Mobile Services (ST 2010)

(1)

Mobile Ser vice s – ST 20 10 | 2 Mobile N etw or ks Axe l Kü p p er | T ech n is ch e U n iv ers itä t Be rlin | Se rv ice -ce n tric N etwork in g

Mobile Services (ST 2010)

Chapter 2: Mobile Networks

Axel Küpper

Service-centric Networking

(2)

Mobile Services

Summer Term 2010

2 Mobile Networks

2.1 Infrastructure versus Ad-Hoc Networks

2.2 Global System for Mobile Communications

2.3 3G and 4G Networks

(3)

2.1 Infrastructure versus Ad-hoc Networks

Infrastructure-based Networks (II)

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

satellite-based cellular telephony parts of the infrastructure (i.e., the satellites) operate wirelessly) Network infrastructure 4 4 AP AP AP AP _AP

(4)

2.1 Infrastructure versus Ad-hoc Networks

Infrastructure-based Networks (I)

 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 Network infrastructure 4 4

A

B

C

AP AP AP

(5)

2.1 Infrastructure versus Ad-hoc Networks

Infrastructure-based Networks (III)

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

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

 Support of application services (i.e., services above connectivity services)

AP AP AP AP AP AP

(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)

(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 890-915 MHz for uplink and 935-960 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 880-915 MHz (uplink) and 925-960 MHz (downlink)  Additional 10 MHz provides additional 50 frequency channels

(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: 1710-1785 MHz (uplink) and 1805-1880 MHz (downlink)  GSM 1900: 1850-1910 MHz (uplink) and 1930-1990 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 50-60 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)

(9)

2.2 Global System for Mobile Communications

GSM Network Architecture

GERAN Circuit-switched domain

PSTN/ISDN EiR AuC

UE

Access networks Core networks

BTS MSC VLR GMSC

HLR BSC

GSM/EDGE Radio Access Network Home Location Register

Integrated Services Digital Network IP Multimedia Subsystem

Long Term Evolution Mobile Switching Center Mobility Management Entity 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

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

User plane

 Comprises channels, protocols, and methods for carrying data originating from the user

 Examples for data transferred at the user plane: voice, email, 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,…

(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

(11)

Mobile Ser vice s – ST 20 10 | 2 Mobile N etw or ks Axe l Kü p p er | T ech n is ch e U n iv ers itä t Be rlin | Se rv ice -ce n tric N etwork in g BSC BTS BTS BTS

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)

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  ... BSC BTS BTS BTS

(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

Gateway MSC

 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) EiR AuC HLR BSC BSC MSC VLR GMSC

(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

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 EiR AuC

HLR BSC

BSC

(14)

2.2 Global System for Mobile Communications

GPRS (I)

GERAN Packet-switched domain Circuit-switched domain PSTN/ISDN IMS Internet EiR AuC UE

BTS MSC VLR GMSC

HLR

SGSN BSC

SGSN

(15)

2.2 Global System for Mobile Communications

GPRS (II)

 GSM was initially designed for circuit-switched 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

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 GGSN

Colocation of SGSN and GGSN

IP Network SGSN SGSN GGSN GGSN

n:m relationship between SGSN and GGSN

1:1 relationship between SGSN and GGSN

GGSN SGSN

(16)

2.3 3G and 4G Networks

3G and 4G Overview (I)

UMTS (Universal Mobile Telecommunications System)

 Standardized by the 3rd _{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: 1920-1980 MHz for uplink and 2110-2170 for downlink  TDD mode: 1900-1920 MHz and 2010-2025 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+: 28-84 Mbps for the downlink (to be achieved in combination with MIMO)  Long Term Evolution

(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 802.16 standard  Used of multicarrier modulation (OFDM) and Multiple-Input-Multiple-Output (MIMO)

(18)

2.3 3G and 4G Networks

Combined GSM/GPRS/UMTS Network Architecture

GERAN Packet-switched domain UTRAN Circuit-switched domain PSTN/ISDN IMS Internet EiR AuC UE UE

BTS MSC VLR GMSC

HLR

NB SGSN

BSC

RNC SGSN

(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)

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 RNC NB NB NB RNC NB NB NB

(20)

2.3 3G and 4G Networks

Introduction of LTE

GERAN Packet-switched domain

Evolved Packet Core E-UTRAN UTRAN Circuit-switched domain PSTN/ISDN SAEGW IMS Internet EiR AuC UE UE

eNB BTS MSC VLR GMSC HLR NB SGSN MME BSC RNC SGSN

(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

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 eNB eNB eNB SAEGW MME

(22)

2.3 3G and 4G Networks

Outlook

GERAN

Packet-switched domain

Evolved Packet Core E-UTRAN UTRAN SAEGW Internet UE UE

eNB BTS NB MME BSC RNC SGSN

(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

(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 802.16

 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: 10 - 66 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-to-point (P2P) transmission

(25)

2.3 3G and 4G Networks

Nomadic WiMAX

 Serves nomadic customers

 Released in April 2003 as IEEE 802.16a  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 802.16-2004 in June 2004

(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 802.16-2004

 Released as IEEE 802.16 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

(27)

2.3 3G and 4G Networks

WiMAX - Placement

WLAN IEEE 802.11

 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

(28)

2.3 Local and Personal Networks

WLAN/WiFi - Overview

IEEE WLAN 802.11

 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  802.3 Ethernet

 802.4 Token Bus  802.5 Token Ring

 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 (802.11 a/b/g/n) with different features and capabilities

(29)

2.4 Local and Personal Networks

WLAN Standards (I)

802.11 legacy

 Original version of 802.11 released in 1997 and revised in 1999  1 or 2 Mbps at 2.4 GHz

802.11a

 Extended version using the 5 GHz band, but with the same MAC layer  Higher frequency range allows for transmission rates of 54 Mbps

802.11b

 Data rates of up to 11 Mbps at 2.4 GHz, enabled by modified physical and MAC layer

802.11g

 Adopts the transmission technology of 802.11a to be used at 2.4 GHz

 54 Mbps

802.11n

 Amendment for improving data throughput of other 802.11 standards  Multiple Input Multiple Output (MIMO) antennas

(30)

2.4 Local and Personal Networks

WLAN Standards (II)

802.11b 802.11a 802.11g 802.11n

Standard Approved Sept. 1999 Sept. 1999 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) 3 24 3 3/24

Data Rate per Channel 1 – 11 Mbps 6 – 54 Mbps 1 – 54 Mbps 1 – 600 Mbps

Modulation Type DSSS OFDM DSSS

OFDM

DSSS OFDM,

(31)

2.4 Local and Personal Networks

Infrastructure versus Ad-Hoc in WLAN

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

IBSS

Infrastructure mode

Ad-hoc mode

Wired LAN BSS3 BSS2

BSS

₁

BSS1

WLAN IEEE 802.11

Extended Service Set (ESS)

(32)

2.4 Local and Personal Networks

WLAN Network Example

Radio 802.11 PHY 802.11 MAC IP TCP Application 802.3 PHY 802.3 MAC IP TCP Application 802.3 PHY 802.3 MAC 802.11 PHY 802.11 MAC Wireless device

Server Wired device

Infrastructure (802.3, Ethernet bus)

(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 802.11, 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 802.15 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.

(34)

2.4 Local and Personal Networks

Bluetooth Network Topologies

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

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)