Introduction to wireless communication

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Wireless communication is a complicated and rapidly evolving field. In the marketplace, wireless is marketing-speak for radio frequency. However, there are many technologies besides radio that enable data to be transmitted without wires. This page serves as an overview of some common techniques and technologies.

Physical properties that enable wireless communication

If you were to ignore how the word wireless is used by marketers, at a high level, there are several types of physical properties which could enable wireless communication. Almost all of these are specific usages of the peculiar properties of electromagnetic radiation.

Radio

Radio is electromagnetic radiation at frequencies between 3kHz to 300GHz, which is slower than visible light and infra-red.

Examples uses:

  • garage door openers
  • remote-controlled cars
  • microwave ovens
  • cell phones communicate with cell towers via radio
  • wi-fi is an application of radio whereby your computer communicates with a router via microwave radio
  • bluetooth is yet another application of radio communication in personal computing
  • GPS is a radio signal broadcast by satellites and received by GPS receivers
  • RFID prevents theft and helps in inventory management systems
  • etc. etc.


Light transmission

Light is electromagnetic radiation at frequencies between 430 THz to 790 THz. Some of it is visible to human eyes, some is not.

Example uses:


Electrical capacitance

Capacitance is the ability of a body to store electric charge. Thus capacitance is another manifestation of the electromagnet force. Capacitive sensors can detect the charge difference between two charged bodies.

Example uses:

Magnetism

Magnetism is yet another aspect of the same electromagnetic phenomenon as radio, light, and capacitance. Magnetic force is present everywhere there is electrical current, as well as innately in some ferromagnetic materials.

Example uses:

Sound

Sound is produced by air pressure changes, which cause a line of air molecules, starting from the sound source, to bump into each other until some of them reach your inner ear, at which point you "hear" it.

Example uses:

Applications of wireless technology

Broadcasting

Sending out a signal but not expecting a response back.

Examples:

  • FM, AM, and satellite radio
  • garage door openers
  • remote-controlled cars
  • GPS
  • lighthouse
  • TV remote-controls
  • The Clapper
  • some capacitance-based devices


Voice communication

Sending out a voice signal and receiving a response, thereby allowing for a dialogue.

Examples:

  • Ham radio (two-way radio communication)
  • mobile phone

Data communication

Sending out a data signal and receiving a response, thereby allowing for a dialogue:

Examples:

  • wi-fi
  • bluetooth
  • mobile phone data service
  • RFID
  • CD and DVD optical transceivers
  • some capacitance-based devices


Location mapping

Locating an object in 2D or 3D space.

Examples


Comparison of popular wireless protocols

Bluetooth

  • named after Harald Bluetooth, who united the Danish tribes
  • the logo is based on two runes representing Harald's initials
  • uses short distance UTF signals (10m for Bluetooth 3, 60m for Bluetooth 4, 240m for Bluetooth 5)
  • medium data rate (25 Mbit/s for Bluetooth 3 & 4, 50 Mbit/s for Bluetooth 5)
  • medium power consumption
  • commonly built into laptops, phones, and a wide variety of available computer peripherals
  • requires 'pairing' of devices, so requires manual setup
  • not useful for mesh-type ad-hoc networks
  • communicates with Arduino via serial RX and TX pins

Low-energy Bluetooth

  • a variant of Bluetooth
  • low power consumption
  • low data rate
  • good for battery-powered applications with low-intensity communication needs

Wifi

  • high data rate (54 Mbit/s +)
  • high power consumption
  • connect through central router to Internet
  • best when power supply is not an issue

XBee

  • low data rate (250kbit/s)
  • low power consumption
  • good for mesh-type ad-hoc networks
  • each XBee device can communication with each other
  • each XBee can communication through others to devices out of range
  • great for mesh-type ad-hoc networks with no central hub

nRF24L01 / RFM12B / RFM22B(SI4432)

  • popular proprietary transceivers with good Arduino support
  • can connect via SPI and have a lot of fancy features like low power modes, multiple channels, channel hopping, frequency calibration, CRC, retransmit and so on.
  • the nRF24L01 from Nordic Semiconductor] operates in the 2.4GHz band, others use the ISM band 433/470/868/915Mhz
  • great state of the art highly integrated and low cost hardware for reliable telemetry and consumer applications
  • range is between 10m and 150m.
    • SI4432/RFM22B has the range of about 1.5Km

Other RF modules

  • There are many simple cheap devices.
  • transmitter/receiver pairs, or single transceivers that operate in the ISM radio band
  • often used as garage door openers, etc
  • good for custom networks where interoperability with other devices is not required


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