the command received theprevious time slot,
increases or decreases the
±∆TPC
L’UE measures the C/I on DPCCH DL (pilot
field): if C/I_DPCCH<C/I_Target, sends to
Node B the “UP” (1) command on the
DPCCH UL. If C/I_DPCCH>C/I_Target, the
generated command is “DOWN”(-1)
3GPP specifications handle faulty terminals by limiting the transmitted power
to one UE and by containing the consecutive (+ DTPC) increments
Closed Loop Power Control on DPCH: Downlink
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Tslot =0.667 ms
Powercontrol
NTPC bit Ndata2 bit
DPDCH
N TFCIbit
Pilot
Npilot bit
Datafield 1
Ndata1 bit
DPDCH DPCCH DPCCH
Formatindicator
Datafield 2
DPCCH Downlink
Indicates to increase or decrease the transmittedpower
Known sequence used forchannel estimation
Closed Loop Power Control on DPCH
Pilot
N pilot bit NTPC bitNFBI bit
Format indicator
N TFCI bit
Feedbackinformation
Powercontrol
DPCCH UplinkTslot =0.667 ms
Indicates to increase or decrease thetransmitted power
Known sequence used for
channel estimation
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Outer Loop Power Control on DPCH
Nodo B
RNC
RNC calculates the BLER from CRC* on DCH UL
radio blocks. If the BLER is lower than RABrequirements, indicates to Node B to decrease the
C/I_Target (i.e. of 0,2 dB); in the opposite case,
indicates to increase thel C/I_Target
Iub
L’UE calculates the BLER of
DCH DL through the CRC* and,
following the corresponding
table BLER and C/I, changes the
C/I_Target of the Closed Loop
Downlink procedure
Uses the C/I_Target recalculatedon the basis of RNC in the Closed
Loop Uplink procedure
Updates the C/I_Target (Node B side) and BLER_Target (UE side) used in the
Closed Loop procedure. Outer Loop algorithms, that operate on a scale of centsof ms, are manufacturer dependent
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-20 -19 -18 -17 -16 -150,000
0,025
0,050
0,075
0,100
0,125
Fitting: Gauss
µgauss
= -18.2 dB
σgauss
= 0.41 dB
PDF of C/I ratio at Node B - System Load: 74.4 kbps/MHz/cell
[email protected] kbps, Perfect Power Control
P r o b a b i l i t y D e n s i t y F u n c t i o n
Carrier to Interference Ratio at receiver side (dB)
Power Control Uplink: C/I PDF at the Node B
C/I PDF function is very narrow because the power control algorithm
points to the C/I_Target.
F o n t : C o R i T e l ( P a c e A . – M a z z e n g a F .
)
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Power Control Uplink: PDF of UE transmitted power
Dynamic of transmitted power is wide: path attenuation varies in function of
distance and fading
F o n t : C o R i T e l ( P a c e A . – M a z z e n g a F .
