Cell Phones
and Standards
1
Cell Phones
Standards
Cell Phone Technologies
1G, 2G and 3G
Determining a standard
Wireless Networking
2
Setting Standards
Three main ways that standards get set in practice:
(I) De-facto standards, i.e., standards set primarily by the market.
These standards are often proprietary.
Examples: Microsoft Office and Windows, Java, TCP/IP
Often fast to develop and can be changed readily
But are usually proprietary and may not be “open”
US and cell phones
(II) Voluntary industry agreements, where standards are often
jointly developed. These standards are typically open standards,
that is, they are not proprietary. Example: bar codes
(III) Standards imposed by National Standards Bodies (NSBs), or
agreed upon by regional or international standards development
organizations (SDOs).
Examples: meter
Slow to develop
Non-proprietary
Europe and cell phones 3
Move to a New Standard
Tipping
100% 100
Winner
80
Market
Share 60
40
20
Loser
0% 0
Time
4
Move to a Single Standard
Tipping
100% 100
Winner
80
Market
Share 60
40
20
Loser
0% 0
Time
Why?
5
Tipping
The economic theory of tipping would suggest that
the early adoption of one standard or the decision to
formally set one standard in the European Union
(EU) could tip the whole world toward that standard.
The adoption of a single standard by a few large
firms will likely tip the entire market toward that
standard.
In market competition between wireless standards,
interconnection may mean that the standard tipping
results may apply only if one standard gets far out in
front of a competing standard early on before the
competing standard has a chance to get
established.
6
Cell Phone Technologies
Cellular system divides a coverage area into small
cells.
This allows extensive frequency reuse.
In a typical analog cell-phone system in the United
States, the cell-phone carrier receives about 800
frequencies to use across a city.
The carrier chops up the city into cells. Each cell is
typically sized at about 10 square miles (26 square
kilometers).
Cells are normally thought of as hexagons on a big
hexagonal grid
7
Note 7 cells in pattern
From Mukesh Raghuraman 2003 8
Hexagon grid - Cell
Cell
base
Station
Call
Handof
f
Coverage
area
“Cell”
9
From Mukesh Raghuraman 2003
Movement Between Cells
-Ability to change frequency/channel as the unit moves
from one cell to another cell.
-Enables the concept of frequency reuse. Because cell
phones and base stations use low-power transmitters,
the same frequencies can be reused in non-adjacent
cells.
-The ability that made the cellular system possible.
10
Cell Phone Standards
From Mukesh Raghuraman 2003 Note wide divergence of standards 11
Not all frequencies/ standards shown
1G - Analog Cell Phone Basics
In US, the analog cell-phone standard called AMPS (Advanced
Mobile Phone System) was approved by the FCC and first used in
Chicago in 1983.
Each cell has a base station that consists of a tower and a small
building containing the radio equipment
A single cell in an analog system uses one-seventh of the available
duplex voice channels. That is, each cell (of the seven on a
hexagonal grid) is using one-seventh of the available channels so it
has a unique set of frequencies and there are no collisions:
A cell-phone carrier typically gets 832 radio frequencies to use in a
city.
Each cell phone uses two frequencies per call -- a duplex channel --
so there are typically 395 voice channels per carrier. (The other 42
frequencies are used for control channels)
Therefore, each cell has about 56 voice channels available (395/7).
In other words, in any cell, 56 people can be talking on their cell
phone at one time. (Note all of the above is for ANALOG systems)
– pretty hopeless for Iowa City!
12
1G Analog Problems
Cell phones
Limited battery life (typically 8 hours)
Limited range – could have more powerful cell
phone mounted in cars
Security
None – easy to listen in
E.g. Squidgy-gate and Camilla-gate (1992)
Very limited number of voice channels
13
Analog and Digital
Analog – each conversation occupies whole
channel. Limits number of open lines in each
cell. Frequency Division Multiple Access
(FDMA)
Digital – conversation compressed using 0,
1s and sent out in shorter time. Can share
each frequency. Time Division Multiple
Access (TDMA)
14
Digital
Analog
(most of 2G)
From The
Economist
Analog – each conversation occupies whole channel.
Limits number of open lines in each cell. Frequency
Division Multiple Access (FDMA)
Digital – uses 0, 1s, compressed and sent out in shorter
time. Can share each frequency. Time Division Multiple
Access (TDMA)
15
FDMA
FDMA separates the
spectrum into distinct voice
channels by splitting it into
uniform chunks of
bandwidth.
FDMA is used mainly for
analog transmission. While
it is certainly capable of
carrying digital information,
FDMA is not considered to
be an efficient method for
digital transmission.
16
From How Stuff Works
TDMA – 2G
Compression of digital
signal allows signal to be
sent out in shorter time.
Usually for TDMA, each
conversation takes up one
third of channel.
Note more frequencies set
aside for 2G
Nearly all US and Europe
2G systems use TDMA
(exceptions include
SprintPCS, CDMA)
Can also include encryption
17
Another Way to Increase Number of
Simultaneous Conversations - CDMA
Code-division Multiple Access (CDMA)
Involves spreading a radio signal out over a range of frequencies.
