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Cisco's 802.11n Wi-Fi boosts older laptops
But Ruckus says it's been done before.
By Peter Judge, Techworld | Techworld
Published: 16:52 GMT, 13 January 09
Cisco's new Aironet 1140 Wi-Fi access point has added the ability to send directional signals so existing Wi-Fi clients can share in the speed improvements provided by 802.11n.
Although Cisco was the first enterprise Wi-Fi vendor with 802.11n technology, its 1250 access point, launched in 2007, is bigger and heavier than the subsequent competition from the likes of rivals Aruba and Trapeze. It also required users to update their networks with Cisco's proprietary power over Ethernet, to power its two radios at full 802.11n speeds.
The 1140 can drive two spatial streams of data on both the radio bands where Wi-Fi is allowed, using 802.11n's MIMO technology, giving speeds of around 130Mbit/s for 802.11n clients, such as newer Centrino laptops.
Older 802.11g clients can't do MIMO, however, so Cisco's "ClientLink" technology uses the access point's smarter antennas to produce directional beams for these devices. This focusses the transmit power, so those clients see a bigger signal strength, and gives faster speeds for older devices, as well as eliminating dead spots in coverage. It can also switch clients from one access point to another to balance the load on the network.
"Customers want to extend the life of existing clients," said Chris Kozup, a senior manager in Cisco's mobility group. "Our competitors talk about making sure that legacy clients don't impact the performance of 802.11n clients, but Cisco has a large number of established customers with applications that are run on legacy client devices. The idea of optimising the performance of 802.11n at the expense of 802.11g is not palatable to them."
Cisco has released a report from test company Meircom, which claims that 802.11g devices get up to 65 percent more throughput, and the overall capacity of channels used for 802.11g can go up by 27 percent.
"I expect we'll see a lot more beamforming in the future, as the WLAN chip guys build it in," said Craig Mathias, of Farpoint Group. "The whole scheduling space is ripe for innovation and we'll also see more on that going forward."
Already, Ruckus Networks is doing beam-forming: "Not all beamforming is created equal," said Jim Calderbank, director of enterprise sales EMEA at Ruckus Wireless. "Cisco's new technology still won't solve the problem with Wi-Fi performance today because it was built on a standard chipset, meaning it has no real-time adaptive capabilities and cannot optimise the form or direction of Wi-Fi signals."
"We increasingly rely on Wi-Fi for a multitude of bandwidth intensive applications - from multimedia content to making VoIP calls - and it's therefore crucial for networks to be able to deal with the ever-changing environment and constant interference. With this alone, it's surprising to see an industry leader like Cisco follow the path of least resistance."
Powering the AP from standard 802.3af power over Ethernet is not a big surprise given other vendors' moves in that direction, but Cisco is proud of the fact that it has sold 175,000 of the older units - presumably to people who could have avoided the proprietary PoE upgrade if they'd waited. "A lot of those customers were in more ruggedised environments," said Kozup. "Some already had switches that supported enhanced power, and others used injectors."
Either way, they can use standard PoE in future, said Mathias - who pointed out that future wireless networks might use more than three or more radios and need more than 802.3af power, anyway.
Cisco, as is its wont, announced a new overall marketing term for its wireless management features. "M-Drive" includes the new ClientLink technology alongside other features.
Cisco would not confirm what silicon its access point is using, but the company is understood to have used Marvell Wi-Fi chips, while most vendors use silicon from Atheros. "We will build on our existing relationships," said Kozup.
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Cisco compares ClientLink to Other Beamforming Sol | Published: 22:44 GMT, 14 January 2009
ClientLink has many advantages over switched antenna arrays used by others: - Enhances performance in both directions: ClientLink enhances performance in both uplink and downlink directions, whereas a switched antenna array only helps in the downlink direction when used with multiple simultaneous clients. - Faster Dynamic Response: ClientLink adjusts antenna weights on a per-packet basis, and can easily track moving clients, whereas a switched antenna array uses a slow feedback loop and can't keep up with moving clients. - Better performance in indoor multipath environments: ClientLink digitally can vary its antenna pattern across signal frequency, whereas a switched antenna array must use the same pattern at all frequencies, yielding degraded performance in indoor environments. - Lower parts cost: ClientLink uses existing antennas with no need for an expensive array. - Less signal loss: Antenna array solutions require switches that result in signal loss.
Cisco clarifies on beam forming benefits | Published: 22:37 GMT, 14 January 2009
Cisco wanted to clarify some of the statements made about ClientLink and beamforming. 1) ClientLink technology is based on custom chipset level enhancements, that are not available in standard chipsets, 2) ClientLink does indeed optimize the form and direction of the Wi-Fi signal by adjusting beam-forming parameters, and 3) ClientLink performs real-time adaptation of the beam on a per-packet and per-client basis.