)
-70 -60 -50 -40 -30 -20 -10
0,00
0,01
0,02
PDF of UE Tx Power - [email protected] kbps, System Load: 61.6 kbps/MHz/cell
Perfect Power Control - Max. UE Tx power: 24 dBm (-6 dB)
P r o b a b i l i t y D e n s i t y F u n c t i o n
UE Transmit Power (dB)
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Primary
SCHSecondarySCH
2560 chips
cp cp cp
Slot #0 Slot #1 Slot #14
(Tx OFF)
256 chip
P-CCPCH (18 bit, SF = 256)
Time Slot (2560 chip, 0,667 ms)
frame (10 ms)
Slot #iSlot #0 Slot #1 Slot #14
Trama (10 ms)
cs(i,0) cs(i,1) cs(i,j) cs(i,14)
Synchronization channels structure
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Synchronization channels characteristics Primary SCH: is a modulated sequence 256 chip long, unique for each
cell, used to acquire slot synchronization
A matched filter with sliding window is used
Matchedfilter
Identifies thecorrelation
peck and
distributes the
timing
Baseband (Rc
chip/s) P-SCH sequence
Secondary SCH: is a sequence of 15 words (1 per Time Slot) of 256 chip,
taken from a family of 16 known words
16 correlators are used and a sequence of 15 words identifies:
1. The group of 8 primary scrambling codes (64 possible), to which theprimary code of the cell belongs
2. The Time Slot (index from 0 to 14), to acquire frame and Time Slot
synchronism
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Frame and slot synchronism acquisition1. The UE searches the primary synchronization code of 256 chips, sent on the
primary SCH, through a matched filter; a peak at the output indicates slot
synchronization
2. The secondary code Csi,j indicates both the group of 8 primary scrambling codes
(index i, with value from 0 and 0 e 63) to which the primary cell code belongs,
both the Time Slot (index j from 0 and 14). The secondary codewords are only 16
and their particular sequence (known from the correlation) indicates group and
slot
3. A third correlation process with the CPICH allows the primary scrambling code
identification among the 8 indicated Csi,j and to decode the P-CCPCH
Primary
SCHSecondarySCH
2560 chips
cp cp cp
Slot #0 Slot #1 Slot #14
frame (10 ms)
cs(i,0) cs(i,1) cs(i,j) cs(i,14)
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Network Access Procedure
Contention access, with collisions In Uplink the PRACH channel is used, with preambles at increasing
power and a final part, the message
Only PRACH message brings signaling or data
The message is transmitted only if the preamble is acknowledged from
the downlink channel AICH ( Acquisition Indicator Channel)
For preambles and AICH, the time is divided into Access Slot:
The Access Slot are grouped into 12 non overlapping ensembles, out of phased of an integer number of frames (SFN, System Frame Number )
The mobile randomly selects one of the available ensembles, and an
Access Slot in it
The preamble is a sequence of 4096 chip, that the mobile randomly
selects in 16 possible sequences (signature).
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Access Procedure - Evolution
t
Reception at UE side
t
Transmission at UE side
1° Pre-amble
Access Slot AICH(2 Time Slot, 5120 chip)
Access Slot RACH(2 Time Slot, 5120 chip)
4096 chip
2° Pre-
amble
AICH
Message
PRACH
10 o 20 ms
TP-P (3 o 4 Access Slot) TP-M (3 o 4 Access Slot)
TP-A (3 o 4 Time Slot)
4096 chip
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UMTS security
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Network Access Security - Network Domain Security
RNC
RNCNode B
Node B
Node B
Node B
UTRAN
Iu
Iur
Iub3GMSC
VLR
HLR
SGSN GGSN
Iu CS
Iu PS Gn
Gs
3GGMSC
Gr Gc
Network Access Security Network Domain Security
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2G Security brainstorming
Main 2G Security features
• User identity confidentiality (IMSI TMSI)
• 2G AKA procedure
• Ciphering
Due to the closed nature of SS7 networks, 2G does not expect
Network Domain Security features.
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2G Security brainstorming2G AKA procedure AuC/HLR
(triplets generation)
RANDKiKi
A3 A8
RAND SRES Kc
Kc (to the BTS, CS only)
Visited VLR/SGSN
RAND SRES Kc
=??
Y
S u c c e s
s ! !Kc (to the MS)
SRESuser
RANDKiKi
A3A8
Kc
SIM card
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2G Security brainstorming -Ciphering
“Ciphered text”
Frame
number
(22bits)
Kc
(64bits)
A5/GEA
“Clear text”
Frame
number
(22bits)
Kc
(64bits)
A5/GEA
“Clear text”
MS BTS (CS) / SGSN (PS)
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3G Security (Rel-99)Main 3G Security features
• User identity confidentiality (IMSI TMSI)
• Confidentiality
• Data integrity
• 3G AKA procedure
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3G Security (Rel-99) -
User identity confidentiality
• IMSI confidentiality
• User Location confidentiality
• User untraceability
TMSI/P-TMSI allocation/re-allocation + Ciphering
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N E W ! !
N E W ! !
