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Wireless Communications

Explore the history, benefits, and limitations of wireless communication, including its convenience, installation cost savings, and suitability for remote areas and small devices. Discover key wireless technologies and their applications.

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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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