introduction - 건국대학교 - 나라를 세우고 세계를 품는...

Copyright © 2011, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved 1

Chapter 1

INTRODUCTION


Main Topics

n  Cellular networks (3G, LTE, LTE-A)

n  IEEE 802.11 based WLAN (WiFi)

n  NS-3 network simulator

n  NS-3 project n  WiFi throughput


Course Overview

n  Introduction (today)

n  Characteristics of wireless channels

n  Multiple access protocols

n  Cellular networks

n  IEEE 802.11 WLAN

n  NS-3

n  Recent advances


Lecture Outline

n  Interesting ICT statistics

n  Wireless networks

n  Cellular networks v  History and basic concepts

n  IEEE 802.11 wireless LAN v  Overview of features in 802.11 series


ICT Statistics (ITIF, 2013)

n  Refer to PDF


Wireless Networks

n  Cellular networks n  IEEE 802.11 wireless LAN n  Sensor networks n  Ad hoc networks (e.g., vehicular networks) n  Satellite networks

Chapter 6 Wireless and Mobile Networks

Computer Networking: A Top Down Approach 6th edition Jim Kurose, Keith Ross Addison-Wesley March 2012

A note on the use of these ppt slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: v  If you use these slides (e.g., in a class) that you mention their source

(after all, we’d like people to use our book!) v  If you post any slides on a www site, that you note that they are adapted

from (or perhaps identical to) our slides, and note our copyright of this material.

Thanks and enjoy! JFK/KWR All material copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved

Wireless, Mobile Networks 6-1


Ch. 6: Wireless and Mobile Networks Background: v  # wireless (mobile) phone subscribers now exceeds #

wired phone subscribers (5-to-1)! v  # wireless Internet-connected devices equals #

wireline Internet-connected devices §  laptops, Internet-enabled phones promise anytime untethered

Internet access

v  two important (but different) challenges §  wireless: communication over wireless link §  mobility: handling the mobile user who changes point of

attachment to network


Chapter 6 outline

6.1 Introduction

Wireless 6.2 Wireless links,

characteristics §  CDMA

6.3 IEEE 802.11 wireless LANs (“Wi-Fi”)

6.4 Cellular Internet Access §  architecture §  standards (e.g., GSM)

Mobility 6.5 Principles: addressing and

routing to mobile users 6.6 Mobile IP 6.7 Handling mobility in

cellular networks 6.8 Mobility and higher-layer

protocols

6.9 Summary

Hyang-Won Lee

Rectangle


Elements of a wireless network

network infrastructure


wireless hosts v  laptop, smartphone v  run applications v  may be stationary (non-

mobile) or mobile §  wireless does not always

mean mobility




base station v  typically connected to

wired network v  relay - responsible for

sending packets between wired network and wireless host(s) in its “area” §  e.g., cell towers,

802.11 access points




wireless link v  typically used to connect

mobile(s) to base station v  also used as backbone

link v  multiple access protocol

coordinates link access v  various data rates,

transmission distance




Characteristics of selected wireless links

Indoor 10-30m

Outdoor 50-200m

Mid-range outdoor

200m – 4 Km

Long-range outdoor

5Km – 20 Km

.056

.384

1

4

5-11

54

2G: IS-95, CDMA, GSM

2.5G: UMTS/WCDMA, CDMA2000

802.15

802.11b

802.11a,g

3G: UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO

4G: LTWE WIMAX

802.11a,g point-to-point

200 802.11n

Dat

a ra

te (M

bps)


infrastructure mode v  base station connects

mobiles into wired network

v  handoff: mobile changes base station providing connection into wired network




ad hoc mode v  no base stations v  nodes can only

transmit to other nodes within link coverage

v  nodes organize themselves into a network: route among themselves



Wireless network taxonomy

single hop multiple hops

infrastructure (e.g., APs)

no infrastructure

host connects to base station (WiFi, WiMAX, cellular) which connects to

larger Internet

no base station, no connection to larger Internet (Bluetooth,

ad hoc nets)

host may have to relay through several

wireless nodes to connect to larger Internet: mesh net

no base station, no connection to larger Internet. May have to relay to reach other a given wireless node