3G Security (Rel-99) -3G AKA procedure
• User authentication
• Network authentication
3G AKA procedure provides:
• Cipher key generation
• Integrity key generation
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3G Security (Rel-99) -3G AKA procedure
CK, IK (to the serving RNC)
Visited VLR/SGSN
S u c c e s s !
!
=??
Y
RAND XRES CK IK AUTN
X R E S
AuC/HLR
RAND, K,
SQN, AMF
A V s
g e n e r a t i o
n
RAND X RES CK IK AUTN
CK, IK (to the UE)
USIM
K
N e t w o r k
A u t h e n t i c
a t i o n
C K, I K, X R
E S u s e r
c a l c u l a t i o
n XRESuser
RAND, AUTN
168 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
3G Security (Rel-99) -3G AKA procedure
• As for 2G, the 3G AKA procedure is a “Challenge-Response”
mechanism.
• As for 2G, the corner stone of the whole security is a
Subscriber-specific 128bits-long secret key, named “K”. It is
securely stored on the USIM card and in the HPLMN (in the
AuC). Nobody can access the “K” key and it is never
transmitted, neither within the HPLMN.
• As for 2G, 3G AKA procedure is based on pre-calculated
Subscriber-specific authentication vectors (AVs).
• The main differences between 2G and 3G AKA procedures are
the “IK generation” and the “Network Authentication”
features.
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3G Security (Rel-99) -
3G AKA procedure AuC/HLR
AK
f1 f2 f3 f4 f5
R A N D
KSQN
AMF
IKMAC
AUTN
CKX R E S
RAND XRES CK IK AUTN
3G AVs generation.
INPUTs:
• K = Subscriber-specific secret key
(128 bits), stored in the AuC.
• RAND = random-like data (128 bits)
generated by the AuC.
• SQN = sequence number, generated
by the AuC.
• AMF = Authentication and key
Management Field.
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3G Security (Rel-99) -3G AKA procedure
AuC/HLR
AK
f1 f2 f3 f4 f5
R A N D
KSQN
AMF
IKMAC
AUTN
CKX R E S
RAND XRES CK IK AUTN
3G AVs generation.
OUTPUT: Subscriber-specific
Authentication Vectors (AVs or simply
“Quintets”).
• RAND = cfr. INPUTs
• XRES = Expected signed Response
(32-128 bits).
• CK = Ciphering Key (128 bits).
• IK = Integrity Key (128 bits).
• AUTN = Authentication Token (it
allows the Network Authentication).
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3G Security (Rel-99) -3G AKA procedure
AuC/HLR
AK
f1 f2 f3 f4 f5
R A N D
KSQN
AMF
IKMAC
AUTN
CKX R E S
RAND XRES CK IK AUTN
3G AVs generation.
• f1 = 4-inputs message authentication
function.
• f2 = 2-inputs message authentication
function. It is the “equivalent” of
the 2G “A3” algorithm).
• f3, f4, f5 = 2-inputs key generation
functions. f3 is the “equivalent” of
the 2G “A8” algorithm.
Note: f1, …, f5 are Operator-specificone-way functions, securely stored
on the USIM and in the AuC.
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USIM
AK
f4 f3 f2
f5SQN
K MACAMFSQN xor AK AUTN, RAND
from VLR/SGSN
f1
RAND
XMAC =??
MA C
IK (to the UE)
Y S U C C E S
S F U L
N e t w o
r k
A u t h
e n t i c a
t i o n
CK (to the UE)
AUTN
RES (to VLR/SGSN)
3G Security (Rel-99) -3G AKA procedure
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3G Security (Rel-99) -
Confidentiality
• Cipher algorithm agreement
• Cipher key agreement
• Confidentiality of user/signalling data
The following features are provided:
Security mode negotiation mechanism + 3G AKA procedure
+ Ciphering over radio access interface.
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3G Security (Rel-99) -Confidentiality
• 3G ciphering is based on the same principle of the 2G
one (stream cipher concept).
• It occurs between UE and RNC, where “f8” is located.
• 2G “A5” 3G “f8”.
