Transcript Chapter3a

Chapter 3
Mobile Data Services and
Technologies
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Prof. Huei-Wen Ferng
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Mobile Data Services
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Contents
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The RAM/Mobitex mobile data service
The ARDIS/Modacom mobile data service
Cellular Digital Packet Data (CDPD)
Data over analog and digital cellular
Competing mobile data services
Paging and two-way paging
Comparison of paging and cellular
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The RAM/Mobitex Mobile Data Service
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This service is owned jointly by Bell
South and RAM in the US
Protocol was developed by Ericsson
Data rate
• 8 Kbps in the US ->19.2 Kbps (CDPD)
• 9.6 Kbps in the other parts of the world
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Some of early applications
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Point of sale where dial-up is not available:
MasterCard
Inventory control of rental cars: National Car
Rental
Train exchange yards: Conrail
Passenger check-in: British Airway
Field service: GE consumer service
Public safety: Chicago Parking Authority
Insurance claims
Transportation
E-mail
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Countries that installed Mobitex
networks
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Australia
Canada
Finland
Netherlands
Norway
Sweden
UK
US
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Rest of Europe
(later)
Latin America
(later)
The Pacific Rim
(later)
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What would you need to use the
RAM/Mobitex network
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Hardware
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• Radio
• Modem
• Terminal
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• Mobitex
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Application SW
• System integrators
• Software companies
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Network usage
Remark: the
combination unit of
radio and modem
is called Mobidem
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Specifications of Mobidem
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Portable wireless modem and radio
Connectible to RS-232 serial port
8 Kbps migrating to 19.2 Kbps
1 pound
3.3X2.68X7.87 in
Max transmit power: 2 W
>10 hours per battery charge
Support for nationwide roaming
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Operations of Mobitex
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The Mobidem automatically registers with
the nearest base station
The network is a store-and-forward
network
The Mobidem scans the network for
incoming messages
It alerts the user’s of incoming messages
The Mobidem stores the messages if the
terminal is not available
The network stores the messages if the
Mobidem is not available
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Subscription Type for the Hosts
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CCITT X.25
ISO/HDLC
SNA 3270
Mobitex asynchronous
communications
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Subscription Types for the Mobile
Terminal
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Continuous linkage to a particular
terminal
Personal subscription that is linked to
a person, not a terminal, in which
case the user logs in via name and
password
Group subscriptions that can consists
of mobile and fixed users
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Mobitex Partners
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IBM
HP
Motorola
Intel
Fujitsu
Ericsson
AT&T
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Developer and System Integrator
Partners
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DEC
Lotus
Novell
WordPerfect
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The ARDIS/Modacom Mobile Data
Service
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Countries have installed Modacom
• US
• Germany
• UK
• Hong Kong
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Data rate
• US: 4.8 Kbps -> 19.2 Kbps (CDPD)
• The other parts of the world: 9.6 Kbps
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Applications of Modacom
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Field techniques can access
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Dispatch info.
Diagnostic info.
Service history
Parts availability
• Obtain latest product
specifications
• Provide accurate price
quote
• Check product availability
• Make the order
Messenger service
• Receive and dispatch
messages while making
deliveries
• Notify customer that
delivery was done
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Salesperson can
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Additional applications
• Fleet management
• Insurance and financial
services
• Real time data
applications
• Point of sale (POS)
• Telemetry
• E-mail
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InfoTAC
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The radio and modem
combination
Specifications:
• Connects through RS232 port
• Receives, stores, and
responds to messages
• Canned responses can
be programmed
• 10 KB buffer
• Transmit power: 3 W
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• 6.8X3.3X3.3 inches
• 18 ounces
• 4X20 line backlit LCD
display
• 8 hours battery life
• Compatible with
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ARDIS/Modacom
RAM/Mobitex
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Cellular Digital Packet Data
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Consortium of companies
• IBM
• 6 of the 7 ROBCs (Regional Bell Operating
Companies)
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Ameritech Mobile Communications
Bell Atlantic Mobile Systems
NYNEX Mobile Communications
Pac Tel Cellular
Southwestern Bell Mobile Systems
US West New Vector Group
• McCaw Cellular Communications
• Contel Cellular
• GTE Mobile Communications
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Four CDPD Applications
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Transaction applications
Interactive applications
Broadcast applications
Multicast applications
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Transaction Applications
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Credit card
authorization/transacti
on
Package pickup,
delivery, and tracking
Fleet management
POS
Inventory control
Emergency services
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M-ES/vehicle theft
recovery
Display of calling
party name and
number
Notice of voice mail
E-mail
Information retrieval
services
Telemetry
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Examples of Telemetry
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Location service
Vehicle statistics
• Mileage
• Speed
• Engine status
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Burglar or fire alarm reporting
Vending machine status
Weather statistics
Traffic statistics
Field measurements
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Examples of Information Retrieval
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Weather report for a particular place
Traffic report for a specific area
Directory assistance: White pages
Local service assistance: Yellow
pages
Location and direction information
Restaurant reservation service
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Interactive and Broadcast Apps.
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Interactive: Remote access via direct
network connection or via a packet
assembly/disassembly
Broadcast
• News
• Sports
• Weather
• Advertising
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Multicast Applications
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A subscription to
obtain:
• Market info.
