Mobile Services (ST 2010)

Transcription

1 Mobile Services (ST 2010) Chapter 2: Mobile Networks Axel Küpper Service-centric Networking Deutsche Telekom Laboratories, TU Berlin 1

2 Mobile Services Summer Term Mobile Networks 2.1 Infrastructure versus Ad-Hoc Networks 2.2 Global System for Mobile Communications 2.3 3G and 4G Networks 2.4 Local and Personal Networks 2

3 2.1 Infrastructure versus Ad-hoc Networks Infrastructure-based Networks (II) 4 4 AP Network infrastructure AP AP AP AP Infrastructure-based Networks Communication typically takes place between a mobile terminal and an access points (AP), but not directly between terminals Air interface control, network functions, mobility support, and service provision are primarily organized in the network infrastructure Terminals only adopt a minimal set of tasks which are inevitable to connect them to the network infrastructure or to provide the user with services Complexity resides at the infrastructure site, whereas the terminal can remain comparatively simple Note: infrastructure does not necessarily imply a wired fixed network (e.g., in satellitebased cellular telephony parts of the infrastructure (i.e., the satellites) operate wirelessly) 3

4 2.1 Infrastructure versus Ad-hoc Networks Infrastructure-based Networks (I) 4 4 A AP Network infrastructure C B AP AP Several wireless networks may form one logical network Different access points together with the infrastructure in between can connect several wireless networks to form a larger network beyond actual radio coverage Example: wireless networks A und B form a larger wireless network C Some procedures to support merging (not mandatory): handover, paging Handover: changing the assignment of a mobile terminal from one access point to another as the mobile moves from one radio cell to another Paging: procedure initialized by the infrastructure to determine the access point a certain terminal is attached to 4

5 2.1 Infrastructure versus Ad-hoc Networks Infrastructure-based Networks (III) AP Access points Transceiver unit (transceiver=transmitter+receiver) Medium access control Execution of handover and paging Forwarding function between devices and the network Bridging to other wireless or wired networks Power Control Switches Network device that selects a path or circuit for sending a unit of data to its next destination In contrast to conventional fixed networks, switches for mobile networks may be equipped with special features to support terminal and personal mobility AP AP Databases Localization (e.g., association between user and device and between device and access point) Storage of user profiles and user data Data for authentication Server for service provision Server AP Support of application services (i.e., services above connectivity services) AP AP 5

6 2.1 Infrastructure versus Ad-hoc Networks Ad-Hoc Networks Ad-hoc Networks No infrastructure is needed - each device can communicate with another device without support of access points or other infrastructure components Devices within an ad-hoc network can only communicate if they can reach each other physically, i.e., if they are within each others radio range or if other devices can forward the message Complexity of each device is higher because every node has to implement control mechanisms, e.g., for coordinating access to the air interface (Medium Access Control, MAC) 6

7 2.2 Global System for Mobile Communications GSM Overview (I) GSM900 (GSM at 900 MHz) GSM: Communication standard specified by the Group Spéciale Mobile (founded in 1982) Uses Gaussian Minimum Shift Keying (GMSK) as modulation scheme Primarily designed for speech telephony, but also used for circuit-switched data transmission with data rates up to 14.4 kbps Medium access: FDMA for channels and TDMA for user access Channel bandwidth 200 khz Operates at MHz for uplink and for downlink 124 channels with eight time slots each First GSM networks were introduced around 1990 Meanwhile adopted by >200 operators and servers >2 billion subscribers EGSM (Extended GSM) Provides an additional spectrum of 10 MHz on both uplink and downlink Operational frequencies are MHz (uplink) and MHz (downlink) Additional 10 MHz provides additional 50 frequency channels 7

