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    • December 14, 2012

    How 2 Microwave Networks Survived Superstorm Sandy

    After Superstorm Sandy more than 8 million people were without power on the East Coast of the US and Canada, including most of New York City.

    After Superstorm Sandy more than 8 million people were without power on the East Coast of the US and Canada, including most of New York City.

    The week of October 29, 2012, “Superstorm” Sandy made landfall in the Northeast United States. Combining a powerful hurricane with a fast-moving cold front resulted in one of the worst weather systems possible. Sandy also took shape during the full moon and high tide. The storm brought damage and destruction from the Carolinas all the way to Canada before it moved on. There was tremendous loss of power, communications and general destruction of infrastructure. Sadly, there were also a number of deaths from this powerful storm.

    So what does that have to do with Aviat Networks? One of the AviatCare support services that we offer customers is a comprehensive Network Monitoring and Support service from our North American Network Operations Center (NOC) located in Texas. From that location, we have the ability to monitor, manage and dispatch resources to address customer issues with their networks. Even before the storm hit the Northeast U.S., our NOC was getting ready to ensure our customers would be prepared for this coming disturbance. With our ability to monitor weather events in real-time, we can see immediately what is affecting a customer’s network from a weather perspective.

    In the path of the storm, we had two customers who rely on Aviat Networks for the monitoring and management of their networks from our NOC: an E911 Service in Virginia and a low latency network that runs from Chicago to New York City. First hit was the Virginia E911 customer’s network undergoing a glancing blow from the storm but no less destructive than what was soon to happen farther north. Three of the E911 sites were brought down by Sandy. Within eight hours of the storm touching Virginia, the NOC with support from our Technical Assistance Center (TAC) engineers had the customer back up and operational. We were able to do this 100 percent remotely without having to dispatch any field resources to site. Using the tools we have, we were able to remotely validate that there was no physical damage and all that had to be done was get power back up and reset the equipment remotely.

    The Chicago-to-NYC network had bigger issues. The eastern end of this network bore the full brunt of the storm and suffered considerably. Three sites endured long-term power loss and two sites were blown out of path alignment. Even though it was outside of the scope of the carrier’s SLA, we located power generators and got them onsite in time to provide power before battery backup failed. This work started even while the storm was underway in the area. Resources got to the sites through severe flooding, virtually impassable roads and downed trees and power lines. In addition, someone returned to the sites every 12 hours to refuel the generators for three days running until power was finally restored. As soon as the storm passed, we collaborated with tower crews on site to realign the links back to operational status. Within 48 hours of the superstorm, the low-latency network was fully functional and carrying traffic within the parameters required to meet its customers’ requirements.

    This was truly a team effort and involved the dedication of a large number of AviatCare resources as well as some of our key partners. This is just another example of how we can pull together to ensure our customers get a level of care that demonstrates our commitment to excellence. Whether it is a superstorm or a super number of tornadoes—which we had to address in 2011—our NOC and TAC teams know what it takes to support customers during and after a natural disaster. We never wish for these things to happen but it is critical that when they do our customers have the right level of support to ensure their networks are operational in the shortest time possible.

    Patrick Davis
    Director, Global Support Services
    Aviat Networks

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    • November 16, 2012

    All-Outdoor Microwave Radios: Site Considerations

    All-Outdoor Microwave Radios: Site ConsiderationsOne of the great things about the microwave radio market today is the diversity of products available to network operators. But like many situations where there is a glut of options, it tends to put more stress on making the right choice.

    An operator looking at products in the microwave radio sector will notice that there are three general categories of product to choose from: all-indoor, split-mount and all-outdoor, and within each, they are myriad different flavors.

    All-outdoor radios are the most recent addition to the microwave radio party, and for the sake of easy reference, I’ll refer to them as ODRs (outdoor radios). These self-contained systems incorporate the traffic interfaces, switching/multiplexing elements, radio modem and radio transceiver—all packaged in a weatherproof outdoor housing. By contrast, an outdoor unit (ODU) used in split-mount systems only contains the radio transceiver, which connects to a radio modem embedded in an indoor unit (IDU). In a split-mount radio system, the IDU also provides the traffic interfaces and switching/multiplexing elements.

    The rationale for ODRs is straightforward—networks are getting denser, new sites are getting smaller and established sites more densely populated. Space for equipment such as IDUs is at a premium and costs of upgrading sites with bigger equipment shelters is often not viable or possible due to site constraints. As a result, more network devices are being repackaged for deployment outdoors on supporting structures such as towers, walls or masts. Advances in electronics have made microwave radios viable for all-outdoor treatment, so ODRs came into being.

