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1

Mobile Services (ST 2010)Chapter 2: Mobile Networks

Axel Küpper

Service-centric NetworkingDeutsche Telekom Laboratories, TU Berlin

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Mobile ServicesSummer Term 2010

2 Mobile Networks2.1 Infrastructure versus Ad-Hoc Networks

2.2 Global System for Mobile Communications

2.3 3G and 4G Networks

2.4 Local and Personal Networks

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2.1 Infrastructure versus Ad-hoc NetworksInfrastructure-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

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AP

AP

AP AP

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2.1 Infrastructure versus Ad-hoc NetworksInfrastructure-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

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A

BC

AP

APAP

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2.1 Infrastructure versus Ad-hoc NetworksInfrastructure-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

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2.1 Infrastructure versus Ad-hoc NetworksAd-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)

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2.2 Global System for Mobile CommunicationsGSM 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

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2.2 Global System for Mobile CommunicationsGSM 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)

GPRS mode based on EDGE

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2.2 Global System for Mobile CommunicationsGSM 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 NetworkHome Location RegisterIntegrated Services Digital NetworkIP Multimedia SubsystemLong Term EvolutionMobile Switching CenterMobility Management Entity

Authentication CenterBase Station ControllerBase Transceiver Stationenhanced NodeBEquipment Identity RegisterGateway GPRS Support NodeGateway Mobile Switching CenterGeneral Packet Radio Service

Public Switched Telephone NetworkRadio Network ControlerServing GPRS Support NodeSystem Architecture Evolution GatewayUMTS Terrestrial Radio Access NetworkUser Equipment Visitor Location Register

User PlaneControl 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,… Internal channels – users do not have access to the control plane

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2.2 Global System for Mobile CommunicationsGSM 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

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BSC

BTS

BTS

BTS

2.2 Global System for Mobile CommunicationsGSM 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

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2.2 Global System for Mobile CommunicationsGSM 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 AuCHLR

BSC

BSC

MSC VLR GMSC

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2.2 Global System for Mobile CommunicationsGSM 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 AuCHLR

BSC

BSC

MSC VLR GMSC

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2.2 Global System for Mobile CommunicationsGPRS (I)

GERAN

Packet-switched domain

Circuit-switched domain

PSTN/ISDN

IMS

Internet

EiR AuC

UE

Access networks Core networks

BTS MSC VLR GMSC

HLR

SGSN

BSC

SGSN

GSM/EDGE Radio Access NetworkHome Location RegisterIntegrated Services Digital NetworkIP Multimedia SubsystemLong Term EvolutionMobile Switching CenterMobility Management Entity

Authentication CenterBase Station ControllerBase Transceiver Stationenhanced NodeBEquipment Identity RegisterGateway GPRS Support NodeGateway Mobile Switching CenterGeneral Packet Radio Service

Public Switched Telephone NetworkRadio Network ControlerServing GPRS Support NodeSystem Architecture Evolution GatewayUMTS Terrestrial Radio Access NetworkUser Equipment Visitor Location Register

User PlaneControl Plane

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2.2 Global System for Mobile CommunicationsGPRS (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

SGSNGGSN

Colocation of SGSN and GGSN

IPNetwork

SGSN

SGSN

GGSN

GGSN

n:m relationship between SGSN and GGSN

1:1 relationship between SGSN and GGSN

GGSNSGSN

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2.3 3G and 4G Networks3G 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

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2.3 3G and 4G Networks3G 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) antennas (similar to LTE)

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2.3 3G and 4G NetworksCombined GSM/GPRS/UMTS Network Architecture

GERAN

Packet-switched domainUTRAN

Circuit-switched domain

PSTN/ISDN

IMS

Internet

EiR AuC

UE

UE

Access networks Core networks

BTS MSC VLR GMSC

HLR

NB SGSN

BSC

RNC SGSN

GSM/EDGE Radio Access NetworkHome Location RegisterIntegrated Services Digital NetworkIP Multimedia SubsystemLong Term EvolutionMobile Switching CenterMobility Management Entity

Authentication CenterBase Station ControllerBase Transceiver Stationenhanced NodeBEquipment Identity RegisterGateway GPRS Support NodeGateway Mobile Switching CenterGeneral Packet Radio Service

