3g wireless systems: umtswireless.ictp.it/school_2002/lectures/telit/html/ictp_umts.pdf3g wireless...
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TELIT GROUP Industries for Telecommunications 1
20th February 2002
3G wireless systems: UMTSSCHOOL ON DIGITAL
AND MULTIMEDIA
COMMUNICATIONS
USING TERRESTRIAL
AND SATELLITE
RADIO LINKS
TELIT MOBILE TERMINALS
Ing. PhD. Alberto CerdeiraTelit Mobile Terminals S.p.A.R&D IC Hardware Designv.le Stazione di Prosecco 5/B34010 - [email protected]
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ICTP - Miramare
• Why 3rd generation ?• Frequency Bands• Standartization of 3G Projects• CDMA Technology Review• UMTS Channels• UMTS Synchronization• UMTS Architecture
OUTLINE
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ICTP - MiramareNew services require high data rate capability
e-mail web photo report videoclipGSM Ph.1
e-mail web photo report videoclipPSTN
web photoe-mail report videoclipISDN
web photo report videoclipGSM 2+
photo report videoclipUMTS
10sec 1 min 10 min 1 hour
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ICTP - MiramareUMTS Service aspects and Service Capabilities
• Radio operating environments– indoor– outdoor to indoor and pedestrian– vehicular and fixed outdoor– (satellite)
• Data rates– up to at least 144 kbps in vehicular environment with full
mobility– up to at least 384 kbps in suburban outdoor and outdoor to
indoor environments with medium mobility– up to 2 Mbps with low mobility in pico cells and indoor
• Packet and circuit oriented, symmetric and asymmetric services
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ICTP - MiramareNew services require high data rate capability
Cellular phonestowards
Smart platforms
Personal DigitalAssistantget mobile
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ICTP - Miramare
1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180
35 MHz of unpaired spectrum
2*60=120 MHz of paired spectrum
Spectrum Allocation in Europe
Need for Speed = Wide Band System•The spectrum availability is a key factor for the success of 3rd
generation systems•UMTS Forum estimated a minimum need for a 3rd generationoperator of–2x15 MHz of paired spectrum–5 MHz of unpaired spectrum(supposing 1 UMTS carrier occupies a 5 MHz slot)
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ICTP - MiramareWorldwide Frequency Bands
2X30 MHz in S-Band allocated toMSS, adjacent tospectrumallocation forterrestrial systems
ERC (European Radiocommunications Committee) assignments to MSS:– 2 x 30 MHz (1980 - 2010 MHz and 2170 - 2200 MHz)– 15 MHz available from 2000 (1995 - 2010 MHz and 2185 - 2200 MHz)– 30 MHz available from 2005 (1980 - 2010 MHz and 2170 - 2200 MHz)– 15 MHz assigned TDMA systems (S-PCS) (1995 - 2010 MHz and 2185 -2200 MHz)
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ICTP - MiramareWireless Evolution through the Generations series
1G
2G
3G
Analogue voice (AMPS- AdvancedMobile Phone Standard, TACS-TotalAccess Communications System,... )
Digital voice, low datarate applications [GSM,IS-54 (TDMA), IS-95(CDMA), GLOBALSTAR,IRIDIUM…]
UMTS/IMT 2000 GlobalStandard for wirelessmultimedia
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ICTP - Miramare
Project Co-ordination Group
Technical Specification Groups
Support functions
3GPP
IndividualMembers(e.g. Telit)
IMT-2000contributionsvia existingprocesses
Regulators/Governments
Partners (e.g. ETSI)
Technicalcontr.