    They did so to a fanfare of claims that pointed to fantastic gains in terms of operator TCO (total cost of ownership). No doubt, an ODR can deliver cost benefits, but it is important to fully scope and quantify those benefits, because although ODRs represent simplification in terms of product architecture, most networks have remained stubbornly complex. In practical terms, this means for each type of site in the network an operator needs to closely examine the gains an ODR might generate vs. a split-mount radio, for example. Our experience is that ODRs provide the most operator benefits at sites where:

    • One gigabit Ethernet (GbE) interface is adequate
    • Only a single local device will be connected (such as an LTE basestation)
    • There are no requirements to aggregate traffic from “downstream” sites
    • Out-of-band management facilities are not required
    • Non-protected (1+0) link configuration is adequate

    Once operators consider sites with requirements beyond this scope—usually the majority—then ODRs (somewhat ironically) start to generate complexity and cost. This becomes manifest in the form of multiple Ethernet cable runs, multiple power cable runs, multiple PoE injectors, multiple lightning protection devices and, in some cases, the need for a separate outdoor Ethernet switch.

    Even at modestly complex sites, the overhead costs ODRs can generate mean that a split-mount radio will often be a more effective option and deliver better TCO, assuming space can be found. On that note it is worth highlighting that IDUs already deployed at such sites are often modular and can be scaled without consuming any additional rack space, and the most advanced fixed (i.e., non-modular) IDUs only consume a half-rack unit of space.

    On the surface, the case for ODRs can seem compelling but before jumping in, I would encourage operators to carefully examine how marketing claims translate into meaningful (real) TCO gains.

    I am convinced ODRs represent a new and potentially very useful product category for microwave radio, but they are not a panacea; our experience (at Aviat Networks) is that optimum TCO is based on a mix of split-mount and all-outdoor radios (i.e., one “size” does not fit all).

    So there you have it, in the right environment, an ODR can offer a winning formula but in other situations, it may not work so well. An old saying comes to mind: Knowledge is knowing a tomato is a fruit, but wisdom is knowing not to put a tomato in a fruit salad.

    Next time, we will examine ODRs in more detail, how they differ and how to choose the best option for your network.

    Jarlath Lally
    Product Marketing Manager
    Aviat Networks

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    • November 9, 2012

    Know Your Microwave Backhaul Options

    Know Your Microwave Backhaul OptionsIf you look in the November issue of MissionCritical Communications, you will see an article by Aviat Networks director of marketing and communications, Gary Croke. In his article “Know Your Microwave Backhaul Options,” Gary covers:

    • Benefits of using indoor, outdoor and split-mount microwave radios in various scenarios
    • Rationale for choosing microwave over fiber (especially for LTE)
    • Deployability of microwave
    • Software-upgradeable capacity for “pay-as-you-grow” capex scalability
    • Cost contribution of towers over the first 10 years of LTE implementation
    • And more

    You can read Gary’s article (on page-30) here—MissionCritical Communications—November 2012.

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    • October 5, 2012

    Developments in Fixed Link Spectrum Access in Ireland

    spectrum

    Spectrum (Photo credit: Free Press Pics)

    In response to the ever-growing demand for spectrum to satisfy the increase in usage of data hungry mobile applications and in line with recently published ECC recommendations, ComReg (i.e., Ireland’s telecom regulator) issued a consultation document looking at the future demands on spectrum for point-to-point fixed links. September saw the publication of the conclusions and subsequent decisions arising from that consultation, to which Aviat Networks was the only manufacturer to respond. This blog highlights some of those decisions:

    New Spectrum
    One of the major topics was the requirement for more spectrum allocated for point-to-point usage. Consequently, ComReg has made the following announcements:

    • ComReg intends to open the frequency bands below, as there is a significant demand for fixed links services in the 28 GHz, 31 GHz and 40 GHz band:ComReg microwave spectrum rules change September 2012
    • The 32 GHz band may be made available for fixed links services at a later stage subject to its potential for future PP/PMP use and the demand on spectrum for PP use in the 31 GHz (31.0 – 31.3 GHz paired with 31.5 – 31.8 GHz) band
    • Within the 28 GHz band, as per REC T/R 13-02 Annex C, the following frequency ranges will be made available for fixed links services: 27.9405 – 28.4445 GHz and 28.9485 – 29.4525 GHz
    • Frequency bands 28 (27.5 – 29.5) GHz, 31 (31.0 – 31.3 paired with 31.5 – 31.8) GHz, 32 (31.8 – 33.4) GHz and 40 (40.5 – 43.5) GHz will not be opened for PMP use in the current spectrum strategy period 2011 – 2013

    Aviat Networks supported this initiative during the consultation process and is pleased to see ComReg make these announcements as a move to satisfy the increasing demand for microwave spectrum. Specifically, frequencies in the range of 28 to 42 GHz are ideal for short-haul urban links, and we expect the decision by ComReg to stimulate further growth of microwave for fixed line and mobile network applications.

