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Farpoint Group White Paper – April 2010
Spectral Assurance Total Cost of Ownership
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hile many forms of wireless-LAN assurance and verification tools have become
available over the past decade or so of the history of the WLAN and Wi-Fi, one
of the last to be addressed is the ability to examine activity at the physical layer
available over the past decade or so of the history of the WLAN and Wi-Fi, one
of the last to be addressed is the ability to examine activity at the physical layer
(PHY) – in other words, to look at what’s happening in the air itself, what we call
spectral assurance (SA). SA is particularly important not just because the frequencies
used by WLANs are unlicensed, and thus subject to arbitrary radio signals and
interference, but rather because WLANs are now mission-critical in so many applications,
serving as primary and even default access, and the need to detect and remediate
spectrum-related challenges has become equally vital. The device used to address this
challenge is called a spectrum analyzer, and, with the initial availability of Cisco’s
notebook-PC-based Spectrum Expert in 2005, a low-cost but highly-effective tool was
finally available to network operations staffs everywhere. But a new challenge has
emerged: as wireless LANs have grown in importance and coverage, the ad hoc approach
to spectrum analysis, what we call the “walking around” (“WAM”) model of operation
enabled by mobile spectrum analyzers, while still valuable, is less than optimal. Given
the mission-critical nature of contemporary WLAN installations, there is an obvious need
for full-time, pervasive spectral analysis, and thus a clear requirement to move this
functionality into the WLAN infrastructure, thus creating what we call the
“centralized/infrastructure” (“CIM”) model of spectral assurance. With recent
introduction of Cisco’s CleanAir product line, the CIM strategy is now a reality, leading
to some very interesting questions about the total cost of ownership of such an approach
– the subject of this White Paper.
Spectral Assurance: The Benefits
Why is spectral assurance so important? Let’s look at some of the key benefits:
spectral assurance (SA). SA is particularly important not just because the frequencies
used by WLANs are unlicensed, and thus subject to arbitrary radio signals and
interference, but rather because WLANs are now mission-critical in so many applications,
serving as primary and even default access, and the need to detect and remediate
spectrum-related challenges has become equally vital. The device used to address this
challenge is called a spectrum analyzer, and, with the initial availability of Cisco’s
notebook-PC-based Spectrum Expert in 2005, a low-cost but highly-effective tool was
finally available to network operations staffs everywhere. But a new challenge has
emerged: as wireless LANs have grown in importance and coverage, the ad hoc approach
to spectrum analysis, what we call the “walking around” (“WAM”) model of operation
enabled by mobile spectrum analyzers, while still valuable, is less than optimal. Given
the mission-critical nature of contemporary WLAN installations, there is an obvious need
for full-time, pervasive spectral analysis, and thus a clear requirement to move this
functionality into the WLAN infrastructure, thus creating what we call the
“centralized/infrastructure” (“CIM”) model of spectral assurance. With recent
introduction of Cisco’s CleanAir product line, the CIM strategy is now a reality, leading
to some very interesting questions about the total cost of ownership of such an approach
– the subject of this White Paper.
Spectral Assurance: The Benefits
Why is spectral assurance so important? Let’s look at some of the key benefits:
• Interference detection – The unlicensed bands can be filled with interfering
signals from a broad range of devices, from cordless phones to Bluetooth products,
wireless video cameras, microwave ovens, and more. Most interference is
unintentional, weak, and harmful to Wi-Fi signals only intermittently. But, as our
own experiments have shown, interference from common, commercial wireless
devices can be very damaging to Wi-Fi transmissions, and, without spectral
analysis, there is no way to verify the nature of a specific problem.
wireless video cameras, microwave ovens, and more. Most interference is
unintentional, weak, and harmful to Wi-Fi signals only intermittently. But, as our
own experiments have shown, interference from common, commercial wireless
devices can be very damaging to Wi-Fi transmissions, and, without spectral
analysis, there is no way to verify the nature of a specific problem.
• Optimal operations – While most enterprise-class WLAN systems can today
automatically assign radio channels and set transmit power levels, having
knowledge of the radio environment can avoid channels with significant
interference (Wi-Fi or other), thereby optimizing (potentially dynamically) a
given installation for throughput, reliability, and overall capacity.
knowledge of the radio environment can avoid channels with significant
interference (Wi-Fi or other), thereby optimizing (potentially dynamically) a
given installation for throughput, reliability, and overall capacity.
• Security and system integrity – While full-blown PHY-layer denial-of-service
(DoS) attacks are thankfully rare, such remain a possibility. Being able to detect
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