Main aspects:
• As “A5”, in order to allow roaming, “f8” is “standard”.
• Kc (64bits) CK (128bits).
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3G Security (Rel-99) -
Data integrity
• Integrity algorithm agreement
• Integrity key agreement
• Data integrity and origin authentication of signalling data
The following features are provided:
Security mode negotiation mechanism + 3G AKA procedure
+ Integrity over radio access interface.
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3G Security (Rel-99) -Data integrity
• Data integrity provides individual control message.
• It occurs between UE and RNC, where “f9” is located.
Main aspects:
• Similarly to “f8” , in order to allow roaming, “f9” has to
be “standard”.
• It is based on the “traditional” MAC concept, by using the
128bits-long IK, generated by the 3G AKA procedure.
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2G-3G Security interoperability
R e l e as e 9 9 + V L R / S G S N Release 98-
V L R / S G S N
R e l e a s e 9 9 +
H L R / A u C
U S I M
R A N D
A U T N
R E S
C KIK
C K , I KK c
U T R A N
R 9 9 + M E c a p a b le o f
U M T S A K A
R A N D
A U T N
R E S
[ K c ]
C K , I KK c
G S M B S S
C K , I K K c
R E S S R E S
C K , I K K c
R 9 9 + M E n o tc a p a b l e o f U M T S
A K A
o r R 9 8 - M E
C K , I K K c
C K , I K K c
R E S S R E S
R A N D
[ A U T N ]
S R E S
[ K c ]
K c
R A N DS R E S
[ K c ]
K c
M E
C K , I K K c
R E S S R E S
Q u in tet s T riple t s
C K , I K K c
R E S S R E S
U M T S secu r ity c on te x t G SM secu r ity con tex t
C K , I K K c
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UMTS OVERVIEW Maria Stella Iacobucci
The UMTS evolution: HSDPA
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What is HSDPA?
HSDPA is a whole of radio functionalities for
Optimization of asymmetric packet transmission
(Streaming, interactive, FTP/e-mail)
Intermittent transmissions handling with high peak bit
rate
Increase of UMTS spectral efficiency
Lower latency
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HSDPA positioning
100 m 1000 m 10 km
100 kbit/s
1 Mbit/s
10 Mbit/s
U MT S R e le as e 9 9
H S D P A ( U M T S R e l e a s e 5 )
WLAN (802.11b)
EDGE
GPRS
Transmission
speed
Cell radius
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HSDPA innovations
Intoduction of a transmission channel shared among different
users for the downlink
Scheduling of the transmission queues demanded to the base
station: the MAC level has been decentralized
Multiplation on the time domain using subframes (TTI) of 2ms
Hybrid ARQ techniques for corrupted radio blocks handled from
the node B
Adaptive modulation and coding
Use of QAM modulation to increase spectral efficiency
Peak speed up to 14 Mb/s
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16-QAM modulationAverage power equal to
peak power
Non constant
envelop
QPSK: 4 symbols, 2 bit per symbol 16 QAM: 16 symbols, 4 bit per symbol
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Intermittent service handling in R99
Data on DCH Tinact (1 -3 s)
Signaling onFACH
Source inactivity (empty transmission buffers)
Source activity
Tact (1 -3 s)
Synchronization
Data on DCH
t
DPCCH (control channel)
DCH release
DPCCH
Transition on common channels
Transition on dedicated channels
The DL code is busy even in inactive intervals (at least DPCCH is
sent)
Code allocation and code deallocation handled by timers: the
units are one or more frames Synchronization need
Scarce efficiency for intermittent services
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HSDPA:
Code and Time multiplexing
The idea of the HSDPA is to allocate resources for lower time
intervals
A new transport channel named HS-DSCH (High Speed Downlink
Shared Channel) is used On the HS-DSCH the TTI is reduced to 2 ms (3 Time Slot), even
if the frame organization is the same
Different users can be multiplexed on adjacent TTI of the same
frame
HS-DSCH
user 1HS-DSCH
user 2HS-DSCH 1
Utente1
time
c o d e s
time
DCH – user 3
DCH - user 4
HS-DSCH 1
Utente 2
HS-DSCH 2
Utente1HS-DSCH 2
Utente 3
DCH - user 5
C o d i c iDedicated channels:
Users multiplexed only oncode basis
Shared channels: users
Multiplexd on code
and time basis
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HS-DSCH assignment and release
For Power Control and signalling, each user uses a DL associated dedicated
channel at low bit rate (i.e. 3,4 kbit/s and SF 256)
The scheduling information is carried on a shared control channel, the HS-SCCH
(High Speed Shared Control Channel).
