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)
(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
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 = m.s-1

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 ~ 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: n bandwidth B = 40 MHz, SNR = 25 dB, rate 600 Mbps
C = log2 (1+25dB) = 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

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)
European Communications Office (ECO)
European Telecommunications Standards Institute (ETSI)
Český telekomunikační úřad (CTU)
Federal Communications Commission (FCC)
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
433 MHz 10 mW
2.4 GHz mW EIRP, 10 mW / 1MHz (DSSS)
5.8 GHz mW EIRP
GHZ 100 mW EIRP
Short Range Devices (SRD) MHz – ERC 70-03
mW duty cycle <1%
mW duty cycle <0,1%
mW duty cycle <10%
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 , WiMAX Forum
Broadband wireless access
last-mile wireless internet connection
m, km, max. 75 Mbps, max. 50 km
2-11 GHz, 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), …
Standard
802.11
Band
GHz
Data rate
max Mbps
Range m
Year
Modulation -
2.4 2
1997
FH/DSSS a 5 54
1999
OFDM b 11
DSSS g
2003 n
2.4 / 5
600
2009
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
20, m
QoS, security, frequency selection, power control
“better” than original , but expensive, …
Development stopped, market dominated by Wi-Fi
Some concepts reused in WiMAX and n

18. PAN networks WirelessPAN – IEEE 802.15 802.15.1 → Bluetooth
(high-rate PAN) → UWB
(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 (PHY+MAC)
Voice communication, cable replacement, …
Versions 1.0, 1.1, 1.2, 2.0, 2.1, 3 (April/2009)
Version 3: original radio 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
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 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 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 radio
Provide Internet reach to small devices

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

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
M.Welsh: Wireless Communication Basics