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An Overview of Wireless Data Communications


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Title: An Overview of Wireless Data Communications

An Overview of Wireless Data Communications
  • Wide Area Cellular Services
  • Wireless LANs
  • Satellite
  • Integrated Wireless Services

Richard Perlman Lucent Technologies
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
GSM Services - Phase 2
GSM Services - Phase 2
  • Primarily concerned with the improvement of
    Bearer (data!) services
  • Full data rate _at_ 14.4 kb/s
  • High Speed Circuit Switched Data (HSCSD)
  • General Packet Radio Service GPRD)
  • Some additional supplementary services also

(No Transcript)
Architecture of a GSM Network
Mobile Station (MS)
  • Mobile Equipment
  • Fixed
  • Portable
  • International Mobile Equipment Identity (IMEI)
  • Subscriber Identity Module (SIM)
  • Personal Identification Number (PIN)
  • International Mobile Subscriber Identity (IMSI)
  • 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
  • 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.

  • 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
  • Details of data services added to HLR

GPRS - Summary
  • Data capacity increased considerably
  • Depending on configuration
  • _at_ 14.4 kb/s per channel, 115.2 kb/s achieved
  • _at_ 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

  • Minimum impact on the core network
  • SGSN GGSN practically independent of data rates
  • Some minor software upgrades

  • User Equipment
  • Mobile Equipment
  • Air interface
  • UMTS Terrestrial Radio Access (UTRA)
  • W-CDMA

  • 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 (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
  • 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
  • Note For simplicity, only the CDMA2000
    architecture will be reviewed for this
  • SOURCE CDMA Development Group (CDG) 3G CDMA

BTW, the US didnt 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

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

Comparative Network Speeds
Source ITU.
3G Systems Overview
3G Migration SOURCE 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
  • 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

Standards Evolution to 3G Worldwide
Europe/Parts of Asia
Americas/Parts of Asia
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.
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
  • A WAP-enabled phone acts like a miniature browser
    with obvious limitations on graphical display
  • WAP content is marked up in WML Wireless Markup
  • 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
  • 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
    phonenot 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
Rich Call
  • SMSShort Message ServiceCurrent 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
  • Overwhelming user uptake in Europe and A/P
    --billions of messages sent each month very
    profitable for carriers

SMS growth in Europe
  • 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
  • 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 ATT Wireless, launch with KPN)

J2ME and BREW ApplicationsWhy Run Locally on the
  • Overcomes some of the issues with messaging
  • 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
  • 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
  • Like Java, BREW runs a virtual machine on the
  • 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

Wireless LANs
Wireless LANs
  • Wireless LAN networks, including 802.11 or Wi-Fi,
    are growing quickly for home and office
  • 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

  • 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

WLAN Overview
  • 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 SHAExpected draft for 2004
  • 802.11e QoS features in the air
    interfaceExpected draft for 2004
  • 802.11f Inter Access Point Protocol (IAPP) for
    seamless interoperable roamingExpected draft for

RF MAC Layer
MAC Layer Features
  • All 802.11 standards can be used for
    Point-to-Point or Point-to-Multi-Point

Wi-Fi Problems
  • Security
  • Wi-Fi was not designed with robust security in
  • Interference
  • operates in unlicensed 2.4 GHz spectrum
  • competes with other products e.g microwave ovens!
  • Scarcity of hotspots

  • 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 Telephony
Integrated Wireless Services
Future of Mobility
  • Current mobility is based on single wireless
  • Future will allow automatic configuration for
    seamless roaming amongst various wireless
    technologiesand, hence, greater coverage

Mobile devices can connect to office networks
anytime from anywhere.
  • Architecture of Seamless Enterprise Connectivity
  • Source CSC NTIS

WLAN-3G Integration Overview
WLAN/3G Integration Loose and Tight Methods
Communications Publication
  • 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 Overview
  • Two Types of Integration Services
  • 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.
  • Mobile IP Service User can roam heterogeneous
  • Utilizes mobile IP to allow IP address to seem
    unchanged to higher layer applications
  • Optimized for mobility

WLAN-3G Integration- Mobile IP
IP Address is Constant
  • Using Mobile IP for Handoffs Used for Seamless
  • SOURCE Bell Labs IOTA Project IOTA CDMA2000 WLAN
    Whitepaper IEEE Comms

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.