We use the term Wi-Fi, but do we really know what it means. When looking at phone specifications, the Wi-Fi capabilities appear under WLAN (Wireless LAN), and LAN stands for Local Area Network. Don’t you love acronyms that contain acronyms. Wireless tells us that we are using radio frequencies as the communications media. LAN tells that we are connecting multiple devices into a single network. To avoid chaos on the network, some device must manage communications between devices, and that is the job of the WAP (Wireless Access Point). Other Wi-Fi enabled devices (laptops, phones, printers, scanners, Web cams, and TVs) are clients that connect to the WAP. They can communicate with each other because they are a part of the same LAN. Without getting into the world of protocol mania (more acronyms), the standard protocol for addressing devices is TCP/IP (Transmission Control Protocol / Internet Protocol), which uses a unique IP addresses to identify device. The WAP may be part of a router, which in turn, allows the LAN to connect to another network, usually to an ISP (Internet Service Provider) for small networks.

Wi-Fi is also an acronym for Wireless Fidelity, although we now use Wi-Fi as if were a noun. Wi-Fi, itself, refers to the IEEE 802.11 standard. IEEE is the Institute of Electrical and Electronic Engineers, and they number their standards. The goal of standards is to provide interoperability between devices. Unfortunately, manufactures interpreted the standard differently. In 1999, a group of industry leaders formed the Wi-Fi Alliance to certify products that complied to the IEEE 802.11 standard. The standard contains a number of subsections that are identified by appending lower cases letters to the standard.

IEEE 802.11 b/g/n, the letters refer to different communication protocols used to communicate between devices. These protocols determine the data transfer rate. IEEE 802.11b is the oldest and slowest standard. Since Wi-Fi uses radio frequencies as the medium of communication, we are back to regulation of a limited resource. In the USA, the FCC (Federal Communication Commission) authorized only 11 channels. SUTEL (Superintendencia de Telecomunicaciones) in Costa Rica, like most countries, authorized 13 channels. Japan authorized the use of a 14th channel. The problem is that the channels overlap each other. As a result, you often see channels 1, 6, and 11 as the options for Wi-Fi equipment made for the USA. The rest of the world used channels 1,5,9,13 as the non-interfering channels. The IEEE 802.11g standard increases the speed by changing the protocol used for communications, but the channels stayed the same. IEEE 802.11n is the fastest protocol, critical for HD (High Definition) video streaming, and uses channel 3 and 11 as the non-interfering channels, as it uses a much wider bandwidth than the b or g. While a single WAP only uses one channel, it is the neighboring WAPs that can create a problem. For example, if you use channel 11 for 802.11n, and another Wi-Fi in radio range uses channel 9 for 802.11g, there is going to be interference, and both signals will degrade, resulting in slower data rates. For this reason Wi-Fi uses very low power to limit the range and the chance of interference. It is no different than if you are listening to a radio, and you get interference from another station on a nearby frequency. I know this sounds complicated, but it is the reality of Wi-Fi. If you have an Android device, the WiFi Analyzer App displays a great graphical view of Wi-Fi signals, that clearly illustrate the above.

The good news is that most countries, including Costa Rica, allocated another band, just for 802.11n. The Wi-Fi routers that implement the additional band are referred to as dual-band routers. When the router has interference on one band, it automatically switches to the other band. The catch is that a dual-band WAP can only play this game with devices that support dual bands. Devices negotiate with each other to find the fastest protocol that they can use for communication. This allows a device with an older protocol, such as IEEE 802.11b, to communicate with a WAP that supports IEEE 802,11 b/g/n. Now for some interesting new approaches to Wi-Fi communications.

In the article on tethering, I mention that Wi-Fi tethering uses the ad-hoc mode. The ad-hoc mode still uses Wi-Fi frequencies, and the phone does act as an access point to the Internet. However, there is no local network. The ad-hoc mode acts like a wireless cable between two devices. To create a network without a WAP, the Wi-Fi Alliance created a new protocol call Wi-Fi Direct. In addition to one-to-one connections, you can connect a group of devices. With Wi-Fi Direct, the phone becomes another member of the group (see this demo). To joint the group, you need to know its password. There still is no local network. Devices do not require an IP address to communicate. This only works for devices certified as supporting Wi-Fi Direct.

Digital Living Network Alliance (DLNA) is not yet another standard. Rather, it is a set of guidelines that enable sharing of digital media between consumer devices. The guidelines are based on existing standards. Consumer devices that are certified by the Digital Living Network Alliance get to display the DLNA logo. The best way to experience the benefits of DLNA is to visit the Digital Living Network Alliance Web site. After you go through the demos, you will have to admit that it is really cool.