MANET, VANET


Wireless Sensor Networks

Path of the Response

Radio Range

Data Collection and Monitoring Agency

Cloud of Smoke

Predicted position for the Cloud of Smoke

Path of the ResponsePath of the Response

Radio Range

Data Collection and Monitoring Agency

Cloud of Smoke

Predicted position for the Cloud of Smoke


Ad Hoc Network


Satellite Systems

n  Traditional Applications n  Weather satellite n  Radio and TV broadcasting n  Military satellites

n  Telecommunication Applications n  Global telephone connections n  Backbone for global network n  GPS


Macrocell

Suburban

Coverage Aspect of Next Generation Mobile Communication Systems

Microcell

Urban

Satellite

Global

Global

Picocell

In-building


The History of Mobile Radio Communication (1/3)

n  1880: Hertz – Initial demonstration of practical radio communication n  1897: Marconi – Radio transmission to a tugboat over an 18 mi path n  1921: Detroit Police Department: -- Police car radio dispatch (2 MHz

frequency band) n  1933: FCC (Federal Communications Commission) – Authorized four

channels in the 30 to 40 MHz range n  1938: FCC – Ruled for regular service n  1946: Bell Telephone Laboratories – 152 MHz (Simplex) n  1956: FCC – 450 MHz (Simplex) n  1959: Bell Telephone Laboratories – Suggested 32 MHz band for high

capacity mobile radio communication n  1964: FCC – 152 MHz (Full Duplex) n  1964: Bell Telephone Laboratories – Active research at 800 MHz n  1969: FCC – 450 MHz (Full Duplex) n  1974: FCC – 40 MHz bandwidth allocation in the 800 to 900 MHz range n  1981: FCC – Release of cellular land mobile phone service in the 40 MHz

bandwidth in the 800 to 900 MHz range for commercial operation



n  1981: AT&T and RCC (Radio Common Carrier) reach an agreement to split 40 MHz spectrum into two 20 MHz bands. Band A belongs to nonwireline operators (RCC), and Band B belongs to wireline operators (telephone companies). Each market has two operators.

n  1982: AT&T is divested, and seven RBOCs (Regional Bell Operating Companies) are formed to manage the cellular operations

n  1982: MFJ (Modified Final Judgment) is issued by the government DOJ. All the operators were prohibited to (1) operate long-distance business, (2) provide information services, and (3) do manufacturing business

n  1983: Ameritech system in operation in Chicago n  1984: Most RBOC markets in operation n  1986: FCC allocates 5 MHz in extended band n  1987: FCC makes lottery on the small MSA and all RSA licenses n  1988: TDMA (Time Division Multiple Access) voted as a digital cellular

standard in North America n  1992: GSM (Groupe Speciale Mobile) operable in Germany D2 system



n  1993: CDMA (Code Division Multiple Access) voted as another digital cellular standard in North America

n  1994: American TDMA operable in Seattle, Washington n  1994: PDC (Personal Digital Cellular) operable in Tokyo, Japan n  1994: Two of six broadband PCS (Personal Communication Service) license

bands in auction n  1995: CDMA operable in Hong Kong n  1996: US Congress passes Telecommunication Reform Act Bill n  1996: The auction money for six broadband PCS licensed bands (120 MHz)

almost reaches 20 billion US dollars n  1997: Broadband CDMA considered as one of the third generation mobile

communication technologies for UMTS (Universal Mobile Telecommunication Systems) during the UMTS workshop conference held in Korea

n  1999: ITU (International Telecommunication Union) decides the next generation mobile communication systems

(e.g., W-CDMA, cdma2000, etc)


Fundamentals of Cellular Systems

Illustration of a cell with a mobile station and a base station

BS

MS

Cell MS

Alternative shape of a cell

Ideal cell area (2-10 km radius)

Hexagonal cell area used in most models

Copyright © 2010, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved 15 15

Universal Cell Phone Coverage

Maintaining the telephone number across geographical areas in a wireless and mobile system

Microwave Tower

Cell

Cincinnati

Washington, DC


First Generation Cellular Systems and Services

1970s Developments of radio and computer technologies for 800/900 MHz mobile communications