    Technical Changes

    • High-Low search radii for the 23 GHz and 26 GHz bands will be reduced from 200 meters to 100 meters. The consensus of current licensees operating within the 23 GHz and 26 GHz bands is that the reduced radius will improve spectrum planning and reuse, which will improve spectral efficiency
    • There will be no distinction between rural and urban areas concerning the High-Low search radius
    • Antenna size will be limited to 0.6 meters in the 23 GHz and 26 GHz bands
    • ComReg will allow use of 56 MHz channels in the 26 GHz band only where the licensee has a National Block license containing contiguous blocks of spectrum
    • ComReg will permit the use of higher bandwidths, as shown in the table below, to facilitate the increase in mobile data demand:ComReg microwave spectrum rules changes September 2012

    Block Licensing
    ComReg signalled its intention to potentially reopen the 26 GHz block license scheme for a further round of National Block assignments, subject to market demand. In the past, Aviat Networks commented that it believes block licensing is not the most appropriate method of licensing in the microwave bands. However, ComReg disagrees with that view.

    Summary
    The combined expansion in spectrum use—new bands and larger channel allocations—underlines the popularity and ongoing viability of microwave as an alternative to fiber in urban networks experiencing rapid traffic growth and geographic expansion.

    Aviat Networks welcomes the ComReg announcement. We already address all the band/channel assignments made by ComReg.

    Ian Marshall
    Regulatory Manager
    Aviat Networks

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    • September 18, 2012

    3 Types of Microwave Propagation and the Horn Antenna

    Antennas on the roof of a microwave relay stat...

    Horn antennas on the roof of a microwave relay station near Madison St. and 17th Ave, Capitol Hill, Seattle, Washington State, USA. (Photo credit: Vladimir Menkov via Wikipedia)

    Between any two microwave radio antennas, there is one direct ray and multiple refractive/ reflective multi-path rays. In the eighth and last installment of our Radio Head Technology Series, Aviat Networks Principal Engineer and master storyteller, Dick Laine, relates how restrictive tower rules for San Francisco’s historic China Basin Building required fine adjustments of a horn antenna to resolve reflective rays from the surrounding bay.

    As Dick tells it, to accommodate a Space Diversity arrangement, one horn antenna on the building had to be hung upside down. During the installation process, the alignment for the upside-down diversity antenna created a reflection point 3 miles out into the bay. Because of this installation, the performance was horrible, but at the time no one knew why. For example, when a little speedboat or anything larger went through the reflection point, there would be an outage as the signal was interrupted. There did not seem to be an obvious fix to the alignment issue. The horn antenna did not have a way to check the alignment on the horizontal with a bubble level.

    To find out how Dick solved this antenna mystery, register for the Radio Head series (it’s free). Then to put it all in context, Dick goes over Huygens’ Principle as it applies to microwave signal diffraction. And if you ever wondered what happened to periscope antennas, Dick provides some key insight! Tune in to find out!

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    • August 17, 2012

    Wireless Regulators Move to Prevent Spectrum Waste

    Historically, in many countries the 26GHz and 28GHz wireless frequency bands have been allocated to point-to-multi-point systems, such as LMDS in the United States and LMCS in Canada. However, most of these systems have failed to reach their expected potential in terms of revenue generated and, as such, much of the allocated spectrum is now unused. This, along with the growth in demand for point-to-point microwave spectrum, has meant a number of national regulators have started to consider reallocation of this spectrum.

    In Canada, the spectrum allocations for both the 26GHz and 28GHz bands have been revisited, owing to their underutilization by LMCS operators, with a new band plan having been developed during the drafting of SRSP 325.25. The diagrams below show the new allocations that accommodate more FDD spectrum suitable for microwave in point-to-point usage.

