Wireless Communication Basics

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Wireless Communication Basics
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RF Basics

• Basic Communication System
• Transmitter and Receiver

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RF Basics

• Basic Communication System
• Transmitter and Receiver
• Transmitting Antenna

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RF Basics

• Basic Communication System
• Transmitter and Receiver
• Transmitting Antenna
• Receiving Antenna

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RF Basics

• Basic Communication System
• Transmitter and Receiver
• Transmitting Antenna
• Receiving Antenna
• Environment

Environment
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RF Basics

• Maximizing Range

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RF Essentials

• Maximizing Range
• Increase Transmitter (TX) Power
• Government Regulated
• Low-powered Applications

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RF Essentials

• Maximizing Range
• Increase Transmitter (TX) Power
• Increase Receiver (RX) Sensitivity
• Specified in dBm
• Every 6 dB doubles the range LOS
• Every 12 dB doubles range indoors / urban
  environments

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RF Basics

• Maximizing Range
• Increase Transmitter (TX) Power
• Increase Receiver (RX) Sensitivity
• Increase Antenna Gain
• More gain equates with more focusing of energy
• Antenna cables should be as short as possible

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RF Basics

• Basic Communication System
• Transmitter and Receiver
• Transmitting Antenna
• Focused energy

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RF Basics

• Basic Communication System
• Transmitter and Receiver
• Transmitting Antenna
• Receiving Antenna
• Focused energy

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RF Basics

• Antenna Gain
• Government-imposed power restrictions
• Omnidirectional

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RF Basics

• Antenna Gain
• Directional

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RF Basics

• Maximizing Range
• Increase Transmitter (TX) Power
• Improve Receiver (RX) Sensitivity
• Increase Antenna Gain
• Clear the Environment of obstructions
• Visual (Linear) line-of-sight vs. RF (Radio)
  line-of-sight

Clear the Environment
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RF Basics

• Fresnel Zone
• Football-shaped path

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RF Basics

• Fresnel Zone
• Football-shaped path
• Acceptable 60 of Zone 1 3 meters
• Raise antennas to help clear the zone

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RF Basics

• Fresnel Zone
• Football-shaped path
• Acceptable 60 of Zone 1 3 meters
• Raise antennas to help clear the zone
• Formula

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RF Basics

• Fresnel Zone Diameters

Range Distance 868 MHz Modems Required Fresnel Zone Radius 2.4 GHz Modems Required Fresnel Zone Radius
1 m 0,29 m 0,18 m
3 m 0,51 m 0,31 m
10 m 0,93 m 0,56 m
30 m 1,61 m 0,97 m
100 m 2,94 m 1,77 m
300 m 5,09 m 3,06 m
1600 m 11,76 m 7,07 m
8000 m 26,29 m 15,81 m
16000 m 37,18 m 22,36 m
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Importance of Frequency Selection

• Geographic Deployment
• Worldwide versus Regional
• RF Performance
• Range
• RF Penetration
• Antenna Considerations

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License-Free Bands
2.4 GHz
315 MHz 420 MHz 900 MHz 5.7 GHz
433 MHz 868 MHz 5.7 GHz
900 MHz
433 MHz
915 MHz
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Regulatory Bodies

• FCC (United States)
• IC (Canada)
• ETSI (Europe, some APAC)
• C-Tick (Australia
• Telec (Japan)
• Anatel (Brazil)

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Rates and Ranges
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Nodes
Nodes and Rates
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Radio Modem Operation

• Modem
• Modulate / Demodulate

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Modulation

• What is modulation?
• The process by which a parameter (amplitude,
  frequency or phase of a sinusoidal signal) of a
  higher frequency carrier wave is altered in
  accordance with the baseband message signal.
• Transforms the message signal into a form that is
  suitable for transmission over the channel.
• The transmitter uses the baseband message signal
  to modulate a carrier and transmit it over the
  channel.

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Radio Modem Operation

• Two types of spread spectrum used in modern
  Radios
• FHSS- Frequency Hopping Spread Spectrum
• Transmitter rapidly hops from one channel to the
  next in a pseudo-random fashion, avoiding
  long-term interference.
• Receiver follows transmitter
• Some Digi Products use FHSS
• 24XStream

2400
2480
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XStreamKey Features

• Price-to-Performance Value
• High Receiver Sensitivity
• Low Power Consumption
• FCC (U.S.A.), IC (Canada),
• ETSI (Europe) Approved

Best Value OEM RF Modules 2.4GHz
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XStream (2.4 GHz)Best Value OEM RF Modules
Specifications Specifications
Indoor/urban Range up to 180 m
Outdoor line-of-sight Range up to 16 km
Transmit Power Output 50 mW (17 dBm)
Receiver Sensitivity -105 dBm _at_9600 bps
Operating Frequency 2.45-2.46 GHz
Operating Voltage 5V (OEM) 7-18 (Boxed)
RF Data Rate 9600 or 19200 bps
Interface Packages Available
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Radio Modem Operation

• Two types of spread spectrum used in modern
  Radios
• DSSS- Direct Sequence Spread Spectrum
• Each bit is represented by N, shorter segments,
  called chips.
• Increases over-the-air rate by a factor of N,
  widening the spectrum
• Correlator in receiver examines the chips and
  maps chips back to bits, while simultaneously
  spreading undesired signals
• Processing gain, 10log(chip_rate/bit_rate)
• Some Digi productsuse DSSS
• XBee
• XBee-Pro
• All WiFi enabledproducts

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Digi RF Products
Packaged (Boxed)
Modules (Embedded)
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DigiRF Products

• XBee
• XStream
• XTend
• XPress
• XCite
• Digi Mesh

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Digi RF Modules
Product Name Frequency Power Output Indoor RangeOutdoor Range Data Rate
XBee 2.4 GHz 1 mW 30 meters100 meters 250 Kbps
XBee-PRO 2.4 GHz 10 mW 19 mW (EIRP) 80 meters800 meters 250 Kbps
9XTend 900 MHz 1 Watt 900 meters64 kilometers 115 Kbps
9XStream 900 MHz 100 mW 450 meters32 kilometers 19.2 Kbps
24XStream 2.4 GHz 50 mW 180 meters16 kilometers 19.2 Kbps
9XCite 900 MHz 4 mW 90 meters300 meters 38.4 Kbps