8 2.2 Global System for Mobile Communications GSM Overview (II) GSM1800 and GSM1900 (GSM at 1800 MHz and 1900 MHz) Additional spectrum for coping with increasing number of subscribers (GSM1800) and for introduction of GSM in North America (GSM1900) GSM 1800: MHz (uplink) and MHz (downlink) GSM 1900: MHz (uplink) and MHz (downlink) GPRS (General Packet Radio Service) GSM Phase 2+ (2.5 G) Extension of GSM for packet-switched data transmission Introduction of a second, packet-witched core network, new software releases for existing access networks Utilizes unused channels of TDMA Increased data rates of kbps by multislot operation EDGE (Enhanced Data Rates for GSM Evolution) Based on 8-PSK modulation Achieves increased data rates of up to 48 kbps per time slot (compared to 14.4 kbps in conventional GSM) EGPRS (Enhanced General Packet Radio Service) GPRS mode based on EDGE 8

9 2.2 Global System for Mobile Communications GSM Network Architecture UE Access networks Core networks GERAN Circuit-switched domain BTS BSC MSC VLR GMSC PSTN/ISDN HLR EiR AuC User plane Comprises channels, protocols, and methods for carrying data originating from the user Examples for data transferred at the user plane: voice, , Web content, Control plane Comprises channels, protocols, and methods for carrying control data (signaling) Examples for control procedures: call/data session setup, handover, location update, paging, Internal channels users do not have access to the control plane Authentication Center Base Station Controller Base Transceiver Station enhanced NodeB Equipment Identity Register Gateway GPRS Support Node Gateway Mobile Switching Center General Packet Radio Service GSM/EDGE Radio Access Network Home Location Register Integrated Services Digital Network IP Multimedia Subsystem Long Term Evolution Mobile Switching Center Mobility Management Entity Public Switched Telephone Network Radio Network Controler Serving GPRS Support Node System Architecture Evolution Gateway UMTS Terrestrial Radio Access Network User Equipment Visitor Location Register User Plane Control Plane 9

10 2.2 Global System for Mobile Communications GSM User Equipment and SIM Mobile Station (MS) Used by mobile service subscribers for access to services, e.g., voice telephony, SMS, or browsing the Internet Contains the mobile equipment (transceiver, mechanisms for media access, coding,...) and the SIM Subscriber Identity Module (SIM) Personalization of mobile stations Provides separation of personal from terminal mobility (e.g., enabling international roaming independent of mobile equipment and network technology) Contains cryptographic algorithms to support authentication and user data encryption Storage of charging information, SMS, and telephone book Protection with a PIN against unauthorized access Network specific data (organization of air interface) SIM Application Toolkit (SAT): execution environment for operator specific functions 10

11 2.2 Global System for Mobile Communications GSM Access Network Base Station Subsystem (BSS) Consists of a Base Station Controller and one or more Base Transceiver Stations Base Transceiver Station (BTS) Defines a single radio cell with a radius of between 100m and 35 km (depending on the environment) Each BTS is allocated a set of frequencies (Cell Allocation, CA) Contains one or several radio antennas (each covering a cell sector), radio transceiver, and link to a base station controller In order to reduce complexity, signal and protocol processing is limited to error protection, encryption, and link level signaling (Link Access Procedure for the D-Channel, LAPD) BTS BTS BTS BSC Base Station Controller (BSC) Controls one or multiple BTS units and hence multiple cells Performs essential control functions and coordination between BTSs, e.g. Reservation of radio frequencies Management of handover from one cell to another within the same BSS Control of paging... BTS BTS BTS BSC 11

12 2.2 Global System for Mobile Communications GSM Core Network (I) Mobile Switching Center (MSC) Performs all switching functions of a fixed-network switching node (e.g. routing path search, signal routing, service feature processing) Difference between conventional fixed network switch and MSC: allocation and administration of radio resources and mobility of subscribers (supports location registration, handover between different BSCs,...) Support of service features like call forwarding or conference calls Signaling between MSCs and between MSCs and other logical entities accomplished by the Signal System No. 7 BSC BSC Gateway MSC MSC VLR GMSC HLR EiR AuC Passing of voice traffic between fixed and mobile networks Required as access to GSM network, because fixed network is unable to connect an incoming call to the local target MSC (due to its inability to interrogate the HLR) 12

