UMTS

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UMTS

• Universal Mobile Telecommunications System

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Evolution of Mobile Communications

• 1G ( First Generation )
• Introduced in late 1970s and early 1980s.
• Transmits only analog voice information.
• Prominent 1g systems are
• Advanced Mobile Telephone Systems ( AMTS)
• Nordic mobile telephone (NMT)
• Total Access communication system (TACS)

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• 2G ( 2 Generation)
• Was implemented to improve Transmission quality,
  system capacity, and network coverage.
• Digital communication was implemented due to
  advancement in semiconductor technology.
• Provided supplementary services like fax, and
  short messaging service.
• 2G systems include
• GSM ( Global System for Mobile communications)
• D-AMPS (Digital AMPS)
• CDMA (Code Division Multiple Access )
• PDC (Personal Digital Communication)

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2.5 Generation

• 2.5 is a stepping-stone between 2G and 3G
  cellular wireless technologies, invented for
  marketing purposes only.
• Implemented a packet switched domain
• 2.5 G systems
• GPRS (General Packet Radio Service)
• EDGE (Enhanced Data rates for GSM )

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3G (Third Generation)

• 3G provide the ability to transfer both voice
  data (a telephone call) and non-voice data (such
  as downloading information, exchanging email,
  and instanting messaging).
• High Data Rates
• 3G systems
• UMTS (Universal Mobile Telecommunications System)
• CDMA 2000 ( Code Division Multiple access)
• TD-SCDMA (Time Division Syncronous CDMA)

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IMT-2000

• IMT-2000 (International Mobile Teleommunications
  ) a global standard for (3G) wireless
  communication defined by ITU( International
  Telecommunication Union
• UMTS is being developed by Third Generation
  Partnership project (3GPP), a joint venture of
  several organizations.
• ETSI (European Telecommunication Standard
  Institute, Europe)
• Association of Radio Industries and
  Business/Telecommunication Technology Committee
  (ARIB/TTC) (Japan)
• American National Standards Institute (ANSI) T-1
  (USA)
• Telecommunications technology association (TTA)
  (South Korea)
• Chinese Wireless Telecommunication Standard
  (CWTS) (China)
• To reach global acceptance, 3GPP is introducing
  UMTS in phases and annual releases.

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UTRAN (UMTS Terrestrial Radio access)

• The most significant change in Release. 99
  by3GPP.
•  UTRAN is subdivided into individual radio
  network systems (RNSs), where each RNS is
  controlled by an RNC
• UMTS defines four new open interfaces
• Uu UE to Node B (UTRA, the UMTS WCDMA air
  interface)
• Iu RNC to GSM Phase 2 CN interface (MSC/VLR or
  SGSN)
• Iu-CS for circuit-switched data
• Iu-PS for packet-switched data
• Iub RNC to Node B interface
• Iur RNC to RNC interface, not comparable to any
  interface in GSM

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UMTS Architecture

• The network of UMTS can be split into 3 main
  constituents.
• Mobile Station called the User equipment UE
• Base station subsystem known as Radio Network
  Subsystem (RNS)
• Core network.

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UE (User Equipment)

• equivalent to the mobile equipment (ME) used on
  GSM networks.
• The Circuit used in UE broadly split
• RF circuitry
  Handles all
  elements of the signal, both for the receiver and
  the transmitter .Uses liner RF power amplifier.
• Base band processing areas.
  Base band signal
  processing mainly consists of digital circuitry.
  This is considerably more complicated than that
  used in phones for previous generations.

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USIM (Universal SIM)

• Universal Subscribers Identity Module, advanced
  version of SIM card used in GSM
• contains the International Mobile Subscriber
  Identity Number (IMSI) as well as the Mobile
  Station International ISDN number (MSISD
• USIM also contains a short message storage area,
  phone book numbers and call information of the
  numbers of incoming and outgoing calls can also
  be stored.
• UMTS mobile station can operate in one of three
  modes of operation
• PS/CS mode of operation
• PS mode of operation
• CS mode of operation

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Radio Network Subsytem

• Interfaces to both the UE and the core network
• Radio transceiver is known as Node B,
  communicates with various UEs, radio Network
  controller (RNC )
• The RNC enables autonomous radio resource
  management (RRM) by UTRAN.
• Node B is the physical unit for radio
  transmission/reception with cells

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(Radio Network Subsystem)
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RNC Functions

• Performs the same functions as the GSM BSC,
  providing central control for the RNS elements
  (RNC and Node Bs) .
• The RNC handles protocol exchanges between Iu,
  Iur, and Iub.
• Congestion and handover/macro diversity are
  managed entirely by a single serving RNC (SRNC).
• Another RNC involved in the active connection
  through an interRNC soft handover,is declared a
  drift RNC (DRNC). The DRNC is only responsible
  for the allocation of code resources.
• The term controlling RNC (CRNC) is used to define
  the RNC that controls the logical resources of
  its UTRAN access points.

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Node-B

• Connects with the UE via the WCDMA Uu radio
  interface and with the RNC via the Iub
  asynchronous transfer mode (ATM)based interface
• Node B is the ATM termination point
• Node B is the conversion of data to and from the
  Uu radio interface, including forward error
  correction (FEC), rate adaptation, WCDMA
  spreading/dispreading, and quadrature phase shift
  keying (QPSK) modulation on the air interface
• Measures quality and strength of the connection
  and determines the frame error rate (FER)
• The Node B also participates in power control via
  the inner-loop power control

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Node B overview
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Frequencies

• Currently six bands that are specified for the
  use for UMTS/WCDMA.
• Much of the focus on UMTS is currently on
  frequency allocations around 2GHz.
• Uplink Frequency 1885- 2025 MHZ
• Downlink Frequency 2110- 2200 MHz
• The channels are spaced by 5MHz.
• The downlink uses quadrature phase-shift keying
  (QPSK) for all transport channels.
• Uplink used two separate channels so that the
  cycling of the transmitter on or off does not
  cause interference to the audio lines.

