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Cellular Networks:Architectural and Functional Overview,
Evolving Trends, and Clean Slate DesignParadigms
Jatinder Pal SinghDeutsche Telekom Labs,
Stanford University,
Oct., 2007
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Agenda
Basics & Technology Evolution Architecture and Functionality (GSM, 3G and
beyond) Cellular future goals (2010 and beyond)
Emerging trendsAlternative wireless access technologiesConvergence
Comparison with Internet and sample scenario
studies Economics of operation From a clean slate
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Basics: Structure
CellsDifferent
Frequencies or
Codes
Base Station
Fixed transceiver
Mobile Station
Distributed transceivers
Downlink
Uplink
Handoff
Multiple Access
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Basics: Multiple Access Methods
Time
Frequency
Codes
TDMA: Time
Division Multiple
Access
FDMA: Frequency
Division MultipleAccess
CMDA: Code
Division Multiple
Access
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Some More Basics
Uplink & Downlink separated inTime: Time Division Duplex (TDD), or
Frequency: Frequency Division Duplex (FDD)
Information (voice, data) is digitized and bitstreams modulated onto carrier
Modulation, data redundancy (coding),transmission power, data retransmissions (ARQ)
adapted to varying wireless channel quality Spatial attenuation of signal
Frequency or codes can be reused (frequency reuse)
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Cellular Technology Evolution
0G: Mobile radio telephones (PTT, MTS) 1G: Analog
2G/3G and beyond - digital:
GSM Family cdmaOne/CDMA2000 Family
GSM
GPRS
EDGE
HSCSD
WCDMA (UMTS)
HSPA
cdmaOne/IS-95
CDMA2000 EV-DO
2G
3G
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Agenda
Basics & Technology Evolution Architecture and Functionality (GSM, 3G
and beyond) Cellular future goals (2010 and beyond)
Emerging trendsAlternative wireless access technologiesConvergence
Comparison with Internet and sample scenario
studies Economics of operation From a clean slate
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Global System for Mobilecommunications (GSM)
900/1800 MHz band (US: 850/1900 MHz) For 900 MHz band
Uplink: 890-915
Downlink: 935-960
25 MHz bandwidth - 124 carrier frequencychannels, spaced 200KHz apart
Time Division Multiplexing for 8 full rate speech
channels per frequency channel. Circuit Switched Data with data rate of 9.6 kbps
Handset transmission power limited to 2 W in
GSM850/900 and 1 W in GSM1800/1900.
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Architecture
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The Base Station Subsystem (BSS)
Base Transceiver Station BTS - transceivers servedifferent frequencies.
Frequency hopping by handsets and transceivers
Sectorization using directional antennas
Base Station Controller (BSC) controls several(tens to hundreds) of BTSsallocation 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
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Network Switching Subsystem (NSS)
GSM circuit-switched core network managescommunication between mobile phones & PSTN
Mobile Switching Center (MSC) : provides circuitswitched calling, mobility management, GSMservices for usersGateway MSCinterfaces with PSTN, determines
which visited MSC the subscriber being called iscurrently located at
Visited MSC - MSC where a customer is currentlylocated. 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.
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GPRS core network
Mobility management, sessionmanagement, and transport for IP services
GPRS Tunneling Protocol, GTP (over UDP)
allows end users mobility with continuedInternet connectivity
GPRS support nodes (GSN)
GGSN - Gateway GPRS Support NodeSGSN - Serving GPRS Support Node
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GSM Support for Data Services:GPRS
User gets pair of uplink and downlinkfrequencies.
Multiple users share the same frequency channelwith time domain multiplexing.
Packets have constant length corresponding to aGSM time slot.
Downlink uses FCFS packet scheduling Uplink
Slotted ALOHA for reservation inquiries duringcontention phase
data transferred using dynamic TDMA with FCFSscheduling.
Upto 64 kbps (more for EDGE) downlink per user.
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UMTS and 3G technologies(WCDMA & HSPA)
Universal Mobile Telecommunications System (UMTS) - WCDMA asthe underlying interface
Supports up to 14 Mbps rates with HSDPA (typical present deployedrates per user 384kbps)
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 onone or several pairs of 1.25 Mhz radio channels).
HSDPA allows networks based on UMTS to have higher data rates(1.8. 3.6, 7.2, 14.4 Mbps via AMC, and HARQ, fast packet scheduling.
UMTS air interface forms Generic Radio Access Network (GeRAN)
which can be connected to various backbone networks like theInternet, ISDN, GSM or UMTS. Using PCMCIA or USB card, or cellular router customers are able to
access 3G broadband services
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Agenda
Basics & Technology Evolution Architecture and Functionality (GSM, 3G and
beyond) Cellular future goals (2010 and beyond)
Emerging trendsAlternative wireless access technologiesConvergence
Comparison with Internet and sample scenario
studies Economics of operation From a clean slate
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In the decade beyond 2010
Next Generation Mobile Networks (NGMN) Ltd. -Consortium with partnership of major mobileoperators
Recommendations without specific technologyprescriptions
Target to establish performance targets,recommendations and deployment scenarios forfuture wide-area mobile broadband networkpacket switched core
The architecture intended to provide a smoothmigration of existing 2G/3G networks towards anIP network that is cost competitive and hasbroadband performance.
