An Overview of Wireless Data Communications

Wide Area Cellular Services

Wireless LANs

Satellite

Integrated Wireless Services

Richard PerlmanLucent Technologies

perl@lucent.com

Wide Area Cellular Services

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

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 GPRD)

• Some additional supplementary services also specified

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

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

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

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 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 - 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 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

CDMA BASICS• CDMA (Code Division Multiple Access) splits

calls into fragments and send them over different frequencies simultaneously

• The use of multiple frequencies gives CDMA effective protection against interference and lost calls

• CDMA supports true packet switching and does not use time slots, therefore is more bandwidth efficient than TDMA -- also a more direct path to 3G

• Current CDMA penetration in the world market is about 27%

3G CDMA Architecture

CDMA2000-1xEVDO System Architecture (Basic)• BTS: Base Station, which creates a single cell• BSC: Base Station Controller, which controls roaming and channel allocations amongst various

BSTs and is also referred to as a Radio Network Controller (RNC).• MSC: Mobile Switching Center, which performs the telephony switching functions and is

usually connected to an SS7 network.• PDSN: Packet Data Serving Node, maintains IP communications between all MNs and the

Packet Data Network (PDN), which in this diagram is the Internet.

Note: For simplicity, only the CDMA2000 architecture will be reviewed for this presentation

SOURCE: CDMA Development Group (CDG) 3G CDMA Architecture

BTW, the US didn’t pick ANY 2G standard--with predictable results

• The US allowed adoption of multiple wireless network technologies, including:– IS-95 CDMA (cdmaOne)– IS-136 TDMA– iDEN (Nextel)– GSM

• Unlike Europe and Japan, the US now lacks a dominant 2G standard – carriers and subscribers are using CDMA, TDMA, iDen, and GSM

Why do carriers want to move to 3G?

• Faster speeds--able to handle more calls

• Efficiencies in data handling– Integration with the Internet technology

• More capable, multi-media handsets and devices

• Global interoperability and roaming*

• Advanced services and more profitable revenue opportunities**

Some Urgent 3G Drivers

• Need to increase wireless data revenues and ARPU as voice prices decline

• Staggering investment already made in preparing for 3G upgrades

• Pressure by device makers and governments– 3G License clock ticking in Europe

• Dramatic success stories: – Korea, Japan markets are embracing 3G

• Fear of falling even further behind – Competition from WiFi as the high-speed alternative

Comparative Network Speeds

9.6

28.8

64

114

144

384

2000

2400

GSM/PDC

PDC-P

CDMA

GPRS

CDMA1xRTT

W-CDMAmoving

W-CDMAstationary

CDMA1xEV/DO

Theoretical data

transmission speedkbps

Source: ITU.

3G Systems Overview

3G MigrationSOURCE: CDMA Development Group (CDG) CDG Migration Diagram

Mobility Overview• Future mobility will be provided with

higher data rates and Ubiquitous access

– This implies the need for seamless wide area and office coverage

– Future remote access techniques will mirror existing to protect current investments

• Higher data rates and better coverage will be realized using disparate types of Wireless Technologies

– Mobility across disparate networks is a significant change to the paradigm of current mobile networks.

– Mobility is attributed to L2 and L1 abstraction through use of IP (Mobile IP).

Data Rates and Ranges of Wireless Technologies

SOURCE: ITU

3rd Generation Wireless Vision• Extends current data applications & devices• Enables breakthrough data services

Web Browsing

E-mail

E-Commerce

Telemetry

Vertical Solutions

Vehicle Location

Messaging

Full Web browsing

E-mail w/ Attachments

Richer E-Commerce

Multimedia Messaging

Streaming Audio & Video

Online Games

Video Telephony

Music Download

2nd Generation 3rd Generation

9.6 Kbps 28.8 Kbps 384 Kbps

Standards Evolution to 3G Worldwide

Japan Europe/Parts of Asia Americas/Parts of Asia

1st Gen TACS NMT/TACS/Other AMPS

2nd Gen PDC GSM TDMA CDMA

3rd Gen EDGE cdma2000W-CDMA/UMTS

Instead of solving the 2G network differences via 3G, we will continue to have W-CDMA and cdma2000 as separate networks. Both will be “optional implementation modes” in one 3G standard specification. Basic 3G phones will support one or the other. “Global phones” will be able to roam from one to the other.

cdma2000

Application PlatformsFor Cellular Networks

• WAP: discredited in first outing, but still alive and well as a backend mobile server standard