    Figure 1 - 25.25 - 26.5 GHz Band Plan and Associated Usage - Industry Canada

    Figure 1 – 25.25 – 26.5 GHz Band Plan and Associated Usage – Industry Canada

    While the technical details of this draft SRSP have been finalized, consideration of licensing options by Industry Canada has so far delayed the formal publication of this SRSP. Note that the remaining point-to-multipoint operators are catered to in the TDD section in the middle of the 26GHz plan.

    Figure 2 - 27.5-28.35 GHz Band Plan and Associated Usage - Industry Canada

    Figure 2 – 27.5-28.35 GHz Band Plan and Associated Usage – Industry Canada

    In the Republic of Ireland, ComReg (the Irish national telecommunications regulator) recently issued a consultation resulting from an operator request to change the use of its allocated spectrum from point-to-multipoint to point-to-point. Figure 3 shows the current situation in Ireland and Figure 4 shows the same band after the proposed change of use.

    Figure 3 - Current 26GHz Band Plan - ComReg Ireland

    Figure 3 – Current 26GHz Band Plan – ComReg Ireland

    In the United States, the LMDS service occupies the following spectrum blocks:

    • 27.5 – 28.35 GHz
    • 29.1 – 29.25 GHz
    • 31.075 – 31.225 GHz
    • 31.0 – 31.075 GHz
    • 31.225 – 31.3 GHz

    Thus, that would make a total of 1300MHz of spectrum—more than double the recent allocation at 7 and 13GHz—potentially available across the entire country. LMDS take up has been very low, and, as previously mentioned, much of this spectrum is now unused. This begs the question: Would spectrum reallocation in the U.S., as is happening in Canada and Ireland, promote its more active usage?

    Figure 4 - Revised New 26GHz band plan - ComReg Ireland

    Figure 4 – Revised New 26GHz band plan – ComReg Ireland

    It is worth noting that existing users are protected in both the examples given above, but unused spectrum is now available to point-to-point operators. Therefore, it is now time to approach the FCC and request a similar exercise to be carried out for the United States. Aviat Networks intends to be one of the driving forces in requesting this reallocation of spectrum.

    Ian Marshall
    Regulatory Manager
    Aviat Networks

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    • June 26, 2012

    42GHz: A New Global Standard for Wireless Backhaul?

    Parabolic antennas

    With ever-increasing demand for spectrum in fixed services, FWCC has endorsed opening up the 42GHz band as a new global standard for microwave backhaul. (Photo credit: Miguel Ferrando via Wikipedia)

    An ever-increasing demand for spectrum has recently turned focus on the 42GHz band. Initially opened in some European countries following the development of ECC REC(01)04, the recently published ECC Report 173 states 12 countries have opened this band including Germany, Norway, Poland, Switzerland and the United Kingdom. In the U.K., this band was part of a wider auction of fixed service bands in 2010, with three operators being granted blocks of spectrum in the 42GHz band as a result.

    Building on this growth there is a move to make this band global and earlier this year saw the publication of ITU-R Rec F.2005, which in effect promoted the aforementioned CEPT recommendation to global status. Aviat Networks has been lobbying key regulators to open this band. We are eagerly awaiting a consultation from Canada and responses have already been submitted to recent consultations from France and Ireland containing considerations regarding opening this band. The process is also underway in Finland and Sweden to open up this band. Recently our attention has turned to the United States and whether the FCC will open this band for use by the fixed service.

    Back in autumn 2011, Aviat Networks raised this topic within the FWCC (Fixed Wireless Communications Coalition) as the first stage of a petition of rulemaking to the FCC. At first there was only a lukewarm reception to our idea as there was concern that the FCC would refuse the request out-of-hand as some previously released spectrum below 40 GHz is underutilized and, therefore, why is more needed? We pointed out that much of this spectrum (e.g., 39 GHz) was block-allocated by auction and thus has not been readily available to all users and that the licensees have underutilized the spectrum. There is a growing need for spectrum that can be licensed on a flexible, site-by-site basis, and this is reflected by the fact that there are no underutilization issues in bands such as 18 and 23 GHz, which are licensed in this manner. It is no coincidence that auctioned bands tend to underperform in terms of efficiency and utilization. So, undeterred, we forged ahead and this resulted in the production of a FWCC petition to the FCC in May 2012. The FCC has recently placed this petition on public notice, per its procedures. This is a great success for Aviat Networks and our commitment to seeking more spectrum for the fixed service, but the story has not ended here as can be seen from a recent blog entry from the FWCC.

