Transcript Comparison Of Wireless Data Networks

Comparison Of Wide Area
Wireless Data Networks
-Selling
-By
The GPRS Standard
Pranav S. Vaidya
Sales Scenario
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Client has USD 100 M to invest
Client is considering the following wireless data
standards. Hence client is interested in wireless
data networks more than wireless voice
networks.
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ARDIS … The Oldest One (1G)
MOBITEX … The Most Widely Used (1,2G)
CDPD …The Smart One
GPRS … The New One
Not considering other broadband standards such
as MetriComm Richochet.
Evaluation Criterion Of
Technologies
Data transmission Characteristics.
Transmission Costs.
Throughput – Faster Throughput
Cost Of Service
1.
2.
3.
4.
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Customer Satisfaction – Roaming.
Interoperability with the Internet (WAP and IP).
Security Concerns
Application Domains
5.
6.
Money Reaps Money V/S Too Many Pieces to the Pie
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Mobile Office.
Financial Critical Communications.
Remote Control or Monitoring.
Comparison Of Various Standards
Evaluation
Criterion
ARDIS
MOBITEX
Cellular Digital
Packet Data
(CDPD)
GPRS
Genealogy
Developed
Developed
Pioneered
General
by
Motorola and IBM.
Currently
owned by
Americal Mobile
Satellite Corporation
by Ericcson and
Swedish Telecom.
Mobitex is an open,
nonproprietary system, but
the specification is
copyrighted and made
available under a royalty-free
license. The technical details
of Mobitex are collectively
referred to as the Mobitex
Interface Specification (MIS)
in
1990 by Baby
Bells (Regional
Telecom
Operators such
as Nynex, U.S.
West,
Ameritech, Bell
South, and Bell
Atlantic among
others)
Aimed at
providing
wireless data
services while
using existing
Advance Mobile
Phone Service
Network(AMPS)
Packet
Radio Service (GPRS)
specifications were
published at the end
of 1997 after work in
ETSI, which had
started in 1994.
Relatively new
technology
Key for evolving
GSM Networks to 3G
Data
as well as
infrastructural
overlay.
Comparison Of Various Standards
Evaluation Criterion –
Services Offered
ARDIS(1G)
MOBITEX(2G)
CDPD(1G)
GPRS(2.5G)
National Roaming
Yes – RF/ NCP selects
appropriate Base station
to comm. Using signal
strength
Yes – Automatic Frame
Sync.
Yes, But Limited to areas
covered by Providers.
Yes, but it can be easily
extended and network
adjusted according to
clientele locations.
Data Transmission Rate
4.8 Kbps (MDC 4800) and
in certain cities upto 19.2
Kbps
But extensible by Service
Providers.
Initially 1.2 Kbps
Now upto 8 Kbps
Optimization of Radio
channels by trunking
method
Interoperability with
other Networks
Protocol Conversion at
Message switch.
Additionally, Network
Monitoring is done at MS
At regional Switch Levels
to Internet(over TCP/IP),
Office LANs etc.
Gross
Eg: Service G(PRS)
S(upport) Node in
corporate areas
Transmission Rate
is 19.2 Kbps
Actual betn 9-13 Kbps.
The transmitted blocks
have 378 bits (or 63
symbols) of coded data
using a Reed-Solomon
code to which 42 control
bits are added making a
total of 420 bits
transmitted every 21.875
ms (producing a bit rate
of 19.2 Kbps).
Up to 115 Kbps
True Interoperability
using TCP/IP,
Connectionless Network
Protocol (CLNP).
Interoperable with other
Networks.(TCP/IP, CLNP,
X.25)
Proper Network planning
can increase revenues.
So easily extensible
Comparison Of Various Standards
Evaluation Criterion –
Services Offered
ARDIS
MOBITEX
CDPD
GPRS
Personal Messaging
from PSTN phone
Real time, Bidirectional mail
service from a DTMF
equipped phone.
NA
NA
NA
Linking with
Customers Computer
ASYNC, BISYNC,
SNA, X.25
X.25, HDLC
Existing AMPS
Network
Existing GSM
Network
Peer To Peer
Communication
within Base Station
Yes
Yes,
In fact Base
stations can operate
autonomously in case
of loss of connection
with backbone
True Peer – to Peer
within Base Station
No.
NA
Multiple Destination
No
Yes
NA
Yes, Point to
multipoint
transmission by LLC
Back-haul
No
No
Yes
No, but limited to
authentication.
Comparison Of Various Standards
Evaluation Criterion –
ARDIS
MOBITEX
CDPD
GPRS
Transmission Rates
Backbone MDC 4800 –
4.8 Kbps
Initially 1.2 Kbps
Now upto 8 Kbps
19.2 Kbps
19.2 Kbps
RD-LAP – 19.2 Kbps (Eff.
8 Kbps)
Optimization of Radio
channels by trunking
method
Operating Band
800 Mhz
US Uplink – 896-901 MHz
Downlink – 935-940 MHz
Rest of the world – 410450 MHz
800 MHz
NA
Error Detection
Mechanisms
Yes - ACK
Yes - ARQ and FEC
Block Interleaving and
Hamming(12,8) codes for
error correction
Yes – ARQ and FEC for
interference and fading of
cellular channels.
Yes
Full Duplex
Yes
Semi Duplex
Yes
Yes
Channel Spacing = 25
KHz
Duplex Channel Spacing
= 45 KHz
Channel Spacing
= 12.5 KHz
Channel Spacing = 30
KHz
Security
Evaluation Criterion –
ARDIS
MOBITEX
CDPD
GPRS
Security
SSL
Mobile Access
Numbers(MAN)
No mutual
authentication
Local key
storage Because CDPD
devices lack a tamperresistant module like an
SIM card to store the
NEI, the possibility always
exists that a hacker could
retrieve the unique
identifiers from the device
itself.
SIM
Lack of mutual
authentication
(device to
network and
network to
device) and the
local storage of
the serial
number and
MAN pairs
cards and the
associated algorithms.
User identity
confidentiality is ensured

