06_gsm-umts
TRANSCRIPT
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Prof. Dr. Claudia Linnhoff-Popien
Moritz Kessel, Kevin Wiesner
http://www.mobile.ifi.lmu.de
Wintersemester 2010/2011
Praktikum Mobile und Verteilte Systeme
GSM & UMTS - Introduction
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM & UMTS - Introduction
Today:
• GSM – Global System for Mobile Communication
– System architecture
– Addressing and location management
– Air interface
• UMTS – Universal Mobile Telecommunications System
– System architecture
– Air interface
Next week:
•
Mario Jaritz: Mobilfunk in der Praxis
Note:
Some slides originate from the lecture Mobile Communications.
By courtesy of Axel Küpper
2
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
Evolution Path: From GSM to LTE
3
GSM speech
Short Message
Service (SMS)
Data services
(circuit switched)
2G
General Packet Radio
Service (GPRS)
Multimedia Messaging
Services (MMS)Wireless Application
Protocol (WAP)
High-Speed Circuit
Switched Data
(HSCSD)
Location-based
Services (LBS)
Enhanced Data Rates
for GSM Evolution
(EDGE)
Global System for
Mobile Communications
(GSM)
High-Speed
Downlink/Uplink
Packet Access
(HSDPA/HSUPA)
Long Term Evolution
(LTE)
Universal Mobile
Telecommunications
System (UMTS)
Streaming (Audio/
Video)
Video Telephony Mobile Internet
Push Email
Push-to-Talk
Over-Cellular
(PoC)
2.5G 3G 3.5G 4G
1990 2010
Network technologies/services
High-level services
Service functionalityData rate
Quality of transmission
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM
• 1982: Groupe Spécial Mobile established by Conférence Européenne des
Administrations des Postes et de Télécommunications (CEPT)• 1987: Elements of wireless transmission are specified based on prototype evaluation
• 1989: GSM becomes a Technical Committee of the new European TelecommunicationStandards Institute (ETSI)
• 1990: GSM 900 specifications are frozen. Adaption to DCS 1800 (Digital Cellular Systemat 1800 MHz) commences
• 1991: First GSM networks launched. DCS 1800 specification finalized and frozen
• 1993: First roaming agreements in operation. 32 networks in 18 countries areoperational
• 1994: Data transmission capabilities launched. 69 networks in 43 countries
• 1995: First PCS 1900 (Personal Communications System at 1900 MHz) network islaunched in the US
• Data and SMS roaming starts; Video transmitted by GSM for demonstration
•
1998: 320 GSM networks in 118 countries with 135 million subscribers worldwide• 1999: Wireless Application Protocol; 130 countries, 260 million subscribers
• 2000: 362 million subscribers; Introduction of General Packet Radio Service (GPRS)
• 2004: 1 billion subscribers; 200 countries
• 2007: 2 billion subscribers
4
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Architecture
AUC Authentication Center ISDN Integrated Services Digital Network
BSC Base Station Controller MSC Mobile Switching Center
BTS Base Transceiver Station OMC Operation and Maintenance Center
EIR Equipment Identity Register PSTN Public Switched Telephone Network
GGSN Gateway GPRS Support Node SGSN Serving GPRS Support Node
GMSC Gateway Mobile Switching Center SMSC Short Message Service Center
HLR Home Location Register VLR Visitor Location Register
5
BSC
BTS
BTS BSC
BTS
MSC
VLR
MSC
VLR
HLR EIR OMC
AUC GMSC
PSTN /
ISDN
SMSC GGSNInternet
SGSN
SGSN
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
Components – Mobile Station
Mobile Station (MS)
• Used by mobile service subscribers for
access to services, e.g., voice telephony,
SMS, or browsing the Internet
• Contains the mobile equipment (transceiver,
mechanisms for media access, coding, ...)
