Lecturer:Michael O'Grady

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Wireless Network Structure

• Lecturer Michael O'Grady
• Course MSc Ubiquitous Multimedia Systems
• Unit Context Sensitive Service Delivery
• Lecture

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Objectives

• Describe GSM
• Outline the evolution of GSM to 3G
• Describe the implications for services of this
  evolution.
• Review the Cellular Concept
• Introduce WiFi, Bluetooth and Satellite telephony
• Introduce Software Defined Radio

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History of GSM - I

• 1982 Group Spéciale Mobile formed (origin of term
  GSM)
• 1897 Initial Memorandum of Understanding (MoU)
  signed by network operators representing 12
  countries
• coordinate introduction of GSM
• agree time scales
• plan the introduction of services
• coordinate routing, billing and tariffs
• 1988 - Validation trials

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History of GSM - II

• 1989 - European Telecommunications Standard
  Institute (ETSI) formed
• 1991 - Launch delayed due to lack of mobiles
• 1992 - Officially launched
• 1993 - Commercial services start outside Europe
• 2003 - Over 200 countries
• 2004 - Over 1 billion subscribers?
• Ref http//www.gsmworld.com

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Anticipated Benefits of GSM

• Superior speech quality
• Low terminal costs
• Better security
• Low power portable terminals
• Support for international roaming
• New services

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Motivations for GSM

• Political Considerations
• Impending EU unification
• Deregulation of mobile telephony
• Economic Considerations
• single market
• cost benefits through economies of scale
• potential for export

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GSM Services - Phase 1
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GSM Services - Phase 2
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GSM Services - Phase 2

• Primarily concerned with the improvement of
  Bearer (data!) services
• Full data rate _at_ 14.4 kb/s
• High Speed Circuit Switched Data (HSCSD)
• General Packet Radio Service (GPRS)
• Some additional supplementary services also
  specified

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The GSM Family - 1

• GSM 900
• Uplink - 890 MHz to 915 MHz
• Downlink - 935 MHz to 960 MHz
• GSM 1800
• Also known as
• PCN (Personal Communications Network)
• DCS 1800 (Digital Cellular System 1800)
• Uplink - 1710 MHz to 1785 MHz
• Downlink - 1805 MHz to 1880 MHz

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The GSM Family - 2

• GSM 1900
• also known as PCS 1900/DCS 1900
• deployed main in North America
• Uplink - 1850 MHz to 1910 MHz
• Downlink - 1920 MHz to 1990 MHz
• Dual-Mode/Tri-band phones
• Roaming agreement necessary

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Architecture of a GSM Network
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Mobile Station (MS)

• Mobile Equipment
• Fixed
• Portable
• International Mobile Equipment Identity (IMEI)
  number
• Subscriber Identity Module (SIM)
• Personal Identification Number (PIN)
• International Mobile Subscriber Identity (IMSI)
  number
• Enables access to subscribed services
• Smart card

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Interfaces in GSM

• Interfaces of fundamental importance and
  documented by the standardization organizations
• Interface Definition
• An Interface may be defined by a set of
  technical characteristics describing the point
  of connection between two telecommunication
  entities. For example, the connection between a
  telecommunication network and the customers
  apparatus.
• Example Air Interface (Um Interface)
• Interface between Mobile Station and Base Station
  Subsystem

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Base Transceiver Station - BTS

• Usually referred to as the Base Station
• Provides the interface to the network for the MS
• Handles all communications with the MS
• Less intelligent than analogue equivalent
• cheaper than analogue systems
• bypass analogue in less wealthy countries
• intelligence now deployed on MS
• for example, when to perform a handover
• Transmitting power determines cell size

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Base Station Controller - BSC

• Controls Base Stations
• up to several hundred depending on manufacturer
• Manages radio channels
• allocation and release
• Coordinates Handover
• Physical location may vary
• Abis interface
• between BSC and BTS

