Transcript Code Division Multiple Access

Cellular Networks and
Mobile Architectures
Mobile Telecommunications
Mobile Switching
Office
Air Interface
Public Switched
Telephone Network
PSTN
Cell Tower
Pre-Cellular Technology
 One Transmitter
 High Power
 Limited Channels
Source: International Engineering Consortium
Cellular Architecture
 Many Transmitters
 Low Power
 Frequency Reuse
Source: International Engineering Consortium
Cellular Architecture
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Each tower serves one cell
Each cell uses different
frequencies
As phone moves from one cell to
another, towers “handoff” calls
Seven Way Frequency Re-use
Cellular networks are designed
so adjacent cells use different
frequencies
Source: International Engineering Consortium
Cellular vs PCS
 All mobile telephony providers use “cellular” architecture
 Primarily two different types of FCC licenses are used to
provide mobile telephony: Cellular and PCS (Personal
Communications System)
Cellular
PCS
Spectrum
850 MHz
1.9 GHz
Bandwith
2x25 MHz licenses
3x30 MHz licenses
3x10 MHz licenses
Introduced
1980s
1990s
Format
Originally analog
Originally digital
Mobile Telephony Generations
 First Generation – Analog
• AMPS (Advanced Mobile Phone System)
• First cellular standard, used by all cellular licensees
• Represented pioneer analog cellular systems that permitted twoway voice communications, circuit-switched data transmission
Mobile Telephony Generations
 Second Generation - Digital
• TDMA (Time Division Multiple Access) - AT&T
• CDMA (Code Division Multiple Access) - Sprint, Verizon
• GSM (Global System for Mobile Communications)
• Voicestream, Most European Operators
• iDEN (Integrated Digital Enhanced Network) - Nextel
• Uses SMR licenses rather than cellular or PCS
• 2G networks are the first digital mobile telephone networks and
offer voice services such as voice mail and caller ID as well as
Short Messaging Service (SMS)
• Data speeds of 9.6 to 19.2 kbps
Mobile Telephony Generations
 Third Generation – Digital
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WCDMA: Wideband Code Division Multiple Access
CDMA2000 : Code Division Multiple Access
UMTS : Universal Mobile Telecommunications System
EDGE : Enhanced Data for Global Evolution
DECT: Digital Enhanced Cordless Telecommunications
Called UMTS in Europe
Currently in development
3G technology promises Internet access with speeds up to 2 Mbps
Combines high-speed mobile access with Internet Protocol (IP) based services.
Planned 3G services include video and audio streaming and location-based
services
• This doesn't just mean fast mobile connection to the World Wide Web - by
liberating us from slow connections, cumbersome equipment and immovable
access points, 3G will enable new ways to communicate, access information,
conduct business and learn.
1G: First Generation Mobile Telephony
 AMPS : Advanced Mobile Phone System
• Original Standard for analog mobile telephony systems
• Still used in some areas of North America, Latin America, Eastern
Europe, Australia, and parts of Russia and Asia.
• Competes with GSM and CDMA
• To optimize the use of transmission frequencies, AMPS divides
geographic areas into cells
• Each connection uses its own dedicated frequency - of which there
are about 1,000 per cell.
• Two cells can use the same frequency for different connections so
long as the cells are not adjacent to each other.
• The digital IS-136 TDMA standard (often known as D-AMPS) offers
the evolutionary path from analog AMPS.
2G: Second Generation Mobile Telephony
 CDMA : Code Division Multiple Access
• IS-95 based digital technology for delivering mobile telephone
services.
• CDMA systems have been in commercial operation since 1995
• These systems now support over 95 million subscribers worldwide.
• CDMA networks operate in the 800 and 1900 MHz frequency
bands with primary markets in the Americas and Asia.
• Provides for voice and data services up to speeds of 64 kbits/sec, as
well as integrated voice mail and SMS services.
• Marketed using the name cdmaOne.
• The next evolutionary step for 3G services is CDMA2000, or IS2000.
2G: Second Generation Mobile Telephony
 TDMA : Time Division Multiple Access
• Also known as D-AMPS
• Technology for digital transmission of radio signals between a
mobile telephone and a radio base station.
• In TDMA, the frequency band is split into a number of channels.
• Each channel is split into three time units, so that three calls can
share a single frequency channel without interfering with one
another.
• Based on the IS-136 standard.
• It is one of the world's most widely deployed digital wireless
systems. PR providers are now switching from CDMA to TDMA
• It provides a natural evolutionary path for analog AMPS networks
• Offers efficient coverage and is well suited to emerging applications,
such as wireless virtual private networks (VPNs)
• Ideal platform for PCS (Personal Communication Services).
2G: Second Generation Mobile Telephony
 GSM : Global System for Mobile Communications
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First introduced in 1991
One of the leading digital cellular systems.
Eight simultaneous calls can occupy the same radio frequency.
GSM simplifies data transmission to allow laptop and palmtop
computers to be connected to GSM phones.
It provides integrated voice mail, high-speed data, fax, paging and
short message services capabilities, as well as secure
communications.