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Spreading

• Data to be transmitted is encoded using a
  spreading code particular to a given user
• Only the desired recipient is able to correlate
  and decode the signal, all other signals
  appearing as noise, this allows Physical RF
  channel to be used by several users
  simultaneously.
• The data of a CDMA signal is multiplied with a
  chip or spreading code to increase the bandwidth
  of the signal
• Each physical channel is spread with unique and
  variable spreading sequence. The overall degree
  of spreading varies to enable the final signal to
  fill required channel bandwidth Each physical
  channel is spread with a unique and variable
  spreading sequence.

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Synchronization

• Synchronisation is provided from the Primary
  Synchronisation Channel (P-SCH) and the Secondary
  Synchronisation Channel (S-SCH)
• They spread using synchronisation codes, two
  types are used.
• Primary code and is used on the P-SCH
  primary code is the same for all
  cells and is a 256 chip sequence that is
  transmitted during the first 256 chips of each
  time slot. This allows the UE to synchronise with
  the base station for the time slot
• Secondary code and is used on the S-SCH
  sixteen different secondary
  synchronisation codes.Scrambling codes in the
  S-SCH enable UE to identify which scrambling code
  is being used and hence it can identify the base
  station

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Power Control

• Base station receives signals from UEs at same
  power level
• If not, the UEs further away will be lower in
  strength than those closer to the node B and will
  not be heard. This effect is called as the
  near-far effect.
• Power control is achieved using 2 techniques.
• open loop
  
  used during initial access
  before communication between the UE and node B is
  established
• closed loop
  
  A measurement of the signal
  strength is taken in each time slot. As a result
  of this a power control bit is sent requesting
  the power to be stepped up or down. This process
  is undertaken on both the up and downlinks
  
  
  

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Channels

• UMTS uses CDMA techniques (as WCDMA) as its
  multiple access technology, but it additionally
  uses time division techniques with a slot and
  frame structure to provide the full channel
  structure.
• A channel is divided into 10 ms frames, each of
  which has fifteen time slots each of 666
  microseconds length.
• The channels carried are categorised into three
  types
• Logical
  
  define the way in which the data
  will be transferred
• transport
  
  transport channel along with the
  logical channel again defines the way in which
  the data is transferred
• physical channels.
  
  Carries the payload data and govern the
  physical characteristics of the signal.

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Packet data

• Packet data is an increasingly important element
  within mobile phone applications.
• WCDMA is able to carry data in this format in two
  ways
• short data packets to be appended directly to a
  random access burst. This method is called common
  channel packet transmission and it is used for
  short infrequent packets.Delay in setting up a
  packet data channel and transferring the
  operational mode to this format is avoided.
• Larger or more frequent packets have to be
  transmitted on a dedicated channel. A large
  single packet is transmitted using a
  single-packet scheme where the dedicated channel
  is released immediately after the packet has been
  transmitted.

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Discontinuous reception

• One of the important issues with mobile phones is
  that of battery life. A key differentiators that
  people take into account when buying a phone.
• Discontinuous reception mode allows several
  non-essential segments of the phone circuitry to
  power down during periods when paging messages
  will not be received.
• By synchronising with the paging channels being
  transmitted it is able to turn the receiver on
  only when it needs to monitor the paging channel.
  As the receiver, with its RF circuitry, will
  consume power, savings can be made by switching
  it off.

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Handover

• Handover follows many of the similar concepts to
  those used for other CDMA systems.
• There are three basic types of handover. All
  three types are used but under different
  circumstances.
• Hard handover
  
  When UE moves out of range of one node B,
  the call has to be handed over to another
  frequency channel.
• soft
  
  Technique was not available on previous
  generations of mobile phone systems. Adjacent
  cell sites are on same frequency,as a result the
  UE can receive the signals from two adjacent
  cells at once,
• Softer Handover.
• The decisions about handover are generally
  handled by the RNC

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Advantages of UMTS over previous Generation
Handsets.

• UMTS is a successor to 2G based GSM technologies
  including GPRS and EDGE. Gaining a 3rd name 3GSM
  because it is a 3G migration for GSM
• Support 2Mbit/s data rates. Higher Data rates at
  lower incremental costs.
• Benefits of automatic international roaming plus
  integral security and billing functions, allowing
  operators to migrate from 2G to 3G while
  retaining many of their existing back-office
  systems
• Gives operators the flexibility to introduce new
  multimedia services to business users and
  consumers
• This not only gives user a useful phone but also
  translates higher revenues for the operator.

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UMTS Applications

• Conversational Class applications
• Circuit switched voice service and Packet
  Switched Voiced Service
• Streaming Class applications
• Streaming / Download (Video, Audio)
• Videoconferences.
• Interactive Class applications
• Fast Internet / Intranet.
• Mobile E-Commerce (M-Commerce)
• Remote Login 
• Background Class applications
• Any non real time applications like
• Multimedia-Messaging, E-Mail
• FTP Access
• Mobile Entertainment (Games)