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) ZigBee (2004) Wikipedia

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

Radio basics FCC 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

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

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

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

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

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, …

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

FCC – allocation chart FCC

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 duty cycle <0,1% 869.4-869.65 500 mW duty cycle <10% 869.7-870.0 5 mW duty cycle 100% User or provider responsibility to maintain limits!

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, ………………………….

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)

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), … Standard 802.11 Band GHz Data rate max Mbps Range m Year Modulation - 2.4 2 20 -100 1997 FH/DSSS a 5 54 35 - 120 1999 OFDM b 11 38 - 140 DSSS g 2003 n 2.4 / 5 600 70 - 250 2009 Wikipedia, IEEE

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

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

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.

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

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

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

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)

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

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

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

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

Comparison Technology 802.11b 802.15.1 802.15.4 Target application Web, Email, Video Voice, Cable replacement Monitoring and control Flash size 1MB+ 250KB+ 25KB - 70KB Battery life (days) 0.5 - 5 1 - 7 100 - 1,000+ Basic network 32 / … 7 / … 255 / 65535 Throughput (kbps) 11,000+ 1000 20 - 250 Range (m) 1 – 100+ 1 - 100+ 1 – 75+ Advantage Speed, flexibility (IP) Price, convenience Low power, simple

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

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