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What is Enterprise Ready WLAN?

September 10, 2007 - 1 Comment

Has anyone noticed the large number of “enterprise class” wireless devices being delivered to the market that only support the 2.4Ghz spectrum?Whether these devices support 802.11b or 802.11g, the fact remains that there is simply not enough spectrum available in 2.4Ghz space to ensure a quality service. As many of you probably already know, the 2.4Ghz space only supports three non-overlap channels, and no matter how creative your channel plan is, any deployment that exceeds three APs will see some co-channel interference – including from devices that may not be under your control (is your neighbor running a network?). Backgrounder: co-channel interference means that two neighboring APs share the same channel. When this occurs, if any device in either cell transmits, it is likely to create interference in the other cell. Adjacent channel interference means that neighboring access points are on channels that follow each other. In these cases, physical distance and radio quality can cause some bleed over across the channels and create interference. So in a reason that in an ideal network, you want to ensure that neighboring APs do not share the same channel, and the channel spacing eliminates adjacent interference.Going back to the 2.4Ghz spectrum, with a total of three channels, you can now see that eliminating co-channel interference is a challenge, while eliminating adjacent interference is simply not possible.It is for this reason that enterprises need to start considering moving to the 5Ghz spectrum. The number of channels in 5Ghz ensures that sufficient spacing can be established between the APs to eliminate both co-channel and adjacent channel interference. What I would recommend is that in your purchasing decisions you make sure that the devices support 5Ghz. I’ve heard many arguments from device manufacturers that 5Ghz WiFi is simply too power hungry. I would point those manufacturers to Cisco’s 7921 WiFi phone, which has an impressive stand-by and talk-time battery life. We’ve reached a point where technology is simply no longer a reason for ignoring enterprise spectrum demands.Many customers have asked whether they should dedicate their 5Ghz spectrum for voice, and push all data to 2.4Ghz. Given the sensitvity of voice service, and the fact that poor performance is much more noticeable to the user, it is a reasonable approach. For customers that deploy dedicated voice devices, such as the 7921 mentioned above, enforcement may be possible. However, for most customers I believe this is an interim step since multi-mode devices are now becoming widely available. These devices provide both Unified Communications and data services, making it very difficult to dedicate a single spectrum for voice – and causing both data and voice on the 5Ghz band.So if I have both data and voice services on my 5Ghz band, how will I ensure the voice quality meets my user’s expectations? As we are seeing through the WiFi certification process, more voice devices are now being certified to be WMM compliant. The WMM certification process provides quality of service (QoS) enhancements to ensure that voice traffic is properly prioritized. I believe that over time WMM will also become an “Enterprise Ready” requirement.

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  1. In response to moving certain medical devices over to 5 GHz and the effect this would have on voice? Our advice is to have all your voice clients in a SSID that uses the highest level of QoS (Platinum). Then have data in a SSID that uses best effort level of QoS (Silver). Because 5GHz has many more channels than 2.4GHz there is more bandwidth. Also, the channels in 5GHz do not use the 1 and 2 Mbps data rates that really slow down the 2.4GHz channels. The applications will be faster on 5GHz and if QoS is done correctly, should not have a noticeable impact on the voice quality.