Issues

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3G NETWORKS
Abhinay Kontham
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Introduction to 3G
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Why 3G?

• Next few slides taken from web give various
  reasons as to why 3G was needed.
• Why do you think 3G was created?

4
Why 3G?

• Existing mobile networks (GSM/CDMA) were designed
  to handle voice traffic and voice-oriented
  services.
• Then, when they were introduced into the market
  it turned out that, other than voice-oriented,
  additional services (SMS to set an example)
  gained unexpected popularity.
• The need for data transmission through mobile
  networks has been growing gradually together with
  Internet popularity.

5
Why 3G?

• Therefore some network upgrades had to be
  introduced into existing mobile networks (HSCSD,
  GPRS).
• However, these improvements provide only limited
  capability (e.g. GPRS - up to 50kbit/s in
  reality). They don't provide flexible, variable
  data speed, supporting Quality of Service
  solutions.

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Lack of Resources

• Another important factor is that together with
  the need for efficient data-oriented mobile
  networks, the beginning of radio resources
  shortage in dense populated areas has been
  observed, due to high level of penetration in
  mature mobile markets (penetration rates around
  50 and up to 80 in the Nordic countries).
• Therefore a new radio access technology is needed
  to cope with those problems.

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3G Vision

• Multimedia (voice, data video)
• Increased data rates
• 384 Kbps while moving
• 2 Mbps when stationary at specific locations
• Universal global roaming
• Increased capacity (more spectrally efficient)
• IP architecture

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3G Services The Promise

• Customised Infotainment
• Multimedia Messaging Service
• Mobile Intranet/Extranet Access
• Mobile Internet Access
• Location-based Services
• Rich Voice (simple and enhanced voice)

9
Designing 3G

• Technical arguments galore as to which
  technologies should be used.
• Standardisation bodies tried to come to agreement
  as to what was the best options

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The Standards Issue

• When the ITU tried to unify and standardize 3G
  technologies, no consensus was reached.
• There were thus five terrestrial standards
  developed as part of the IMT-2000 program.
• Instead, depending on where in the world 3G will
  be implemented, the 3G standard will be based on
  CDMA variants with some other technologies thrown
  in as well.

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IMT-2000 Terrestrial Radio Interfaces
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Standards adopted for IMT-2000

• Mode Description Standard
• IMT-DS DIRECT SEQUENCE W-CDMA
• UTRA FDD
• IMT-MC
  MULTICARRIER cdma2000
• IMT-TC
  TDMA/CDMA UTRA TDD
• TD-SCDMA
• IMT-SC SINGLE
  CARRIER UWC-136
• IMT-FT
  FDMA/TDMA DECT
• the three indicated in green are emerging as the
  most important

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Migration To 3G
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Issues

• REGIONAL BLACKOUTS
• APPLICATIONS TESTING
• IMPACT OF VOICE AND DATA TRAFFIC ON THE NETWORK

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Regional Blackouts

• Protection of broadcast content on 3G Networks
• One of the driving forces behind the
  development of 3G systems is the potential to
  deliver complex content to consumers.
• There is a growing collaboration between
  broadcast and mobile network providers.
• The challenge in providing such a service is
  content protection.

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• CONTENT PROTECTION
• Advances in mobile communication technology
  have provided the many services to the
  subscribers at any location.
• The removal of barriers to the delivery of
  such services raises the issues of content
  protection and digital rights management.
• Broadcasters are often required to restrict
  broadcast of certain content to specific
  geographic locations , or specific dates and
  times

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• CURRENT PROBLEM IN 3G NETWORKS.
• The location of the end devices in the
  network can be tracked using satellites and GPS
  technology but , this is a very costly solution
  for tracking low cost mobile devices without
  satellite reception.
• The problem is compounded where the receivers
  have the ability to store and forward content.

