Wireless Network Structure. Lecturer: Michael O'Grady Course: MSc Ubiquitous & Multimedia Systems Unit: Context Sensitive Service Delivery Lecture:. Objectives. Describe GSM Outline the evolution of GSM to 3G Describe the implications for services of this evolution.
Une image / un lien ci-dessous est fourni (tel quel) pour télécharger la présentation
Politique de téléchargement : le contenu du site vous est fourni TEL QUEL pour votre information et votre usage personnel ; il ne peut être vendu, concédé sous licence ni partagé sur d’autres sites sans l’accord de son auteur.Le contenu vous est fourni TEL QUEL, pour votre information et votre usage personnel uniquement.Téléchargez la présentation en cliquant sur ce lien.Lors du téléchargement, si vous ne parvenez pas à télécharger une présentation, l’éditeur a peut-être supprimé le fichier de son serveur.Pendant le téléchargement, si vous ne parvenez pas à obtenir une présentation, le fichier a peut-être été supprimé par l’éditeur.
F I N
Plus de contenu associé
Transcription de la présentation
Wireless Network Structure Lecturer: Michael O'Grady Course: MSc Ubiquitous & Multimedia Systems Unit: Context Sensitive Service Delivery Lecture:
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 • 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
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 quality • Low terminal costs • Better security • Low power portable terminals • Support for international roaming • New 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 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 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
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 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
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)
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 defect • EIR 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
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 considerably • Depending 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” connection • Charging 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 necessary • Situated 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
UMTS - MS • User Equipment • Mobile Equipment • UMTS SIM (USIM) • Air interface • UMTS Terrestrial Radio Access (UTRA) • W-CDMA • TD-CDMA
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
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 Consortium • Java 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 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
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
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
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”
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
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.