1976 WARC (World Administrative Radio Conference) allocates spectrum for cellular radio

1979 NTT (Nippon Telephone & Telegraph) introduces the first cellular system in Japan

1981 NMT (Nordic Mobile Telephone) 900 system introduced by Ericsson Radio System AB and deployed in Scandinavia

1984

AMPS (Advanced Mobile Phone Service) introduced by AT&T in North America


Second Generation Cellular Systems and Services

1982 CEPT (Conference Europeenne des Post et Telecommunications) established GSM to define future Pan-European cellular Radio Standards

1990 Interim Standard IS-54 (USDC) adopted by TIA (Telecommunications Industry Association)

1990 Interim Standard IS-19B (NAMPS) adopted by TIA

1991 Japanese PDC (Personal Digital Cellular) system standardized by the MPT (Ministry of Posts and Telecommunications)

1992 Phase I GSM system is operational

1993 Interim Standard IS-95 (CDMA) adopted by TIA

1994 Interim Standard IS-136 adopted by TIA

1995 PCS Licenses issued in North America

1996 Phase II GSM operational

1997 North American PCS deploys GSM, IS-54, IS-95

1999 IS-54: North America IS-95: North America, Hong Kong, Israel, Japan, China, etc GSM: 110 countries


Third Generation Cellular Systems and Services (1/2)

n  IMT-2000 (International Mobile Telecommunications-2000): - Fulfill one's dream of anywhere, anytime communications a reality.

n  Key Features of IMT-2000 include: - High degree of commonality of design worldwide; - Compatibility of services within IMT-2000 and with the

fixed networks; - High quality; - Small terminal for worldwide use; - Worldwide roaming capability; - Capability for multimedia applications, and a wide

range of services and terminals.


Third Generation Cellular Systems and Services (2/2)

n  Important Component of IMT-2000 is ability to provide high bearer rate capabilities: - 2 Mbps for fixed environment; - 384 Kbps for indoor/outdoor and pedestrian

environment; - 144 kbps for vehicular environment.

n  Standardization Work: - In processing

n  Scheduled Service: - Started in October 2001 in Japan (W-CDMA)


Subscriber Growth

3G Subscribers

2G Digital only Subscribers

1G Analogue only Subscribers

Subs

crib

ers

Year


Wireless LAN and PAN

n  Wireless Local Area Network (LAN) using the IEEE 802.11

n  HiperLAN is a European Standard n  Wireless Personal Area Network (PAN)

n  Bluetooth n  HomeRF


Chapter 6 outline

6.1 Introduction








protocols

6.9 Summary


Wireless Link Characteristics (1)

important differences from wired link ….

§  decreased signal strength: radio signal attenuates as it propagates through matter (path loss)

§  interference from other sources: standardized wireless network frequencies (e.g., 2.4 GHz) shared by other devices (e.g., phone); devices (motors) interfere as well

§  multipath propagation: radio signal reflects off objects ground, arriving ad destination at slightly different times

…. make communication across (even a point to point)

wireless link much more “difficult”


Wireless Link Characteristics (2)

v  SNR: signal-to-noise ratio §  larger SNR – easier to

extract signal from noise (a “good thing”)

v  SNR versus BER tradeoffs §  given physical layer: increase

power -> increase SNR->decrease BER

§  given SNR: choose physical layer that meets BER requirement, giving highest thruput

•  SNR may change with mobility: dynamically adapt physical layer (modulation technique, rate)

10 20 30 40

QAM256 (8 Mbps)

QAM16 (4 Mbps)

BPSK (1 Mbps)

SNR(dB)

BER

10-1

10-2

10-3

10-5

10-6

10-7

10-4


Wireless network characteristics Multiple wireless senders and receivers create additional

problems (beyond multiple access):

A B

C

Hidden terminal problem v  B, A hear each other v  B, C hear each other v  A, C can not hear each other

means A, C unaware of their interference at B

A B C

A’s signal strength

space

C’s signal strength

Signal attenuation: v  B, A hear each other v  B, C hear each other v  A, C can not hear each other

interfering at B


Chapter 6 outline

6.1 Introduction




6.4 Cellular Internet access §  architecture §  standards (e.g., GSM)




protocols

6.9 Summary


Mobile Switching

Center

Public telephone network

Mobile Switching

Center

Components of cellular network architecture

v  connects cells to wired tel. net. v  manages call setup (more later!) v  handles mobility (more later!)