Public Switched Telephone NetworkRadio Network ControlerServing GPRS Support NodeSystem Architecture Evolution GatewayUMTS Terrestrial Radio Access NetworkUser Equipment Visitor Location Register

User PlaneControl Plane

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2.3 3G and 4G NetworksUTRAN – 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

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2.3 3G and 4G NetworksIntroduction of LTE

GERAN

Packet-switched domain

Evolved Packet CoreE-UTRAN

UTRAN

Circuit-switched domain

PSTN/ISDN

SAEGW

IMS

Internet

EiR AuC

UE

UE

Access networks Core networks

eNB

BTS MSC VLR GMSC

HLR

NB SGSN

MME

BSC

RNC SGSN

GSM/EDGE Radio Access NetworkHome Location RegisterIntegrated Services Digital NetworkIP Multimedia SubsystemLong Term EvolutionMobile Switching CenterMobility Management Entity

Authentication CenterBase Station ControllerBase Transceiver Stationenhanced NodeBEquipment Identity RegisterGateway GPRS Support NodeGateway Mobile Switching CenterGeneral Packet Radio Service

Public Switched Telephone NetworkRadio Network ControlerServing GPRS Support NodeSystem Architecture Evolution GatewayUMTS Terrestrial Radio Access NetworkUser Equipment Visitor Location Register

User PlaneControl Plane

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2.3 3G and 4G NetworksLTE 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

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2.3 3G and 4G NetworksOutlook

GSM/EDGE Radio Access NetworkHome Location RegisterIntegrated Services Digital NetworkIP Multimedia SubsystemLong Term EvolutionMobile Switching CenterMobility Management Entity

Authentication CenterBase Station ControllerBase Transceiver Stationenhanced NodeBEquipment Identity RegisterGateway GPRS Support NodeGateway Mobile Switching CenterGeneral Packet Radio Service

Public Switched Telephone NetworkRadio Network ControlerServing GPRS Support NodeSystem Architecture Evolution GatewayUMTS Terrestrial Radio Access NetworkUser Equipment Visitor Location Register

GERAN

Packet-switched domain

Evolved Packet CoreE-UTRAN

UTRAN

SAEGW

Internet

UE

UE

Access networks Core networks

eNB

BTS

NB

MME

BSC

RNC SGSN

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2.3 3G and 4G NetworksWiMAX - 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

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2.3 3G and 4G NetworksFixed 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 IEEE802.16

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

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2.3 3G and 4G NetworksNomadic 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 allcustomers)

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

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2.3 3G and 4G NetworksMobile 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

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2.3 3G and 4G NetworksWiMAX - 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

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2.3 Local and Personal NetworksWLAN/WiFi - Overview

IEEE WLAN 802.11

Set of standards for wireless area networksspecified by IEEE

Covers only physical and medium accesslayers

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

Institute of Electrical and Electronics Engineers

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2.4 Local and Personal NetworksWLAN 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

Up to 300 Mbps

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2.4 Local and Personal NetworksWLAN Standards (II)

802.11b 802.11a 802.11g 802.11n

Standard Approved Sept. 1999 Sept. 1999June 2003

?

Available Bandwidth 83.5 MHz 580 MHz 83.5 MHz83.5/580

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 OFDMDSSS

OFDM

DSSSOFDM,MIMO

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2.4 Local and Personal NetworksInfrastructure 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

BSS1

BSS1

WLAN IEEE 802.11

Extended Service Set (ESS)

IEEE 802.x

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2.4 Local and Personal NetworksWLAN 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)

Access point

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2.4 Local and Personal NetworksBluetooth

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.

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2.4 Local and Personal NetworksBluetooth 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 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)

Piconet PiconetPiconet

MS M SS

M

S S S

Piconet Piconet

Pico-net

Scatternet

M/SM SS

SPiconet Piconet

Scatternet

M/S MS

S

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2 Mobile NetworksData Rates versus Mobility

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Long Term Evolution (LTE)

UMTS & HSDPA/HSUPA

GSM

Data rate [MBit/s]

Mobility

1.0

100.0

10.0

0.1

0.01

GSM & EDGE

Blue-

tooth

Wireless

LAN 802.11

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