history & context

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© Jasleen Kaur, 2015 1

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COMP 635: WIRELESS NETWORKS

HISTORY & CONTEXT

Jasleen Kaur

Fall 2015

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SOME HISTORY Light, Electromagnetic Waves, TV, WLANs, …

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Using Light for Communication q  Ancient Times:

Ø  Smoke signals (150 BC, Greece) Ø  Light towers (206 BC, China)

q  Not-so-ancient: Ø  Heliographs, semaphores, navy

q  1794, Claude Chappe Ø  Optical telegraph

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Electromagnetic Waves q  Discovery of electromagnetic waves:

Ø  Faraday (1831): demonstrated electromagnetic induction Ø  Maxwell (1860s-70s): theory of electromagnetic waves Ø  Hertz (1886): demonstrated the wave character of

electrical transmission q  Marconi (1896):

Ø  First demonstration of wireless telegraphy Ø  Long-wave transmission, high transmission power

needed (> 200 kW) q  1907: Commercial transatlantic connections

Ø  Huge base stations (Thirty 100m high antennas) q  1915: Wireless voice transmission (NY-SFO)

Ø  Still needed huge antennas, high transmission power

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Small Antennas, Small Power

q  1920: Discovery of short waves (Marconi, again) Ø  Get reflected at the ionosphere Ø  Enabled sending short radio waves around the world,

bouncing at the ionosphere §  Technique still used today for amateur radio

q  1906: Invention of vacuum tube (DeForest, Leiben) Ø  Helped reduce the size of senders and receivers Ø  Still used for amplifying sender output in radio stations

q  1920s: Mobile Transmitters Ø  First phone in a train (wires parallel to track as antennas) Ø  1927: First commercial car radio

§  1922: 18-yr Frost (Chicago) integrated radio into a Ford

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Rise of Broadcasting: TV & Radio

q  1928: Many TV broadcast trials Ø  Baird: TV transmission across Atlantic, Color TV Ø  WGY (Schnectady, NY): regular TV broadcasts, TV news

q  1932: CBS started first tele-teaching

q  1933: Frequency modulation (E.H. Armstrong) Ø  Much better quality than amplitude modulation Ø  Both FM and AM still used for today’s radio broadcasting

§  FM results in better quality

q  1930s: Ø  Many radio stations broadcasting all over the world

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Analog Mobile Phone Systems q  1960s: Bell Labs, US completed initial cellular system design q  1960s-70s: Several European mobile phone projects

Ø  German: A-Netz (1958), B-Netz (1972) §  Carrier freq of 160 MHz, no handover §  connection setup:

–  only from mobile station (A-Netz), fixed network too (B-Netz) §  1971: 80% coverage; 11,000 customers

Ø  Scandinavian countries: NMT (1979) – carrier freq 450 MHz

q  1982: Start of GSM specification Ø  Several incompatible analog mobile phone standards

q  1983: US AMPS system started Ø  Advanced Mobile Phone System – 850 MHz Ø  Included handoffs

q  1984: CT1 (cordless home phone standard) Ø  1987: CT2 – carrier freq 864 MHz, channel rate 32 Kbps

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Digital Wireless Systems q  1991: DECT (Digital European Cordless Telephone)

Ø  1880-1900 MHz; 100 – 500 m range; 120 duplex channels Ø  1.2 Mbps data transmission; encryption, authentication Ø  Up to several 10000 users/km2 ; used in 110+ countries Ø  Renamed: Digital Enhanced Cordless Telecommunications

q  1992: Start of GSM (standardized) Ø  900 MHz, 124 duplex channels Ø  Full international roaming, automatic location services,

authentication, encryption, interoperation with ISDN, relatively high quality audio

Ø  Includes SMS, fax, data services (9.6 Kbps) Ø  Offers compatibility despite provider accounting diversity

§  Currently 400 providers, 190 countries, 70% of world market Ø  Renamed: Global System for Mobile Communication

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Mobile Communication w/ Satellites

q  1998: Iridium system Ø  66 satellites in low earth orbit; uses the 1.6 GHz band Ø  First small and truly portable mobile satellite phones

§  Including data service

q  1998: UMTS (European) Ø  Universal Mobile Telecommunications System Ø  Combines GSM with bandwidth-efficient CDMA solutions

q  IMT-2000: International Mobile Telecommunications Ø  ITU worldwide framework for future mobile communication Ø  Service framework, network architecture, radio interface

requirements, spectrum considerations, … Ø  Includes strategies for developing countries

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WLAN: Wireless Local Area Networks q  1996: HIPERLAN (European)

Ø  High-performance Radio LAN family of standards Ø  Type 1 (5.2 GHz, 23.5 Mbps) – Type 4 (17 GHz, 155 Mbps)

q  1997: IEEE 802.11 standard Ø  Uses the License-free Industrial, Science, Medical band

§  2.4 GHz and infra-red Ø  Initially offering 2 Mbps

q  802.11 emerged as winner for LANs Ø  Standards vs. market forces Ø  In contrast to GSM vs. US technologies

q  1999: more powerful WLAN standards Ø  IEEE 802.11b: 2.4 GHz, 11 Mbps Ø  Bluetooth: 2.4 GHz, < 1 Mbps, short-range, piconets

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Third Generation (3G)

q  2000: GSM higher data rates (up to 57.6 Kbps)

q  Late 90s: UMTS spectrum auctions Ø  Hype: portraying 3G as high-performance mobile Internet

§  UMTS announced as capable of handling interactive video streaming for all users at 2 Mbps

