The remote controls of devices such as televisions that we use at home communicate with infrared light. If we recall, the mobile phones we used in the 2000s could even transfer files using infrared communication instead of Bluetooth.

Examples of wireless devices include mobile phones, GPS devices, remote controls that we use to open parking barriers, and cards that we use as tickets on buses. If you noticed, some of these devices are only receivers, some are only transmitters, and some are both receivers and transmitters. Almost all of them use different communication protocols. We can also use some of these communication systems such as WiFi, Bluetooth, and NFC in our own projects. I will try to talk about their working principles and differences as much as I can.

WiFi

This abbreviation, which we can translate into Turkish as wireless local area network, consists of the first two letters of the words Wireless Fidelity. It operates at 2.4 GHz and 5 GHz frequencies. All devices that use IEEE 802.11 standards can be defined as WiFi devices. It can be used for internet connection, home or workplace network, and communication between two devices.

WiFi devices basically have 3 different operating modes: Infrastructure and Ad-Hoc (direct communication between two devices). Infrastructure mode has two different sub-modes: client and station (access point). As clients, we can give our computers, mobile phones and WiFi modules that we can use in our projects as examples. Station devices are modems and routers. Most devices can be used by switching between client and station modes. For example, when we turn on the wireless access point on our smartphone, our phone’s WiFi module exits client mode and enters station mode and broadcasts the mobile internet using its own WiFi module.

In an Ad-Hoc connection, two devices can only communicate with each other. In this case, both devices act as both a client and a station.

The most widely used IEEE 802.11 standards today are 802.11b/g/n and ac standards.

The 802.11b and 802.11g standards use the 2.4 GHz frequency. The maximum communication speeds they can reach are 11 Mbps for the 802.11b standard and 54 Mbps for the 802.11g standard.

The 802.11n standard uses the 2.4 GHz and 5 GHz frequencies. The maximum speed that can be reached using this standard is 150 Mbps.

The 802.11ac standard uses the 5 GHz frequency. The maximum speed that can be reached using this standard is 780 Mbps.

Bluetooth

It is a technology developed for data transfer over short distances. It was first developed by Ericsson in 1994 to be a wireless alternative to RS-232 connection. It operates at the 2.4 GHz frequency. It is used in applications such as file transfer, voice transfer and virtual COM port. The communication protocol is constantly developing and updated. Current devices support new protocols and are also backward compatible.

The speeds in Bluetooth communication are as follows:

Bluetooth v1.2: 1 Mbps
Bluetooth v2.0+EDR: 3 Mbps
Bluetooth v3.0+HS: 24 Mbps
Bluetooth v4.0: 24 Mbps

Today, devices that are aimed to consume less power, such as smart watches, use the protocol called Bluetooth Low Energy. This protocol is only compatible with devices that support Bluetooth v4.0 and BLE, and is not backward compatible.

NFC and RFID

NFC is often confused with RFID. RFID is the name given to the technology used to recognize objects using radio waves. There are active and passive tags. Active tags have their own power source and thus provide the opportunity to communicate from longer distances. Passive tags operate by being fed by the magnetic field created during reading. The best examples of active and passive tags are the OGS and HGS systems used at bridge and highway toll booths. While the OGS device is a large device containing a battery, the HGS is in the form of a card or tag. There are RFID tags that work in three different frequency bands:

Low Frequency (LF) 125 -134 kHz
High Frequency (HF)13.56 MHz
Ultra High Frequency (UHF) 856 MHz to 960 MHz

NFC is a wireless communication technology that works by touching or bringing devices closer to each other at short distances such as 10 cm. NFC is an application of RFID technology. It works in the HF band (13.56 MHz).

NFC devices can work in three different modes: NFC card emulation mode, printer/reader mode and peer-to-peer mode. In card emulation mode, devices such as smartphones can act as cards and be used in ways such as making payments in shopping. In writer/reader mode, an NFC device can be used to read and write to an NFC card or tag. In peer-to-peer mode, protocols such as file transfers between two NFC devices are initiated using NFC.

NFC cards have a small amount of memory. This memory can only be read or rewritten