125 High Speed Mode
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125 High Speed Mode (125HSM) is Broadcom's proprietary frame-bursting and compression technology to improve 802.11g wireless LAN performance. The throughput transmission speed limit when using 125HSM is claimed to be up to 35%-40% higher than standard 802.11g.
The "125" in "125 High Speed Mode" refers to performance at a theoretical signaling rate of 125 Mbit/s: a 125HSM device can achieve a maximum throughput of 34.1 Mbit/s, which is the equivalent throughput of a system strictly following all 802.11g protocols and operating at a signaling rate of 125 Mbit/s.
When 125HSM was originally announced in 2004, it was called Afterburner. It is currently marketed as a proprietary extension of Broadcom's Xpress technology, their standards-based frame-bursting approach that is supported by their 54g Wi-Fi chipsets.
Other vendors have marketed 125HSM products under a variety of names:
- g+ SuperSpeed (ZyXEL) (This one uses the G++ Technology solution from Texas Instruments, which uses 125 Mbit/s as well but may or may not be compatible to Broadcom's solution)
- G Plus or HSM (Belkin)
- 125* High Speed or Turbo G (Buffalo)
- SpeedBooster (Linksys)
- 125M or 125 High Speed or 125* High Speed (Asus)
- 125 Mbit/s 802.11g
Manufacturers that have licensed 125HSM technology from Broadcom include Belkin, Buffalo Technology, Dell, Gateway, Hewlett-Packard, Asus, Linksys (now part of Belkin), Motorola, U.S. Robotics and Netcomm. In general[who?], 125HSM products from different vendors are all interoperable in 125HSM mode.
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- These (and similar) proprietary extensions are incompatible across different wi-fi chips vendors. So to make wi-fi links work in 125 HSM mode, both sides should use chips from same vendor (e.g. Broadcom). In most real-world scenarios such modes are simply useless due to different chips used by different devices.
- Existence of several similar technologies with different branding and incompatible with each other causes massive consumer confusion.
- These technologies are marketed in such a way it is possible to see them as cheating and tricking consumers through technology branding. This type of network will never be able to reach 125 Mbit/s as real data throughput; 125 Mbit/s is the maximum data rate before accounting for overhead. This causes consumer frustration due to failed expectations. For instance, the average consumer would expect a 125 Mbit/s wireless link to outperform a standard 100 Mbit/s wired link while, in fact, 100 Mbit/s wired link will be much faster; a standard wired 100Mbit/s 100BaseT link is approximately three times faster than 125HSM in simplex mode (i.e. transmitting or receiving only) and six times faster than 125HSM in full-duplex mode (i.e. both transmitting and receiving data—which is typical during file transfers between 2 computer connected to the same hub). In other words, even under ideal conditions, 125 HSM mode may only deliver anywhere from a third to one sixth the data transfer speed of a standard 100 Mbit/s wired LAN link.
125HSM is one of several competing incompatible proprietary extension approaches that were developed to increase performance of 802.11g wireless devices, such as Super G (or "108 Mbit/s" technology) from Atheros, MIMO-based extensions from Airgo Networks, and Nitro from Conexant
125HSM can be more successful[by whom?] in radio-dense environments than non-standard channel bonding approaches to enhance 802.11g performance. Broadcom claims that in the real-world, 125HSM provides up to 17% better performance over channel bonding approaches such as Super G because other ISM band devices—such as neighboring wireless networks, cordless telephones, baby monitors, and Bluetooth devices—can interfere with channel bonding at distances of up to 150 feet (46 m).
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- Press release announcing 125HSM as Afterburner
- 125 High Speed Mode page within the 54g Wi-Fi technology site
- KeyLabs benchmark comparison of 125 Mbit/s products by US Robotics, Linksys, Netgear, Belkin, and DLink. Also comparisons to some "Draft 802.11n" competitors.
- Article at SmallNetBuilder (formerly Tom's Hardware Guide) testing 125HSM performance
- Short article on various 802.11g boosters