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Network SubSystem(NSS)

• Nerve Centre of entire GSM network
• Manages all
• call processing
• subscriber related functions
• Contains
• the core switching component
• a number of databases
• gateways to other networks
• Uses Signalling System Number 7 (SS7)

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Mobile Switching Centre (MSC)

• Performs all switching/exchange functions
• Handles
• registration
• authentication
• location updating
• A GSM network must have at least one MSC
• May connect to other networks
• Gateway MSC (GMSC)

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Home Location Register (HLR)

• Administrative information for all subscribers
• IMSI number
• actual phone number
• permitted supplementary services
• current location i.e. which VLR subscriber is
  currently registered with
• parameters for authentication and ciphering
• One HLR per GSM PLMN

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Visitor Location Register (VLR)

• Contains data on all MSs currently in the area
  served by the MSC
• permanent data (identical to that in HLR)
• Consulted during
• call establishment
• caller authentication
• Usually integrated with MSC so that geographic
  area covered by both coincides
• signalling requirements simplified considerably

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Equipment Identity Register (EIR)

• Maintains lists of IMEI numbers of all valid and
  invalid equipment for the network
• IMEI - International Mobile Equipment Identity
• An IMEI may be invalid if
• stolen
• not approved for use on the network, possibly due
  to some defect
• EIR consulted during registration/call setup

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Authentication Centre (AUC)

• Protected database
• Stores all algorithms used for authentication
  purposes
• Knows which one has been issued to the subscriber
  (stored on SIM card)
• provides HLR or VLR with parameters for
  completing authentication

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Other Network Components

• Operations Maintenance Centre
• Intelligent Networking
• Billing Centre
• SMS Gateway

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Integrating GPRS
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GPRS MS

• Two Components
• Mobile Terminal (MT)
• SIM card
• Three Classes of terminal
• Class A - simultaneous circuit switched (GSM) and
  packet switched (GPRS) traffic
• Class B- supports both GSM and GPRS connections
  but not both at the same time. One call is
  suspended for the duration of the other
• Class C - handless both GPRS or GSM but can only
  be connected to one at the same time.

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GPRS BSS

• GPRS has minor impact on the BSS
• Packet Control Unit introduced
• Usually integrated into the BSC
• Essentially, a software update

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GPRS NSS

• Two new nodes introduced for packet data
• Serving GPRS Support Node (SGSN)
• handles all packet data for the appropriate
  geographic area
• monitors GPRS users
• handles security and access control
• may be regarded as the packet switched equivalent
  of the circuit-switched MSC
• Gateway GPRS Support Node (GGSN)
• internetworking functionality
• routes incoming data to correct SGSN
• translates between different protocols and
  formats
• Details of data services added to HLR

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GPRS - Summary

• Data capacity increased considerably
• Depending on configuration
• _at_ 14.4 kb/s per channel, 115.2 kb/s achieved
• _at_ 21.4 kb/s per channel, 171.2 kb/s achieved
• BUT up to 8 users per channel!
• Minimum set-up time
• always-on connection
• Charging determined by actual data not time

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Integrating EDGE

• Minimum changes to the existing network
• New Modulation scheme
• 8 phase shift keying (8PSK)
• 3 bits of information per signal pulse
• data rates increased by a factor of three

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EDGE - MS

• Upgrade is necessary
• Situated complicated by
• higher data rates on the downlink only
• higher data rates on both the uplink and downlink

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EDGE - BSS

• Significant changes
• software upgrades on all BTSs and BSCs
• New transceiver unit for all BTSs
• support legacy GSM GPRS traffic
• switch to EDGE only as required

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EDGE - NSS

• Minimum impact on the core network
• SGSN GGSN practically independent of data rates
• Some minor software upgrades

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3G - UMTS
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UMTS - MS

• User Equipment
• Mobile Equipment
• UMTS SIM (USIM)
• Air interface
• UMTS Terrestrial Radio Access (UTRA)
• W-CDMA
• TD-CDMA