DCH at low bit rate, mobile 1
time
DCH at low bit rate, mobile 2
data on HS-DSCH
(mobile 1)signallingonHS-SCCH
signallingonHS-SCCH
Data on HS-DSCH
(mobile 2)
signallingonHS-SCCH
signallingonHS-SCCH
Dati on HS-DSCH
(mobile 1)
Data onHS-DSCH
(mobile 1)
1 TTI 1 TTI
1 frame
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Physical channel HS-PDSCH
Spreading factor equal to 16
Up to 15 codes to the same user in the same TTI
In each TTI only one Transport Block is sent
subframe HS-DSCH (2 ms)
Slot #0 Slot #1 Slot #2
HS Physical DSCH , Tslot = 0,667 ms
Ndata bit (2560chip , 320/640*bit, SF = 16)
* 320 bit if QPSK, 640 if 16QAM
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DCH and HS-DSCH differences
Prestazione DCH Downlink HS-DSCH
Variable Spreading Factor yes (4÷ 256) No (16)
Closed loop power control yes No
modulation QPSK QPSK e 16-QAM
Modulation and adaptive coding No yes
H-ARQ - No yes
Multicode modality No yes ÷
TTI duration minimum 10 ms 2 ms
Soft Handover yes No
Maximum Bit Rate 384 kbit/s 1÷14 Mbit/s
RNC Nodo BScheduler
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New channels in HSDPA
Scheduling information is carried in a shared control channel, the
HS-SCCH
It is possible to transmit up to 4 users in the same TTI on groups
of codes with SF 16
One HS-SCCH can address one user
In Uplink, the radio block Ack/Nack is carried on a physical
control channel, the HS-DPCCH
Even for the HS-DPCCH a structure with three time slots is used:
the first for Ack/Nack, in the other two the CQI
In Uplink, traffic and signaling are carried on a dedicated
associated channel corresponding to R99 (i.e. 64 kbit/s payload +
3,4 kbit/s for signaling).
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Transmission
∼19200 chip (5ms)
HS-DSCH
Reception at UE
time
Transmission at UE HS-DPCCH
Reception at Node B
Block 1
Block 2
Block 3
Block 4
Block 5 Block 6 Block 1
Block 7
TTI (3 TimeSlot, 2 ms)
Elaboration
∆TNACK ACK ACK ACKACKCQI CQI CQI CQI CQI
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UMTS OVERVIEW Maria Stella Iacobucci
Temporal relationship among DL channels
PCCPCHReception at the UE
1 frame = 15 Time Slot = 10 ms
HS-SCCH
1 TTI = 3 Time Slot = 2 ms
HS-DSCH
1 TTI = 3 Time Slot = 2 ms
2 Time Slot = 1,33 ms
Part 1: MS,CCS, UE ID
Part 2: TBS,HARQ, UE ID
Each HS-SCCH (up to 4) uses a code with SF 128 and is organized in subframes of
2 ms (3 Time Slot) In part1 (1 TS) the information necessary to demodulate the HS-DSCH is sent:
modulation (MS), MAC UE identifier, number and position of used OVSF (CCS,
Channelization Code Set)
Part 2, overlapping to the HS-DSCH, allows the decoding: HARQ informations and
block dimentions (TBS)
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HSDPA Channels
HS-DPCCH is sent on the UL Dual-BPSKmodulator, together with the
dedicated associated DPCCH
The table has been taken on RAB HSDPA proposed in 3GPP.
