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Lecturer: Michael O'Grady
Course: MSc Ubiquitous & Multimedia Systems
Unit: Context Sensitive Service Delivery
Lecture:
Wireless Network Structure
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
History of GSM - I
1982Group Spéciale Mobile formed (origin of term GSM)
1897 Initial Memorandum of Understanding (MoU) signed by network operators representing 12 countriescoordinate introduction of GSMagree time scalesplan the introduction of servicescoordinate routing, billing and tariffs
1988 - Validation & trials
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
Anticipated Benefits of GSM
Superior speech qualityLow terminal costsBetter securityLow power portable terminalsSupport for international roamingNew services
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
GSM Services - Phase 1
Service Category Service CommentsTeleservices Speech
EmergencySMS (Short Message Service)
Group 3 Fax
Full Rate 13KbpsPoint to Point & Cell Broadcast
Bearer Services Asynchronous DataSynchronous Data
300 – 9600bps300 – 9600bps
Supplementary Services Call ForwardCall Barring
Subscriber Busy, Not ReachableInternational & Incoming Calls
GSM Services - Phase 2
Service Category Service CommentsTeleservices Speech
EmergencySMS (Short Message Service)
Group 3 Fax
Half Rate 6.5KbpsPoint to Point & Cell Broadcast
Bearer Services Synchronous Packet Data Access 2400 – 9600bpsSupplementary Services CLI (Calling Line Identification)
Call WaitingCall HoldMultiparty
USSD (Unstructured SupplementaryService Data)
Operator BarringAdvice on charge
GSM Services - Phase 2+
Primarily concerned with the improvement of Bearer (data!) services Full data rate @ 14.4 kb/s High Speed Circuit Switched Data (HSCSD) General Packet Radio Service (GPRS)
Some additional supplementary services also specified
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
The GSM Family - 2
GSM 1900also known as PCS 1900/DCS 1900deployed main in North America
Uplink - 1850 MHz to 1910 MHz Downlink - 1920 MHz to 1990 MHz
Dual-Mode/Tri-band phonesRoaming agreement necessary
Architecture of a GSM Network
SD
Mobile Station
BTS
MSC/VLR
SIM MEBSC
Base StationSubsystem
GMSC
Network Subsystem
AUCEIR HLR
Other Networks
Note: Interfaces have been omitted for clarity purposes.
+
PSTN
PLMN
Internet
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
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
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
Base Station Controller - BSC
Controls Base Stationsup to several hundred depending on
manufacturer
Manages radio channelsallocation and release
Coordinates Handover Physical location may vary Abis interface
between BSC and BTS
Network SubSystem(NSS)
Nerve Centre of entire GSM networkManages all
call processingsubscriber related functions
Contains the core switching component a number of databases gateways to other networks
Uses Signalling System Number 7 (SS7)
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)
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
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
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 defectEIR consulted during registration/call
setup
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
Other Network Components
Operations & Maintenance Centre Intelligent Networking Billing Centre SMS Gateway
Integrating GPRS
SD
Mobile Station
BTS
MSC/VLRBSC
Base StationSubsystem
GMSC
Network Subsystem
AUCEIR HLR
Other Networks
Note: Interfaces have been omitted for clarity purposes.
GGSNSGSN
SIM ME
+
PSTN
PLMN
Internet
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.
GPRS BSS
GPRS has minor impact on the BSS Packet Control Unit introduced
Usually integrated into the BSC Essentially, a software update
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
GPRS - Summary
Data capacity increased considerablyDepending on configuration
@ 14.4 kb/s per channel, 115.2 kb/s achieved@ 21.4 kb/s per channel, 171.2 kb/s achieved
BUT up to 8 users per channel!Minimum set-up time“always-on” connectionCharging determined by actual data not
time
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
EDGE - MS
Upgrade is necessarySituated complicated by
higher data rates on the downlink only
higher data rates on both the uplink and downlink
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
EDGE - NSS
Minimum impact on the core network
SGSN & GGSN practically independent of data rates
Some minor software upgrades
3G - UMTS
SD
Mobile Station
MSC/VLR
Base StationSubsystem
GMSC
Network Subsystem
AUCEIR HLR
Other Networks
Note: Interfaces have been omitted for clarity purposes.
GGSNSGSN
BTS BSC
NodeB
RNC
RNS
UTRAN
SIM ME
USIMME
+
PSTN
PLMN
Internet
UMTS - MS
User Equipment Mobile Equipment UMTS SIM (USIM)
Air interface UMTS Terrestrial Radio Access (UTRA)
• W-CDMA• TD-CDMA
UMTS BSS
Radio Network SubsystemTwo 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
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.
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!
Other Initiatives
Parlay ConsortiumJava Intelligent Network Initiative
(JAIN)Mobile Games Interoperability Forum
(MGI Forum)M-Services
GSM Association Common set of services available
globally
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!
Advantages of Cellular Networks
More capacity due to spectral reuseLower transmission power due to
smaller transmitter/receiver distancesMore robust system as Base Station
problem only effects the immediate cell
More predictable propagation environment due to shorter distances
Disadvantages of Cellular Networks
Need for more infrastructureNeed for fixed network to connect
Base StationsSome residual interference from co-
channel cellsHandover procedure required
WiFi
Wireless Fidelity (WiFi)IEEE 802.11b50m range approximatelyData 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
WiFi Problems
Security WiFi was not designed with robust
security in mindInterference
operates in unlicensed 2.4 GHz spectrum
competes with other products e.g microwave ovens!
Scarcity of “hotspots”
Bluetooth
1998Goal: eliminate the need for cablesShort range - 10mdata rate - 1 Mb/sExample of an ad-hoc network
network formed on an “as-needed” basis
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.
Satellite Telephony
TYPE Altitude Characteristics Examples
GEO
(Geosynchronous
Earth Orbit)
35,800km Large coverage footprint
Small number of satellites
Large propagation delay
High power requirements
INMARSAT
LEO
(Low Earth Orbit)
Between
500km and
1500km
Small coverage footprint
Larger number of satellites
Faster response time
Low power requirements
Short life span of satellites
(due to increased radiation
at low altitudes)
Iridium
GlobalStar
MEO
(Medium Earth
Orbit)
Between
5000km
and
12000km
Essentially a compromise
between GEO and LEO
satellites with the respective
advantages and disadvantages
being affected accordingly.
Odyssey
ICO
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….
Cognitive Radio
3G – cellular parameters fixedSDR – parameters dynamicCR – parameters “intelligently”
adapted Sense environment – usage patterns etc Learn patterns, rules etc Act accordingly
Note: most spectrum unused!!!!!!!!!Objective – maximise spectrum efficiency
Summary
Examined GSMTraced the proposed migration of
GSM to 3GOutlined some implications for data
servicesIntroduced some additional wireless
technologies including Bluetooth, WiFi and Satellite telephony