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• TRUSTED HARDWARE SOLUTION
• An obvious way to provide trustworthy
  location data is to use a hardware that is
  trusted by the content provider. This can be done
  by using a GPS system but it is an expensive
  method to implement.
• Alternatively, the end device could be
  connected to the trusted part of the intermediate
  network. The network can then provide the current
  location and time of the gateway from which the
  end device is receiving on a special request.
• the problem wit this methodology is that it
  restricts to the end device which can be directly
  connected to the trusted network.

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NETWORK MODEL
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Issue -2

• APPLICATIONS TESTING
• The 3G networks demand for test and
  verification methods that achieve high quality
  terminal and software environments that enable
  free introduction of 3G applications and
  services.

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• WHAT THE USER EXPECTS..
• Providing applications and content is key to
  the success of the 3G networks. These
  applications include video mail, video streaming,
  interactive gaming and high speed web browsing.
• The customer expects to be able to use these
  applications anytime and at any place in the
  3G networks even while he is roaming.

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• TESTING IN 3G NETWORKS
• In the 3G networks there needs to be
  interoperability between the application layer in
  the handset and the server.
• The application layer testing in the 3G
  networks can be divided into two steps
• Application Layer Testing and
• Application Delivery Testing

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• Application layer testing
• In this phase we are looking to test the
  correct operation of the application in the
  handset and the correct interaction between the
  application processor in the handset and the
  server.
• Application delivery testing
• In this phase we look at how the application
  works in the dynamic networks , with radio
  propagation issues , network errors and changing
  radio bearer configurations.

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• PROPOSED SOLUTIONS
• The current testing strategy are useful for
  testing on live networks where it is
  difficult to create faults in repeated and
  controlled manner.
• The test and measurement industry is now
  developing new types of system simulator
  environments that move beyond conformance tests
  and allows operators to quickly and easily test
  applications in many complex and demanding
  environments.

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(No Transcript)
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Issue-3

• IMPACT OF VOICE and DATA TRAFFIC
• The provision of multimedia services to mobile
  users is one of the main goals of 3G systems.
• The traffic transferred in the network will
  be composed by different information flows with
  various constraints on the required QoS.
• The issue over here is to decide whether to
  share a single frequency between different
  services or reserve different frequencies for
  different services.

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UMTS

• The UMTS terrestrial radio access network
  (UTRA) is devised to provide access to different
  services ranging from the classical speech
  service (8-12,Z Kb/s) to high rate packet data
  service (up to2 Mb/s).
• W-CDMA (Wideband CDMA) which adopts
  frequency division duplexing (FDD), and TD-CDMA
  (Time Division and Code Division Multiple Access)
• which is based on time division duplexing
  (TDD)
• The UMTS standardization bodies have
  designed a radio interface highly flexible able
  to provide different bearer services with
  different bit rates and different transfer modes
• Circuit switching and packet switching are
  the two transfer modes that are available

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• In each transfer mode different quality of
  service can be achieved by suitably setting
  physical layer parameters such as the spreading
  factors (SF) of the physical channels, the rate
  of the FEC (Forward Error Correction) code used
  to protect information hits, the target SIR of
  the power control procedure
• 3G operators have to decide whether to
  reserve different frequency carriers to different
  services or to share a single frequency carrier
  between different services.
• When different services contend for the
  shared resource, their performance
  characteristics may highly change from the single
  service case.

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• Transport channels are divided into dedicated
  channels, which can be assigned and then used
  only for transmissions to and from a single
  mobile terminal (MT) at a time, and common
  channels which are time shared by different MTs
• Speech traffic is transported over dedicated
  channels. Dedicated Channels (DCH) are assigned
  to single users through set-up and tear down
  procedures and are power controlled according to
  a closed loop mechanism that adjusts transmission
  power in order to keep the SIR (Signal
  to-Interference-Ratio) at a target value.

