AVIAT’S FAS EXPERT SYSTEM USES SOPHISTICATED, PATENT-PENDING
ALGORITHMS TO ENSURE LINK STABILITY

INTRODUCTION
For more than two years now, the FCC has been evaluating the necessity and feasibility of opening up the 6 GHz band to unlicensed users of a wide variety of devices. They’ve published multiple notices of their findings, and on April 2, 2020, FCC Chairman Ajit Pai issued a draft version of the official rules, allowing unlicensed operation in the 6 GHz band—over the entire 1,200 MHz spectrum of that band. A final vote on April 23 opened the door to Wi-Fi 6e.


Other stakeholders have filed objections to the FCC plan, asking for greater research and planning, more development of interference monitoring and protection schemes, and assurance that their links will stay stable. Incumbents operating mobile networks remain concerned that their microwave links will be susceptible to significant interference. Those objections come mainly from utilities and public safety network operators, but also from mobile operators.


As early as March 2019, the Utilities Technology Council (UTC)
registered objections. They and other utility and infrastructure
associations filed a joint reply then to the FCC plan, stating that
advocates of unlicensed operation had not shown firm proof
that incumbents would be free from risk of interference. They
saw the arguments for unlicensed 6 GHz as generic policy
statements.


In public statements, the Association of Public-Safety
Communications Officials (APCO) also voiced objections. They
noted that interference would require lengthy troubleshooting
and could mean significant downtime before link operation
was restored. “This would be unacceptable for mission-critical
uses such as public-safety dispatch or first responder voice
communications,” a spokesperson said. APCO also indicated
that a study by RKF Engineering Services, which supported the
adoption of unlicensed operation, contained wrong assumptions
and technical errors, and did not address key potential
problems.

PROBLEM: THE REAL RISKS TO INCUMBENTS
So why are the new rules shaping up to be a major problem for
licensed stakeholders?

Here are the main reasons:
• Wi-Fi 6e is now assured as a new consumer boost, providing enhanced speed and performance.
Its certification process started in September 2019, so you can bet that new devices supporting it
are being developed now.
• Interference can directly cause outages and/or reduce the fade margin, so links are more
susceptible to what would otherwise be minor issues.
• Interference is a problem in 5.8 GHz environments today. There is no reason to believe Wi-Fi 6e,
with so many devices—and untested or hastily tested protections—will not follow suit. Plus, there
are many more 6 GHz point-to-point (PtP) links than 5.8 GHz. And there will likely be many more
Wi-Fi 6e outdoor access points, compared to 5.8 GHz environments.
• AFC protection mechanisms may not work well. The Universal Licensing System (ULS) data that
operators use to file their applications (which includes maps showing the geographic area covered)
can be based on inaccurate information and is often not correct.
• It’s difficult logistically and technically to regulate and control Wi-Fi 6e deployments. Also, many of
the assumptions being made on the impact of interference to PtP links are aggressively optimistic.
• PtP systems were designed to assume interference does not exist. That’s especially true for Wi-Fi
interference. So today’s systems lack effective controls and protections.
• The vast majority of 6 GHz links are used by utilities, public safety networks, and mobile operators.
Interference monitoring is not available in those mission critical applications today.
FOR ALL THESE REASONS, INCUMBENT STAKEHOLDERS DO NOT SEE THE
AFC MECHANISMS WORKING AS PLANNED.

BROAD SOLUTION CHALLENGES
The main challenge today for solution providers and network
operators is that there is no way to detect interference. This puts
the operator in reactive mode, where significant problems must
be detected before action is taken. The responses might be nonanalytical, even guesswork at times: How do you identify interference
that has not yet caused an alarm, but may be impacting radio
performance? How do you pinpoint and analyze interference issues
before they cause an outage or other major problem?
In addition, current systems do not gather data—real-time or historical—for reporting or for fast remediation. Solution providers and operators need to know a great deal: What are the current interference levels today? What impact will Wi-Fi 6e interference have on those levels, both initially
and over time? What links do operators need to worry about? How can they identify interferers and remediate issues with the FCC?
With no answers to those questions, operators will remain reactive and link degradations and outages will occur in critical service environments. With no answers, operators will be unable to fight back.

