Background

The 802.11g standard has a maximum link speed/signaling rate of 54 megabits per second (Mbps), which can result in maximum actual throughput of up to 22Mbps-24Mbps for data. Various wireless chipset vendors have created approaches to increasing this limit in their wireless devices. All of these methods require an AccessPoint and WiFi network adapters that support them. Some methods fall back to the 54Mbps link speed when even one device that does not support them is connected to the access point in question. Other methods, such as SpeedBooster, can tolerate non-speed-enhanced devices on the same access point.

SpeedBooster (aka 125 High Speed Mode)

SpeedBooster is the Linksys term for 125 High Speed Mode (125HSM), Broadcom's proprietary frame-bursting and advanced compression technology to improve 802.11g performance. When originally announced, Broadcom called it Afterburner, and other vendors have marketed it as g+ SuperSpeed, Gplus, HSM, 125Mbps 802.11g, and Turbo G. It's currently marketed as a proprietary extension of Broadcom's Xpress Technology, their standards-based enhancements to 802.11g that are supported by their 54g WiFi chipsets.

The throughput transmission speed limit when using 125HSM is up to 35%-40% higher (or more) than standard 802.11g. The "125" in "125 High Speed Mode" refers to performance at a theoretical signaling rate: a 125HSM device can achieve maximum actual throughput of up to 34.1Mbps, which is the equivalent throughput of a system strictly following all 802.11g protocols and operating at a signaling rate of 125Mbps.

Besides Linksys (part of Cisco Systems), other vendors that have licensed 125HSM technology from Broadcom include Belkin, Buffalo Technologies, Dell, Gateway, Hewlett-Packard, Motorola, and U.S. Robotics. In general, they are all interoperable in 125HSM mode.

One alternative: Super G

Most Atheros WiFi chipsets use Super G, a set of high speed wireless LAN technologies which use proprietary techniques: channel-bonding, packet bursting, fast frames, and compression. They have also adopted these technologies to 802.11a/g, marketing it as Super AG. Vendors that have licensed Super G technology from Atheros include D-Link, Netgear, Nortel Networks, SMC, Sony and Toshiba. In general, they are all interoperable in Super G mode.

The maximum link speed with Super G is 108Mbps, which is achieved through bonding two 54Mbps channels. This can result in maximum actual throughput of 40Mbps-60Mbps. However, these channel-bonding techniques are considered problematic from a standards standpoint because Super G channel-bonding can create interference on all channels, potentially causing interference with neighboring WiFi networks and other wireless devices in the band, such as cordless phones and BlueTooth devices. It also makes it difficult to put a high number of AccessPoints in a small area, because they are all basically operating on the same channel. However, channel bonding can yield higher wireless speeds.

125HSM does not use channel-bonding, so it is possible to use it in areas with a high concentration of AccessPoints. 125HSM devices allow a higher AccessPoint density, because each AccessPoint can be set up to use a different channel and can be slightly more successful in a radio-dense environment. Conversely, they often yield a lower speed when compared to a channel-bonding Super G alternative.

Competing performance claims

Atheros claims that Super G more than doubles throughput over standard 802.11g in a typical home and enterprise applications. Broadcom claims that in the real-world, 125HSM provides up to 17% better performance over Super G because other 2.4GHz devices interfere with channel-bonding at distances of up to 150 feet. However, Atheros also claims that in real-world scenarios with physical separation and walls, closely located networks will not experience any interference from a Super G network.

More alternatives: MIMO, ODFM and the road to 802.11n

Airgo Networks has released several WiFi chipsets with proprietary implementations of MIMO and OFDM technologies. MIMO (multiple-input multiple-out) allows multiple transmitter and receiver antennas for increased data throughput through spatial multiplexing and increased range. OFDM (orthogonal frequency-division multiplexing) allows a single transmitter to transmit on dozens to thousands of different orthogonal (independent) frequencies. These techniques should result in a signal with high resistance to interference.

This approach can provide benefits to non-MIMO devices, with greater coverage and better throughput at longer distances, although not beyond their maximum data rates for standard 802.11a/b/g devices. With proprietary Airgo MIMO devices, extensions to 802.11a/b/g allow for close to a doubling of throughput over standard 802.11a/b/g. The most recent 3rd generation chipsets are marketed under the name True MIMO. For "True MIMO" devices, the addition of proprietary ODFM technology allows up to 126Mbps throughput in one channel, or up to 240Mbps throughput using channel-bonding. This level of throughput is considered noteworthy because it can provide faster speeds than wired 100Mbps Ethernet.

Different implementations of this technology are marketed under various names besides MIMO and True MIMO: "Pre-N" by Belkin and Netgear, RangeMax by Netgear, and SRX/SRX200/SRX400 by Linksys. Because all of these products are based on propetary implementations, they may suffer from poor interoperability across vendors, and have no guarantee of full compatibility with future standards, although they may function as standard 802.11a/b/g devices with benefits from MIMO.

The desire for a standard for these wireless LAN technologies led to the new 802.11n task group, which is developing a new standard that could be up to 10x the speed and up to 20x the range of 802.11a/g. The draft 802.11n specification includes several improvements to 802.11g, including MIMO and OFDM. Some vendors are already starting to sell technologies that are compliant with the draft standard, such as Intensi-Fi chipsets from Broadcom and XSPAN chipsets from Atheros.

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This stuff should all be refactored into a separate WirelessSpeedEnhancement page, linking to SpeedBooster, Super G, and other methods such as MIMO and 802.11n.