Partners Standardisation ProcessPartner deliverable
TechnicalSpecifications
ITU International Recommendations
Standartization - 3GPP Group (www.3gpp.org)
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ICTP - MiramareStandartization - 3GPP Group (www.3gpp.org)
WG1Radio Layer 1
WG2Radio Layer 2 and
Layer 3 (RR)
WG3Iu and O&M
WG4Radio performance and proto-
-col aspects from a systempoint of view; BS conformance
TSGRadio Access Network
WG1MM/CC/SM (Iu)
WG2CAMEL/MAP
WG3Interworking withexternal networks
TSGCore Network
WG1Mobile terminal
conformancetesting
WG2Mobile terminal
Services &Capabilities
WG3USIM
TSGTerminals
WG1Services
WG2Architecture
WG3Security
WG4Codec
WG5Telecom
Management
TSGServices and System Aspects
Project coordination groupPCG
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ICTP - Miramare
– spreading & de-spreading– rake receiver– soft handoff– power control– synchronous versus asynchronous networks
CDMA – Technology review
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ICTP - Miramare
CDMA & spread spectrum• CDMA = Code Division Multiple Access• Spread spectrum is a characteristic of a signal; the
signal is not necessarily intended for a multipleaccess of a common medium (e.g. anti-jamming)
• Signals used in CDMA are usually spread spectrumsignals
• There are many types of spread spectrum, e.g.– Direct Sequence ⇐ this is the only one we consider here– Frequency hopping
CDMA – Technology review
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ICTP - Miramare
0 (SF-1)Tc
0 (SF-1)Tc
j Cqn(kTc)
Cin(kTc) Cin(kTc)
-j Cqn(kTc)
0-(SF-1)Tc
0-(SF-1)Tc
aI(mT)
aQ(mT)
T
T∝ 1/T
∝ 1/Tc
T = SF Tc
• Direct Sequence spread spectrum• Rake receiver exploits micro-diversity• Spreading sequences should be as much as possible
– orthogonal each other with arbitrary shifts– each one orthogonal to itself with arbitrary shifts
Spreading & de-spreadingCDMA – Technology review
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ICTP - MiramareCDMA – Technology review
Ortogonal Variable Spreading FactorCodes
Recursive rule
( )( )
1
2
2
(0) 1
(2 1) ( ), ( )( )
(2 ) ( ), ( )N N N
NN N N
C
C i C i C iC i
C i C i C i
=
− =→ = −
1
11
1-1
1111
11-1-1
1-1-11
1-11-1
C1(1)
C2(1)
C2(2)
C4(1)
C4(2)
C4(3)
C4(4)
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ICTP - MiramareCDMA – Technology review
decoder
11-1-1
1-1-11
1-11-1 -4 -4 4
-4 4 -4
4 4 -4
001
010
110
decoder
decoder
-1-1-13 11-31 -1-13-1
-1-1-13 11-31 -1-13-1
-1-1-13 11-31 -1-13-1
-1 -1 -1 3 1 1 -3 1 -1 -1 3 -1
001 encoder1-11-1
-11-11 -11-11 1-11-1
010 encoder11-1-1
-1-111 11-1-1 -1-111
110 encoder1-1-11
1-1-11 1-1-11 -111-1 -1 -1 -1 3 1 1 -3 1 -1 -1 3 -1
Spreading
De-Spreading
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ICTP - MiramareCDMA – Technology review
1-1-1 1 1-1-1 1 1-1-1 1 1-1-1 1 1-1-1 1 Code1
Data1
-1 1 1-1 1-1-1 1-1 1 1-1 0 0 0 0 1-1-1 1 Data1*Code1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Code2
Data2
1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 Data2*Code2
0 2 2 0 2 0 0 2 0 2 1-1 0 0 1 1 2 0-1 1 Received data (somma dei canali)
0-2-2 0 2 0 0 2 0-2-1-1 0 0-1 1 2 0 1 1 Rx*Code1
Data despreaded
0 2 2 0 2 0 0 2 0 2 1-1 0 0 1 1 2 0-1 1 RX*Code2
Data despreaded
1 0
1 1 1 1 1 0 0 1
1 0 0 1
11 -1 0
1 1
-1
-1
1 1
1 -1 0 1
1 0
Canale 2
Canale 1
Created by Luca Marcato
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ICTP - MiramareCDMA – Technology review
Soft handoff (hand-over)
• The two Base Stations use different scrambling codes• Soft handoff exploits macro-diversity• Softer handoff: between two sector of the same BS• Active Set: set of BS connected to a mobile• Candidate Set: set of BS whose signals has been
detected by the mobile but not currently connected
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ICTP - MiramareCDMA – Technology review
Rake receiver
0 (SF-1)Tc
0 (SF-1)Tc
j Cqn(kTc)
Cin(kTc) Cin(kTc)
Cqn(kTc)
0-(SF-1)Tc
0-(SF-1)Tc
aI(mT)
aQ(mT)
T
0 δTc
αβ
T
Cin(kTc- δTc)
Cqn(kTc- δTc)
-δTc-(SF-1)Tc- δTc
T
T-δTc-(SF-1)Tc- δTc
α*
β*
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ICTP - MiramareCDMA – Technology review
Rake receiver in soft handoffCin(kTc)
Cqn(kTc)
0-(SF-1)Tc
0-(SF-1)Tc
T
T
C’in(kTc- δTc)
C’qn(kTc- δTc)
-δTc-(SF-1)Tc- δTc
T
T-δTc-(SF-1)Tc- δTc
α*
β*
0 (SF-1)Tc
0 (SF-1)Tc
j Cqn(kTc)
Cin(kTc)
aI(mT)
aQ(mT) 0
α
0 (SF-1)Tc
0 (SF-1)Tc
j C’qn(kTc)
C’in(kTc)
aI(mT)
aQ(mT)0 δTc
β
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ICTP - MiramareCDMA – Technology review
Why power control ?• A “strong” user can cover a “weak”one (because codes are not strictlyorthogonal): near far effect• Since we want a fair system thenetwork command the mobiles to adjusttheir power in order to have their signalsto arrive with (almost) equal quality(minimise the interference at the basestation)• Power control is critical for CDMAsystems• If we can separate users in some way(e.g. TDD and Multi User Detection)power control become less critical
