As the cellular generations evolve, so do other wireless technologies. Wi-Fi and Ultra-Wideband (UWB) are well known wireless technologies that are also continuously changing along with the cellular standards as semiconductor and antenna technologies advance.
The most widely used wireless technology Wi-Fi, also known as the IEEE’s 802.11 wireless local-area network (LAN) standard, has changed significantly. When the initial standard 802.11 was introduced in 1997, the maximum data rate was 2 Mbits/s. In 1999, the 802.11b standard emerged to provide up to 11 Mbits/s and launch the first successful WLAN wave.
Since then, the modulation/access has changed from direct sequence spread spectrum (DSSS) to orthogonal frequency-division multiplexing (OFDM). Subsequent versions of the standard have used various configurations of OFDM. 802.11a was the first to use it in the 5-GHz band, boosting rates to 54 Gbits/s. 802.11g came next with 54 Gbits/s in the 2.4-GHz band. The most recent version is 802.11n, which boosted rates to over 150 Mbits/s using up to four multiple-input multiple-output (MIMO) streams and wider bandwidth (40 MHz) channels in both the 2.4- and 5-GHz bands.
Already, the next generation of standards is being finalized—802.11ac and 802.11ad. The next logical extension of the standard beyond the popular 802.11n is 802.11ac. It is expected to use the 5-GHz band to achieve data rates to 1 Gbit/s using the same basic media access control (MAC) and physical layer (PHY) configurations but with some modifications to achieve the higher data rates.
802.11ac does this by using wider-bandwidth channels of 80 or 160 MHz, whereas the maximum for 802.11n is 40 MHz. This standard also supports up to eight spatial streams of MIMO, whereas 802.11n has a maximum of four. Multi-user MIMO or MU-MIMO is introduced to further boost speeds. The modulation is 256-phase quadrature amplitude modulation (256QAM) instead of the 64-phase quadrature amplitude modulation (64QAM) used by 802.11n.
Using single antennas and 80-MHz bandwidth, a user could expect a theoretical peak of 433 Mbits/s with 256QAM. That jumps to 867 Mbits/s with a 2x2 MIMO in an 80-MHz channel. Using a 160-MHz channel and single antennas, a maximum rate of 867 Mbits/s could be achieved. With 2x2 MIMO in 160 MHz, the theoretical rate jumps to 1.73 Gbits/s. Even higher speeds are expected with higher MIMO configurations using the MU-MIMO arrangements.
The 802.11ad standard is another high-speed variation using the 60-GHz millimeter-wave band. Data rates up to 7 Gbits/s can be expected. Neither the 802.11ac nor the 802.11ad standard has been finalized as work continues toward a potential ratification in 2012.
Considerable effort was put into developing a UWB wireless standard. While the IEEE standards group 802.15.3a failed to agree on one approach to UWB, several companies developed the OFDM version and have sold chipsets over the past several years.
Only a few viable UWB chip companies still exist, such as Alereon and Wisair. Both produce chips that are used primarily for transmitting compressed video to video monitors, HDTV sets, and other video products. More recently it is being used to connect laptops to larger video monitors and docking stations.
UWB uses the 3.1- to 10.6-GHz band and can achieve data rates from 53.3 Gbits/s to as much as 480 Gbits/s at a range of up to 10 meters. The WiMedia Alliance, which defined the standard for UWB, provided for higher data rates in its most recent version 1.5. It supports data rates to 1.024 Gbits/s with simple modifications to the modulation and coding. Eric Boockman, CEO of leading UWB chip supplier Alereon, sees an increasing adoption of the technology where it simplifies video transmissions over short distances.
Some other lesser-known wireless efforts do exist, with their futures unknown. Streaming video wirelessly is the focus. For example, WiDi is a software option from Intel that uses Wi-Fi (802.11n) to stream video to HDTV sets that have an appropriate compatible accessory receiver.
ECMA-387 is the European 60-GHz wireless LAN standard. It offers a single-carrier mode with speeds to 6.35 Gbits/s and an OFDM mode that can generate speeds to 4.032 Gbits/s. Its unique MAC conforms to the Open Systems Interconnection (OSI) standards.
And, the Wireless Home Digital Interface (WHDI) is a unique standard for streaming video from computers to HDTV sets. It uses 40-MHz wide channels in the 5-GHz unlicensed band. It also uses OFDM in a version of 802.11a with a unique compression scheme and 5x4 MIMO to achieve a reliable 3-Gbit/s data rate.