• SMS: proven worldwide but just emerging in US; limited to plain text messaging

• MMS: standard behind the exchange of pictures from camera phones; also for many audio and graphic formats

• iMode: proven in Japan; export still in doubt• J2ME (Java for mobile): large developer following

and handset deployment; confused business models• BREW: CDMA app platform: big in a few areas;

clearer business and distribution model

Overview of WAP

• WAP is an acronym for Wireless Application Protocol

• A WAP-enabled phone acts like a miniature browser – with obvious limitations on graphical display

• WAP content is marked up in WML – Wireless Markup Language

• Small client-side applications can be written in WMLScript (like JavaScript)

• Images are crude and delivered in wbmp format

WAP Architecture

WAP combines handset and server functionality:• The mobile device has embedded browser software •This browser connects to a WAP gateway and makes a request for information from a WAP- enabled web server• The content for wireless devices can be stored on any web server on the Internet, but the content must be formatted for the mobile device using WML

Early WAP Was Over-Sold

• Wireless Internet Browsing conveyed WWW on the phone—not what subscribers experienced

• Expected WAP to quickly become the “killer application” builder for mobile commerce– Hundreds of new companies and thousands of WAP

developers quickly went out of business instead

• Currently WAP is valued as infrastructure for delivering content and messaging to phones– Re-emerging as Internet enabled phone client

Evolution of messaging

Vers

ati

lity

of

Con

ten

t an

d U

ser

Ben

efi

ts

Time

Text

SMS

Text &Graphics

PictureMessaging

Digitalimageinput

MultimediaMessageService

Newcontenttypes

MobileMultimedia

Rich Call

Browsing

Messaging

SMS

SMS=Short Message Service=Current Worldwide “Killer Application”• A basic text messaging service for sending messages up to 160 characters to mobile phones• Runs on separate channel from voice traffic-much cheaper for operators to carry text messages (started out as free service in many countries)•Overwhelming user uptake in Europe and A/P --billions of messages sent each month; very profitable for carriers

0

10

20

30

40

50

60

0% 10% 20% 30% 40% 50% 60% 70% 80%Mobile Penetration

SM

Ss/s

ub

s/m

on

th

FinlandNorway

Germany

Italy

Portugal

GreeceUK

France

Sweden

Spain

SMS growth in Europe

i-Mode

•In 1999 Japanese wireless operator NTT DoCoMo decided to launch its own specially developed application environment for subscribers and to open its billing system to application providers • DoCoMo developed a programming language based on HTML (cHTML), set up the billing and distribution infrastructure and manufactured a new breed of application friendly handsets. •The service was branded as i-Mode

Importance of iMode Model• First to value the content/app provider part of the

business model--developers get the revenues for application usage (minus 9% for DoCoMo to handle billing)

• Enormous popularity with very large range of titles and applications developed

• Viewed as a potential model for Europe & US (investment in AT&T Wireless, launch with KPN)

J2ME and BREW ApplicationsWhy Run Locally on the Handset?

• Overcomes some of the issues with messaging applications

– No network/delivery delay in highly interactive apps like games

– User not worried about cost of airtime or message delivery; one-time fee for downloading easier to present to the marketplace

• Can use processing power of device to add speed, graphics, and logic support for richer user experience

• Simpler value chain for all players

New Phones Have MMS, WAP, Java (GSM) or

BREW (CDMA) – 400 million plus in 2003

What is J2ME?

• Java 2 Micro Edition– Optimized Java programming and execution for mobile

devices– CLDC: Connected Limited Device Configuration– MIDP: Mobile Information Device Profile

• Creates a Virtual Machine that runs programs on the device• Makes it easy for large Java programming community to

write mobile applications• Apps can be downloaded from carrier sites, Java portals, or

directly from developers• No consistent business model to support revenue collection

and marketplace management– Nokia provides a marketplace at Tradepoint, but no

testing and billing services

What is BREW?• Binary Runtime Environment for Wireless

– Also a sly poke at Java from its Qualcomm creators

• Like Java, BREW runs a virtual machine on the handset

– Allows user to download an application once from the wireless network and then interact with content without using air time

– Supports graphics, etc. to make it suitable for games and interactive apps

• Applications written in C or C++ (or even Java)

• Well-organized BREW business model created and maintained by Qualcomm

– Testing and “TrueBREW” certification for apps

– For 20% of app revenue, Qualcomm manages marketplace

Wireless LANs

Wireless LANs• Wireless LAN networks, including 802.11 or Wi-Fi,

are growing quickly for home and office applications• Unregulated frequency bands - Quality of Service not

guaranteed, but speed, low cost, and ease of implementation are compelling

• Very suitable for local data transmission and access outside operator networks - e.g. company internal solutions or home installations