It offers the best voice quality of any current digital wireless
standard.
Originally a European standard for digital mobile telephony, GSM
has become the world's most widely used mobile system in
use in over 100 countries.
GSM networks operate on the 900 MHz and 1800 MHz waveband
in Europe, Asia and Australia, and on the 1900 MHz waveband in
North America and in parts of Latin America and Africa.
2G: Second Generation Mobile Telephony
 GPRS : General Packet Radio Service
• Packet-linked technology
• Enables high-speed wireless Internet and other data
communications.
• GPRS provides more than four times greater speed than
conventional GSM systems.
• Using a packet data service, subscribers are always connected and
always on line so services will be easy and quick to access.
Global System for Mobile
communications (GSM)
 900/1800 MHz band (US: 850/1900 MHz)
 For 900 MHz band
Uplink: 890-915
Downlink: 935-960
 25 MHz bandwidth - 124 carrier frequency
channels, spaced 200KHz apart
 Time Division Multiplexing for 8 full rate
speech channels per frequency channel.
 Handset transmission power limited to 2 W
in GSM850/900 and 1 W in GSM1800/1900.
Architecture
The Base Station Subsystem (BSS)
 Base Transceiver Station BTS - transceivers serve
different frequencies.
 Frequency hopping by handsets and transceivers
 Sectorization using directional antennas
 Base Station Controller (BSC) controls several
(tens to hundreds) of BTSs
 allocation of radio channels
 handovers between BTSs
 concentrator of traffic
 databases with information such as carrier frequencies,
frequency hopping lists, power reduction levels, etc.
for each cell site
Network Switching Subsystem (NSS)
 This GSM core network manages communication amongst
mobile devices & with PSTN
 Mobile Switching Center (MSC) : routing of calls and GSM
services for users, mobility management, handovers,
 Gateway MSC – interfaces with PSTN, determines the visited MSC
at which the subscriber being called is currently located
 Visited MSC - MSC where a customer is currently located. The
Visitor Location Register (VLR) associated with this MSC has
subscriber's data.
 Anchor MSC - MSC from which handover initiated.
 Target MSC - MSC toward which a handover should take place.
 Home Location Register (HLR): database with all mobile
phone subscriber details
GPRS core network
 Mobility management, session
management, and transport for IP services
 GPRS Tunneling Protocol, GTP allows end
users mobility with continued Internet
connectivity by transporting user’s data
between users’ current SGSN and GGSN
 GPRS support nodes (GSN)
GGSN - Gateway GPRS Support Node
SGSN - Serving GPRS Support Node
GSM Support for Data Services:
GPRS
 User gets pair of uplink and downlink
frequencies.
 Multiple users share the same frequency channel
with time domain multiplexing.
 Packets have constant length corresponding to a
GSM time slot.
 Downlink uses FCFS packet scheduling
 Uplink
 Slotted ALOHA for reservation inquiries during
contention phase
 data transferred using dynamic TDMA with FCFS
scheduling.
 Upto 64 kbps (more for EDGE) downlink per user.
IMT-2000
 International Mobile Telecommunications 2000
• Term used by the International Telecommunication Union (ITU),
a United Nations agency, to describe third generation mobile
telephony standards that meet a number of requirements in terms
of transmission speed and other factors.
• Basic standards in IMT-2000 include: \
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IMT-DS (direct spread). WCDMA
IMT-MC (multi-carrier). CDMA2000
IMT-TC (time-code) UTRA TDD & TD-SCDMA
IMT-FT (frequency-time). DECT
IMT-SC (single carrier). TDMA
IMT-2000 Terrestrial Radio Interfaces
Transition to 3G
3G: Third Generation Mobile Telephony
 WCDMA: Wideband Code Division Multiple Access
• Technology for wideband digital radio communications of
Internet, multimedia, video and other capacity-demanding
applications.
• WCDMA is the dominating 3G technology, providing higher
capacity for voice and data and higher data rates.
• Uses a new spectrum with a 5 MHz carrier, providing 50 times
higher data rate than in present GSM networks, and 10 times
higher data rate than in GPRS networks
• Handles up to 2 Mbps for local area access or 384 Kbps for wide
area access. A coming release will include enhancements up to
more than 10 Mbps.
3G: Third Generation Mobile Telephony
 WCDMA: Wideband Code Division Multiple Access
• WCDMA is also known as UMTS
• Has been adopted as a standard by the ITU under the name IMT2000 direct spread.
• The gradual evolution from today's systems is driven by demand
for capacity, which is required by new and faster data based
mobile services.
• WCDMA enables better use of available spectrum and more costefficient network solutions.
• The operator can gradually evolve from GSM to WCDMA,
protecting investments by re-using the GSM core network and
2G/2.5G services.
3G: Third Generation Mobile Telephony
 CDMA 2000: Code Division Multiple Access 2000
• Also known as IS-2000
• 3G technology that can be deployed in several phases.
• The first phase, CDMA2000 1X, supports an average of 144 kbps
packet data in a mobile environment.
