UNESCOCISM SECOND ADVANCED SCHOOL OF INFORMATICS UNESCO PROJECT Advanced Course on Networking Introd

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UNESCO/CISM SECOND ADVANCED SCHOOL OF
INFORMATICSUNESCO PROJECT Advanced Course on
Networking Introduction to Cellular Wireless
Networks On the Road to UMTS
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Mobile Communications system Evolution
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Outline

• GSM
• GPRS
• UMTS
• CDMA
• WCDMA
• Summery

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What is GSM??
(Global System for Mobile Communications)
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GSM Architecture

• Three broad parts
• Mobile Station (MS) carried by the subscriber
• Base Station Subsystem control radio link with
  MS
• Network Subsystem its main part is MSC
• Interfaces
• Um Interface known as air interface or radio
  link.
• Abis Interface between BTS and BSC
• A Interface between BSC and MSC

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Mobile Station

• ME(mobile equipment)
• the terminal
• SIM (Subscriber identity Module)
• provides personal mobility.
• Can insert the SIM card into another GSM terminal
  and use

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Base Station Subsystem

• BTS (Base Transceiver Station)
• handle the radio link protocols with the Mobile
  Station
• many BTSs in a large urban area
• BSC (Base Station Controller)
• manages the radio resources for one or more BTSs
• handles such as channel setup , frequence
  hopping and handovers.
• connection between MS and MSC

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Network Subsystem

• MSC (Mobile Services Switching Center)
• acts like a normal switching node of the PSTN or
  ISDN
• provides the connection to the fixed networks
  (such as the PSTN or ISDN).
• HLR (Home Location Register )
• contains information of each subscriber
  registered in the corresponding GSM network,
  along with the current location of the mobile.
• logically one HLR per GSM network

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Network Subsystem cont.

• VLR (Visitor Location Register)
• contains selected information from the HLR,
  necessary for call control and provision of the
  subscribed services,
• each mobile currently located in the geographical
  area controlled by the VLR.
• EIR (The Equipment Identity Register)
• a database that contains a list of all valid
  mobile equipment on the network,
• AuC (The Authentication Center)
• is a protected databasesecret key of SIM

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GSM Features

• Multiple access use TDMA/FDMA to share the
  limited radio spectrum
• The FDMA part involves the division by frequency
  of the (maximum) 25 MHz bandwidth into 124
  carrier frequencies spaced 200 kHz apart.
• Each of these carrier frequencies is then divided
  in time, using a TDMA scheme.
• GSM is a digital network
• Based on Circuit-switch

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GSM Features cont.

• SMS Short Message Service
• is a bi-directional service for short (up to 160
  bytes) messages. Messages are transported in a
  store-and-forward fashion.
• an acknowledgement of receipt is provided to the
  sender.
• can also be used in a cell-broadcast mode, for
  sending messages such as traffic updates or news
  updates. Messages can also be stored in the SIM
  card for later retrieval

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GPRS System
(General Packet Radio Service)
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GPRS Architecture

• Introduce two new nodes into GSM network
• SGSN (the Serving GPRS Support Node)
• Keep track of the location of the mobile within
  its service area and send/receive packets from
  the mobile , passing them on, or receiving them
  from the GGSN
• GGSN (Gateway GPRS Support Node)
• convert the GSM packets into other packet
  protocols (e.g.IP or X.25) and send them out into
  another network.

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GPRS Features

• Log on to GPRS
• A GPRS-capable terminal communicates with GSM
  base Stations, but unlike circuit-switched data
  calls which connects to MSC, GPRS packets are
  sent from the base station to SGSN, SGSN
  communicates with GGSN.
• Establishes a Packet Data Protocol (PDP) which is
  logical connection between the mobile and GGSN
• now visible to the outside fixed networks

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GPRS Features Cont.

• SGSN and GGSN use GPRS tunnel protocol (GTP)
  which operates over the top of TCP/IP to
  encapsulate the packets
• Tunnels information may be encrypted and
  additional data is added to each packet to
  prevent tampering
• Packed based
• No dial-up, just as with a LAN connection.
• No delay for sending data

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GPRS Features Cont.

• pay for the amount of data they actually
  communicate, and not the idle time
• users need to confirm their agreement to pay for
  the delivery of content from the service. This is
  performed by using WAP (Wireless Application
  Protocol)
• unsolicited packets may not be charged
• voice and Data Communication at the same time
• can be viewed as a sub-network of the Internet

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GPRS Features Cont.