by means of the TLLI.
Comparison Of Various Standards
Evaluation Criterion –
ARDIS
MOBITEX
CDPD
GPRS
Medium Access
FDMA with Gaussian
FSK
Slotted ALOHA with
FMSK
DSMA (Similar to
CSMA/CD) with
GMSK
Slotted ALOHA
Base Station
Coverage
40 W (15-20 Km)
NA
NA
Extensible
Mobile Terminal
4W
Power Control for
both low power as
well as high power
mobiles.
NA
NA
Packet Size
256 bytes (MDC
4800)
512 bytes (Radio Link
Data Access Protocol)
512
User data size is
small
NA
Bytes
3 Packet types(Text,
Data, Status)
Comparison Of Various Standards
Evaluation
Criterion
Coverage
ARDIS
MOBITEX
CDPD
GPRS
90 % Urban
Business
population, about
40,000 customers.
More than 400
Metropolitan
Areas in US,
Puerto Rico, And
Virgin Islands
In
195
Extensible, New
Technology.

US 93% urban
business
population.
1200 Base
station, 7700
cities, 11000 miles
of Interstate.
 20 Across 20
countries and 5
continents
Globally
accepted hence
true de-facto
standard.
Markets(118
MSA, 36 RSA)
36 International
Markets
Available to 53%
US population
Comparison Of Various Standards
Evaluation
External
Criterion
Users
ARDIS
MOBITEX
CDPD
GPRS
IBM
RAM
Electronic
NA
Support
Engineers.
Emergency Use (LA
Earthquake 1994)
Financial Reporting
and MOBIPAC
Failed
Startups like
MOBIPAC of French
Telecom due to insuff
customer base.
mail,
parcel delivery
recording, inventory
control, credit card
checking, security,
weather information
services, and road
traffic information.
The long-term
prognosis for CDPD is
unclear. AT&T
remains the largest
CDPD carrier in the
United States and
their PocketNet
service has attracted
a considerable user
base.
Comparison Of Various Standards
Evaluation Criterion
ARDIS
MOBITEX
CDPD
GPRS
Limitations
Indoor
Lack
Initial
Not end-to-end
security
Added cost
Trust issues
Reuse puts
high constraints on
freq. reuse.
To ensure
dependablity,
message is
trasmitted to multiple
base stations
ARDIS is slowly
being phased out.
of mutual
authentication
(device to network
and network to
device) and the local
storage of the serial
number and MAN
pairs
Huge initial
investment due to
setup of own
network unlike CDPD
Cost savings
by using AMPS is
working against
CDPD as carriers are
trying to go complete
digital.
Defragmentation by
the business
proponents of CDPD
has caused
deemphasis of CDPD.
Why GPRS
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Compatibility with the Internet Because the Internet is a
packet-based network utilizing the IP, GPRS provides an easy
connection with Internet-based data. This makes GPRS ideally
suited for wireless data and applications.
Always-on connection Packet switching does not require that a
physical link (such as a circuit) be opened for data transfer. This
enables GPRS users to receive information only when they need to,
but more importantly, it does not require that a circuit-switched
connection be established for every individual call.
Efficient networks Packet switching enables data packets to be
redirected over the optimal network path and bypass potential
network bottlenecks. Furthermore, packet switching means that the
radio spectrum is only used during the transmit or receive mode.
This enables multiple users to share the same spectrum in a given
area. In circuit switching, a dedicated circuit must be opened for
each call, preventing multiple users from using the same frequency
in a cell site.
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From Handbook of Wireless Networks
Upgrade to GPRS Over 3G
•Because these networks did not require additional radio
spectrum, the cost of building GPRS-capable wireless networks
was relatively minor. This contrasted sharply with the emerging
third-generation (3G) networks, which required new spectrum
and a large infrastructure upgrade. Above figureprovides a sense
of the infrastructure requirements for deploying a GPRS
network.
•As another example, in December 2001, AT&T Wireless stated
that the network upgrade cost for GPRS was $300 to $400
million, whereas the 3G upgrade cost was at least $1 billion.
•From Wireless Security
GPRS – Good for the Customer
and Good for the operator.
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In Europe, many GSM operators started promoting GPRS
to build awareness around the capabilities of these faster
networks. Furthermore, because the network upgrade
costs were relatively low, the operators could charge
relatively modest tariffs for GPRS and still generate a
positive return on the investment. In order to utilize
GPRS, subscribers only needed to purchase a new GPRSenabled handset. Monthly fees were usually based on
the amount of data sent to an individual’s phone.
GPRS subscribers could then utilize significantly higher
data throughput for accessing the Internet, and for
receiving and sending e-mail. In most cases,
subscription fees are based on the amount of data
received.
Other Advantages
1. Network Protocols
2. Subnetwork Dependant
Convergence Layer.
• Multiplexing to
single logical Layer.
• Ciphering
• Segmentation
• Compression
3. Logical Layer – LAPD
Point to Multi point
transmission
4. RLC/MAC – Contention
resolution, QoS, Framing
and error control.
Questions ?