    Aviat Networks will continue work with the FWCC to ensure that the FCC gives this proposal full consideration and, having learned important lessons from past spectrum allocations, we will lobby for a flexible approach to the licensing model.

    Ian Marshall
    Regulatory Manager
    Aviat Networks

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    • June 20, 2012

    What is More Susceptible to Rain Outage, Vertical or Horizontal Radio Signals?

    English: A map of the world divided into Inter...

    The world is divided into separate International Telecommunication Union regions. In many regions of the world, ITU methods of calculating rain outage are most commonly used. In other regions, such as North America, the Crane model is used more often. (Image credit: Wikipedia)

    Ever wonder which antenna polarization is more susceptible to rain outage? Vertical? Horizontal? Which should you use for very long hops?

    What would you do besides add extra fade margin to mitigate rain outage? Design a shorter path or use a lower frequency band?

    Aviat Networks’ microwave radio guru, Principal Engineer Dick Laine, tackles these tricky questions and others in the latest episode of our Radio Head Technology Series of videos.

    Dick also talks about rain outage—as calculated by ITU using a simple scientific calculator, or computer programs (Starlink) that use the Crane model. He goes through an ITU-R availability calculation in one example, noting specifically about rain attenuation calculation above and below 30 degrees latitude. Dick then proceeds into a deep dive on calculating outage when you know the fade margin, followed by a discussion on the Crane rain attenuation model.

    Aviat Networks invites our readers to register to be added to our Radio Heads distribution list to get notified of new Radio Head Technology Series releases and links to replays.

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    • June 15, 2012

    Mobile Network Modernization in Africa

    Africa Mobile Penetration Rates

    Total African Mobile Connections and Penetration Rate (million, percentage penetration). Source GSMA Africa Mobile Observatory 2011

    Throughout Africa a wind of change is blowing as mobile network operators ponder, and in many cases implement, a wave of network modernization. The trigger for this is multi-faceted. Booming subscriber growth, introduction of new data services and arrival of new undersea fiber optic cable links are combining to strain existing network infrastructure to the breaking point.

    Booming Mobile Subscriber Growth
    According to the GSMA , as of September 2011 Africa has overtaken Latin America with 620m mobile connections, making it the second largest mobile market in the world after Asia-Pacific. The number of connections has more than doubled over the past four years, with growth expected to continue at the fastest rate of all global regions over the next four years.

    First Voice, Now Increasingly Data
    Most networks across Africa were built many years ago to serve the initial rollout of 2G/GSM mobile networks that were designed to provide basic voice services. Many operators have since introduced data services using EDGE, 3G WCDMA, and, more recently 3G HSPA, putting an incredible strain on these networks. These data services can be vital for the operator, as they are often supporting premium, prepaid subscribers or new fixed line data services being offered for small and medium-size businesses.

    One example of network modernization in action is in East Africa, where a mobile network operator saw subscriber numbers increase 9 percent in 2011, with 3G customers increasing more than 85 percent. This operator was also offering fixed data services to private and corporate customers through the deployment of WiMAX base stations collocated with the existing mobile sites. All this new data traffic was growing exponentially and fast outstripping the legacy backhaul network capacity. The operator also had to ensure that existing voice traffic was protected.

    Priorities Driving Network Upgrades
    Today, several priorities are driving network operators to upgrade their networks including the need for:

    • Increased capacity
    • More efficient use of backhaul spectrum resources
    • Support for increasing volume of Ethernet/IP-based traffic
    • Network Simplification
    • Reduction in Capital and Operational Expenses

    These five priorities are closely interrelated. For more details, download the complete article.

    Stuart D. Little
    Director Corporate Marketing
    Aviat Networks

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    • June 12, 2012

    Record 180 km Hybrid Diversity IP Microwave Link

    Survey view from Belize toward Honduras, at 1000 m AMSL

    Survey view from Belize toward Honduras, at 1000 m AMSL

    Link between Honduras and Belize Crosses Water and Land

    Last year I wrote about the world’s longest all-IP microwave link, stretching 193 km over the Atlantic Ocean in Honduras. Aviat Networks and Telecomunicaciones y Sistemas S.A. (TELSSA) designed and implemented this link together. This year, Aviat Networks and TELSSA again worked together to build another link and achieve another record—an Eclipse microwave link between Honduras and Belize that crosses 75 km of the Atlantic Ocean and 105 km of rugged terrain for a total path length of 180 km. This is a new world record for a hybrid diversity microwave link!