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• Packet data can he delivered using a
  circuit oriented scheme which still adopts
  dedicated channels, or can be delivered using
  ad-hoc shared resources. In particular, two
  different shared channels are available for
  packet transmissions DSCH (Downlink Shared
  Channel) and FACH (Forward Access Channel).
• DSCH users must have an associated active
  DCH on the downlink whose power control mechanism
  is also used to control the power of the shared
  channel itself.
• The FACH is shared by many users to transmit
  short bursts of data, but, unlike DSCH, no
  closed-loop power control is exerted and no DCH
  must he activated to access this channel.

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• Experimental Setup
• The performance of the network is measured
  by using three parameters
• SIR (Signal to Interference
  Ratio)
• BLER (Block Error Rate , to
  measure quality of voice calls)
• Average packet delay and
  throughput are used to
  measure the data traffic performance.

32

• RESULTS OF VARIOUS SIMULATIONS
• All the results that are being presented
  were obtained using steady state simulations 900
  seconds long. The first 100 seconds are used as
  warm up time , no data is collected during this
  time.
• The remaining 800 seconds are divided into
  four simulation runs and during each run the
  results are collected and used to evaluate one
  sample of each statistical data.

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• Simulation conditions
• No Data in the network
• Only a number of voice calls
• are accepted

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• If a too small SIR target is chosen too
  many errors occur since the code protection
  is useless. On the other side, with a high SIR
  target the
• power requirement increases and too many
  transmissions tend to
• be driven into saturation.
• We observe that for almost all the cases
  considered the SIR target value around 3 dB
  provides the lowest BLER. With such a SIR target
  value, up to 80 voice users per cell can be
  served with a BLER lower than 1.

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SECOND SIMULATION
10 data users using 4 DSCH channels at a data
rate of 100Kbps
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• Results of the second simulation are
• Number of voice calls is reduced to 65 from
  80
• The SIR target value is 2dB higher than the
  value which provides lowest BLER in only voice
  calls scenario
• The interference has a higher standard
  deviation in the case of mixed traffic, therefore
  the power control cannot easily track
  interference variations and an higher value of
  SIR target is needed in order to prevent the SIR
  fluctuations from affecting the BLER of voice
  calls

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• INTERFERENCE STANDARD DEVIATION vs NUMBER OF
  VOICE USERS

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• The next figure shows the average packet
  delivery delay versus the throughput of one SF 4
  DSCH shared by 10 data users, for several numbers
  of voice users active in the same cell.
• The performance of the downlink shared
  channel is obviously affected by the presence of
  voice calls interference, and drops dramatically
  if the number of voice users grows above 30.

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(No Transcript)
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• CONCLUSIONS OF THE EXPERIMENTS.
• The system capacity always decreases when
  mixing voice and data traffic in the network.
• Data transmissions can operate temporarily
  beyond full capacity even if the required power
  is not there , since they can take advantage of
  retransmissions
• Adding a certain load of data traffic
  requires to drop an higher load of voice traffic
  due to the increased burstiness of interference
  level.

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• The interference generated by the voice
  calls limits the capacity of data service in
  terms of maximum throughput.

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3G vs Wimax
Wimax today
UMTS TDDs Quiet Path
Hype
UMTS TDD today
3G FDD today
Gartner Hype Cycle
TDD no-hype shortcut
Time
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Will there really be any market opportunity left
in 2009?

• Enterprises should continue watching the
  technology but not consider short-term
  deployment Gartner Research Brief, May 11 2004

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references

• http//www.kerton.com/papers/Kerton_WCA_20june200
  4.ppt275,12,But Dont Take My Word For It
• http//libproxy.library.unt.edu2133/iel5/71/28460
  /01271183.pdf?tparnumber1271183isnumber28460
• http//libproxy.library.unt.edu2133/iel5/9803/309
  12/01434515.pdf?tparnumber1434515isnumber3091
  2
• http//libproxy.library.unt.edu2133/iel5/9803/309
  12/01434450.pdf?tparnumber1434450isnumber3091
  2