and the SIM
Subscriber Identity Module (SIM)
• Personalization of mobile stations
• Provides separation of personal from
terminal mobility (e.g., enabling international
roaming independent of mobile equipment
and network technology)
• Contains cryptographic algorithms to support
authentication and user data encryption
• Storage of charging information,SMS, and telephone book
• Protection with a PIN againstunauthorized access
• Network specific data (organizationof air interface)
• SIM Application Toolkit (SAT):execution environment for operator specific functions
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
Components – Base Station Subsystem
Base Station Subsystem (BSS)
• Consists of a Base Station Controller
and one or more Base Transceiver
Stations
Base Transceiver Station (BTS)
• Defines a single radio cell with a radius
of between 100m and 35 km
(depending on the environment)
• Each BTS is allocated a set of
frequencies (Cell Allocation, CA)
• Contains radio antenna, radio
transceiver, and link to a base station
controller
• Signal and protocol processing is
limited to error protection, encryption,
and link level signaling
Base Station Controller (BSC)
• Controls one or multiple BTS units
and hence multiple cells
• Performs essential control functions
and coordination between BTSs, e.g.
• Reservation of radio frequencies
• Management of handover from
one cell to another within the
same BSS
• Control of paging
• ...
BTS
BTS
BSC
BTS
BSC
BTS
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
Components – Switching Centers
Mobile Switching Center (MSC)
• Performs all switching functions of a
fixed-network switching node, e.g.
routing path search, signal routing,
service feature processing)
• Difference between conventional fixed
network switch and MSC: allocation
and administration of radio resourcesand mobility of subscribers (supports
location registration, handover
between different BSCs, ...)
• Support of service features like call
forwarding or conference calls
• Signaling between MSCs andbetween MSCs and other logical
entities by the Signal System No. 7
Gateway MSCs
• Passing of voice traffic between
fixed and mobile networks
• Required as access to GSM
network, because fixed network is
unable to connect an incoming call
to the local target MSC (due to its
inability to interrogate the HLR)
MSC
VLR
MSCVLR
HLR EIR OMC
AUC GMSC
PSTN /
ISDN
SMSC GGSNSGSN
SGSN
Internet
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
Components – Databases, Operation and Maintenance
Home Location Register (HLR)• Central database, stores permanent
and temporary information about eachof the subscribers associated with thenetwork
Visitor Location Register (VLR)•
Database containing distributednodes, each being responsible for acertain coverage area
• Contains information aboutsubscribers currently physicallystaying in the associated coveragearea
•
Usually combined with an MSC
Other components• SMS gateway
• WAP gateway
• ...
MSC
VLR
MSCVLR
HLR EIR OMC
AUC GMSC
PSTN /
ISDN
SMSC GGSNSGSN
SGSN
Internet
Components for Operation andMaintenance
• Operation and Maintenance Center
(OMC): controls and monitors all
network entities (traffic and status
reports, accounting and billing,...)
• Authentication Center (AuC):Protects user identity and data
transmission
• Equipment Identity Register (EIR):
Stores all device identification
registered for this network
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
Components – GPRS Infrastructure
• GSM was initially designed for circuit-
switched voice telephony• MSCs operating in circuit-switched
mode cannot be used for packet-switching
• Introduction of the packet-switchedGeneral Packet Radio Services(GPRS) for offering packet-switched
data services• Reuse of existing access networks
• Introduction of a new core network
Serving GPRS Support Node• Internet router with mobility support
•Counterpart of MSC
Gateway GPRS Support Node• Gateway to the public Internet
• Counterpart of GMSC
MSC
VLR
MSCVLR
HLR EIR OMC
AUC GMSC
PSTN /
ISDN
SMSC GGSNSGSN
SGSN
Internet
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Medium Access
• Combination of TDMA and FDMA
11
124
…
…
…
…
…
...1
124
…
……
…
…
2
1
960 MHz
959,8 MHz
935,2 MHz
935 MHz
915 MHz
914,8 MHz
890,2 MHz
890 MHz
200 KHz
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
3 Time slots delay
Data burst = 576,9 µs
Downlink
Uplink
Modulation: G(MSK)
Data rate: 270,83 kbps per physical channel
BTS
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Impact of Propagation Delay
12
Mobile
Station A
Downlink
Uplink
Base Station
Propagation
delay
Mobile
Station B
Round trip propagation delay BSMS B
Propagation
delay
1 21
2 Round trip propagation delay BSMS A
Downlink
Uplink
Downlink
Uplink
!!! Collision !!!
