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									An Overview of Wireless
 Data Communications

    Wide Area Cellular Services
           Wireless LANs
    Integrated Wireless Services
           Richard Perlman
         Lucent Technologies
Wide Area Cellular
           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
   –   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
• Some residual interference from co-channel
• Handover procedure required
               GSM Services - Phase 1

 Service Category                 Service                      Comments
     Teleservices                 Speech                      Full Rate 13Kbps
                                 Emergency             Point to Point & Cell Broadcast
                         SMS (Short Message Service)
                                Group 3 Fax
   Bearer Services          Asynchronous Data                   300 – 9600bps
                             Synchronous Data                   300 – 9600bps
Supplementary Services          Call Forward           Subscriber Busy, Not Reachable
                                Call Barring           International & Incoming Calls
               GSM Services - Phase 2
 Service Category                    Service                          Comments
     Teleservices                     Speech                         Half Rate 6.5Kbps
                                    Emergency                 Point to Point & Cell Broadcast
                           SMS (Short Message Service)
                                    Group 3 Fax
   Bearer Services        Synchronous Packet Data Access             2400 – 9600bps
Supplementary Services    CLI (Calling Line Identification)
                                    Call Waiting
                                     Call Hold
                         USSD (Unstructured Supplementary
                                   Service Data)
                                 Operator Barring
                                 Advice 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
Architecture of a GSM Network
                      Base Station
                                                Network Subsystem
  Mobile Station       Subsystem                                              Other Networks

                                         MSC/                GMSC
                             BSC         VLR

                                          EIR          HLR          AUC


                                     Note: Interfaces have been omitted for clarity purposes.
          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
                                    Base Station
                                                                 Network Subsystem
           Mobile Station            Subsystem                                                 Other Networks

                                                          MSC/                GMSC
                                             BSC          VLR                                     PSTN

                                                           EIR          HLR          AUC

                                                                              GGSN                Internet

                                                   Note: Interfaces have been omitted for clarity purposes.
                 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
                           Base Station
                                                         Network Subsystem
       Mobile Station       Subsystem                                                  Other Networks

                                                  MSC/                GMSC
                                    BSC           VLR                                      PSTN

                                                   EIR          HLR          AUC           PLMN

                         Node        RNC                                                  Internet
                ME        B


                                           Note: Interfaces have been omitted for clarity purposes.
               UMTS - MS
• User Equipment
  – Mobile Equipment

  – 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
• 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 Internet.
   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
• Faster speeds--able to handle more calls
• Efficiencies in data handling
  – Integration with the Internet technology
• More capable, multi-media handsets and
• 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

      GPRS      114
      CDMA      64           data
     PDC-P      28.8        speed
  GSM/PDC       9.6                    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
   – 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
                                       Data Rates and Ranges of Wireless
   – Mobility across disparate                    Technologies
     networks is a significant                     SOURCE: ITU

     change to the paradigm of
     current mobile networks.
   – Mobility is attributed to L2
     and L1 abstraction through
     use of IP (Mobile IP).
    3rd Generation Wireless Vision
• Extends current data applications & devices
• Enables breakthrough data services

       2nd Generation                            3rd Generation

              Web Browsing         Full Web browsing    Streaming
                                                        Audio & Video
              E-mail               E-mail w/
                                   Attachments          Online Games
                                   Richer               Video
              Telemetry            E-Commerce           Telephony

              Vertical Solutions   Multimedia           Music Download
Messaging                          Messaging
              Vehicle Location
   9.6 Kbps                  28.8 Kbps                      384 Kbps
             Standards Evolution to 3G
              Japan        Europe/Parts of Asia        Americas/Parts of Asia

1st Gen        TACS           NMT/TACS/Other                   AMPS

2nd Gen         PDC                GSM                 TDMA            CDMA

3rd Gen       W-CDMA/UMTS         cdma2000             EDGE          cdma2000

  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 Platforms
         For 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
• 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
  •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
    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
            Versatility of Content and User Benefits
Rich Call


Browsing                                                       Picture     Service

                                                       Text    Text &      Digital        New
                                                              Graphics      image       content
Messaging                                                                   input        types

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
                           SMS growth in Europe


                                                            UK           Italy
                      0%   10%   20%       30%         40%      50%        60%   70%       80%
                                                 Mobile Penetration
•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 AT&T Wireless, launch with KPN)
  J2ME and BREW Applications
 Why Run Locally on the Handset?
• Overcomes some of the issues with messaging
   – No network/delivery delay in highly interactive apps like
   – 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
     – 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
•   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.
RF &
           • 802.11b: 2.4 GHz DSSS technology supporting typical ranges of 100m and 11 Mbps
Layer        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
Features   • 802.11f: Inter Access Point Protocol (IAPP) for seamless interoperable
             roaming…Expected draft for 2005

  • All 802.11 standards can be used for Point-to-Point or Point-to-
    Multi-Point configurations
             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
• 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
     TYPE           Altitude            Characteristics             Examples
      GEO           35,800km       Large coverage footprint        INMARSAT
(Geosynchronous                    Small number of satellites
  Earth Orbit)                     Large propagation delay
                                   High power requirements
      LEO           Between        Small coverage footprint          Iridium
(Low Earth Orbit)   500km and      Larger number of satellites      GlobalStar
                     1500km        Faster response time
                                   Low power requirements
                                   Short life span of satellites
                                    (due to increased radiation
                                    at low altitudes)
     MEO            Between     Essentially    a    compromise        Odyssey
 (Medium Earth       5000km     between       GEO       and   LEO       ICO
     Orbit)            and      satellites with the respective
                    12000km     advantages and disadvantages
                                being affected accordingly.
Integrated Wireless
                                         Future of Mobility
                                              Enterprise                                         • Current mobility is based on
                                                                         Home AAA Server
                                                                                                   single wireless technologies.
                  Gateway,                                                                       • Future will allow automatic
                   HA, FA                                                                          configuration for seamless
                                                         Corporate LAN
                             Ethernet                                                              roaming amongst various
                                                                                                   wireless technologies…and,
                                                                                                   hence, greater coverage
                                  802.11 Access Points                                             (ubiquitous).

                                                                   IP Backbone/
                 CDMA WSP                                                                                              WSP
    ewall                                            WLAN                                              GGSN/FA/HA/
                                                    Gateway                           Public             Firewall
                                                     & FA                             WLAN                                        SGSN
                   BS                                                                                                BS          CGF
                             BS                                  802.11 Access                                              BS

    Mobile devices can                                                                     Multi-mode terminal
    connect to office networks                                                              w/MobileIP client
    anytime from anywhere….                                                                  & IPSec Client

    Architecture of Seamless Enterprise Connectivity
   WLAN-3G Integration Overview

                         WLAN/3G Integration – Loose and Tight Methods
                           SOURCE: Bell Labs IOTA 3G-WLAN IEEE 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
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
   –   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
   –   Optimized for mobility
   WLAN-3G Integration-
       Mobile IP

                  IP Address

Using Mobile IP for Handoffs Used for Seamless
           WLAN-3G Seamless
• 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
• 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

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