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ICTP - MiramareCDMA – Technology review
Power control &soft handoff
• Power control minimise intra-cellinterference
• Inter-cell interference minimisation isachieved through soft handoff and carefulselection of the BS involved in it
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ICTP - MiramareCDMA – Technology review
Codes planning• Different Base Stations must have
different scrambling codes– e.g. to permit to the mobile to distinguish
between signals coming from different BS• “Different” scrambling codes
– “completely” different scrambling codes– scrambling codes made by shifting a unique
mother code
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ICTP - MiramareCDMA – Technology review
Synchronous & asynchronous networks• Synchronous network: all BS are tightly
synchronised (e.g. through GPS)• Asynchronous network: BS are not supposed to
be synchronised• In synchronous networks we can use a set o
scrambling codes made from shifts of a uniquemother code
UMTS is an asynchronous system
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ICTP - MiramareUMTS – Channels
Logical, Transport andPhysical channels
• Logical channel: an information streamdedicated to the transfer of a specific type ofinformation
• Transport channel: described by how data aretransferred
• Physical channel: defined by the frequency,phase (I,Q) and code
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ICTP - Miramare
Logical channels• Control channels (C-plane information)
– Synchronisation Control CHannel (DL)– Broadcast Control CHannel (DL)– Paging Control CHannel (DL)– Common Control CHannel (UL&DL)– Dedicated Control CHannel (UL&DL)– Shared Control CHannel– ODMA Dedicated Control CHannel
UMTS – Channels
• Traffic channels (U-plane information)– Dedicated Traffic CHannel (DL&UL)– ODMA Dedicated Traffic CHannel– Common Traffic CHannel
• Others channels...
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ICTP - MiramareUMTS – Syncronization
Primary and Secondary Syncronization Channels (PSCH, SSCH)
Common Pilot Syncronization Channels (CPICH)
All zeros
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips , 20 bits = 10 symbols
1 radio frame: Tf = 10 ms
256 chips Pattern
Pre-defined symbol sequence
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips , 20 bits = 10 symbols
1 radio frame: Tf = 10 ms
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ICTP - MiramareUMTS – Synchronization
• PSCH is constant over a slot and identify the UMTS cell, slotperiodicity. (slot synchronization)
• SSCH is constant over a frame, each of 15 slot has its own symbolfrom 16 possible ones and identify the code group to use. (framesynchronization)
• CPICH has frame periodicity. Identify the sub-code from where toget the final code to use with other channels.
P-SCHS-SCH
CPICHother channels
P-SCHS-SCH
CPICHother channels
2560 2562560 0 2560
P-SCHS-SCH
CPICH
2560 chips
other channels
2560
Slot 1 Slot 2 Slot 15...
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ICTP - Miramare
Down-link spreading and modulation:all channels but SCH
I
Any downlinkphysical channelexcept SCH
S→P
Cch,SF,m
j
Sdl,n
Q
I+jQ S
UMTS – Syncronization
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ICTP - MiramareUMTS – Hardware Function Extentions
The asynchronous characteristic in UMTS system needsa more complex synchronization procedure.
The complexity in its realization is due to the bigamount of CPU and/or DSP time need to complete thesynchronization between the mobile and the antenna.The solutions are the use of a powerful embeddedsystem, but it may cost in power consumption, or therealization of an external, to CPU, hardware acceleratorblock that realize the desired function only when it isnecessary, in real time. In this paper we present a fullhardware block done in a FPGA for UMTS-FDD initialsynchronization procedure.
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ICTP - MiramareUMTS Terminal : envisaged architecture
A digital predistortionin the TX path isenvisaged, performedby the loop “DSP-Upconversion path-Antenna set-Feedback”. The samefeedback line, shown infigure, is used toperform a dinamicadjustment, toimprove the linearityof the receivingsection.
The Control Processormanages the exchange ofdata/addressinginformation between theDSP and the ASIC
The core of the system is the DSP, responsible of most of the basebandprocessing; the support of dedicated FPGAs or ASICs for particular heavycomputational operations like rake-decoding/Interference mitigation can benecessary depending on DSP computational power. In this last case, adedicated bus between the DSP and the ASIC could also be needed, orthe ASIC should directly communicate with the AD/DA converters andthen with the DSP.
FPGA
ASIC