Problem: As the distance between a mobile and a base station usually varies, the
signal propagation delays between them also vary adjacent channel interference
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Guard Intervals
• Guard times between time slots avoid co-channel interference caused by
different propagation delays
• Example:
– Distance between MS and BS: 35 km
– Synchronization signal from BS arrives after
– Necessary guard time: 234 µs
Problem: guard times decrease capacity
234 µs guard time lowers capacity by 40 %!
Solution: Adaptive frame spacing
– Guard time can be reduced down to 30 µs
13
117μsm103
m10358
3
s
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Data Bursts
10 2 3 4 6 75
4,615 ms
Data DataTraining
sequence
57 5726
3 Tail bits 1 Signaling bit 1 Signaling bit 3 Tail bits
Burst (148 bits)
Time slot (156,25 bits)
0,577 ms
Guard
time
8,25
•
Each time slot of a TDMA frame lasts 0,577ms, which corresponds to the duration of
156.25 bit periods
• 156.25 bits are assigned according to a
well-defined structure known as a data
burst
•
GSM defines five different kinds of databursts used for different purposes:
• Normal burst (shown in this figure)
• Synchronization burst
• Frequency Correction Burst
• Access Burst
• Dummy Burst
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Dummy and Access Bursts
Dummy Burst
• Transmitted on one frequency of the cell allocation, when no other bursts are to be
transmitted
• Enables the mobile station to perform signal power measurements (quality
monitoring)
• Access Burst
• Initial signal sent by the mobile station
• Increased guard period is necessary as adaptive frame alignment could not have
been established yet
• Long guard duration of the guard period compensates propagation delay if a mobilestation sends an access burst from the boundary of a cell of 70 km diameter
326 bit training
sequence
3 8.25
336 data bits41 bit training
sequence8 68.25
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Physical Channels
16
GSM 900 GSM 1800
Frequencies Uplink: 890-915 MHzDownlink: 935-960 MHz
Uplink: 1710-1785 MHzDownlink: 1805-1880 MHz
# Carriers 124 374
# Duplex Channels 992 (Full rate)
1984 (Half rate)
2976 (Full rate)
5925 (Half rate)
Duplex distance 45 MHz 95 MHz
Max. BS power 320 W 20 W
Max MS power 8 W 1 W
Max MS velocity 250 Km/h 130 Km/h
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Logical Channels
MS BSSFull rate TCHTCH/F
MS BSSHalf rate TCHTCH/H
MS BSSStand-alone dedicated controlSDCCH
MS BSSSlow associated controlSACCH
MS BSSFast associated controlFACCH
MS BSSBroadcast controlBCCH
MS BSSFrequency correctionFCCH
MS BSSSynchronizationSCH
Access grant MS BSS AGCH
Paging MS BSSPCH
Notification MS BSSNCH
Random access MS BSSRACH
Traffic channel
(TCH)
Broadcast
channel
(BCH)
Common control
channel (CCCH)
Dedicated
control
channel (DCCH)
Traffic channel
(TCH)
Control
channel
(CH)
Group Channel Function Direction
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – System Hierarchy
GSM network consists of
at least oneadministrative region,
which is assigned to a
Mobile Switching Center
(MSC)
Administrative domain is
made up of at least one
location area (LA)
An LA consists of several
cell groups
A cell group is assigned
to Base Station
Controller (BSC)
For each LA there exists
at least one BSC, but
cells of one BSC may
belong to different LAs.
GSM network MSC region Location Area BSC Controller Cell
Cell
.....
BSC Controller
BSC Controller
BSC Controller
Location Area
BSC ControllerLocation Area
MSC region
MSC region
..........
.....