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NGMN: Beyond 3G
Video telephony and multimedia conferencing, IM, videostreamingamong 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
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NGMN Envisioned SystemArchitecture
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Agenda
Basics & Technology Evolution Architecture and Functionality (GSM, 3G and
beyond) Cellular future goals (2010 and beyond)
Emerging trendsAlternative wireless access technologiesConvergence
Comparison with Internet and sample scenario
studies Economics of operation From a clean slate
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Alternative fixed wireless and MANstandards
WiMAX, the Worldwide Interoperability forMicrowave Access based on IEEE 802.16standard
Last-mile broadband access, backhaul for cellular
networks, interconnectivity for hotspots OFDMA used by 802.16e. MIMO support amongst
recent developments
Licensed spectrum profiles: 2.3GHz, 2.5GHz and
3.5GHz. US mostly around 2.5 GHz, assignedprimarily to Sprint Nextel, Clearwire.
Claims for delivery of 70 Mbps, and over 50kilometers, not simultaneously true.
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Convergence
Heterogeneous access technologies Multi-mode access devices
Dual mode phones (WiFi, 2.5/3G), UMA
Heterogeneous Services
Cellular Internet access and Internet basedvoice/video access
Challenges
Time variant heterogeneous network characteristics
Heterogeneous applications with different utilities
System design and networking challenges
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Agenda
Basics & Technology Evolution Architecture and Functionality (GSM, 3G and
beyond) Cellular future goals (2010 and beyond)
Emerging trendsAlternative wireless access technologiesConvergence
Comparison with Internet and sample
scenario studies Economics of operation From a clean slate
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Cellular Networks and InternetCellular Networks Internet
VoiceData
Packet
Switched
Controlled Semi-Organic
Good Poor
Incipient
Service
Technology
Evolution
Mobility
Support
Circuit Switched Analog
Circuit Switched DigitalC.S. Voice + P.S. Data
New ServicesOperator initiated
or partneredThird party/
independent (largely)
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Cellular Networks and Internet
Cellular NetworksInternet
Data rates for
supporting
broadband
services
Insufficient as of
presentRelatively high
Cost per MB
of dataHigher
Lower
QoS at edges Good Support
(voice vs. data)Mostly absent
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Internet : Sample scenarioResidential Broadband access
Internet
BRASDSLAM
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?
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Cellular Scenario
Better QoS, schedulingBetter Mobility within the cellular network
Integrated voice/data Authentication
Downside is excessive edge network delays,
costs of network deployment.
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Agenda
Basics & Technology Evolution Architecture and Functionality (GSM, 3G and
beyond) Cellular future goals (2010 and beyond)
Emerging trendsAlternative wireless access technologiesConvergence
Comparison with Internet and sample scenario
studies Economics of operation From a clean slate
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The Economics
3G spectrum licensing and migration cost Telecom equipment vendorseconomics
of operation, meeting bids vs. system
upgrades for technical innovation Stiff competition for fixed and mobile
segments of operators, drive towards
services. Interesting and sometimes conflicting
dynamics for both fixed and mobile
operators.
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Agenda
Basics & Technology Evolution Architecture and Functionality (GSM, 3G and
beyond) Cellular future goals (2010 and beyond)
Emerging trendsAlternative wireless access technologiesConvergence
Comparison with Internet and sample scenario
studies Economics of operation From a clean slate
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From a Clean Slate Greater intelligence at edges of networks, eventually leading to just
network elements of different sizes and capabilities Functional homogeneity in network elements in terms of
storage/caching, processing, networking capability. Such networkelement should likely be multi-homed connected with heterogeneous technologies (including
p2p, delay tolerant),
have intelligence for resource allocation, QoS have interaction capability with other network elements (including user
devices), support mobility, handoffs have ability to recognize needs of existing and new applications (HDTV,
phone, streaming video)
be plug and play Interfacing of applications/services (QoS specs) with underlying
serving networks for fast and easy deployment. Heterogeneity in access technologies amongst user carried devices
honored and accepted by the network elements.
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Options for operators
Sharing the spectrum/infrastructure costs? New service models to forestall cost of
upgrades
Good opportunity for fixed and mobilecarriers to take initiative.
D t h T l k L b t i
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Deutsche Telekom Laboratories:Related Research Efforts
Broadband Access Sharing (Extended HotSpots) Commercial grade routers with virtualization, user traceability, limited
QoS support. Limited trail in Berlin; Pilot for extensive evaluation launched and
technology on company product roadmap for 2008. Distributed Authentication framework for a Global WiFi network
(Mobicom07, extended abstract)
Heterogeneous Network access Optimal Control theoretic approach for rate allocation (WiOpt07) Convex optimization framework for media-aware rate allocation for HD
video sequences (ACM Multimedia07, best student paper award) Markov Decision Process based flow assignment over heterogeneous
networks (IEEE WoWMoM07, top 15 papers)
Peer to Peer Media Streaming Large scale dynamics of a commercial P2P streaming session and real-
world testing of commercial P2P streaming solutions. Gossip based P2P streaming protocol (Journal on Advances in
Multimedia07)
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Publications and other information:
http://www.stanford.edu/~jatinder
Email:
http://www.stanford.edu/~jatindermailto:[email protected]:[email protected]://www.stanford.edu/~jatinder