Downlink SF codes Net Bit Rate [kbit/s]
HS-DSCH 16 1 ÷ 15 900 ÷ 14400 ( payload )
DCH - 256 1 3,4 (signaling)
HS-SCCH 128 1 ÷ 4 - (control channels forscheduling)
Uplink SF codes Net Bit Rate [kbit/s]
DCH - 8 ÷16 1 64 ÷ 128 ( payload ) + 3,4(signaling)
HS-DPCCH 256 1 - (Ack/Nack and CQI)
(associated to HS-DSCH)
(associated to HS-DSCH)
192 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Hybrid ARQ and Incremental RedundancyRadio block
Coded block (Rate 1/3)
1st transmission (Self Decodable)
ritransmission(Non-self Decodable)
Coder Rate 1/3
puncturing
Node B
Mobile Terminal
Failed decoding
NACK
Combination anddecoding OK
ACK
X
X
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Fast Scheduling and CQI
Nodo B
Mobile 1
Mobile 2
C Q I : g o
o d c h
a n n e l q
u a l i t y C
Q I : s c a r c e c h a n n e l q u a l i t y
Decision on scheduling e AMC*
CQI is a metric calculated each 2 ms basing on the pilot channel, and indicates
the transmission format (power, modulation, coding scheme) that the mobilecan receive in the subsequent TTI with Block Error Rate (BLER) lower than 10%
* Adaptive Modulation & Coding
194 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Example: CQI and transmission formats CQI is a 5 bit information word (32 values)
The correspondence among CQI values and transmission formats is
different for each class of MTs; follows the case of class 10 UE
CQI
(0 ÷ ÷÷ ÷ 31)
modulation Transport Block [bit]
Coding Rate Number of codes
4 QPSK 317 1/3 1
6 QPSK 461 1/2 1
9 QPSK 931 1/2 2
11 QPSK 1483 1/2 4
13 QPSK 2279 1/2 5
15 QPSK 3319 ∼0,7 5
16 16-QAM 3565 ∼0,4 5
18 16-QAM 4664 1/2 5
25 16-QAM 14411 3/4 10
30 16-QAM 25558 ∼0,9 15
i.
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Orthogonal codes : coexistence with R99
In each cell where HSDPA is active, it is necessary to keep:
From 1 to 15 codes with SF 16 for HS-PDSCH channels
From 1 to 4 codes with SF 128 for HS-SCCH
Many codes with SF 256 associated to the dedicated channels per each
HSDPA session
A portion of the transmission power for HS-PDSCH e HS-SCCH
The coexistence HSDPA and R99 services on the same carrier must
provide dinamic mechanisms for resource allocation to HSDPA
A basic configuration to verify the coexistence is:
5 codes with SF 16 for HS-PDSCH, and 1 for HS-SCCH
20-30% of the allocated power to HSDPA.
