With each new generation of Wi-Fi standards, network managers can offer users faster wireless throughput. But the promise of high-speed wireless is often derailed by the persistence of legacy wireless clients that some enterprises refuse to retire.
IEEE 802.11n and 802.11ac operate in the 5 GHz spectrum where packets move faster and wireless interference is uncommon. But legacy wireless standards that use only the 2.4 GHz spectrum -- such as 802.11b and 802.11g -- are a drag on the performance of these newer standards. The legacy networks exchange packets more slowly, and the 2.4 GHz spectrum is vulnerable to interference by everything from Bluetooth devices to microwave ovens. It's time for enterprises to do everything they can to retire legacy standards, or at least get them out of the way of 802.11n.
Most if not all wireless LAN vendors design their access points to be backward-compatible with those legacy Wi-Fi standards. When network managers turn on these legacy standards to support older client devices, faster 802.11n clients have to share airtime with them. Users with faster devices often experience poor wireless performance due to interference or the slower data rates of devices accessing the same APs. The 5 GHz spectrum offers wider, nonoverlapping channels. IT organizations should design their WLANs by advertising the 5 GHz band before the 2.4 GHz band for devices coming onto the enterprise network -- a method called band steering.
Wireless band steering prevents backward compatibility from slowing Wi-Fi speeds
Cisco proposed that manufacturers of wireless network equipment should end support for slower Wi-Fi standards and data rates, such as 802.11b, which operates at 11 Mbps in the 2.4 GHz band. Legacy 802.11b client devices chew up airtime. Clients that take advantage of 802.11n's 600 Mbps throughput often get stuck behind these older clients, leading to performance issues, the company said.
Cisco acknowledges that network managers can't simply turn off or stop supporting legacy Wi-Fi standards because older devices still need to connect to the wireless network. But advertising the 5 GHz spectrum first using band steering can give faster devices a chance to jump ahead of legacy devices, said Chris Spain, vice president of marketing for Cisco. "When you advertise your wireless network, you usually advertise it at the lowest data rate you are going to support, just in case there are slower devices out there," he said. "But if enterprises disable slower standards, they can free up more capacity.
"Enterprises must ask themselves, 'Is it time to replace some of these assets and disable these slower data rates so we can speed the network up?'"
Some industries have to support legacy wireless
While it's common for some businesses to disable the lowest data rates -- such as 1 Mbps and 2 Mbps -- it won't be a solution for every business, said Matthew Norwood, solutions engineer for Bedroc, a Franklin, Tenn.-based systems integrator. Certain industries, such as healthcare and retail, typically have older devices on their networks they need to support. These businesses can't afford to upgrade all devices -- which can include medical equipment carts or scanners -- every time the WLAN is refreshed.
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"There are plenty of cases in which older clients -- even four- and five-year-old laptops that operate in the 2.4 GHz band only -- on the network are just not going to be replaced," Norwood said. "You can't tell [enterprises] to get rid of any .11b devices -- companies don't work that way."
Cisco's focus is on getting as many devices off of the 2.4 GHz band -- often dubbed the junk band -- as possible, Spain said. Many newer clients are both 2.4 GHz- and 5 GHz-capable, and many IT professionals will be able to adjust their access points to advertise the 5 GHz band first. "IT should plan their Wi-Fi deployments by optimizing the network for the 5 GHz band, and then overlay the 2.4 GHz band," Cisco's Spain said.
Methods for accommodating legacy Wi-Fi standards without affecting performance
Some network managers will be able to accommodate older standards without affecting faster wireless speeds and standards by supporting legacy standards in only certain locations within their offices or facilities, Norwood said.
"If a business knows they have older, lower data rate devices contained within a part of the building, they can adjust what the access points in that area support, which can be different [from] what the other access points in other areas support," he said.
Deploying dual-radio access points are another option. Some 802.11ac-enabled WLAN access points on the market today dedicate one radio for 802.11ac support in the 5 GHz spectrum and one radio operating in the 2.4 GHz band. "Because each radio is operating in a different spectrum, the capacity of one radio will not affect the capacity or scalability of the other, so there is no interference," IDC's Mehra said.
"Any .11ac [access points] shipping have to support .11n to ensure interoperability; we are going to have legacy devices for a long time," he said.