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Addressing and Location Management
• Permanent numbering
– Numbering of subscribers
• IMSI International Mobile Subscriber Identity
• MSISDN Mobile Subscriber ISDN
– Numbering of devices
• IMEI International Mobile Station Equipment Identity
• Temporal Numbering
• MSRN Mobile Station Roaming Number
• TMSI Temporary Mobile Subscriber Identity
• LAI Location Area Identifier
• CI Cell Identifier
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Permanent Subscriber Addresses
International Mobile Subscriber
Identity (IMSI)• Uniquely identifies the subscriber and is
stored in the SIM, HLR, and AuC
• Hierarchical addressing (example:
MCN=262 for Germany, MNC=01,02,03,07
for T-Mobile, Vodafone, Eplus, O2)
• Used, e.g., for billing
Mobile Subscriber ISDN Number
(MSISDN)
• Real telephone number of a subscriber
• Subscriber can have several MSISDNs, e.g.,
to distinguish several services (voice, data,
fax,...)
• Thus, automatic activation of service-
specific resources is already possible
during setup of connection
• Stored centrally in the HLR and in the SIM
Mobile Country
Code (MCC)
Mobile Network Code
(MNC)
Mobile Subscriber Identification Number
(MSIN)
Country Code
(CC), max. 3 places
National Destination Code
(NDC), max. 3 places
Subscriber Number
(MSIN), max. 10 places
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Temporary Subscriber Addresses
Mobile Station Roaming Number
(MSRN)• Temporary location-dependent ISDN
number
• Required to make routing decisions and toidentify the responsible MSC
• Assigned by the locally responsible VLR to
each mobile station in its area and passed tothe HLR
• Generated at each registration or when theHLR requests it for call setup (on a call-by-call basis)
VCC VNDC MSIN
Addresses the
responsible MSC
Addresses the
subscriber
Temporary Mobile Subscriber Identity
(TMSI)• Used in place of the IMSI for the definite
identification and addressing of the mobilestation
• Avoids to determine the identity of thesubscriber by listening to the radio channel
• Assigned during the mobile station’spresence in the area of one VLR (by that VLR)and can be changed during this period (IDhopping)
• Is stored by the mobile station on the SIMcard
• Is stored on the network side only in the VLR,
not in the HLR• Is assigned in an operator specific way and
consists of 4x8 Bits
• Subscriber can be uniquely identified; IMSI isreplaced by (TMSI, LAI)
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
GSM – Other Addresses
International Mobile Station Equipment
Identity (IMEI)• Uniquely identifies mobile stations
internationally
• Allocated by the manufacturer, registered by thenetwork operator and stored in the EIR
• Characterizes a mobile station and gives cluesabout the manufacturer and the date of
manufacturing
Location Area Identity (LAI)• Internationally unique identification of a location
area
• Regularly broadcasted by the base station
• “Heard” by the mobile station in order to decide
whether or not a new LA has been entered
Cell Identifier (CI)• Uniquely identification of cells within an LA
• Length of CI: 2x8 bits
• Internationally unique identification with theGlobal Cell Identity (LAI+CI)
Type Approval Code (TAC),centrally assigned
Finally Assembly Code (FAC),
assigned by the manufacturer
Serial Number (SNR),assigned by the man.
Spare (SP),
not used
Country Code (CC)
Mobile Network Code (MNC)
Location Area Code (LAC)
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
IMSI RAND SRES Ki Kc
IMEI
IMSI MSISDN MSRN
IMEI
IMSI, MSISDN, TMSI
MSRN IMSI TMSI MSISDN LAI
GSM – Overview of Addresses
BTS
CI, LAI
EIR
VLR
HLR
AUC
CI Cell IdentifierBSIC Base Transceiver Station Identity Code
LAI Location Area Identifier
IMSI International Mobile Subscriber Identity
MSISDN Mobile Subscriber ISDN Number