13 2.2 Global System for Mobile Communications GSM Core Network (II) Home Location Register (HLR) Central database that stores both permanent as well as temporary information about each of the subscribers associated with the network BSC BSC MSC VLR GMSC HLR EiR AuC Visitor Location Register (VLR) Database containing distributed nodes, each being responsible for a certain coverage area Contains information about subscribers currently physically staying in the associated coverage area Usually combined with an MSC Other components SMS gateway WAP gateway... Authentication Center (AuC) Used for protecting user identity and data transmission Generates key for authentication and encryption Equipment Identity Register (EIR) Stores all device identification registered for this network Maybe used for detecting stolen devices 13

14 2.2 Global System for Mobile Communications GPRS (I) UE Access networks Core networks GERAN Circuit-switched domain BTS BSC MSC VLR GMSC PSTN/ISDN HLR EiR AuC Packet-switched domain IMS SGSN SGSN Internet Authentication Center Base Station Controller Base Transceiver Station enhanced NodeB Equipment Identity Register Gateway GPRS Support Node Gateway Mobile Switching Center General Packet Radio Service GSM/EDGE Radio Access Network Home Location Register Integrated Services Digital Network IP Multimedia Subsystem Long Term Evolution Mobile Switching Center Mobility Management Entity Public Switched Telephone Network Radio Network Controler Serving GPRS Support Node System Architecture Evolution Gateway UMTS Terrestrial Radio Access Network User Equipment Visitor Location Register User Plane Control Plane 14

15 2.2 Global System for Mobile Communications GPRS (II) GSM was initially designed for circuitswitched voice telephony MSCs operating in circuit-switched mode cannot be used for packet-switching Introduction of the packet-switched General Packet Radio Services (GPRS) for offering packet-switched data services Reuse of existing access networks Introduction of a new core network Colocation of SGSN and GGSN SGSN GGSN 1:1 relationship between SGSN and GGSN Gateway GPRS Support Node (GGSN) Gateway that provides mobile subscribers access to the Internet Counterpart to the circuit-switched GMSC Serving GPRS Support Node (SGSN) Connects the radio access network to the GPRS/UMTS core Tunnels user sessions to the GGSN Packet-switched counterpart to MSC SGSN n:m relationship between SGSN and GGSN SGSN GGSN IP Network GGSN GGSN SGSN 15

16 2.3 3G and 4G Networks 3G and 4G Overview (I) UMTS (Universal Mobile Telecommunications System) Standardized by the 3 rd Generation Partnership Project (3GPP), which also adopted responsibility for GSM Supports data rates between 100 kbps to 2 Mbps Medium access: CDMA Direct Sequence with a channel bandwidth of 5 MHz and 3.84 Mbps chipping rate FDD mode: MHz for uplink and for downlink TDD mode: MHz and MHz Also referred to as 3G network HSDPA (High-Speed Downlink Packet Access) and HSPA (High-Speed Packet Access) Advanced modulation schemes (16QAM and 64 QAM) for UMTS networks HSDPA: up to 4 Mbps for downlink HSPA: up to 7 Mbps for downlink and uplink HSPA+: Mbps for the downlink (to be achieved in combination with MIMO) Long Term Evolution 16

17 2.3 3G and 4G Networks 3G and 4G Overview (II) LTE (Long Term Evolution) Expected to go into operation around 2011 Data rates of up to 170 Mbps in the first expansion stage and up to 1 Gbps in an advanced stage Introduces multicarrier modulation (OFDM) and new antenna technology (MIMO) Referred to as 4G WiMAX (Worldwide Interoperability for Microwave Access) Specification for a 4G network that delivers high-speed broadband, fixed and mobile services wirelessly to large areas with much less infrastructure using IEEE standard Used of multicarrier modulation (OFDM) and Multiple-Input-Multiple-Output (MIMO) antennas (similar to LTE) 17

