- À propos de nous
- Services
- Secteurs
- Succès
- Évenements
- Blog Fr
The continued quest for wireless connectivity in a multitude of devices has now been joined by an insatiable appetite for speed. Today’s fastest wireless LAN (WLAN) standard, 802.11n, delivers theoretical raw data speeds in excess of 500Mbps — but that’s not enough. To help satisfy the hunger for ever-faster WLANs, the IEEE is now adding to its alphabet soup of Wi-Fi technology standards. The latest concoction is 802.11ac, a new technology developed to provide Gigabit speeds.
The IEEE is expected to release a draft of the 802.11ac standard sometime in 2011, with the first 802.11ac-enabled devices to reach the market sometime in 2012. Research firm In-Stat forecasts rapid uptake of the new standard, with shipments of 802.11ac-enabled devices going from zero in 2011 to nearly 1 billion by 2015. “The goal of 802.11ac is to provide data speeds much faster than 802.11n, with speeds of around 1Gbps,” says Frank Dickson, vice president of research, In-Stat. “The timing for 802.11ac approval is to have a draft standard created by 2011 and have the first 802.11ac products out by the end of 2012. The technology behind 802.11ac has not been finalized. However, it will likely involve bonding four or even eight channels together and some tweaks to the modulation scheme.”
The 802.11n standard, finalized in March 2009, gave a real boost to WLAN performance. While older 802.11g technology provides real WLAN throughput in the 20Mbps to 25Mbps range, 802.11n delivers at least 100Mbps by improving the efficiency of media access control. It also uses more of the wireless spectrum, when available, to enhance performance; while 802.11g uses 22MHz-wide channels, 802.11n supports up to 40MHz-wide channels. It is also designed to resist interference from neighboring Wi-Fi systems and 2.4GHz devices.
But the heart of 802.11n is a technology called MIMO — short for multiple input, multiple output — that employs multiple antennas and radios to transmit and receive data. Although multiple paths typically degrade radio signals, MIMO uses a technique called spatial multiplexing for simultaneous transmission. This not only increases bandwidth but provides greater coverage, enabling very high-speed connections over distances of 150 feet or more.
As a result, a state-of-the-art 802.11n WLAN can achieve speeds of 300Mbps using two spatial streams, and future developments will brings speeds of up to 600Mbps using three or four spatial streams. The 802.11 working group is taking a similar path to reach the goal of 1Gbps throughput with 802.11ac.
The proposed 802.11ac standard features well-known technologies, including MIMO, along with an increase in the radio channel. Just as 802.11n increased throughput by doubling channel width from 20MHz to 40MHz, 802.11ac provides even greater speeds thanks to wide 80MHz channels. In addition, advances in processing power have made it possible to use more sensitive coding techniques that depend upon finer distinctions in the received signal.
Increasing efficiency — that is, maximizing the number of megabits transmitted per megahertz of spectrum — is another way to increase data throughput. A new technology called multi-user MIMO (MU-MIMO) improves upon the capabilities of the 802.11n technology by enabling the simultaneous transmission of different data frames to different end-users through spatial awareness of clients and sophisticated queuing systems.
With any WLAN technology, the real throughput (100Mbps for 802.11n) is generally a fraction of the theoretical throughput (500Mbps for 802.11n). Thus, the 1Gbps data rates of 802.11ac may exist only in ideal conditions. Furthermore, few Internet connections or internal LANs operate on that kind of bandwidth, so an upgrade to 802.11ac may not result in any real performance gains. Nonetheless, those who savor the idea of having the fastest WLAN possible are expected to rapidly boost the nascent market for 802.11ac devices.
