WiFi algorithm, CSMA/CA

Wireless - broadcast network implemented over short* distance radio
communication.

Different electro-magnetic frequency ranges assigned to  
  Television VHF/UHF, AM, FM, shortwave, cell-phones, blue-tooth, 
  satellite, walkie-talkies, CB, etc. 

  So, only certain ranges available for WiFi.

See WiFi and 802.11 on wikipedia.

IEEE 802.11 (1991) (a-n, various revisions and tweaks).
  3 major revisions and several tweaks.

  Available frequencies
  Standard describes 5 licensed frequency ranges the gigahertz range :
    2.4, 3.6, 4.9, 5, 5.9

    Ranges are further broken into channels.

  2.4 GHz(b/g/n) - most countries.
 
  3.65 GHz - wide area wireless - U.S. only.
    * used by satellites elsewhere in the world.

  4.9 GHz - U.S. Public Safety WLAN (2 channels)

  5 GHz(a/hj/n/ac) - many channels. Different countries select different
    channels.

  5.9 GHz - used for wireless interface for devices in vehicles.

  ***
  2 additional non-licensed frequencies.

  900 MHz - (802.11ah) unlicensed. Long distances or very low power.
    Sensors (Internet of things) Like Bluetooth but wider range.

  60 GHz - unlicensed, very high speed, cannot penetrate walls, but can 
    bounce off of objects offering high saturation in room.

  Throughput of data is about 1% of frequency without multiplexing signals.
    But tricks like phase shifting and compression can increase throughput.

http://www.speedguide.net/faq/what-is-the-actual-real-life-speed-of-wireless-374

Major frequency is divided into sub-ranges or channels which 
  allows multiple devices or stations to use the same access point.  

  https://en.wikipedia.org/wiki/List_of_WLAN_channels

  * 2.4 GHz - 2.412, 2.417, 2.422, 2.427, 2.432, 2.437, 2.442, 2.447,
              2.452, 2.457, 2.462, 2.467, 2.472, 2.484 (US?)

  * Similar to how the television broadcast spectrum is broken into channels.
  * Consider switching channels if you WiFi under performs.
  * Channels in the 2.4 GHz range overlap so :
    * Can't use channels next to each other, so not all available.
      Usually only 3 to 5 of the channels.
    * access point will use channels at least 22 MHz apart.

  * Channels in the 5 GHz range don't overlap and more are available.

Because channel frequencies overlap, only a few channels useful.
   
Implemented in half-duplex - a device can either send or receive but
  not both at same time on any one channel.

Wireless network is combination of stations (end points) and access nodes.
  Access nodes usually interconnected using standard copper LAN and Ethernet
    protocol.

  Individual access points directly bridged wirelessly to create a 
    truly wireless local network.

Also wireless stations can be set up peer to peer without an access node,
  but then network is truly private.

Wireless access points are configured so that they appear to have a 
  common link layer (same local network id - SSID). e.g NIUwireless

  SSID - service set identification - 32 octet ID which IDs/ensures the 
     interaction between an access node and a station that has established
     a connection to it.
     * This allows different devices to connect to different nodes/networks.
     * Often human readable.

Multiple devices can interleave communication packets on a particular
  channel and follow the CSMA/CA protocol when competing for band width.