18 2.3 3G and 4G Networks Combined GSM/GPRS/UMTS Network Architecture UE Access networks Core networks GERAN Circuit-switched domain BTS BSC MSC VLR GMSC PSTN/ISDN HLR EiR AuC UE UTRAN NB RNC SGSN Packet-switched domain SGSN IMS Internet Authentication Center Base Station Controller Base Transceiver Station enhanced NodeB Equipment Identity Register Gateway GPRS Support Node Gateway Mobile Switching Center General Packet Radio Service GSM/EDGE Radio Access Network Home Location Register Integrated Services Digital Network IP Multimedia Subsystem Long Term Evolution Mobile Switching Center Mobility Management Entity Public Switched Telephone Network Radio Network Controler Serving GPRS Support Node System Architecture Evolution Gateway UMTS Terrestrial Radio Access Network User Equipment Visitor Location Register User Plane Control Plane 18

19 2.3 3G and 4G Networks UTRAN UMTS Terrestrial Access Network Node B (NB) Counterpart to GMS s BTS May be connected to several antennas Significant differences to BTSs regarding medium access (CDMA instead of FDMA/TDMA), power control, etc. UE is usually connected to several NBs simultaneously Node B was initially chosen as temporary name, which had to be replaced by a more appropriate term (never happened) Radio Network Controller (RNC) Counterpart to GSM s BSC Serves several NBs and is connected to circuit-switched/packet-switched core network Neighboring RNCs are direectly interconnected (higher complexity, but better handover control) NB NB NB NB NB NB RNC RNC UMTS Subscriber Identity Module (USIM) All features of conventional SIM Incread security features: integrity and mutual authentication UMTS SIM Application Toolkit (USAT): extension of SAT by additional computational power, more storage, and new capabilities 19

20 2.3 3G and 4G Networks Introduction of LTE UE Access networks Core networks GERAN Circuit-switched domain BTS BSC MSC VLR GMSC PSTN/ISDN HLR EiR AuC UE UTRAN NB RNC SGSN Packet-switched domain SGSN IMS E-UTRAN Evolved Packet Core Internet enb MME SAEGW Authentication Center Base Station Controller Base Transceiver Station enhanced NodeB Equipment Identity Register Gateway GPRS Support Node Gateway Mobile Switching Center General Packet Radio Service GSM/EDGE Radio Access Network Home Location Register Integrated Services Digital Network IP Multimedia Subsystem Long Term Evolution Mobile Switching Center Mobility Management Entity Public Switched Telephone Network Radio Network Controler Serving GPRS Support Node System Architecture Evolution Gateway UMTS Terrestrial Radio Access Network User Equipment Visitor Location Register User Plane Control Plane 20

21 2.3 3G and 4G Networks LTE Network Architecture LTE Architecture features Optimized architecture for the user plane: only two node types (enb and gateway) IP-based protocols on all interfaces Common gateway for all access technologies Split in the control/user plane between MME and SAEGW enb enb enb SAEGW MME System Architecture Evolution Gateway Routes and forwards user data packets Acts as mobility anchor for the user plane during inter-enb handover and as anchor for mobility between LTE and other 3GPP technologies Terminates downlink data path for idle Ues and triggers paging Mobility Management Entity (MME) Tracking of idle UEs Paging procedure and retransmission Bearer activation and deactivation Handover control Authentication 21

22 2.3 3G and 4G Networks Outlook UE Access networks GERAN BTS BSC Core networks UTRAN UE NB RNC SGSN Packet-switched domain E-UTRAN Evolved Packet Core Internet enb MME SAEGW Authentication Center Base Station Controller Base Transceiver Station enhanced NodeB Equipment Identity Register Gateway GPRS Support Node Gateway Mobile Switching Center General Packet Radio Service GSM/EDGE Radio Access Network Home Location Register Integrated Services Digital Network IP Multimedia Subsystem Long Term Evolution Mobile Switching Center Mobility Management Entity Public Switched Telephone Network Radio Network Controler Serving GPRS Support Node System Architecture Evolution Gateway UMTS Terrestrial Radio Access Network User Equipment Visitor Location Register 22