TMSI Temporary Mobile Subscriber Identity
MSRN Mobile Station Roaming Number
IMEI International Mobile Station Equipment Identity RAND Random Number
SRES Session Key
Ki Subscriber Authentication Key
Kc Cipher/Decipher Key
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
ISDN
GSM – Mobile Terminated Call
24
MSISDN Mobile subscriber ISDN number
CC Country code
NDC National destination code
MSRN Mobile station roaming number
TMSI Temporary mobile subscriber identity
HLR
MSC
BTS
BSC
MSC
SS7
HLR
BTS
VLR
VLRGMSC
4
1
MSRN
2
3
5
6
8
7
7
7
Forwarding to
responsible GMSC
(based on CC and
NDC of MSISDN)
Request and
delivery of routingaddress
Forwarding to
the local MSC
Request and
delivery of
TMSI for
paging
Paging request
Paging response
MSRN
MSISDN
TMSI
MSISDN
TMSI
TMSI
TMSI
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
UMTS – Release 99
25
BSCBTS
RNCNode B
MSCVLR
HLR EIR OMCAUC
GMSCPSTN /
ISDN
GGSNInternet
SGSN
AUC Authentication Center ISDN Integrated Services Digital Network
BSC Base Station Controller MSC Mobile Switching Center
BTS Base Transceiver Station PSTN Public Switched Telephone Network
EIR Equipment Identity Register RNC Radio Network Controller
GMSC Gateway Mobile Switching Center SGSN Serving GPRS Support Node
GGSN Gateway GPRS Support Node VLR Visitor Location Register
HLR Home Location Register
GSM/EDGE Radio Access Network
Universal Terrestrial
Access Network
(UTRAN)
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
UMTS – UTRAN-FDD
• Primarily used for speech transmission and forservices with data rates of up to 384 kbps in macroand micro cells
• A physical channel is defined by its carrierfrequency, a channelization code (OVSF), and therelative phase
• Frame structure with 15 slots for timing andsynchronization (no time multiplex)
• Variable data rates are achieved by varyingspreading factors
• Spreading factors: 1, 2, 4, ..., 256
• Depending on the number of physicalchannels used and their data rate, thenumber of available channelizationcodes varies
• The number of voice channels percarrier can be approximated to 250(256 available orthogonal codes, minussome control channels)
• Multicode and multirate users
5.0 MHz
Multicode users
Multirate user
1 frame = 10 msUTRAN-FDD mode:
Code
Frequency
Time
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
UMTS – UTRAN-TDD
• Primarily used for services with data rates of up to 2 Mbps in indoor/pico cells
• A physical channel is defined by its carrierfrequency, access code, and time slot
•
Frame structure with 15 slots for timemultiplex
• Multicode, multirate, and multislot users
• Two options for combined TDMA/CDMAoperation: multicode and single codetransmission
• Multicode with fixed spreading• Each user in a time slot gets assigned a
different spreading code and up to 8 different
codes can be allocated per time slot
• Spreading factor is fixed (=8)
• Single code with variable spreading• Each user gets one code but employs a
different spreading factor depending on the
required data rate
• Spreading factors: 1, 2, 4, 8 ,16
1 frame = 15 slots = 10 ms
5.0 MHz
Multicode user
Multirate user
Multislot user
Multislot/multicode user
UTRAN-TDD mode:
Code
Frequency
Time
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
UMTS – Principles of Wideband-CDMA
Principle of WCDMA
• All users are simultaneously transmitting in
the same frequency bands
• Each user interferes with each other
• Cluster size is 1, i.e., adjacent cells use the
same frequencies
• Cells, users (terminals), and physical channels
are separated by code
Codes
• Channelization codes for separation of
physical channels in the uplink and
separation of users in the downlink
•
Scrambling codes for separation of users/terminals in the uplink and
cells/sectors in the downlink
3,84 MHz
5 MHz
f
Guard Guard