• The second release of 1X, called 1xEV-DO can support data rates
up to 2 Mbps on a dedicated data carrier
• The final phase, 1xEV-DV, supports even higher peak rates,
simultaneous voice and high-speed data, as well as improved
Quality of Service mechanisms.
• A key component of CDMA2000 is its ability to support the full
demands of advanced 3G services such as multimedia and other
IP-based services.
3G: Third Generation Mobile Telephony
 EDGE : Enhanced Data for Global Evolution
• A technology that gives GSM the capacity to handle services for
the third generation of mobile telephony.
• EDGE provides three times the data capacity of GPRS.
• Using EDGE, operators can handle three times more subscribers
than GPRS; triple their data rate per subscriber, or add extra
capacity to their voice communications.
• EDGE uses the same TDMA (Time Division Multiple Access)
frame structure, logic channel and 200kHz carrier bandwidth as
today's GSM networks, which allows existing cell plans to remain
intact.
3G: Third Generation Mobile Telephony
 DECT : Digital Enhanced Cordless Telecommunications
• A common standard for cordless personal telephony
• Originally established by ETSI, a European standardization body.
• DECT is a system for cordless business communications.
3G: Applications, Services and
Market
Difference between regular TDMA
and W-CDMA
Difference between regular CDMA
and W-CDMA
UMTS and 3G technologies
(WCDMA & HSPA)
 Universal Mobile Telecommunications System
(UMTS) – commonly uses WCDMA as the
underlying interface
 Theoretically supports up to 14 Mbps rates with
HSDPA
 WCDMA Frequency bands
 1885-2025 Mhz (uplink), 2110-2200 Mhz (downlink)
 US: 1710-1755 MHz and 2110-2155 MHz
 W-CDMA has 5 Mhz wide radio channels
(CDMA2000 transmits on one or several pairs of
1.25 Mhz radio channels).
 HSDPA allows networks based on UMTS to have
higher data rates on downlink(1.8. 3.6, 7.2, 14.0
Mbps via AMC, and HARQ, fast packet scheduling.
Next Generation Mobile Networks
 Next Generation Mobile Networks (NGMN) Ltd. Consortium with partnership of major mobile
operators
 Recommendations without specific technology
prescriptions
 Target to establish performance targets,
recommendations and deployment scenarios for
future wide-area mobile broadband network
packet switched core
 The architecture intended to provide a smooth
migration of existing 2G/3G networks towards an
IP network that is cost competitive and has
broadband performance.
NGMN: Beyond 3G
 Video telephony and multimedia conferencing, IM, video
streaming – among high drivers for NGMN
 Essential System recommendations
 Seamless mobility across all bearers with service continuity
through a min of 120 km/h
 Peak uplink data rates 30-50 Mbps
 Peak > 100Mbps downlink
 Latency core < 10ms, RAN <10ms, <30ms e2e
 QoS based global roaming
 Broadcast, multicast, and unicast services to subscribers of all
environments
 Real time, conversational and streaming in PS across all required
bearers
 Cost per MB : as close to DSL as possible
NGMN Envisioned System
Architecture
Alternative fixed wireless and MAN
standards
 WiMAX, the Worldwide Interoperability for
Microwave Access based on IEEE 802.16
standard
 Last-mile broadband access, backhaul for
cellular networks, Internet Services
 802.16d Fixed WiMAX, 802.16e - Mobile
WiMAX.
 Licensed spectrum profiles: 2.3GHz,
2.5GHz and 3.5GHz. US mostly around 2.5
GHz, assigned primarily to Sprint Nextel,
Clearwire.
Convergence
 Heterogeneous access technologies
 Multi-mode access devices
 Dual mode phones (WiFi, 2.5/3G), UMA
 Heterogeneous Services
 Cellular Internet access and Internet based
voice/video access
 Challenges
 Time variant heterogeneous network characteristics
 Heterogeneous applications with different utilities
 System design and networking challenges
Cellular Networks and Internet
Cellular Networks
Incipient
Service
Voice
Circuit Switched Analog
Technology
Circuit Switched Digital
Internet
Data
Packet
Switched
C.S. Voice + P.S. Data
Evolution
New Services
Mobility
Support
Controlled
Operator initiated
or partnered
Good
Semi-Organic
Third party/
independent (largely)
Poor
Cellular Networks and Internet
Cellular Networks
QoS at edges
Data rates for
supporting
broadband
services
Cost per MB
of data
Good Support
(voice vs. data)
Insufficient as of
present
Higher
Internet
Mostly absent
Relatively high
Lower
Internet : Sample scenario –
Residential Broadband access
Internet
DSLAM
BRAS
Home WiFi Router
QoS: Wireless hop (802.11e?), PPPoE, IP QoS (Diffserv)
and translation mechanisms
Mobility Options: MIP - high-barrier, delay performance,
incremental patch rather than clean solution?
Cellular Scenario
Better QoS, scheduling
Better Mobility within the cellular network
Integrated voice/data Authentication
Downside is excessive edge network delays,
costs of network deployment.
END.