23 2.3 3G and 4G Networks WiMAX - Overview WiMAX Acronym for Worldwide Interoperability for Microwave Access Wireless transmission technology for multiple deployment scenarios Connceting WLAN access points to the Internet Providing a wireless alternative to cable and DSL for last mile broadband access Providing data and telecommunications services Providing portable connectivity Enabling large range mesh networks Institute of Electrical and Electronics Engineers 23

24 2.3 3G and 4G Networks Fixed WiMAX Designed only for "fixed" access Wireless transmission between stationary senders and receivers in outdoor environments Only suited for Line-of-Sight (LoS) transmission Released in December 2001 as IEEE Base stations: Located at cell sites of operator Subscriber stations Installed at the roofs of buildings Antenna dimensions similar to that satellite dishes Connected to local network(s) inside buildings Frequency range: GHz Bandwidth: 20, 25 or 28 MHz per radio channel Transmission range: < 70 km Data rates: < 134 Mbps (shared by all customers) Preferred mode of operation: point-topoint (P2P) transmission 24

25 2.3 3G and 4G Networks Nomadic WiMAX Serves nomadic customers Released in April 2003 as IEEE a Frequency bands: 2-11 GHz Bandwidth between 1.75 and 20 MHz Transmission range: approx. 5 km Data rates: < 70 Mbps (shared by all customers) Preferred mode of operation: Point-to-Multipoint (P2M) transmission Non-Line-of-Sight (NLoS) transmission WiMAX transceivers with integrated antennas connected to a PC or included into handheld devices or PCMCIA cards Customers can enter into contact with a base station from everywhere within its coverage area (even from the inside of buildings) No mobility support: service session can only be maintained as long as the customers remains in the coverage area of the serving base station Focus: alternative to DSL, cable modem and T1 access in rural areas Standardization of Fixed and Nomadic WiMAX merged into IEEE in June

26 2.3 3G and 4G Networks Mobile WiMAX Mobile WiMAX support of mobile customers Based on WiBRO (Korean standard for mobile broadband access) and IEEE Released as IEEE in November 2004 Portable access mode Serves customers traveling at pedestrian speeds Hard handover ("break before make") Short interruption of data transfer until handover is completed Mobile access mode Serves customers up to 125 km/h Soft handover ("make before break") No QoS degradations during handover Further mobility functions Location management Power saving modes Improved modulation and error correction 26

27 2.3 3G and 4G Networks WiMAX - Placement WLAN IEEE Similar to WiMAX WLAN is a pure access technology WLAN: small coverage area and low mobility support (hard handover between access points) Data rates: 54 Mbps (more than the WiMAX customer can expect) GSM/GPRS/UMTS High-level services and complex network infrastructure Mobility support by handover, location management, roaming (world-wide coverage) Low data rates (GPRS: 60 Kbps, UMTS: 384 Kbps -2 Mbps) WiMAX bridges the gap between WLAN (high data rates, but low mobility support) and cellular networks (low data rates, but high mobility support) Perhaps another access network technology for 4G networks 27

28 2.3 Local and Personal Networks WLAN/WiFi - Overview IEEE WLAN Set of standards for wireless area networks specified by IEEE Covers only physical and medium access layers Does not fix an entire network infrastructure with high-level services (like GSM), but is only an access technology Belongs to the group of 802.x LAN standards Ethernet Token Bus Token Ring Institute of Electrical and Electronics Engineers Defines multiple physical layers on infrared as well as radio basis with different transmission characteristics Offers the same interface as other IEEE 802.x standards to higher layers in order to maintain interoperability Operates in the license-free Industrial-Science-Medical (ISM) band at 2.4 GHz and at 5 GHz Different standards ( a/b/g/n) with different features and capabilities 28