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
Excurs – Cross-Correlation
Cross-Correlation
Two codes have a low cross-correlation if their product is low for all shift combinations
Low cross-correlation between a sequence and noise is useful to the receiver in filtering out
noise
Low cross-correlation between two sequences is useful to the receiver to discriminate
among signals generated by different users
If the cross-correlation between two sequences is 0, the sequences are said to be full
orthogonal
Cross-correlation between c1 and c2 is
c3 and c4 are orthogonal, because their cross-correlation is
c1: +1 +1 +1 +1 −1 +1 +1 −1
c2: −1 +1 −1 +1 +1 −1 −1 +1
−1 +1 −1 +1 −1 −1 −1 −1 =4
c3: −1 −1 −1 +1 +1 −1 +1 +1
c4: −1 −1 +1 −1 +1 +1 +1 −1+1 +1 −1 −1 +1 −1 +1 −1 =0
5.08
40
2,1
08
00
4,3
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
1
1,1
1,-1
1,1,1,1
1,1,-1,-1
1,-1,1,-1
1,-1,-1,1
1,1,1,1,-1,-1,-1,-1
1,1,1,1,1,1,1,1
1,1,-1,-1,1,1,-1,-1
1,1,-1,-1,-1,-1,1,1
1,-1,1,-1,1,-1,1,-1
1,-1,1,-1,-1,1,-1,1
1,-1,-1,1,1,-1,-1,1
1,-1,-1,1,-1,1,1,-1
C1,1
C2,1
C8,5
C8,4
C8,3
C8,2
C8,1
C4,4
C4,3
C4,2
C4,1
C2,2
C8,8
C8,7
C8,6
UMTS – Channelization Codes
• Orthogonal Variable SpreadingFactor (OVSF): method toobtain variable lengthorthogonal codes thatpreserve orthogonalitybetween different rates andspreading factors
• Recursive generation of variable orthogonal codesusing a tree structure
• A node adopts the code fromits predecessor andconcatenates it either with acopy of this code (firstsuccessor) or with its inverse(second successor)
• Codes of the same layer are
orthogonal• Any two Codes of different
layers are orthogonal exceptfor the case that one of thetwo codes is a mother code of the other
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
UMTS – Channelization Codes(II)
Example:
C4,2 is assigned to a user
Codes C8,3 and C8,4 generated from this code cannot be assigned to other users requesting lower bit rates
Mother codes C1,1 and C2,1 cannot be assigned to users requesting higher rates
bit rate * spreading factor = 3.84 Mcps
1
1,1
1,-1
1,1,1,1
1,1,-1,-1
1,-1,1,-1
1,-1,-1,1
1,1,1,1,-1,-1,-1,-1
1,1,1,1,1,1,1,1
1,1,-1,-1,1,1,-1,-1
1,1,-1,-1,-1,-1,1,1
1,-1,1,-1,1,-1,1,-1
1,-1,1,-1,-1,1,-1,1
1,-1,-1,1,1,-1,-1,1
1,-1,-1,1,-1,1,1,-1
C1,1
C2,1
C8,5
C8,4
C8,3
C8,2
C8,1
C4,4
C4,3
C4,2
C4,1
C2,2
C8,8
C8,7
C8,6
Spreading factorBit rate
8480 kb/s
4960 kb/s
16240 kb/s
5127.5 kb/s
25615 kb/s
12830 kb/s
6460 kb/s
32
Chip rate
3.84 Mcps
3.84 Mcps
3.84 Mcps
3.84 Mcps
3.84 Mcps
3.84 Mcps
3.84 Mcps
3.84 Mcps120 kb/s
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
Wintersemester 2010/2011, GSM & UMTS - Introduction
UMTS – Drawbacks of Channelization Codes
Problem 1
•
Networks based on WCDMA haveusually a cluster size of 1
• Thus, access to the code tree must becoordinated between adjacent cells oreach cell needs its own code tree
Problem 2
• Propagation delay of users withdifferent distances to the node B coulddestroy the orthogonality of the usedcodes (see example)
• Codes are received asynchronously
Scrambling codes
• Sector and cell separation in the
downlink• Terminal and cell separation in the
uplink
• Codes remain nearly orthogonal if received asynchronously
NBx m
x+78 m
1 1 -1 -1 1 1 -1 -1 1 1 -1 -1
1 -1 -1 1 1 -1 -1 1 1 -1 -1 1Propagation delay
A
B t
User B:
C4,4User A: C4,2
Orthogonality is lost!
Example for (2):
Two users A and B use channelization codes
C4,2 and C4,4
Difference in the distance to the node B is 78 m,
which is covered by the signal in 0,26s
(corresponds to the duration of 1 Chip)
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Prof. Dr. C. Linnhoff-Popien, M. Kessel, K. Wiesner - Praktikum Mobile und Verteilte Systeme
GSM & UMTS – Practical Courses
33
Set up of
Android
project
Cell-ID
positioning
Reading of Cell
related
information