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Introduction to Cellular Networking and Rethinking Mobile Architectures

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Title: Introduction to Cellular Networking and Rethinking Mobile Architectures


1
Introduction to Cellular Networking and
Rethinking Mobile Architectures
  • Jatinder Pal Singh
  • EE 392I, Lecture-3
  • April 13th, 2010

2
Agenda
  • Basics Technology Evolution
  • Architecture and Functionality (GSM, 3G and
    beyond)
  • Cellular future goals
  • Emerging trends
  • Alternative wireless access technologies
  • Convergence
  • Comparison with Internet and sample scenario
    studies
  • Economics of operation
  • From a clean slate

3
Basics Structure
Multiple Access
Downlink
Handoff
Uplink
Base Station Fixed transceiver
Mobile Station Distributed transceivers
Cells Different Frequencies or Codes
4
Basics Multiple Access Methods
Frequency
CMDA Code Division Multiple Access
TDMA Time Division Multiple Access
FDMA Frequency Division Multiple Access
Codes
Time
5
Some More Basics
  • Uplink Downlink separated in
  • Time Time Division Duplex (TDD), or
  • Frequency Frequency Division Duplex (FDD)
  • Information (voice, data) is digitized and bit
    streams 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)

6
Cellular Technology Evolution
  • 0G Mobile radio telephones (e.g. MTS)
  • 1G Analog
  • 2G/3G/4G .. - digital

GSM/3GPP Family
cdmaOne/CDMA2000 Family
GSM
cdmaOne/IS-95
GPRS
2G
EDGE
UMTS, WCDMA
CDMA2000 EV-DO
3G
HSPA
4G
LTE
7
Agenda
  • Basics Technology Evolution
  • Architecture and Functionality (GSM, 3G and
    beyond)
  • Cellular future goals
  • Emerging trends
  • Alternative wireless access technologies
  • Convergence
  • Comparison with Internet and sample scenario
    studies
  • Economics of operation
  • From a clean slate

8
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.

9
Architecture
10
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

11
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

12
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 users data between users current
    SGSN and GGSN
  • GPRS support nodes (GSN)
  • GGSN - Gateway GPRS Support Node
  • SGSN - Serving GPRS Support Node

13
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.

14
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.

15
Agenda
  • Basics Technology Evolution
  • Architecture and Functionality (GSM, 3G and
    beyond)
  • Cellular future goals
  • Emerging trends
  • Alternative wireless access technologies
  • Convergence
  • Comparison with Internet and sample scenario
    studies
  • Economics of operation
  • From a clean slate

16
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.

17
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 gt 100Mbps downlink
  • Latency core lt 10ms, RAN lt10ms, lt30ms 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

18
NGMN Envisioned System Architecture
19
Agenda
  • Basics Technology Evolution
  • Architecture and Functionality (GSM, 3G and
    beyond)
  • Cellular future goals
  • Emerging trends
  • Alternative wireless access technologies
  • Convergence
  • Comparison with Internet and sample scenario
    studies
  • Economics of operation
  • From a clean slate

20
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.

21
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

22
Agenda
  • Basics Technology Evolution
  • Architecture and Functionality (GSM, 3G and
    beyond)
  • Cellular future goals
  • Emerging trends
  • Alternative wireless access technologies
  • Convergence
  • Comparison with Internet and sample scenario
    studies
  • Economics of operation
  • From a clean slate

23
Cellular Networks and Internet
Internet
Cellular Networks
Incipient Service
Data
Voice
Packet Switched
Technology
Semi-Organic
Controlled
Evolution
Operator initiated or partnered
Third party/ independent (largely)
New Services
Mobility Support
Good
Poor
24
Cellular Networks and Internet
Internet
Cellular Networks
QoS at edges
Good Support (voice vs. data)
Mostly absent
Data rates for supporting broadband services
Insufficient as of present
Relatively high
Lower
Cost per MB of data
Higher
25
Internet Sample scenario Residential
Broadband access
Internet
BRAS
DSLAM
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?

26
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.
27
Agenda
  • Basics Technology Evolution
  • Architecture and Functionality (GSM, 3G and
    beyond)
  • Cellular future goals
  • Emerging trends
  • Alternative wireless access technologies
  • Convergence
  • Comparison with Internet and sample scenario
    studies
  • Economics of operation
  • From a clean slate

28
The Economics
  • 3G spectrum licensing and migration cost
  • Telecom equipment vendors economics 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.

29
Agenda
  • Basics Technology Evolution
  • Architecture and Functionality (GSM, 3G and
    beyond)
  • Cellular future goals
  • Emerging trends
  • Alternative wireless access technologies
  • Convergence
  • Comparison with Internet and sample scenario
    studies
  • Economics of operation
  • From a clean slate

30
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 network element 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.

31
Options for operators
  • Sharing the spectrum/infrastructure costs?
  • New service models to forestall cost of upgrades
  • Good opportunity for fixed and mobile carriers to
    take initiative.
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