SOLUTION: AVIAT’S FAS EXPERT SYSTEM
Aviat’s FAS (Frequency Assurance Software) offers
sophisticated, well tested monitoring and analysis of
unlicensed 6 GHz—and can trigger corrective action
to protect link stability. This software is a direct
response to the FCC rules opening up the 6 GHz band
to unlicensed users. It’s a comprehensive solution
designed to protect customers from pending radio
local area network (RLAN) deployments in the 6 GHz
band.


The main focus here will be on the North American
case, where the FCC’s directive has created a more
urgent need for intervention. We’ll follow with some
perspectives on the international situation, where
some of these concerns will also be felt.

KEY FACTS OF AVIAT FAS:
• The software functions as an add-on to Aviat’s
ProVision Plus network management software.
• The new FAS software is ground breaking and
patent-pending.


KEY FEATURES OF AVIAT FAS:
• Interference alarms and analysis
• Interference trends by link and network
• Detailed and executive reports
• Paperless chart recording (PCR) integrated into the
FAS application to enable ongoing analysis


TOP BENEFITS OF AVIAT FAS:
• Outage prevention before it happens
• Detects issues before they become real problems
• Prevents outages and performance degradation
• Reporting and remediation
• Collects and reports on interference events, finds
interferers, and identifies trends for remediation
with regulators
• Baselines your network to understand the base
case
• Data accumulation offers ongoing fine tuning and
protections
• Isolates problem links
• Enhanced network management
• Manage your network anywhere, anytime
• With FAS you also get web-based management (for
layer 1) and a management platform for the future
(the all new Aviat apps build on ProVision Plus)
These features and benefits highlight
the urgency of the problem. For
maximum benefit, network operators
will do well to stay ahead of the curve
and deploy now, before unlicensed
devices proliferate. FAS can benefit
anyone concerned with reliability on 6
GHz links.

FAS IS NOT JUST FOR 6 GHZ – APPLICABLE FOR ANY BAND
Interference in other bands can also be a problem not just in North
America but in other regions as well. Network operators around the
world often contend with these issues:


• Poorly regulated microwave spectrum in some countries
• Random, unprofessional users operating in microwave bands without licenses
• Microwave spectrum costs can be high in some countries—and interference wreaks havoc on your very expensive asset
• Many of today’s systems around the world lack controls and protections
• 80 GHz millimeter wave spectrum is often lightly licensed and operators using this band have no visibility into the state of interference
6 GHz is not the only band or application being affected by interference. FAS monitoring software has been designed to work in any band, in any region of the world, from 6 GHz to 80 GHz. And it works on
any Aviat radio, including the IRU 600, ODU 600, WTM 4000, and WTM 4800—with or without Eclipse or CTR 8000.
Beyond 6 GHz, interference monitoring is important in countries with lax regulatory enforcement; wherever non-professional operators use spectrum in unauthorized ways; in lightly licensed environments such as 80 GHz; and in regions where spectrum is expensive and operators need assurance that their costly spectrum asset is being protected

FAS PATENT PENDING ALGORITHM—THE CORE ENABLING
ELEMENTS OF FAS SOFTWARE


At the core of the FAS software lies a set of algorithms that can be used to detect interferer signals in PtP microwave links. They are designed to operate while a microwave link is on-line, without affecting the ongoing payload transport. Determining whether a PtP microwave link is being affected by interference is extremely important, as interference may affect performance and the stability of the link. It’s important to differentiate between situations where the radio signal is being degraded by one
or more interferer signals and those that may be produced by naturally occurring phenomena, equipment malfunction, ineffective installation practices, or other reasons. The algorithms make use of parameters present in the radio modem as well as in the radio frequency unit (RFU) to determine whether an interferer is or may be present in the path. They can also determine the severity of the interference and discriminate among the different interference types. Based on these detection algorithms, microwave links will be able to react to the interference by increasing output power, shifting to a more robust modulation, using a diversity partner signal (if available),improving the quality of the signal by adjusting equalizer coefficients, or other remediations.

CONCLUSION
The FCC, in its effort to advance consumer technology and the
benefits to service providers and consumers, has been optimistic
that interference from new Wi-Fi 6e and other devices will not be
significant. Decades of accumulated knowledge and experience
among incumbents—of both network operators and solution
providers—say that this optimism is unfounded.
Untested or hastily tested rules and AFC protection mechanisms,
and the mission critical applications used by utilities, public safety
networks, and mobile operators over 6 GHz links all point to one
conclusion: the risk is significant.

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