Each transmission is scrambled using a random “code”
Allows for more simultaneous conversations than other approaches
Handsets stop transmitting when the user isn’t talking – allows more
conversations
FDMA is akin to a party at which everybody talks simultaneously, but
each pair of speakers converses at a different musical pitch, from
booming bass to piping treble. A system in which party-goers took
turns to speak at different pitches would be like TDMA. And
everybody talking at once, only in different languages (so that other
conversations are rendered incomprehensible), would be equivalent
to CDMA. (The Economist, 2003)
18
2G Advantages Over 1G
Cell phones
Increased battery life (significantly more than 8
hours)
Increased range
Security
Possible to encrypt signals
Increased number of voice channels
19
2G Standard - GSM
Global System for Mobile communications (GSM).
Mandated for use in Europe
In US, companies were allowed to develop and use
their own choice of standard for 2G
Result
Europe – single 2G standard GSM
US – multiple standards. Some companies use GSM but
on a different frequency from Europe. Standards uses
include TDMA, GSM and CDMA
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Move to Increase Bandwidth
Increase bandwidth allows for larger amount of data
to be received – web browsing, pictures, video,
music at increased quality.
How to do this
2.5G approaches – build on 2G systems
3G systems – new systems with increased bandwidth over
2.5G systems
Bandwidth
2G data rates 9.6 Kbps – 14.4 Kbps.
2.5G data rates 64 – 144 Kbps.
3G data rates144 Kbps. to 2 Mbps. Live high quality video
requires 2Mbps.
21
2.5G
Uses General Packet Radio Services (GPRS)
GSM and TDMA enhanced to packet based
networks – IP based (the available radio resource
can be concurrently shared between several users)
GPRS is primarily a simple software upgrade on
GSM and TDMA
Relatively easy for the service providers to update
their networks
Can simultaneously make telephone calls and
transmit data.
Expect to see this generally in place over the next
few years [e.g. AT&T moving to GSM with GPRS]
22
3G
High data rates:
144 kbits/sec or higher in high mobility (vehicular)
traffic
384 Kbits/sec for pedestrian traffic
2 Mbits/sec or higher for indoor traffic
Different Standards
WCDMA – Europe and Japan
CDMA2000 from Qualcomm used in USA, Korea
TD-S CDMA China
23
Vodafone advertisement
24
Setting Standards
Europeans set standard for 2G – GSM while
US companies were free to develop their own
standard
Did the imposition of a standard for 2G help the
Europeans?
25
2G – Europe and Setting a
Single Standard
Features work across companies – e.g. text messaging
Larger economies of scale in the production of both
terminals/handsets and network infrastructure equipment reduce
costs and increase availability.
Increase market share for European companies?
Variety of terminal equipment (handsets) tends to be greater.
Larger number of purchasers of service since single standard. By
the end of 1993 there were already more than 1 million GSM
users in Europe. By contrast, in the U.S., the FCC did not even
complete its first auction allocating PCS spectrum until March of
1995. (Could also be partly due to high costs of traditional
European phone companies).
Wider coverage area (perhaps)
26
Text Messaging
Large difference
between Europe and
US
Ireland around 70 per
month, USA 7 per
month
Messaging accounts for
20% of revenue for EU
cell phone companies.
Why?
27
Market Impact of European Cell
Phone Handset Manufacturers
28
From: The Economist 10/12/2000
29
SprintPCS National Coverage
30
Dark Green = Digital Coverage Light Green = Analogue Coverage
SprintPCS – New Mexico
Coverage
31
Benefits From Multiple
(Competing) Standards
Types of services tend to differ across technologies.
For example, CDMA networks have offered more
and better data services than were available on
GSM networks.
More technological competition (“highly centralized
approach foregoes the benefits of competition in
research and development…”)
Greater price competition (at least early on) among
competing incompatible standards (perhaps)
Wider coverage area (perhaps)
32
Setting 3G Standards
Two main standards have been proposed
Wideband CDMA (WCDMA) for Europe and
CDMA2000 for US and other countries
CDMA2000 is a natural migration from
CDMA-One (the 2G CDMA standard),
while WCDMA is essentially incompatible
with any existing technology.
33
Will a Single 3G European
Standard Help the Europeans
Not clear
3G does not show real signs of take off. Who will
use it?
Will consumers be happy with 2G and 2.5G?
Will WCDMA work as promised?
Will CDMA2000 build a huge lead worldwide?
Will 802.11g, 802.11a, or 802.16 (WiMax) take
over?
34
WiMAX
WiMAX, an acronym that stands for Worldwide
Interoperability for Microwave Access, is a
certification mark for products that pass conformity
and interoperability tests for the IEEE 802.16
standards. Shared data rates up to 70 Mbit/s
http://en.wikipedia.org/wiki/Wimax
Aim for line of sight of 30 miles (15 miles non-line of
sight). Can cover a metropolitan district.http://en.wikipedia.org/wiki/Wimax
First products expected in 2005. See, for example,
http://www.egovmonitor.com/node/691/
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Wireless Internet Access
3G data rates:
144 kbits/sec or higher in high mobility
(vehicular) traffic
384 Kbits/sec for pedestrian traffic
2 Mbits/sec or higher for indoor traffic
802.11g data rate of 20Mbit/sec, 802.11a
data rate of about 24Mbit/sec
Usually limited by other parts of the
network
Limited range: 300 feet, more with
antenna. Office environment, Iowa City?
Voice over IP (VoIP) handsets possible
36