Interference, Data Deluge Key 802.11n Concerns

Carl Weinschenk

We recently posted an item suggesting that companies be careful when considering moving to 802.11n, since the draft standard isn't likely to be signed off on for a year or more. (One note about that posting: A representative of Aruba Networks says the ZDNet piece that was mentioned mischaracterized the company's position.) provides further evidence and good insight into why such care should be taken. There are at least a couple of interrelated issues, both of which relate to the greater power generated by 802.11n. The increased range changes the equation when mapping out where to put access points. The story says no updated tools are available to perform pre-deployment site surveys and to monitor their management access points. We take such unconditional statements with a grain of salt, but certainly assume that, at best, few are available.


The other issue involves the ability of deployed 802.11 controllers -- the devices that control the flow of data to and from APs -- to handle the increased traffic. The story suggests that the greater throughput generated by the new spec can overwhelm controllers. APs end up handling the excess. This is problematic, since their security may not be adequate. The flavor of the piece is that carefully engineered workarounds are possible. The challenges will grow more extreme, however, as beam forming and multiple in, multiple out (MIMO) antennas are integrated into 802.11n systems.


The challenges of deploying 802.11n are generating a lot of discussion among technical folks. This paper at CWNP, a wireless training, certification and services organization, offers four choices: Deploy a network in parallel to existing 2.4 and 5 GHz networks; use only a second 5 GHz channel; rip out the existing 802.11a and g networks and; finally, deploy upgraded APs.


One potential answer to at least some of the challenges involves deployment of the 802.11n gear in a mesh configuration. The possibility is explored at Network World. Since meshes don't rely on central control points, the issue of overloading controllers could be reduced or alleviated. It also is possible that the bandwidth savings could enable the deployment of fewer APs, making it easier to change over when the full standard is promulgated. The writer provides details on the attitudes of Ruckus, Colubris, Aruba, Cisco, Firetide, Meru, Motorola and Trapeze networks on 802.11n mesh AP plans.


Indeed, Aruba made 802.11n news -- though not on the mesh front -- this week. The Multi-Service Mobility Controllers and 802.11n Access Points, the company says, provide converged services, including cellular-to-wireless integration and secure remote access. The release goes into great detail on the new products, but doesn't directly address the interference issues. The release does say the new controllers can be retrofit onto existing Aruba gear, which suggests that the vendor has addressed the issue.

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