An Overview of Wireless Data Communications

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An Overview of Wireless Data Communications

• Wide Area Cellular Services
• Wireless LANs
• Satellite
• Integrated Wireless Services

Richard Perlman Lucent Technologies perl_at_lucent.co
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Wide Area Cellular Services
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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!

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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

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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

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GSM Services - Phase 1
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GSM Services - Phase 2
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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
  specified

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Architecture of a GSM Network
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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

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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

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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

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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)

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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

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Integrating GPRS
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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.

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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

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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

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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

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EDGE - NSS

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

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3G - UMTS
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UMTS - MS

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

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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

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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

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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

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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

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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

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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

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Comparative Network Speeds
Source ITU.
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3G Systems Overview
3G Migration SOURCE CDMA Development Group (CDG)
CDG Migration Diagram
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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
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3rd Generation Wireless Vision

• Extends current data applications devices
• Enables breakthrough data services

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Standards Evolution to 3G Worldwide
Japan
Europe/Parts of Asia
Americas/Parts of Asia
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.
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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

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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

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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

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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

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Evolution of messaging
Rich Call
Browsing
Messaging
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SMS

• 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
  countries)
• Overwhelming user uptake in Europe and A/P
  --billions of messages sent each month very
  profitable for carriers

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SMS growth in Europe
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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

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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)

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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

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New Phones Have MMS, WAP, Java (GSM) or BREW
(CDMA) 400 million plus in 2003
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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

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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

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Wireless LANs
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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

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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

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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
  2005

RF MAC Layer
MAC Layer Features

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

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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

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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

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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.

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Satellite
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Satellite Telephony
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Integrated Wireless Services
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Future of Mobility

• Current mobility is based on single wireless
  technologies.
• Future will allow automatic configuration for
  seamless roaming amongst various wireless
  technologiesand, hence, greater coverage
  (ubiquitous).

Mobile devices can connect to office networks
anytime from anywhere.

• Architecture of Seamless Enterprise Connectivity
• Source CSC NTIS

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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.
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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
  networks.
• Utilizes mobile IP to allow IP address to seem
  unchanged to higher layer applications
• Optimized for mobility

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WLAN-3G Integration- Mobile IP
IP Address is Constant

• Using Mobile IP for Handoffs Used for Seamless
  Roaming
• SOURCE Bell Labs IOTA Project IOTA CDMA2000 WLAN
  Whitepaper IEEE Comms

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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

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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.