Originally, equipment based on the IEEE 802.11 wireless-local-area-networking (WLAN) standards (first IEEE 802.11a and b and 802.11g in 2003) was used as a means of delivering simple web browsing and e-mail connectivity “on the road”—in airports, hotels, Internet cafes, and shopping malls. Since then, such equipment has moved firmly into the home and home-office environment. Multiple devices now operate in connection to each other: computers, smartphones, tablets, printers, game consoles, media servers, scanners, and more. In addition, we want access to all of our stored material—data, pictures, whatever—from devices as small as a smartphone or as large as the screen in an auditorium—and to be able to share it with friends and colleagues instantly. We also want speeds that match a wired gigabit LAN connection, without the cables. The IEEE 802.11x standards are steadily evolving to meet all of these desires and demands (Fig. 1).
1. This graphic provides an overview of the IEEE 802.11x standards family.
IEEE 802.11n was introduced in 2009, improving the maximum single-channel data rate from the 54 Mb/s of IEEE 802.11g to more than 100 Mb/s. It also introduced multiple-input multiple-output (MIMO), or “spatial streaming,” communications. As many as four separate physical transmit and receive antennas carry independent data, which is aggregated in the modulation/demodulation process. Projections call for even higher data throughput requirements in future home and office applications. To cater to these, two new IEEE project groups have been formed with the goal of providing “very high throughput” (VHT).
Working Group TGac hopes to specify IEEE 802.11ac as an extension of 802.11n, providing a single-link minimum of 500-Mb/s and 1-Gbit/s overall in the 5-GHz band. Meanwhile, Working Group TGad and the Wireless Gigabit Alliance (WiGig) jointly proposed IEEE 802.11ad, which is targeting short-range speeds to 7 Gb/s in approximately 2 GHz of spectrum at 60 GHz. It was officially accepted as a standard at the end of 2012.
With the huge number of existing client devices, backward compatibility with current standards using the same frequency range is vital. The goal is for all IEEE 802.11 standards to be backward compatible and for 802.11ac and 802.11ad to be compatible at the medium-access-control (MAC) or data-link layer. They should differ only in physical-layer (PHY) characteristics. Devices could then have three radios: 2.4 GHz for general use (which may suffer from interference), 5 GHz for more robust and higher-speed applications, and 60 GHz for ultra-high-speed operation within a room—as well as support session switching amongst them.