Wireless data networks Why is wireless different? Martin Heusse X - - PowerPoint PPT Presentation

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Wireless data networks Why is wireless different? Martin Heusse X - - PowerPoint PPT Presentation

Apr 07, 2023 167 likes •340 views

Wireless data networks Why is wireless different? Martin Heusse X L A TEX E General info This is TLEN 5520, or ECEN 5032 ECCS 1B12, WF, 3:00pm to 4:15pm Please register to the class mailing list! send a mail to

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X E L

ATEX

Wireless data networks Why is wireless different?

Martin Heusse

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SLIDE 2

X E L

ATEX

General info

  • This is TLEN 5520, or ECEN 5032
  • ECCS 1B12, WF, 3:00pm to 4:15pm
  • Please register to the class mailing list!

✓ send a mail to listproc@lists.Colorado.edu ✓ body: subscribe tlen5520-s09 <Your Full Name>

  • Web site: http://morse.colorado.edu/~tlen5520/
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SLIDE 3
  • Intro. 3

History — what are we talking about?

Audio CD (82)

DECT

1930 1940 1950 1960 1970 1980 1990 2000 2010 HF VHF UHF SHF EHF Infrared Shortwave radio B&W TV FM radio 3MHz 30MHz 300MHz 3GHz 30GHz 300GHz Color TV Satellite (experimental) Cordless phone Cell phone Satellite communications IR WLAN WiMAX IRIDIUM

  • sat. to sat.

Walkie Talky

“Mobile” phone CB radio Digital era WLAN 3G 4G / LTE AlohaNet Twisted pair Coax λ f 1m 10cm 1mm 1cm DVB-T DAB

IBM PC (81) Arpanet

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SLIDE 4
  • Intro. 4

Wireless data networks

Session Transport Network Link Physical

HTTP

MIME HTTP

Cookies

TCP

IP

Application Presentation

PPP

(HDLC framing)

RS-232

11a 11b

…

UDP

SCTP (adresses, security, channel access, ARQ)

  • Phy. Layer Converg. Protocol
  • Phy. medium dependent

MAC …

DNS FTP SSH X11 …

LLC

10baseT 100baseTX 6Mb/s 9Mb/s

… XDR

SLIP

SSL Session

Ethernet 802.11

Blue- tooth

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SLIDE 5
  • Intro. 5

The wireless channel

  • Free space propagation

✓ Typical attenuation: λ = 0.1m, d = 1m → -30dB (1/1000!) ✓ Attenuation # 1

dn with 2 ≤ n

At best, the radiated power is projected on (a part of) a sphere whose surface grows in the order of

1 4πd2 .

✓ May be worse!

  • The atmosphere is (mostly) transparent

✓ 10−2dB/km attenuation for radio waves in the air ✓ Twisted pair: > 1dB/100m ✓ Attenuation is exponential! (and so it makes sense to measure attenuation in dB) ✓ Strong attenuation in concrete, metal; varies with λ

→ Good for long distance communications (if only the world was flat…) → Strong attenuation, even over short distances

  • No confinement

✓ …

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SLIDE 6
  • Intro. 6

Radio waves

  • Propagation

✓ Ground wave

◮ f < 2MHz; (…) ◮ AM radio

✓ Sky wave (Reflection on the ionosphere) ★ Line of sight

  • Diffraction, refraction, absorption, scattering
  • Multi-paths, fading
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SLIDE 7
  • Intro. 7

Radio waves (cont.)

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SLIDE 8
  • Intro. 8

Digital transmission Channel capacity

  • Channel characteristics

✓ Bandwidth ✓ Signal to Noise power ratio (Signal power imited by regulation, amplifier performance, distance, antenna…)

  • Nyquist bandwidth

✓ Channel width B (Hz) → 2B (bauds) max trans. rate ✓ (bauds ⇔ symbols/s) ✓ POTS modems had a capacity of 56kb/s on a channel several kHz wide… ← multilevel signaling

  • Shannon capacity (How many levels can I use?)

✓ The signal is subject to noise. If levels are too close from each

  • ther, there is a risk of error!

C = B log2(1 + SNR) where SNR is the ratio of power in the signal to the power in the noise.

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SLIDE 9
  • Intro. 9

Physical layer for wireless

  • Antennas

✓ Why does an antenna radiate power? ✓ Radiation pattern

EHIJ I08N L39, O21, L39, K2-3/ L39,4 K02- L39, P?==

Example: cellular net. antennas point toward the ground ✓ Polarization

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SLIDE 10
  • Intro. 10

Physical layer for wireless (cont.)

  • Not baseband transmission! (→ modulation)
  • Synchronisation (→ preamble)

(Ex.: for ASM, to which level does a logical “1” correspond?)

