Cisco Cisco Aironet 3500e Access Point 백서

Farpoint Group White Paper – April 2010 

 

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and localize illicit transmitters of any form on a firm’s premises is today an 
essential WLAN assurance capability. 

 

•  Policy enforcement – Firms should have policies with respect to what wireless 

devices (including cordless phones, wireless video cameras, non-Wi-Fi wireless 
LANs, and more) can be used on site. Being able to detect prohibited devices is 
vital to this end. 

 

•  Forensic troubleshooting – Getting to the root cause of disruptions (intermittent 

or not) to wireless operations quickly, efficiently, and at minimal cost is a key 
capability of spectral assurance. Ultimately, as overall productivity depends upon 
the LAN and network services, it thus depends upon optimal wireless services as 
well. 

 
As we noted above, spectral analysis in Wi-Fi applications has traditionally been 
implemented via an engineer or similar technical professional walking around with a 
notebook-based analyzer, looking for the source of radio interference or otherwise 
prohibited transmitters. While this approach can and does work, it’s far from optimal. 
The biggest issue is that this technique is usually applied only when a problem is 
suspected. By then, of course, the problem might be gone, or, if intermittent or bursty in 
nature, undetectable. And, by definition, the WAM strategy covers only a portion of a 
given infrastructure at any moment in time, and it is always labor-intensive, involving a 
trained, experienced engineer or RF-qualified technician, and often with long-distance 
travel and significant time-on-site required. If one desires to localize the source of an 
interferer, such is often difficult with only one sensor. And, finally, the WA technique is 
completely independent of WLAN management and other assurance tools, meaning that 
decisions resulting from spectral assurance exercises must be made manually – with 
additional complexity and indeterminism often inherent in the process. 
 
While we do in fact recommend that a PC-based spectral analysis tool be available (for 
ad-hoc analysis and pre-installation RF surveys, for example), incorporating SA 
functionality into the infrastructure of an enterprise-class WLAN installation introduces a 
broad range of benefits. These include, most importantly, integration with the 
management console and management system of the wireless LAN, thus merging all key 
functions onto a single screen with a corresponding improvement in both staff 
productivity and overall operations. Radio resource management can be similarly 
optimized, with channel assignment and transmit power logic now able to take advantage 
of another key variable, and with automation in the bargain. Reconfiguration, as required, 
is rapid and automatic. Event recording and trend analysis become simple and consistent. 
Locating an interferer or unauthorized device is automated, accurate, and rapid. And, 
most importantly, large areas – even multiple buildings, campuses, and widely-dispersed 
facilities can all be monitored and managed from a single location on a continual 
(24/7/365) basis. The idea is very similar to that applied to intrusion detection and 
prevention (IDS/IPS) services and other elements of a WLAN assurance solution, which 
also began with the walking-around model and evolved into enterprise-class, 
infrastructure-based solutions.