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UMTS BSS

• Radio Network Subsystem
• Two new network elements
• Node B
• equivalent of a BTS
• Radio Network Controller
• supports a number of Node Bs
• equivalent of a BSC
• Obviously, UMTS has major implications for the BSS

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UMTS NSS

• Core Network (CN)
• Minimum changes
• mainly software upgrades

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Enabling UMTS Services - 1

• Some initiatives launched to aid the deployment
  of new services
• Mobile Station Execution Environment (MExE)
• categorize handsets using classmarks
• SIM Application Toolkit (SAT)
• standardized execution environment
• ensures interoperability between any SIM and any
  ME
• Virtual Home Environment (VHE)
• roaming users enjoy the same standard of services
  and the exact same services wherever they roam.

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Enabling UMTS Services - 2

• Customised Applications for Mobile networks
  Enhanced Logic (CAMEL)
• essential for the VHE
• Open Services Access (OSA)
• provides a standard scalable and extensible
  interface through which standard network
  functionality can be accessed
• Recall propriety nature of telecommunications
  networks!

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Other Initiatives

• Parlay Consortium
• Java Intelligent Network Initiative (JAIN)
• Mobile Games Interoperability Forum (MGI Forum)
• M-Services
• GSM Association
• Common set of services available globally

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The Cellular Principle

• Relies on the concept of concurrency
• delivered through channel reuse i.e. reusing
  channels in different cells
• Total coverage area is divided into cells
• only a subset of channels available in each cell
• All channels partitioned into sets
• sets assigned to cells
• Rule assign the same set to two cells that are
  sufficient geographically distant so that
  interference is small
• Net result increased capacity!

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Advantages of Cellular Networks

• More capacity due to spectral reuse
• Lower transmission power due to smaller
  transmitter/receiver distances
• More robust system as Base Station problem only
  effects the immediate cell
• More predictable propagation environment due to
  shorter distances

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Disadvantages of Cellular Networks

• Need for more infrastructure
• Need for fixed network to connect Base Stations
• Some residual interference from co-channel cells
• Handover procedure required

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WiFi

• Wireless Fidelity (WiFi)
• IEEE 802.11b
• 50m range approximately
• Data rates vary
• 11 Mb/s in theory
• 7 Mb/s is more realistic
• Walls can reduces range and throughput
• Number of users can reduce data rates

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WiFi Problems

• Security
• WiFi was not designed with robust security in
  mind
• Interference
• operates in unlicensed 2.4 GHz spectrum
• competes with other products e.g microwave ovens!
• Scarcity of hotspots

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Bluetooth

• 1998
• Goal eliminate the need for cables
• Short range - 10m
• data rate - 1 Mb/s
• Example of an ad-hoc network
• network formed on an as-needed basis

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Bluetooth Topology

• Piconet
• Two or more Bluetooth devices
• One master
• regulates traffic between devices
• Remainder termed slaves
• Scatternet
• Two or more piconets
• Note that a device can be a member of more than
  one piconet at a given time.

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Satellite Telephony
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Software Defined Radio

• Incompatible technologies
• Gardai, Fire brigade etc
• Different protocols, air interfaces etc
• Legacy telecommunications systems
• Solution
• Implement modules in software!
• Power consumption .
• Additional Processing required
• Goal Ubiquitous Connectivity.

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Cognitive Radio

• 3G cellular parameters fixed
• SDR parameters dynamic
• CR parameters intelligently adapted
• Sense environment usage patterns etc
• Learn patterns, rules etc
• Act accordingly
• Note most spectrum unused!!!!!!!!!
• Objective maximise spectrum efficiency

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Summary

• Examined GSM
• Traced the proposed migration of GSM to 3G
• Outlined some implications for data services
• Introduced some additional wireless technologies
  including Bluetooth, WiFi and Satellite telephony

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The End