  • Spread spectrum

✓ Can help to reduce impact of noise ✓ Does not work for e.g. white noise

  • Error detection, correction
  • Scrambling
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SLIDE 11
  • Intro. 11

Link layer for wireless

  • ARQ
  • Association information

✓ Which network am I connecting to? → Beacons / discovery

  • Multiplexing / channel sharing

✓ (Sub) Channel choice ✓ Channel access

◮ Centralized ◮ Localized ( distributed)

  • Addressing (may include a relay address…)
  • Fragmentation/reassembly
  • Power management

✓ Idle listening is also power consuming

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SLIDE 12
  • Intro. 12

Multiplexing

☛ ✡ ✟ ✠

Multiplexing: several entities or flows share the same transmission channel

  • In time

✓ CSMA ✓ TDMA (GSM: 8 uni-directional connection/freq. band)

  • Frequency

FDMA: GSM, DECT, 802.11

  • Code

✓ CDMA (3G) ✓ Frequency hopping (Bluetooth)

  • Spatial
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SLIDE 13
  • Intro. 13

An example: DECT

Digital Enhanced Cordless Telecommunications

  • 32kb/s; 1920 MHz–1930 MHz (US);

(G)FSK

  • FDMA + TDMA
  • The base station transmits

permanently in one slot (→ discovery)

  • Encryption
  • Several data profiles (e.g. HDLC

framing etc.)

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SLIDE 14
  • Intro. 14

Applications of wireless networks

  • Long distance links
  • Cellular phones

★ Wireless LAN (802.11) ★ Internet access (802.11, 802.16—WiMAX) ★ Wireless personal area network (802.15.1—Bluetooth)

✓ High rate, short range, low power consumption

★ Sensor networks (802.15.4—Zigbee)

✓ Low power consumption

* Ad hoc networks (Mobile multihop network)

✓ Routing ✓ Performance issues

* Mesh networks

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SLIDE 15
  • Intro. 15

Radio spectrum—FCC Freq. alloc.

NON-GOVERNMENT EXCLUSIVE GOVERNMENT/NON-GOVERNMENT SHARED GOVERNMENT EXCLUSIVE

ACTIVITY CODE

3 x 105m 30,000 m 3,000 m 300 m 30 m 3 m 30 cm 3 cm 0.3 cm 0.03 cm 3 x 105Å 1 kHz 10 kHz 100 kHz 1 MHz 10 MHz 100 MHz 1 GHz 10 GHz 100 GHz 1 THz 1013Hz

THE RADIO SPECTRUM

MAGNIFIED ABOVE

3 kHz 300 GHz

ENCY (VLF)

e Range AM Broadcast FM Broadcast Radar Sub-Millimeter Sonics Ultra-sonics Microwaves Infrared P L S X C Radar Bands

LF MF HF VHF UHF SHF EHF INFRARED

http://www.ntia.doc.gov/osmhome/allochrt.pdf http://www.fcc.gov/oet/spectrum/table/fcctable.pdf

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SLIDE 16
  • Intro. 16

Radio spectrum—FCC Freq. alloc. (cont.)

S)

300 MHz 3 GHz

BROADCASTING (TV CHANNELS 7-13) MOBILE FIXED MOBILE FIXED MOBILE SATELLITE MOBILE** FIXED

AERONAUTICAL RADIONAVIGATION Radiolocation Radiolocation MARITIME RADIONAVIGATION

MOBILE FIXED

FIXED Land Mobile FIXED MOBILE Radiolocation Radiolocation LAND MOBILE AMATEUR AIDS (Radiosonde) SATELLITE (s-E)

Fixed FIXED

  • MET. SAT.

(s-E) FIXED FIXED FIXED MOBILE FIXED

FIXED (LOS) MOBILE (LOS) SPACE RESEARCH (s-E)(s-s) SPACE OPERATION (s-E)(s-s) EARTH EXPLORATION

  • SAT. (s-E)(s-s)

Amateur

MOBILE Fixed RADIOLOCATION AMATEUR RADIO ASTRON. SPACE RESEARCH EARTH EXPL SAT

173.2 173.4 174.0 216.0 220.0 222.0 225.0 235.0 300 2000 2020 2025 2110 2155 2160 2180 2200 2290 2300 2305 2310 2320 2345 2360 2385 2390 2400 2417 2450 2483.5 2500 2655 2690 2700 2900 3000 1700 1710 1755 1850 ISM – 2450.0 ± 50 MHz

Amateur

MOBILE

F I X E D F i x e d M o b i l e R a d i o - l o c a t i o n F I X E D M O B I L E

METEOROLOGICAL AIDS

FX

Space res. Radio Ast E-Expl Sat

FIXED MOBILE**

MOBILE SATELLITE (S-E) RADIODETERMINATION SAT. (S-E) Radiolocation

MOBILE FIXED

Amateur Radiolocation

AMATEUR FIXED MOBILE B-SAT

FX

MOB

Fixed Mobile Radiolocation

MOBILE MOBILE SATELLITE (E-S)

SPACE OP. (E-S)(s-s) EARTH EXPL.

  • SAT. (E-S)(s-s)

SPACE RES. (E-S)(s-s)

FX. MOB. MOBILE FIXED

Mobile R- LOC.

BCST-SATELLITE

Fixed Radio- location B-SAT R- LOC. FX

MOB

Fixed Mobile Radiolocation

FIXED MOBILE** Amateur

RADIOLOCATION SPACE RES..(S-E)

MOBILE FIXED MOBILE SATELLITE (S-E) MOBILE FIXED

FX-SAT (S - E)

BCST - SAT.

B- SAT. MOB** FX-SAT