Ø  Thus, auctions for licensing 3G spectrum started Ø  More than 100 Billion pounds paid in Europe alone

§  Companies that had never run a network before paid billions §  Most companies now bankrupt

q  2001: Start of 3G systems Ø  FOMA (Japan), UMTS (Europe) cdma2000 (Korea)

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2000s q  Early 2000s: New WLAN developments

Ø  IEEE 802.11a: 5 GHz, up to 54 Mbps Ø  IEEE 802.11g: 2.4 GHz, up to 54 Mbps Ø  New Bluetooth applications:

§  Headsets, remote controls, wireless keyboards, hot syncing

q  Deployment of 3G infrastructure (licensing pre-condition)

q  Digital terrestrial TV: high quality, mobile, small antenna

q  Next generation mobile and wireless systems: Ø  Likely to be widely Internet based (IP protocols/apps) Ø  Users will have choice of many different networks

q  2009: Netbooks, iphones, VoIPoWLAN, … q  Latest: 802.11ac, 802.11ad, GigaIR, WUSB-UWB, …

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CURRENT STATE OF AFFAIRS Market & Spectrum

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Explosion of User Base

~ 7 billion current mobile phone service subscriptions è more than 96% of world population !

-‐

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015*

Mobile cellular telephone subscripCons

Fixed-‐telephone subscripCons

AcCve Mobile-‐broadband subscripCons

Fixed broadband subscripCons

Internet Users

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Cellular Subscribers Per Region

9%

11%

43%

11%

13%

5% 8%

Regions – September 2008

Africa

Americas

Asia Pacific

Europe: Eastern

Europe: Western

Middle East

USA/Canada

10% 6%

53%

5%

11%

15%

Regions -‐ 2015

Africa

Arab States

Asia & Pacific

CIS

Europe

The Americas

www.gsmworld.com

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Cellular Subscribers Per Technology

0 10 20 30 40 50 60 70 80 90

www.gsmworld.com September 2008

Percen

t

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Spectrum Allocation

q  Limited frequency spectrum Ø  Must be shared among various applications Ø  Typically government regulated

q  US spectrum allocation chart: http://www.ntia.doc.gov/osmhome/allochrt.html

q  More in next lecture-set …

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EXAMPLES OF WIRELESS COMMUNICATION SYSTEMS Paging, Cordless, Cellular

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Some Terminology

q  Portable (hand-held, walk speed) vs mobile (vehicle speed)

q  Base stations: mobiles communicate to fixed base stations Ø  Connected to power source, and a backbone network

q  Classification: Ø  Simplex systems: e.g., paging systems

§  Messages are received, but not acknowledged. Ø  Half-duplex systems: e.g., walkie-talkies

§  Allow two-way communication, but use same radio channel for both transmission and reception.

§  “push-to-talk”, “release-to-listen” Ø  Full-duplex systems: e.g., US AMPS standard

§  Allow simultaneous radio transmission and reception §  Provide two separate channels (frequency division duplex), or

adjacent time slot on a single channel (time division duplex)

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Paging Systems

q  Architecture: Ø  Transmit the page throughout the service area using

base stations, which simultaneously broadcast the page on a radio carrier

Ø  Reliability achieved using large transmission power (~kw) and low data rates (~Kbps)

q  Service: Ø  Send brief

messages to a subscriber

Ø  Simplex, reliable communication

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Cordless Telephony

q  Full duplex in-home communication system Ø  Radio connects portable handset to dedicated base

station, which is connected to a dedicated phone line • 

q  2nd-generation systems cover up to 100s of meters Ø  But no coverage outside range

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Cellular Systems q  Provides wireless connection to the PSTN for any user

location within the system range q  Accommodate large number of users (using cells) over a

large geographic area (using handoffs), within a limited frequency spectrum

q  Base station Ø  Several antennas Ø  Full duplex Ø  Connects to MSC

q  MSC: Ø  Handles channel

allocation in base stations

Ø  Involved in call initiation, termination, and handoff

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ARCHITECTURAL CONTEXT Layered Reference Model

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Internet Structure q  Internet is a “network of networks”

Ø  A packet passes through many networks

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP Tier-2 ISP Tier-2 ISP

local ISP local

ISP local ISP

local ISP

local ISP Tier 3

ISP

local ISP

local ISP

local ISP

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Organizing the Structure

q  Networks are diverse and complex Ø  Many pieces and many designers

§  Hosts §  Routers §  Links of various media §  Applications §  Protocols §  Hardware, software

Use layering for accommodating diversity and managing complexity

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Why Layering? q  Explicit structure allows identification, relationship of

complex system’s pieces

q  Modularization eases maintenance, updating of system Ø  Change of implementation of a layer transparent to rest

of system

q  Standard, well-defined interfaces a must Ø  Single, simple IP glues the Internet together

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q  Application layer Ø  Supporting network applications

§  ftp, SMTP, HTTP

q  Transport layer Ø  Host-host data transfer

§  TCP, UDP

q  Network layer Ø  Routing of packets from source to

destination §  IP, routing protocols

q  Link layer Ø  Data transfer between directly

connected network elements §  Ethernet, 802.11, SONET, …

q  Physical layer Ø  The insertion of individual bits “on the wire”

application

transport

network

link

physical

Different services specified at each layer

interface

Internet Protocol Stack

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Impact of Wireless on Protocol Layers Application layer Transport layer Network layer Data link layer Physical layer

service location new/adaptive applications multimedia congestion/flow control quality of service addressing, routing device location hand-over authentication media access/control multiplexing encryption modulation interference attenuation frequency

history & context

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