196 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
OVSF codes assignment (CCS field of the HS-SCCH)
SF = 32 SF = 64 SF = 128
C64,0
C64,1
C32,0
C128,0
C128,1
C 128,2
C128,3
SF = 256
C16,0
C16,1
C32,1
C16,14
C16,15
SF = 16 SF = 32 SF = 64 SF = 128
C64,0
C64,1
C32,0
C128,0
C128,1
C 128,2
C128,3
SF = 256
C16,0
C16,1
C32,1
C16,14
C16,15
SF = 16
Group of codesposition forHS-DSCH -(Starting Node )
15 codes
Blocked code for
Signallingchannels
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Transmission formats
Transmission formats are defined on the basis of:1) The number of codes assigned in the TTI for the HS-PDSCH
2) the modulation, QPSK or 16-QAM
3) The radio block dimension, which can assume 64 values per each
combination of codes and modulation
The number of transmission formats is
2 modulations x 15 codes x 64 block dimensions = 1920
The code rates different from 1/3 (or 1/2) are obtained with
puncturing
with 15 codes, 16-QAM modulation and lower error protection, the
peak bit rate is 14 Mbit/s
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UMTS OVERVIEW Maria Stella Iacobucci
Transmission formats
0,25 0,50 0,75 1,00
0,1
1
10
V e l o
c i t à d i T r a s m i s s i o n e [ M b i t / s ]
Rate di Codifica
1 Codice
2 Codici5 Codici
10 Codici
15 CodiciQPSK
16-QAM
0,25 0,50 0,75 1,00
0,1
1
10
V e l o
c i t à d i T r a s m i s s i o n e [ M b i t / s ]
Rate di Codifica
1 Codice
2 Codici5 Codici
10 Codici
15 Codici
0,25 0,50 0,75 1,00
0,1
1
10
V e l o
c i t à d i T r a s m i s s i o n e [ M b i t / s ]
Rate di Codifica
1 Codice
2 Codici5 Codici
10 Codici
15 Codici
0,25 0,50 0,75 1,00
0,1
1
10
V e l o
c i t à d i T r a s m i s s i o n e [ M b i t / s ]
Rate di Codifica
1 Codice
2 Codici5 Codici
10 Codici
15 CodiciQPSK
16-QAM
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Example of transmission formats
Modulation Transport block dimension
Block [bit]
TTI [ms] Coding
Rate
Bit Rate [Mbit/s] Number of codes
QPSK (R99) 3840 (12 blocchi di 320 bit) 10 1/3 0,384 1 (SF=8)
QPSK (R99) 20480 (32 blocchi di 640 bit) 10 1/3 2 3 (SF=4)
QPSK 317 2 1/3 0,16 1 (SF=16)
QPSK 461 2 1/2 0,23 1 (SF=16)
QPSK 931 2 1/2 0,46 2 (SF=16)
QPSK 1483 2 1/2 0,74 4 (SF=16)
QPSK 2279 2 1/2 1,14 5 (SF=16)
QPSK 3319 2 ∼0,7 1,65 5 (SF=16)
16-QAM 3565 2 ∼0,4 1,8 5 (SF=16)
16-QAM 4664 2 1/2 2,3 5 (SF=16)
16-QAM 7168 2 3/4 3,6 5 (SF=16)
16-QAM 11418 2 3/4 5,7 8 (SF=16)
16-QAM 14411 2 3/4 7,2 10 (SF=16)
16-QAM 17237 2 3/4 8,6 12 (SF=16)
16-QAM 21754 2 3/4 10,9 15 (SF=16)
16-QAM 25558 2 ∼0,9 12,8 15 (SF=16)
16-QAM 28776 2 1 14,4 15 (SF=16)
i.
200 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
Classes of terminals
The classes of terminals are defined basing on:
1) The number of codes that can be elaborated per each TTI
2) The maximum sustained bit rate, calculated on the whole
frame
3) The minimum interval between two subsequent TTI,
expressed in TTI
4) Handled modulations (only QPSK, or QPSK and 16-QAM)
3) Dimension of memory for HARQ
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HSDPA – mobility handling
The mobile can stay in Cell_DCH state, applying Soft Handover
at the associated DCH
NodoBNodoB
Cell 1NodoBNodoB
Cell 2
HS-DSCH
DCH associatedDCH associated
Radio connections at instat T
202 Rio De Janeiro October 2006
UMTS OVERVIEW Maria Stella Iacobucci
HSDPA – mobility handling
The mobility procedure that transfers the connection on the HS-DSCH to the target cell iscalled Serving HS-DSCH Cell Change
It is activated from the RNC on the basis of terminal measurements
NodoBNodoB
Cella 1NodoBNodoB
Cella 2
HS-DSCHDCH Associato
DCH Associato
Radio connections at instant T+T 0
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HSDPA – Network impact
Adaptive resource allocation algorithms for HSDPA
HW on Node B: new baseband elaboration to handle new coding
schemes and modulation (Channel Card, RAXB e TXB)
HW on RNC: new radio protocols elaboration algorithms and Iub
interface
Amplifiers: necessary a back-off of 1,5-2 dB for 16-QAM
New capacity on Iub, Iu
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