IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands.
http://en.wikipedia.org/wiki/IEEE_802.11
the most prevalent is 802.11b. Equipment using 802.11b is comparitively inexpensive. The 802.11b wireless communication standard operates in the unregulated 2.4 Ghz frequency range. Unfortunately, so do many other devices such as cordless phones and baby monitors which can interfere with your wireless network traffic. The maximum speed for 802.11b communications is 11 mbps.
The newer 802.11g standard improves on 802.11b. It still uses the same crowded 2.4 Ghz shared by other common household wireless devices, but 802.11g is capable of transmission speeds up to 54 mbps
The 802.11a standard is in a whole different frequency range. By broadcasting in the 5 Ghz range 802.11a devices run into a lot less competition and interference from household devices. 802.11a is also capable of transmission speeds up to 54 mbps like the 802.11g standard, however 802.11 hardware is significantly more expensive.
Bluetooth devices trasnmit at relatively low power and have a range of only 30 feet or so. Bluetooth networks also use the unregulated 2.4 Ghz frequency range and are limited to a maximum of eight connected devices. The maximum transmission speed only goes to 1 mbps.
http://netsecurity.about.com/cs/wirelesssecurity/qt/qt_wifiprotocol.htm
- a wireless personal area network technology designed and marketed by the Bluetooth Special Interest Group aimed at novel applications in the healthcare, fitness, beacons,security, and home entertainment industries
Compared to Classic Bluetooth, Bluetooth Smart is intended to provide considerably reduced power consumption and cost while maintaining a similar communication range.
CSR Mesh protocol uses Bluetooth Smart to communicate with other Bluetooth Smart devices in the network. Each device can pass the information forward to other Bluetooth Smart devices creating a “mesh” effect. For example, switching off an entire building of lights from a single smartphone.
https://en.wikipedia.org/wiki/Bluetooth_low_energy
- Wi-Fi calling is nothing new; apps like Skype, Google Hangouts, Facebook Messenger and WhatsApp make it easier to use a phone to place calls and send texts over the internet and forgo mobile networks altogether.
Carriers are also adopting Wi-Fi calling themselves. Whether it's because they want to bolster their network coverage or improve user experience, several networks have phones that have this service baked in.
Instead of using your carrier's network connection, you can make voice calls via a Wi-Fi network. That could mean using a Wi-Fi connection you have set up at home, or whatever Wi-Fi hotspot you happen to be on when you're out and about, such as at a cafe or library. In most ways, it's like any other phone call, and you still use regular phone numbers.
Wi-Fi calling is especially useful when you're in an area with weak carrier coverage. For example, when you're traveling to the residential countryside, or you're in a building with spotty reception. You may already be familiar with using Wi-Fi to send messages when SMS texting is unavailable (apps like Kik and Facebook Messenger provide these services) -- and the same applies when you're trying to place a call. With Wi-Fi, you can call a friend up even if you're in a dingy, underground bar (assuming you can connect to the bar's Wi-Fi, that is.)
Carrier-branded Wi-Fi calling is a bit different, however. It's baked directly into the phone's dialer, so you don't need to fire up an app or connect to a service to use it.
https://www.cnet.com/news/what-you-need-to-know-about-wifi-calling/
- A duplex communication system requires a pair of channels/frequencies hence the term duplex meaning two parts. The two channels are defined as uplink/downlink or reverse/forward.
In a full-duplex system simultaneous transmission/reception is available,i.e., one can transmit and receive simultaneously.
In a half-duplex system, each party can communicate with the other but not simultaneously; the communication is one direction at a time. Half duplex systems utilize separate channels for uplink and downlink, i.e., a transmit and receive frequency. In a half duplex communications system one user is allowed to transmit on the uplink channel at a time.
https://en.wikipedia.org/wiki/Duplex_(telecommunications)