    After the success of implementing the 193km link over water, Aviat Networks and TELSSA were eager to meet the challenge to connect Honduras and the neighboring nation of Belize using a single microwave link. Aviat Networks network engineers and TELSSA engineers were able to use their extensive knowledge of local propagation conditions, thorough understanding of long path design principles and precise installation practices to successfully implement this 180km microwave link.

    Long Path Design Considerations

    As outlined in the article last year for the longest all-IP hop, a deep understanding of path design considerations and experience in microwave transmission path design are necessary to successfully complete a long path design. Key considerations involved:

    • The effect of antenna diameter on highly refractive paths
    • Precise alignment of the antennas to mitigate the effect of refractivity
    • Optimum RF and space diversity spacing to counter elevated divergent dielectric layers
    • Deterministic prediction of the variations of atmospheric conditions
    • Multi-path propagation delay

    To read more about this world-record Hybrid Diversity IP microwave link, download the full article.

    Ivan Zambrano
    Senior Network Engineer
    Aviat Networks

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    • May 29, 2012

    The Modulation Arms Race: A Case of Diminishing Returns

    English: A standard Quadrature Amplitude Modul...

    A standard Quadrature Amplitude Modulation constellation (non-gray code) diagram showing a demonstrative 4-bit binary code pattern. (Phase offset and amplitude values may not represent those used in real life) (Photo credit: Chris Watts via Wikipedia)

    There’s a new arms race in the microwave industry, and it’s over who can claim support for the highest QAM level. Now two vendors are out in the market fighting it out over who had 2048QAM first, yet go back a little more than 12 months and 512 or 1024QAM had barely hit the market. We even are seeing mentions of 4096QAM in some conference presentations. We here at Aviat Networks view these advances as a good thing for our industry, but this heavy marketing of 2048QAM does no one any favors, as it focuses purely on only one aspect of high modulations—capacity—and ignores several other aspects that need to be understood, namely:

    • Capacity improvement diminishes with every higher modulation step
    • High modulations come with much lower radio system performance—requires shorter hops and/or larger antennas
    • High modulations are much more sensitive to interference—makes link coordination difficult (if not impossible)
    • High modulations need higher Tx power, increased phase noise and linearity—increases radio design complexity cost

    So as with most things that are presented as a cureall, higher order modulations are a useful tool to help operators address their growing backhaul capacity needs, but the catch is in the fine print. Operators will need to look at all the tools at their disposal, of which 1024/2048QAM is a useful option, albeit one that will require very careful planning and strategic deployment. In general, operators need practical solutions for capacity increases, as detailed in “Improving Microwave Capacity“.  In fact, speaking of practicalities, the real challenges with LTE backhaul has very little to do with capacity…as detailed by this article. For the complete “Modulations Arms Race” article, click here.

    Stuart Little
    Director, Corporate Marketing
    Aviat Networks

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    • May 25, 2012

    Five-Nines Availability and RCA’s Top Secret Communication Project

    You may not think that 78 rpm records and microwave communications could have anything in common. But our Dick Laine finds the devil in the details between the two in Radio Heads video No. 3. (Picture: label for 1940s brand of jukebox needles for playing 78 rpm records; photo credit, Infrogmation via Wikipedia)

    Five-nines (99.999 percent) availability is a concept that is familiar in wireless engineering. Dick Laine, principal engineer of Aviat Networks, compares five-nines availability to 78-rpm records in our most recent episode of the Radio Head Technology Series.

    As he relates, even with scratches and pops, a 78-rpm record still is able to transfer aural information so that you can hear it, i.e., its availability is intact, as it does not drop performance. Scratches and pops only represent degradation in the quality of communication. But when the record is broken, an outage occurs—no record, no communication.

    The same goes for wireless communication systems. If a microwave link drops 315 or fewer seconds of microwave communications per year (in increments of up to 10 seconds at a time), it is maintaining five-nines availability. The microwave link is offering 99.999 percent availability for wireless backhaul. Only if the microwave link is unavailable for more than 10 seconds has an outage occurred, for the purposes of determining if microwave communications traffic has been dropped.

    Dick goes on to explain about what happened in 1949 when 78-rpm records were superseded by 45-rpm records. Dick got a sneak peek at the top-secret 45-rpm record project when he visited the legendary RCA facility in Camden, New Jersey, which played a crucial role in the development of the modern music, radio and television businesses. Unfortunately, unlike a five-nines microwave link, 78-rpm and 45-rpm records are mostly unavailable nowadays.

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