• Business news
• News related to a
specific area
• Classifieds for a
particular area
• Recreational info.
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A subscription to a
private bulletin to
obtain:
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Service bulletins
Company functions
Product info.
Fraud warnings
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Data over Analog and Digital
Cellular
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Data over analog cellular
• Data rate: up to 14.4 Kbps
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Data over digital cellular
• Data rate:
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Voice grade channel: 9.6 Kbps
GSM: 270 Kbps
Digital TDMA: 30 Kbps
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Competing Mobile Data Services
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Paging and Two-Way Paging
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Paging steps
• Someone dialing the page number
• Central controller broadcasts the page
to local controller
• Local controller broadcasts to base
stations
• Base station broadcasts to end users
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One-Way Paging
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One-Way Paging
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Two-Way Paging
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Two kinds
• Two-way asymmetrical paging networks
• Two-way symmetrical paging networks
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Spectrum: 900 MHz
Bandwidth: 50 MHz
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Asymmetrical Two-Way Paging
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Two separate networks:
• One for outgoing traffic
• The other for incoming traffic
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Incoming networks receives more
dense than the outgoing transmitters,
• e.g., a simple query may receive a
much longer response
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Asymmetrical Two-Way Paging
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Comparison of Paging to Cellular
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Paging is inexpensive, ubiquitous,
but with limited applications
It may become very powerful when
combined with a PDA because of its
simplicity
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Comparison of Paging to Cellular
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Mobile Data
Technologies
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Contents
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RAM/Mobitex network technologies
Motorola ARDIS/Modacom network
technologies
CDPD network technologies
Cell size classification
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RAM/Mobitex Network
Technologies
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It offered by Ericsson in most parts
of the world. In the US, it is jointly
owned by RAM and Bell South
The Network Control Center is the
heart of the network
Its protocol was developed by
Ericsson and is open
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Parameters (in the US)
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Tx. Frequency: 896-902 GHz
Rx. Frequency: 935-941 GHz
10-30 channel pairs in each
metropolitan area
Channel spacing: 12.5 KHz
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Air Interface
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ROSI: RadiO Signaling
0.3 GMSK: Gaussian Minimum Shift
Keying with BT=0.3
Block interleaving
16-bit CRC for error detection
Reduced Hamming code for error
correction
Selective Automatic Repeat Request
Channel access mechanism: reservation
slotted ALOHA
Collisions are detected by the lack of ACK
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The Terminal Interface (DLC)
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MASC: RAM/Mobitex Asynchronous
Communications
Handles data between the terminal
and Mobidem
Provides control and status
monitoring of the Mobidem
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The Network Layer
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MPAK
Max packet size of 512 bytes of info.,
plus header
24-bit addressing for the Mobitex
number
The transport layer protocol
• MTP/1
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Mobitex Packet
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Mobitex Protocol Layer
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Gateway Service
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Available via
• Mobitex directly: Mobigate
• The third party
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Mobigate to hosts
• TCP/IP
• X.25
• SNA 3270
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Third party gateways to hosts
• SNA
• AS 400
• DECNet
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ARDIS/Modacom Network
Technologies
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In most parts of world provided by Motorola:
called Modacom
In US: called ARDIS
ARDIS: separate company from IBM
The network intelligence is concentrated in the
hub
Hub is connected to the Radio Frequency Network
Control Points (RF NCP)
InfoTAC: the combination of radio and modem
MAC protocol: slotted ALOHA
25 KHz channel spacing
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The Terminal Interface
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MDC 4800, the original protocol
• 4.8 Kbps
• FSK
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RD LAP 19.2
• 19.2 Kbps
• Four level FSK
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RAM/Mobitex
• 8 Kbps
• GMSK
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The Terminal Interface (cont’d)
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The MDC 4800 protocol is quite
robust:
• Error detection and correction using 16
bits for 32 bits of info.
• Employing convolutional code: up 28%
of error correction
• Bits are interleaved
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CDPD Network Technologies
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The basic idea was proposed by a scientist at IBM, Dr. Vic Moore
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The Services Provided by CDPD
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19.2 Kbps
Connectionless service
Point-to-point
Multicast
Broadcast
Security
• Authentication of users
• Authorization
• Encryption of data
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CDPD Reference Model
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Functions of the Air Link Network
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Overlays existing cell site equipment
Accepts and forwards traffic to and from
M-ESs
Over the A-Interface
At the PHY and MAC layers
Manages channel allocation
Two types of air link channels (IS-533)
• MDBS to M-Es: forward/downlink
• M-Es to MDBS: reverse/uplink
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Data stream is assigned a Channel Stream
Identifier (CSI)
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Functions of MD-IS
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Uses and controls MDBSs
Control mobile data link
Manages mobility
Does not perform complex routing
decisions since they are included in
the function of the ISs
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Air Link Network
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Functions of IS
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Perform network layer functions
Route datagrams among F-ESs MD-ISs
Support
• Internet protocol (IP)
• Connectionless network protocol (CLNP)
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Can be composed of several
administrative domains
Connection oriented communications are
provided by transport layer in end system
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CDPD Switched Network
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Network Configuration
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CDPD Data Carriage Protocol
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MDLP: Mobile Data Link Protocol
SNDCP: Sub Network Dependent Convergence Protocol
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Cell Size Classification
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