29 2.4 Local and Personal Networks WLAN Standards (I) legacy Original version of released in 1997 and revised in or 2 Mbps at 2.4 GHz a Extended version using the 5 GHz band, but with the same MAC layer Higher frequency range allows for transmission rates of 54 Mbps b Data rates of up to 11 Mbps at 2.4 GHz, enabled by modified physical and MAC layer g Adopts the transmission technology of a to be used at 2.4 GHz 54 Mbps n Amendment for improving data throughput of other standards Multiple Input Multiple Output (MIMO) antennas Up to 300 Mbps 29

30 2.4 Local and Personal Networks WLAN Standards (II) b a g n Standard Approved Sept Sept June 2003? Available Bandwidth 83.5 MHz 580 MHz 83.5 MHz 83.5/580 MHz Frequency Band of Operation 2.4 GHz 5 GHz 2.4 GHz 2.4/5 GHz # Non-Overlapping Channels (US) /24 Data Rate per Channel 1 11 Mbps 6 54 Mbps 1 54 Mbps Mbps Modulation Type DSSS OFDM DSSS OFDM DSSS OFDM, MIMO 30

31 2.4 Local and Personal Networks Infrastructure versus Ad-Hoc in WLAN Infrastructure mode BSS1 Ad-hoc mode BSS2 WLAN IEEE IBSS BSS3 BSS 1 Extended Service Set (ESS) Wired LAN IEEE 802.x Wireless Local Area Networks May be operated in an infrastructure or ad hoc mode Infrastructure mode Single or few BSSs (=radio cells) operated by an access point Data transmission only between devices and access point Used to get access to networked services (e.g., Internet) Ad-hoc mode Direct transmission between devices Coverage area between 30 m and 300 m radius Designed for replacing wired technologies in office environments No mobility support 31

32 2.4 Local and Personal Networks WLAN Network Example Server Wired device Wireless device Infrastructure (802.3, Ethernet bus) Access point Application Application TCP TCP IP IP MAC MAC MAC MAC PHY PHY PHY PHY Radio 32

33 2.4 Local and Personal Networks Bluetooth Single-chip, low-cost, radio-based wireless network technology for connecting different small devices and/or peripherals in an ad-hoc manner, i.e., without expensive wiring or the need for a wireless infrastructure Standardized by the Bluetooth Special Interest Group (SIG), a consortium founded in spring 1998 by Ericsson, Intel, IBM, Nokia, and Toshiba Like WLAN , Bluetooth uses the license-free 2.4 GHz band Coverage range is limited to 10m (work on a version for 100m is in progress) Data rate: 720 kbps Adopted by the IEEE WPAN working group to be integrated into the IEEE standard for Wireless Personal Area Networks The specification is named after Harald Blatand, a tenth-century Danish Viking king. Unlike his Viking counterparts, King Harald had dark hair (thus the name Bluetooth, meaning a dark complexion). He is credited with bringing Christianity to Scandinavia along with uniting Denmark and Norway. The name was adopted because Bluetooth wireless technology is expected to unify the telecommunications and computing industry. The blue logo that identifies Bluetooth-enabled devices is derived from the runes of his initials. 33

34 2.4 Local and Personal Networks Bluetooth Network Topologies S M S S Piconet Piconet M S S M Piconet S S S M/S Piconet Piconet Scatternet M S S Piconet M Piconet Scatternet M/S Piconet S Piconet Basic unit of networking in Bluetooth Consists of a master (M) and up to seven slaves (S) Master coordinates medium access Slaves only communicate with the master and only when granted permission by the master Many piconets with overlapping coverage can exist simultaneously Scatternet Group of linked piconets joined by common devices Devices linking the piconets can be slaves on both piconets, or a master of one piconet and a slave of another (M/S) 34

35 2 Mobile Networks Data Rates versus Mobility Wired networks Data rate [MBit/s] Wireless LAN Bluetooth Indoor Long Term Evolution (LTE) UMTS & HSDPA/HSUPA GSM & EDGE GSM Outdoor Room Building Local National Global Mobility 35