There is no doubt that 802.11n brings a high level of performance when compared to older a/b/g WLANs. Using multi-antenna and multi-radio MIMO capability allows data to be transmitted over multiple data streams in the same 802.11 channel — doubling, tripling, and even quadrupling throughput. Higher throughput opens up a new world of applications over wireless, including voice and video; and smart phones are already available to gobble up the content.
But these performance enhancements run parallel to the complexities of 802.11n. While manufacturers and industry organizations strive for interoperability, 802.11n still requires an educated consumer, especially for enterprise deployments, to ensure that incompatibilities are not designed or introduced into existing WLAN infrastructures.
Below are common issues that you may face when switching to 11n, how you can easily solve these issues, and questions you should ask your network monitoring provider and network equipment manufacture before you make the switch.
Mixed Mode Deployments
If you are deploying 11n, and want to take full advantage of it, you need to have all 11n gear. That’s not to say 11n isn’t compatible with existing a/b/g technology, because it certainly is. But once users hear that 11n is deployed, they expect all the benefits, and if they’re still using older technology to connect into 11n APs they’ll wonder what all the hype is about. If there are operational or financial reasons for designing for mixed modes, be sure to set appropriate expectations for users, and be extra vigilant in testing and verifying the performance of both the a/b/g and 11n users to be sure the overall system is performing as designed.
Compatibility Within 11n Greenfield Deployments
Even if you’re going all 11n, you need to carefully analyze the specifications for all of your components, including APs and wireless clients, to ensure complete compatibility and ultimate performance.
The typical designation for the specific 11n capabilities of a device is: NxM:n, where N is the number of transmitting antennae, M is the number of receiving antennae and n is the maximum number of data streams the device is capable of using. Note that just because a device is “3×3” that does not automatically mean it is also capable of 3-stream operation (and the corresponding 450Mbps data rate). For 3-stream operation the specification should be 3×3:3. If the manufacturer does not include that detail (most don’t on their packaging) then pay careful attention to the maximum throughput the manufacturer advertises for the device. If it’s 150Mbps, it’s a 1-stream device. If it’s 300Mbps, it’s a 2-stream device. And if it’s 450Mbps, it’s a 3-stream device. To take full advantage of maximum data rates, both the AP and the client must be capable of the same number of data streams. If your AP is capable of 3 streams but you have some clients that only have 2-stream wireless adapters then those clients will only be able to connect at 300Mbps maximum.
The same holds true for network monitoring. If you have devices that are capable of 3-stream operation, you must use network analysis software with a 3-stream capable wireless adapter to capture any 3-stream data in the network.
Inability to Troubleshoot Due to Settings and Modes
11n uses a combination of technologies in addition to MIMO to achieve superior data rates. These include channel bonding (also known as 40MHz mode), aggregation, and short and long guard intervals. Now we have 4 variables that can be applied in many, many different combinations, making 11n analysis extremely complex. Users of network analysis software, like OmniPeek, often have difficulty capturing all of the 11n data when they first upgrade. It’s critical to understand the maximum capabilities of your APs, as they will negotiate the optimum combination of settings with each associated client. Once these maximum capabilities have been understood through an analysis of each AP’s configuration settings, you can properly determine the appropriate wireless adapter and settings to be used for wireless network analysis.
Whether you already have 11n in place or you are thinking about moving, make sure you educate yourself about its complexities and determine if the ROI is there. If your current 802.11a/b/g is not fully depreciated, it might not be the right time for you to switch.