• Spectrum Efficiency
• users can share the resource (Radio link),it is
  used only when users are actually sending or
  receiving data
• Speed Based on GMSK
• a modulation technique known as Gaussian
  Minimum-shift keying.
• Theoretical Max speeds up to 171.2kbps.(GSM9.6Kbp
  s)

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GPRS Features Cont.

• a channel that is 200kHz wide, is divided into 8
  separate data streams, each carrying maximum
  20kbps(14.4kbps typical), GSM only use one
  channel, GPRS combine up to 8 of these channels.
• complement rather than replace the current data
  services available through todays GSM
• doesn't require new radio spectrum
• supports TDMA also use for IS-136

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Scenario for Migration from 2G to 3G
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What are 3G Technologies?

• UMTS (Universal Mobile Telecommunications
  Service)
• EDGE can co-exist with UMTS
• e.g. Edge provide high speed services for
  wide-area coverage while UMTS is deployed in
  urban hot spots.
• Cdma 2000
• based on the cdma One standard, two air modes
• one based on the parallel use of 3 contiguous
  cdmaOne carriers (multi-carrier approach),
• the other one on the use of the corresponding 3
  carriers width spreading (direct spread approach)
  

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What does UMTS provide?

• Circuit- and Packet-Oriented Services
• Seamless Global Roaming
• Capacity and Capability to serve more than 50
  population
• A Wide Range of Services
• Voice, low-rate data and high-rate data
• 144kb/s, 384kb/s , 2Mb/s

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UMTS coverage vs. bit rate
UMTS
Vehicle
Outdoors
Broadband Radio
Walk
Fixed
Indoors
GSM
155Mb/s
2.0
0.5
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UTRAN-UMTS Terrestrial Radio Access Network
Core Network
lu
lu
lu
lur
lur
RNC
RNC
RNC
lub
Node B
Node B
Node B
Node B
Node B
Node B
Uu
MH
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Frequency Allocation

• 1920-1980 MHz paired with 2110-2170 MHz
• Total 35 MHz unpaired band

C
MSS
B
C
A
A
MSS
1920
2010
2110
2170
1980
2200
2025
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FDD vs. TDD

• Both FDD and TDD are available in UMTS
• TDD has been designed for use in high density
  areas
• The highest bearer rate
• TDD-2.048Mb/s
• FDD-384kb/s

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CDMA(Coded Division Multiple Access)

• In CDMA, every user assigned a unique
• Code

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WCDMA

• Radio Parameters
• Performance Improvement
• Channels
• Channel Generation
• Power Control
• Handoff

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WCDMA Radio Parameters

• Group 200KHz bands into 4.2-5.0 MHz carriers
• Chip Rate is 4.096 Mchips/sec
• System Capacity of 128 channels per cell provided
  by 5 MHz bandwidth

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WCDMA Performance Improvement

• Capacity Improvement
• No Frequency Planning
• Multiple Services per Connection
• Frequency Handoff
• HCS
• Hot Spot

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HCS Hot-Spot
HCS-Scenario
Hot-Spot Scenario
Hot-Spot
Macro
Macro
Micro
f2
f2
f1
f1
f1
f1
f1
Handoff between layers is alwayse needed
Handoff at Hot-Spot is sometimes needed
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WCDMA Channels

• Transport channels are the services which the
  physical layer provides to higher layers.
• The number of transport channels is much higher
  than for GSM as more services are needed.
• Transport channels are grouped into two classes
• Common channels (where information is transmitted
  to all mobile terminals without distinction)
• Dedicated channels (where communication takes
  place towards a single terminal by associating it
  with a physical channel, i.e. a code and a
  frequency or, in the case of TDD, also a time
  slot).

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WCDMA Channels.. Cont.

• The following common channels are provided
• BCH (Broadcast Channel) used on the downlink to
  transmit system information in the entire cell.
• FACH (Forward Access Channel) used on the
  downlink to transmit control information to
  mobile terminal. It also can be used to transport
  short data packets (as with GSM Short Message
  Service). FACH is used when the system knows the
  cell in which the terminal is registered.
• PCH (Paging Channel) used on the downlink to
  transmit control information to mobile terminal
  whose location is not known. Transmission here is
  associated with paging indicator which informs
  the mobile terminal that the information is
  present on the paging channel, thus permitting
  lower battery consumption.
• SCH (Synchronization Channel) used on the
  downlink to permit synchronization between the
  mobile terminal and base station.
• RACH (Random Access Channel) used on the uplink
  to transport control information transmitted by
  the mobile terminal.
• CPCH (Common Packet Channel) used on the uplink
  to transport data packets especially burst
  traffic.
• DSCH (Downlink Shared Channel) used in the
  downlink to transport data packets. Access is
  shared by various users and is regulated by the
  base station.

