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Wireless Communications

Wireless Communications. Wireless - history. Hertz – detection of radio waves (1887) Tesla – radio transmission (1893) Marconi – transatlantic transmission (1901) Communication satellites (1962) ALOHAnet (1970) First GSM call (1991) 802.11 (1997) Bluetooth (2000) WiMax (2004)

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Wireless Communications

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  1. Wireless Communications

  2. Wireless - history Hertz – detection of radio waves (1887) Tesla – radio transmission (1893) Marconi – transatlantic transmission (1901) Communication satellites (1962) ALOHAnet (1970) First GSM call (1991) 802.11 (1997) Bluetooth (2000) WiMax (2004) ZigBee (2004) Wikipedia

  3. Why use wireless today? Why wireless? - Convenient, cheaper installation • Remote areas, moving parts/mobility, small devices • Many devices in one area – simple installation • Easy interfacing (no connectors) • Often the only choice Why not? - Not perfect, limitations • Reliability • Security • Interference Wikimedia Commons

  4. Radio basics Radio frequency is an electromagnetic signal with a frequency in range from 3 kHz to 300 GHz frequency f [Hz] wavelength λ [m] λ = c / f speed of light c [m.s-1] c = 299 792 458 m.s-1 FCC

  5. Radio basics How to convey information? Modulation. • Carrier signal ← modulate amplitude/frequency/phase • Analog / digital modulation (AM, FM, ASK, FSK, …) • Spread spectrum (DSSS, FHSS, …) • Ultrawideband (PPM, THSS, CSS) Wikipedia Wikimedia Commons

  6. Radio propagation Radio propagation • Ground-wave propagation (f < 2 MHz) • Sky-wave propagation (f ~ 2 - 30 MHz) • Line-of-Sight (LOS) propagation (f > 30 MHz) • Multipath: • Reflection • Scattering • Difraction

  7. Radio propagation Channel capacity • Data rate [bps] • Bandwidth [Hz] • Error rate – BER, PER • Noise – SNR, Eb/No Theoretical limit: Shannon formula C = B.log2(1+SNR) C – capacity [bps], B – bandwidth [Hz] Example: 802.11n bandwidth B = 40 MHz, SNR = 25 dB, rate 600 Mbps C = 40.106.log2 (1+25dB) = 40.106.log2 (1+316) = 332 Mbps why?? cnx.org

  8. Radio propagation LOS signal impairments: • Attenuation, distortion • Free space loss • Noise • Thermal noise • Intermodulation noise • Crosstalk • Impulse noise • Atmospheric absorption • Multipath • Refraction www.mike-willis.com

  9. dB, mW, dBm, dBW … • The signal strength is expressed as power [W] • The gain/loss is ratio between output and input power. GaindB = 10 log10 Pout /Pin [dB] i.e. 10x more power = 10 dB, 100x less power = -20 dB, … • Absolute levels can be expressed in decibels when referenced to a signal level: • dBW (decibel-Watt) is power referenced to 1 W • dBm (decibel-milliWatt) to 1 mW. i.e. PowerdBm = 10 log10 PmW / 1 mW [dBm], 0 dBm = 1 mW, …

  10. Legal issues • Spectrum is allocated to prevent interferences International Telecommunication Union (ITU) http://www.itu.int/ European Communications Office (ECO) http://www.ero.dk/ European Telecommunications Standards Institute (ETSI) http://www.etsi.org/ Český telekomunikační úřad (CTU) http://www.ctu.cz/ Federal Communications Commission (FCC) http://www.fcc.gov/ • ITU – recommendations • National frequency allocation table and utilization

  11. FCC – allocation chart FCC

  12. Unlicensed • Portions of the spectrum reserved for unlicensed use, some globally • Industrial, Scientific, Medical (ISM) Band – ETSI 300-328 • 433 MHz 10 mW • 2.4 GHz 100 mW EIRP, 10 mW / 1MHz (DSSS) • 5.8 GHz 25 mW EIRP • 24.125 GHZ 100 mW EIRP • Short Range Devices (SRD) 868-870 MHz – ERC 70-03 • 868.0-868.6 25 mW duty cycle <1% • 868.7-869.2 25 mW dutycycle <0,1% • 869.4-869.65 500 mW dutycycle <10% • 869.7-870.0 5 mW duty cycle 100% • User or provider responsibility to maintain limits!

