QUESTION & ANSWER

The 802.11n wireless standard is ready. Are you?

By Andrew R. Hickey, News Editor 25 Oct 2007 | SearchNetworking.com

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With the 802.11n standard still in draft form until 2008, why should an enterprise consider deployment now? What are the downsides, if any, to such an early deployment?
Rachna Ahlawat: WLAN products based on 802.11n draft 2.0 are already being certified by the Wi-Fi Alliance, which means they are effectively ready for use today. The draft standard specifies all core features of the standard, including increased performance using multiple input, multiple output (MIMO) technology.

The Wi-Fi Alliance's approach here is similar to when it launched Wi-Fi Protected Access (WPA) prior to the approval of 802.11i for security. Eventually, the Wi-Fi Alliance synchronized its own certification with 802.11i through the release of WPA2, but provided WPA as an interim technology for use in advance of the final standard.

Given the speed, capacity and other benefits of 802.11n, many organizations are deciding to deploy 802.11n now, rather than wait until the full ratification of the standard. For example, Morrisville State College, a SUNY school, is the first organization to deploy enterprise-class 802.11n WLAN products. Morrisville installed its first WLAN in 1999 and determined that an upgrade was necessary this year. The effective life of a WLAN is three to five years, so it was time for the school to make a change ….

What should enterprise users do now to prepare for the final release of the standard? What should companies take into consideration when deploying 802.11n?
Ahlawat: While some optional features may be added to the final 802.11n standard, one thing that will not change is the planning required. It makes sense for enterprises to think about planning now, as they need to consider AP placement for the latest and emerging wireless technologies, rather than for legacy technologies.

On average, enterprises spend 15% to 20% of their entire WLAN budget on planning and AP placement activities. This is important to keep in mind because – with the new standard's use of MIMO technology – planning can be much more challenging than with previous Wi-Fi standards. While MIMO helps extend the wireless range, it also creates islands of wireless connectivity, making it challenging for the networking manager to design the network.

But planning doesn't have to be difficult or time-consuming. Each vendor is recommending different approaches to planning and placement. Vendors with a fourth-generation architecture have been identified by Gartner as offering the easiest deployment and simplest site planning because they are more immune to interference issues and can operate with fewer, non-overlapping channels. Meru's fourth-generation architecture uses a single channel with the capability to layer additional channels for greater network capacity, eliminating the need for complex site surveys when planning a network. Access points can be deployed after an eyeball site survey, and more can be added if coverage holes develop, without the need for channel planning.

What are the benefits of 802.11n over previous generations of the Wi-Fi standard?
Ahlawat: 802.11n provides a real alternative to traditional wired switching, with speeds up to 300 Mbps per client. With 802.11n, enterprises can replace edge wired networks without noticeable performance penalties in most environments. Its wire-like performance, coupled with the benefits of mobility and elimination of wiring and per-port costs, will enable 802.11n to change the enterprise networking landscape.

Compared with the peak performance metrics of legacy 802.11 a/b/g networks, 802.11n increases peak throughput by six times and range by three times, and it improves signal quality. It does so by doubling the spectrum per channel, improving baseband encoding, increasing the number of transmit/receive chains, leveraging multi-path, and enforcing the use of the more efficient 802.11e MAC protocol. Clearly, 802.11n is significantly more complex than earlier 802.11 protocols, spanning major enhancements in RF, baseband and MAC protocol. Consequently, there will be major variations in the benefits that can be realized from 802.11n, depending on device capabilities, device and access point settings, and the overall wireless LAN architecture in which 802.11n is deployed.

What are the downsides, if any, to 802.11n?
Ahlawat: There are no downsides, just considerations that enterprises have to keep in mind to avoid hidden costs of upgrading. As mentioned earlier, MIMO provides critical performance benefits to 802.11n. Because its signal reach is unpredictable, however, MIMO also makes it challenging for networking managers to design the network using traditional methods of site planning. Companies considering 802.11n should carefully evaluate vendor approaches to site planning. There are no tools available in the market for planning and placement of 802.11n APs. Meru's single-channel architecture requires planning for AP placement, but not channel planning. Converge holes can be easily filled by deploying additional access points on the same channel.

Another consideration is power. Access points draw power through Power over Ethernet (PoE). Meru … can support 802.11n [in] 2-by-2 antenna mode using the existing PoE standard of 802.3af (15.4 watts). Most vendors will require enterprises to upgrade their PoE ports on wired switches or PoE midspan devices to support 802.3at (29 watts), which has not yet become a standard.

What kind of compatibility issues are there in mixing 802.11n with existing Wi-Fi networks?
Ahlawat: 802.11n is backward compatible to all three previously ratified Wi-Fi standards – 802.11b, 802.11a and 802.11g. When selecting a vendor, enterprises need to ensure that they choose an architecture that takes into account the standard supported by the client devices to avoid slowing all the devices to the lowest common denominator.

For more on 802.11n Read what Cisco is doing with 802.11n Learn why 802.11n may require upgrades Before deploying 802.11n, do your research Take a look ahead at the 802.11n standard

With enhanced speed, capacity and other new capabilities, will 802.11n drive the adoption of voice over wireless or other advanced applications?
Ahlawat: With 802.11n, WLANs are finally achieving the speeds of wired networks. Our increasingly mobile workforce is the catalyst for much of the change we're seeing: More laptops are shipped now than desktops, cell phones are increasingly offering Wi-Fi adapters, and some vertical markets, such as healthcare and manufacturing, are seeing widespread adoption of Wi-Fi voice handsets instead of fixed desk phones.

In the next three to five years, networking will be transformed much more rapidly than it has been in the past 15 years. With IP becoming the preferred transport protocol and wireless becoming the preferred transport medium, we're seeing the creation of a new market that is transforming voice communication. Voice over WLAN (VoWLAN) is taking off because desk phones are not only expensive to install and maintain, they also force employees to work in a fixed position and thus hinder productivity.

With the new capacity provided by 802.11n, expect to see new high-performance data applications, voice communications and real-time video streaming business solutions.

Tags: WLAN Standards,  Wireless LAN Implementation,  VIEW ALL TAGS

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