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WCDMA Channels.. Cont.

• There are certain physical channels which are not
  associated with a transport channel. They are
  used to transport physical layer information that
  does not need to be sent to higher layers.
• These channels are as follows
• CPICH (Common Pilot Channel) a downlink channel
  on which a known un-modulated sequence is
  transmitted.
• DPCCH (Dedicated Physical Control Channel)
  physical channel present on both links and used
  to transport physical layer signalling.
• AICH (Acquisition Indication Channel) present on
  the downlink and used to inform the mobile
  terminal that there is a message on the FACH
  channel in response to an access attempt.
• PICH (Paging indication Channel) present on the
  downlink and used to inform the mobile terminal
  that there is a message on the PCH channel.

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WCDMA Channels.. Cont.

• Physical Channels are typically based on the
  following structure
• Radio frame has a length of 10 ms and consists
  of 15 time slots.
• Time slot has a length of 10/15 ms. Each slot
  consists of a number of symbols which varies
  according to the bit rate of the service to be
  transmitted.
• Symbol this is the information element after the
  channel encoding operations (i.e. after error
  correction codes are inserted)

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Power Control In WCDMA

• Near-Far Problem in CDMA
• Different Performance for Subscriber Links
• A Few Subscribers closest to the BTS may
  contribute too much multiple Access Interference.

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Power Control In WCDMA

• How to do power control
• Force all users to transmit the minimum amount of
  power
• Reduce the power transmitted by users closest to
  the BTS increase the power transmitted by users
  farst to the BTS

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Power Control In WCDMA

• Open Loop vs. Close Loop
• Open Loop Power Control
• Subscriber measures the DL power and adjusts its
  transmission power
• Close Loop Power Control
• BS measures the UL power. MS measures the DL
  power and reports to the BS. BS instructs the
  user to raise or lower it transmission power

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WCDMA Soft Handoff
BS1
BS2
BS1
Active set BS1
BS2
BS1
Active set BS1 BS2 BS2 SS gt add threshold
BS2
Active set BS2 BS1 SS lt drop threshold
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Active Research Topics

• Cellular system architecture
• UMTS air interface
• Power control in CDMA
• Handoff
• Satellite-UMTS traffic
• Integrated All-IP 3G-WLAN

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Reference

• http//www.europe.alcatel.fr/telecom/rcd/keytech/
• http//www.comms.eee.strath.ac.uk/gozalvez/gsm/
• http//www.gsmworld.com/
• http//www.ibctelecoms.com/
• http//www.span.net.au/
• http//www.cdg.org/tech/a_ross/
• http//www.nokia.com/networks/mobile/
• http//www.gsmdata.com/
• http//www.sds.lcs.mit.edu/turletti/gmsk/
• http//www.wirelessweek.com/issues/3G/

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Reference

• http//www.umts-forum.org/reports.html
• http//www.itu.int/imt/
• http//www.etsi.org/
• Flavio Muratore UMTS, Mobile Communications for
  future, John Wiley Sons, 2001.
• S. Dutnall, N. Lobley, A. Clapton, UMTS The
  mobile part of broadband communications for the
  next century IEEE Atm Workshop, Proceedings.
  p242-252,1998
• S. Breyer, G. Dega, V. Kumar, L. Szabo, Global
  view of the UMTS concept Alcatel
  Telecommunications Review. n 3 1999. p 219-227
• M. Lee, CDMA Network Security , Prentice-Hall,
  1998
• U. Black, Mobile Wireless Networks,
  Prentice-Hall, 1999
• M. Gallagher, W. Webb, UMTS The next generation
  of mobile radio, IEE Review. v 45 n 2 1999. p
  59-63

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Reference

• A. Samukic, UMTS Universal Mobile
  Telecommunications SystemDevelopment of
  standards for the third generation, IEEE Global
  Telecommunications Conference Exhibition. v 4
  1998. p 1976-1983
• N. Prasad, GSM evolution towards third generation
  UMTS/IMT2000, IEEE International Conference on
  Personal Wireless Communications 1999, p 50-54
• A. Samukic, UMTS universal mobile
  telecommunications system Development of
  standards for the third generation, IEEE
  Transactions on Vehicular Technology. v 47 n 4
  Nov 1998. p 1099-1104

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Thank you !!!
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UNESCO PROJECT Advanced Course on Networking
Professor Khalid Al-BegainUNESCO/CISM SECOND
ADVANCED SCHOOL OF INFORMATICSUniversity of
Damascus, Syria, 06 - 15 April 2004