  13. Communication standards Metropolitan networks - Wireless MAN (WMAN) • WiMAX • Cellular (GPRS, EDGE, UMTS…) Local networks - Wireless LAN (WLAN) • WiFi, HIPERLAN • DECT Short range networks - Wireless PAN (WPAN) • Bluetooth, ZigBee, Z-Wave, WiBree, nanoNET, UWB, Wireless USB, WirelessHD, WirelessHART, RFID, 6LoWPAN, WirelessFirewire, ………………………….

  14. WiMAX WiMAX (Worldwide Interoperability for Microwave Access) • IEEE 802.16, WiMAX Forum • Broadband wireless access • last-mile wireless internet connection • 20 Mbps@ 600 m, 10 Mbps @ 10 km, max. 75 Mbps, max. 50 km • 2-11 GHz, 10-66 GHz, 3.5 GHz in Czech Rep. (licensed) • Shared channel – FDD • LOS not required – suitable for urban • Mobile WiMAX available (802.16e)

  15. Wi-Fi Wi-Fi (not an abbreviation) • Wi-Fi Alliance, IEEE 802.11 • WLAN “de facto” standard • IP technology compatible, defines PHY and MAC • Amendments: mesh (802.11s), security (802.11i), QoS (802.11e), … Wikipedia, IEEE

  16. Wi-Fi • Coordinated/distributed (AP/Ad-hoc) • Beacon-synchronization • Contention free access • Security, authentication • Mobile (802.11r) and high throughput variants (802.11ac/ad) under way VAN

  17. HIPERLAN HIPERLAN (High Performance Radio LAN) • European ETSI standard for WLAN, alternative to 802.11 • 20, 54 Mbps @ 30-150 m • QoS, security, frequency selection, power control • “better” than original 802.11, but expensive, … • Development stopped, market dominated by Wi-Fi • Some concepts reused in WiMAX and 802.11n

  18. PAN networks WirelessPAN – IEEE 802.15 • 802.15.1 → Bluetooth • 802.15.3 (high-rate PAN) → UWB • 802.15.4 (low-rate PAN) → ZigBee, WirelessHART, 6LoWPAN,ISA100, … • Others: Body Area networks, Visible light communications, etc.

  19. Bluetooth Bluetooth (symbolic name) • Bluetooth Special Interest Group (SIG) • IEEE 802.15.1 (PHY+MAC) • Voice communication, cable replacement, … • Versions 1.0, 1.1, 1.2, 2.0, 2.1, 3 (April/2009) • Version 3: original radio + 802.11 for high rate • Future? UWB, broadcasts, topology management

  20. Bluetooth • Profile-based communication • FHSS over 79 channels in 2.4 GHz band • Device discovery • Synchronous, asynchronous data • Master/slave • Piconet, Scatternet VAN

  21. Wibree → Bluetooth low energy • Proprietary radio (Nokia) originally candidate for 802.15.4 • Intended as low-power supplement to Bluetooth • April/2009 addition to Bluetooth stack, compatible • 200 kbps (net), < 15 mA peak current

  22. ZigBee ZigBee (just a name) • Low cost, low energy, low rate mesh networks • Based on 802.15.4 radio, defines upper layers • FFD/RFD devices, mesh self-healing topology • Enables low power consumption in end-devices • First version in 2004, current ZigBeePRO (2007)

  23. ZigBee • Defines full stack, up to application layer • Communication based on profiles • Home automation profile, RF4CE,… • Works in 2.4 GHz and 868 (900) MHz bands Freescale

  24. Z-Wave Z-Wave (by Zensys) • Another standard for home automation • Competitor to ZigBee (in home automation) • Proprietary radio at 868 MHz, 40 kbps • Does not define profiles, based on command sets • In use longer than ZigBee, but not so well known

  25. WirelessHART WirelessHART (wireless Highway Addressable Remote Transducer ) • Built on 802.15.4 radio and Dust Networks technology • Enables transparent connection of HART devices • Part of HART7 specification • Targeted at automation – remote transducers

  26. 6LoWPAN 6LoWPAN (IPv6 over Low power WPAN) • Implementation of IPv6 protocol • Based on 802.15.4 radio • Provide Internet reach to small devices

  27. Comparison

  28. Other standards • UWB (Ultra Wide Band) • WirelessUSB, WirelessFirewire, • WirelessHD • RFID • EnOcean • ONE-NET • nanoNET • NFC • DSRC (WAVE, Car2Car) • ….?

  29. Resources and references • W.Stallings: Wireless Communication & Networks • http://wirelesshistory.org/ • http://www.wikipedia.org/ • http://www.bluetooth.com/ • http://www.zigbee.com/ • M.Welsh: Wireless Communication Basics

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