• Being endowed with roaming capabilities and voice enabled devices to compete directly with carrier-owned networks

Wi-Fi

• Wireless Fidelity (Wi-Fi)

• IEEE 802.11b

• 50m range approximately

• Data rates vary– 11 - 56 Mb/s in theory

• Higher with some proprietary extensions

– 7 Mb/s is more realistic

• Walls can reduces range and throughput

• Number of users can reduce data rates

• WLANs are specified by IEEE 802.11 standards:• 802.11a: 5.8 GHz OFDM technology supporting typical ranges of 100m and 54

Mbps data rates.

• 802.11b: 2.4 GHz DSSS technology supporting typical ranges of 100m and 11 Mbps data rates.

• 802.11g: 2.4 GHz OFDM & DSSS technology supporting typical ranges of 100m and 54 Mbps data rates.

• 802.11i: MAC layer security using AES, 802.1x, and SHA…Expected draft for 2004

• 802.11e: QoS features in the air interface…Expected draft for 2004

• 802.11f: Inter Access Point Protocol (IAPP) for seamless interoperable roaming…Expected draft for 2005

RF &

MAC

Layer

MAC

Layer

Features

• All 802.11 standards can be used for Point-to-Point or Point-to-Multi-Point configurations

WLAN Overview

Wi-Fi Problems

• Security– Wi-Fi 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.

Satellite

Satellite TelephonyTYPE 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

Integrated Wireless Services

Future of Mobility

Architecture of Seamless Enterprise ConnectivitySource: CSC NTIS

IP Backbone/Internet

Multi-mode terminal w/MobileIP client& IPSec Client

PublicWLAN

802.11 Access Points

Ethernet

WLANGateway

& FA

802.11 Access Points

Ethernet

WLANGateway, HA, FA

Home AAA Server

Enterprise

Corporate LAN

VPNFirewall

PDSN/FA/HA/Firewall

CDMA WSP

PCF

BSBS

MSC/RNC

GGSN/FA/HA/Firewall

GSM/UMTSWSP

BS

BSC

SGSN

CGF

BS

Mobile devices can connect to office networks anytime from anywhere….

• Current mobility is based on single wireless technologies.

• Future will allow automatic configuration for seamless roaming amongst various wireless technologies…and, hence, greater coverage (ubiquitous).

WLAN-3G Integration Overview

There is not yet a defined standard architecture for 1x-EVDO WLAN Interworking via 3GPP2 (ITU CDMA2000 standards group), but loose integration is currently favored in preliminary drafts.

Loose integration makes most sense because it allows office WLAN, public hotspot WLAN, home WLAN, and operator WLAN access.

WLAN/3G Integration – Loose and Tight Methods SOURCE: Bell Labs IOTA 3G-WLAN IEEE Communications Publication

WLAN-3G Integration Overview

Two Types of Integration Services:

1. Simple IP Service: A mobile node (MN) acquires L2 authentication and then the WLAN gateway provides IP address. – This results in lost sessions from 1xEVDO to WLAN b/c of change of IP

address

– Not optimized to support mobility.

2. Mobile IP Service: User can roam heterogeneous networks.– Utilizes mobile IP to allow IP address to seem unchanged to higher layer

applications

– Optimized for mobility

WLAN-3G Integration- Mobile IP

Using Mobile IP for Handoffs Used for Seamless RoamingSOURCE: Bell Labs IOTA Project IOTA CDMA2000 WLAN Whitepaper IEEE Comms

IP Addressis

Constant

WLAN-3G Seamless Authentication

• Authentication across multiple technologies must be seamless• Client driver intelligence to determine when to switch entirely

from WLAN to CDMA, CDMA to WLAN, or WLAN to WLAN resulting in overhead usage but assuring higher layer sessions are kept active.– Software is responsible for Mobile IP on client

– Must support both interfaces (WLAN & 1x-EVDO) and corresponding access techniques: Office, Public Hotspot, Home, etc…

WLAN-3G Seamless Authentication

• Link security of interworking architecture must accommodate a mutual technique for authentication or client intelligence regarding which credentials to present for authentication.– For example: Client supporting hotspot proprietary access technique while

office access is determined via 802.1x. Client must realize which network it is trying to access, and then present the proper authentication credentials. Similarly, if accessing the 1xEV-DO network, it must present proper credentials.