MSC

v  covers geographical region v  base station (BS) analogous to 802.11 AP v  mobile users attach to network through BS v  air-interface: physical and link layer protocol between mobile and BS

cell

wired network


Cellular networks: the first hop

Two techniques for sharing mobile-to-BS radio spectrum

v  combined FDMA/TDMA: divide spectrum in frequency channels, divide each channel into time slots

v  CDMA: code division multiple access frequency

bands

time slots


BSC BTS

Base transceiver station (BTS)

Base station controller (BSC)

Mobile Switching Center (MSC)

Mobile subscribers

Base station system (BSS)

Legend

2G (voice) network architecture

MSC Public telephone network

Gateway MSC

G


3G (voice+data) network architecture

radio network controller

MSC

SGSN


Gateway MSC

G

Serving GPRS Support Node (SGSN)

Gateway GPRS Support Node (GGSN)

Public Internet

GGSN

G

Key insight: new cellular data network operates in parallel (except at edge) with existing cellular voice network v  voice network unchanged in core v  data network operates in parallel


radio network controller

MSC

SGSN


Gateway MSC

G

Public Internet

GGSN

G

radio access network Universal Terrestrial Radio Access Network (UTRAN)

core network General Packet Radio Service

(GPRS) Core Network

public Internet

radio interface (WCDMA, HSPA)

3G (voice+data) network architecture


Chapter 6 outline

6.1 Introduction








protocols

6.9 Summary


IEEE 802.11 Wireless LAN 802.11b v  2.4-5 GHz unlicensed spectrum v  up to 11 Mbps v  direct sequence spread spectrum

(DSSS) in physical layer §  all hosts use same chipping

code

802.11a §  5-6 GHz range §  up to 54 Mbps

802.11g §  2.4-5 GHz range §  up to 54 Mbps

802.11n: multiple antennae §  2.4-5 GHz range §  up to 200 Mbps

v  all use CSMA/CA for multiple access v  all have base-station and ad-hoc network versions


802.11 LAN architecture v  wireless host

communicates with base station §  base station = access point

(AP)

v  Basic Service Set (BSS) (aka “cell”) in infrastructure mode contains: §  wireless hosts §  access point (AP): base

station §  ad hoc mode: hosts only

BSS 1

BSS 2

Internet

hub, switch or router


802.11: Channels, association

v  802.11b: 2.4GHz-2.485GHz spectrum divided into 11 channels at different frequencies §  AP admin chooses frequency for AP §  interference possible: channel can be same as that

chosen by neighboring AP!

v  host: must associate with an AP §  scans channels, listening for beacon frames containing

AP’s name (SSID) and MAC address §  selects AP to associate with §  may perform authentication [Chapter 8] §  will typically run DHCP to get IP address in AP’s

subnet


802.11: passive/active scanning

AP 2 AP 1

H1

BBS 2 BBS 1

1 2 3

1

passive scanning: (1)  beacon frames sent from APs (2)  association Request frame sent: H1 to

selected AP (3)  association Response frame sent from

selected AP to H1

AP 2 AP 1

H1

BBS 2 BBS 1

1 2 2

3 4

active scanning: (1) Probe Request frame broadcast

from H1 (2) Probe Response frames sent

from APs (3) Association Request frame sent:

H1 to selected AP (4) Association Response frame sent

from selected AP to H1


IEEE 802.11: multiple access v  avoid collisions: 2+ nodes transmitting at same time v  802.11: CSMA - sense before transmitting

§  don’t collide with ongoing transmission by other node

v  802.11: no collision detection! §  difficult to receive (sense collisions) when transmitting due to weak

received signals (fading) §  can’t sense all collisions in any case: hidden terminal, fading §  goal: avoid collisions: CSMA/C(ollision)A(voidance)

space

A B

C A B C

A’s signal strength

C’s signal strength


M radius of coverage

S

SS

P

P

P

P

M

S

Master device

Slave device

Parked device (inactive) P

802.15: personal area network

v  less than 10 m diameter v  replacement for cables (mouse,

keyboard, headphones) v  ad hoc: no infrastructure v  master/slaves:

§  slaves request permission to send (to master)

§  master grants requests

v  802.15: evolved from Bluetooth specification §  2.4-2.5 GHz radio band §  up to 721 kbps

introduction - 건국대학교 - 나라를 세우고 세계를 품는...

Documents